Test: Refrigerants - 3


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QUESTION: 1

 Which one of the following refrigerants is an Azeotrope?

Solution:

Azeotrope refrigerants are designated by R-500 series.
Hence, R-502 will be an Azeotrope.

QUESTION: 2

The significant advantage of using Ammonia as a refrigerant is its.

Solution:

Properties of Ammonia Refrigerant:
1. It is a chemical compound of Nitrogen and Hydrogen and under ordinary condition. It is a colourless gas.
2. High latent heat of vaporization at -15°C latent heat of vaporization is 131b kJ/kg.
3. It is poisonous if inhaled in large quantities.
4. It is some what flammable.

QUESTION: 3

The recommended material for use with ammonia as a refrigerants is

Solution:

Ammonia reacts with copper and hence when ammonia is used as a refrigerant copper material is not used.
Generally wrought iron and steel is used.

QUESTION: 4

Which one eco-friendly refrigerant out of the following is used in many domestic and car air- conditioners now-a-days?

Solution:

R-134a is known as eco-friendly refrigerant since it does not contain any Cl atom hence it does not lead to Ozone layer depletion.

QUESTION: 5

What is an Azeotrope?

Solution:

Azeotrope is a mixture of refrigerants without phase separation.

QUESTION: 6

The use of refrigerant R-22 for temperatures below -30°C is not recommended due to its

Solution:
QUESTION: 7

Hydrogen is used in electrolux refrigeration system so that vapour pressure of ammonia in the evaporator should be

Solution:
QUESTION: 8

Which one of the following refrigerants has the highest critical temperature?

Solution:

QUESTION: 9

In an absorption type refrigerator, the heat is supplied to NH3 generator by condensing steam at 2 bar and 90% dry. The temperature in the refrigerator is to be maintained at - 5°C. If the refrigeration load is 20 tones and actual COP is 70% of the maximum then mass of steam required per hour is
(Take atmospheric temperature as 30°C saturation temperature of steam at pressure of 2 bar is 120.2°C, hfg at 2 bar is 2201.6 kJ/kg)

Solution:

Given: TG = 393.2 k, Tc = 303 k,
TE = -5 + 273 = 268 k

actual COP = 0.7 x 1.756 = 1.229
actual heat supplied = Refrigeration load/Actual COP

Assuming that only latent heat of steam is used for heating

QUESTION: 10

Match List-I (Refrigerant) with List-Il (Application) and select the correct answer using the codes given below the lists:
    List-l          List-II
A. R-11      1. Window type air conditioning system
B. R-12      2. Central air-conditioning system
C. R-22      3. Domestic refrigerator
D. NH3      4. Cold storages, ice plants
Codes:
      A B C D
(a)  2 1  3 4
(b)  4 3  1 2
(c)  2 3  1 4
(d)  4 1  3 2

Solution:

R - 11: It is used with centrifugal co m pressor in large capacity central air-conditioning plants.
R-12: It is used with reciprocating compressors in small units, specially domestic refrigerators, water coolers etc.
R-22: It is used with reciprocating compressors in window type air conditioners and large units such as package units and central air conditioning plants.
NH3: It is used with reciprocating and screw compressors, in cold storage, i.e., plants, food refrigeration, etc.

QUESTION: 11

Match List-I (Property of refrigerant or absorbent) with List-II (Name of refrigerant) and select the correct answer using the code given below the lists
List-I                                                                  List-II
A. Used for very low temperature                     1. CF4
B. Used with centrifugal compressors              2. CCI3F
C. Used in vortex tube                                     3. Air
Codes:    A  B  C
          (a) 1  2  3
          (b) 3  1  2
          (c) 1  3  2
          (d) 3  2  1

Solution:
QUESTION: 12

When the mixture of refrigerant is used to replace a refrigerant, if the COP increase, the reason attributed is

Solution:


i.e., cooling effect increases

QUESTION: 13

Match List-l with List-ll and select the correct answer using the codes given below the lists:
List-l                                     List-ll
A. Sulphur candle test        1. Propane
B. Halide torch test             2. Ammonia
C. Soap and water test       3. Halocarbon refrigerants
D. Ammonia Swab test       4. Sulphur dioxide
Codes:
      A  B   C  D
(a)  2  3   1   4
(b)  4  1   3   2
(c)  2  1   3   4
(d)  4  3   1   2

Solution:
QUESTION: 14

Ideal refrigerant mixture is one which

Solution:
QUESTION: 15

Consider the following statements:
1. Azeotropes are the mixtures of refrigerants and behave like pure substances.
2. Isomers refrigerants are compounds with the same chemical formula but have different molecular structures.
3. The formula n + p + q = 2m is used for unsaturated chloro-fluorocarbon compounds (m, n, p and q are the number of atoms of carbon, hydrogen, fluorine and chlorine respectively.)
​Q. Which of these statements are correct?

Solution:

Azeotropes are non ideal mixture as they show deviation from Raoults law.

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