Temperature change across expansion valve?

In summary, the problem involves finding the temperature and internal energy changes of Refrigerant 134-a as it passes through an expansion valve. The refrigerant enters at 160 psia as a saturated liquid and exits at 30 psia. Using the first law for a flow situation, we can determine the temperature change by using the specific heat at constant volume (cv) and the change in internal energy. However, it is unclear if the refrigerant is a saturated mixture or a superheated vapor after the pressure change.
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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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  • #2
Hint: Is there any work being done? Think first law for a flow situation.
 

1. What is the purpose of an expansion valve?

The expansion valve is a crucial component in a refrigeration or air conditioning system. It controls the flow of refrigerant into the evaporator, which allows for the refrigerant to expand and absorb heat from the surrounding air.

2. How does an expansion valve work?

An expansion valve works by controlling the amount of refrigerant that enters the evaporator. It does this through a small opening that can be adjusted to regulate the flow of refrigerant. As the refrigerant passes through this opening, it rapidly expands and cools, allowing it to absorb heat from the surrounding air.

3. What are the types of expansion valves?

There are several types of expansion valves, including capillary tube, thermostatic expansion valve, electronic expansion valve, and automatic expansion valve. Each type has its own unique design and method of regulating refrigerant flow.

4. What are the signs of a faulty expansion valve?

A faulty expansion valve can cause various issues in a refrigeration or air conditioning system, including reduced cooling capacity, uneven cooling, and increased energy consumption. Other signs may include frost or ice buildup on the evaporator coil, strange noises, or leaking refrigerant.

5. Can an expansion valve be repaired?

In most cases, an expansion valve can be repaired by a trained technician. However, if the valve is severely damaged or corroded, it may need to be replaced. Regular maintenance and cleaning of the expansion valve can help prevent the need for costly repairs or replacements.

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