Conference Year



Ejector, Isobutane, Experimental Results


The paper describes experimental and numerical investigation of ejection refrigeration system dedicated for short time storage of food products for local retail market, especially in rural areas. This work was sponsored by US Dept. of Agriculture under Phase I SBIR program. This novel method does not use electricity and is cleaner for the environment than other refrigeration techniques. One of the crucial problems of the retail market of perishable foodstuff is a lack of efficient and appropriate refrigerated storage capacity. The existing technology in most cases uses conventional refrigeration systems that consume a large amount of electricity, they are expensive as well as use harmful working substances (usually artificial GHG gases that have high greenhouse warming potential in comparison with most of the natural substances). In addition, ensuring required storage conditions in terms of the stability of the product temperature and humidity may be a challenge for most of the existing short time storage refrigerators.  Responding to these challenges we developed an ejector based refrigeration system that 1) utilizes solar or waste heat (below 100C temperature) as a main source of energy, 2) eliminates the mechanical compressor, which is a main user of electricity and the main contributor to maintenance and reliability issues in cooling systems and 3) operates without any ozone depletion effects and any greenhouse gas (GHG) emissions, when used with natural refrigerants. Until recently, ejector use in refrigeration systems was considered as controversial because most of the research conducted in the past has yielded only theoretical results without visible, commercial products. The main issue was a relatively low value of coefficient of performance (COP) in comparison with classical compression systems. Selection of the working fluid for the refrigeration or air-conditioning system is the crucial problem because the system efficiency is strongly influenced by the thermodynamic properties of the refrigerant. We found that the maximum efficiency can be achieved with natural refrigerants, of which isobutane is by far the most favorable. However, primarily due to its flammable nature, isobutane is not currently allowed in commercial systems in USA and Canada although it has been used for many years in all domestic refrigerators in Germany and other EU countries where appropriate safety precautions and regulations were developed. For US market, we identified two other environmentally friendly equivalents to isobutane: R245fa and R1234ze both with zero ozone depletion potential. The research described here had overcome another limitation - a lack of appropriate methods for the design of ejector geometry. Such methodology was developed and tested in a variety of thermodynamic cycles for cooling, heating and heat pumps. The test stand and the experimental results of investigation for isobutane as a working fluid along with CFD modelling results are shown and discussed in the paper in details.Â