24 June 2014
With increasing efficiency standards and higher energy costs, the demand for reversible air-conditioning/heat pump systems is increasing throughout the stationary market. The heat exchangers in such reversible systems must perform reliably as both evaporator and condenser. The outdoor coil, specifically, is subject to very large changes in both
operational pressures and temperatures. With this increase in demand and the gradual shift
of the industry to aluminum microchannel coil design, comes a need to better understand and quantify the reliability of the heat exchangers. This paper presents the development of
an accelerated thermal cycling test method using refrigerant at typical pressures and temperatures to demonstrate the reliability of said heat exchangers. This method employs a
technique of switching the heat exchanger between condensing and evaporation modes rapidly while monitoring strain at various locations of concern to quantify any shift in strain
caused by fatigue.