Performance evaluation of a novel plate-type porous indirect evaporative cooling system: An experimental study

The traditional indirect evaporative cooler (IEC) needs the consistent working of the pump for water spraying to the secondary air channel wall, which consumes an amount of energy and causes the extra pressure drop. Improving the channel surface water retention capacity has drawn research attentions over the years, and using porous materials is expected to deal with this problem. However, there is still lack of quantitative experimental data on the thermodynamic performance of this environmental-friendly heat exchanger. In this study, a plate-type cross-flow indirect evaporative cooler that sintered the porous layer in each secondary air channel surface (PIEC) was proposed and manufactured. A series of experiments were carried out on an established test rig to assess the performance of the PIEC system. It was observed that the air cooling effect could still be observed over time without water supply owing to the water absorbed and retained in the porous layer, which indicated the feasibility of the intermittent spraying plans. Results showed that the PIEC maintained the supply air temperature up to 2105 s within 0.5 °C fluctuation under the test conditions without spraying water, lessening 94.6% of the operation time of the water system. Therefore, the power consumption was significantly reduced. The coefficient of performances (COPs) were enhanced by 117.5% on average compared with the conventional continuous spraying mode. In addition, the pressure drop of secondary channels was measured to be lower in the non-spraying mode than in the spraying mode. Eventually, the present experimental study recommended to combine the PIEC as a pre-cooling air-conditioning device with the air handling unit to guarantee the required outlet air temperature for the indoor environment.