Performance assessment of annular fins and cellulose cooling pad on heat transfer enhancement of evaporative heat exchangers using volumetric heat and mass transfer coefficients

In the present work, a test facility has been built to assess the performance of evaporative heat exchangers. The experimental set-up consists of Fan-Cooling pad-Water spray-Heat exchanger (FCWHX) unit with four different configurations namely a) plain tube heat exchanger and b) finned tube heat exchanger with water spray arrangement on their top and without cooling pad, c) plain tube heat exchanger and d) finned tube heat exchanger with cooling pad and water spray arrangement on the top of cooling pad. Experiments are conducted during various durations with climatic conditions in the range of 27 degrees C-31 degrees C DBT and 45%-65% RH. While testing the FCWHX unit with and without cellulose pad, exit temperature and humidity of air, exit temperature of spray water and exit temperature of hot water from heat exchanger were continuously monitored. The performance parameters namely heat exchanger duty, evaporative cooling rate and evaporation rate of spray water, volumetric heat and mass transfer coefficients have been determined. Correlations for Nusselt and Sherwood number for all four configurations of FCWHX unit have been presented from these studies, with a maximum of +/- 10% error band.