30 May 2005

DEMONSTRATION OF A MICROCHANNEL HEAT EXCHANGER FOR OPERATION IN A REVERSIBLE HEAT PUMP SYSTEM


This paper presents results from the integration of a microchannel heat exchanger (MCHEX) into a
conventional R410A reversible air-to-water heat pump system. This implementation is made assuming
equal face areas for the heat exchangers analyzed. The overall goal of the investigation is to achieve an
easy integration of the MCHEX into the baseline unit and an efficiency increase in both heating and
cooling modes. The impact of utilizing a MCHEX on refrigerant charge and refrigerant distribution, along
with frosting concerns are also evaluated. The baseline unit was tested to establish operating conditions
for properly designing the MCHEX into the heat pump system. The new system, equipped with the
MCHEX, shows very encouraging results in terms of refrigerant charge reduction (nearly 50% versus
baseline unit) and efficiency gain (about 15%) for cooling mode. Tests performed in heating mode
demonstrate similar frosting characteristics to the baseline unit and successful draining of the condensed
humidity. Distribution patterns of the liquid refrigerant in two phase-flow indicate inadequate circuiting,
which leads to approximately equal performance with the baseline unit instead of an anticipated increase.
Analysis of the MCHEX circuiting with a thermal imaging (IR) camera has identified areas for further
design improvements that will be tested.