4.5: Closed Circuit Evaporative Cooler

4.5 Closed Circuit Evaporative Cooler

In a closed-circuit evaporative cooler, an example is shown in Figure 1.3.1, cooling a process fluid flowing in tubes is achieved by spraying water onto the tubes, deluging them, and forming a film of water that flows downward under the action of gravity. As the water flows down the surface of the tube, it is evaporated by air flowing over it and results in cooling the process fluid.

One of the earliest useful analytical treatments of closed circuit evaporative coolers was by Parker and Treybal. The method was derived before low cost computing facilities were generally available and used Merkel's approximation for the heat-mass transfer process. One of the most significant features of this work is that the variations in the recirculating water temperature as it flowed through the bundle were taken into consideration. In addition, the enthalpy of the saturated air was assumed to be a linear function of temperature, making it possible to integrate the simultaneous differential equations over the height of the coil.

Mizushina et al. using a similar approach to Parker and Treybal integrated their equations numerically using a computer. At the same time, they carried out some useful experiments to determine the applicable heat and mass transfer coefficients in a smooth tube bundle having a triangular tube layout.

Perez-Blanco and Bird did an analysis on the performance of a rather idealized vertical counterflow evaporative cooling unit but used the correct thermodynamic equations without any approximations. Kreid et al. presented an...