Thermo-hydraulic performance of a cryogenic printed circuit heat exchanger for liquid air energy storage

The liquid air energy storage assisted by liquefied natural gas is a promising large-scale storage method, but its development is limited by the lack of thermo-hydraulic data on the cryogenic printed circuit heat exchanger. A simplified model for conjugate heat transfer was built and solved by a commercial code FLUENT 14.5. Model validation was conducted by comparing results with experimental data. The nature of flow and heat transfer was revealed by quantifying the vortex strength and visualizing the vortex core. The influence of the inclined angle was investigated, and the Nusselt number and friction factor correlations for the best angle were developed. The minimum internal temperature approach for optimum system operation is approximately 6 K, located in the middle of the heat exchanger. Results indicate that the evolution of Dean vortices plays a crucial part in the augmentation of heat transfer. The secondary flow caused by elbows forces the fluid cores to strike the windward side periodically, which disturbs the boundary layer and enhances the fluid mixing. Entropy production analysis shows that the thermal entropy generation has a dominant share of total irreversibility. The best performance is achieved at an inclined angle of 45 degrees since the irreversibility is reduced by augmenting the heat transfer.

Automated summary

The thermo-hydraulic behavior of a cryogenic printed circuit heat exchanger in the liquid air energy storage assisted by liquefied natural gas was investigated. A simplified model was built and solved using the FLUENT software, and its accuracy was validated against experimental data. The study revealed the importance of Dean vortices and secondary flow in enhancing heat transfer.