International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 06 | June 2019 www.irjet.net p-ISSN: 2395-0072 CFD Analysis of Flow through Integral Orifice Plate Assemblies under Diverse Working Conditions MANU B V1, Prof. YOGESH KUMAR2 K J and Dr. V. SESHADRI3 1M.Tech student, Department of Mechanical Engineering, Maharaja Institute of Technology, Mysore. 2Assistant Professor, Department of Mechanical Engineering, Maharaja Institute of Technology, Mysore. 3Professor (Emeritus), Department of Mechanical Engineering, Maharaja Institute of Technology, Mysore. ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract – The performance of characteristics of various for geometry and flow characteristics of integral orifice types of integral orifice plates for diverse working conditions meters but there is not much research work done or are analyzed using commercially available CFD software, information available on this type of orifice meters. ANSYS FLUENT. Several manufacturers like Yokogawa, Honeywell and others In this present work, ANSYS FLUENT software is used for the manufacture the integral orifice meters assemblies and they analysis of both compressible and incompressible flow have conducted the experiments on these particular orifice through the various types of integral orifice plates namely, meters and given the data for geometry and flow square edge, conical entrance and quarter circle integral characteristic for certain range of diameters and Reynolds orifice plate assemblies. numbers. But there is no computational validation for experimental results and there is no further information on The flow through the standard orifice plate is analyzed flow characteristics if orifice meters operate outside the according to BS 1042 and computational results are specified range of Reynolds number and diameters. validated with standard results. Hence this research work is an attempt to simulate the flow The experimental results given by MARCELO FILARDI et through the integral orifice meter which operates outside al[5] and by Yokogawa electronic corporation[10] are the specified conditions, that is under diverse conditions. validated by using ANSYS FLUENT and same computational methodology is used to study the variation of co-efficient of The computational fluid dynamics (CFD) ANALYSIS FLUENT discharge (Cd) and permanent pressure loss co-efficient (CL) is used as a tool for modeling and analysis of integral orifice with Reynolds number, diameter ratio and effect of absence meters. Initially the simulation is carried out according BS of upstream and downstream pipelines. 1042 and ISO 5167 standards and results are validated with the standards. Further the analysis is carried out for The compressible flow through standard orifice plate is nonstandard conditions of Reynolds numbers and diameter validated with CFD and same methodology is used to predict ratio for both compressible and incompressible flows for the variation of expansibility factor with Reynolds number integral orifices and studying the effects of these parameters for the various types of integral orifice plate assemblies. on coefficient of discharge, permanent pressure loss coefficient and expansibility coefficient. Key Words: Co-efficient of discharge (Cd), Permanent pressure loss (CL), CFD, ANSYS FLUENT, Integral orifice 1.1 OPERATING PRINCIPLE OF ORIFICE METER plates, Reynolds number, Expansibility factor, Diameter ratio. With an orifice plate installed in a flow stream, increases in a fluid flow velocity through the reduced area of the orifice, 1. INTRODUCTION develop a differential pressure across the orifice. The differential pressure generated is related to the diameter Orifice meter is an obstruction type of flow meter, which is ratio of the orifice plate. The smaller beta ratio causes the widely used for flow measurement in most of the industries higher the differential pressure to be generated. In practice like food, chemical, water supply Industries etc. BS 1042 and the choice of beta ratio is a compromise between the ISO 5167 standards provide the coefficient of discharge for differential pressure desired and the flow rate required. certain range of diameter ratios and Reynolds numbers. But in case of specialized industrial applications the orifice meter With the orifice plate in the pipe work, the static pressure operates at diverse conditions, that are outside the standard upstream the plate increases slightly due to back pressure diameter and Reynolds number ranges. effect and then decreases sharply as the flow passes through the orifice. Flow downstream the orifice reaches minimum at The integral orifice meters are special type of obstruction a point called the Vena contracta where the velocity of the type flow meters, which are used for small diameters and flow is at a maximum. Beyond Vena contracta, static low flows. BS 1042 standard also provides the specifications pressure