DA-13-028 -- Investigation of Electric and Reverse-Cycle Hot-Gas Defrosting for Evaporators in Refrigeration Systems PDF

This paper investigates the performance of evaporator heat exchangers' defrosting methodology for refrigeration systems. The electric defrosting method for evaporators is often utilized for relatively small systems below 20 kW (5.7 TR) and with direct-expansion (DX) evaporators operating at - 20°C (-4°F) and below. However, the use of hot-gas defrosting is rarely seen for systems in this range. The project design for this study includes special feature: two evaporators (DX and flooded), two defrosting cycles (electrical and reverse hotgas), and control and data logging by a process logic controller (PLC). Both evaporators are linked to a common condenser to provide two separate circuits. The performances of the two defrosting methods are compared for three operating temperatures: -20°C, -10°C, and 0°C (-4°F, 14°F, and 32°F) and analyzed to ascertain suitable operation and viability for such systems.