IMPACT OF GROUND COVER ON THE EFFICIENCIES OF EARTH-TO-AIR HEAT-EXCHANGERS

The influence of different ground surface boundary conditions on the e fficiency of a single earth-to-air heat exchanger as well as of a mult iple parallel earth tubes system has been investigated The cooling pot ential of both these systems buried under bare soil has been assessed and compared with the cooling potential of the same systems buried und er short-grass covered soil. The results revealed that soil surface co uld be a controllable factor for the improvement of the performance of earth-to-air heat exchangers. The cooling system consists of a single tube or multiple tubes, buried in the ground and through which ambien t or indoor air is circulated and cooled: it is then mixed with the in door air of a building or an agricultural greenhouse. An accurate nume rical model has been used to assess the dynamic thermal performances a nd operational limits of the earth-to-air heat exchangers. Finally, a sensitivity investigation was carried out in order to evaluate the eff ect of the main design parameters on the system's cooling capacity. Cu mulative frequency distributions of the air temperature at the pipe's exit have been developed as a function of the input parameters.