Temperature change across expansion valve?

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SUMMARY

The discussion focuses on the temperature and internal energy changes of Refrigerant 134-a as it passes through an expansion valve in a refrigeration system. The refrigerant enters at 160 psia as a saturated liquid with an initial temperature of 109.5 °F and exits at 30 psia. Participants emphasize the importance of determining the state of the refrigerant post-expansion, questioning whether it remains a saturated mixture or transitions to a superheated vapor. The first law of thermodynamics is highlighted as a critical concept for analyzing the flow situation.

PREREQUISITES
  • Understanding of thermodynamic properties of refrigerants
  • Familiarity with the first law of thermodynamics
  • Knowledge of property tables for Refrigerant 134-a
  • Concept of phase changes in refrigeration cycles
NEXT STEPS
  • Study the phase diagram of Refrigerant 134-a to identify states at different pressures
  • Learn about the first law of thermodynamics in flow processes
  • Explore the use of property tables for various refrigerants
  • Investigate the characteristics of superheated vapor versus saturated mixtures
USEFUL FOR

Students and professionals in thermodynamics, HVAC engineers, and anyone involved in refrigeration system design and analysis.

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Homework Statement


Refrigerant 134-a enters the expansion valve of a refrigeration system at 160 psia as a saturated liquid and leaves at 30 psia. Determine the temperature and internal energy changes across the valve.


Homework Equations



Δu=cv*ΔT

The Attempt at a Solution



I'm not sure how to get the temperature change. Since we know it is initially a saturated liquid, I was able to get the initial temperature from a property table to be 109.5 °F

Is there a way to tell if the refrigerant is a saturated mixture or a superheated vapor after the pressure change? Can we assume its a saturated mixture?
 
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Hint: Is there any work being done? Think first law for a flow situation.
 

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