Trans-critical vapor compression cycle using butane (R600) as refrigerant for industrial waste heat recovery.

Abstract

By utilizing a trans-critical vapor compression cycle using hydrocarbons, the operating range of these natural refrigerants with low global warming potential and zero ozone depletion potential can be extended to higher temperature levels. A single-stage cycle using a reciprocating (suction gas cooled) compressor and an internal heat exchanger for suction gas superheating has been modeled using Modelica and the TIL thermal component library. The simulation model has been validated by means of experimental data gathered with a R600 test rig operated at condensing temperatures up to 110°C. The simulation model was modified to study the system behavior in trans-critical operation. Increasing the suction gas superheat lowers the values for the high-side pressure at which the maximum efficiency is reached, which could be utilized if the high-side pressure is limited by the used components. Through the application of an internal heat exchanger, the increase of superheat shows potential to increase the Coefficient of Performance (COP).