# example 15-2 - Example 15-2 Subcooled liquid R134a enters a...

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Example 15-2 Subcooled liquid R134a enters a throttling valve at station 1 with a flow rate of 0.035 lbm/s, as shown. The liquid exits as a two-phase mixture at station 2. In the evaporator, the R134a exchanges heat with air flowing at 0.27 lbm/s. Using data on the figure, a) Find the temperature at station 2 b) Find the quality at station 2 c) Find the temperature at station 3 d) Determine whether station 3 is a two-phase mixture or a superheated vapor e) Calculate the heat transferred from the air to the R134a f) Sketch the process on a P-v diagram

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Solution: a) Across the throttling valve, the enthalpy is constant. 12 hh = 1 Btu enthalpy(R134a, 70, 55) 29.8 lbm hP T == = = At state 2, the pressure and enthalpy are known, so the state is fixed. The temperature is 2 temperature(R134a, 20, 29.8) TP h = o 2 2.43 F T =− b) State 2 is in the two-phase region. 2 =quality(R134a, 20, 29.8) xP h = = 2 =0.201 x c) Draw a control volume around the entire evaporator. The

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## This note was uploaded on 04/06/2009 for the course ENGR 2250 taught by Professor Borca-tasciuc during the Spring '08 term at Rensselaer Polytechnic Institute.

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example 15-2 - Example 15-2 Subcooled liquid R134a enters a...

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