Energy efficiency improvement in the refrigeration cycle using Internal Heat Exchanger – a new approach / J. Müller // W: 23rd IIR International Congress of Refrigeration : Refrigeration for Sustainable ... więcej

Energy efficiency improvement in the refrigeration cycle using Internal Heat Exchanger – a new approach / J. Müller // W: 23rd IIR International Congress of Refrigeration : Refrigeration for Sustainable Development : proceedings, Prague, Czech Republic, August 21-26, 2011 = 23e Congrès International du Froid de l'IIF : Le froid pour le dèveloppment durable [Dokument elektroniczny]. – Paris : International Institute of Refrigeration, 2011. – Dysk optyczny CD. – (Proceedings of the 23rd IIR International Congress of Refrigeration, ISSN 1025-9031 ; 23). – 10 s. – Oznaczenie ref./art.: 354. – Bibliogr. 22 poz. – ISBN 978-2-913149-88-5 (CD). – ISBN 978-1-61839-748-5 (print). – ISBN 978-2-913-149-89-2 (USB)

The aim of the paper is to present a refrigeration cycle modified by using an internal heat exchanger (IHX). The idea of an IHX is not new but in this case a new approach is applied. For different refrigerants ... więcej

The aim of the paper is to present a refrigeration cycle modified by using an internal heat exchanger (IHX). The idea of an IHX is not new but in this case a new approach is applied. For different refrigerants the net effect of using an IHX is either positive or negative due to refrigerant properties. Not only properties have influence on energy effect of IHX, working conditions are also very important. One of the disadvantages of applying the IHX is superheating the refrigerant vapor at the compressor inlet. This has a negative effect – for many refrigerants – i.e. an increase of the specific work of compression and receiving high discharge temperature. A simple solution – wet vapor of refrigerant at the inlet of IHX – improves the cycle in various aspects. First, the evaporator performance is much better when not superheating the vapor. The end part of the heat exchange area can be more effectively used. Second, the vapor at the compressor inlet can be only slightly superheated which prevents too high compressor discharge temperature and does not increase the specific work of the compressor. Third, we obtain a “pure” effect of subcooling the refrigerant liquid at the inlet of the expansion valve resulting in an increased specific heat of evaporation. For zeotropic mixtures with temperature glide during the phase change significant subcooling results in lowering the evaporating temperature without lowering the pressure in the evaporator. Last but not least, energy efficiency of refrigeration (EER) can be improved for some refrigerants and for specific working conditions. Together with theoretical evaluation of this concept some experimental data are presented. Commonly used refrigerants were evaluated theoretically and tested in a 10 kW (cooling capacity) test rig. R22, R407C, and zeotropic mixture including R744 were analyzed.