Cooling of Electronic Equipment Vary Widely, Depending on the Particular Application

Total Page:16

File Type:pdf, Size:1020Kb

Cooling of Electronic Equipment Vary Widely, Depending on the Particular Application cen58933_ch15.qxd 9/9/2002 10:20 AM Page 785 CHAPTER COOLING OF ELECTRONIC 15 EQUIPMENT lectronic equipment has made its way into practically every aspect of modern life, from toys and appliances to high-power computers. The re- CONTENTS Eliability of the electronics of a system is a major factor in the overall re- 15–1 Introduction and liability of the system. Electronic components depend on the passage of History 786 electric current to perform their duties, and they become potential sites for ex- 15–2 Manufacturing of Electronic Equipment 787 cessive heating, since the current flow through a resistance is accompanied by heat generation. Continued miniaturization of electronic systems has resulted 15–3 Cooling Load of Electronic Equipment 793 in a dramatic increase in the amount of heat generated per unit volume, com- 15–4 Thermal Environment 794 parable in magnitude to those encountered at nuclear reactors and the surface of the sun. Unless properly designed and controlled, high rates of heat gener- 15–5 Electronics Cooling in Different Applications 795 ation result in high operating temperatures for electronic equipment, which 15–6 Conduction Cooling 797 jeopardizes its safety and reliability. The failure rate of electronic equipment increases exponentially with 15–7 Air Cooling: Natural Convection and Radiation 812 temperature. Also, the high thermal stresses in the solder joints of electronic 15–8 Air Cooling: Forced components mounted on circuit boards resulting from temperature variations Convection 820 are major causes of failure. Therefore, thermal control has become increas- 15–9 Liquid Cooling 833 ingly important in the design and operation of electronic equipment. 15–10 Immersion Cooling 836 In this chapter, we discuss several cooling techniques commonly used in electronic equipment such as conduction cooling, natural convection and radiation cooling, forced-air cooling, liquid cooling, and immersion cooling. This chapter is intended to familiarize the reader with these techniques and put them into perspective. The reader interested in an in-depth coverage of any of these topics can consult numerous other sources available, such as those listed in the references. 785 cen58933_ch15.qxd 9/9/2002 10:20 AM Page 786 786 HEAT TRANSFER 15–1I INTRODUCTION AND HISTORY The field of electronics deals with the construction and utilization of devices that involve current flow through a vacuum, a gas, or a semiconductor. This exciting field of science and engineering dates back to 1883, when Thomas Edison invented the vacuum diode. The vacuum tube served as the foun- dation of the electronics industry until the 1950s, and played a central role in the development of radio, TV, radar, and the digital computer. Of the several computers developed in this era, the largest and best known is the ENIAC (Electronic Numerical Integrator and Computer), which was built at the Uni- versity of Pennsylvania in 1946. It had over 18,000 vacuum tubes and occu- pied a room 7 m ϫ 14 m in size. It consumed a large amount of power, and its reliability was poor because of the high failure rate of the vacuum tubes. The invention of the bipolar transistor in 1948 marked the beginning of a new era in the electronics industry and the obsolescence of vacuum tube tech- nology. Transistor circuits performed the functions of the vacuum tubes with greater reliability, while occupying negligible space and consuming negligible power compared with vacuum tubes. The first transistors were made from ger- manium, which could not function properly at temperatures above 100°C. Soon they were replaced by silicon transistors, which could operate at much higher temperatures. The next turning point in electronics occurred in 1959 with the introduction of the integrated circuits (IC), where several components such as diodes, transistors, resistors, and capacitors are placed in a single chip. The number of 1010 GSI components packed in a single chip has been increasing steadily since then at an amazing rate, as shown in Figure 15–1. The continued miniaturization of 9 10 electronic components has resulted in medium-scale integration (MSI) in the 1960s with 50–1000 components per chip, large-scale integration (LSI) in 8 10 ULSI the 1970s with 1000–100,000 components per chip, and very large-scale inte- gration (VLSI) in the 1980s with 100,000–10,000,000 components per chip. 7 10 Today it is not unusual to have a chip 3 cm ϫ 3 cm in size with several mil- 6 lion components on it. 10 VLSI The development of the microprocessor in the early 1970s by the Intel Corporation marked yet another beginning in the electronics industry. The ac- 105 