Refrigeration Process: Freon 13 Heat Exchanger -25C, 1MPa

In summary, Freon 13 is used as a refrigerant in commercial refrigeration and enters a heat exchanger at 1 MPa and -25 degrees C. It absorbs 115 KJ of heat per kg and exits at the same temperature and pressure with a quality of 96%. The specific volume of saturated liquid Freon 13 at these conditions is 5% of the saturated vapor volume and the vapor phase is not ideal. The critical temperature and pressure of Freon 13 are 302 K and 4 MPa, respectively, with a molecular weight of 104.3 gm/mole. The enthalpy of vaporization process and the required pressure to maintain vapor-liquid equilibrium at a lower temperature of -30
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thermoA
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Homework Statement


Freon 13 is used as the refrigent in a commerical refrigeration process. At one point Freon 13 enters a heat exchanger at a pressure of 1 MPa and -25 degrees C. The liquid absorbs 115 KJ of heat per kg of Freon 13 entering the heat exchanger and exits at the same temp and pressure, but with a quality of 96%.

Specifice volume of saturated liquid Freon 13 at 1 MPa and -25 degrees C is 5% of the saturated capor volume at this pressure and temperature.
Also, vapor phase as these conditions is not an ideal gas.
Critical Temp is 302 K and critical pressure is 4 MPa. MW = 104.3 gm/mole.

Homework Equations


What is the enthalpy of vaporization process?
And if the operation temperature of Freon 13 in heat exchanger is lowered to -30 degrees C, what pressure would be required to stay on the saturation curve for vapor liquid equilibrium to carry out the evaporation at this new temperature?
 
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  • #2
The Attempt at a Solution I am not sure how to go about solving this problem. I know I must use the given values and equations, but I am not sure which equations I should use.
 
  • #3




The enthalpy of vaporization process can be calculated using the thermodynamic equation:

ΔHvap = Q/m

Where ΔHvap is the enthalpy of vaporization, Q is the heat absorbed per kg of Freon 13, and m is the mass of Freon 13. Plugging in the given values, we get:

ΔHvap = 115 kJ/kg

To determine the required pressure for the evaporation process at -30 degrees C, we can use the Clausius-Clapeyron equation:

ln(P2/P1) = ΔHvap/R * (1/T1 - 1/T2)

Where P1 and T1 are the initial pressure and temperature, and P2 and T2 are the new pressure and temperature. Rearranging the equation, we get:

P2 = P1 * e^(ΔHvap/R * (1/T1 - 1/T2))

Plugging in the given values, we get:

P2 = 1 MPa * e^(115 kJ/kg / (104.3 gm/mol * 8.314 J/mol*K) * (1/248 K - 1/243 K))

P2 = 1.034 MPa

Therefore, the pressure required for the evaporation process at -30 degrees C is approximately 1.034 MPa. This is slightly higher than the initial pressure of 1 MPa, indicating that a slight increase in pressure is needed to maintain the saturation curve for vapor-liquid equilibrium at the lower temperature.
 

Related to Refrigeration Process: Freon 13 Heat Exchanger -25C, 1MPa

What is the purpose of refrigeration process?

The purpose of the refrigeration process is to lower the temperature of a substance or space by removing heat energy through a heat exchanger.

What is Freon 13 and why is it used in refrigeration?

Freon 13, also known as R-13, is a colorless, odorless, and non-toxic refrigerant that has low flammability and toxicity levels. It is commonly used in refrigeration systems because of its high efficiency and low cost.

How does the heat exchanger work in the refrigeration process?

The heat exchanger is a device that transfers heat from one fluid to another without the two fluids mixing. In the refrigeration process, the heat exchanger removes heat from the substance being cooled and transfers it to the refrigerant, which then carries the heat away.

What temperature and pressure does the refrigeration process with Freon 13 operate at?

The refrigeration process with Freon 13 typically operates at a temperature of -25 degrees Celsius and a pressure of 1 megapascal (MPa).

What are the benefits of using Freon 13 in the refrigeration process?

Freon 13 has a low boiling point, making it ideal for use in low-temperature refrigeration systems. It is also non-corrosive and has a low toxicity level, making it safe for use in food refrigeration and other applications.

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