Design, construction and testing of an air-cycle refrigeration system for road transport Stephen W.T. Spence a, * , W. John Doran b , David W. Artt a a School of Mechanical and Manufacturing Engineering, Queen’s University Belfast, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland b School of Engineering, Letterkenny Institute of Technology, Port Road, Letterkenny, Co., Donegal, Ireland Received 9 September 2003; received in revised form 5 February 2004; accepted 18 February 2004 Abstract The environmental attractions of air-cycle refrigeration are considerable. Following a thermodynamic design analysis, an air- cycle demonstrator plant was constructed within the restricted physical envelope of an existing Thermo King SL200 trailer refrigeration unit. This unique plant operated satisfactorily, delivering sustainable cooling for refrigerated trailers using a completely natural and safe working fluid. The full load capacity of the air-cycle unit at 2 20 8C was 7,8 kW, 8% greater than the equivalent vapour-cycle unit, but the fuel consumption of the air-cycle plant was excessively high. However, at part load operation the disparity in fuel consumption dropped from approximately 200% to around 80%. The components used in the air- cycle demonstrator were not optimised and considerable potential exists for efficiency improvements, possibly to the point where the air-cycle system could rival the efficiency of the standard vapour-cycle system at part-load operation, which represents the biggest proportion of operating time for most units. q 2004 Elsevier Ltd and IIR. All rights reserved. Keywords: Design; Construction; Air conditioner; Refrigerated transport; Thermodynamic cycle; Air; Centrifuge compressor; Turbine expander Syste `me frigorifique a ` cycle a ` air pour le transport routier: conception, fabrication et essais Mots-cle ´s: Conception; Fabrication; Conditionneur d’air; Transport frigorifique; Cycle thermodynamique; Air; Compresseur centrifuge; Turbine a ` de ´tente 1. Introduction The current legislative pressure on conventional refriger- ants is well known. The reason why vapour-cycle refrigeration is preferred over air-cycle refrigeration is simply that in the great majority of cases vapour-cycle is the most energy efficient option. Consequently, as soon as alternative systems, such as non-HFC refrigerants or air- cycle systems are considered, the issue of increased energy consumption arises immediately. Concerns over legislation affecting HFC refrigerants and the desire to improve long-term system reliability led to the examination of the feasibility of an air-cycle system for refrigerated transport. With the support of Enterprise Ireland 0140-7007/$35.00 q 2004 Elsevier Ltd and IIR. All rights reserved. doi:10.1016/j.ijrefrig.2004.02.003 International Journal of Refrigeration 27 (2004) 503–510 www.elsevier.com/locate/ijrefrig * Corresponding author. E-mail address: s.w.spence@qub.ac.uk (S.W.T. Spence). Abbreviations: COP, coefficient of performance; CAU, cold air unit; QUB, Queen’s University of Belfast; LYIT, Letterkenny Institute of Technology.