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GUJARAT TECHNOLOGICAL UNIVERSITY
DIPLOMA ENGINEERING – SEMESTER – V• EXAMINATION – SUMMER 2016
Subject Code: 3351901 Date:07/05/2016
Subject Name: Thermal Engineering - II
Time: 02:30 PM to 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make Suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Use of programmable & Communication aids are strictly prohibited.
5. Use of only simple calculator is permitted in Mathematics.
6. English version is authentic.
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Q.1 Answer any seven out of ten. 14
1. State functions of piston ring and fly wheel for I C Engine.
2. Define (i) stroke volume (ii) compression ratio
3. What is supercharging?
4. State properties of CNG.
5. State reasons for requirements of alternative fuels.
6. Define (i) C O P of refrigerator (ii) C O P of heat pump
7. State chemical formula of R-11 and R-12 refrigerant.
8. State purpose of compressor in refrigeration system.
9. 1 bar = _________Pa = __________N/m2
10. Define Air-conditioning.
Q.2 (a) Explain fuel supply system for diesel system 03
OR
(a) State the purpose of lubrication. 03
(b) Classify I C Engine in detail. 03
OR
(b) Define (i)Indicated power(ii) Mechanical efficiency(iii)Efficiency ratio 03
(c) Differentiate between 2-stroke and 4-stroke engine. 04
OR
(c) Differentiate between S.I and C.I engine. 04
(d) The following data was recorded during a test run made on a single cylinder, four stroke engines.
Bore and stroke = 10 cm and 12.5 cm respectively
Dead load and spring balance reading = 60 N and 20 N
Effective radius of brake drum = 40 cm
Speed of engine = 2000 rpm
Indicated mean effective pressure = 0.25 MPa
Determine (i) Indicated Power (ii) Brake power (iii) Mechanical efficiency 04
OR
(d) The following particulars refer to a 4-cylinder, 4-stroke petrol engine;
Bore and stroke = 65 mm and 95 mm respectively
Torque = 64 Nm,
Engine speed = 3000 rpm
Determine brake mean effective pressure. 04
Q.3 (a) Compare the air cooling and water cooling system for I.C. Engine 03
OR
(a) State the reasons for failing a spark plug. 03
(b) State safety precautions in I.C Engine. 03
OR
(b) Draw valve timing diagram of 4-stroke C I engine. 03
(c) Define (i) Flash point (ii) Fire point (iii) Pour point (iv) Freezing point 04
OR
(c) Write short note on Biodiesel. 04
(d) Explain reversed Carnot cycle for vapour medium on P-V and T-S diagram. 04
OR
(d) Explain vapour compression cycle on P-V, T-S and P-h diagram. 04
Q.4 (a) Compare between Hermetically sealed compressor and open compressor. 03
OR
(a) Differentiate between Dry expansion evaporator and Flooded evaporator. 03
(b) Explain vapour absorption refrigeration system with neat sketch. 04
OR
(b) State the factors affecting the location of the cold storage. 04
(c) A refrigerator operates on a reversed Carnot cycle whose C O P is 5.0. The evaporator is maintained at a temperature of −6°C and the power required to run the refrigerator is 3.5 kW. Determine the refrigerating effect (RE) and the condenser temperature of the refrigerator. 07
Q.5 (a) Define (i) Psychrometry (ii) Wet bulb temperature (iii) Dew point temperature (iv) Specific humidity 04
(b) Explain heating with humidification process on psychrometric chart. 04
(c) Explain the working of window air conditioner. 03
(d) Differentiate between air conditioner and air cooler. 03
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