Theoretical and numerical investigation on the fin effectiveness and the fin efficiency of printed circuit heat exchanger with straight channels

Theoretical and numerical studies were conducted on the fin effectiveness and the fin efficiency of printed circuit heat exchanger (PCHE). A heat conduction equation for the fins of PCHE with straight channels was derived, from which the longitudinal temperature distribution of the fins can be obtained. And the expressions of the fin effectiveness and the fin efficiency were developed. Based on their expressions, an understanding of the heat transfer process between the fin surface and the bulk fluid was improved. Results show that the PCHE fin effectiveness is enhanced by the choices of high fin thermal conductivity, decreasing the ratio of the fin thickness to the radius of the channels, or under conditions for which the convective coefficient is small. As for the fin efficiency of PCHE, it's improved with high fin thermal conductivity, thick fin and low convective coefficient of the working fluid. For the cases with large Biot number, the PCHE fin effectiveness and the PCHE fin efficiency can be weakened up to 20%, which should be considered in the modeling of thermal-hydraulic. Moreover, the theoretical investigations were validated against the numerical simulation, and they agree with each other very well.