Steam Jet Refrigeration Cycle
Chemical Engineering and Processing 41 (2002) 551– 561 www.elsevier.com/locate/cep Evaluation of steam jet ejectors
Hisham El-Dessouky *, Hisham Ettouney, Imad Alatiqi, Ghada Al-Nuwaibit
Department of Chemical Engineering, College of Engineering and Petroleum, Kuwait Uni6ersity, P.O. Box 5969, Safat 13060, Kuwait
Received 4 April 2001; received in revised form 26 September 2001; accepted 27 September 2001
Abstract
Steam jet ejectors are an essential part in refrigeration and air conditioning, desalination, petroleum refining, petrochemical and chemical industries. The ejectors form an integral part of distillation columns, condensers and other heat exchange processes. In this study, semi-empirical models are developed for design and rating of steam jet ejectors. The model gives the entrainment ratio as a function of the expansion ratio and the pressures of the entrained vapor, motive steam and compressed vapor. Also, correlations are developed for the motive steam pressure at the nozzle exit as a function of the evaporator and condenser pressures and the area ratios as a function of the entrainment ratio and the stream pressures. This allows for full design of the ejector, where defining the ejector load and the pressures of the motive steam, evaporator and condenser gives the entrainment ratio, the motive steam pressure at the nozzle outlet and the cross section areas of the diffuser and the nozzle. The developed correlations are based on large database that includes manufacturer design data and experimental data. The model includes correlations for the choked flow with compression ratios above 1.8. In addition, a correlation is provided for the non-choked flow with compression ratios below 1.8. The values of the coefficient of determination (R 2) are 0.85 and 0.78 for the choked and non-choked flow correlations, respectively. As for the correlations for the motive steam pressure at the nozzle outlet and the area ratios, all have R 2 values above
Hisham El-Dessouky *, Hisham Ettouney, Imad Alatiqi, Ghada Al-Nuwaibit
Department of Chemical Engineering, College of Engineering and Petroleum, Kuwait Uni6ersity, P.O. Box 5969, Safat 13060, Kuwait
Received 4 April 2001; received in revised form 26 September 2001; accepted 27 September 2001
Abstract
Steam jet ejectors are an essential part in refrigeration and air conditioning, desalination, petroleum refining, petrochemical and chemical industries. The ejectors form an integral part of distillation columns, condensers and other heat exchange processes. In this study, semi-empirical models are developed for design and rating of steam jet ejectors. The model gives the entrainment ratio as a function of the expansion ratio and the pressures of the entrained vapor, motive steam and compressed vapor. Also, correlations are developed for the motive steam pressure at the nozzle exit as a function of the evaporator and condenser pressures and the area ratios as a function of the entrainment ratio and the stream pressures. This allows for full design of the ejector, where defining the ejector load and the pressures of the motive steam, evaporator and condenser gives the entrainment ratio, the motive steam pressure at the nozzle outlet and the cross section areas of the diffuser and the nozzle. The developed correlations are based on large database that includes manufacturer design data and experimental data. The model includes correlations for the choked flow with compression ratios above 1.8. In addition, a correlation is provided for the non-choked flow with compression ratios below 1.8. The values of the coefficient of determination (R 2) are 0.85 and 0.78 for the choked and non-choked flow correlations, respectively. As for the correlations for the motive steam pressure at the nozzle outlet and the area ratios, all have R 2 values above
References: [1] E.E. Ludwig, Applied Process Design for Chemical and Petrochemical Plants, vol. 1, second ed, Gulf, Houston, TX, 1977. [2] R.B. Power, Hydrocarb. Proc. 43 (1964) 138. Eng. 20 (1999) 52 – 68. [4] J.T. Munday, D.F. Bagster, A new ejector theory to steam jet refrigeration, IEC 16 (1977) 442 – 449. 64 (1942) 85 – 91. Refrig. 18 (1995) 378 – 385. ejector refrigeration cycle, Int. J. Energy Res. 20 (1996) 871 – 885. [10] N.H. Aly, A. Karmeldin, M.M. Shamloul, Modelling and simulation of steam jet ejectors, Desalination 123 (1999) 1 – 8. with moveable primary nozzle, Int. J. Refrig. 20 (1997) 352 – 358. Conference on Chemical Engineering, Brisbane, 4 – 7 September, 1983. [15] D. Sun, Variable geometry ejectors and their applications in ejector refrigeration systems, Energy 21 (1996) 919 – 929. Therm. Fluid Sci. 15 (1997) 384 – 394. [19] N. Al-Khalidy, Performance of solar refrigerant ejector refrigerating machine, ASHRAE Trans. 103 (1997) 56 – 64. Trans. 104 (1998) 153 – 160. J. Refrig. 13 (1990a) 351 – 356. 13 (1990b) 357 – 363. ASHRAE Trans. 101 (1995) 383 – 391. Astronaut. 2 (1994) 915 – 920. jet refrigeration systems, Chem. Eng. J. 45 (1990) 99 – 110. (1998) 1827 – 1834. Inst. Chem. Eng. 27 (1996) 91 – 100. [31] M.L. Tomasek, R. Radermacher, Analysis of a domestic refrigerator cycle with an ejector, ASHRAE Trans. 1 (1995) 1431 – 1438. (2000) 213 – 226. Convers. Manag. 40 (1999) 873 – 884. jet ejector, Chem. Eng. J. 18 (1979) 81 – 85.