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Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER-VII EXAMINATION WINTER 2017
Subject Code: X71901 Date:02/11/2017
Subject Name: Refrigeration and Air-conditioning
Time:10:30AM TO 1:00PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1

Define the following:-
Dalton's law for partial pressure
Relative humidity
Enthalpy of moist air
Wet bulb temperature
Dew point temperature
Air-conditioning
1 T.R.(Ton of Refrigeration)
07

Discuss in detail with neat sketch about Principle, Construction and working of thermostatic expansion valve.
07
Q.2

Discuss in detail with neat sketch about Principle, Construction and working of Central Air-conditioning systems.
07

Explain in detail with neat sketch about flywheel effect of building material.
07
OR

Define Refrigerant. Classify various types of Refrigerants. List down the desirable properties of an ideal refrigerant.
07
Q.3

Discuss in detail with neat sketch about Principle, Construction and working of Steam Jet Refrigeration system.
07

What is effective temperature? Discuss in brief about the factors governing the effective temperature.
07
OR
Q.3

Explain the following with schematic psychrometric diagram.
Cooling and humidification
Cooling and dehumidification
07

Vapour compression refrigeration systems using R-12 Refrigerant operates between -20 °C and 36 °C respectively. The enthalpies of refrigerant leaving and entering the compressor are 350 kJ/kg and 380 kJ/kg respectively. The enthalpy of liquid refrigerant at 36 °C is 235 kJ/kg. The isentropic efficiency of compressor is 82 %.The compressor bore 12 cm and it runs at 550 rpm with 77 volumetric efficiency. The specific volume of vapour refrigerant at suction of compressor is 0.12 m3/kg. Calculate the following:-
Mass of the refrigerant flowing through the refrigeration system.
Refrigeration capacity of the system.
07
Q.4

Define Duct. Discuss in detail about step-by-step procedure for designing a duct through equal friction method.
07

Discuss in detail with neat sketch about Principle, Construction and working of Ice manufacturing plant.
07
OR
2
Q.4

Explain why flash gas removal is always desirable in a vapour compression refrigeration system
Draw a neat schematic diagram of the refrigeration system having two evaporators, individual compressor, multiple expansion valve arrangement and flash chamber. Also Derive the equation for power required to drive the system and C.O.P. along with P-h diagram.
07

Differentiate between vapour compression refrigeration system and vapour absorption refrigeration system.
Discuss in detail with neat sketch about Principle, Construction and working of practical aqua-ammonia vapour absorption refrigeration system.
07
Q.5

Discuss in detail with neat sketch about Principle and working of Boot strap air refrigeration system. Express the same on T-S diagram.
07

Explain in detail with neat sketch about Working of simple vapour compression refrigeration system. Express the same system on P-h and T-S diagram. Also Derive the equation of C.O.P. for the same system.
07
OR
Q.5

Circular duct of 30 cm is selected to carry an air in conditioned space with the velocity of 360 m/min to keep the noise at desired level. If the duct is replaced by a rectangular duct with the aspect ratio of 1.3 than find out the size of rectangular duct when
The velocity of air in both ducts is same.
The discharge of air in both ducts is same.
07

Classify the various types of fans.
Also discuss in detail about different fan laws.
07