Synergy effects and competition in nucleation and growth of R134a + TBAB binary hydrates

Single-component hydrate systems are often limited by sluggish nucleation kinetics and low cold storage density, which restrict their application in high-efficiency thermal energy storage systems. In this study, a binary hydrate formation method is proposed, leveraging the synergistic effect between tetrafluoroethane and tetra-n-butylammonium bromide to enhance nucleation and growth. By introducing composite guest molecules to stabilize the hydrate structure, the formation performance of the system was substantially improved. The effects of cooling rate on the induction time, hydrate yield, and formation rate were systematically evaluated under various cooling conditions for the R134a–TBAB binary system. Experimental results demonstrated that, compared to a single guest hydrate, the binary hydrate exhibited significantly enhanced kinetic behavior. Specifically, the induction time was reduced by 14.29%–28%, hydrate conversion increased by a factor of 1.72–2.95, and the hydrate formation rate was improved by 1.28–12.77 times. Furthermore, increased cooling rates enhanced the degree of supercooling, thereby providing a stronger thermodynamic driving force for nucleation and reducing the induction time by an additional 51.5%. In addition, a macroscopic behavior model for binary hydrate nucleation and growth was constructed based on visual experimental observations and Raman spectra. The results revealed that R134a and TBAB exhibit a three-layer stratified distribution at the liquid surface, and the nucleation mechanism is characterized by both competition and synergy between the two guest species. These findings elucidate the cooperative nucleation mechanism inherent in binary guest systems and offer new theoretical insights and design strategies for developing efficient hydrate-based cold storage technologies.