G. Mihalakakou et al., THE INFLUENCE OF DIFFERENT GROUND COVERS ON THE HEATING POTENTIAL OF EARTH-TO-AIR HEAT-EXCHANGERS, Renewable energy, 7(1), 1996, pp. 33-46
Ten years' hourly measurements of air and ground temperature values at
various depths below bare and short grass soil at Dublin Airport have
been used in order to investigate the impact of different ground surf
ace boundary conditions on the efficiency of a single and a multiple p
arallel earth-to-air heat exchanger system. The heating potential of b
oth these systems buried under bare soil has been assessed and compare
d with the heating potential of the same systems buried under short-gr
ass-covered soil. The results of this comparison revealed that soil su
rface cover might be a significant controllable factor for the improve
ment of the performance of earth-to-air heat exchangers. The heating s
ystem consists of a single pipe or multiple parallel pipes laid horizo
ntally, through which ambient or indoor air is propelled and heated by
the bulk temperature of the natural ground. The dynamic thermal perfo
rmance of these systems during the winter period and their operational
limits have been calculated using an accurate numerical model. Finall
y, a sensitivity analysis was performed in order to investigate the ef
fect of the main design parameters, such as pipe length, pipe radius,
air velocity inside the tube and the depth of the buried pipe below th
e earth's surface, on the system heating capacity. Cumulative frequenc
y distributions of the air temperature at the pipe's exit have been de
veloped as a function of the main input parameters.