Supersonic two-phase flow of CO_2 through converging-diverging nozzles for the ejector refrigeration cycle

摘要

CO_2 is environmentally friendly, safe and more suitable to ejector refrigeration cycle than to vapor compression cycle. Supersonic two-phase flow of CO_2 in the diverging sections of rectangular converging-diverging nozzles was investigated. The divergence angles with significant variation of decompression were 0.076°, 0.153°, 0.306° and 0.612°. This paper presents experimental decompression phenomena which can be used in designing nozzles and an assessment of Isentropic Homogeneous Equilibrium (IHE). Inlet conditions around 6-9 MPa, 20-37℃ were used to resemble ejector nozzles of coolers and heat pumps. For inlet temperature around 37℃, throat decompression boiling from the saturated liquid line, supersonic decompression and IHE solution were obtained for the two large divergence angles. For divergence angles larger than 0.306°, decompression curves for inlet temperature above 35℃ approached IHE curves. For divergence angles smaller than 0.306° or for nozzles with inlet temperature below 35℃, IHE had no solution.