A Novel Passive Defrost System for a Frozen Retail Display Cabinet with a Low Evaporator

An energy efficient thermo-siphon method of defrosting the air coils on a commercial half glass door (HGD)/well retail display cabinet has been developed (FrigescoTM) and the performance compared with the existing electric defrost system under EN ISO 23953 test room conditions. Previous work by (Foster et al, 2013) used a passive thermo-siphon to defrost the top evaporator inside the top (glass door) section and a pump assisted thermo-siphon to defrost the well section. This was due to the head being too low to adequately defrost the well evaporator with a passive thermo-siphon. This work describes a passive thermo-siphon with no pump. To enable the thermo-siphon to operate efficiently the design of the evaporator was optimised. The thermo-siphon heated quicker and melted water faster than the electric defrost. The thermo-siphon used less electrical heat and had an added benefit of free sub-cooling.