Evaluation of CO2-doped blends in single-stage with IHX and parallel compression refrigeration architectures.

CO 2 is the standard for medium to large-sized commercial applications, as it combines security and low environmental impact. However, it requires the use of advanced and complex cycles. Recently, CO 2 -doping (the addition of a small quantity of another fluid) has attracted scientific attention, as when CO 2 is mixed with fluids with higher critical temperatures, the optimum operation moves to subcritical, providing COP increments in relation to pure-CO 2 operation. This work, from a theoretical perspective, evaluates CO 2 -doping with the fluids R-152a, R-1234yf, R-1234ze(E) and R-1233zd(E) considering the two most used CO 2 cycles: the base cycle with an internal heat exchanger (IHX) and the cycle with parallel compression (PC), fractionation taking place. The work analyses the COP improvements for an evaporating level of -10 °C and from 10 to 40 °C of environment temperature. Predicted maximum COP increments reach up to 5.8% for the IHX cycle and 10.0% for the PC cycle. [ABSTRACT FROM AUTHOR]