Refrigeration Written Test Questions and Answers

This set of Refrigeration written test Questions & Answers focuses on “Multiple Evaporators and Compressor System – 2”.

1. What is the value of enthalpy when refrigerant enters the compressor, i.e., point 1?

a) m₁ h₁₁ + m₂ h₈ + m₃ h₅ / (m₁ + m₂ – m₃)
b) m₁ h₁₁ + m₂ h₈ + m₃ h₅ / (m₁ – m₂ + m₃)
c) m₁ h₁₁ + m₂ h₈ + m₃ h₅ / (m₁ + m₂ + m₃)
d) m₁ h₅ + m₂ h₅ + m₃ h₄ / (m₁ + m₂ + m₃)
View Answer

Answer: c
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁₁ – h₁₀
m₂ = 210 Q₂ / h₈ – h₇
m₃ = 210 Q₃ / h₅ – h₄
At point 1, mass of refrigerant coming from each evaporator is converging.
So, (m₁ + m₂ + m₃) h₁ = m₁ h₁₁ + m₂ h₈ + m₃ h₅
h₁ = m₁ h₁₁ + m₂ h₈ + m₃ h₅ / (m₁ + m₂ + m₃).

2. What is the value of the refrigeration effect in the following arrangement?

a) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₁) + m₃ (h₅ – h₂)
b) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄)
c) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₂) + m₃ (h₂ – h₄)
d) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₁ – h₄)
View Answer

Answer: b
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁₁ – h₁₀
m₂ = 210 Q₂ / h₈ – h₇
m₃ = 210 Q₃ / h₅ – h₄
So, Refrigeration effect across EP₁ = m₁ (h₁₁ – h₁₀)
Refrigeration effect across EP₂ = m₂ (h₈ – h₇)
Refrigeration effect across EP₃ = m₃ (h₅ – h₄)
Total refrigeration effect produced in the system is the summation of refrigeration effect across each evaporator.
Total refrigeration effect = m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄) = 210 (Q₁ + Q₂ + Q₃).

3. What is the value of C.O.P. in the following arrangement?

a) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄) / (m₁ + m₂ + m₃) (h₂ – h₃)
b) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄) / (m₁ + m₂ + m₃) (h₂ – h₇)
c) m₁ (h₁₁ – h₁₀) + m₃ (h₈ – h₇) + m₂ (h₅ – h₄) / (m₁ + m₂ + m₃) (h₂ – h₁)
d) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄) / (m₁ + m₂ + m₃) (h₂ – h₁)
View Answer

Answer: d
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁₁ – h₁₀
m₂ = 210 Q₂ / h₈ – h₇
m₃ = 210 Q₃ / h₅ – h₄
So, Refrigeration effect across EP₁ = m₁ (h₁₁ – h₁₀)
Refrigeration effect across EP₂ = m₂ (h₈ – h₇)
Refrigeration effect across EP₃ = m₃ (h₅ – h₄)
Total refrigeration effect produced in the system is the summation of refrigeration effect across each evaporator.
Total refrigeration effect = m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄) = 210 (Q₁ + Q₂ + Q₃)
Work = (m₁ + m₂ + m₃) (h₂ – h₁)
C.O.P. = Total refrigeration effect / Work
= m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄) / (m₁ + m₂ + m₃) (h₂ – h₁)
= 210 (Q₁ + Q₂ + Q₃) / (m₁ + m₂ + m₃) (h₂ – h₁).

