| Groundwater source heat pumps （GWSHP） are widely used to develop shallow geothermal resources in the recent years. The dissertation started from the basic theory of groundwater flow and heat transport, set up a groundwater flow and heat transport coupled model for Zhengzhou City with the limited difference simulation software HST3D, and simulated impact of several factors on groundwater temperature field, including the hydro-geological conditions of the aquifers, structure of the production wells, pumping and injection volumes of groundwater. The distance of the pumping-injection wells, the pumping volume and the mode of pumping and injection in different layers are the main factors influencing the groundwater temperature field.Based on analysis of the geological condictions of Zhengzhou for sustainable development of shallow geothermal resources, the dissertation set up a 3D flow-heat coupled model for a typical groundwater source heat pump project in the Zhengzhou Children Hospital, calibrated the model’s hydro-geological parameters with the observed water-level and temperature data, and used the calibrated model to predict the change of groundwater temperature field in the future five years after 2008. The simulation results showed that, the model could well describe the hydro-geological conditions and the strata’s thermal physical features of the study area; the change of temperature in the aquifers were relatively remarkable, and the heat peak moved very fast and the influence radius were large in the aquifers, while the temperature in the clay layers changed slightly and slowly. The temperature in the pumping well rose slightly in five years with the current pumping volume. The system’s efficiency didn’t be upgraded under the alternate pumping-injection mode for the existence of regional groundwater flow, but the efficiency can be improved if the distance between the pumping and injection wells increase. These results could provide reliable reference for scientific management of the groundwater source heat pump project.The dissertation employed the analytic hierarchy process and spatial analysis software to carry out suitability assessment on application of groundwater source heat pump systems in Zhengzhou, and divided Zhengzhou into four sub-regions, which were respectively unsuitable sub-region, normal suitable sub-region, relatively suitable sub-region and very suitable sub-region. The suitability division result was maily affected by the water-bearing of the aquifers and their lithology. The very suitable sub-region, the relatively suitable sub-region and the normal suitable sub-region were 5.397×107m2,4.996×108m2 and 4.150×108m2 respectively.Based on the suitability assessment, the dissertation used the simulation method to determine the optimal distance between the pumping well and the injection well in different sub-regions, and used the geothermal reserve method and the water quantity convertion method to calculate the reserve of the shallow geothermal resources in Zhengzhou and the safe yield of shallow geothermal resources by groundwater source heat pumps. The reserve of the shallow geothermal resources in Zhengzhou within the depth of 200m was 3.5072×1015kJ; and the safe yield by means of groundwater source heat pumps in the suitable sub-regions was 2.1165×1014kJ, under the condition of extracting 5℃energy and the system running for 120 days respectively in winter and summer. |
