GUJARAT TECHNOLOGICAL UNIVERSITY

BRANCH NAME: Mechanical Engineering

SUBJECT NAME: Advance Heat Transfer

SUBJECT CODE: 2171911

B.E. 7th SEMESTER

Type of course: Elective

Prerequisite: Engineering Thermodynamics, Fluid Mechanics, Heat Transfer

Rationale: The course is prepared to provide the detailed understanding of conduction,

convection, radiation and phase change. This course is design to learn techniques for heat transfer

enhancement and usage of numerical methods for solving heat transfer problems.

Teaching and Examination Scheme:

Teaching Scheme Credits Examination Marks Total

Marks L T P C Theory Marks Practical Marks

ESE

(E)

PA (M) ESE (V) PA

(I) PA ALA ESE OEP

3 0 2 5 70 20 10 20 10 20 150

Content:

Sr. No. Content No. of

Hrs.

%

Weightage

1 Heat conduction with heat generation: Plane wall and cylinder

with uniform heat generation, applications. Two-dimensional

steady state conduction.

6 14

2 Transient and multi dimensional heat conduction: Exact

solution, use of Heisler and Grober chart, integrated method

6 14

3 Heat Transfer through extended surfaces: Steady state analysis

and optimization, radial fins of rectangular and hyperbolic profiles-

longitudinal fin of rectangular profile radiating to free space.

7 17

4 Convective Heat Transfer:

Forced convection: Introduction, heat transfer in high velocity

flow, empirical relations for pipe and tube flow, flow across

cylinders, spheres and tube banks, liquid-metal heat transfer

Natural Convection: Introduction, empirical relations for free

convection, free convection from vertical planes, cylinders,

horizontal cylinders, horizontal plates, inclined surfaces, spheres

and enclosed space, non-newtonian fluids, combined free and

forced convection

10 19

5 Convection with change of phase: Condensation: Laminar film on a vertical surface, Turbulent film

on a vertical surface, Film condensation in other configurations,

Drop condensation, effect of non-condensable gases in condensing

equipments

Boiling: Pool boiling regimes, Nucleate boiling and peak heat flux,

Film boiling and minimum heat flux, Flow boiling

6 17

6 Radiation heat transfer: Radiation effect on temperature

measurements, radiation properties of a participating medium,

emissivity and absorptivity of gases and gases mixtures, heat

transfer from the human body, radiative exchange and overall heat

transfer in furnaces.

8 19

Suggested Specification table with Marks (Theory):

Distribution of Theory Marks

R Level U Level A Level N Level E Level C Level

10 15 15 15 10 5

Legends: R: Remembrance; U: Understanding; A: Application, N: Analyze and E:

Evaluate C: Create and above Levels (Revised Bloom’s Taxonomy)

Note: This specification table shall be treated as a general guideline for students and teachers.

The actual distribution of marks in the question paper may vary slightly from above table.

Reference Books:

1. D.P. Incropera, P.P. and Dewitt, Fundamentals of Heat and Mass Transfer, Wiley

Eastern

2. Adrian Bejan, Convective Heat Transfer, Wiley India.

3. Cengel Y A, Heat Transfer – A Practical Approach, McGraw Hill

4. Kays, Crawford and Weigand, Convective Heat and Mass Transfer, McGraw Hill.

5. Siegel and Howell, Thermal Radiation, McGraw Hill.

6. Kraus A.D., Aziz, A., and Welty, J., Extended Surface Heat Transfer, McGraw Hill

7. Adrian Bejan, Allan D. Krams, Heat Transfer Handbook, John Wiley & Sons.

8. J. P. Holman, Heat Transfer, McGraw Hill

Course Outcome:

After learning the course, the students should be able to:

Develop ability to apply the basic principles of classical heat transfer in real engineering

application

Analyze the analytical and numerical solutions for heat transfer problem.

Understand the basic concepts of turbulence and their impact on heat transfer

List of Experiments:

1. Experiment on “Heat transfer through composite wall at different temperature”

2. Experiment on “Thermal conductivity of insulating powder (Asbestos powder) ”

3. Experiment on “Heat transfer in turbulent flow”

4. Experiment on “Heat transfer by forced convection”

5. Experiment on “Heat transfer coefficient in natural convection”

6. Experiment on “Heat transfer by radiation: Stefan-Boltzmann Law”

7. Experiment on “Thermal conductivity of metal rod ”

8. Experiment on “Drop and Film wise condensation”

9. Experiment on “Unsteady state conduction heat transfer”

Design based Problems (DP)/Open Ended Problem:

1. Comparison of composite wall made of different materials

2. Calculate cooling capacity of domestic refrigerator

3. Calculate the effect of different fins in heat transfer

Major Equipment:

1. Conduction through Composite Wall

2. Heat Transfer in Natural convection

3. Heat Transfer in Forced Flow

4. Pin-Fin (Natural and Forced Convection)

5. Stefan Boltzmann Constant

6. Emissivity of test plate

7. Drop and Film wise condensation

8. Unsteady state conduction heat transfer

List of Open Source Software/learning website:

1. nptel.ac.in

2. www.learnerstv.com

3. cosmolearning.org

ACTIVE LEARNING ASSIGNMENTS: Preparation of power-point slides, which include

videos, animations, pictures, graphics for better understanding theory and practical work – The

faculty will allocate chapters/ parts of chapters to groups of students so that the entire syllabus

to be covered. The power-point slides should be put up on the web-site of the College/ Institute,

along with the names of the students of the group, the name of the faculty, Department and

College on the first slide. The best three works should submit to GTU.

