Estimation of vapour liquid equilibria for the system carbon dioxide–difluoromethane using artificial neural networks

In this paper, an alternate tool, i.e. the artificial neural network technique has been applied for estimation of vapour liquid equilibria (VLE) for the binary system, carbon dioxide–difluoromethane, which is an attractive alternative to chlorofluorocarbons and hydrochlorofluorocarbons, normally used as refrigerants. The model can satisfactorily estimate the vapour liquid equilibrium pressure and mole fraction carbon dioxide in vapour phase in the temperature range 222.04–343.23 K and in the pressure range 0.105–7.46 MPa. The average absolute error for the system in the estimation of vapour phase mole fraction is 0.0086 and 0.056 MPa for the pressure.     

Vapour–liquid equilibrium data for the difluoromethane+1,1,1,2,3,3,3-heptafluoropropane system at temperatures from 283.20 to 343.38 K and pressures up to 4.5 MPa

Isothermal vapour–liquid equilibrium data for the difluoromethane (R32)-1,1,1,2,3,3,3-Heptafluoropropane (R227ea) binary system are presented at 283.20, 303.21, 323.21 and 343.38 K and pressures up to 4.5 MPa. The experimental method, used for this work, is of the static-analytic type. It takes advantage of mobile pneumatic capillary samplers (Rolsi™, Armines’ patent) developed in our laboratory. The four P, x, y isothermal data have been represented with the Soave–Redlich–Kwong (SRK) equation of state and the MHV1 rules involving the NRTL model.     

Thermodynamic analysis of a liquid-flooded Ericsson cycle cooler

A novel approach to implementing a gas Ericsson cycle heat pump was developed. The concept, termed a liquid-flooded Ericsson cooler (LFEC), uses liquid flooding of the compressor and expander to approach isothermal compression and expansion processes. Analytical models of liquid-flooded compression and expansion processes were developed using ideal gas, constant specific heat, and incompressible liquid assumptions. Special considerations for use of positive displacement compressors with fixed volume ratios are detailed. The unique behavior of a liquid-flooded compressor was explored, including the discovery of an optimum liquid flooding rate that minimizes compression power. A computer model of the LFEC cycle was developed using ideal gas, incompressible liquid, and constant specific heat assumptions. The model was used for a thorough parametric study. The purpose of the study was to explore the feasibility of the concept, identify the optimum operating parameters, and to provide a basis for the design of an experimental system.