Development and assessment of defrosting strategies for transport refrigeration systems

When commercial transport refrigeration systems operate at temperatures of 0°C frost accumulates on the surface of the evaporator coil. Occasionally, defrost cycles are required to remove frost from the coil to sustain effective operation of the refrigeration system. This paper details results of an experimental investigation undertaken to characterise the performance of an existing defrost strategy that was in turn modified to improve its performance and effectiveness. Results are reported for two significant modifications, the first of which utilises new criteria for terminating the defrost cycle and the second that employs higher compressor speeds during defrost. Results show that the number of defrosts required was reduced by 20 to 40% yielding more stable temperature control and reduced fuel consumption during defrost.