Experimental study on a new type of water storage tank for geothermal heating

Abstract

To enhance the utilization of geothermal energy in a geothermal heating and energy storage coupling system, a new water storage tank is proposed. The tank's structure comprises a horizontally designed multi-slot form with a flow equalizing plate positioned in the middle. Subsequently, an experimental system for evaluating the water storage tank's performance was designed, and a test rig was established. The study aimed to explore the thermocline's thickness variation using three distinct flow equalizing plate structures–uniform shunt, middle shunt, and side shunt—and examine the heat storage/release performance under different operational conditions. Concurrently, the applicability of the water storage tank's structure under various heat storage conditions was assessed. The findings revealed the following: (1) Under identical working conditions, the new tank displayed a thermocline's thickness proportion to the tank's height, ranging from 20.25% to 33.75%, lower than that of a traditional water storage tank. This indicates a superior temperature stratification performance for the new water storage tank. (2) At an inlet cross-sectional velocity of <0.40 m/s, the side shunt flow equalizing plate resulted in the thinnest thermocline's thickness. Conversely, with an inlet cross-sectional velocity of ≥0.40 m/s, the uniform shunt flow equalizing plate optimized the temperature stratification performance. (3) Higher initial temperatures in the tank led to reduced total heat storage and release, along with a decline in the heat release/storage ratio. For initial temperatures of 30°C, 35°C, and 40°C, the water storage tank exhibited heat release/storage ratios of 95.11%, 93.07%, and 92.04%, respectively, surpassing those of a traditional water storage tank.