Validation of cooling grid model and testing of alternatives

Abstract

[Abstract]: The Great Artesian Basin Sustainability Initiative, (GABSI), is a joint state and federal government project which rehabilitates artesian bores and replaces bore drains with polyethylene pipeline systems to tanks and troughs for stock water. The naturally pressurised artesian water can reach temperatures of up to 99°C due to the heat convection at great depths within the Earth’s crust. The heated artesian water is required to be cooled to below 45°C to prevent heat deterioration of the polyethylene pipe and to maintain a 50 year design life of the entire reticulation system. Historically, a submerged network of copper pipes has been designed for each system to provide a cooling mechanism and maintain the natural pressure of the bore. The project’s main aim was to predict and confirm the heat transfer parameters for cooling grids submerged in water and air, investigate alternative cooling options and validate the design model to accurately reflect existing operation. The testing procedure utilised a 12 metre length of the three pipe materials under investigation, which were tested at four representative flow rates surrounded by air and then submerged underwater. Inlet, outlet, ambient and pond temperatures were monitored along with relative humidity and weather observations. The experimental results and research allowed for model to be validated and deemed accurate with an appropriate factor of safety. The alternative designs tested were comparatively analysed accounting for costs, cooling performance, pipeline flow characteristics, material availability, corrosion resistance and maintenance requirements. Aluminium was determined to exhibit the most desirable traits and was recommended as the most suitable alternative cooling grid pipe material. Air as a heat transfer medium was deemed inappropriate for cooling artesian bore water because of the apparent lack of heat transfer.