4. What is the value of enthalpy when refrigerant enters the compressor, i.e., point 1?

a) m_e1 h₁₁ + m_e2 h₉ + m_e3 h₆ / (m_e1 + m_e2 + m_e3)
b) m_e1 h₁₁ + m_e2 h₉ + m_e3 h₅ / (m_e1 + m_e2 + m_e3)
c) m_e1 h₁₁ + m_e2 h₈ + m_e3 h₆ / (m_e1 + m_e2 + m_e3)
d) m₁ h₅ + m₂ h₅ + m₃ h₄ / (m₁ + m₂ + m₃)
View Answer

Answer: a
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = m_e1 = 210 Q₁ / h₁₁ – h₁₀
m₂ = 210 Q₂ / h₉ – h₇, m_e2 = m₂ + m_e1 (x₇ / 1 – x₇)
m₃ = 210 Q₃ / h₆ – h₄, m_e3 = m₃ + (m_e1 + m_e2) (x₄ / 1 – x₄)
At point 1, mass of refrigerant coming from each evaporator is converging.
So, (m_e1 + m_e2 + m_e3) h₁ = m_e1 h₁₁ + m_e2 h₉ + m_e3 h₆
h₁ = m_e1 h₁₁ + m_e2 h₉ + m_e3 h₆ / (m_e1 + m_e2 + m_e3).

5. What is the value of the refrigeration effect in the following arrangement?

a) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₁) + m₃ (h₅ – h₂)
b) m₁ (h₁₁ – h₁₀) + m₂ (h₉ – h₇) + m₃ (h₆ – h₄)
c) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₂) + m₃ (h₂ – h₄)
d) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₁ – h₄)
View Answer

Answer: b
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁₁ – h₁₀
m₂ = 210 Q₂ / h₉ – h₇
m₃ = 210 Q₃ / h₆ – h₄
So, Refrigeration effect across EP₁ = m₁ (h₁₁ – h₁₀)
Refrigeration effect across EP₂ = m₂ (h₉ – h7)
Refrigeration effect across EP₃ = m₃ (h6 – h₄)
Total refrigeration effect produced in the system is the summation of refrigeration effect across each evaporator.
Total refrigeration effect = m₁ (h₁₁ – h₁₀) + m₂ (h₉ – h₇) + m₃ (h₆ – h₄) = 210 (Q₁ + Q₂ + Q₃).

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6. What is the value of C.O.P. in the following arrangement?

a) m₁ (h₁₁ – h₁₀) + m₂ (h₉ – h₇) + m₃ (h₆ – h₄) / (m_e1 + m_e2 + m_e3) (h₂ – h₁)
b) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄) / (m₁ + m₂ + m₃) (h₂ – h₇)
c) m₁ (h₁₁ – h₁₀) + m₂ (h₉ – h₇) + m₃ (h₆ – h₁) / (m_e1 + m_e2 + m_e3) (h₂ – h₈)
d) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄) / (m₁ + m₂ + m₃) (h₂ – h₁)
View Answer

Answer: a
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁₁ – h₁₀
m₂ = 210 Q₂ / h₉ – h₇
m₃ = 210 Q₃ / h₆ – h₄
So, Refrigeration effect across EP₁ = m₁ (h₁₁ – h₁₀)
Refrigeration effect across EP₂ = m₂ (h₉ – h₇)
Refrigeration effect across EP₃ = m₃ (h₆ – h₄)
Total refrigeration effect produced in the system is the summation of refrigeration effect across each evaporator.
Total refrigeration effect = m₁ (h₁₁ – h₁₀) + m₂ (h₉ – h₇) + m₃ (h₆ – h₄) = 210 (Q₁ + Q₂ + Q₃)
Work = (m_e1 + m_e2 + m_e3) (h₂ – h₁)
C.O.P. = Total refrigeration effect / Work
= m₁ (h₁₁ – h₁₀) + m₂ (h₉ – h₇) + m₃ (h₆ – h₄) / (m_e1 + m_e2 + m_e3) (h₂ – h₁)
= 210 (Q₁ + Q₂ + Q₃) / (m_e1 + m_e2 + m_e2) (h₂ – h₁).

