Air-Side Thermal Behavior of Parallel-Plate Evaporators. Part II: Performance under Frosting

In the second part of the paper, an experimentally validated extension of the mathematical model is presented to simulate the thermal behavior of a roll-bond parallel-plate evaporator under frosting. This novel heat exchanger geometry is a potential alternative to finned-tube "no-frost" evaporators in some applications. The experimental work consisted of testing one of the heat exchanger prototypes selected from Part I in a closed-loop wind tunnel calorimeter at different conditions of air temperature, humidity, air flow rate and inlet coolant temperature. The semi-analytical model divided the evaporator in control volumes involving the air, plate and coolant and solving the momentum, energy, and species balance equations to generate distributions of air humidity, temperature, and pressure, as well as frost thickness and aluminum plate temperature. A good agreement was observed for the heat transfer rate, mass of frost accumulated in the heat exchanger and pressure drop, as most data points were predicted to within ±20% relative error.