Experimental study on the thermodynamic performance of a novel tetrabutylammonium bromide hydrate cold storage system

Abstract

Clathrate hydrates with huge phase change latent heat are rapidly becoming a key means of improving and replacing current cold storage technologies. Efficient hydrate cold storage systems play a pivotal role in achieving carbon peaks. This study proposes a novel hydrate cold storage system, with a hydrate-on-coil component and an internal circulating gas disturbance device- and investigates the cold storage characteristics. In this study, comparative analyses of the tetrabutylammonium bromide (TBAB) hydrate cooling rate, cooling capacity, and energy storage ratio outside the hydrate-on-coil were conducted for various values of the coolant inlet temperature, flow rate, and gas disturbance, and the in situ formation morphology of TBAB hydrates outside the hydrate-on-coil were recorded. The results indicated that internal circulating gas disturbance achieved the double promotion effect of enhanced heat transfer and promoted hydrate phase change, which led to a significant increase in cooling capacity. Gas disturbance boosted the cooling capacity by approximately 20% to more than 80% of the theoretical cooling capacity. A theoretical cooling capacity of 86% was achieved at a storage temperature of 1 °C. Notably, gas disturbance could reduce the cooling capacity due to the increase in coolant temperature and the decrease in flow rate. The hydrate packing factor reached 79.5%, and the system energy storage efficiency was maintained at over 85%. Furthermore, the form of hydrate accumulation outside the hydrate-on-coil was influenced by natural convection and bubble uplift (forced convection). These two types of heat transfer affected the hydrate accumulation pattern and cold storage process. The insights gained from this study may provide important experimental support and a reference for the application and improvement of cold storage technology.