Air Mass Flow Rate Measurement

Final Report

l Design of a Laboratory Setup to Measure Air Mass lilow Rate

Design Team Kian Cheong Lim, Arianne Nartyasari Michael Tavares, Yiyan Wang

Design Advisor Prof. Mohammad Taslim E.

Abstract

In the field of engineering studies, experimental lab activities are necessary for engineering students to

relate what they have learned in dass as ideal situations to the actual application settings and conditions.

This project presents a design of an experimental lab setup for undergraduate mechanical engineering students to perform mass flow rate measurements. The air mass flow rate measurements are to be air conducted using vruious flow rate measurement devices, allowing an accuracy comparison study runong the different devices. The experimental lab setup also incorporates a device to measure the discharge coefficient of different disk geometries. Several design concepts were generated throughout detailed analysis of various flow rate measurement devices and data acquisition systems, which results in the optimum device configuration setup. The Need for the Project

The need for this project is The need wr this project is to provide an opportunity for

to provide mechanical undergraduate mechanical engineering students to compare what

engineering students with they learn in classrooms Ito the real working application settings,

hands-on experience air particularly in the mass flow rate measurements. Oftentimes, in air mass flow rate theories and illustrations taught in engineering courses do not

measurement. present clear understanding for engineering students without the

actual theory applications, such as in laboratory experiments. It is

important for mechanical engineering students to be capable of

conducting an mass flow rate measurement, as it is one of the air many common measurements performed frequently by mechanical

engineers.

The Design Project Objectives and Requirements

The objective of this project Design Objectives

is to develop a laboratory The primary objective of this design project is to develop a setup to perform air mass laboratory setup to perform mass flow rate measurements using various air flow rate measurements and measurement devices. Although the theory behind flow rate measurements allow students to compare only requires simple understanding of fluid mechanics and measurement the accuracy of various analysis methods, there are many methods and devices that can be used to measurement devices. measure mass flow rate. These different devices posses variable degree air of measurement accuracy, allowing the students to perform an accuracy

study of different measurement devices. Design Requirements

The main requirement for this design project is to assemble four (4) off-the-shelf flow rate measurement devices, which should fit

on a feet by feet table. general requirements, the flow rate 3 6 As measurement system should be able to operate with maximum inlet

pressure of psig at room temperature. The flow rate measurement 100 system should also be able to provide a maximum air mass flow rate

measurement of O.l lbm/s. an additional preference, the flow rate As measurement system is going to be assembled using type copper L tubing with a pipeline size of one inch. Detailed requirements (1) were later added to the design such as a maximum pressure difference

of inches of liquid and a throat diameter of inches for the 32 0.15 critical venturi. Design Concepts Considered

Four design configurations Four (4) design configuration concepts were generated throughout

were generated, which detailed design analysis during brainstorming sessions. The main

present main difference that governs the different design concepts is the the difference of a series and parallel configuration setup of :series or parallel. The generated design

concepts include a series assembly with sliders, a series assembly with assembly configurations. bypass, a parallel assembly and a combination of series and parallel

combination configuration.

Both the series and parallel device configuration have each own

advantages and disadvantages. As an advantage, the series device ValYr.�- i assembly provides consistent (uniform) mass flow rate throughout the 0"'""""" flow. the other hand, a series assembly requires more space for On device placement locations when compared to the parallel assembly.

In contrary, a parallel series requires less space for the device

configuration to fit on the table. Inversely, a parallel series will not

provide consistent mass flow rate, which is crucial for the practice of 0 ::?:!!'g...-lc.tors comparing the accuracy of ditierent flow rate measurement devices. with Bmass Series Further consideration that was used to determine the optimum

device configuration setup is the order in which a device is to be

placed within the system. Different order of placement affects the • YO� Parallel -Series inlet pressure coming in a device, preventing it to operate properly as

different devices require a minimum value of inlet pressure.

With the help of a decision matrix, the series assembly presents a /;;;:_ w -�. frttt· preferred device configuration assembly as it provides a consistent $ v�cv�= mass flow rate within the flow, which is required to conduct accuracy

comparison of different measurement devices.

Recommended Design Concept

The recommended design The recommended design concept incorporates a series

concept has the highest assembly for the device configuration assembly with several bends on

credibility on fulfilling all the the piping, in order to accommodate the space provided by the feet 3 requirements needed for this by feet table. The device assembly consists of four (4) off-the-shelf 6 L project. This design concept flow rate measurement devices in the following order of placement is a combination of all good critical venturi, orifice plate, discharge coefficient measurement

aspects of the various design device, pitot tube androtameter. The minimum required inlet pressure

concepts that were conceived for each device determines the order of placement of the flow rate

earlier. measurement devices. A brief description of each flow rate measuremeDt device used in this system is described in the following

section.

A critical venturi is a converging-diverging nozzle with sonic

flow condition at the throat section, which results in a Mach number

of This sonic flow at the throat results in the constant pressure ratio 1. of between the inlet pressure and total (stagnation) pressure 0.5283 Critical Venturi within the flow. This condition allows the mass flow rate calculation

through the critical venturi to depend only on inlet pressure, inlet

temperature and the throat area. A critical venturi was chosen to be

included in the flow rate measurement system due to the fact that it

provides the best measurement accuracy of ±1%. An orifice plate creates an area difference when the flow

passes the inlet location and the bore location of the orifice plate. As Orifice Plate illustrated in the Continuity equation, in which the mass flow rate

within the flow in a series assembly must be constant, the area . . · difference created by the bore results in pressure difference to be hL;,� . measured by the students in calculating the mass flow rate. The orifice · .. ·. . ·.·• -· ...... · · < . .·.··•·•• . �. · . ·�-.·.· ,..· 'F' . ···· plate possesses a measurement accuracy of . ±3%. Averaging . . Pitot . ·. .Tube.. . . A similar principle is applied by the pitot tube, which creates l r· a pressure difference value to be measured by the students. This value

! of pressure difference is the average of four (4) measurements taken L in four different points in the tube within the flow. The pitot tube has a measurement accuracy of Another device used in this system ±3%. is a rotameter, which directly measures the volumetric flow rate of the

system to be converted later to obtain the mass flow rate value. The

rotameter is a flow rate measurement device with the least

measurement accuracy of ±5%. An additional device is incorporated to measure the

discharge coefficient of different disk geometries. A discharge

coefficient is a coefficient used to describe the ratio between the

actual mass flow rate and lthe ideal mass flow rate. The actual mass

flow rate is obtained from the measurement performed during the

experiment, through one of the flow rate measurement devices, either

Discharge Coefficient the critical venturi or the orifice plate. The ideal mass flow rate is Provision calculated using Dynamics principles. Different disk geometries Gas will be used during the experiment to illustrate the different values of

discharge coefficient of different geometries. Recommended Improvements

In order to provide the To proceed on with the experiment with a finished assembly,

students with the highest conventional pressure and temperature measurement devices, e.g.,

quality and latest im manometers and thermometers, could be used. But with the modem technology, a data acquisition industry automation technology, however, the process could be

unit can be incorporated to simplified with a data acquisition system. Although this project's

enable measurements to be intention is to have students learning the concept of measurement of

taken digitally. airflow mass rate, it is also very helpful to provide an accurate

solution with the data acquisition system. Furthermore, it is also a

good learning experience for our group members.

Utilizing regular Pes, standard data acquisition systems consist of

three parts: data collector, interface, and software. The data collector

part collecting data from pressure transducers, thermocouples, and so

on. These transducers change the measured results like pressures and

temperatures into very small voltages. Then the electrical signals pass

through the interface into the The software could then process the PC. signals and based on transducer's calibration curve to convert the each electrical signals back Ito the desired pressure and temperature

measurement. Memorandum

Date: 6/2/1999 To: Professo r. Ko walski and Professo r. Tasli m From: Ai r Mass Flow Rate Measu rement Group Lette r of Trans mittal RE:

As tea m me mb ers fo r the Design of Ai r Mass Flow Rate Measu rement Syste m, we would like to sub mit ou r re port on the design of a labo ra to ry syste m setup to me asu re ai r ma ss flow ra te. The objective of the re po rt is to desc ribe the ove ra ll design process on the labo ra to ry syste m setup that will be used by engineering students in gaining knowledge in the field of ai r ma ss flow ra te

me asu rement. The objective of the design proj ect is to design a labo rato ry syste m setup to

me asu re ai r ma ss flow ra te using fou r off-the-shelf me asu rement devices and to provide an additional device to me asu re the discha rge coefficient of va rious disk geo met ries. The tea m ca me to a conclusion that a se ries type asse mbly will be suitable to fulfill the design re qui rements. This conclusion is supported by va rious testing and extensive calculation ve rification , as explained in detail in the design re po rt.

