For the sustainable use of low-temperature geothermal resources, it is essential to understand heat transfer in the geological environment of the planned geothermal system. At the microscopic level, correct identification of the influence of the physical parameters of the sediments including mineral composition, porosity, water content, density and grain size distribution is required. But also at the macroscopic level, hydrological conditions such as the presence of groundwater, hydraulic conductivity and dispersivity are the initial parameters that need to be considered. What influence do the physical parameters of the sediments and the hydrogeological conditions have on the thermal properties of the sediments and heat transfer? Is the correct determination of matrix thermal conductivity important for the analytical and numerical models that define the temperature distribution of groundwater in the vicinity of an open-loop systems? If properly addressed, these questions can make an important contribution to the understanding of heat transport in the studied intergranular aquifer of Murska Sobota. In this dissertation, we studied at the microscopic the relationship between the physical parameters and thermal properties of the sediment, that influence the potential for the use of low-temperature geothermal resources. By establishing the analytical and numerical model of groundwater flow and heat transfer in a selected shallow aquifer, we were able to study these relationships on a macroscopic level. Based on two sets of samples with parameters determined in the laboratory, we were able to define appropriate analytical thermal conductivity models based on different sediment types and accurately determine the matrix thermal conductivity. Based on 2-years field observations in NE Slovenia, we were able to evaluate the influence of the physical parameters measured in the laboratory compared to the influence of the individual parameters on the temperature distribution including natural conditions. We found out that in our study area, the most important parameter influencing groundwater temperature distribution around open-loop systems is hydraulic conductivity. The thermal parameters measured in the laboratory, did not have a significant influence on the groundwater temperature at the macroscopic level.
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