7. What is the value of the refrigeration effect in the following arrangement?

a) m₁ (h₁ – h₁₀) + m₂ (h₈ – h₁) + m₃ (h₅ – h₂)
b) m₁ (h₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄)
c) m₁ (h₁ – h₁₀) + m₂ (h₃ – h₉) + m₃ (h₅ – h₈)
d) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₁ – h₄)
View Answer

Answer: c
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁ – h₁₀
m₂ = 210 Q₂ / h₃ – h₉
m₃ = 210 Q₃ / h₅ – h₈
So, Refrigeration effect across EP₁ = m₁ (h₁ – h₁₀)
Refrigeration effect across EP₂ = m₂ (h₃ – h₉)
Refrigeration effect across EP₃ = m₃ (h₅ – h₈)
Total refrigeration effect produced in the system is the summation of refrigeration effect across each evaporator.
Total refrigeration effect = m₁ (h₁ – h₁₀) + m₂ (h₃ – h₉) + m₃ (h₅ – h₈) = 210 (Q₁ + Q₂ + Q₃).

8. What is the value of total power required to run the following arrangement?

a) m₁ (h₂ – h₁) + m₃ (h₄ – h₃) + m₂ (h₆ – h₁)
b) m₁ (h₂ – h₁) + m₂ (h₄ – h₃) + m₃ (h₆ – h₅)
c) m₂ (h₂ – h₁) + m₃ (h₄ – h₃) + m₁ (h₆ – h₅) / 60
d) m₁ (h₂ – h₁) + m₂ (h₄ – h₃) + m₃ (h₆ – h₅) / 60
View Answer

Answer: d
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through compressors C₁, C₂ and C₃
So, Power required to run compressor C₁ = m₁ (h₂ – h₁) / 60
Power required to run compressor C₂ = m₂ (h₄ – h₃) / 60
Power required to run compressor C₃ = m₃ (h₆ – h₅) / 60
Total power required to run the system will be summation of power required to run each compressor.
Total power required to run the system = m₁ (h₂ – h₁) + m₂ (h₄ – h₃) + m₃ (h₆ – h₅) / 60.

9. What is the value of C.O.P. in the following arrangement?

a) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄) / (m₁ + m₂ + m₃) (h₂ – h₃)
b) m₁ (h₁ – h₁₀) + m₂ (h₃ – h₉) + m₃ (h₅ – h₈) / m₁ (h₂ – h₁) + m₂ (h₄ – h₃) + m₃ (h₆ – h₅)
c) m₁ (h₁ – h₁₀) + m₂ (h₃ – h₉) + m₃ (h₅ – h₈) / m₁ (h₂ – h₁) + m₂ (h₄ – h₂) + m₃ (h₆ – h₃)
d) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₅ – h₄) / (m₁ + m₂ + m₃) (h₂ – h₁)
View Answer

Answer: b
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁ – h₁₀
m₂ = 210 Q₂ / h₃ – h₉
m₃ = 210 Q₃ / h₅ – h₈
So, Refrigeration effect across EP₁ = m₁ (h₁ – h₁₀)
Refrigeration effect across EP₂ = m₂ (h₃ – h₉)
Refrigeration effect across EP₃ = m₃ (h₅ – h₈)
Total refrigeration effect produced in the system is the summation of refrigeration effect across each evaporator.
Total refrigeration effect = m₁ (h₁ – h₁₀) + m₂ (h₃ – h₉) + m₃ (h₅ – h₈) = 210 (Q₁ + Q₂ + Q₃)
Total Work = m₁ (h₂ – h₁) + m₂ (h₄ – h₃) + m₃ (h₉ – h₅)
C.O.P. = Total refrigeration effect / Work
= m₁ (h₁ – h₁₀) + m₂ (h₃ – h₉) + m₃ (h₅ – h₈) / m₁ (h₂ – h₁) + m₂ (h₄ – h₃) + m₃ (h₆ – h₅)
= 210 (Q₁ + Q₂ + Q₃) / m₁ (h₂ – h₁) + m₂ (h₄ – h₃) + m₃ (h₉ – h₅).