companying rapid development of large-capacity memory chips in this decade made it possible to introduce capable personal computers for use at work or at 104 VLSI Components per chip home at an affordable price. Electronics has made its way into practically everything from watches to household appliances to automobiles. Today it is 103 difficult to imagine a new product that does not involve any electronic parts. The current flow through a resistance is always accompanied by heat 102 MSI generation in the amount of I 2R, where I is the electric current and R is the SSI 101 resistance. When the transistor was first introduced, it was touted in the news- papers as a device that “produces no heat.” This certainly was a fair statement, 100 considering the huge amount of heat generated by vacuum tubes. Obviously, 1960 1970 1980 1990 2000 the little heat generated in the transistor was no match to that generated in its Year predecessor. But when thousands or even millions of such components are FIGURE 15–1 packed in a small volume, the heat generated increases to such high levels that The increase in the number of its removal becomes a formidable task and a major concern for the safety and components packed on a chip over reliability of the electronic devices. The heat fluxes encountered in electronic the years. devices range from less than 1 W/cm2 to more than 100 W/cm2. cen58933_ch15.qxd 9/9/2002 10:20 AM Page 787 787 CHAPTER 15 Heat is generated in a resistive element for as long as current continues to flow through it. This creates a heat build-up and a subsequent temperature rise at and around the component. The temperature of the component will continue rising until the component is destroyed unless heat is transferred away from it. The temperature of the component will remain constant when the rate of heat removal from it equals the rate of heat generation. Individual electronic components have no moving parts, and thus nothing to wear out with time. Therefore, they are inherently reliable, and it seems as if they can operate safely for many years. Indeed, this would be the case if com- ponents operated at room temperature. But electronic components are ob- served to fail under prolonged use at high temperatures. Possible causes of failure are diffusion in semiconductor materials, chemical reactions, and creep in the bonding materials, among other things. The failure rate of electronic de- vices increases almost exponentially with the operating temperature, as shown in Figure 15–2. The cooler the electronic device operates, the more reliable it 10 failure rate at T is. A rule of thumb is that the failure rate of electronic components is halved 9 f = —–—————— T failure rate at 75°C for each 10°C reduction in their junction temperature. 8 T f 7 15–2I MANUFACTURING OF ELECTRONIC 6 5 EQUIPMENT 4 Failure factor factor Failure The narrow band where two different regions of a semiconductor (such as the 3 p-type and n-type regions) come in contact is called a junction. A transistor, 2 for example, involves two such junctions, and a diode, which is the simplest 1 0 semiconductor device, is based on a single p-n junction. In heat transfer analy- 20 40 60 80 100 120 140 sis, the circuitry of an electronic component through which electrons flow 75 and thus heat is generated is also referred to as the junction. That is, junctions Temperature, °C are the sites of heat generation and thus the hottest spots in a component. In FIGURE 15–2 silicon-based semiconductor devices, the junction temperature is limited to The increase in the failure rate of 125°C for safe operation. However, lower junction temperatures are desirable bipolar digital devices with for extended life and lower maintenance costs. In a typical application, nu- temperature (from Ref. 15). merous electronic components, some smaller than 1 ␮m in size, are formed from a silicon wafer into a chip. The Chip Carrier The chip is housed in a chip carrier or substrate made of ceramic, plastic, or glass in order to protect its delicate circuitry from the detrimental effects of the environment. The chip carrier provides a rugged housing for the safe han- dling of the chip during the manufacturing process, as well as the connectors between the chip and the circuit board. The various components of the chip carrier are shown in Figure 15–3. The chip is secured in the carrier by bond- Lid Bond wires ing it to the bottom surface. The thermal expansion coefficient of the plastic Case is about 20 times that of silicon. Therefore, bonding the silicon chip directly Leads to the plastic case would result in such large thermal stresses that the reliabil- Chip ity would be seriously jeopardized. To avoid this problem, a lead frame made of a copper alloy with a thermal expansion coefficient close to that of silicon Lead frame Bond Pins is used as the bonding surface.
