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Past Year Questions: Vapour Refrigeration - Mechanical Engineering MCQ


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14 Questions MCQ Test Additional Study Material for Mechanical Engineering - Past Year Questions: Vapour Refrigeration

Past Year Questions: Vapour Refrigeration for Mechanical Engineering 2024 is part of Additional Study Material for Mechanical Engineering preparation. The Past Year Questions: Vapour Refrigeration questions and answers have been prepared according to the Mechanical Engineering exam syllabus.The Past Year Questions: Vapour Refrigeration MCQs are made for Mechanical Engineering 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Past Year Questions: Vapour Refrigeration below.
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Past Year Questions: Vapour Refrigeration - Question 1

Round the clock cooling of an apartment having a load of 300 MJ/day requires and air conditioning plant of capacity about

[1993]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 1

Capacity= Q . 300 MJ/day

= 3.47 kW
1 ton = 3.5 kW

= 0.99 ton
= 1 ton

Past Year Questions: Vapour Refrigeration - Question 2

In a vapour compression refrigeration system, liquids to suction heat exchanger is used to

[2000]

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Past Year Questions: Vapour Refrigeration - Question 3

A refrigerator based on ideal vapour compression cycle operates between the temperature limits of –20°C and 40°C. The refrigerant enters the condenser as saturated vapour and leaves as saturated liquid. The enthalpy and entropy values for saturated liquid and vapour at these temperatures are given in the table below.

If refrigerant circulation rate is 0.025 kg/s, the refrigeration effect is equal to

[2003]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 3



= 0.07 + x + (0.7366 – 0.07)
⇒ 0.67 = 0.07 + x + 0.6666
⇒ 

= 20 + 0.9(180 – 20)
= 20 + 0.9 × 160 =165 kJ/kg
Refrigerating effect per kg = h2 – h1
= 164 – 80 = 84 kJ/kg
Hence refrigerating effect for 0.025 kg/sec circulation
= 84 × 0.025 = 2.1 kW

Past Year Questions: Vapour Refrigeration - Question 4

A refrigerator based on ideal vapour compression cycle operates between the temperature limits of –20°C and 40°C. The refrigerant enters the condenser as saturated vapour and leaves as saturated liquid. The enthalpy and entropy values for saturated liquid and vapour at these temperatures are given in the table below.

The COP of the refrigerator is

[2003]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 4


Past Year Questions: Vapour Refrigeration - Question 5

In the window air conditioner, the expansion device used is

[2004]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 5

The capillary tube is used as expansion device

Past Year Questions: Vapour Refrigeration - Question 6

A R-12 refrigerant reciprocating compressor operates between the condensing temperature of 30º and evaporator temperature of –20ºC. The clearance volume ratio of the compressor is 0.03. Specific heat ratio of the vapour is 1.15 and the specific volume at the suction is 0.1089 m3/kg. Other properties at various states are given in the figure. To realize 2 tons of refrigeration, the actual volume displacement rate considering the effect of clearance is

[2004]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 6

Given: Clearance volume ratio,
C = 0.03
Specific volume at suction,
v1 = 0.1089 m3/kg
Net refrigerating effect
= 2 ton = 2 × 3.516 kJ = 7.032 kJ/s Specific heat ratio, c = 1.15

∴ Net refrigerating effect
= m  (h1 – h4)
or 7.032 = m (176 – 65)
or m = 0.063 kg/s
∴ Volume =  0.063 × 0.1089
= 6.89 × 10–3 m3/s
Volumetric efficiency

= 0.909
∴ Volume displace mentrate considering clearance effect
= 6.89 × 10–3 × 0.909
= 6.26 × 10–3 m3/s

Past Year Questions: Vapour Refrigeration - Question 7

The vapour compression refrigeration cycle is represented as shown in the figure below, with state 1 being the exit of the evaporator. The coordinate system used in this figure is

[2005]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 7

T-h curve

Past Year Questions: Vapour Refrigeration - Question 8

In an ideal vapour compression refrigeration cycle, the specific enthalpy of refrigerant (in kJ/kg) at the following states is given as:
Inlet of condenser : 283
Exit of condenser : 116
Exit of evaporator : 232
The COP of this cycle is

[2009]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 8


1– 2   →  work done by the compressor 2 - 3 → condenser heat rejected at constant pressure
3 - 4 →   throttling
4 - 1 →   heat addition in evaporator
Given :
h2 = 283 kJ/ kg
h3 = 116 kJ/kg = h4 (from ph curve)
h1 = 232 kJ/kg
We know

Past Year Questions: Vapour Refrigeration - Question 9

A refrigerator operates between 120 kPa and 800 kPa in an ideal vapor compression cycle with R-134a as the refrigerant. The refrigerant enters the compressor as saturated vapor and leaves the condenser as saturated liquid. The mass flow rate of the refrigerant is 0.2 kg/s.
Properties for R -134a are as follows: Saturated R-134a

The rate at which heat is extracted, in kJ/s from the refrigerated space is

[2012]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 9

Rate at which heat is extracted
= m (h1 – h4) = 0.2 (237 – 95.5)
= 28.3 kW

Past Year Questions: Vapour Refrigeration - Question 10

A refrigerator operates between 120 kPa and 800 kPa in an ideal vapor compression cycle with R-134a as the refrigerant. The refrigerant enters the compressor as saturated vapor and leaves the condenser as saturated liquid. The mass flow rate of the refrigerant is 0.2 kg/s.
Properties for R -134a are as follows: Saturated R-134a

The power required for compressor in kW is

[2016]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 10

Power required by compressor
p = m(h2 – h1) = 0.2 (276.45 – 237) = 7.9 kW

Past Year Questions: Vapour Refrigeration - Question 11

Consider an ideal vapor compression refrigeration cycle. If the throttling process is replaced by an isentropic expansion process, keeping all the other processes unchanged, which one of the following statements is true for the modified cycle?

[2019]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 11

Vapor compression refrigeration cycle :

Both cycle required same amount of work input but by use of Isentropic expander, we can get more amount of refrigeration effect, hence
((COP)modified cycle > ((COP)original cycle)

Past Year Questions: Vapour Refrigeration - Question 12

Global warming is caused by

[2000]

Past Year Questions: Vapour Refrigeration - Question 13

Environment friendly refrigerant R134a is used in the new generation domestic refrigerators.Its Chemical formula is

[2004]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 13


Number of carbon atoms = 1st digit + 1 = 1+1 = 2
Number of hydrogen atoms = 2nd digit – 1 = 3 – 1 = 2
Number of fluorine atoms = 3rd digit = 4
So chemical formula is C2H2F4

Past Year Questions: Vapour Refrigeration - Question 14

Which one of the following is a CFC refrigerant?

[2015]

Detailed Solution for Past Year Questions: Vapour Refrigeration - Question 14

R744–CO2
R502 – CHClF3 + CCl F2CF3

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