Statistical-thermodynamics modeling of clathrate-hydrate-forming systems suitable as working media of a hydrate-based refrigeration system

Attempts to develop a novel hydrate-based refrigeration system have been carried out in recent years. It was reported that the vapor/liquid/liquid/ hydrate four-phase equilibrium conditions in the systems of cyclopentane and water plus difluoromethane satisfy the required conditions of the working media of a hydrate-based refrigeration system for residential air-conditioning use. When a statistical- thermodynamic model is applied to the above-mentioned hydrate-forming systems, the Kihara potential parameters of these guest substances need to be determined. In this study, an attempt was made to determine the Kihara potential parameters of difluoromethane and cyclopentane based on phase equilibrium data for difluoromethane + water, cyclopentane + water, and difluoromethane + cyclopentane + water systems. The absolute average deviations of the predicted equilibrium pressure at a given temperature from the corresponding experimental values are 0.043 for the HFC-32 + water system, 0.12 for the cyclopentane + water, and 0.031 for the HFC-32 + cyclopentane + water.