Recommended publications
  • Heat Transfer Model of a Rotary Compressor S
    Purdue University Purdue e-Pubs International Compressor Engineering Conference School of Mechanical Engineering 1992 Heat Transfer Model of a Rotary Compressor S. K. Padhy General Electric Company Follow this and additional works at: https://docs.lib.purdue.edu/icec Padhy, S. K., "Heat Transfer Model of a Rotary Compressor" (1992). International Compressor Engineering Conference. Paper 935. https://docs.lib.purdue.edu/icec/935 This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/ Herrick/Events/orderlit.html HEAT TRANSFER MODEL OF A ROTARY COMPRESSOR Sisir K. Padhy General Electric C_ompany Appliance Park 5-2North, Louisville, KY 40225 ABSTRACT Energy improvements for a rotary compressor can be achieved in several ways such as: reduction of various electrical and mechanical losses, reduction of gas leakage, better lubrication, better surface cooling, reduction of suction gas heating and by improving other parameters. To have a ' better understanding analytical/numerical analysis is needed. Although various mechanical models are presented to understand the mechanical losses, dynamics, thermodynamics etc.; little work has been done to understand the compressor from a heat uansfer stand point In this paper a lumped heat transfer model for the rotary compressor is described. Various heat sources and heat sinks are analyzed and the temperature profile of the compressor is generated. A good agreement is found between theoretical and experimental results. NOMENCLATURE D, inner diameter D.
    [Show full text]
  • Investigation of Compressor Heat Dispersion Model Da Shi Shanghai Hitachi Electronic Appliances, China, People's Republic Of, [email protected]
    Purdue University Purdue e-Pubs International Compressor Engineering Conference School of Mechanical Engineering 2014 Investigation Of Compressor Heat Dispersion Model Da Shi Shanghai Hitachi Electronic Appliances, China, People's Republic of, [email protected] Hong Tao Shanghai Hitachi Electronic Appliances, China, People's Republic of, [email protected] Min Yang Shanghai Hitachi Electronic Appliances, China, People's Republic of, [email protected] Follow this and additional works at: https://docs.lib.purdue.edu/icec Shi, Da; Tao, Hong; and Yang, Min, "Investigation Of Compressor Heat Dispersion Model" (2014). International Compressor Engineering Conference. Paper 2314. https://docs.lib.purdue.edu/icec/2314 This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/ Herrick/Events/orderlit.html 1336, Page 1 Investigation of Rotary Compressor Heat Dissipation Model Da SHI 1, Hong TAO2, Min YANG 3* 1SHEC, R&D Centre, Shanghai, China Contact Information (+8621-13564483789, [email protected]) 2SHEC, R&D Centre, Shanghai, China Contact Information (+8621-13501728323,[email protected]) 3SHEC, R&D Centre, Shanghai, China Contact Information (+8621-15900963244, [email protected]) * Corresponding Author ABSTRACT This paper presented a model of rotary compressor heat dissipation, which can be used to calculate heat dissipation under forced-convective/natural-convective and heat radiation mode respectively. The comparison, between calculated and experimental result for both constant speed compressor and variable speed one, shows that the average heat dissipation error is below 20% and discharge temperature deflection is less than 4 ℃。 1.