Th ro ughout the design process , the tea m has le arned to co mpromise and help each othe r as a tea m to acco mplish the fin al design goal and that wo rking togethe r and prope r co mmunication can ove rco me obstacles in exp ressing ou r ideas. We acknowledge ou r success in the design process to the assistance of Professo r Tasli m as ou r project adviso r and Professo r

Ko walski as ou r cou rse adviso r. The tea m will be available to answe r any questions re ga rding info rmation he rein as well as provide additional co mments at the re ade r' s re quest. TablP. of Contents

Memo of Transmittal ...... I Table of Conten1ts ...... II List of Tables ...... IV

List of Figures ...... V Acknowledgements ...... VI Copyright ...... VII Abstract ...... VID

1. Introduction ...... 1-1 1.1 Proj ect Need and Ob jective ...... 1-1 1.2 Gene ral Design Requi re me nts ...... 1-1 1.3 Detailed En ginee ring Design Specifications ...... 1-2 1.4 Repo rt St ructu re...... 1-3 State of The Art Research ...... 2-1 2. 2.1 Patent Sea rch ...... 2-1 2.1.1 Classifications ...... 2-2 2.2 Patent Relevance ...... 2-7 2.2.1 Patent Originality ...... 2-7 2.2.2 Co mpetition ...... 2-8 3. Theory Development ...... 3-1 3.1 Mass Flow Rate Measu rement Theo ry ...... 3-1 3.2 Measu rement Device Theo ry ...... 3-3 3.2.1 Critical Ventu ri ...... 3-4 3.2.2 Orifice Plate ...... 3-8 3.2.3 H.o ta mete r ...... 3-10 3.2.4 Ave raging Pitot Tube ...... 3-11 I 3.2.5 Discha rge Coefficient Measu rement Device ...... 3--14 3.3 Head Loss Theo ry ...... 3-15 4. Conceptual Designs for Device Assembly ...... 4-1 4.1 Se ries Configu ration with Sliding Track ...... 4-1 4.2 Series Configur ation with ByP ::-ss ...... 4-2 4.3 Series Parallel Combined Configur ation ...... 4-3 I 4.4 Parail el Configur ation ...... 4-3 4.5 Decision Matrix ...... 4-4 5. Proposed Device ConfigurationAssembly ...... 5-1 6. Data Acquisition System ...... 6-1 7. Design Issues ...... 7-1 7.1 Parts ...... 7-1 7.2 Tole rance .,...... 7-1 7.3 Safe ty ...... 7-2 7.4 Bill of Materi al s ...... 7-2 7.5 Cost / Fin an ci al Is sues ...... 7-3

7.6 Project Pl an ...... 7-4 7.7 Testing Activities ...... 7-4 7.8 Codes Compli ance ...... 7-5 8. Report Conclusion ...... 8-1

Appendix A. Critical Venturi Calculation ...... A- 1 Appendix B. OrificePlate Calculation ...... B- 1 Appendix C. Minimum Pipe Entrance Length Calculation ...... C-1 Appendix D. Patents ...... D-1 References ...... E-1 Li�t of Tables

Table 1 - Comparison Factors between Proposed Design and H10 Apparatus 2-9 Table 2 - Decision Matrix 4-5 Table 3 -Bm of Materials 7-3

List of Figure:§

Figure 1 H10 Flow Measurement Apparatus 2-9 Figure 2 Critical Venturi 3-7 Figure 3 Orifice Plate 3-10 Figure 4 Rotameter 3-11 Figure 5 Averaging Pitot Tube 3-13 Figure 6 Discharge CoefficientMeasurement Device 3-14 Figure 7 Series Configuration with Sliding Tracks 4-1 Figure 8 Series Configuration with ByPass 4-2 Figure Series Parallel Combination Configuration 4-2 9 I Figure 10 Parallel Configuration 4-4 Figure 11 Venturi Throat Diameter Calculation 5-2 Figure 12 OrificePlate Bore Diameter Calculation 5-2 Figure 13 Ave:raging Pitot- Tube Calculation 5-3 Figure 14 Rotameter Calculation 5-3 Figure 15 Data Acquisition System Setup 6-2 Figure 16 VI Illustration 6-3 Figure 17 Output of Lab Tech 6-4 Acknowledgem,ents

The Air Mass Flow Rate Me as urement Design te am would like to take this opportunity to th ank the many people who have contributed both directly an d indirectly to the completion of this design pro je ct an d the design report . We would like to th ank Professor M. Taslim , Professor G.

Ko walski , Matt Ulinski , Jo n Doughty , Professor D. Harper an d our fellow cl assm ates for their technic al contribution . We would al so like to th an k Hor aci a's Welding an d Met al Sheet

Comp an y for their as sembly support an d parts contribution on this pro je ct . Our most import ant ac knowledgements ar e bestowed to God , our loving parents, brothers , sisters an d friends for without their undying mor al support , none of these would have been possible. Copyright

"We, the te am me pbers,

Ari an ne Narty as ari

Mi� ae l Tavares hereby as sign our copyright of this report an d the corresponding Executive Summ ary to the Mech anic al, In dustri al an d Manuf acturing Engineering (M IME) Dep artment of No rthe as tern

University." We al so hereby ag ree th at the video of our Or al Present ations is the full property of the MIME Dep artment.

Public ation of this report does not constitute ap prov al by Northe as tern University , the MIMEDep ar tment, or its faculty members of the fi ndings or conclusions cont ained herein. It is published for the exch ange an d stimul ation of ide as. Abstract

In the field of engineering studies, experimental lab activities are necessary for engineering students to relate what they have learned in class as ideal situations to the actual application settings and conditions. This project presents a design of an experimental lab setup for undergraduate mechanical engineering students to perfmm air mass flow rate measurements. The air mass flow rate measurements are to be conducted using various flow rate measurement devices, allowing an accuracy comparison study among the different devices. The experimental lab setup also incorporates a device to measure the discharge coefficient of different disk geometries. Several design concepts were generated throughout detailed analysis of various flow rate measurement devices and data acquisition systems, which results in the optimum device configuration setup. 1. I 'J.troduction

1.1. Project Need and Objective

In this age of civilization driven by technology and computerized processes, educators around the world agree that it is not enough for students to acquire knowledge in depth by just learning the background theory without the theory application. Especially in the college level, students majoring in technical fields of engineering must be fully introduced to the theory application in order to prepare them for the working application in the "real engineering world". The design project of designing a laboratory system to measure air mass flow rate is driven by this need to provide college students majoring in mechanical engineering with practical knowledge of air mass flow rate measurement. The objective of this design project is to design a laboratory system setup to be used by mechanical engineering students for air mass flow rate measurement. This design project was requested to be a part of the Capstone Senior Design course by our project advisor, Professor Taslim. Air mass flow rate measurement is an important aspect in the mechanical engineering industry and is one of the common measurements performed by mechanical engineers in daily basis. Unfortunately, mechanical engineering students at Northeastern University have never conducted air mass flowrate measurement as a part of the laboratory experimental activities, due to the lack of the experimental setup. Therefore, our proposed design will fulfill the need of mechanical engineering educators at Northeastern University in exposing the mechanical engineering students to the practical application of air mass flow rate measurement.

1.2 General Design Requirements

Our design project of designing a laboratory system setup to measure air mass flow rate is constrained by the following general design requirements stated by our design project advisor:

• The laboratory system setup must use four (4) different air mass flow rate measurement devices including an orifice plate, a critical venturi and a typical f1owmeter such as a rotameter. • The laboratory system setup should also include a provision to perform a discharge

coefficient measurement within the same system and devices.

• The laboratory system setup must be able to be used as one of the experiments in the undergraduate Fluid Mechanics as well as Measurement and Analysis Lab.

• The laboratory system setup should be self-contained with minimal assembly requirements. L • Most assembly components and instrumentation in the laboratory system setup including the air mass flow rate measurement devices, should be off-the-shelf parts.

• The laboratory system setup must be able to operate properly using available compressed air

at maximum pressure of 100 psig, room temperature of 80° F, which will provide a

maximum air mass flow rate measurementof 0.1 lbrnls.

• The laboratory system setup must be equipped with a clearly written laboratory manual in order to ensure safety and proper use of the laboratory system setup.

1.3 Detailed Engineering Design Specifications

Aside from the general design requirements presented proposed by our design project advisor, our design project of designing a laboratory system setup to measure air mass flow rate is also constrained by the following detailed engineering design specifications:

• In the beginning of the design project stage, our design advisor suggested that the laboratory system setup should accommodate a critical venturi that is already available to use in other laboratory system setups due to the high cost of purchasing a new critical venturi. Once our budget was approved, it was determined that there is sufficientfun ding to buy a new one.

• The mass flow rate measurement conducted using the laboratory system setup must not create any pressure drop that exceeds 30 inches of fluid (oil, water or mercury) height within a measurement device. This constraint is applied to the design in the event that the air mass flow rate measurement is performed conventionally (the maximum scale of any off-the-shelf

manometer is 30 inches).

• The laboratory system setup must fit into a 4' by 6' table.

• The design configuration of all the measurement devices must maintain a consistent mass flow rate measurement. • The design configuration of all the measurement devices must not introduce a exceedingly large pressure drop within the measurement system.

• The overall assembly configuration must conform to AS ME and other industrial codes.

