Thermo-exergetic analysis of micro pin fin heat sinks

A parametric study of thermo-economic performance over four micro pin fin heat sinks of different spacing and shapes was conducted. Unit cost per product exergy, relative cost difference, and exergo-economic factor were utilized to evaluate the thermodynamic performance. The effect of working fluid on thermo-economic performance was also investigated using R-123 and water as working fluids. Unit costs per product exergy were obtained to evaluate and compare the costs of products (total exergy change between exit and inlet streams) in micro pin fin heat sinks at fixed mass flow rate and fixed pressure drop. The results of thermo-economic analysis were compared to the results of a past exergy performance study. Important differences were observed and unveiled between the results of exergy and exergo-economic performances. It was found that the unit cost of exergy change decreased as the electrical power was increased and the relative cost difference became close to unity at high electrical powers. Moreover, high exergo-economic values were obtained at low electrical powers while f had a small value at high electrical powers. When looking at the effect of the working fluid, lower cost per Watts of the products was obtained with R-123 compared to water at both fixed mass flowrate and pressure drop. No significant effect of pin fin spacing on the unit cost of exergy change was observed at fixed mass flowrate, while higher unit costs were recorded at fixed pressure drop for scarcely packaged pin fin heat sinks. Finally, the unit cost of exergy change was found to be independent on pin fin shape at fixed mass flowrate, whereas at fixed pressure drop, the hydrofoil based pin fin heat sink had higher unit costs compared to flow separation promoting ones.