Možnosti optimalizace vystrojení vrtaných tepelných výměníků sloužících jako primární okruh tepelných čerpadel země-voda.

Abstract

New concept of the completion of the borehole heat exchangers which are designed for ground-coupled heat pumps utilization is presented in this dissertation thesis. This concept is based on selective grouting of rock environment segments. The segmentation of the underground is based on analytical and numerical models of geothermal and geothermodynamic processes in the upper zones of earth crust. This study is focused mainly on the campus of the VŠB-TU Ostrava. Conducted approach very well simulates the real processes such as radiogenic heat production, underground temperature changes due to the climate changes in the last centuries and also the yearly atmospheric temperature oscillations influence in the surficial ground zone. Following parts cover theory of the borehole heat exchanger completion in which the crucial role belongs to the grout that fills the annulus of the borehole. The influence of this and also other completion parameters on the ability of the borehole heat exchanger to produce the thermal energy – the borehole thermal resistance, is introduced as well. The analysis shows that the grout thermal conductivity of 2,5 W·m-1·K-1 is the reasonable value of which the further improvement will not significantly affect thermal production. Natural ingredients were added to the basic grout to improve it‘s thermal conductivity in the laboratories of Department of Applied Geology of the Institute of Geological Engineering. Developed grouts cover the thermal conductivity range of 0,59~3,43 W·m-1·K-1. The application of all grouts, but one with the natural graphite addition is feasible, from the reduced borehole length or increased thermal productivity point of view. The performance of the segmentally grouted borehole exchanger is evaluated by means of the numerical model. This models physical setting is verified by the field data for the underground heat storage process and by the analytical model for the heat production task. The presented results evaluating the concept of borehole heat exchanger completion by the grouting segmentation show certain potential in some specific conditions.