start to recover but it never gets to the upstream © 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 1699 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 06 | June 2019 www.irjet.net p-ISSN: 2395-0072 value. In other words, with an orifice meter installation, QActual = Cd QTheoritical =Cd there is always a permanent pressure loss. In addition to pressure loss, some of the pressure energy is converted into sound and heat at an orifice plate. for compressible flows. When a fluid (whether liquid or gas) passes through the Cd is defined as the ratio of the actual flow to the ideal flows orifice, its pressure builds up slightly upstream of the and is always less than one. orifice but as the fluid is forced to converge to pass through the hole, the velocity increases and the fluid pressure When the orifice meter is operating at elevated decreases. A little downstream of the orifice the flow reaches temperatures, an area correction factor Fα needs to be its point of maximum convergence, the vena-contracta, included to account for the change in the area of the orifice where the velocity reaches its maximum and the pressure hole due to thermal expansion. reaches its minimum. Beyond that, the flow expands, the velocity falls and the pressure increases. By measuring the When the fluid is compressible an additional factor ε the difference in fluid pressure across tappings upstream and expansibility coefficient needs to be introduced which takes downstream of the plate, the flow rate can be obtained from account of the difference between the discharge co-efficient Bernoulli's equation for compressible and incompressible flows. It is given by, Fig1. represents the flow of fluid through orifice meter and ε = let us consider section 1-1 at the upstream of the pipe and section 2-2 at the downstream where the pressure are to be Where noted . Let P1, V1 and A1 are the pressure, velocity and the cross-sectional area of the pipeline at section 1-1 Cdc is discharge co-efficient for compressible flow. Cdi is discharge co-efficient for incompressible flow. respectively and P2, V2 and A2 are the pressure, velocity and the cross sectional area of the pipe line, at section 2-2 respectively. Calculation of Cd can be done using the formula specified in ISO-5167. The discharge coefficient is given by the Reader- The expression for theoretical flow rate is given by, Harries/Gallagher equation given by, 2 8 6 Cd = 0.5961 + 0.0261β – 0.216β + 0.000521[10 β/ReD] + 3.5 5 -10L QTheoretical = = [0.0188 + 0.0063A]β [10 /ReD] + [0.043 + 0.080 e 1 – -7L 1.1 1.3 0.123e 1][1 – 0.11A][ – 0.031[M2 – 0.08M2 ]β If D <71.12mm (2.8 inch), the following term should be added to the equation. + 0.011[0.075 –β][ 2.8 - ] Where D is the diameter of pipe in mm Diameter ratio, β = d/D ReD = Pipe Reynolds number 0.8 A = [19000β/ReD] Fig1: FLOW THROUGH THE ORIFICE METER M2 = Constant = 2L2 / (1-β) 1.2 DISCHARGE COEFFICIENT OF ORIFICE PLATE L1 and L2 are distance from upstream and downstream The flow expression obtained in the above equation is not depending on the type of pressure tappings used. accurate in the actual case and some correction factor, such as discharge coefficient (Cd) has to be incorporated. Thus the The above equation has its own limitations. The equation is equation becomes, completely empirical and is derived on the basis of extensive experimental data. It is only applicable when pipe diameter QActual = Cd QTheoritical =Cd is within 50mm<D<1000mm when diameter ratio is within 0.1<β<0.75, plate thickness between 0.005D and 0.002D, bevel angle of 45°±15°.The upstream edge of the orifice hole for incompressible flows. © 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 1700 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 06 | June 2019 www.irjet.net p-ISSN: 2395-0072 should be sharp and a radius of curvature not greater than loss caused by the orifice meter may be determined by the 0.0004d. Further the pipe surface should be smooth. pressure measurements made with the same pipe line before and after the insertion of the orifice meter as well as the The geometry and dimensions should be as per ISO 5167 pressure differential indicated by the flow meter. standards for the equation to be applicable. For any other non-standard cases lying outside of the mentioned range, the If ΔP` is the difference in pressure, measured prior to the Reader-Harries/Gallagher Equation is invalid. installation of the orifice plate between two pressure tappings one of which is situated far upstream of the flanges Discharge coefficient depends on Reynolds number and where the orifice will be inserted and the other which is far 4 diameter ratio, β. But it has been observed that for Re>10 , downstream of the same flanges and if ΔP`` is the difference the flow is totally turbulent and Discharge coefficient is fairly in the pressure measured between the same pressure independent for Reynolds number.