Abstract: A steam ejecter refrigeration cycle system consisting of an ejector, an evaporator, a generator, and a condenser was established. The effects of different constant diameters of the diffuser on the pumping performance of the ejector were investigated. When the throat diameter of the diffuser is increased from 24 mm to 28 mm, the entrainment ratio of the ejector is significantly increased, the pumping efficiency is improved, but the critical back pressure of the ejector is reduced. The effect of the constant diameter of the diffuser on the pumping performance of the ejector under different operating parameters was also analyzed. The results show that with the increase of working steam pressure, the entrainment ratio increases first and then decreases. When the pressure reaches 0.36MPa, the maximum entrainment ratio of the ejector is 0.53. The entrainment ratio remains constant when the back pressure is less than the critical back pressure. When the back pressure is greater than the critical back pressure, the entrainment ratio is reduced to zero until the back pressure is 7000Pa. There is an optimum constant diameter of diffuser to maximize the ejector pumping efficiency under certain operating parameters. In actual design and production, it is necessary to take into account both the exhaust efficiency and the ultimate exhaust capacity of the ejector.

Key words: ejector, diffuser, constant diameter, entrainment ratio, experimental investigation