Studies show that the performance of transcritical R744 systems is highly sensitive to the high side pressure in the gas cooler. Hence use of appropriate strategy to control the high side pressure is essential to extract the best performance from these systems. In the present study, a R744 based air conditioning cycle with two expansion valves is considered for proper control of high side press...

This paper presents a distributed mathematical model for carbon dioxide direct expansion solar-assisted heat pump used to bath water. The main components are gas cooler, needle valve, an evaporator/collector, and compressor. To develop the exchange models, mass, energy, momentum balances were used. was validated transient as well steady state conditions using experimental data. A reasonably goo...

Despite widely used for the solution of one-dimensional subcritical flows governed by Saint-Venant's equations, the Preissmann's scheme cannot solve transcritical flows. This inability is due only to the solution methods created for non-transcritical flows. Transcritical transitions present specific properties which have to be adequately represented in the numerical method. A modified version o...

• A new refrigeration hybrid system of CO 2 subcooled by magnetic is presented. The hybridisation evaluated at environmental temperatures from 25 to 35 °C. Operation parameters the overall are optimized. Increments up 9.0% in COP obtained. Subcooling methods for transcritical plants being studied order improve behaviour these systems hot climates, where basic configurations not competitive enou...