Abstract
Nanofluid has great potentials in heat transfer enhancement and entropy generation decrease as an effective cooling medium. Effects of Al2O3-water nanofluid flow on entropy generation and heat transfer performance in a rectangular conventional channel are numerically investigated in this study. Four different volume fractions are considered and the boundary condition with a constant heat flux is adopted. The flow Reynolds number covers laminar flow, transitional flow and turbulent flow. The influences of the flow regime and nanofluid volume fraction are examined. Furthermore, dimples and protrusions are employed, and the impacts on heat transfer characteristic and entropy generation are acquired. It is found that the average heat transfer entropy generation rate descends and the average friction entropy generation rate rises with an increasing nanofluid volume fraction. The effect of nanofluid on average heat transfer entropy generation rate declines when Reynolds number ascends, which is inverse for average friction entropy generation rate. The average wall temperature and temperature uniformity both drop accompanied with increasing pumping power with the growth in nanofluid volume fraction. The employment of dimples and protrusions significantly decreases the average entropy generation rate and improve the heat transfer performance. The effect of dimple-case shows great difference with that of protrusion-case.
Highlights
As the remarkable development of the electronic equipment technology and consequent continuous growth of the device output power, the requirement of superior cooling technique has been dramatically drawing the researchers’ attention
Fan and Wang [6] provided a review on heat conduction of nanofluids in which they focused on thermal conductivity of nanofluids
It can be concluded that when Re reaches 10,000 or even higher, the mainstream has completely turned into turbulent flow, and the Reynolds number range in this study covers laminar flow, transitional flow and turbulent flow
Summary
As the remarkable development of the electronic equipment technology and consequent continuous growth of the device output power, the requirement of superior cooling technique has been dramatically drawing the researchers’ attention. Koo and Kleinstreuer [16] presented a model for calculating the thermal conductivity of nanofluids (K-K model) and they took account of the influences of the particle size, volume fraction and temperature dependence, and effects of the properties of base fluid and nanoparticles are seriously considered. Considering the extended irreversible thermodynamics, Machrafi and Lebon [18] presented a model for predicting nanofluids thermal conductivities, and the effect of coupled heat transfer mechanisms is taken into great consideration, including the interfacial layering between the base fluid and nanoparticles, Brownian motion and particles agglomeration. Suresh et al [23] experimentally examined the convective heat transfer and friction characteristics of distilled water and CuO-water nanofluids in flat and dimpled tube under laminar flow, and a constant heat flux boundary condition was adopted Later on, they conducted a similar study under turbulent flow [24]. The assessments effects on average wall temperature, wall temperature uniformity and pumping power are analyzed to provide assessments of the thermal performance
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