Performance of microchannel cooling system depends on, inter alia, vapor quality in the evaporator. Therefore, optimization of evaporation requires precise control of quality at the microchannel inlet (x).

Here, we compare three different kinds of preheaters used to adjust x: an immerse heater, a brazed plate heat exchanger (BPHE) and direct current (DC) heater.

The study covers critical heat flux (CHF), pressure drop, heat transfer coefficient, operating temperature limits imposed by refrigerant, uncertainties in x, and power control. The refrigerant is R245fa and the saturation temperature is 40-90°C.

Immerse heaters require liquid immersion and, depending on geometry, are prone to CHF occurrence. BPHE requires silicone oil as a heating medium and, consequently, expensive measuring equipment. Compared to BPHE, DC heating offers lower uncertainties, but it is limited by the maximum voltage of the power supply.