In this paper, the vapor-liquid-solid phase-equilibrium property of a mixed gas hydrate formed by the blend of CFC alternatives HFC152a/HCFC14lb is studied under a constant volume condition and the phase diagram of the mixed gas hydrate is presented first time. It has been shown that a cool-storage material with superior performance property can be achieved from the mixed refrigerant hydrate, due to the principle of property compensation of mixtures. The experimelltal result reveals that HFC152a/HCFC141b mixed gas hydrate has an azeotropic melting property This means that mixed gas hydrates can has phaseequilibrium properties similar to that of mixture vapor-liquid phase equilibrium and it may be described by means of the solution theory. This discovery is significant for understanding the formation and phase change of mixed gas hydrates and improvement of gas-hydratethermal-energy-storage materials.
In this study, the phase-equilibrium property of the mixed gas hydrate formed by an-other pair of CFC alternatives HFC152a/HCFC141b was measured under a constant volume condition. The phase diagrams of mixed gas hydrates and their characteristics were fur-ther studied, and the phase-equilibrium property of mixed gas hydrates comparing to that of simple gas hydrates was depicted and discussed. The experimental result reveals that HFC134a/HCFC141b mixed gas hydrate has a non-azeotropic melting property, which is different from that of HFC152a/HCFC141b[4]. The melt and freeze points are quite close because the decomposition temperatures of HFC134a and HCFC141b simple gas hydrates have small difference.
In this study, the formation and decomposition of the simple and mixed gas hydrates of CFC alternatives HFC134a, HFC152a and HCFC141b as well as their mixtures were tested with an enclosed cell, which was cooled within a low-temperature water bath. The results show that the formation temperature, pressure and speed of mixed gas hydrates are much better than those of simple gas hydrates. This means that one can get a phase-change cool-storage material which has superior thermodynamic and kinetic properties by using mixed gas hydrate formed by high-and low-pressure (active and inactive) refrigerant blends. HFC134a/HCFC141b and HFC152a/HCFC141b mixed gas hydrates has been found to be good cool storage materials which can be formed and decomposed at moderate pressure and appropriate temperature.
