(AUTONOMOUS)
B. Tech VII Semester Supplementary Examinations, May 2018
(Regulations: VCE-R11/R11A)
REFRIGERATION AND AIR CONDITIONING
(Mechanical Engineering)
Date: 17 May, 2018 AN Time: 3 hours Max Marks: 75
Answer ONE question from each Unit
All Questions Carry Equal Marks
Unit I
1. Define refrigeration and Mention five applications of refrigeration. 6M
An air refrigerator used for food storage provides 50 tonnes of refrigeration. The
temperature of air entering the compressor is 70C and the temperature before entering
into expander is 270C. Assuming 30% more power is required than theoretical, find:
i. Actual C.O.P of the cycle
ii. H.P. required for compressor
The quantity of air circulated in the system is 100 kg/min. the compression and expansion
follows the law PV1.3=constant. Take γ=1.4 and Cp= 1.007KJ/kg.k.
9M
2. What are the different heat sources which necessitates refrigeration in aircrafts? 5M
An air refrigeration working on Bell-Coleman cycle takes air into the compressor at 1 atm
and -50C. It is compressed in the compressor to 5 atm and cooled to 250C at the same
pressure. It is further expanded in the expander to 1 atm and discharged to take the
cooling load. The isentropic efficiency of the compressor=85%, the isentropic efficiency of
the expander=90%. Find:
i. Refrigeration capacity of the system if the air circulation is 40 kg/min
ii. H.P. required for the compressor
iii. C.O.P of the system
Take γ=1.4 and Cp= 1.007KJ/kg.k. K and Cv=0.717KJ/kg.K for air.
10M
Unit II
3. Explain with neat diagram the working principle of Simple Vapour compression
Refrigeration system.
8M
Explain the effect of sub cooling and super heating on Vapour compression
Refrigeration system.
7M
4. Explain the principle of operation of three fluid absorption systems. 8M
Compare the difference between the vapour compression and vapour absorption
system.
7M
Unit III
5. Explain the basic components and working principle of Steam Jet Refrigeration system. 8M
Explain the concept of Vortex tube.
7M
6. Briefly explain the purpose of Expansion valves in refrigeration system. 5M
Briefly explain the working of Flooded Evaporator with neat sketch. 10M
Unit IV
7. Define the following terms:
i. Dew point temperature
ii. Relative humidity
iii. Dry bulb temperature
iv. Dry air
v. Moist air
5M
One kg of air at 400C DBT and 50% R.H. is mixed with two kg of air at 200C DBT and 120C
dew point temperature. Calculate temperature and specific humidity of the mixture.
10M
Cont…2

8. Explain the following psychrometric processes and represent them on the psychrometric
chart:
i. Sensible heating
ii. Sensible cooling
6M
An air conditioning plant is to be designed for a small office room for winter conditions.
Out-door conditions: 100C DBT and 80C WBT
Required indoor conditions: 200C DBT and 60% R.H.
Amount of free air circulation: 0.3m3/min/person
Seating capacity of the office: 50
The required condition is achieved first by heating and then by adiabatic humidification.
Find:
i. Heating capacity of the coil in kW and surface temperature required if the bypass
factor of the coil is 0.32
ii. The capacity of the humidifier
9M
Unit V
9. Differentiate between summer air conditioning and winter air conditioning. 7M
Briefly explain Comfort Air Conditioning and Industrial Air conditioning.
8M
10. Briefly explain heating humidification and dehumidification. 7M
What are the factors affecting Human comfort and need for Ventilation? 8M