Investigation of seasonal behaviour of a vertical ground source heat pump used in residential air conditioning systems

A significant section of world energy consumption is attributable to domestic heating and cooling. Heat pumps are preferred and widely used in many applications due to their high utilization efficiencies compared to conventional heating and cooling systems. Ground source heat pump (GSHP) systems are usually used for heating or cooling of commercial and residential buildings. Because the temperature of the soil is almost stable during the year, the use of these types of heat pumps (HPs) is very attractive economically and environmentally. These HPs can use the soil as either a heat source for heating or as a heat sink for cooling. Using this resource, the GSHP transfers heat from the soil to the building in winter or from the building to the soil in summer.In this study, vertical drilling of borehole was performed for three different depths (30, 60, and 90 m) in garden of a heated and cooled village house in Elazig, Turkey. First, a thermal response test for determining the thermal conductivity and thermal resistance of the geologic formation, where the vertical ground heat exchangers were buried, was carried out. The vertical type single U-borehole heat exchangers were linked with a GSHP unit which was placed in a house and manufactured with the national facilities. In this way, this house was both heated and cooled. The effect of the depth of borehole coupled to heat exchanger on the thermal system performance was experimentally investigated. Furthermore, the exergetic efficiencies of the GSHP system were determined as a function of the borehole depth for cooling and heating seasons. Besides, our goal is to model the behaviour of thermally conductive bentonite grouts surrounding U-shaped pipes in this work. For this aim, finite element analysis was performed to evaluate the heat transfer in the complete pipe-grout formation associated with U-tube ground heat exchangers. In the last chapter of the thesis, a comparison of artificial neural network (ANN) and adaptive neuro fuzzy inference systems (ANFIS) is presented for modelling the GSHP. In this section, the system performance was predicted by using water-antifreeze solution and air (condenser inlet and outlet) temperatures. In conclusion, ANFIS for the quantitative modeling of GSHP systems has been shown as more suitable estimation method.According to the results of the cooling and heating experiments, it is proved that the best performance of system has been obtained for the heat exchanger system with depth of 90 m. If the drilling cost is reduced and heat pump equipments could be produced by the national technology completely, these systems will provide great benefits in our country.Key Words: Ground source heat pump, experimentally performance, thermal response test, finite element method, artificial neural network, adaptive neuro fuzzy inference systems.