Download Heat Transfer Comparison in Coaxial Tube in Tube Heat Exchanger

Heat Transfer Comparison in Coaxial Tube in Tube Heat Exchanger
Operating with Refrigerants R407C and R22
Vladimir Soldo
Tonko Curko
Marino Grozdek
Faculty of Mechanical Engineering and
Naval Architecture
Department of Thermodynamics,
Thermal and Processing Technology
University of Zagreb
ABSTRACT
Due to hazardous environmental impact of the CFC and HCFC refrigerants that
are currently used in R&AC systems, in accordance with the Montreal Protocol, actual is
exchange of those by new, ecologically acceptable, HFC refrigerants. Therefore system
performance analyses was made where the single component refrigerant R22 was
replaced with zeotropic mixture R407C.
In the system operating at the same conditions, a comparison of heat transfer in
coaxial exchanger for R22 and R407C is performed. Experimental data are presented in
the form of average heat transfer coefficients as a function of heat flux and mass flux.
Results have showed that in the heat exchange process with R407C refrigerant heat
transfer coefficient is lower (10-35 %) than for R22. As R407C is a blend of three pure
refrigerants (R32, R125 and R134a) with temperature glide of 5-7 °C, the concentration
shift occurs during two-phase flow in the condenser and evaporator.