Pioneering applications of refrigeration

J&E Hall Gold Medal Winner 2012 leading RAC innovator Pega Hrnjak of the University of Illinois where he is Professor at UIUC and Co-Director of their Air-Conditioning and Refrigeration Centre, one of the most prestigious research centres in the world. He also operates a commercial research facility (Creative Thermal Solutions) which carries out hands-on research on thermal systems ranging from nano-technology to large industrial equipment. There are 15 environmental chambers in a facility of 4,000 m2 with a staff of over 50 researchers. Between his academic job and his commercial job he has an exceptionally broad range of experience in addressing practical refrigeration problems and applying technical innovation to meet business problems. His paper will outline this inspirational work in the USA and internationally for which he was awarded the IOR's J&E Hall International Gold Medal for practical advancement of refrigeration in 20011-12. Pega states that refrigeration is a mature technology. Numerous smart and excellent scientist and engineers have been building the structure and knowledge in thermodynamics, fluid related areas, heat transfer, materials, compressors, auxiliaries etc… over a century so some think that in scientific and engineering sense refrigeration is a closed book. Needless to say we do not share that position, neither in scientific nor in engineering aspect of the statement. Numerous are examples to oppose assumption of exhausted creativity and invention in refrigeration: new compressor types (geometry and avoidance of lubricants), heat exchangers (microchannel and other new types), refrigerants (new environmentally friendly man made types and resurgence of natural refrigerants like CO2, ammonia, water,…), improved cycles, new control options, etc… The truth is that every new concept in refrigeration requires solid evaluation against well established and carefully optimized existing solutions which slows down the development process compared to new, emerging technologies. The paper presents some of authors pioneering concepts with emphasis on microchannel heat exchangers, evaporators in particular with flash gas bypass and periodic reverse flow.