Research on the heat and mass transfer mechanisms for growth of hydrate shell from gas bubbles

As a fundamental study for hydrate utilization technologies, hydrate growth is a complicated rate-limiting process controlled by heat and mass transfer mechanisms. Generally, the experimental data of hydrate shell lateral growth in the literature are compiled based on the system subcooling, while those of hydrate shell vertical growth are compiled based on the molecular mobility of the hydrate formers and water. In this study, we quantitatively investigate the dominating factors for hydrate film growth considering the opposite mass or heat transfer limitations, which can explain the observed phenomena from the literature more comprehensively. Firstly, a model is derived to describe the lateral growth of hydrate shell considering the convective mass transfer and effective concentration driving force at the film front. It can demonstrate the important effects of subcooling and other system factors such as gas type, aqueous solution, and system pressure on hydrate shell lateral growth. Secondly, an improved self-similar model is presented to simulate the process of hydrate shell thickening considering the heat transfer limitation. The simulation results indicate that the hydrate shell growth rate decreases with a decrease in the subcooling and an increase in the bubble radius.