Numerical analysis of heat gain to geothermal heat exchangers with moisture evaporation in the structure

Abstract

Relevance. Provisions on the need to transition to alternative energy sources and energy security, reduction of environmental emissions and energy conservation in various industries can largely rely on the use of geothermal energy. A separate area in the field of modeling geothermal technologies is the study of thermal regimes of geothermal heat exchangers. The need to ensure reliable thermal contact between the geothermal heat exchanger and its environment leads to the use of a variety of backfills, including pre-moistened ones. Aim. Study of the intensification of heat supply to geothermal heat exchangers, taking into account the influence of moisture evaporation in its backfill, its characteristics and operating conditions of the systems under consideration. Methods. The solution to the problem was obtained by the finite difference method. An implicit difference scheme and sweep algorithm were used. The coordinate step ranged from 1 to 10 mm. Results and conclusions. Study was carried out for six months of continuous operation of a geothermal heat exchanger. When analyzing the thermal conditions of the system under consideration, the main attention was paid to the study of the intensification of heat supply to the geothermal heat exchanger, taking into account the influence of moisture evaporation in its backfill, its characteristics and operating conditions of the systems under consideration. It has been established that an increase in the humidity of the sand backfill of a geothermal heat exchanger leads to a growth in heat inflows by 3.2–7.8%. A significant influence of the unsteadiness of transfer processes on the intensification of heat transfer in the system under consideration was revealed. It was shown that the increase in heat flow to the geothermal heat exchanger due to the presence of evaporation is about 22%. The conclusion is substantiated that when choosing an option for regulating the thermal conditions of geothermal heat exchangers, the volumetric humidity of the sand backfill should be primarily changed.

Keywords

• geothermal energy
• geothermal heat exchanger
• mathematical modeling
• heat gain
• evaporation