1
Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
B.VOC. -SEMESTER 1 (NEW SYLLABUS) EXAMINATION- WINTER 2018
Subject Code: 1110401 Date: 16/1/2019
Subject Name: Basics of Refrigeration (B.O.R)
Time:10.30 AM 12.30 PM Total Marks: 50
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Marks
Q.1

Define COP for heat pump and Refrigerator.
05

Draw the flow diagram of VCR and write function of each component.
05
Q.2

The temperature limit of an ammonia refrigeration system are 250c and -100c. If gas is dry at end of the compression. Calculate
1. COP of the cycle.
2. Compressor work.
Assuming no undercooling of the liquid ammonia.
05

Explain types of vapour compression refrigeration cycle with the expression of COP and with the help of P-H and T-S diagram.
Theoretical vapour compression cycle with wet vapour after compression.
Theoretical vapour compression cycle with sub cooling of refrigerant.
05
OR

Enlist the types of Vapour compression system and also explain
Cycle with superheated vapour after compression.
Cycle with dry saturated vapour after compression.
05
Q.3

Draw a simple vapour compression refrigeration system with neat sketch and p-v t-s diagram. Mention the advantages and disadvantages of VCR over air refrigeration cycle.
05

A vapour compression refrigeration machine, with Freon -12 as refrigerant, and the liquid evaporates in the evaporator at 150 C. The temperature of this refrigerant at the delivery from the compressor is 150 C when the vapour is condensed at 100 C. Find the C.O.P if there is no under cooling and liquid is cooled by 50 C before expansion by throttling.
05
OR
Q.3

Define Following terms:
1. Refrigeration.
2. Refrigerator.
3. Refrigerant.
4. 1 TR.
5. BTU.
05
2

A refrigerating machine using R-12 as refrigerant operates between the pressures 2.5 bar and 9.0 bar. The compression is isentropic and there is not under cooling in the condenser. The vapour is dry and saturated condition at the beginning of the compression. Estimate
the theoretical COP
05
Q.4

Give the advantages of VAR system over VCR system
05

Draw the flow diagram of practical VAR and write function of each component.
05
OR
Q.4

Explain Air Refrigeration (Bell-coleman) Cycle.
05

In a VAR System, heating, cooling and refrigeration take place at the temperatures of 1000C, 200C and -50C respectively. Find the maximum C.O.P. of the system.
05
Q.5

Derive the equation for COP of an Ideal VAR System.
05

How will you assign the number to following Refrigerant?
i. Trichloro-monofluoro-methane(CCl3F)
ii. Tetrafluoro-ethane(CF3CH2F)
iii. Difluoro-ethane(CH3CHF2)
iv. 1,1,2,2-Tetrafluoroethane(C2H2F4)
v. Chlorofluoroethane (C2H4ClF)
05
OR
Q.5

What are the desirable properties of an ideal refrigerant?
05

Explain simple Vapour Absorption System.
05