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An adiabatic capillary tube is used in some refrigeration systems to drop the pressure of the refrigerant from the condenser level to the evaporator level. The R-134a enters the capillary tube as a saturated liquid at 50°C, and leaves at -12°C. Determine the quality of the refrigerant at the inlet of the evaporator.

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CPED

Answer:

The quality of refrigerant is 0.423

Explanation:

  • Adiabatic tubes drop the pressure from condenser level to evaporator level in refrigeration systems.
  • The values taken in this problem are from the saturated R-134a table.
  • All the calculation is attached in the image. In the problem, hf stands for the enthalpy of saturated liquid while hfg stands for enthalpy of saturated evaporation.
  • Both terms have units KJ/kg (kilo joule per kg).

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The quality of the refrigerant at the inlet of the evaporator is 0.422.

Given the following data:

  • Initial temperature = 50°C.
  • Final temperature = -12°C.

To determine the quality of the refrigerant at the inlet of the evaporator:

How to determine the quality.

Mathematically, the energy balance for this steady-flow system in the rate form is given by:

[tex]\Delta E_{sys}=E_{in}-E_{out}=0\\\\E_{in}=E_{out}\\\\mgh_1=mgh_2\\\\h_1=h_2[/tex]

From the refrigerant table, we have:

Inlet enthalpy: For a saturated liquid at [tex]T_1[/tex] = 50°C;

  • [tex]h_1=h_f[/tex] = 123.49 kJ/kg.

Exit quality: At [tex]T_1[/tex] = -12°C;

  • [tex]hf[/tex] = 35.92 kJ/kg
  • [tex]h_{fg}[/tex] = 207.38 kJ/kg.

Since the process is isophthalic, we would use this equation:

[tex]x=\frac{h_2 -h_f}{h_{fg}} \\\\x=\frac{123.49\; -\;35.92}{207.38 } \\\\x=\frac{87.57}{207.38 }[/tex]

x = 0.422.

Read more on refrigerants here: https://brainly.com/question/26395073

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