Liquid-gas heat transfer characteristics of near isothermal compressed air energy storage based on Spray Injection

Isothermal compressed air energy storage (I-CAES) could achieve high roundtrip efficiency (RTE) with low carbon emissions. Heat transfer enhancement is the key to achieve I-CAES, thus the liquid-gas heat transfer characteristics of near I-CAES system based on spray injection was analyzed in this paper. The liquid-gas heat transfer model and thermodynamic model were established and the effects of design variables on heat transfer rate and energy efficiency were analyzed. The results showed that spray injection can produce considerable heat transfer capacity and effectively suppress air temperature change, but spray injection at initial compression stage will not bring much heat transfer enhancement. Increasing spray flow rate shifts the dominant heat transfer contribution from water bulk to spray heat transfer and increases total heat transfer rate and RTE, however the increase effect of spray injection is more obvious in small-scale CAES. Low water flow rate and large working cylinder volume are recommended to achieve slow compression and expansion processes with enough liquid-gas heat transfer duration, realizing near I-CAES with high RTE. High air storage pressure increases heat transfer rate, but deviates CAES from isothermal system, resulting in low RTE. This research will provide scientific basis for heat transfer enhancement, system design and performance optimization of I-CAES.