RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY
Department of Mechanical and Aerospace Engineering
650:481 HEAT TRANSFER
MIDTERM EXAM
OPEN BOOK AND NOTES
March 21, 2012
80 Mins.
NOTE: All questions carry equal marks. Clearly give the assumptions and
approxima

PROBLEM 12.3
KNOWN: Thickness and temperature of aluminum plate. Irradiation. Convection conditions.
Absorptivity and emissivity.
FIND: Radiosity and net radiation heat flux at top plate surface, rate of change of plate temperature.
T = 30C
h = 40 W/m2K
S

PROBLEM 7.3
KNOWN: Velocity and temperature of air in parallel flow over a flat plate.
FIND: (a) Velocity boundary layer thickness at selected stations. Distance at which boundary layers
merge for plates separated by H = 3 mm. (b) Surface shear stress and

PROBLEM 6.2
KNOWN: Form of the velocity and temperature profiles for flow over a surface.
FIND: Expressions for the friction and convection coefficients.
SCHEMATIC:
ANALYSIS: The shear stress at the wall is
s =
u
=
y y=0
A + 2By 3Cy 2
y=0 = A .
Henc

PROBLEM 4.2
KNOWN: Two-dimensional rectangular plate subjected to prescribed uniform temperature boundary
conditions.
FIND: Temperature at the mid-point using the exact solution considering the first five non-zero terms;
assess error resulting from using

PROBLEM 3.5
KNOWN: Thermal conductivities and thicknesses of original wall, insulation layer, and glass layer.
Interior and exterior air temperatures and convection heat transfer coefficients.
FIND: Heat flux through original and retrofitted walls.
SCHEMA

PROBLEM 1.2
KNOWN: Thickness and thermal conductivity of a wall. Heat flux applied to one face and
temperatures of both surfaces.
FIND: Whether steady-state conditions exist.
SCHEMATIC:
L = 10 mm
T2 = 30C
q = 20 W/m2
T1 = 50C
qcond
k = 12 W/mK
ASSUMPTIONS

Lecture 16
Flow over Bluff Objects
March 11, 2011
Cylinder in Cross Flow
The Cylinder in Cross Flow
Conditions depend on special features of boundary layer development, including
onset at a stagnation point and separation, as well as transition to turbul

PROBLEM 8.2
KNOWN: Temperature and mean velocity of water flow through a cast iron pipe of
prescribed length and diameter.
FIND: Pressure drop.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state conditions, (2) Fully developed flow, (3) Constant
properties.
3
-6
2

PROBLEM 9.1
KNOWN: Thickness and thermal conductivity of plane wall. Fluid temperatures.
FIND: Expected minimum and maximum steady-state heat fluxes through the wall for (a) free
convection in gases, (b) free convection in liquids, (c) forced convection i

PROBLEM 13.1
KNOWN: Various geometric shapes involving two areas A1 and A2.
FIND: Shape factors, F12 and F21, for each configuration.
ASSUMPTIONS: Surfaces are diffuse.
ANALYSIS: The analysis is not to make use of tables or charts. The approach involves u

RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY
School of Engineering
Department of Mechanical and Aerospace Engineering
650:481 HEAT TRANSFER (3 Cr)
Tentative Schedule:
Week
Topic
Chapter
1
2
3
4
5
6
7
8
9
10
11
12-13
14
15
Introduction to heat transfer proc

Lecture 17
Internal Flow:
General Considerations
March 23, 2011
Entrance Conditions
Entrance Conditions
Must distinguish between entrance and fully developed regions.
Hydrodynamic Effects: Assume laminar flow with uniform velocity profile at
inlet of a

Lecture 18
Internal Flow:
Heat Transfer Correlations
March 25, 2011
Fully Developed Flow
Fully Developed Flow
Laminar Flow in a Circular Tube:
The local Nusselt number is a constant throughout the fully developed
region, but its value depends on the surf

Lecture 19
Free Convection:
General Considerations
and Results for
Vertical and Horizontal Plates
March 30, 2011
General Considerations
General Considerations
Free (natural) convection refers to fluid motion induced by buoyancy forces.
Buoyancy forces m

Review
Review
Be familiar with the expressions of various
familiar with the expressions of various
thermal resistances (Table 3.3, p. 126)
Thermal circuit: steady state, no
circuit: steady state no
generation, one-dimensional
Constant heat transfer rat

Lecture 6
Extended Surfaces
& Fins Problem
02/04/11
Nature and Rationale
Nature and Rationale of Extended Surfaces
An extended surface (also know as a combined conduction-convection system
or a fin) is a solid within which heat transfer by conduction is

Lecture
Lecture 7
Single Fins and Fin Arrays
02/09/11
Review
Review
Essential function of fins: Enhancement of
function of fins: Enhancement of
Heat Transfer
Thin Fin Approximation:
Fin Approximation:
1-D conduction within a solid. Temperature
variatio

Lecture 8
2-D Steady-State Conduction
02/11/11
General Considerations
General Considerations
Two-dimensional conduction:
Temperature distribution is characterized by two spatial coordinates,
e.g., T (x,y).
Heat flux vector is characterized by two direc

Lecture 9
Transient Conduction:
The Lumped Capacitance Method
02/16/11
Transient Conduction
Transient Conduction
A heat transfer process for which the temperature varies with time.
It is initiated whenever a system experiences a change in operating
cond

Lecture 10
Review of Heat Conduction
of Heat Conduction
&
The Finite-Difference Method
02/18/11
Chapter
Chapter 1
1.2 Rate Equations for conduction, convection &
radiation.
1.3 Conservation of energy for a control volume &
at surface
at a surface.
1.6

Lecture 13
Introduction to Convection
Chapter 6 and Appendix D
03/03/11
Boundary Layers: Physical Features
Velocity Boundary Layer
A consequence of viscous effects
associated with relative motion
between a fluid and a surface.
A region of the flow char

Lecture 14
The Reynolds Analogy
03/04/11
The Principle of Similarity
Review
VL VL
=
the Reynolds Number
v
cp v
Pr
= the Prandtl Number
k
Re L
s
2 u *
Cf
=
V 2 / 2 Re L y*
h=
k f T / y
y =0
Ts T
y* = 0
=
hL T *
Nu
=*
kf
y
Nu
u *
y*
(
= f x* , Re L
k