    [Show full text]
  • Convective Heat Transfer Coefficient for Indoor Forced Convection Drying of Corn Kernels
    Int. J. Mech. Eng. & Rob. Res. 2013 Ravinder Kumar Sahdev et al., 2013 ISSN 2278 – 0149 www.ijmerr.com Vol. 2, No. 4, October 2013 © 2013 IJMERR. All Rights Reserved Research Paper CONVECTIVE HEAT TRANSFER COEFFICIENT FOR INDOOR FORCED CONVECTION DRYING OF CORN KERNELS Ravinder Kumar Sahdev1*, Chinu Rathi Saroha1 and Mahesh Kumar2 *Corresponding Author: Ravinder Kumar Sahdev, [email protected] In this present research paper, an attempt has been made to determine the convective heat transfer coefficient of corn kernels under indoor forced convection drying mode. The experiments were conducted in the month of May 2013 in the climatic conditions of Rohtak (28° 40': 29 05'N 76° 13': 76° 51'E). Corn kernels were dried from initial moisture content 43% dry-basis. Experimental data was used to evaluate the values of constants (C and n) in Nusselt number expression by using linear regression analysis and consequently convective heat transfer coefficient was determined. The convective heat transfer coefficient for corn kernels was found to be 1.04 W/m2 °C. The experimental error in terms of percent uncertainty has also been calculated. Keywords: Corn kernels, Convective heat transfer coefficient, Indoor forced convection drying INTRODUCTION the interior of the corn kernels takes place due Corn is one of the main agricultural products to induced vapor pressure difference between in many countries. It is an important industrial the corn kernels and surrounding medium. raw material in the starch industry (Haros and The convective heat transfer coefficient is Surez, 1997; and Soponronnarit et al., 1997a). an important parameter in drying rate It is also a grain that can be eaten raw off the simulation since the temperature difference cob.
    [Show full text]
  • Heat Transfer in Flat-Plate Solar Air-Heating Collectors
    Advanced Computational Methods in Heat Transfer VI, C.A. Brebbia & B. Sunden (Editors) © 2000 WIT Press, www.witpress.com, ISBN 1-85312-818-X Heat transfer in flat-plate solar air-heating collectors Y. Nassar & E. Sergievsky Abstract All energy systems involve processes of heat transfer. Solar energy is obviously a field where heat transfer plays crucial role. Solar collector represents a heat exchanger, in which receive solar radiation, transform it to heat and transfer this heat to the working fluid in the collector's channel The radiation and convection heat transfer processes inside the collectors depend on the temperatures of the collector components and on the hydrodynamic characteristics of the working fluid. Economically, solar energy systems are at best marginal in most cases. In order to realize the potential of solar energy, a combination of better design and performance and of environmental considerations would be necessary. This paper describes the thermal behavior of several types of flat-plate solar air-heating collectors. 1 Introduction Nowadays the problem of utilization of solar energy is very important. By economic estimations, for the regions of annual incident solar radiation not less than 4300 MJ/m^ pear a year (i.e. lower 60 latitude), it will be possible to cover - by using an effective flat-plate solar collector- up to 25% energy demand in hot water supply systems and up to 75% in space heating systems. Solar collector is the main element of any thermal solar system. Besides of large number of scientific publications, on the problem of solar energy utilization, for today there is no common satisfactory technique to evaluate the thermal behaviors of solar systems, especially the local characteristics of the solar collector.
    [Show full text]
  • Forced and Natural Convection
    FORCED AND NATURAL CONVECTION Forced and natural convection ...................................................................................................................... 1 Curved boundary layers, and flow detachment ......................................................................................... 1 Forced flow around bodies .................................................................................................................... 3 Forced flow around a cylinder .............................................................................................................. 3 Forced flow around tube banks ............................................................................................................. 5 Forced flow around a sphere ................................................................................................................. 6 Pipe flow ................................................................................................................................................... 7 Entrance region ..................................................................................................................................... 7 Fully developed laminar flow ............................................................................................................... 8 Fully developed turbulent flow ........................................................................................................... 10 Reynolds analogy and Colburn-Chilton's analogy between friction and heat
    [Show full text]
  • Forced Convection Heat Transfer Convection Is the Mechanism of Heat Transfer Through a Fluid in the Presence of Bulk Fluid Motion
    Forced Convection Heat Transfer Convection is the mechanism of heat transfer through a fluid in the presence of bulk fluid motion. Convection is classified as natural (or free) and forced convection depending on how the fluid motion is initiated. In natural convection, any fluid motion is caused by natural means such as the buoyancy effect, i.e. the rise of warmer fluid and fall the cooler fluid. Whereas in forced convection, the fluid is forced to flow over a surface or in a tube by external means such as a pump or fan. Mechanism of Forced Convection Convection heat transfer is complicated since it involves fluid motion as well as heat conduction. The fluid motion enhances heat transfer (the higher the velocity the higher the heat transfer rate). The rate of convection heat transfer is expressed by Newton’s law of cooling: q hT T W / m 2 conv s Qconv hATs T W The convective heat transfer coefficient h strongly depends on the fluid properties and roughness of the solid surface, and the type of the fluid flow (laminar or turbulent). V∞ V∞ T∞ Zero velocity Qconv at the surface. Qcond Solid hot surface, Ts Fig. 1: Forced convection. It is assumed that the velocity of the fluid is zero at the wall, this assumption is called no‐ slip condition. As a result, the heat transfer from the solid surface to the fluid layer adjacent to the surface is by pure conduction, since the fluid is motionless. Thus, M. Bahrami ENSC 388 (F09) Forced Convection Heat Transfer 1 T T k fluid y qconv qcond k fluid y0 2 y h W / m .K y0 T T s qconv hTs T The convection heat transfer coefficient, in general, varies along the flow direction.
