Thermohydraulic performance analysis and parameters optimization of the combined heat sinks with microchannels and micro pin-fins

Abstract

The combined heat sinks of microchannels and micro pin-fins are numerically studied in depth by three-dimensional conjugate heat transfer models for flow rate (Qv) ranging from 18 to 90 ml/min. The influence degrees of multiple parameters, i.e., the lengths and widths of the cavities and pin-fins, on cooling effect, pressure drop and comprehensive performance are analyzed quantitatively by Taguchi method. And the optimal combination structures for temperature of heat sink (OCS-T), pressure drop (OCS-PD) and performance evaluation criterion (OCS-PEC) are obtained accordingly. The original heat sink with fan shaped cavities and diamond pin-fins (FC-DPF) and the smooth rectangular heat sink (SR) are selected for comparison. The coupling effects of four structure parameters on the local and average thermal hydraulic characteristics are elucidated. The interrelation of multiple physical fields and the comprehensive efficiency of the optimal combination structures are discussed thoroughly. Moreover, the thermodynamic properties and irreversibility are illustrated based on the entropy generation. Results demonstrate that the length of fan shaped cavity and the width of diamond pin–fin have a dominant impact on heat dissipation and pressure drop. The width of cavity has a noticeable impact on the overall performance. Large width of cavity is favorable to induce transverse flow, and large width of pin–fin contributes to distinct vortices. The symmetrical vortices in the direction of channel height can improve chaotic mixing and temperature uniformity. At high flow rate, the performance evaluation criterion (PEC) of the OCS-PEC is increased by 29 % compared to the original structure FC-DPF. When total thermal resistances of the above two heat sinks are similar (0.43 K/W of the OCS-PEC and 0.45 K/W of the FC-DPF), the pumping power of the OCS-PEC (0.47 W) is 35 % lower than that of the FC-DPF (0.72 W) proving the excellent overall efficiency. In addition, the OCS-PD and OCS-PEC show better thermodynamic performance and less irreversible loss for high flow rate, which implies the energy efficiency advantage. The synergistic mechanism of flow and heat transfer is revealed and the results are significant for further understanding the rules of performance enhancement. The excellent overall performance of the OCS-PEC at high flow rate makes it more promising in application for electronic chips cooling in aerospace, defense and communication fields, thermal management of battery, hydrogen storage, fusion energy management, etc.