1.4 Report Structure

The objective of this design report is to describe the overall design process in designing a laboratory system setup to measure air mass flow rate. The first section of the report describes the need and the objective for the design project, as well as the general requirements provided by l our design advisor and the detailed engineering requirements necessary to maintain the working ability of the measurement system design. The next section of this report focuses on the various research activities that were done preliminary to the design process. The objective of conducting this state-of-the-art research is to explore various existing designs similar to our proposed measurement system and to observe any competition in the measurement system design field. Most of the research activities were performed on the World Wide Web and several libraries in learning the theoretical background of the proposed design. The state-of-the-art research revealed that although many of the existing patents are similar to the design of our measurement system, none of them has the same devices of system functions as previously stated in our design project objective. One of the important parts of this design report is explained in the next section, the Theory Development. This section explains in great detail each technical principle that governs every calculation and analysis performed throughout the design process. The theory development section contains the three main principles of the design project: Continuity Equation, Pressure Loss Equation and the Ideal Gas Law. This section also explains in detail the theory development that supports every measurement devices, in order to determine several critical parameters of the measurement devices. Moreover, this section explains the equations behind the calculation of pressure loss within the flow measurement system. The next section of this report contains the description of the conceptual designs for the assembly configuration that were developed by the team members during several of our brainstorming sessions. This section also illustrates the decision matrix that was used by the team members in determining the proposed final design configuration of the measurement devices. The details of the final proposed design c Jnfiguration are described in the following section. This section contains the final specification of each air mass flow rate measurement devices, the final assembly configuration, which includes the calculation of minimum required pipe entrance length and the calculation of pressure loss within the measurement system. The measurement method for performing the experimental using the designed measurement system is described in detail in the next section. This section describes the two possible methods for obtaining the air mass flow rate measurement from the system. As a comparison, this section also analyzes the advantages and disadvantages of obtaining the air mass flow measurement from the system using specific technical software. Before the report conclusion is presented, the report will discuss other design issues such as the bill of materials, the part lists and the overall design cost analysis. In addition, the report also presents all the testing activities performed including their results and the completion of the safety precautions and the laboratory manual. 2. State of the Art Research

2.1 Patent Sean�h

This section explains all the state-of-the-art research activities performed preliminary to the design process. Any inventions made by an engineer have their originality and therefore, in order to secure their work a patent application should be filed with the U.S. Government. According to the U.S. Patent and Trademark Office, a patent for an invention is a grant of a property right by the Government to the inventor (or his or her heirs or assigns). The term of the patent shall be 20 years from the date on which the application for the patent was filed in the United States. The right conferred by the patent grant extends only throughout the United States and its territories and possessions. During the design process of air mass flow rate measurement system, a patent search was conducted on existing various measurement apparatus dating back to the late of 1970s. Although many of the patents found are somewhat similar to the proposed design of the laboratory system setup, there is a significant difference between the objectives of the design and the measuring instrumentation used. Other than that, a patent search was also conducted on each measurement device to be used on the design of laboratory system setup. Among the measurement devices, a complete patent search has been performed on the orifice plate and critical venturi. The patent search is conducted in the early phase of the design project due to two important aspects of the design process. Firstly, a patent search contributes ideas to the design process. The phase of the design process in which conceptual designs are generated arises from previous patents, which further lead to brainstorming sessions and improvisations of the existing concepts. Secondly, the results of the patent research revealed the fact that flow-measuring apparatus have been accustomed to patent index. The existing patents found can be categorized into six different classifications as follows:

• Flow measurement apparatus using a single device

• Flow measurement using high technology research equipment

• Flow measurement apparatus for an internal combustion engine

• Flow measurement device for air at atmospheric pressure

• Flow measurement system for steam at elevated temperatures • Flow measurement techniques for multi ryhase flows

Although these patents may not directly apply to our design project, they may help to generate ideas for our conceptual design concepts. Other than that, patents with improvement of techniques or means of providing better results would assist in refining the design although they are not directly applicable.

2.1.1 Classifications

2.1.1.1 Flow measurement apparatus using a single device Many of the patents found are devices used to measure volumetric flowrate with a single device like an orifice plate or venturi tube or nozzle meter. In comparison to our design, at least four devices would be used to measure mass flow rate. Among the many single device patents, below is a list of examples and its abstract of the patents using a single device (extracted from the patent):

o Variable orifice air flow measuring device and method (US Patent Number 4,570,493) "A device for measuring the volume of air flowing into or out of an air conditioning duct. The device includes a hood having a top end adapted to cover the air conditioning duct to provide channeling of the air flow into an air flow measurement housing. The airflow measurement housing includes an air flow channel and a manometer fvolumes may be determined."

o Flow bench and air flow measurement and calibration procedure (US Patent Number 5,808,188) "A pneumatic system for comparing air flow characteristics of different unknown flow restrictions. The first head or piece of equipment and a base orifice are installed in tum on the flow bench and air flow rates are measured for each using a critical flow venturi nozzle. The

base orifice flow rate is referred to as pl. The first head or piece of equipment flow rate is referred to as p2. A small orifice is identified which equates in flow rate to the first head or piece of equipment, p=p2• A flow coefficient can be calculated were R1 ==p2 /p1• A second head or piece of equipment, for comparison, is then flow tested at the same location or at another location under different atmospheric conditions. The ratio of the first condition flow rates p2 /p1 multiplied by the base orifice flow rate at condition two, p3, allows calculation of a theoretical flow rate for the first small orifice (or first head or piece of equipment) at condition two, p4. Once measured, the flow rate of the second head or piece of equipment at condition two (p) may be compared to the theoretical first small orificeflow rate at condition two, (p4), to determine relative performance of both heads or pieces of equipment at condition two or as between each other either at condition one or condition two. In an alternate embodiment, the system compares the relative air flow characteristics of different race engines."

o Pipeline Flow Measurement Proving System (US Patent Number 4,566,307) "A pipeline flow measurement proving system has a custody transfer insertion turbine meter mounted at a first location on a fluid pipeline. A proving insertion turbine flow meter is mounted at a second location on the pipeline upstream from the custody meter at a distance of approximately ten diameters of the pipeline. This offset spacing reduces the fluid turbulence, which may be produced by the turbine head of the proving meter. The proving meter is calibrated against a standard at the National Bureau of Standards. Each of the flow meters produces a pulse signal, which is proportional to the rotation of the corresponding turbine head. The calibration is carried out by counting the number of pulses produced by the two meters during a selected time period. The ratio of the counts of the pulses comprises a calibration constant, which is utilized by a custody transfer flow computer for producing a flow measurement. The proving insertion turbine flow meter can be utilized to calibrate a plurality of custody meters or can be utilized as a backup for the custody meter." 2.1.1.2 Flow measurement using high technology research equipment Every new products and inventions created show that advancement in technology is happening. Likewise, flow measurement devices are also moving towards better and more precise measurements. Examples of such patents are listed in the following:

o Universal Sensing Apparatus For Sensing Volumetric Rate Of Fluid Flow (US Patent Number 3,765,241) "The sensing apparatus has two tubular members, each with a row of axially spaced side openings, a hollow threaded bushing extending from each end of each member, an end plate on either end of the tubular members, with the bushing extending through spaced holes in the end plates to rotatably mount the members thereto in spaced relationship with each other for being installed in a duct with one bushing of each tubular member extending through the wall of the duct to mount the sensing apparatus to the duct and to connect with means for measuring differential fluid pressure to sense the volumetric rate of air flow. The apparatus has mating dimples for indicating desired rotative positions of the axially spaced openings on the tubular members, a wrench slot in each bushing for receiving a wrench to rotate the bushing and the tubular member attached thereto, and axially spaced fins to provide smooth fluid flow over the tubular members. A template is provided with the apparatus for affixing to the wall of the duct to indicate the location to drill the holes for the� bushings, and to provide a chart for converting differential fluidpressure into volumetric airflow.

o Air-flow Capture and Control Device for Flow Measurement (US Patent Number 4,231,253) "Four curtains are drawn or released together to set the measuring aperture of an air-flow measuring box at the desired area and the linear velocity of flow through the aperture is measured by a single-probe velometer normally held with the probe tip essentially at the center of the aperture, a perimeter sealing strip blocks unmeasured air flow around the back of the curtains. A box-like hood guides the air flow from a ceiling outlet under investigation to the curtained aperture and is provided with diagonal vanes to keep the measurement from being falsified by cyclonic air movement. The box-like hood folds up for storage or transportation." o Air-flow Limiter and Measurement Device (US Patent Number 4,334,64ID "An air conditioning system including an air flow limiter and indicator comprising, in combination: a chamber (24) extending from an inlet (21) to an outlet (22) for flow there between of conditioned air at greater than ambient pressure; a damper (63) in the chamber actuable to variably restrict the flow; apparatus outside the chamber, including an inflatable member (66) having inlet (70) and venting (42) openings, for actuating the damper in accordance with the state of inflation of the member; condition-responsive apparatus, including a fluid amplifier (72) supplying fluid from the chamber to the inlet opening, for causing inflation and deflation of the inflatable member; apparatus including a vane (32) in the conduit for responding to the rate of flow of the fluid inthe conduit; apparatus (41, 57) normally closing the venting opening; and apparatus (43, 45, 55) operable by the vane as the rate of flow exceeds a predetermined value for unclosing the venting opening, to enable deflation of the inflatable means independent of the condition-responsive apparatus."

