Evaluating the efficiency of pin–fin micro-heat sink considering different shapes of nanoparticle based on exergy analysis

In this paper, the exergy rate analysis at a pin–fin micro-heat sink (MH/S) is investigated numerically. The critical part of a MH/S contains several square-shaped pin–fins. A turbulent flow of water/boehmite alumina nanofluid (N-F) moves on the pin–fins and cools the MH/S. Constant heat flux is entered into the lower part of the pin–fin MH/S. The governing equations are solved based on the control volume method and simple algorithm. The K-epsilon model is applied to model the N-F flow over pin–fins. The first-law, second-law efficiencies, gains exergy rate, loss exergy rate, and output exergy rate are studied in analysis. Variables considered in the problem consist of the inlet flow rate of N-F, N-Ps shape, and volume fraction of N-Ps in water. The main purpose of this paper is to investigate the exergy rate of various N-P shapes in a MH/S. The results of this study showed that increasing the flow rate reduces the temperature of the MH/S. Increasing the velocity and volume percentage reduces the amount of out exergy rate. In fact, by increasing the velocity from 1 to 3 m s−1 for water, the amount of out exergy rate output decreases by 7.36 W. The greatest reduction in loss exergy rate is for platelets N-Ps with a reduction of 441 W. Also, increasing the velocity and decreasing the volume percentage reduce the efficiency of the first law of thermodynamics, which is 8.5% for platelets N-Ps. The addition of these N-Ps reduces the efficiency of the second law by 5.7%.