Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Summer 4th Sem New 2143406 Thermo Dynamics And Thermal Engineering Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?IV(NEW) ? EXAMINATION ? SUMMER 2019
Subject Code:2143406 Date:09/05/2019
Subject Name: Thermo Dynamics and Thermal Engineering
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.
Q.1 (a) Show that internal energy is Property of the system. 03
(b) Write and explain the First Law of Thermodynamics.
04
(c) A fluid system, contained in a piston and cylinder machine, passes through a
complete cycle of four processes. The sum of all heat transferred during a cycle
is ? 340 kJ. The system completes 200 cycles per min.
Complete the following table showing the method for each item, and compute
the net rate of work output in kW.
Process Q(KJ/min) W(KJ/min) dU(KJ/min)
1-2 0 4340 ------
2-3 42000 0 -------
3-4 -4200 -------------- -73200
4-1 -------------- ---------------- ---------
07
Q.2 (a) Write a short note on Brayton cycle. 03
(b) Write a short note on modified Rankine cycle, 04
(c) Explain Rankine cycle with p-v and T ? s diagram and find the efficiency of
Rankine cycle.
07
OR
(c) The power developed by a turbine in a certain steam plant is 1200 kW. The
heat supplied to the steam in the boiler is 3360 kJ/kg, the heat rejected by the
system to cooling water in the condenser is 2520 kJ/kg and the feed pump
work required to pump the condensate back into the boiler is 6 kW.
07
Q.3 (a) Define Effectiveness. 03
(b) One kg of air is compressed polytropically from 1 bar pressure and a
temperature of 300 K to a pressure of 6.8 bar and temperature of 370 K.
Determine the irreversibility if the sink temperature is 293 K. Assume R =
0.287 kJ/kg K, cp = 1.004 kJ/kg K and cv = 0.716 kJ/kg K.
04
(c) Derive and Explain Clausius-Claperyon Equation with p-T Diagram 07
OR
Q.3 (a) Define and explain Available and Unavailable Energy 03
(b) 15 kg of water is heated in an insulated tank by a churning process from 300
K to 340 K. If the surrounding temperature is 300 K, find the loss in
availability for the process.
04
(c) Derive Maxwell?s equation 07
Q.4 (a) State and explain Dalton?s law 03
(b) A vessel of 0.35 m3 capacity contains 0.4 kg of carbon monoxide (molecular
weight = 28) and 1 kg of air at 20?C. Calculate :
(i) The partial pressure of each constituent
(ii) The total pressure in the vessel, and
The gravimetric analysis of air is to be taken as 23.3% oxygen (molecular
weight = 32) and 76.7% nitrogen (molecular weight = 28).
04
(c)
Prove the following relation ?? =
? ?? ?? ?? ?? ? ?? ??
1
?
?? ????
?? ??
07
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Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?IV(NEW) ? EXAMINATION ? SUMMER 2019
Subject Code:2143406 Date:09/05/2019
Subject Name: Thermo Dynamics and Thermal Engineering
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.
Q.1 (a) Show that internal energy is Property of the system. 03
(b) Write and explain the First Law of Thermodynamics.
04
(c) A fluid system, contained in a piston and cylinder machine, passes through a
complete cycle of four processes. The sum of all heat transferred during a cycle
is ? 340 kJ. The system completes 200 cycles per min.
Complete the following table showing the method for each item, and compute
the net rate of work output in kW.
Process Q(KJ/min) W(KJ/min) dU(KJ/min)
1-2 0 4340 ------
2-3 42000 0 -------
3-4 -4200 -------------- -73200
4-1 -------------- ---------------- ---------
07
Q.2 (a) Write a short note on Brayton cycle. 03
(b) Write a short note on modified Rankine cycle, 04
(c) Explain Rankine cycle with p-v and T ? s diagram and find the efficiency of
Rankine cycle.
