Refrigerants and energy efficiency

Abstract

Environmental concerns ( i.e. ozone depletion and greenhouse warming) are forcing major shifts from traditional choices of refrigerant working fluids for individual systems and for specific applications. Energy efficiency has taken on new urgency to mitigate fossil fuel demands and the associated effects on greenhouse warming while allowing for future growth of refrigerant demand. Energy efficiency has thus become an increasingly important parameter and a key focus in the refrigerant selection process. Efforts to generically rank refrigerants with respect to their inherent thermodynamic efficiencies have thus far not proven to be very productive. Much conflicting information has surfaced as to the true impacts on energy demand of various candidate fluids. It is apparent that much more than a simple thermodynamic cycle efficiency is involved. Other factors may have an equal or even greater impact on the ultimate energy demands associated with any particular working fluid and/or system design. Even calorimeter testing may prove misleading in the absence of appropriate optimization. This paper discusses individual sources of inefficiency inherent in every real system and attempts to define key fluid characteristics associated with optimizing or degrading the effectiveness of individual system components and the overall system. Relative compressor efficiencies, heat transfer effectiveness, pressure drop impacts, etc., will be addressed.