Achieving Cooler Soil as an Effective Heat Sink for Earth-to-Air Heat Exchanger (EAHE) Cooling Technology in Malaysia Tropical Climate

This research is intended to explore the capacity of Malaysia soil in becoming a more effective heat sink for the application of Earth-to-Air Heat Exchanger (EAHE) Cooling Technology in Malaysia. EAHE Cooling Technology consists of buried pipes underground where the ambient air is channeled through from the pipe inlet and produces cooler air at its outlet. Within the buried pipes, heat exchange process occurs between the air and the soil that surrounding the pipe. This building cooling technology has been applied in many countries, mostly in temperate or hot and arid climate where the diurnal temperature is large. However, minimal resources were found on the study of EAHE application to buildings in Malaysia, hence there is room to develop. A parametric study on EAHE cooling application in Malaysia was done through field experiment and concluded that among many parameters affecting the technology performance, the soil temperature which surrounded the pipe was the most influential factor. The study recommended to further reduce the soil temperature to achieve a cooler outlet temperature. In response to that, this research conducted a parametric study of soil temperature under three different soil surface conditions: bare, shaded with timber pallettes and insulated with used tyres at 1.0 m and 1.5 m underground. The data was logged for a month and the result has shown significant reduction in the soil temperature underground below the shaded and insulated soil surface as compared to below bare soil surface condition. The insulated soil surface produced the best result where the soil temperature was reduced up to 26.9°C. The main contribution of this paper is to highlight that the soil surface treatment can be used to reduce solar heat gain within the soil underground and thus improving the performance of EAHE Cooling Technology particularly for the application in Malaysia tropical climate.

Cooling performance of earth-to-air heat exchangers applied to a poultry barn in semi-desert areas of south Iraq

Earth-to-air heat exchangers(EAHE)can reduce the energy consumption required for heating and cooling of buildings.The composition and the thermal characteristics of the soil influence the heat exchange capacity,and the soil moisture can furthermore affect thermal performance of EAHE.The aim of this study was to compare the thermal performance of EAHE in dry and artificially wetted soil.Tests were carried out in the Basra Province(Iraq),in a semi-desert area.Two experimental EAHE were built in a poultry barn and tested from June 2013 to September 2013.The pipe exchangers were buried at 2 m deep.One heat exchanger operated in dry soil(DE),while the other one operated in artificially wetted soil(WE).In the WE system,a drip tubing placed 10 cm above the air pipe wetted the soil around the exchanger.Air temperatures at the inlet and at the outlet of both the exchangers as well as soil temperature at 2 m deep were continuously monitored.The experimental results confirmed that wetting the soil around EAHE improves the general heat exchange efficiency.The coefficient of cooling performance(COP)of the earth-to-air heat exchangers system was evaluated on the basis of the ratio between the heat removed from the air or added to the air and the energy input.During the day,with an average COP of 6.41,the WE system cooled the air more than the DE system,which reported a value of 5.07.On average,in the hottest hours of the day,the outlet temperature of the WE was 37.35℃ while in the DE it was 38.91℃.Moreover,during the nighttime,the WE system warmed the air more than the DE system.