    [Show full text]
  • 4. Forced Convection Heat Transfer
    Page 4.1 4. Forced Convection Heat Transfer 4.1 Fundamental Aspects of Viscous Fluid Motion and Boundary Layer Motion 4.1.1 Viscosity 4.1.2 Fluid Conservation Equations - Laminar Flow 4.1.3 Fluid Conservation Equations - Turbulent Flow 4.2 The Concept pf Boundary Layer 4.2.1 Laminar Boundary Layer 4.2.1.1 Conservation Equations - Local Formulation 4.2.1.2 Conservation Equations -Integral Formulation 4.2.2 Turbulent Boundary Layer 4.3 Forced Convection Over a Flat Plate 4.3.1 laminar Boundary Layer 4.3.1.1 Velocity Boundary Layer - Friction Coefficient 4.3.1.2 Thermal Boundary Layer - Heat Transfer Coefficient 4.3.2 Turbulent Flow 4.3.2.1 Velocity Boundary Layer - Friction Coefficient 4.3.2.2 Heat Transfer in the Turbulent Boundary Layer 4.4 Forced Convection In Ducts 4.4.1 laminar Flow 4.4.1.1 Velocity Distribution and Friction Factor In Laminar Flow 4.4.1.2 Bulk Temperature 4.4.1.3 Heat Transfer in Fully Developed Laminar Flow 4.4.2 Turbulent 4.4.2.1 Velocity Distribution and Friction Factor 4.4.2.2 Heat Transfer In Fully Developed Turbulent Flow 4.4.2.3 Non- Circular Tubes Page 4.2 4. Forced Convection Heat Transfer In Chapter 3, we have discussed the problems of heat conduction and used the convection as one of the boundary conditions that can be applied to the surface of a conducting solid. We also assumed that the heat transfer rate from the solid surface was given by Newton's law of cooling: =h,A~w-tJ q" 4.1 In the above application, he' the convection heat transfer coefficient has been supposed known.
    [Show full text]
  • Experimental Studies on Natural and Forced Convection Around Spherical and Mushroom Shaped Particles
    EXPERIMENTAL STUDIES ON NATURAL AND FORCED CONVECTION AROUND SPHERICAL AND MUSHROOM SHAPED PARTICLES. A Thesis Presented in Partial Fulfillment of the Requirements for the degree Master of Science in the Graduate School of The Ohio State University by Abdullah M. Alhaxsdan ***** The Ohio State University 1989 Master's Examination Committeet Approved by Dr. Sudhir Sastry Dr. Harold Keener Dr. Santi Bhowmik ' Adviser Department of Agricultural Engineering ACKNOWLEDGEMENTS I would like to acknowledge the guidence and support of Dr. Sudhir Sastry, advisor, and my thesis committee, Dr. Santi Bhowmik, and Dr. Harold Keener in guiding me for the research of this thesis. In addition, I appreciate my previous advisor Professor John Blaisdell, who is now retired, in supporting and helping me start this thesis. Thanks also to Mr. Dusty Bauman and Mr. Brian Heskitt for their help in lab work. A special thanks to my wife , Jwaher, in supporting me and her patience with me. My daughter, Rehab, also is a great delight during the work in this thesis. ii THESIS ABSTRACT THE OHIO STATE UNIVERSITY GRADUATE SCHOOL NAME: ALHAMDAN, ABDULLAH M. QUARTER/YEAR: SUMMER/1989 DEPARTMENT: AGRICULTURAL ENGINEERING DEGREE: M.S. ADVISOR«S NAME: SASTRY, SUDHIR K. TITLE OP THESIS: EXPERIMENTAL STUDIES ON NATURAL AND FORCED CONVECTION AROUND SPHERICAL AND MUSHROOM SHAPED PARTICLES. Heat transfer coefficients (h) between fluids and particles were determined for three situations: the first two involving natural convection of a mushroom-shaped particle immersed in Newtonian and non-Newtonian liquids, and the third involving continuous flow of a sphere within liquid in a tube. For natural convection studies, h was much higher for heating than for cooling, and decreased with time as equilibration occurred.
