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Active and passive cooling are the two possible methods for removing heat. An active cooling system is the one that involves the use of energy as opposed to passive cooling that uses no energy. Passive cooling methods are cost effective and more reliable than active cooling due to the absence of moving parts. Microchannel heat sink is one of high-tech devices that have widely considered passive cooling methods especially for electronics cooling. In this paper, the use of passive cooling methods in microchannel heat sink is comprehensively discussed. This paper also present the effects of some important parameters such as the type of channel types, surface roughness, fluid additives, and Reynolds number on the rate of heat transfer in microchannel heat sink. Finally, the conclusions and important summaries were presented according to the data collected. [ABSTRACT FROM AUTHOR]

Nanofluids have gained significant attention in recent years due their great potential for heat transfer enhancement . The heat transfer of nanofluids can be numerically studied using a single-phase or two-phase approaches. The first assumes that the fluid phase and nanoparticles are in thermal equilibrium and move with the same velocity, while the second requires more computational effort but provides the possibility of understanding the behavior of both fluid phase and solid particles in the heat transfer mechanism. This paper reviews various computational approaches to predict fluid flow and heat transfer characteristics of nanofluids. The characteristics of single-phase and two-phase (volume of fluid, mixture, Eulerian–Lagrangian and Eulerian–Eulerian) approaches have been analyzed and discussed systematically. Latest development and recent researches related to the computational nanofluids are also given. [ABSTRACT FROM AUTHOR]

This paper reviewed the application of nanofluids in vehicle engine cooling system. So far, nanoparticles have been used in engine oil, transmission oil, and radiator coolant to enhance heat transfer removal from vehicle engine. The heat transfer performance of nanofluids has been reported to perform better compared to pure fluid. This review focused on the experimental and numerical studies by previous researchers and their suggested amount of nanoparticles for optimum performance in vehicle engine cooling system. Finally, the conclusions and important summaries were presented according to the data collected. [ABSTRACT FROM AUTHOR]

The performance of friction drag, heat transfer rate, and mass transfer is illustrated the in boundary layer flow region via density of motile microorganisms. Magnetic dipole in presence of Curie temperature and density of motile microorganisms plays important role in stabilizing and controlling the momentum and thermal boundary layers. In this direction, the characteristics of the magnetic dipole on the suspensions of motile microorganisms in the flow of ferrofluid are incorporated. Heat flux in the suspensions of motile microorganisms and at the surface is computed via Fourier's law of heat conduction. Characteristics of sundry physical parameter on the ferrohydrodynamic, thermal energy, mass transfer, and bioconvection are computed numerically and analytically. It is depicted that an enhancement in thermal Rayleigh number results in the reduction of friction drag, thereby enhances the heat transfer rate and Sherwood number at the surface, while the local density of motile microorganisms enhance for larger values of bioconvection Lewis number. Further, it is characterized that bioconvection Rayleigh number has increasing behavior on the heat transfer in the boundary layer. Comparison with available results are found in an excellent agreement. • Heat transport phenomenon is depicted in motile micro-organisms. • Thermal Rayleigh number results in the reduction of friction drag. • Velocity reduces and the temperature field enhances for β_{f}. • The wall shear stress of the motile micro-organisms reduces. • The fast reduction in heat transfer rate is observed. [ABSTRACT FROM AUTHOR]

In this article, turbulent flow characteristic of nanofluids is thoroughly reviewed. Turbulent flows have unique characteristics and are preferred in many industrial applications. Therefore, this paper reviews different techniques used to enhance heat transfer using nanofluids within turbulent regime. This paper also presents the effects of some important parameters such as nanoparticle type, nanoparticles concentration, and Reynolds number on heat transfer rate. Studies on numerical techniques are also discussed. Finally, the conclusions and important summaries are presented according to the data collected. [ABSTRACT FROM AUTHOR]

This article deals with numerical analysis of two-dimensional viscous fluid in modified square duct. A rectangular obstacle with constant temperature at walls is placed inside it. Flow duct is depicted in Figs. 1 and 2. Influence of Prandtl number and geometry on heat transfer of working fluid is studied in two cases. Computation for the present model is made in commercial package ANSYS-Fluent. Calculations are carried at two different values of Reynolds numbers i.e., Re 40 and 200 for each of the cases. Liquid water (H 2 0) and Liquid Aniline (C 6 H 5 NH 2) are taken as working fluids. Stream functions, isotherms, vorticity, velocity and pressure profiles are examined. Graphical data for C f and Nu is presented to analyze the effect of Reynolds number and Prandtl number on heat transfer. Thermal boundary layers are discussed in each of the cases. It is shown that heat transfer has high dependance on Reynolds number and Prandtl number. Geometry of the problem has noticeable effect on heat transfer. [ABSTRACT FROM AUTHOR]