This project was carried out in the period from 2003 to 2004 as a joint research and development at University of Nottingham, United Kingdom, in cooperation with ERTC and Odessa State Academy of Refrigeration, Ukraine, in the area of ejector refrigerating technologies, supported by the CANMET Energy Technology Centre of Ottawa, Canada.
The aims of this project are to investigate an experimental elector refrigeration machine (ERM) designed to test the suitability of R236fa as a working fluid, for general ERM applications that utilise low-grade heat (Tg < 100 °C) as their motive power. In addition the experimental ERM was designed to test several new innovations, including:
- Novel ejector designs.
- The optimum mixing chamber entry angle and area ratio.
- The performance of a new design of suction chamber with double flow entry.
- The performance benefits of adding a pre-cooler and a recuperator into the jet pump cycle.
Refrigerant R236fa was selected by University of Nottingham because of its zero ODP and GWP values, non-toxicity and non-flammability. R236fa also it has the benefit of a positively-sloped saturated-vapour line in the thermodynamic T-s diagram, which means that during expansion through the nozzle condensation losses are prevented.
Figure 1. Photograph of the ejector test rig
The photograph of experimental test rig assembly designed by ERTC team is shown in Figure 1. The ejector test rig equipment includes the following major components: a water heater (providing a heat source), a vapor generator, a separator, an ejector, an evaporator, a condenser, a feed pump, a recuperator, and a precooler. Brazed plate heat exchangers were used as generator, evaporator and condenser. "Tube-in-tube" heat exchangers with low pressure resistance were used as recuperator and precooler. The design of the generator heating system was based on the thermo-siphon principle.
Figure 2. Photograph of the experimental ejector with replaceable nozzle and mixing chamber
A photograph of the experimental ejector assembly with two retrofract symmetrical suction inlet ducts is shown in Figure 2. The assembly of the ejector consists of the following main components: a body, an axially movable supersonic nozzle, a mixing chamber made jointly with the diffuser, a frame and a mechanism to move the nozzle into optimal position with respect to the entrance of the mixing chamber. Special mechanism for assembling the primary nozzle with the diffuser was designed to allowed the distance between the nozzle exit and the mixing chamber inlet to be adjusted in order to study its influence on ejector performance.
Ejector and ERM experimental investigations was carried out with supersonic nozzle, cylindrical and conical-cylindrical mixing chambers, that was designed by ERTC, and conoidal mixing chamber, designed with Constant Rate of Momentum Change (CRMC) method by University of Nottingham.
Experimental investigations was carried out in wide range of operating conditions and ejector geometrical characteristics. Later, University of Nottingham investigate R245fa as a refrigerant for this experimental ERM. The main results of a theoretical and experimental investigation of the performance characteristics of an ejector and an ejector refrigeration machine operating with refrigerants R236fa and R245fa at design and off-design working conditions are presented in articles and abstracts on international conferences (see list below).
- Eames I.W., Petrenko V.O., Ablwaifa A.E. Design and experimental investigation of a jet pump refrigerator // Proceedings of 3rd International conference on Heat Powered Cycles, HPC 2004. – 11th-13th October, 2004. – Larnaca, Cyprus.
- Ablwaifa A.E. A Theoretical and experimental investigation of jet-pump refrigeration. PhD thesis, Nottingham University. - 2006.
- Eames I.W., Ablwaifa A.E., Petrenko V.O. Results of an experimental study of an advanced jet-pump refrigerator operating with R245fa // Applied Thermal Engineering. – 2007. – Vol. 27, Issue 17-18. – pp. 2833-2840.
- Petrenko V.O., Volovyk O.S. Design and development of automated ejector refrigeration machines, operating with low boiling refrigerants. J. Refrigeration Engineering and Technology, ¹1 (105), pp.41-47, 2007 (in Russian).
- Petrenko V.O., Volovyk O.S. Analysis of performance characteristics of ejector refrigeration machine operating at design and off-design conditions. J. Refrigeration Engineering and Technology, ¹2 (106), pp.25-30, 2007 (in Russian)
- Ablwaifa A.E., Eames I.W., Petrenko V.O. Experimental validation of CFD model used to design jet-pumps // International seminar on ejector/jet-pump technology and application, EUROTHERM SEMINAR ¹85. – September 7-9, 2009. – Louvain-la-Neuve, Belgium.