    [Show full text]
  • Effect of Buoyancy on Forced Convection Heat Trans­
    AE-176 UDC 536.25 o K lu Effect of Buoyancy on Forced Convection < Heat Transfer in Vertical Channels — a Literature Survey A. Bhattacharyya AKTIEBOLAGET ATOMENERGI STOCKHOLM, SWEDEN 1965 AE-176 EFFECT OF BUOYANCY ON FORCED CONVECTION HEAT TRANS­ FER IN VERTICAL CHANNELS - A LITERATURE SURVEY Ajay Bhattacharyya Abstract This report contains a short resume of the available informa ­ tion from various sources on the effect of free convection flow on forced convection heat transfer in vertical channels. Both theoretical and experimental investigations are included. Nearly all of the theo­ retical investigations are concerned with laminar flow with or with­ out internal heat generation. More consistent data are available for upward flow than for downward flow. Curves are presented to deter ­ mine whether free convection or forced convection mode of heat trans­ fer is predominant for a particular Reynolds number and Rayleigh 5 . number. At Re^ > 10 free convection effects are negligible. Downward flow through a heated channel at low Reynolds num ­ ber is unstable. Under similar conditions the overall heat transfer coefficient for downward flow tends to be higher than that for upward flow. (This report forms a part of the thesis to be submitted to the Royal Institute of Technology, Stockholm, in partial fulfillment of the re­ quirements for the degree of Teknologie Licentiat. ) Printed and distributed in March 1965 LIST OF CONTENTS Page Abstract 1 I. Introduction 3 II. Theoretical investigations 3 II. 1 Laminar flow 3 II. 2 Turbulent flow 4 III. Experimental investigations 5 III. 1 Laminar flow 5 III. 2 Turbulent flow 8 IV.
    [Show full text]
  • Comparative Evaluation of Radiant and Forced Convection Heaters in Grow-Finish Swine Rooms
    The Canadian Society for Bioengineering La Société Canadienne de Génie The Canadian society for engineering in agricultural, food, Agroalimentaire et de Bioingénierie environmental, and biological systems. La société canadienne de génie agroalimentaire, de la bioingénierie et de l’environnement Paper No. CSBE11-408 Comparative Evaluation of Radiant and Forced Convection Heaters in Grow-Finish Swine Rooms Bernardo Predicala Prairie Swine Centre Inc., Saskatoon, SK; [email protected] Leila Dominguez Prairie Swine Centre Inc. / Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, SK; [email protected] Alvin Alvarado Prairie Swine Centre Inc. / Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, SK; [email protected] Jason Price Alberta Agriculture and Rural Development, Edmonton, Alberta; [email protected] Yaomin Jin Prairie Swine Centre Inc., Saskatoon, SK; [email protected] Written for presentation at the CSBE/SCGAB 2011 Annual Conference Inn at the Forks, Winnipeg, Manitoba 10-13 July 2011 ABSTRACT In cold climate production locations, space heating represents a significant proportion of total energy use in a hog production barn. The use of gas-fired infrared heating system presents a possible alternative for space heating in barns. In this work, an infrared radiant heater was compared with a conventional forced-convection heater by installing them separately in two identical 100-head grow-finish rooms and operating the heaters to maintain similar thermal environments in the two rooms. The energy consumption (natural gas and electricity), animal performance (ADG and ADFI), and air quality were monitored in both rooms. Results from three completed trials showed that the room with infrared radiant heating system consumed more natural gas but less electrical energy compared to the room with forced-air convection heater.
