Experimental study of the effect of filled bed type on the performance of a cross-flow cooling tower with the approach of using nanofluids

Abstract

This study aimed to experimentally investigate the effects of filled beds on the performance of a cross-flow cooling tower (CFCT) with the approach of using nanofluids. Multi-walled carbon nanotubes (MWCNTs) and titanium dioxide (TiO2) nanofluids and 6 kinds of filled beds in two classes of splashes and films were used. To select the best bed using TiO2/water and MWCNTs/water nanofluids with a concentration of 0.05 wt%, the effect of these beds on the thermal performance of CFCT was evaluated, and the results were compared with each other and with pure water. The effects of nanofluid type and flow ratio (L/G) on CFCT performance factors, including cooling range, effectiveness, Merkel number, and evaporation rate, were investigated. The nanofluids were prepared by the two-step method and gum arabic was used as a surfactant to improve their stability. The results showed that, using nanofluids instead of water as the operating fluid generally improves the thermal performance of CFCT. It was found that the appropriate bed for water and nanofluid was bed 5 and bed 3, respectively. As well as, the use of a suitable filled bed at low flow ratio had a much greater effect on improving the performance of the tower. For example, at the same concentration of MWCNTs/water nanofluid using bed 3, the increase in tower effectiveness compared to pure water was about 28% at L/G=0.4, while it was only 7% at L/G=2. In addition, the parameters of cooling range, effectiveness, and Merkel number were increased by 28%, 85%, and 131%, respectively, when bed 3 was used compared to the bedless condition, indicating the importance of a suitable bed when using nanofluids.