2.1.1.3 Flow measurement apparatus for an internal combustion engine The patent search also revealed a few patents that are measurement devices for application on an internal combustion engine. Airflow into an internal combustion engine is important because it governs the working operation for the overall system. The following patents describe such conditions:

o Device for air flow rate measurement in the air intag tube of an internal combustion engine (US Patent Number 4,344,322) "A device for air flow rate measurement in the air intake tube of an internal combustion engine which has at least two temperature-dependent resistors in different branches of a bridge circuit having closed-loop electric current control, and which is characterized in that the temperature-dependent resistors are embodied as hot wires, that a temperature above the aspirated air temperature is selected for both hot wires, and that the difference of the hot wire temperatures is held to a constant value. The purpose of the device is to provide airflow rate measurement that is as error-free as possible, even when the aspirated air temperature is fluctuating rapidly. An identically embodied suspension and fastening of the individual hot wires is given as an example for the spatial disposition of the individual hot wires in the air

intake tube."

o Apparatus for temperature control of a resistor used_for measurement purposes, especially in internal combustion engines (US Patent Number 4,3�829) "An apparatus for the temperature control of a resistor used for measurement purposes, in particular, in combination with air flow rate measurement purposes, in particular, in r combination with air flow rate measuring devices in internal combustion engines for a vehicle wherein the temperature of the resistor with current flowing through it is regulated i during the measurement phase and in particular, operational states of the system provided with the apparatus and/or at particular times, the flow of current through the resistor is increased for the purpose of burning off dirt particles, which would falsify the measurement result, from the surface of the resistor which is formed, for example, as a hot wire. The apparatus includes a memory for picking up a signa1 such as whether a particular engine temperature is present at the beginning of one operational cycle or not and when this temperature is present, a red-hot heating procedure is omitted when the engine is subsequently turned off. In addition, the increase in current for initiating the red-hot heating procedure may also be controlled in accordance with operational duration and driving distance of the vehicle and in accordance with time."

2.1.1.4 Flow measurement device for air at atmospheric pressure Other than measuring flow at high pressure, flow rate can also be measured at atmospheric pressure. In order to measure flow rate at low pressure, very sensitive equipment would need to be used. This because flow measurement is strongly related with pressure drop and having pressure at low pressure does not assist the measurement of flow.

2.1.15 Flow measurement system for steam at elevated temperatures

o "Measurement of Steam Quality and Mass Flow Rate" (US Patent number 5,421,209) Lots factors need to be included when measuring airflow. When measuring steam flow rate, the density or quality of the steam needs to be measured. This is because mass flow rate of steam would differ for every different density of the steam. Temperature would also affect

the mass flow although not significantly. In order to determine the flow rate, an orifice plate would be positioned in series with a critical venturi within a conduit.

2.1.1.6 Flow measurement techniques for multi phase flows o Means and techniques useful in mass flow meters for multiphase flows (US Patent Number 4,604,902) The technique for measuring a multi phase flow is discussed in this patent. First, the mixture is passed through a first measuring station, which comprise of a Venturi meter, and differential pressure is measured. This differential pressure represents the mass flow rate of the mixture and velocity. Next,, the flow is passed through a second station where the temperature difference is measure. By increasing the temperature, the density of each component in the mixture will change individually and the corresponding change would indicate the mass flow rate of each component.

2.2 Patent Relevance

Patents are important mainly because they protect the copyright of the inventor and assist other engineers in generating improvement ideas. During the design process of designing air mass flow rate measurement system, the patent search activities provided aid and expertise for team members to gain complete understanding of the design project and the competition available in the market. The patent search activities also provide useful information on the knowledge of the existing devices to be used on the design assembly.

2.2.1 Patent Originality

According to the U.S. Government, a patent is a grant of property right of an invention to the inventor. Thus, patents provide the inventor a sense of security knowing the fact that his or her invention is safe from perpetrators. Other than that, patents provide other inventors with information about the originality of their new ideas, in order to avoid the case in which the idea

has been invented and patented previously. Therefore, patents also function as prevention against confusion and deceit among inventors and their inventions. For the purpose of our design project, patent search activities provide design team members with information whether a laboratory setup for measuring air mass flow rate has been previously invented. Other than providing inventors with the information on the originality of their patent, they also provide information on improvement of techniques for measurement using the device. Examples of improvement would be a better method of devising the flow of the design, a better means of measuring the output or a more efficient way of placing the devices. The generation of new ideas or concept, as discussed earlier, is the most important part of the design process. After performing a patent search, an observation on the patents would contribute new ideas or concepts to the design process of our laboratory setup. Therefore, a patent not only provides security but it also provides inspiration for new ideas and concepts.

2.2.2 Competition

During the patent search activities, we did not find any patents that resemble the proposed design of the air mass flow rate measurement system. However, from our research conducted through the World Wide Web, we found that a company located in England [ manufactures a similar mass flow rate measurement setup called HlO Flow Measurement that utilizes CAL Software (see Figure 1). Table 1 below provides the difference between our proposed design and the HlO Flow Measurement design. Other than flowmeasurement, the HlO Flow Measmement apparatus also provides direct comparison of flow measurement between a Venturi Meter, an OrificePla te and a Rotameter. All these devices are mounted on a 900mm x 210mm plate and have an approximate height of 925mm. The HlO Flow Measurement apparatus is also equipped with Computer-Aided Learning Software compatible with all types of personal computers.

HlO Apparatus Proposed Design Working Fluid Water Air

Space Required 900 mmx 210 mm 6 feet x 4 feet Mass/Volumetric Flow Rate 28 min O.llbm/s U Discharge CoefficientDevice Does Not Exist Exists Software Requires special software Fl exible Price High Low

Table 1. ComparisonFactors between the Proposed Design and H10 Apparatus

Figure 1. H10 Flow Measurement Apparatus 3. Theory Development

3.1 Mass Flow Rate Measurement Theory

There are three basic Fluid Mechanics principles that govern the measurement of air mass

flow rate. The first principle is the Energy Balance equation, which conveys the relationship between pressure, density, velocity and elevation of the flow measurement condition. The physical form of the Energy Balance equation for any two given condition points is illustrated in the following:

It (1)

The Energy Balance equation applies to any points with flow conditions on a streamline in a steady, inviscid flow. This equation states that the total effect of pressure, density, velocity, specific weight and elevation of a fluidflow in a system is constant in every measurement points, with consideration of the head loss. The constant total effect of all factors of flow conditions confirms that an increase in one factor will cause a decrease in the others. Conversely, a decrease in one factor will cause an increase in the others. The air mass flow rate measurement uses this basic understanding as a foundation for all the calculation process. Since the mass flow rate is derived from calculation of flowvelocity, the relationship between pressure and velocity from the Energy Balance equation governs the calculation of mass flow rate. The use of the Energy Balance equation to relat'e flow pressure and flow velocity must be

incorporated with the Conservation of Mass principle as illustrated in the following equation:

(2)

This basic principle states that the mass flow rate is constant in every measurement points within the flow. The mass flowrate is calculated using the following equation: m =pAV (3)

Equation (2) states that the mass flow rate is obtained as a product of flow density, cross sectional area of the flow and the flow velocity. This principle reaffirms that the total effect of flow velocity and cross sectional area of the flow is constant in every measurement points. Reducing the cross sectional area of the flow will increase the flow velocity. Conversely, an increase in the cross sectional area of the flow will reduce the flow velocity as illustrated in equation (2). The equation for the Conservation of Mass (also known as the Continuity Equation) allows the regulation of flow velocity by modifying the cross sectional area of the flow. Assuming that the flow measurement is conducted in two locations at the same elevation, the combination of Bernoulli's equation and Conservation of Mass produces the following relation:

(4)

Equation (4) allows the calculation of velocity from given values of cross sectional areas and pressure measurement at two different locations. The combination equation states that in order to calculate the flow velocity, lab users need to have the value for the flow density, p. The calculation of flow velocity is required to compute the volumetric flow rate, by multiplying it with the cross sectional area of the flow. In addition, since the objective of the lab experiment is to measure the mass flow rate, lab users need to convert the volumetric flow rate to the mass flow rate. This conversion is achieved by multiplying the volume flow rate by the flow density to obtain the value for the mass flow rate.

Since the type of fluid flowrate to be measured is air, the governing principle that supports this flow rate conversion is the Ideal Gas This principle allows the calculation of flow density Law. to convert the volumetric flow rate to the mass flow rate. The basic equation for Ideal Gas Law is illustrated in the following:

P = pRT (5) This principle presents the relationship between the flow pressure, flow temperature and flow density. Since the value of the flow density changes according to the flow pressure and temperature, the flow density can be calculated using the measurement values of flow pressure and temperature. The three basic principles described in this section are used as the basic for all experimental calculations. Most flow rate measurement devices also use those principles as a base for operation. Additional principles and formulas will be included in the experimental analysis for flow rate measurement devices that use special principles and calculation.

