SA-96-02-2 -- Thermodynamic optimisation of evaporators with zeotropic refrigerant mixtures PDF

The need to evaluate design changes, aimed at improving the energy efficiency of existing systems, has been identified by several studies related to the replacement of refrigerant R22 (Didion 1994). Zeotropic (or nonazeotropic) refrigerant blends are attractive replacements because of their low ozone depletion potential (ODP) and global warming potential (GWP) values, as well as promising thermodynamic characteristics. Zeotropes experience a variable temperature glide during isobaric phase changes. This, combined with changes in evaporator design can lead to a better match between the temperature glides of the refrigerant and the external fluid, reducing heat exchanger irreversibilities and increasing system performance. Investigates the effect of evaporator design on performance. An irreversibility-based function was selected to quantify the penalties associated with various designs, and was evaluated with an experimentally validated computer simulation of the evaporator developed as part of this study (Ragazzi 1995).

KEYWORDS: year 1996, thermodynamics, optimisation, evaporators, non-azeotropic, refrigerants, mixtures, heat flow, pressure drop, comparing, cross flow heat exchangers, counterflow heat exchangers, R407C, R22, temperature difference