THE IMPACT OF EJECTOR CHARACTERISTICS ON THE OPERATION AND PERFORMANCE OF A CONVENTIONAL REFRIGERATION CYCLE

摘要

Ejectors used in refrigeration systems as compression components, alone or in combination with compressors, have gained renewed interest from the scientific community as means of low temperature heat recovery and more efficient energy use. A 1-D mathematical model, using the forward marching solution technique and the NIST database of refrigerants properties was developed for analysis and optimized ejector design in refrigeration cycles. Two program versions coded in FORTRAN were written for design and simulation respectively. Ejector operation and cycle overall performance were then studied in a large range of working conditions, using the refrigerants R141 b for validation purposes, R142 b and R22 for ejector and cycle applications in typical refrigeration conditions. Local distributions of relevant parameters, including the temperature, the pressure and the Mach number were calculated at any position along the ejector length. Operation parameters such as the entrainment ratio ω, the compression ratios P_(ex)/P_e and P_g/P_(ex) or the geometric ratio (D/d)~2 were found to be very important for ejector design. Hybrid ejector-compressor cycle configurations have been assessed. The ejector location in the cycle was shown to play a crucial role in the overall cycle performance.