Thermodynamic Optimization of Tube-Fin Evaporators Operating under Frosting Conditions

In this study, the method of entropy generation minimization (i.e., design aimed at facilitating both heat, mass and fluid flows) is used to improve the evaporator geometry (aspect ratio and fin density) considering the irreversibilities produced by the heat and mass transfer, and viscous flow processes. A fully algebraic semi-empirical model was put forward to simulate the thermal-hydraulic behavior of tube-fin evaporator coils running under frosting conditions. The model predictions were validated against experimental data from Silva (2012), showing a good agreement between calculated and measured counterparts, with errors within a ±5% band for the cooling capacity and the air flow rate. The optimization exercise pointed out that high aspect ratio heat exchanger designs lead to minimum entropy generation in cases of fixed heat duty and air flow rate constrained by the characteristic curve of the fan.