1

Seat No.: ________ Enrolment No.___________

GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII (NEW) - EXAMINATION – SUMMER 2017

Subject Code: 2171911 Date: 29/04/2017 Subject Name: Advance Heat Transfer(Department Elective - I) 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) What is the difference between film and drop wise condensation? Which is a

more effective mechanism of heat transfer?

07

(b) Explain the function of extended surfaces with classification. 07

Q.2 (a) Derive Temperature distribution relation for cylinder with Steady state and

uniform heat generation.

07

(b) A chemical reaction takes place in a packed bed (k=0.6 W/m 0C) between two

coaxial cylinders with radii 15 mm and 45 mm. the inner surface is at 580 0C

and it is insulated. Assuming the reaction rate of 0.6 MW/m3 in the reactor

volume, find the temperature at the outer surface of the reactor.

07

OR

(b) Obtain an expression for the steady state temperature distribution of two

dimensional rectangular fin having constant thermal conductivity. The fin has

thickness of L in Y-direction and is semi infinite in X- direction. The base

temperature of fin and ambient temperature are t0 and t∞ respectively. Assume

the heat transfer coefficient to be large

07

Q.3 (a) What is lumped system analysis? Derive equation for lumped parameter

Analysis

07

(b) Water in a tank is to be boiled at sea level by a 1-cm-diameter nickel plated

steel heating element equipped with electrical resistance wires inside. .

Determine the maximum heat flux that can be attained in the nucleate boiling

regime and the surface temperature of the heater surface in that case.

Take following properties of water at saturation temperature of 100 0C

ρ l= 957.9 kg/m3, ρ v = 0.6 kg/m3, Prl= 1.75, hfg= 2257 × 103 J/ kg, μl= 0.282 ×

10 -3 kg m/s, Cpl= 4217J / Kg 0C and Csf = 0.006 , n=1, Ccr =0.12

07

OR

Q.3 (a) Draw the boiling curve and identify the burnout point on the curve. Explain

how burnout is caused. Why is the burnout point avoided in the design of

boilers?

07

(b) An ordinary egg can be approximated as a 5-cm-diameter sphere with

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 =1200 W/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 = 0.627 W/m °C , α = 0.151×10-6

m2/s, λ1 = 3.0753 and A1 = 1.9958

07

Q.4 (a) Define: Nusselt Number, Reynolds Number, Prandtl Number and give

conventional generalised basic equation for forced convection using these

numbers.

07

2

(b) Air at 20 0C and 1.013 bar flows over a rectangular container, with top surface

750 mm long in direction of flow and 1 m wide, at 35 m/s. determine the heat

transfer from the top surface maintained at 60 0 C.

use following properties of air at average temperature of 40 0C:

µ= 1.906X10-5 kg/ms, Cp = 1.007 kJ/kg 0C and k= 0.0272 W/m 0C, and

following correlations for finding average heat transfer coefficient

Nu = 0.664 (ReL)0.5 (Pr)0.33 if ReL ≤ 5 × 105

Nu = [0.037 (ReL)0.5 – 850] (Pr)0.33 if ReL > 5 × 105

07

OR

Q.4 (a) Explain briefly Flow boiling regimes. 07

(b) Air at 2 bar and 40 c is heated as it flows through a 30mm diameter tube at a

velocity of 10m/s. If the wall temperature is maintained at 100 0C all along the

length of the tube, make calculations for heat transfer per unit length of the

tube. Proceed to calculate the increase in bulk temperature over one meter

length of the tube. Use Nu=0.023 (Re0.8 )(Pr0.4)

And take following thermo-physical properties of air at the average film

temperature of 70 0C

µ=20.6×10-6 Ns/m2, Cp=1.009 kJ/Kg 0C, k=0.0297 W/m 0 C and Pr=0.694

07

Q.5 (a) Explain all the different mechanisms of heat transfer from the human body (a)

through the skin and (b) through the lungs.

07

(b) Explain effect of radiation on measurement of temperature by a bare

thermometer. A bare thermometer measuring the temperature of a gas body

reads 600 K. The surrounding walls are 500K. The thermometer bulb is 3mm in

dia and is spherical, its surface emissivity being 0.7. The convective heat

transfer coefficient over the surface is 40 W/ m2K. Determine the gas

temperature and error involved.