3.2 Measurement Device Theory

There are several factors that need consideration in designing a flow measurement w lI system. One factor is the output of the measurement device. Some measurement devices directly measure the mass or volumetric flow rate, such as flowmeters. However, most measurement devices provide indirect measurement, such as pressure indicator, which require further calculation to compute the flow rate. Most measurement devices also require flow calibration in order to provide the most accurate measurement. Another consideration is the measurement range. In most cases, measurement devices that indirectly measure the flow rate usually need connection to manometer or other similar devices as the flow indicator. These measurement connections are limited to certain measurement range. Measurement range is also limited by the material of the measurement device. Since some materials are not capable to withstand certain pressure value, the measurement device made from that material is constrained to handle a maximum flow rate. The measurement accuracy also varies within each device. The device accuracy depends greatly on the pressure loss when the flow is constrained by the device restrictions. The measurement device that has the most complicated measurement concept, such as a venturi, usually yields the best accuracy. On the other hand, the measurement device with the simplest measurement concept, such as a flow meter, usually yields the least accuracy. The accuracy of a flow measurement device determines its manufacturing cost. Measurement devices with good accuracy require a more precise manufacturing process, which increases the manufacturing cost. The following section will describe every device that is selected as flow measurement devices

for the air mass flow rate measurement system.

3.2.1 Venturi

A venturi is a converging-diverging nozzle consisting of a main inlet section and a throat section that has a narrowed cross sectional area. Although a venturi applies the same basic principles of flow rate measurement, it has a distinct advantage of having the best accuracy with the minimum pressure head loss. A venturi is designed to provide a relatively streamlined contraction that eliminates separation ahead of the throat. Moreover, the geometry of the venturi is arranged such that it provides a very gradual expansion downstream of the throat. This factor eliminates separation in the decelerating velocity in the section of the device. The combination of these two factors allows a venturi to reduce the pressure head loss to a minimum. The minimum head loss associated with the flow measurement using a venturi is due mostly from the friction losses along the wall, instead of from separated flows and the inefficient mixing of the flow. This distinct advantage allows a venturi to have the best accuracy as a flow rate measurement device of ± 1%.

There are two main types of venturi. The first type is known as a delta or pressure P differential venturi. This type of venturi applies the basic principle of flow rate measurement, such as Energy Balance equation and Continuity Equation. The measurement output of a delta P venturi is pressure difference between the pressure at the inlet section and the exit section of the venturi. Pressure taps from the inlet section and the exit sections of the venturi are attached to a pressure indicator, such as a pressure gage. If a manometer is used to indicate the pressure difference, the liquid elevation difference in the manometer indicates the pressure difference between the two sections. A modified Energy Balance equation used in the flow measurement principle of the venturi is illustrated in the following:

P ( ) = (Vexit -v;nlet) -· (6) Pinlet - Pexit 2 + Y Zexit Z;nlet The conservation of mass principle presents an understanding that the flow velocity at the throat is equal to the ratio of the area at the inlet and exit sections, multiplied by the flow velocity at the inlet section.

_ �nlet V (7) exit - A. inlet exll V

By using an assumption that the flow pressure for the inlet and the throat section is measured within the same elevation, Equation (7) can be simplified into the following:

2(pinlet - Pexit ) V= (8) p(l - (D D exit I inlt't t)

For nomenclature simplification, the exit-to-inlet pipe diameter ratio (Dexit Dinle ) is defined as I t /3. The throat velocity obtained from Equation (8) allows further calculation of the volumetric fl ow rate, Q. However, since there is a pressure head loss associated with the measurement, a

Ve nturi discharge coefficient, Cv, is introduced to the equation. The parameters that affect the value of this discharge coefficient are as follows:

• �ratio

• Reynold's number

• Shape of converging and diverging sections

By taking the discharge coefficient factor into the measurement process, a final equation to calculate the actual volumetric fl ow rate, Qactual, is illustrated in the following:

2(pin/et -- Pexit ) (9)

In order to calculate the mass flow rate, the volumetric fl ow rate obtained from computing

Equation (9) is converted by multiplying it by the flow density. The flow density should be computed by using the ideal gas relationship described earlier in Equation (5). The second type of a venturi is known as the critical venturi (see Figure 2). Similar to the delta P venturi described earlier, a critical venturi is described as a converging-diverging nozzle consisting of a main inlet section that comes from the pipe: or tubing, and the throat section that has a reduced cross-sectional area. The main difference between the delta P and the critical venturi is that the flow in a critical venturi is choked and therefore the gas dynamics principles for compressible flow are applied for the calculation of the mass flowrate. This is accomplished by designing the throat section of the venturi to have precisely calculated diameter that allows the flow to hit sonic flowconditions at the throat. The sonic flow condition at the throat creates a shock wave that has special flow characteristics. The shock wave created at the throat allows the calculation of the flow rate to depend only on the upstream pressure, as a shock wave locks the downstream pressure to one fixed value. The calculation of the mass flow rate can be obtained directly from the following equation:

0 p � = z z-zr m + -1-M ) (10) inlet AM.fi

Since the fluidto be measured for the mass flow rate is air, the value for the specific heat ratio, y, is defined as 1.4. Moreover, the sonic flow condition at the throat means that the flow Mach number, M, at the throat is defined as 1. Applying these known constant values and the associated value for the gas constant of air, Equation (10) can be simplified as the following:

(11)

The simplified equation allows the calculation of the air mass flow rate just: by knowing the throat area and measuring the upstream pressure and temperature. For ventmi design purposes, it is necessary to calculate the desired pressure difference between the upstream and downstream location. This calculation is important if the venturi is to be included in a flow measurement system and connected to other measuring devices. For a critical venturi, the pressure drop at the throat section from the inlet section can reach a maximum of 50% of the inlet pressure. Once the mass flow rate is obtained, the flow velocity can be computed by dividing the mass flow rate by the flow density and the throat area. Once the fl ow velocity is computed, the Mach number of the flow can be calculated using the following

equation:

Mach number = v (12) JjRT

Using the isentropic flow table and the calculated Mach number, the ratio of pressure at the inlet (main section) and the total (stagnation) pressure can derived. In addition, the isentropic flow be table provides the ratio of the pressure at throat (Mach number equals to 1) to the total pressure to be 0.5283. Combining all the known ratios, the pressure at the throat can be calculated as the

following:

= --� t 0 r283 (13) P P X o al X .. ) throat inlet pinlet r The pressure drop within the fl ow between the main and the throat section of the venturi can be

computed by taking the difference between the measured pressure at the inlet (main section) and the calculated pressure at the throat. The value of the pressure drop allows furtherana lysis of the L venturi pl acement orloca tion within the overall system assembly.

L Figure 2. Critical Venturi

3.2.2 Orifice Plate

Another measurement device to be included in the air mass flow rate measurement system is an orifice plate that has a measurement accuracy of ±2 to 4% (see Figure 3). An orifice plate is a flat plate with a sharp-edged hole in the center that is machined precisely to provide a desired cross sectional area reduction. An orifice plate is placed concentrically within the tubing pipe and fastened together with two flanges in each side of the plate. The flow rate measurement done by an orifice plate uses a pressure difference principle from Energy Balance equation and Continuity Equation, similar to the delta P venturi. The hole in the center of the orifice plate creates an area difference, reducing the area of the pipe inlet to the bore area on the orifice plate. As illustrated by the Continuity Equation, the decrease in the area will create a velocity difference, accelerating the flow velocity when it passes the bore area of the orificepla te. The flow velocity of a flow restricted by an orifice can be calculated using the following equation:

2 = (pinlet ·-· Pbore ) V (14) p(l - (D D bore I inlet )4)

Since there is associated head loss in the flow rate measurement using an orifice plate, an Orifice discharge coefficient, Co, is introduced to the overall flow rate equation. This discharge coefficienttake s into account the effects of the turbulent motion that occurs near the orifice plate.

By integrating the orifice discharge coefficient, the actual flow rate passing through an orifice plate can be computed using the following equation:

(Pinlet -- Pbore ) actual -_ �o A bore (15) Q C w(l - (D D. 4 P bore I mlet ) ) The value of the orifice discharge coefficient depends greatly on the construction of the orifice

plate within the flow rate measurement system. Several factors that affect the value of the orifice discharge coefficientare listed as follows:

• Orifice plate edge (square, beveled)

• Pressure taps placements

• Ratio of Bore diameter to pipe diameter ((3)

• Reynolds Number (Flow velocity)

The important parameters necessary to calculate the volumetric flow rate is to obtain the value for the orifice discharge coefficient, and measure the flow pressure at the bore and at the pipe inlet section. The volumetric flow rate passing through the orifice can then be calculated using based on the standard atmospheric temperature and pressure.

