Practical guidance for optimization of defrost.

Regular defrost of air cooling coils is necessary to restore cooling performance but creates parasitic load on the refrigeration system and can result in short term temperature fluctuations in the refrigerated space. A new method that directly links defrost heat load to latent loads in the refrigerated facility and likely melt water flows is presented. Practical guidance, that is informed by both this method and measurements for actual systems, is provided for the optimization of defrost frequency and duration. Key aspects are: to have a method that terminates defrost once the coil is free of frost and there is no more melt water to avoid unproductive heating; and to vary the frequency of defrost to match the latent load the facility experiences so there is a similar frost loading at the start of each defrost.