Experimental and numerical investigation of a dew-point cooling system for thermal comfort in buildings

Abstract

Using the latent heat of evaporation of water as a natural driving energy resource, indirect evaporative cooling (IEC) systems can decrease air temperature without increasing its moisture content. The performance of any evaporative cooling system is largely dependent on the structure and design of the heat and mass exchanger. By modifying the exchanger of the IEC system, air could be cooled below its wet bub temperature and towards the dew point temperature. In this study a numerical analysis is carried out for a modified dew point cooling system based on a proposed psychrometric energy core (PEC) with a cross-flow heat and mass exchanger for buildings air-conditioning applications. A detailed numerical model was developed for the energy core with the cross-flow exchanger using Matlab. The coupled heat and mass transfer equations were solved using a fully implicit accurate finite difference scheme to predict air temperature and humidity distribution throughout the dry and wet channels. With an intake air of 30°C temperature and 50% relative humidity and a working-to-intake air flow ratio of 0.33, the system attained a wet bulb effectiveness of 112% and a dew point effectiveness of 78% with 5mm channel height and 500mm channel length. In addition, an experimental setup was built and a dew-point cooler with a cross-flow heat and mass exchanger was tested to assess the feasibility of using such dew point cooling systems under various operational and ambient conditions. The numerical model developed was validated using published data in addition to the experimental results. Using the validated model, a parametric study was carried out for a dew-point cooler with cross-flow heat and mass exchanger to investigate the effect of different operational parameters on the overall performance and to optimize the cooling system performance to achieve the indicated thermal comfort levels in buildings.