Heat Transfer Engineering, 37(2):1–15, 2015 C Taylor and Francis Group, LLC Copyright ISSN: 0145-7632 print / 1521-0537 online DOI: 10.1080/01457632.2015.1044392
Influence of Heater Aspect Ratio on Natural Convection in a Rectangular Enclosure NIRMALENDU BISWAS, PALLAB S. MAHAPATRA, NIRMAL K. MANNA, and PROKASH C. ROY Department of Mechanical Engineering, Jadavpur University, Kolkata, India
Analysis of natural convection with heating source protruding from the nonheated lower surface of a rectangular enclosure has been performed using experimental apparatus of a two-dimensional particle image velocimetry system. Results obtained from the experiments are used to validate the numerical simulations. Extensive numerical simulation is carried out using in-house code based on the finite-volume method and the SIMPLE algorithm. Heat transfer and entropy generation are estimated numerically for a protruding heater of different perimeters and aspect ratios, Rayleigh number, and Prandtl number. It is found that the Rayleigh number, Prandtl number, and heater sizes have strong influence on the flow fields, thermal mixing, heat transfer characteristics, and entropy production rate in the enclosure. The analysis indicates that a high thermal mixing may not be the most favorable situation for achieving higher degree of temperature uniformity. The effect of Bejan number is discussed.
energy storage systems, furnaces, heat exchangers, materials processing such as solidification phenomena and growing crystals, micro-fuel-cell designs, and in many other fields. Natural convection is extensively used for passive cooling of electronic devices [1]. Extensive reviews have been done on natural convection in locally heated enclosures (Ostrach [2], Incropera [3], and Davies [4]). The presences of thermal gradient, frictional effects, diffusion, or chemical reaction in a thermodynamic system are subjected to energy losses, which induce entropy generation in the system and increase irreversibility. The optimal design criteria for a thermodynamic system could be achieved by analyzing entropy generation and minimizing the irreversibility in the system. As such, entropy generation has recently been a topic of great interest in many fields, such as heat exchangers, turbomachinery, electronic cooling, porous media and combustion, and so on (Magherbi et al. [5]). Review of the technical literature presents many studies of entropy generation due to natural convection in a cavity. Some other applications on entropy generation due to natural convection for different geometries can be found in the literature, as reported in Oliveski et al. [6], Erbay et al. [7], Shuja et al. [8], and Aydin and Yang [9]. A significant volume of work based on experimental technique using particle image velocimetry (PIV) technique and numerical analyses of the natural convection in an enclosure having
INTRODUCTION The effective heat removal from electronic components has become a problem of significant interest due to the continuing reduction in feature size and increase in functional performance with the fast growth of electronic technology. As electronic components produce heat as a by-product of normal operation, it is very important that cooling systems to be designed in the most efficient way and that the power requirement for the cooling is minimized. Natural convection is the only feasible mode of cooling of the heat source in numerous applications. Moreover, natural convection is cheap, convenient, and is free from auxiliary electromechanical equipment. For these reasons, application of natural convection is increasingly fascinated in thermal control because of its low cost, reliability, and simplicity for use. There is a great interest in investigation of natural convection in enclosures, as it is a very common phenomenon in several environmental problems and engineering applications, for example, solar energy systems, the cooling of electronic equipment, air conditioning and ventilation systems, nuclear reactor design,
Address correspondence to Asst. Professor Nirmal K. Manna, Department of Mechanical Engineering, Jadavpur University, Kolkata 700 032, India. E-mail:
[email protected]
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