Oil-free centrifugal refrigeration compressors: from HFC134a to HFO1234ze(E) Joost J. Brasz Danfoss Turbocor Compressors Inc. Syracuse University CASE Incubation Center 2-212 Center for Science and Technology Syracuse, New York 13244-4100 USA jbrasz@turbocor.com ABSTRACT The high global warming potential of HFC134a (GWP=1300) has led to the development of a new family of man-made refrigerants with much lower global warming potential. HFO1234ze(E) is one of those fluids. It has a GWP value of 7 and has been in commercial production as a blowing agent for a few years. Based on cost and availability this new fluid has been selected a potential candidate to replace HFC134a in commercial chillers. A new family of oil-free direct-drive centrifugal compressors with HFO1234ze(E) as working fluid has recently been introduced commercially, covering a cooling capacity range from 200 – 300 kWthermal. These new compressors are a spin-off of an existing platform of oil-free HFC134a products. Being oil-free eliminated oilrefrigerant compatibility issues, which were a major stumbling block during the transition from CFC12/HCFC22 towards HFC134a in the early 1990’s. Due to its somewhat lower pressure and vapor density HFO1234ze(E) requires in a slightly larger fluid module to achieve equal capacity as HFC134a. Impeller tip speed is reduced at equal temperature lift (=difference between condenser and evaporator saturation temperatures) as a result of the lower sonic velocity of HFO1234ze(E). Overall compressor efficiency improves as a consequence of these two effects. 1. INTRODUCTION During the nineties, the air-conditioning and refrigeration industry saw a transition from CFC’s towards HCFC’s and HFC’s. The main driver for this transition was the discovery of stratospheric ozone layer depletion by the chlorine atoms found in CFC’s and HCFC’s. After the resolution of the ozone layer depletion problem by the introduction of chlorine-free HFC refrigerants, the environmental concern started to focus on the global warming impact of these man-made refrigerants. Legislation intended to
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