A study on thermodynamic coupling in dynamic injection and production processes of compressed air energy storage

Energy storage, as a pivotal technology supporting the energy revolution, is a strategic emerging industry in China, poised for rapid and substantial growth. Within salt cavern compressed air energy storage systems, the flow and heat transfer of compressed air in the wellbore are essential for accurately predicting the thermodynamic behavior within the cavern. This study focuses on the thermal coupling effects within the wellbore-cavern system, employing an interdisciplinary approach to develop a wellbore-cavern airflow thermal coupling model. The model comprehensively accounts for the thermodynamic properties of real gases and successfully predicts the spatiotemporal variations and thermodynamic responses of flow and thermal parameters by integrating characteristic equations—such as Reynolds number, Prandtl number, Grashof number, and Nusselt number—with one-dimensional Euler motion differential equations and both steady-state and transient heat conduction differential equations. The study reveals that as the length of the wellbore increases, the outlet pressure and temperature rise significantly, leading to corresponding increases in pressure, temperature, and wall temperature within the cavern. Under varying gas injection mass flow rates, the thermodynamic parameters of the wellbore and cavern exhibit significant changes, with injection temperature having a particularly pronounced effect. The research findings provide scientific theoretical support for the efficient, stable, and safe operation of salt cavern energy storage systems.