A novel perspective on the performance analysis and design of an injection cooling system for liquid storage

Injection cooling has been used to store liquefied cryopropellants by reducing or eliminating the liquid boil-off due to ambient heat inleak. It involves subcooling of liquid by bubbling a gas through it. Previous studies on injection cooling attributed the cooling effect on liquid evaporation into the injected bubbles. However, a closer look into the process indicates that much higher gas flow rates than those used in the experiments are necessary to cause the observed liquid cooling. Hence, it is envisaged that the liquid evaporation into the ullage also dictates the liquid cooling. A novel theoretical approach has been presented to analyze the injection cooling system by developing a lumped parameter model that considers the liquid evaporation into both the bubbles and the ullage. Satisfactory validation of the proposed model, and a comparison between the surface evaporation and the bubble evaporation corroborate the significance of surface evaporation. Thus the present approach provides a better understanding of this process. To the authors’ best knowledge, the effect of the liquid evaporation into the ullage is being considered for the first time in analyzing this system. This finding is of critical importance in the design and development of injection cooling systems for liquid storage.