Experimental investigation of earth-air heat exchanger using porous clay vessels for eco-friendly buildings

Abstract

This study introduces an experimental investigation of a novel direct trend evaporative cooler based on a ground-air heat exchanger (GAHE) using porous clay vessels as an evaporation media under a variety of operational conditions, including air flow rate, inlet air temperature, temperature of inlet water, and in air humidity. The evaluation of the GAHE performance was based on the air-cooling effect, wet-bulb and dew-point efficiencies, energy efficiency ratio, water evaporation rate, specific water evaporation, specific cooling capacity, specific total cost, and CO2 emission rate. The influences of dry-bulb temperature, the incoming air's relative humidity (RH), and six air flow rates ranging from 11 to 25 L/s on the performance are investigated and discussed. Results indicated that increasing the air flow rate leads to an increase in the cooling capacity. Energy efficiency ratio (EER) reaches the highest value of about 25.5 recorded at 3:00 PM with air flow rate = 11 L/s. The lowest EER value is approximately 7.2 when the measured inlet and outlet temperatures are the closest at 7:00 PM, with a flow rate of 25 L/s. Increasing the air flow rate from 11 to 17 L/s increased the wet bulb efficiency, and the airflow rate was inversely proportional to wet-bulb efficiency. The maximum and minimum average dew-point efficiencies are 64% and 58% at 17 L/s and 22 L/s respectively. The water evaporation rate increases by 182.1%, increasing the air flow rate from 11 to 25 L/s.