Effects of channel configuration on hydrothermal performance of the cylindrical mini-channel heat sinks

Abstract

This work presents the numerical and experimental studies of the thermal and hydraulic performances of cylindrical mini-channel heat sinks (CMCHSs) based on the constructal theory and the entransy principle. Helical and wavy channels were proposed to enhance the heat transfer of CMCHSs in comparison with a conventional channel configuration (straight channel). A numerical simulation was performed using a three-dimensional finite volume method. On the basis of constructal theory, five degrees of freedom (DOFs) were presented, analyzed and discussed to show the geometrical impacts on the performance of CMCHSs when the laminar flow of water was less than 500. The DOFs of the design were channel configuration (straight, helical and wavy), channel aspect ratio (0.467–4), solid void fraction (80%, 85% and 90%), pitch ratio (1.5, 1.8, 2.1, 2.4 and 2.7) and wave amplitude ratio (0.032, 0.048, 0.062, 0.080 and 0.095). The experimental work examined the impacts of parameters on the thermal performance of fabricated CMCHSs with the optimum channel dimensions obtained from predicted numerical simulation and validated the computational simulation. In addition to the energy analysis of the performance of CMCHSs, a performance analysis was also conducted according to the entransy principle to determine the lowest entransy dissipation rate (EDR) and entransy dissipation thermal resistance. The numerical predicted results corroborated that DOFs have significant impacts on the performance of CMCHSs. The best solid void fraction and channel aspect ratio are 90% and 0.46, respectively. For the proposed CMCHSs with helical and wavy channels, Nusselt number and friction factor ratios increase with the increase of pitch and amplitude ratios. The preferred pitch and amplitude ratios are 2.1 and 0.08 because of their high-performance factor. The comparison between the channel configurations affirmed that the slight difference is in the values of the total EDR amongst the three channels. Moreover, the comparison of the best thermo-hydraulic performance of CMCHSs between helical and wavy channels indicated that the best performance was achieved in the helical channel with the lowest total EDR.