Gujarat Technological UniversitySummer 2024 examination

GTU 3151909 Heat Transfer Summer 2024 Question Paper & PDF

B.E. · Mechanical Engineering · Semester 5 · Subject code 3151909
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Total
70 marks
To pass
23 marks (33%)
Duration
2.5 Hours 2:30 PM – 5:00 PM
Questions
5 with internal choice
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Q.1

14 Marks
(a)
3 marks
Do as directed: (1) Define: Thermal diffusivity. (2) Arrange the material in descending order of their thermal conductivity: (i) Water (ii) Copper (iii) Air and (iv) Wood. (3) Define: Anisotropic material.
(b)
4 marks

Give four examples of free convection and four examples of forced convection observed from day to day life.

(c)
7 marks
Explain the following with reference to a heat exchanger: (1) Fouling factor, (2) Effectiveness of heat exchanger, (3) Correction factor for multipass arrangement.

Q.2

14 Marks
(a)
3 marks

What do you mean by radiation shiled? Give two examples of use of radiation shield.

(b)
4 marks

With suirable example, explain in brief abour black body, white body, opquae body and transperant body.

(c)
7 marks

An aluminim fin (k = 200W/mK, 2.5cm long,1m width, and 3.5mm thick) protrudes from a wall. The base is at 420°C and surrounding air temperature is 30°C. Determine the heat dissipated from the fin and fin efficiency for the fin is of finite length and heat loss from fin tip is negligible. Take h = 11W/m²K.

(c)
7 marks
A furnace wall, 32 cm thick, is made up of an inner layer of brick (k=0.84W/mK) covered with a layer of insulation (k=0.16W/mK). The furnace operates at a temperature of 1325°C and the ambient temperature is 25°C. (i) Determine the thickness of 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 accepted than state whether addition of another layer of insulation would provide a satisfactory solution.

Q.3

14 Marks
(a)
3 marks
Explain mean film temperature and bulk mean temperature.
(b)
4 marks
Differentiate between boiling and condensation.
(c)
7 marks
Discuss the electrical analogy for radiant heat transfer.
(a)
3 marks

Justify that a good absorber is also a good emitter for radiation heat transfer.

(b)
4 marks
Explain in detail about cross flow heat exchanger with its advantages.

Give suitable examples.

(c)
7 marks

Define condensation process. Also explain film condensation and drop- wise condensation.

Q.4

14 Marks
(a)
3 marks

‘It is desirable to use two thin fins instead of one thick fin for engine cooling’. Give reason.

(b)
4 marks
What is insulation? State its four applications in engineering field.
(c)
7 marks
Write the most general equation in Cartesian co-ordinates for heat transfer by conduction. Deduce above equation for the following cases with suitable assumptions; (i) Laplace equation, (ii) Poisson equation, and (iii) Fourier equation.
(a)
3 marks

Use of aluminum material as a cooking utensils are not desirable. Evaluate.

(b)
4 marks
Write the general differential equation in Cartesian co-ordinates for 3-D unsteady heat conduction by considering an infinitesimal volume element. Deduce there from the conduction equations for the following cases; (i) Steady state 1-D flow with heat generation at uniform rate within material, (ii) Unsteady 2-D flow without heat generation.
(c)
7 marks

Explain physical significance of critical radius of insulation and derive an expression for the same critical radius in case of sphere.

Q.5

14 Marks
(a)
3 marks
Differentiate natural and forced convection.
(b)
4 marks
State the similarities and difference between: (1) Nusselt number and Biot number, (2) Grashof Number and Reynold number.
(c)
7 marks

What is the limitation of Rayleigh’s method of dimensional analysis? Which method is preferred in such case and how repeating variables are selected?

(a)
3 marks
Define: Nusselt number, Grashof Number and Reynold number.
(b)
4 marks

State the governing law for convection heat transfer. Explain in brief about convection heat transfer coefficient.

(c)
7 marks
Using Buckingham–π theorem show that, Nu=f(Re,Pr)Nu = f(Re, Pr) for forced convection.

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About this paper

Official Gujarat Technological University (GTU) examination paper for Heat Transfer (Summer 2024, B.E. · Mechanical Engineering, Sem 5). Features complete 70-mark regular & remedial examination pattern, official marking distribution across all 5 questions, and direct 1-click official PDF download.

Transcribed for student exam preparation from Gujarat Technological University official examination archives. Questions, syllabus guidelines, and curriculum marking schemes remain the intellectual property of Gujarat Technological University.

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