L I I I_

Figure 3. Orifice Plate

3.2.3 Rotameter:

Another flow rate measurement device to be used in the measurement system a is variable area meter. A rotameter a good example of variable area meters (see Figure 4). The is first component of a rotameter a transparent, tapered metering tube that contains the fluid to be is measured. The second component of a rotameter a float that free to move vertically within is is the tapered metering tube and used to indicate the mass flowrate. working principle of a rotameter based on the pressure difference that caused by The is is different elevation in two measurement locations. the fluid flows vertically upward from the As pipe to the rotameter, the float rises within the tapered tube until it reaches an equilibrium height. The new position of the float balanced by the weight of the fluid, the drag force and the is buoyancy fo rce. fluid weight provides upward fo rces due to the fluid dynamic drag and This buoyancy. I L

Figure 4. Rotameter

The output of a rotameter is the volumetric flow rate, which can be read directly fromthe

calibrated scale on the transparent, tapered metering tube. The location of the float after the flow L indicates the associated flow rate. In order to compute the mass flow rate, the volumetric flow rate obtained fromreading the rotameter scale is converted by multiplying it by the flow density.

The flow density should be calculated fromthe standard atmospheric pressure and temperature.

Although :a rotameter is very easy to use in measuring the mass flow rate of a fluid flow, one can not be certainthat the measurement is accurate. Based on different scaling on the tapered metering tube, the measurement accuracy of a rotameter ranges from 5-10% of the scale. In addition, rotameter will have a certain safety issue as most rotameters are built from material that

will not be able to handle certain values of pressure. is a critical issue to be considered in This deciding which rotameter to use in the system as a high pressure flow may damage the rotameter

and the whole assembly.

3.2.4 Averaging Pitot Tube Another flow measuring device that would be used in the laboratory setup is an averaging

pitot tube (see Figure 5). An averaging pitot tube has its principle derived from a conventional pitot tube. The improvisation of integrating a number of pitot tubes together was the base of the averaging pitot tube. Like any conventional Pitot tube, the averaging Pitot tube works at the idea of having a pressure difference within the flow. A conventional Pitot tube is a tube with a 90° bend at the

one end of the tube and the other end of the tube attached to a manometer. There are actually two paths within the Pitot tube itself where one path is measuring the stagnation pressure and the other measuring the total pressure. When connected to a U-tube manometer, a difference in pressure can be measured. The same principle works on the averaging pitot except that a slot with up to four holes measures average pressure upstream and another slot measures the average pressure downstream. By comparing the output of both the measurements, a differential pressure would be obtained and comparing the output of both the measurements mass flow rate can be calculated. The holes on the slots are strategically positioned to allow precise measurement. Therefore, the profile of the flow that is measured must be considered. The best profile to be applied to the averaging Pitot tube a turbulent flow profile. This is because the holes on the slot are positioned to fit the profile of a turbulent flow. The output of the averaging Pitot tube is the same as a conventional Pitot tube that is in L inches of water. By attaching the mentioned end of the tube to a manometer, the results can be easily read and noted. Other than attaching it to a manometer, pressure transducers can also be easily attached and the data of the readout relayed to a data acquisition computer. The averaging Pitot tube is desired in this project because it solves the problem of positioning the Pitot tube strategically. Although the averaging Pitot tube has achieved a major breakthrough of solving the problem with positioning the tube, it still has an accuracy of± 3%. Figure 5. Averaging Pi tot Tube

3.2.5 Discharge Coefficient Measurement Device

Discharge coefficient is a value that accounts fo r factors that cannot be calculated theoretically. Examples of such factors are head loss induced after passing through an orifice

plate, and head loss due to friction and separation of flow in a critical venturi. Accordingly, this value is incorporated in the calculation of ideal (isentropic) mass flow rate when actual mass

flow rate is measured. A discharge coefficient measurement device (see Figure 6) can easily be

built using a large diameter pipe (also know as the plenum), a flow straightener, a flange, and two disks. Our design of the discharge coefficient measurement device is based on the high­

pressure plenum design. First, a large diameter (5 - 8 inches) pipe with a wall thickness of 0.37.5inches is cut to a length of about - 12 inches. This is fo llowed by welding a disk (with a wall thickness of 10 approximately 0.25 inches) to one end of the pipe and a flange on the other end of pipe. The disk is fitted with an adapter so that it canbe connected to the system. The flange end of the plenum

is supplied with a disk that would be used as the discharge coefficient measurement device (an

orifice). Basically, the discharge coefficient measured of an orifice plate (basically a disk with i

mactual = (15a) Cdischarge misentropic

In order to calculate the discharge coefficient, we would first of all determine the actual mass flow rate as well as the isentropic mass flow rate. The mass flow rate is to be computed by Equation (3). The isentropic mass flow rate can be calculated or derived from assumptions made as well as using the ideal gas fo rmula illustrated in Equation (5). The actual mass flow rate can be calculated using the same equations as above with the exception that pressure at exit is at atmospheric pressure. Other than that, sonic flow (Mach number equals to one) would have to be achieved at the exit on the disk. This is because isentropic condition needs to be attained in order to satisfy our engineering specifications for this particular experiment.

Figure 6. Discharge Coefficient Measurement Device

3.3 Head Loss Theory

The Energy Balance equation described in Section 3. 1 contains a balancing consideration for pipe head loss in the exit condition. With the assumption of a constant pipe diameter (D1 = D2) and horizontal pipe (z1 = z2) with fully developed flow, a simplified equation for calculating

the major head loss in illustrated in the following:

2 l V hzoss = (16) J D 2g

Similar to most pipe systems, our design assembly in the copper tubing also consists of additional components such as valves, bends and tees connection. These additional components introduce minor losses in pressure drop between the inlet and exit conditions within an air mass flow rate measurement device in the pipe. The pressure loss due to the minor losses introduced by the additional connection components can be calculated using the following equation:

1 2 11p = (17) KL -zPV

where KL value varies in accordance to the connection component. Specifically for our proposed piping design, Table 2 provides various values of KL for the connection components to be used in the assembly system:

Connection Component value KL -- Elbows, Regular 90°, flanged 0.30

Tees, Line Flow, flanged 0.20

- Tees, Branch Flow, flanged 1.00

- - Ball valve, fully open 0.05

Table 2. Various value to calculate Minor Losses KL

The detailed calculation for a specific flow condition is described in the Final Design Configuration section. 4. Conceptual Designs for Device Assembly

After the devices were chosen, the next step is to design the proper assembly configuration. The arrangement of the measuring devices in the assembly has a great possibility to create an effect on the overall mass flow rate. As a consequence, the device configuration has to be properly integrated to the assembly, which will reflectthe success or failure of the project. There are four air mass tlow rate measurement devices and they can be placed in series, parallel, or the combination of the two. Four potential configurations were selected for further evaluation after the process of generating various design concepts. The selection consists of two series configuration, a parallel configuration and a combination configuration. The details of each design are described below: { 4.1 Series Configuration with Sliding Track As shown below, the four airflow measurement devices are placed in series in the order of venturi, orifice,Pi tot tube, and rotameter.

i Vo.lves: Q Connectors:

Figure 7. Series Configuration with Sliding Tracks

The placement order is determined by the measuring requirement of each device. Since the critical venturi needs very high pressure to obtain sonic choked flow at the throat, it needs to be located in the first place, where no significant pressure drop has occurred. On the other hand, the rotameter is not capable of operating with a very high pressure. The possibility of rotameter damage requires the rotameter to be located at the end of the flow. The orifice and the pitot tube can be exchanged without affecting the accuracy of the measurement since no substantial pressure drop would occur for either of them. The discharge coefficient measurement device is placed on the branch from the main pipe because that it also needs high pressure to operate accurately. However, this type of device placement will not allow the discharge coefficient measurement device to obtain the ideal mass flow rate. If maintenance needs to be performed on a device, or if individual measurement is required, one or more devices could be easily separated. The connection between each device is I maintained with Snap-On fittings, and the remaining device(s) could then slide forward along the L track to be reconnected.

4.2 Series Configuration with Bypass Another series design configuration is illustrated in the following:

L

Orifice Plod:e Ven'turl

�------� i Vo.Lves

Q:9 Regulo tors

Figure 8. Series Configuration with ByPass

This concept is similar to the previous configuration, except that the locations of the devices are fixed. A U-shaped bypass pipe is placed over each device and additional valves are placed in order to reroute the flow. If maintenance needs to be performed on a device, or if individual measurement is required, flow could be directed around the specified device with the help of the valves. This same concept also applies to the discharge coefficient measurement device.

4.3 Series/Parallel Combined Configuration

Assuming that situations when service or certain device's measurement is required are seldom, series/parallel configurations can be combined ..

Ven-turi Roto.Me'ter

Pl tot Tube DC Device

i Valves

Figure Series Parallel Combination Configuration 9. I

As shown above, this configuration is very simple with devices in fixed locations. Rotameter is placed right after the critical venturi in order to take advantage of the high-pressure drop across it. The discharge coefficient measurement device is placed after the orifice and pitot tube for the same reason.

4.4 Parallel Configuration

Shown as the following, the parallel configuration is also very simple but each device operates independent of each other. As a general concept, this configuration allows a device to operate independently at one time. Since there are not any conflicts between devices, special arrangement is not needed when maintenance is required on one device. However, this type of placement will not allow the discharge coefficient measurement device to obtain the ideal mass flow ratemeas ured from other devices. R<>gulc..-tol�

• V o.. lves <29 Regulo. tors 0

Figure 10. Parallel Configuration

4.5 Decision Matrix

In order to choose the proper assembly configuration, a decision matrix is developed.