07
OR
(c) The power developed by a turbine in a certain steam plant is 1200 kW. The
heat supplied to the steam in the boiler is 3360 kJ/kg, the heat rejected by the
system to cooling water in the condenser is 2520 kJ/kg and the feed pump
work required to pump the condensate back into the boiler is 6 kW.
07
Q.3 (a) Define Effectiveness. 03
(b) One kg of air is compressed polytropically from 1 bar pressure and a
temperature of 300 K to a pressure of 6.8 bar and temperature of 370 K.
Determine the irreversibility if the sink temperature is 293 K. Assume R =
0.287 kJ/kg K, cp = 1.004 kJ/kg K and cv = 0.716 kJ/kg K.
04
(c) Derive and Explain Clausius-Claperyon Equation with p-T Diagram 07
OR
Q.3 (a) Define and explain Available and Unavailable Energy 03
(b) 15 kg of water is heated in an insulated tank by a churning process from 300
K to 340 K. If the surrounding temperature is 300 K, find the loss in
availability for the process.
04
(c) Derive Maxwell?s equation 07
Q.4 (a) State and explain Dalton?s law 03
(b) A vessel of 0.35 m3 capacity contains 0.4 kg of carbon monoxide (molecular
weight = 28) and 1 kg of air at 20?C. Calculate :
(i) The partial pressure of each constituent
(ii) The total pressure in the vessel, and
The gravimetric analysis of air is to be taken as 23.3% oxygen (molecular
weight = 32) and 76.7% nitrogen (molecular weight = 28).
04
(c)
Prove the following relation ?? =
? ?? ?? ?? ?? ? ?? ??
1
?
?? ????
?? ??
07
2
where,
M = Molecular weight of the mixture,
?? ?? = Number of moles of an any constituent,
?? ????
= Mass fraction of the constituent, and
?? ?? = Molecular weight of the constituent.
OR
Q.4 (a)
Show that ?? ??
=
?? ?? ?1
03
(b) Write a short note on Compressibility chart 04
(c) 4 kg of carbon dioxide at 40?C and 1.4 bar are mixed with 8 kg of nitrogen at
160?C and 1.0 bar to form a mixture at a final pressure of 0.7 bar. The process
occurs adiabatically in a steady flow apparatus. Calculate :
(i) The final temperature of the mixture ; (ii) The change in entropy.
Take value of Cp : for CO2 = 0.85 kJ/kg K and N2 = 1.04 kJ/kg K.
07
Q.5 (a) A hot plate 1 m ? 1.5 m is maintained at 300?C. Air at 25?C blows over the
plate. If the convective heat transfer coefficient is 20 W/m
2
?C, calculate the
rate of heat transfer.
03
(b) Write a short note on Thermal Conductivity 04
(c) The effective temperature of a body having an area of 0.12 m
2
is 527?C.
Calculate the following : (i) The total rate of energy emission. (ii) The intensity
of normal radiation, and (iii) The wavelength of maximum monochromatic
emissive power. Take;?? = = 5.67 ? 10
?8
W
m
2
K
4
07
OR
Q.5 (a) Define black body, white body & gray body. 03
(b) The inner surface of a plane brick wall is at 60?C and the outer surface is at
35?C. Calculate the rate of heat transfer per m
2
of surface area of the wall,
which is 220 mm thick. The thermal conductivity of the brick is 0.51 W/m?C.
04
(c) A reactor?s wall 320 mm thick, is made up of an inner layer of fire brick (k =
0.84 W/m?C) covered with a layer of insulation (k = 0.16 W/m?C). The reactor
operates at a temperature of 1325?C and the ambient temperature is 25?C. (i)
Determine the thickness of fire brick and insulation, which gives minimum
heat loss. (ii) Calculate the heat loss presuming that the insulating material has
a maximum temperature of 1200?C.
If the calculated heat loss is not acceptable, then state whether addition of
another layer of insulation would provide a satisfactory solution.
07
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This post was last modified on 20 February 2020