10. What is the value of the refrigeration effect in the following arrangement?

a) m₁ (h₁ – h₁₂) + m₂ (h₃ – h₁₀) + m₃ (h₅ – h₈)
b) m₁ (h₁₁ – h₁₀) + m₂ (h₉ – h₇) + m₃ (h₆ – h₄)
c) m₁ (h₁ – h₁₂) + m₂ (h₉ – h₁₀) + m₃ (h₅ – h₄)
d) m₁ (h₁₁ – h₁₀) + m₂ (h₈ – h₇) + m₃ (h₁ – h₄)
View Answer

Answer: a
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁ – h₁₂
m₂ = 210 Q₂ / h₃ – h₁₀
m₃ = 210 Q₃ / h₅ – h₈
So, Refrigeration effect across EP₁ = m₁ (h₁ – h₁₂)
Refrigeration effect across EP₂ = m₂ (h₃ – h₁₀)
Refrigeration effect across EP₃ = m₃ (h₅ – h₈)
Total refrigeration effect produced in the system is the summation of refrigeration effect across each evaporator.
Total refrigeration effect = m₁ (h₁ – h₁₂) + m₂ (h₃ – h₁₀) + m₃ (h₅ – h₈) = 210 (Q₁ + Q₂ + Q₃).

11. What is the value of total work done in the following arrangement?

a) m_e1 (h₂ – h₁) + m_e2 (h₄ – h₃) + m_e3 (h₄ – h₅)
b) m_e1 (h₂ – h₁) + m_e3 (h₄ – h₃) + m_e2 (h₆ – h₅)
c) m_e1 (h₂ – h₁) + m_e3 (h₄ – h₃) + m_e3 (h₆ – h₅)
d) m₁ h₅ + m₂ h₅ + m₃ h₄ / (m₁ + m₂ + m₃)
View Answer

Answer: c
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = m_e1 = 210 Q₁ / h₁ – h₁₂
m₂ = 210 Q₂ / h₃ – h₁₀, m_e2 = m₂ + m_e1 (x₁₀ / 1 – x₁₀)
m₃ = 210 Q₃ / h₅ – h₈, m_e3 = m₃ + (m_e1 + m_e2) (x₈ / 1 – x₈)
Total work done is the summation of work done by each compressor.
So, Work done by compressor C₁ = m_e1 (h₂ – h₁)
Work done by compressor C₂ = m_e2 (h₄ – h₃)
Work done by compressor C₃ = m_e3 (h₆ – h₅)
Total work = m_e1 (h₂ – h₁) + m_e2 (h₄ – h₃) + m_e3 (h₆ – h₅).

12. What is the value of C.O.P. in the following arrangement?

a) m₁ (h₁ – h₁₂) + m₂ (h₃ – h₁₀) + m₃ (h₅ – h₈)
b) m₁ (h₁ – h₁₂) + m₂ (h₃ – h₁₀) + m₃ (h₅ – h₈) / m_e1 (h₂ – h₁) + m_e2 (h₄ – h₃) + m_e3 (h₆ – h₅)
c) m₁ (h₁ – h₁₂) + m₂ (h₃ – h₁₀) + m₃ (h₅ – h₈) / m_e1 (h₂ – h₅) + m_e2 (h₄ – h₂) + m_e3 (h₆ – h₅)
d) m₁ (h₁ – h₁₂) + m₂ (h₃ – h₁₀) + m₃ (h₅ – h₈) / m_e1 (h₂ – h₁) + m_e2 (h₄ – h₁) + m_e3 (h₆ – h₁)
View Answer

Answer: b
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁ – h₁₂
m₂ = 210 Q₂ / h₃ – h₁₀
m₃ = 210 Q₃ / h₅ – h₈
So, Refrigeration effect across EP₁ = m₁ (h₁ – h₁₂)
Refrigeration effect across EP₂ = m₂ (h₃ – h₁₀)
Refrigeration effect across EP₃ = m₃ (h₅ – h₈)
Total refrigeration effect produced in the system is the summation of refrigeration effect across each evaporator.
Total refrigeration effect = m₁ (h₁ – h₁₂) + m₂ (h₃ – h₁₀) + m₃ (h₅ – h₈) = 210 (Q₁ + Q₂ + Q₃)
So, Work done by compressor C₁ = m_e1 (h₂ – h₁)
Work done by compressor C₂ = m_e2 (h₄ – h₃)
Work done by compressor C₃ = m_e3 (h₆ – h₅)
Total work = m_e1 (h₂ – h₁) + m_e2 (h₄ – h₃) + m_e3 (h₆ – h₅)
C.O.P. = Total refrigeration effect / Total work done
= m₁ (h₁ – h₁₂) + m₂ (h₃ – h₁₀) + m₃ (h₅ – h₈) / m_e1 (h₂ – h₁) + m_e2 (h₄ – h₃) + m_e3 (h₆ – h₅).

