Experimental Research on new MPE tube for Micro Channel Heat Exchanger used in Air-cooled Commercial Heat Pump

We well know that micro channel heat exchanger is more effective for a performance enhancement than Fin & Tube heat exchanger in Chiller applications and it helps to reduce refrigerant quantities in the systems. In Heat Pump applications, on the other hand, the outdoor unit is normally subjected to the frost / defrost issue when the ambient temperature approaches the 0 °C and this aspect challenges the MCHE usage.

This presentation shows the results of a study where we tested a new MPE tube for Micro Channel Heat Exchanger installed on Air-cooled Heat Pump, a typically modular version of commercial size. Aim of the study was to reach a frosting time of the MCHE in evaporation mode as close possible to the traditional technology of Fin&Tube and keeping the same parameters in efficiency.
The study was divided in two parts: an initial section where we found the theoretical grounds for the new geometrical size and the experimental part where these reasons were confirmed from the results. In the MCHE working as evaporator in HP application, the refrigerant flow is normally co-flow with the air flow direction, thus the inlet point is where the temperature approach is bigger and the frosting effect larger.
Reducing the refrigerant circulation area in each channel, it is possible to increase the refrigerant pressure drop with a consequent increase of the fin temperature at the inlet. The minor temperature gradient reduces the amount of frosting in this initial critical section allowing the heat exchanger a lasting working time. Balancing this effect with an optimized fin spacing, it was possible to reach frosting time at the same value as traditional technology Fin & Tube.