GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- VII (New) EXAMINATION — WINTER 2019
--- Content provided by FirstRanker.com ---
Subject Code: 2171911 Date: 23/11/2019Subject Name: Advance Heat Transfer
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
--- Content provided by FirstRanker.com ---
Q.1 (a) What are Heisler charts? How these charts are used to obtain temperature 03 distribution?
(b) Define Biot number and Fourier number? State their significances? 04
(c) Draw the boiling curve and identify the burnout point on the curve. 07 Explain how burnout is caused. Why is the burnout point avoided in the design of boilers?
--- Content provided by FirstRanker.com ---
Q.2 (a) With suitable examples, explain in brief about periodic variation and non- 03 periodic variation transient heat transfer.
(b) Explain all the different mechanisms of heat transfer from the human 04 body (a) Through the skin, and (b) through the lungs.
(c) What is an irregular boundary? What is a practical way of handling 07 irregular boundary surfaces with the finite difference method?
OR
(c) What is lumped system analysis? Derive equation for lumped parameter 07 analysis.
--- Content provided by FirstRanker.com ---
Q.3 (a) Differentiate clearly between boiling and condensation. 03
(b) Define the following terms used in the finite difference formulation: 04 Node, Nodal Network, Volume Element, and Nodal Spacing.
(c) Explain radial fins of rectangular and parabolic profiles. 07
OR
Q.3 (a) Differentiate clearly between dropwise condensation and filmwise 03 condensation.
--- Content provided by FirstRanker.com ---
(b) Explain in brief about free convection and force convection with suitable 04 examples.
(c) Define fin efficiency and fin effectiveness. Why is the insulated-tip 07 solution important for the fin problems?
Q.4 (a) What do you mean by extended surfaces? Under what circumstances, one 03 should opt for extended surfaces?
(b) Write a short note on Emissivity and absorptivity of gases and gas 04 mixtures.
(c) 25mm thick steel plate (K= 48 W/mk) with uniform heat generation of 07 300*10°W/m³ having surface temperatures of 453k and 393k respectively. Determine :
--- Content provided by FirstRanker.com ---
a) The temperature distribution across the plate,
b) The position and value of maximum temperature,
c) The flow of heat from each surface of the plate.
OR
Q.4 (a) Explain the function of extended surfaces with classification. 03
--- Content provided by FirstRanker.com ---
(b) Define mean bulk temperature and mean film temperature with their 04 significances.
(c) A 6-cm-diameter egg initially at a uniform temperature 07 of approximately 75% water. The egg is initially at a uniform temperature of 5°C and is dropped into boiling water at 95°C. Taking the convection heat transfer coefficient to be h=1200W/m² °C, determine how long it will take for the center of the egg to reach 70°C. Take thermal conductivity and diffusivity of eggs at the average temperature of 37.5°C; k=0.627W/m°C, A;=1.9958, a =0.151x10°m²/s and M= 3.0753.
Q.5 (a) What is Beer’s law? Why do surfaces absorb differently for solar or earth 03 bound radiation?
--- Content provided by FirstRanker.com ---
(b) What do you mean by ‘heat generation’? With suitable examples, 04 explain in brief about ‘uniform heat generation’.
(c) Explain effect of radiation on measurement of temperature by a bare 07 thermometer. A bare thermometer measuring the temperature of a gas body reads 600K. The surrounding walls are at 500K. The thermometer bulb is 3mm in diameter and is spherical, its surface emissivity being 0.7. The convective heat transfer coefficient over the surface is 40W/m²K. Determine the gas temperature and error involved.
OR
Q.5 (a) What is latent heat? How is the latent heat loss from the human body 03 affected by (a) skin wetness and (b) Relative humidity of the environment?
(b) Derive Nusselt theory of laminar condensation on vertical plate. 04
--- Content provided by FirstRanker.com ---
(c) A thermocouple (€=0.6) is used to measure the temperature of flue gases 07 in a large duct. The temperature of the duct wall is 20°C and the temperature measured by the thermocouple is 500°C. The convective heat transfer coefficient is 200W/m²’C. Determine the true gas temperature and error involved.
A thin radiation shield (e=0.3) is enveloped to minimize the error.
Estimate the error for the above case.
--- Content provided by FirstRanker.com ---
This download link is referred from the post: GTU BE/B.Tech 2019 Winter Question Papers || Gujarat Technological University