Winter 2015 Thermal Engineering - II Question Paper

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GUJARAT TECHNOLOGICAL UNIVERSITY
DIPLOMA ENGINEERING – SEMESTER – V-EXAMINATION – WINTER 2015
Subject Code: 3351901  Date: 19/12/2015
Subject Name: Thermal Engineering II
Time: 10:30 AM TO 1:00 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.  Define supercharging and scavenging

2.  State the function of crank shaft and flywheel in I.C. Engine.

3.  Define mean effective pressure and brake power of an I.C. Engine.

4.  Write two functions of fuel pump.

5.  Write four advantages of common rail direct injection system for diesel engine.

6.  Why we need alternative fuels?

7.  Define refrigerator and air conditioning.

8.  Define ton of refrigeration and coefficient of performance.

9.  Name any four thermal insulation used in vapor compression refrigeration system?

10.  Define relative humidity and dew point temperature?

Q.2  (a)  What are the different problems to be faced while using alternative fuels?  03

OR

(a)  What is CNG?  State its advantages?  03

(b)  Discuss the safety issue while using CNG and LPG as fuels.  03

OR

(b)  Discuss the effect of emitted gases in atmosphere?  03

(c)  Differentiate between two stroke and four stroke cycle I.C.Engine.  04

OR

(c)  Differentiate between C.I. and S.I. engine.  04

(d)  State the purpose of governing of I.C. Engine and explain any one method of governing of I.C. Engine.  04

OR

(d)  Draw theoretical and actual valve timing diagram for four stroke petrol engine.   04

Q.3  (a)  Give classification of refrigerants.  03

OR

(a)  List properties of refrigerants.  03

(b)  List different evaporator used in VCRS and explain any one?   03

OR

(b)  List different expansion devices used in VCRS and explain any one?   03

(c)  For bell Coleman cycle, derive equation for cycle COP with usual notations?  04

OR

(c)  Draw schematic diagram of VCRS and state function of each component?  04

(d)  Explain the working of water cooler?  04

OR

(d)  Draw schematic diagram of simple vapor absorption system and explain its working?   04

Q.4  (a)  Define following terms. 1] humidity 2] wet bulb temperature 3] degree of saturation   03

OR

(a)  Explain cooling and dehumidification process on psychometric process chart?   03

(b)  Draw diagram of split air conditioner showing all components?  04

OR

(b)  List types of air conditioning fans used in air conditioning?  04

(c)  The following observations were recorded during a test on single cylinder, low speed, four stroke cycle oil engines, having a bore of 30 cm and stroke   07 of 45 cm.
Speed =300 RPM,
Mean effective pressure = 5 bar,
Brake drum diameter = 1.8 m,
Brake rope diameter = 2 cm,
Net brake load = 1.5 KN.
Find 1] Indicated power 2] Brake power 3] Mechanical efficiency.

Q.5  (a)  In a theoretical cycle, condensing temperature is 380C. The refrigerant used is R12. If the evaporation temperature is -70C then calculate C.O.P. of the cycle. Enthalpy of refrigerant leaving the compressor is 407 KJ/Kg.

(b)  A certain air has DBT of 300C and WBT of 200C. Calculate the following using psychometric chart.
1] Relative Humidity 2] Enthalpy 3] Specific humidity 4] Dew point  temperature   04

(c)  Explain the effect of subcooling and superheating on performance of VCRS?  03

(d)  List various systems of an I.C.Engine.  03

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