There are seven key issues that need to be considered for the assembly:

• Measurement Errors

• Space Required

• Ease of Maintenance

• Operations (Independent Overall) I

• Components Instrumentation I

• Human Interaction

• Time

· · ser•es-Shder ser�s-B yPass mbination ParaIIeI __ L_ __ __� ______L______L ______�·-______L ______Error 7 3 4 2 1 Space 5 1 2 3 4 Maintenance 3 3 1 2 4 Operations 4 2 4 1 3 Components 2 1 2 3 4 Interaction 6 1 4 3 2 Time 1 1 3 2 4 Total Score 52 34 40 51

Table 2. Decision Matrix

Based on the Decision Matrix, the chosen design is the series configuration with bypass. The compete detail of the proposed assembly configuration is described in Chapter 5. 5. Proposed Device Configuration Assembly

This section explains the final calculation perfom1ed to determine the main parameters and characteristics of each measurement device to be assembled. Moreover,. this section also presents the detail of the chosen device assembly configuration, which includes the head loss calculation and the minimum pipe entrance and exit requirements. The final design of the device assembly configuration was chosen to the main consideration factor of the overall space required to mount the total assembly on a 4' by 6' table. Moreover, the series setup of the device assembly configuration allows the flow to maintain a uniform mass flow rate throughout the pipe assembly. This will prevent having to adjust the pressure regulator before each measurement, such as in parallel setup configuration. In addition, the chosen device configuration allows a provision of being able to disassembly a device in the case that it needs maintenance or repair. The following two sections discuss in detail the calculation process of the devices and assembly configuration.

5.1 Device Calculation

This sub-section explains the calculation device of each measurement device to be used in the assembly system in the following order: critical venturi, orifice plate, rotameter, averaging [ pitot tube and discharge coefficientmeasurement device.

5.1.1 Critical Venturi

Based on equations explained previously in Chapter 3, the throat diameter of the critical venturi was determined with the aid of different graphs. Figure 11 provides the graph summary l of the critical venturi calculation, which results in the chosen critical venturi diameter of 0.1541 inches. Venturi Throat Diameter Calculation,

0 300

0.260 .j-.--,--.....,.;.-.,..--c-'-�,--c-'--_,,--.....,.;._,_-=.-,::;:...,._-=-�

�= o 2 40 r-.._-,..-,_.....,--_,....,-....-c:-_.,_ ...... ,7"c.,...?��---­

o 220 t.i t----"-.....,-...... :...-"--.,_...-"""--."'-:::::��- --:--·.�,..._::.c..--� r-Pi--::=-:--:::;--:-:-nh;d = 60 ps1g::ll 1f zooo H...;.-,'---"-.::.:>""':::...-,�:...... ---�""'-...... ;.;--'""'""�.._�""l - :: : : :� ::: � : : : : !: �, Pln!et ... QO ps1g i 0.180 -t 0 1 GO .j-.-._::;..-,:"'":: -":::..,--,.---,-��...... ,,-----'--,..,..---'· ,.,...,.....,-4

0 140 ��.,.--·-�...-..-:--�:...... ,.-,-�....,-,-,--��-�

Air Mass Flow Rete (lbm/s)

Figure Venturi Throat Diameter Calculation 11.

5.1.2. Orifice Plate

In order to use the appropriate mass flow rate, we use the pressure difference air correlation to determine the feasible air mass flow rate. Figure 12 below illustrates the graphs as the result of pressure difference calculation. addition, the graphs also provide an important In consideration to determine the bore diameter.

Orific e Bore D i• rneter C alculotio n

450,00

.400.00

350.00

300.00

Ic "'" -bete-ratto = 0.4 250.00 -bete-ratlo = o.s � beta-ratiO = 0.6 200.00 iSli -beta-ratio = 0.7

150.00 m�

100.00

50.00

0.00 0 ;;; � � � Air M� ••• � Flow Rote (Ibm/a) � � !

Figure Orifice Plate BoreDiameter Calculation 12. 5.1.3 Averaging Pitot Tube and Rotameter

The chosen air mass flow rate also determined by averaging pitot tube and rotameter is

calculation as illustrated in Figure 13 and 14 below.

�------·------,

Averaging Pitot Tube Calculation

8.000

...... 7.000 Cl iJj 6.000 .8:G) u c: 5.000 --Pinlet = 60 psig G) � 4.000 ·-- Pinlel = 70 psig 0E Pinlel = 80 psig 3.000 ..G) ::J (I) (I) 2.000 G) ... c.. 1.000

0.000

0 �0 �0 0� �0 80 �0 �0 �0 Air Mass Flow Rate (lbm/s) �------�

Figure 13. Averaging Pitot Tube Calculation

Rotameter Calculation

:: m 90�----�--�------�--�--� ��--�----· a: 80 ������ -���������������� �

0;: � +-�--��--- ����--����.��������� � 60 .g J5 50 +-���--�- ������--����. ������� � � 40 +-��������������;��������� 30 ������������ �������� E- � 20+-��� ,������������4�������� � 10 +-���--�-----�--�------�--�--�----4 �.... 0 +-����- ����������������� � 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10

AirMa ss Flow Rate (Ibm's)

Figure 14. Rotameter Calculation 6. Data Acquisition Sy stem

To proceed an expeliment with the finished assembly, conventional pressure and temperature measurement devices, e.g., manometers and thermometers, could be used. With the modem industlial automated technology, however, the process could be simplified with a data acquisition system (DAS). In addition of being able to take measurement as conventional devices, DAS also has some advantage over the other. DAS is able to take the measurement in remote in potentially dangerous conditions, and to calculate the desired results in real time if required. With add on components such as "Active controls, DAS has the ability to tum the X'" lab setup into a entirely automated system. Furthermore, it is also a good learning expelience for our group members. Utilizing regular PCs, standard data acquisition systems consist of three parts: data collector, interface, and software. The data collector part collecting data from pressure transducers, thermocouples, and so on. These transducers convert the measured results like pressures and temperatures into very small voltages. Then the electlical signals pass through the interface into the PC after being conditioned. The software could then process the signals and based on each transducer's calibration curve to convert the electrical signals back to the desired pressure and temperature measurement. Figure 15 illustrates the data acquisition system setup for our project. Figure Data Acquisition System Setup 15. The DAQ system can be external or internal. External systems have the expansion ability, but relatively more expensive. Since our project only needs approximately eleven (11) pressure and eight (8) temperature measurements, two sixteen (16) channel analog input PCI DAQ boards should be sufficient fo r our purpose. For our project, we are planning to utilize the data acquisition hardware and it's compatible software-Lab Tech, available to use from previous lab experiments. With LabTech software, we could then process the collected data.

The (virtual instrument) generated within the software could then be used to calculate the VI desired result, i.e., the mass airflow rate. Figure 16 contains an illustration of the of the VI LabTech software. The output is also shown in Figure 17 where the measured pressure, temperature, and calculated results can be shown.

LABTECH AFMPIR..UF C NOTEBOOK Build-Time -

Figure 16. IDustration VI - LABTECH Realtime VISI'O scr9

Figure 17. Output of Lab Tech 7. Design Issues

7.1 Parts

There are many parts that are going to be used in the final design. However, the most

important parts are the devices that will be used. Each device also has many parts that

allow it to become part of the assembly. The parts used in the design are consolidated in the

list below:

• 1-Critical Venturi

• !-Rotameter

• 1-0rifice Plate

• !-Averaging Pitot Tube

• !-Discharge CoefficientMeasurement Device

• 1-Pressure Regulator

• 11-Ball Valves

• 12' of 1" diameter type-L copper tubing

• Union fittings for copper tubing

• 3-sets of flanges

• 1-6' by 4' table with a wooden top

Additional parts such as miscellaneous screws and bolts used for mounting will be

used on a need by need basis.

7.2 Tolerance

Tolerances are a major aspect of any design. The chosen design will require minimal tolerances. The main concern is that the system fits to the determined design constraints. The pipeline will have a tight tolerance such that each device must connect to each other, making

sure that air leaks are non-existent. The pipeline will be composed of type-L copper tubing, configured of an outer diameter of 1.125" and an inner diameter of 1.055", creating a wall thickness of 0.035". Tolerances will be ± 0.001" within the pipeline, in order to prevent the line from leaking.

7.3 Safety

Safety is one of the main factors in the design chosen by the team. Since the design involves human interaction, it must be as safe as possible. The chosen design meets most of these safety requirements. As an example, the design contains a pressure regulator that will prevent inexperienced users from damaging the devices with extensive high pressure, which will cause possible injuries. The chosen design is also equipped with a bypass system, which allows the users to bypass a device in the case that it does not function properly or there are problems with obtaining the measurement results. The bypass system consists of ball valves, allowing quick and immediate device shutoff, which is important in the case of device malfunctions. A laboratory manual will also be provided with the experimental setup designed herein (see Appendix E). This laboratory manual clearly explains how each device is used as well as proper maintenance for each device. A special chapter on Safety in the laboratory manual includes precautions that should be taken before performing the experiment It also includes step-by-step procedure for setting up the experiment. Specific instructions will also be included in the case of an emergency. As emergency precautions, a firstaid kit will supplied along with the table for any be laboratory accident related directly and indirectly to this laboratory setup. The first aid kit will provide immediate care for minor scrapes and bruises, more serious injuries will be directed to a physician's attention. Emergency telephone numbers for the university health center will be posted on the laboratory setup for quick access.

