The effect of frost formation on the performance of a domestic refrigerator-freezer evaporatorcoil was investigated. A low temperature evaporator test facility was developed to closely simulaterefrigerator-freezer conditions. The rate of frost deposition on the evaporator was determined to beconstant with respect to time for a ten-hour testing period over a range of air inlet temperatures andrelative humidities, refrigerant temperatures, and airflow rates. Higher humidities and air inlettemperatures and lower refrigerant temperatures were found to increase the frosting ratesignificantly. Varying the airflow rate was found to slightly affect the frosting rate. Increasing theairflow rate increased the frosting rate a small amount, while, decreasing the airflow rate decreasedthe frosting rate an equally small amount. However, it appears that the actual correlation betweenairflow rate and frosting rate is not this straight-forward, but is, instead, the result of the influencesof the mass transfer coefficient, the evaporator surface temperature, and the air moisture capacity.How these factors balance one another determines the actual relationship between frost rate andairflow. rate. In addition to these findings, it was found that the UA-value of the evaporatorincreased as frost was-deposited on the coil while a constant airflow rate was maintained throughthe coil. The increase at the highest frosting rates was on the order of 40% but was accompaniedby an exponentially increasing air side pressure drop.
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