Heat transfer enhancement of closed loop cooling tower by using water spray

Abstract

A closed wet cooling tower became popular for heat transfer process, but the existing system was not sufficient for the heat transfer of the manufacturing line. This research aimed at investigating the heat transfer enhancement of the 200-ton closed cooling tower by installing spray nozzles to spray water to the condenser. The distance between the spray nozzles and the condenser were 20, 30, 40, 50, and 60 centimeters. The mass flow rates of water spray were 8, 10, 12, and 14 liters per minute. The objectives of the study, therefore, were to study the heat transfer coefficient of cooling water and to evaluate the economic value of this improvement option’s investment costs. In this study, the outlet temperature of the cooling tower was set to be less than 37°C, the difference of inlet and outlet water temperature was 2.9°C, and the overall heat transfer rate approximated 360 kW. The results of the study reported that the distance of the spray nozzles and the condenser was at 30 centimeters, and the mass flow rate of water spray was 12 liters per minute. The rate of heat transfer was 362 kW. The efficiency of the cooling system was 0.8, which became suitable for real use. In addition to considering value investing, the results showed that the payback period was 0.47 years, and the net present value was 1,693,801 baht. The rate of return received from the project was 207%, which was worth investing.