When the nominal condenser is heated, liquid condenses in the evaporator and the reservoir. These reverse the evaporator and condenser sides for the defrost cycle. A small refrigeration compressor was used to remove heat from the evaporator coils. The evaporator and condenser are usually cleaned with running water. Owing to viscosity effects, working fluid pressure drops in both the evaporator and the condenser. The refrigerant is boiled by the heat source in the evaporator to produce super-heated vapor. The condenser/evaporator (outdoor) fan will not run during defrost mode. The cold mixture is then routed through the coil or tubes in the evaporator. The interior air is cooled as a fan blows it over the evaporator. Finally it flows through the evaporator and super heater. This arrangement is described as a vacuum insulated evaporator or bulk tank. HRSGs consist of four major components&colon; the economizer, evaporator, superheater and water preheater . The principal changes are in the scale and type of compressor and evaporator. The Waste Heat Recovery Boiler (WHRB) has 3 sections&colon; Economiser, evaporator and superheater. Fresh water is produced by either an evaporator or a reverse osmosis unit.