Water spray heat transfer gas compression for compressed air energy system

Abstract

Compared with other types of energy storage systems, compressed air energy storage (CAES) system has the advantages of low cost, long life, and less impact on environmental. Low cycle efficiency limits its development. Enhancement of the heat transfer between air and environment to achieve isothermal compression is an effective method to improve the round trip efficiency of CAES systems. The spray heat exchange method is proposed to achieve isothermal compression. In order to obtain an accurate heat transfer process model, this paper takes into account that the process of water mist spreading from the nozzle to the whole cylinder will lead to local air and water mist heat transfer in the cylinder, and then divides the area in the cylinder into two parts to analyze and calculate the gas state. To verify the rationality of the diffusion model, a high-speed camera is used to observe the spray diffusion process. Meanwhile, the accuracy of the isothermal CAES system model is verified by literature experimental data, and finally the influence of water spray system parameters is obtained. The research results show that to gain fast heat transfer rate, a spray angle is equal to 60°; when the nozzle diameter is reduced from 0.6 mm to 0.4 mm, the compression efficiency of the system increases from 85.53 % to 89.25 %; The orthogonal design method is used to obtain the maximum total efficiency of the system under the given conditions, when the nozzle diameter is 0.6 mm and the water pressure is 0.2 MPa, and its value reaches 88 %. This research provides theoretical support for the in-cylinder spray isothermal CAES system.