Heat and mass transfer of evaporative cooler with elliptic tube heat exchangers- an experimental study

摘要

In the present study, an evaporative cooling test system consisting of an elliptical-heat exchanger was examined. Tests were conducted for various airflow rates of 52, 68, 81, 96 Cubic Meter per Minute (CMM), sprinkler water flow rates of 30, 40, 50 Liter per Minute (LPM), and hot water flow rates of 18, 22, 28 LPM. The sprinkle nozzle types and outside wet-bulb temperatures were also investigated. The convective heat transfer of the sprinkle water film outside the tubes and the mass transfer between air and water film on tube bundles were probed. The film thickness and sprinkle water picture were studied using high-speed cameras and image processing techniques. The results show that the mass transfer performance of the evaporative cooler was enhanced with the growth of the airflow rate. When the sprinkler water flow rate rose to 50 LPM, the heat-mass transfer coefficient of the evaporative cooler decreased since the water film on the tube was thickened. The low hot water flow rate at the tube side (18 LPM) resulted in a superior performance due to a high local temperature and improved local mass transfer. The experimental data were used to obtain empirical correlations for the heat coefficient of the liquid film and mass transfer.