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In a vapour compression refrigeration cycle, the refrigerant enters the compressor in saturated vapour state at evaporator pressure, with specific enthalpy equal to 250 kJ/kg. The exit of the compressor is superheated at condenser pressure with specific enthalpy equal to 300 kJ/kg. At the condenser exit, the refrigerant is throttled to the evaporator pressure. The coefficient of performance (COP) of the cycle is 3. If the specific enthalpy of the saturated liquid at evaporator pressure is 50 kJ/kg, then the dryness fraction of the refrigerant at entry to evaporator is _________.
  • a)
    0.2
  • b)
    0.25
  • c)
    0.3
  • d)
    0.35
Correct answer is option 'B'. Can you explain this answer?
Most Upvoted Answer
In a vapour compression refrigeration cycle, the refrigerant enters th...
Given data:
- Specific enthalpy of refrigerant at evaporator entry (h1) = 250 kJ/kg
- Specific enthalpy of refrigerant at compressor exit (h2) = 300 kJ/kg
- Coefficient of performance (COP) = 3
- Specific enthalpy of saturated liquid at evaporator pressure (hf) = 50 kJ/kg

To find: Dryness fraction of the refrigerant at entry to evaporator

Approach:
- Using the COP formula, find the ratio of heat absorbed in evaporator to work done by compressor
- Use the refrigeration cycle diagram to find the specific enthalpy at condenser entry (h3) and evaporator exit (h4)
- Use the dryness fraction formula to find the required value

Calculation:
- COP = Heat absorbed in evaporator / Work done by compressor
- COP = (h2 - h1) / (h3 - h2)
- 3 = (300 - 250) / (h3 - 300)
- h3 = 450 kJ/kg
- Using the refrigeration cycle diagram, we know that h4 = hf = 50 kJ/kg
- Dryness fraction (x) = (h1 - hf) / (h4 - hf)
- x = (250 - 50) / (50 - hf) = 0.25 (Option B)

Therefore, the dryness fraction of the refrigerant at entry to evaporator is 0.25.
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Community Answer
In a vapour compression refrigeration cycle, the refrigerant enters th...


From equation (i),
100 = 50 + x(250 - 50)
x = 0.25
Hence, the correct option is (B).
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In a vapour compression refrigeration cycle, the refrigerant enters the compressor in saturated vapour state at evaporator pressure, with specific enthalpy equal to 250 kJ/kg. The exit of the compressor is superheated at condenser pressure with specific enthalpy equal to 300 kJ/kg. At the condenser exit, the refrigerant is throttled to the evaporator pressure. The coefficient of performance (COP) of the cycle is 3. If the specific enthalpy of the saturated liquid at evaporator pressure is 50 kJ/kg, then the dryness fraction of the refrigerant at entry to evaporator is _________.a)0.2b)0.25c)0.3d)0.35Correct answer is option 'B'. Can you explain this answer?
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In a vapour compression refrigeration cycle, the refrigerant enters the compressor in saturated vapour state at evaporator pressure, with specific enthalpy equal to 250 kJ/kg. The exit of the compressor is superheated at condenser pressure with specific enthalpy equal to 300 kJ/kg. At the condenser exit, the refrigerant is throttled to the evaporator pressure. The coefficient of performance (COP) of the cycle is 3. If the specific enthalpy of the saturated liquid at evaporator pressure is 50 kJ/kg, then the dryness fraction of the refrigerant at entry to evaporator is _________.a)0.2b)0.25c)0.3d)0.35Correct answer is option 'B'. Can you explain this answer? for Mechanical Engineering 2024 is part of Mechanical Engineering preparation. The Question and answers have been prepared according to the Mechanical Engineering exam syllabus. Information about In a vapour compression refrigeration cycle, the refrigerant enters the compressor in saturated vapour state at evaporator pressure, with specific enthalpy equal to 250 kJ/kg. The exit of the compressor is superheated at condenser pressure with specific enthalpy equal to 300 kJ/kg. At the condenser exit, the refrigerant is throttled to the evaporator pressure. The coefficient of performance (COP) of the cycle is 3. If the specific enthalpy of the saturated liquid at evaporator pressure is 50 kJ/kg, then the dryness fraction of the refrigerant at entry to evaporator is _________.a)0.2b)0.25c)0.3d)0.35Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for Mechanical Engineering 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for In a vapour compression refrigeration cycle, the refrigerant enters the compressor in saturated vapour state at evaporator pressure, with specific enthalpy equal to 250 kJ/kg. The exit of the compressor is superheated at condenser pressure with specific enthalpy equal to 300 kJ/kg. At the condenser exit, the refrigerant is throttled to the evaporator pressure. The coefficient of performance (COP) of the cycle is 3. If the specific enthalpy of the saturated liquid at evaporator pressure is 50 kJ/kg, then the dryness fraction of the refrigerant at entry to evaporator is _________.a)0.2b)0.25c)0.3d)0.35Correct answer is option 'B'. Can you explain this answer?.
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