07

OR

Q.5 (a) Write a short note on Emissivity and absorptivity of gases and gas mixtures 07

(b) Consider a man of surface area 1.8 m2 and convective heat transfer coefficient

4 W/m2 0C wearing summer clothes whose thermal resistance is 0.93 m2 0C/W.

The man feels very comfortable (33 0C) while standing in a room maintained at

22°C with same air temperature. The air motion in the room is negligible. If this

man were to stand in that room unclothed, determine the temperature at which

the room must be maintained for him to feel thermally comfortable. Take indoor

radiation heat transfer coefficient 4.7 W/m2 0C

07

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1

Seat No.: ________ Enrolment No.___________

GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII(NEW) • EXAMINATION – WINTER 2016

Subject Code:2171911 Date:18/11/2016

Subject Name: Advance Heat Transfer(Department Elective - I)

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. Tables for properties of air and water are permitted.

Q.1 (a) Write the finite-difference equations under steady-state conditions for the

following situations:

(i) (ii) (iii)

07

(b) In a wind tunnel, air at 5 m/s flows over a flat plate and 15oC, 1 m x 0.8 m in

size. The surface temperature of plate is 35oC. One of the side of the plate is

arranged parallel to the flow direction, such that the heat transfer is lesser,

estimate:

(i) Rate of heat transfer from the one side of plate

(ii) Initial rate of cooling per hour of the plate, if mass of the plate is 5 kg

and specific heat is 875 J/kg.K.

(iii)If the flow is turned off, compute the heat flow rate from the upper

surface of the plate in still air at 15oC.

(iv) What is the percentage change in heat flow rate?

The thermo-physical properties of air are as follows:

ρ= 1.1707 kg/m3 , = 15.172 x 10-6 m2/s , k= 0.02614 W/mK, Cp=1007 J/KgK,

Pr = 0.7075

Use the following correlations:

For free convection: Nu= 0.27 (Gr. Pr) 0.25

For forced convection: Nu= 0.664 (Re) 0.5 (Pr) 0.33

07

Q.2 (a) A cylindrical furnace whose height and diameter are 5 m contains gases at 1200

K and a total pressure of 2 atm. The composition of the gases is determined by

volumetric analysis to be 85 percent N2, 8 percent H2O, 7 percent O2.

Determine the effective emissivity of the gases. Consider L = 0.6D

Make use of following charts

07

2

(b) Consider three consecutive nodes n - 1, n, and n + 1 in a plane wall. Using the

finite difference form of the first derivative at the midpoints, show that the

finite difference form of the second derivative can be expressed as

07

OR

(b) Define these terms used in the finite difference formulation: node, nodal

network, volume element, nodal spacing, and difference equation. 07

Q.3 (a) What is an irregular boundary? What is a practical way of handling irregular

boundary surfaces with the finite difference method? 07

(b) In a production facility, large brass plates of 4 cm thickness that are initially at a

uniform temperature of 20°C are heated by passing them through an oven that

is maintained at 500°C. The plates remain in the oven for a period of 7 min.

Taking the combined convection and radiation heat transfer coefficient to be h

= 120 W/m2.°C, determine the surface temperature of the plates when they

come out of the oven using Heisler charts (given at end of paper).

The properties of brass at room temperature are k = 110 W/m·°C, ρ = 8530

kg/m3, Cp = 380 J/kg · °C, and α = 33.9 10-6 m2/s

07

OR

Q.3 (a) Define fin efficiency and fin effectiveness. Why is the insulated-tip solution

important for the fin problems? 07

(b) Explain radial fins of rectangular and parabolic profiles. 07

Q.4 (a) Explain the mechanism of laminar film condensation on a vertical plate. 07

(b) The water flows at 20oC enters a 2 cm diameter tube with a velocity of 1.5 m/s.

The tube is maintained at 100oC. Find the tube length required to heat the water

to a temperature of 60oC.

The properties of water are:

ρ = 992.2 kg/m3 , = 0.659 x 10-6 m2/s , k= 0.634 W/mK ,Cp= 4.174 kJ/KgK,

Pr= 4.31

07

OR

Q.4 (a) Discuss the various regimes of pool boiling with neat sketch. 07

(b) Explain heat transfer in high velocity flow with neat sketch. 07

Q.5 (a) What is Beer’s law?

Why do surfaces absorb differently for solar or earthbound radiation?

07

3

(b) How is the insulating effect of clothing expressed? How does clothing affect

heat loss from the body by convection, radiation, and evaporation? How does

clothing affect heat gain from the sun?

07

OR

Q.5 (a) What is latent heat? How is the latent heat loss from the human body affected

by (a) skin wettedness and (b) relative humidity of the environment? How is the

rate of evaporation from the body related to the rate of latent heat loss?

07

(b) A long, circular aluminum rod is attached at one end to a heated wall and

transfers heat by convection to a cold fluid.

(i) If the diameter of the rod is tripled, by how much would the rate of heat

removal change?

(ii) If a copper rod of the same diameter is used in place of the aluminum, by

how much would the rate of heat removal change?

07

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