Abstract: The parallel flow heat exchanger’s thermal transfer performance under frost conditions was investigated. The heat transfer area and overall surface efficiency change as the frost grows. The airside heat transfer coefficient was also calculated using logarithmic-mean temperature difference (LMTD) method. The result shows that when the frost thickness grows to 0.4 mm, the heat transfer area decreases by 18%, and the air side surface efficiency decreases by 17.42%~24.78%. Moreover, the reduction of the heat transfer coefficient is an important cause to the decline of heat exchanger performance. The heat transfer coefficient decreases about 50% in the tests, while louver gap blockage mainly contributes to the decrease of heat transfer coefficient.  

Key words: parallel flow heat exchanger, frost, heat transfer area, surface efficiency, heat transfer coefficient