7.4 Bill of Materials

The Bill of Materials contains an extensive listing on each part the design contains (see Table 3). It contains the following information:

• Manufacturer • Item

• Unit

• Description

• Total Price

Table 3. Bill of Materials

Quantity Unit Item No. Description Manufacturer Price Total 1 Ea. N/A Critical Venturi Fox Valve $586.00 $586.00 1 Ea. CD-502 OrificePlate Crane Manufacturing $ 110.00 $ 110.00 1 Ea. N/A Averaging Pi tot Tube Midwest Instruments $72.00 $72.00 1 Ea. 805 1K33 Rotameter Dwyer $37.76 $37.76 12 Ft. 5175K64 L-type Copper Tubing Mc-Master Carr $23.64 $283.68 12 Ea. 2664K41 Ball Valves Mc-Master Carr $5.16 $ 61.92 1 Ea. 4959K5 Pressure Regulator Mc-Master Carr $ 76.55 $76.55 8 Ea. 31685K7 Pressure Transducers Omega $85.00 $680.00 8 Ea. 39095K24 Thermocouples Omega $ 31.71 $253.68 1 Ea. N/A Wooden Table Horacio' s Welding $0.00 $0.00 1 Ea. 5533Tl2 First Aid Kit Mc-Master Carr $27.87 $27.87 1 Ea. N/A LabTech Software Northeastern University $0.00 $0.00 1 Set N/A Venturi Flanges 1 Set N/A OrificePlate Flanges 1 Set N/A Pitot Tube Flanges

7.5 Cost Financial Issues I

The final cost of the product will include all parts and material listed in the bill of materials

(see Table 3 above). The bill of materials also includes all shipping and handling charges on all parts ordered from manufacturers. Labor will not be included due to the fact that the complete assembly of the experimental setup will be performed by the team members. Any additional labor will be provided by the Mechanical, Industrial and Manufacturing (MIME)Department of

Northeastern University and donated by Horacio's Welding and Sheet Metal Company. 7.6 Project Plan

The proposed plan for the project consisted of a series of prioritized events. These events were the basis for achieving success with the design. By conducting research, information became readily available on many current mass flow rate measurement technologies. By generating design concepts and through the aid of a decision matrix, a final design was chosen. Parts were then ordered and the assembly process began. Once the assembly process began, L the completed assembly was tested (as explained in detail in Testing section). When the testing activities have all been completed, the measurement data was compared to the theoretical data before deli very to the customer.

7.7 Testing Activities L Testing is an important aspect in validating a design in the industry. Currently in industry, many companies use an Applied Research department, which allows various testing to be conducted on the proposed design. The proposed design will go through a period of testing, providing a series of data used to validate the design. It also provides time to perform changes required before the proposed design is ready to be delivered to the customer. There are two types of testing to be performed on the assembly configuration of air mass flow rate measurement devices. The procedure for the tests are described in detail in the following sections: a) Pressure Test A pressure test is to be performed by connecting !the compressed air of pressure source to the laboratory setup. Once it is connected to the system, each measurement device will be tested to ensure that it functions properly with the correct value of desired mass flow rat<:�. A strategically placed pressure regulator is to be placed in the beginning of the pipeline to determine the correct inlet pressure to be supplied to the flow. In addition to ensuring the proper function of each measurement device, the pressure test will also provide testing for pressure drop calculations derived from theoretical data. b) Data Acquisition Test A Data Acquisition test needs to be perfom1ed in order to ensure that the pressure

transducers and thermocouples function properly. This test is started by placing each pressure transducer and thermocouple at desired measurement points, before turningthe system on and connecting the system to compressed air. The data obtained from the data acquisition system (LabTech software) will be compared to the theoretical data obtained from calculation. Performing this test will result in determining the accuracy of the pressure transducers and thermocouples used in the system.

7.8 Codes Compliance

Code compliance is an important major issue for any measurement system design. Each measurement device used in the measurement system must meet all the associated American Society for Mechanical Engineers (ASME) and American Society for Testing and Materials (ASTM). The specific standard codes for each device is described in the following: a) A critical venturi requires precise machining and must be in tight tolerances. Therefore, it must meet all ASTM and ASME codes. b) An orificepla te also requires precise machining. The bore of the orifice plate should be tapered in strict accordance to the American Petroleum Institute (API) chapter 14, Section 3; American Gas Association (AGA) Gas Measurement Committee Report No. 3; ASMEFluid Meters Committee Report; ISO; J[SA. c) An averaging pitot tube consists of four measurements activities which must also conform to the standard industrial codes. The pressure and temperature must be based on an ASTM A 3 grade A welded schedule 40 of carbon steel pipe; ASTM A 312 TP 316 welded schedule 40 of carbon steel pipe; ASTM A 105 C.S. flanges and compatible components; ASTM A 182-F316 flanges and compatible components. d) A rotameter must also comply to the industrial standards as suggested by ANSI-Z540.1 and IS0-10012-1. 8. Report Conclusion

The air mass flowrate measurement system was designed based on the main objective of providing undergraduate mechanical engineering students with a laboratory setup to be used to perform air mass flow rate measurement. The need for this design project arises from the fact that students only learn about air mass flow rate measurement from theoretical lecture. is It necessary for students to conduct the measurement through laboratory experiment, as air mass flow rate measurement is one of the daily activities performed by mechanical engineers in the industry. The air mass flow ratemeasurement system is mainly designed to operate four (4) off-the-shelf devices, allowing students to compare the measurement accuracy of different devices. The system must also be able to generate consistent mass flow rate throughout the whole system. After several brainstorming sessions to generate various device configuration concepts, a final assembly configuration design is proposed with the help of a decision matrix. The final assembly configuration design includes measurement devices of a critical venturi, an orifice plate, an averaging pitot tube and a rotameter. In addition, the design also provides a device to measure the discharge coefficient for different disk geometries. The devices are assembled in series configuration, allowing the system to have consistent mass flow rate throughout the pipeline. It is ensured that the assembly configuration meets the required industrial codes such as ASI\ffi and ASTM. The measurement data to be used to calculate the mass flow rate will be obtained from the LabTech software, which is connected to the assembly system to generate measurement data. Various testing and calculations were conducted on this design project, resulting in satisfying testing results. A laboratory manual is provided to ensure that the experiment is conducted properly. Appendix A. Venturi Calculation

1. Determining the required throat diameter to produce a sonic choked condition at throat Given: Inlet Pressure = 80 psig = 94 .. 7 psia Inlet Temperature = 70 °F = 530 °R Pipe Inside Dia.. = 1.055 inches Mass Flow Rate = 0.04 lbrnls

Calculation: 0.04x.J530 Use Equation (11): = 0.5215x94.7

= �hroai.... D = throat X F 1[ = 0.1541 in.

2. Determining the pressure drop of the flow from the venturi Calculation: _!_ 94.7x123 x32.174 Use Equation (5): = = = 0.482 lbrnlft3 1716x530*12 p RT

= = 0.04x 144 = Vmlet. __!!!_ 13 • 68 uS P�nlet 0.482xnx0.25xl.055 2 f-.. 1

= Vinler 13.68x12x0.0254 = Mach.mlet = . 0121 .4x 287 294.26 O ..JYRT .Ji X P;n». ratio at Mach # of 0.0121 = 0.9999

Use Equation (13): = 0.5283 �hroat P;nlet X �/P;nlet X 94.7x0.528 . p = � == 50 04 • p sia throat 0.9999

Pressure Drop = Pinlet - Pthroat = 94.7 - 50.0 = 44.7 psia Appendix B.

Orifice Calculation

Given:

Inlet Pressure: 80 psig = 94.7 psia.

Inlet Temperature: 70°F = 530°R

Mass Flow Rate: 0.04 lbm/s

�-ratio: 0.5

Bore Diameter: 0.528 inches

Calculation: 3 _!_== 14·7x32·174x12 3 Density at Std. Atm. Pressure: p = 0.075 lbrnlft 1716x530x12 = RT

2 4 2 Bore Area: Abare == 1CXD bore / = 1CX0.5282 x0.25 = 0.00152 ft

Use Equation (15):

0 2 m (1 - /l4) _____0._ 04_2_(_1 -_ 0_. _54_) _, = M = 2xpx A2 x32.174x144 2x0.075x0.001522 x32.174x144

= 0.939 psia

= 26.0 inH20. Appendix C.

Minimum Pipe Entrance Length

Given (from previous calculation): 3 = 0.482 lbrn!ft p

= 13.68 ft/s V

D = 1.055 inches. 7 2 = 3.74 X w- lbm s ft J..l I

Calculation: pVD 0.482x13.68x1.055 Re = = = 48 142 12x32.174x3.74x10-7 , f.1 r Minimum Pipe Length Entrance = Le

116 � = 4.4Dpipe Re = 4.4xl.055x48,142 := 28.0 inches Le Appendix n.

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