Refrigeration & Air-Conditioning - UTU Question Paper - 2019
Max marks: 100
All questions are compulsory.
Draw diagrams wherever necessary. All questions carry equal marks..
1. Attempt any FOUR parts of the following.
(A) Describe in brief the physical, thermodynamic properties of a refrigerant.
(B) Differentiate between a heat engine and a refrigerator, using the appropriate schematic and cyclic diagram.
(C) Explain simple air evaporative cooling system for air craft refrigeration system with the help of suitable diagram.
(D) What are the limitations of single stage vapor compression cycle for low temperature refrigeration?
(E) Discuss the advantages of closed refrigeration system over an open refrigeration system.
(F) Describe different types of water cooled condensers used in the refrigerating machines.
2. Attempt any FOUR parts of the following. 5X4
(A) Draw actual vapour compression cycle on p-v and T-s diagram and list various processes it consists of.
(B) Define the following terms
i. Dry air rated temperature
ii. Bypass factor
iii. Apparatus dew point
iv. Sensible heat factor
V. Effective temperature
(C) Draw a neat diagram of the simple ammonia water absorption refrigeration system and explain its working.
(D) In an ideal vapour compression refrigeration cycle, the enthalpy of the refrigerant at exit from the condenser, compressor and evaporator is 80 kJ/kg, 200 kJ/kg and 180 kJ/kg respectively. Calculate the COP of the cycle.
(E) Prove that volumetric efficiency is provided by expansion, i.e.
Env=1+C-C(PH/PL) Where C = Clearance ratio
(F) Give the designation for the following refrigerants
i. Dichloro-tetrafluoro-ethane (C2C12F4)
ii. Difluoro-monochloro-methane (CHCIF2) E-mail
3. Attempt any TWO parts of the following
(A) Explain how a reversed Brayton cycle can be modified to approach a reversed Carnot cycle by means of multistage compression with inter cooling and also multistage expansion.
(B) Define the following terms
i. Refrigeration effect
ii. Ton of refrigeration
iii. COP
iv. Refrigerator
v. Heat pump
(C) Explain different types of methods of refrigeration.
4. Attempt any TWO parts of the following . 10X2
(A) Draw a neat and clean diagram of lithium bromide water absorption refrigeration system and explain its working.
(B) Explain types of air refrigeration systems with neat and clean p-v and -s diagrams,
(C) Compare R-12, R-22 and Ammonia in regards of their properties as a refrigerant.
5. Attempt any TWO parts of the following. 10 X 2
EX (A) Write short note on the cold storages and describe their role in preservation of fruits and vegetables.
(B) Write short note on
i. Air washers
ii. Secondary refrigerants
iii. Aircraft refrigeration system
(C) Describe with a neat and clean diagram working of centrifugal compressor. What are the advantages and disadvantages of centrifugal compressor over reciprocating compressors?
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