Parallel flow heat exchangers have much to offer the HVAC industry in improved performance and reduced refrigerant charge. An obstacle to their more widespread application is their unknown performance as an outdoor evaporator. Most large residential HVAC original equipment manufacturers, (OEMs) build both heat pumps and condensing units in the same factories and would prefer to use the same heat exchange technology in both systems. Before many OEMs can apply parallel flow technology, it must be applicable to heat pumps as well as condensing units. Before it can be applied to heat pumps, more must be known of its performance as an outdoor evaporator including its frosting and defrosting characteristics. An additional concern is the long-term integrity of the parallel flow heat exchanger as it undergoes many frost/defrost cycles. Currently, there is no known information in the literature on this topic.

The objective of this research project is: 1) To test a heat pump employing a conventional plate-fin heat exchanger in the outdoor unit; 2) To quantify the above system's performance in cooling mode with the outdoor heat exchanger operating as a condenser; 3) To quantify the above system's performance in heating mode under frost accumulation conditions with the outdoor heat exchanger operating as an evaporator; 4) To measure the time required for the coil to clear its frost load and resume its heating function; 5) To repeat objectives 2-4 having replaced the plate-fin heat exchangers of various fin pitch tube orientations.