Division of Information Technology, Engineering and the Environment
School of Advanced Manufacturing and Mechanical Engineering
School of Advanced Manufacturing and Mechanical Engineering
Thesis Abstract
Ground Air Heat Exchangers (GAHE’s) are not a new phenomenon insofar as the animal kingdom along with our forebears, have been using them for millennia in the form of caves. Caves that had both high and low openings had a draft in one or the opposite direction whenever the temperature outside was different to the cave temperature. Indeed, a reversal of air flow could have been experienced within the same 24 hours. This display and experience of the natural forces of nature at work is still to this day being experienced by many around the world.
Today, the use of natural or forced convection and GAHE’s utilises the same vast resource of the earth’s crust as a thermal bank in a minimalistic way. In its basic form, after setting up the system, the only power required for forced convection to take place is a fan and a sump pump on a periodic basis.
Research of ground temperature manipulation has previously been confined to the surface of the Earth. Thus, natural events and processes dictated outcomes for the Ground Heat Exchanger (GHE) except where grass was grown and in a temperate climate it was watered regularly to keep it fresh. The challenge now for humankind where water is and becoming a scarce commodity, is to be able to sustain sufficient vegetation on the surface to provide enough shade to reduce the soil surface and resulting subterranean soil temperature, without increasing the thermal diffusivity of the soil/air interface by increasing its moisture content. For horizontal GHE’s this aspect of subterranean soil temperature manipulation appears to have been overlooked as a result of the high values of thermal diffusivities associated with an abundance of water availability.
The proposed engineering solution for an improved energy transfer to and from the ground applies to both Ground Water Heat Exchangers (GWHE’s) and Ground Air Heat Exchangers (GAHE’s).
The research is primarily aimed at dwellings but the concept proposed will be useful on all infrastructures such as offices, factories and animal husbandry buildings requiring moderated temperatures at reduced cost to the environment and consumers.
My work will address this issue by irrigating the Ground Air Heat Exchanger’s (GAHE’s) pipework immediate surround of saturated quartz sand contained in a polyethylene impermeable membrane seal welded envelope. This envelope is further encased within the unexcavated main body of soil deep underground.
