Testing of the oil-immersed sensible heat storage unit with circular channel solid heat body under charging modes with different heat transfer temperature difference

Heat storage technology can enrich and store dispersed and discontinuous heat and significantly improve energy efficiency. This paper reports a pilot-scale sensible heat storage unit, which uses circular channel solid made of castables as the heat storage bodies and heat transfer oil as the working fluid. When performing, the heat transfer oil passes through the flow channel of the heat storage body and is in direct contact with the heat storage body for heat exchange. The experiment explores the unit's thermal performance, including heat, power, and charge energy efficiency under different charging temperature difference modes. At the same time, the normalized charge energy efficiency is used to evaluate the heat-storage unit's heat absorption capacity during the charging process. The results show that the average heat storage capacity of the heat storage body is about 1.10 x 10(6) kJ, accounting for 89% of the heat storage capacity of the unit, and the remaining 11% is the heat stored in the oil inside the unit. In addition, the charging mode with step temperature rise used in the experiment can make the heat stored by the regenerator increase linearly with time. The charging mode with a more considerable temperature difference can significantly enhance the charging power and shorten the charging time, but the increase in the temperature difference reduces the efficiency of the charging process. The efficiency in the experimental range is reduced from 64.5% in the minimum temperature difference mode to 34.8% in the maximum temperature difference mode. This paper has a certain supplementary function for the design and application of heat storage and the evaluation of the thermal performance of the heat storage unit.