The Clean Air Act prohibited the production of

Chapter 10, Problem 10.66

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The Clean Air Act prohibited the production of chlo-rofluorocarbons (CFCs) in the United States as of1996. One widely used CFC, refrigerant R-12, hasbeen replaced by R-134a in many applications becauseof their similar properties, including a low boilingpoint at atmospheric pressure, Tsat?243 K and246.9 K for R-12 and R-134a, respectively. Comparethe performance of these two refrigerants under thefollowing conditions. The saturated refrigerant vaporat 310 K is condensed as it flows through a 30-mm-diameter, 0.8-m-long tube whose wall temperature ismaintained at 290 K. If vapor enters the tube at a flowrate of 0.010 kg/s, what is the rate of condensation andthe flow rate of vapor leaving the tube? The relevantproperties of R-12 at Tsat?310 K are ?v?50.1 kg/m3, hfg?160 kJ/kg, and ?v?150?10?7N?s/m2andthose of liquid R-12 at Tf?300 K are ?l?1306kg/m3, cp,l?978 J/kg?K, ?l?2.54 ?10?4N?s/m2,kl?0.072 W/m?K. The properties of the saturated R-134a vapor are ?v?46.1 kg/m3, hfg?166 kJ/kg,and ?v?136 ?10?7N?s/m2.