关键词: 储热系统, 单双级, 氨水, 再吸收循环, COP, 出水温度, 驱动热源温度

Abstract:

A heat storage system based on the double-stage resorption cycle with ammonia water as working medium was constructed and its thermodynamic performance was evaluated.The system stores energy relying on the concentration difference of its solution.The concentration of the solution at the resorption circle high-pressure absorber outlet fluctuates with the circulating operating pressure.There are lower limits for the circulating operating pressure under different solution concentrations.When the mass fraction of the concentrated side solution is as low as 0.9，the circulating operating pressure should not be lower than 4.6 kPa.However，low concentration of the solution at the absorber outlet will hamper the normal operation of the cycle.Based on the feasible concentration-temperature range of the resorption heat storage cycle，a throttling failure threshold is proposed as the criterion for effective cooling capacity of refrigerant.The difference between a resorption cycle and an absorption cycle is that the former one takes the binary solution absorption process instead of the unary refrigerant condensation process， so the heat source temperature of the resorption cycle can be effectively reduced. The conclusions are drawn on the performance analysis.When the heat source temperature is 90 ℃，the COP of a single-stage resorption cycle can be 0.614，and the COP of a double-stage resorption cycle can be 0.489.When the inlet temperature is 30 ℃，the outlet temperature of the system taking single-stage heat storage mode can reach 49.38 ℃，and that taking double-stage heat storage mode can reach 52.54 ℃.The system can meet the requirements of floor heating.

Key words: double-stage, ammonia water, resorption cycle, COP, outlet temperature, heat source temperature