A closed circuit cooling tower, or dry cooling tower, involves no contact between the air and the fluid being cooled. This tower has two separate fluid circuits, one in which the fluid is recirculated on the outside of the second circuit, which is a bundle of tubes through which the hot water is flowing. The air drawn through this cascading water provides evaporative cooling similar to an open cooling tower, except that the cooled water never makes direct contact with the air.Another closed circuit cooling tower system involves a separate heat exchanger package along with an open cooling tower. The fluid on the hot side of the heat exchanger also never makes direct contact with the air. This allows the heat exchanger to be put inside protected from outdoor weather elements along with other system advantages.
Principle of Operation
Closed circuit cooling towers operate in a manner similar to open cooling towers, except that the heat load to be rejected is transferred from the process fluid (the fluid being cooled) to the ambient air through a heat exchange coil. The coil serves to isolate the process fluid from the outside air, keeping it clean and contaminate free in a closed loop. This creates two separate fluid circuits: (1) an external circuit, in which spray water circulates over the coil and mixes with the outside air, and (2) an internal circuit, in which the process fluid circulates inside the coil. During operation, heat is transferred from the internal circuit, through the coil to the spray water, and then to the atmosphere as a portion of the water evaporates.
welltechcoolingtower manufactures two types of closed circuit cooling towers
Combined flow is the use of both a heat exchange coil and fill for heat transfer in a closed circuit cooling tower. The addition of fill to the traditional closed circuit cooling tower design reduces evaporation in the coil section, reducing the potential for scaling and fouling. welltechcoolingtower combined flow closed circuit cooling towers utilize parallel flow of air and spray water over the coil, and crossflow air/water flow through the fill.In parallel flow, air and water flow over the coil in the same direction.
In a counterflow closed circuit cooling tower design, the flow of the air is in the opposite direction of the spray water. In WelltechCoolingTower’s counterflow closed circuit cooling towers, air travels vertically up through the unit while the spray water travels vertically down over the coil. The process fluid flows from top to bottom through the coil and is in thermal counterflow to the air.A counterflow cooling tower requires less plan area than a crossflow cooling tower.