    [Show full text]
  • Convective Heat Transfer Coefficient for Indoor Forced Convection Drying of Vermicelli
    IOSR Journal of Engineering June. 2012, Vol. 2(6) pp: 1282-1290 Convective heat transfer coefficient for indoor forced convection drying of vermicelli Ravinder Kumar Sahdev1, Nitesh Jain1 and Mahesh kumar2 1(Department of Mechanical Engineering, University Institute of Engineering & Technology, Maharshi Dayanand University, Rohtak, India) 1(Department of Mechanical Engineering, University Institute of Engineering & Technology, Maharshi Dayanand University, Rohtak, India) 2(Department of Mechanical Engineering, Guru Jambheshwar University of Sciences & Technology, Hisar, India) ABSTRACT In this present research paper, an attempt has been made to determine the convective heat transfer coefficient of vermicelli under indoor forced convection drying mode. The experiments were conducted in the month of March 2012 in the climatic conditions of Rohtak (28o 40’: 29 05’N 76o 13’: 76o 51’E). Experimental data was used to evaluate the values of constants (C and n) in Nusselt number expression by using linear regression analysis and consequently convective heat transfer coefficients were determined. The convective heat transfer coefficient values for vermicelli were found to vary from 0.98 to 1.10 W/m2 oC. The experimental error in terms of percent uncertainty has also been calculated. Keywords: - Convective heat transfer coefficient, Indoor forced convection drying, Vermicelli. NOMENCLATURE 2 At area of rectangular wire mesh tray, m C constant o C v specific heat of humid air, J/kg C 2 o hc convective heat transfer coefficient, W/m C 2 o hc,av average
    [Show full text]
  • Cooling on Photovoltaic Panel Using Forced Air Convection Induced by DC Fan
    International Journal of Electrical and Computer Engineering (IJECE) Vol. 6, No. 2, April 2016, pp. 526~534 ISSN: 2088-8708, DOI: 10.11591/ijece.v6i2.9118 526 Cooling on Photovoltaic Panel Using Forced Air Convection Induced by DC Fan A.R. Amelia*, Y.M. Irwan*, M. Irwanto*,W.Z. Leow*, N. Gomesh*, I. Safwati**, M.A.M. Anuar*** *Centre of Excellence for Renewable Energy, School of Electrical System Engineering, University Malaysia Perlis (UniMAP), Malaysia **Institute of Engineering Mathematics, University Malaysia Perlis, (UniMAP), Malaysia ***Faculty of Electrical & Automotion Engineering Technology Tati University Collage (TATI), Malaysia Article Info ABSTRACT Article history: Photovoltaic (PV) panel is the heart of solar system generally has a low energy conversion efficiency available in the market. PV panel temperature Received Oct 2, 2015 control is the main key to keeping the PV panel operate efficiently. This Revised Nov 27, 2015 paper presented the great influenced of the cooling system in reduced PV Accepted Dec 18, 2015 panel temperature. A cooling system has been developed based on forced convection induced by fans as cooling mechanism. DC fan was attached at the back side of PV panel will extract the heat energy distributed and cool Keyword: down the PV panel. The working operation of DC fan controlled by the PIC18F4550 micro controller, which is depending on the average value of Direct-current (DC) fan PV panel temperature. Experiments were performed with and without Photovoltaic (PV) panel cooling mechanism attached to the backside PV panel. The whole PV system PV panel temperature was subsequently evaluated in outdoor weather conditions. As a result, it is Solar radiation concluded that there is an optimum number of DC fans required as cooling mechanism in producing efficient electrical output from a PV panel.
    [Show full text]