13. What is the value of enthalpy when refrigerant enters the second compressor, i.e., point 4?

a) m₁ h₂ + m₂ h₃ / (m₁ + m₂)
b) m₁ h₁₁ + m₂ h₈ + m₃ h₅ / (m₁ – m₂ + m₃)
c) m₁ h₂ + m₂ h₁ / (m₁ + m₂)
d) m₁ h₅ + m₂ h₅ + m₃ h₄ / (m₁ + m₂ + m₃)
View Answer

Answer: a
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁ – h₁₂
m₂ = 210 Q₂ / h₂ – h₁₁
m₃ = 210 Q₃ / h₆ – h₁₀
At point 4, mass of refrigerant coming from evaporator 1 and 2 is converging.
So, (m₁ + m₂) h₄ = m₁ h₂ + m₂ h₃
h₄ = m₁ h₂ + m₂ h₃ / (m₁ + m₂).

14. What is the value of enthalpy when refrigerant enters the third compressor, i.e., point 7?

a) m₁ h₂ + m₂ h₃ / (m₁ + m₂)
b) m₁ h₁₁ + m₂ h₈ + m₃ h₅ / (m₁ – m₂ + m₃)
c) (m₁ + m₂) h₅ + m₃ h₆ / (m₁ + m₂ + m₃)
d) m₁ h₅ + m₂ h₅ + m₃ h₄ / (m₁ + m₂ + m₃)
View Answer

Answer: c
Explanation: Let, mass m₁, m₂ and m3 be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃.
Where, m₁ = 210 Q₁ / h₁ – h₁₂
m₂ = 210 Q₂ / h₂ – h₁₁
m₃ = 210 Q₃ / h₆ – h₁₀
At point 4, mass of refrigerant coming from evaporator 1 and 2 is converging.
So, (m₁ + m₂ + m₃) h₇ = (m₁ + m₂) h₅ + m₃ h₆
h₇ = (m₁ + m₂) h₅ + m₃ h₆ / (m₁ + m₂ + m₃).

15. What is the power required for the following arrangement?

a) m₁ (h₂ – h₁₁) + (m₁ + m₂) (h₅ – h₈) + (m₁ + m₂ + m₃) (h₈ – h7) / 60
b) m₁ (h₂ – h₁) + (m₁ + m₂) (h₅ – h₄) + (m₁ + m₂ + m₃) (h₈ – h₇) / 60
c) m₁ (h₂ – h₁) + (m₂ + m₃) (h₅ – h₄) + (m₁ + m₂ + m₃) (h₈ – h₇) / 60
d) m₁ h₅ + m₂ h₅ + m₃ h₄ / (m₁ + m₂ + m₃)
View Answer

Answer: b
Explanation: Let, mass m₁, m₂ and m₃ be the mass of refrigerant circulated through evaporators EP₁, EP₂ and EP₃
So, Power required to run compressor C₁ = m₁ (h₂ – h₁) / 60
Power required to run compressor C₂ = (m₁ + m₂) (h₅ – h₄) / 60
Power required to run compressor C₃ = (m₁ + m₂ + m₃) (h₈ – h₇) / 60
Total power required to run the system will be summation of power required to run each compressor.
Total power required to run the system = m₁ (h₂ – h₁) + (m₁ + m₂) (h₅ – h₄) + (m₁ + m₂ + m₃) (h₈ – h₇) / 60.

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