Closed Circuit Fluid Coolers contain two separate fluid circuits, they are external circuit and internal circuit. In external circuit, water is exposed to the atmosphere as it cascades over the tubes of a coil bundles. In internal circuit, the fluid to be cooled circulates inside the tubes. These coolers are used on heat pump systems and screw compressors. Closed circuit fluid coolers use the evaporation of a small volume of the recirculated water within a system to remove heat. The closed circuit fluid coolers minimize particulates within the condenser water and maintain high quality condenser water.