Summer 2014 Thermal Engineering - I Question Paper

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GUJARAT TECHNOLOGICAL UNIVERSITY
DIPLOMA ENGINEERING – SEMESTER IV –  • EXAMINATION – SUMMER-2014
Subject Code:3341902  Date: 04/05/2015
Subject Name: THERMAL ENGINEERING- I
Time:10:30 AM TO 01:00 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 Dryness fraction of steam and state its value for dry and saturated steam

2.  Define Sensible heat and Latent heat

3.  State functions of feed check valve and economizer

4.  Define equivalent evaporation in context with steam boiler also state its unit.

5.  Define volumetric efficiency of air compressor

6.  Define condenser efficiency and vacuum efficiency for steam condenser

7.  List sources of Air leakage in steam condenser.

8.  List different types of calorimeter

9.  List various factors affecting convective heat transfer

10.  List mode of heat transfer and give example of each

Q.2  (a)  Give difference between Jet condenser and Surface Condenser   03

OR

(a)  Draw only neat sketch of surface type condenser and label it  03

(b)  Draw only neat sketch of Cochran boiler and show flue gas path in it  03

OR

(b)  Draw only neat sketch of Babcock and Wilcox boiler and show flue gas path in it   03

(c)  Explain water level indicator with neat sketch  04

OR

(c)  State four difference between induced draft and forced draft in context with steam boiler   04

(d)  State advantages of centrifugal compressors  04

OR

(d)  Explain in brief effect of clearance volume in reciprocating air compressor  04

Q.3  (a)  State needs for compounding of steam turbine  03

OR

(a)  Compare impulse and reaction turbine on three different basis  03

(b)  Draw velocity compounding diagram of steam turbine   03

OR

(b)  Draw Pressure compounding diagram of steam turbine  03

(c)  Steam enters nozzle with a velocity of 300 m/s with pressure of 3.5 bar with Dryness fraction 0.96 and expands isentropically to 2 bar, using Mollier chart find out change in enthalpy of steam and exit velocity of steam   04

OR

(c)  Apply steady flow energy equation (SFEE) to nozzle and derive equation of extreme velocity   04

(d)  Compare reciprocating air compressor and rotary air compressor on four different criteria.   04

OR

(d)  Explain in brief intercooling in multistage air compression with its advantages  04

Q.4  (a)  Define absorptivity, reflectivity and transmitivity in context with radiation  03

OR

(a)  A concrete wall of house is 50 cm thick and a surface area of 10 m X 5 m. The inside temperature of wall is 30◦C and outside temperature is 10◦C. The thermal conductivity of concrete is 0.8 W/m◦K. Calculate the heat loss through the wall.   03

(b)  State Fourier’s law for conduction and explain heat conducted through flat plate  04

OR

(b)  Define heat exchanger and give classificationwith brief introduction of each .  04

(c)  A boiler produces 10 kg of dry and saturated steam per kg of coal from feed water at 45◦C. The pressure of the steam is 10 bar. Find out equivalent evaporation also find boiler efficiency if calorific value of coal is 35000KJ/Kg07

Q.5  (a)  Explain concept of black body in brief  04

(b)  Draw Mollier chart and show isentropic and throttling process on it  04

(c)  Calculate enthalpy of 10 kg steam with temperature 300◦C and pressure of 14 bar03

(d)  Calculate entropy and volume of steam in above case i.e.Q.5(c) .Take Cp of steam= 2.1 KJ/KgK   03

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