Investigation of a novel ejector expansion refrigeration system using the working fluid R134a and its potential substitute R1234yf

• A new ejector-expansion refrigeration system with two evaporators is presented.
• The cycle analysis is performed using a small number of data and assumptions.
• The effects of the ejector geometry and the condenser temperature are investigated.
• The performance of R1234yf and R134a in the ejector cycle is compared.
• The ejector cycle has an important improvement in COP for both R134a and R1234yf.

To overcome the constraints related to the steady-state operation of the ejector and the separator in a basic ejector-expansion refrigeration system, a new refrigeration system with two evaporators using an ejector as a throttling valve is presented. A constant-area mixing model for the ejector requiring a small number of data and assumptions was established to perform a thermodynamic cycle analysis of the new system. The effects of the ejector area ratio and the condenser temperature on the performance of the ejector and therefore on the increase in COP of the new system compared to the conventional bi-evaporator refrigeration system were investigated for the same cooling capacities of the two evaporators. The refrigerants R134a and its substitute R1234yf were tested. It was found that the novel system has an important improvement in COP for both R134a and R1234yf. This increase in COP is higher for R1234yf especially at high condensing temperatures.