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
NAME_
Drexel University
Mechanical Engineering and Mechanics
MEM 345
Heat Transfer (Spring 2010)
Final Exam
(Open book and closed notes)
Note: Per university regulations, all forms of academic dishonesty will be addressed in a
strict manner. The student m
NAME_
MEM 345
Drexel University
Summer 2009-10
Mechanical Engineering and Mechanics
Midterm Examination 1
(Open book and closed notes)
Note: Per university regulations, all forms of academic dishonesty will be addressed in a strict
manner. The student may
Chapter 2 Introduction to Conduction
The conduction rate equation Considering one-dimensional heat transfer
dT qx kx A dx qx dT " qx kx A dx
Heat flux is a directional quantity
"A" is area normal to the heat flow direction.
Alternative form of the
NAME_
MEM 345
Drexel University
Summer 2009-10
Mechanical Engineering and Mechanics
Midterm Examination 1
(Open book and closed notes)
Note: Per university regulations, all forms of academic dishonesty will be addressed in a strict
manner. The student may
PROBLEM 1.1 KNOWN: Heat rate, q, through one-dimensional wall of area A, thickness L, thermal
conductivity k and inner temperature, T1. FIND: The outer temperature of the wall, T2. SCHEMATIC:
ASSUMPTIONS: (1) One-dimensional conduction in the x-dire
Chapter Five
Transient Conduction
A heat transfer process for which the temperature varies with time, as well as location
within a solid.
It is initiated whenever a system experiences a change in operating conditions.
It can be induced by changes in:
Internal Flow:
General Considerations
Chapter 8
Sections 8.1 through 8.3
Entrance Conditions
Entrance Conditions
Must distinguish between entrance and fully developed regions.
Hydrodynamic Effects: Assume laminar flow with uniform velocity profile at
in
Internal Flow:
Heat Transfer Correlations
Chapter 8
Sections 8.4 through 8.6
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
External Flow:
Flow over Bluff Objects
(Cylinders, Spheres, Packed Beds)
and
Impinging Jets
Chapter 7
Sections 7.4 through 7.8
Cylinder in Cross Flow
The Cylinder in Cross Flow
Conditions depend on special features of boundary layer development, includin
Introduction to Convection:
Flow and Thermal
Considerations
Chapter Six and
Appendix D
Sections 6.1 through 6.8
and D.1 through D.3
Boundary Layer Features
Boundary Layers: Physical Features
Velocity Boundary Layer
A consequence of viscous effects
associa
Radiation Exchange Between Surfaces:
Enclosures with Nonparticipating Media
Chapter 13
Sections 13.1 through 13.3
Basic Concepts
Basic Concepts
Enclosures consist of two or more surfaces that envelop a
region of space (typically gas-filled) and between wh
Radiation: Processes and
Properties
-Basic Principles and DefinitionsChapter 12
General Considerations
General Considerations
Attention is focused on thermal radiation, whose origins are associated
T > 0.
with emission from matter at an absolute temperat
sens
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Irlidterm I Examination
[Cpen book and closed notes
1. To determine the effect of the temperature dependence of the thennal conductivity on the
tempera
CHAPTER THREE
STEADY-STATE ONE DIMENSIONAL HEAT CONDUCTION
Methodology
Specify appropriate form of the heat equation.
Solve for the temperature distribution.
Apply Fouriers law to determine the heat flux.
Simplest Case: One-Dimensional, Steady-State Co
External Flow:
The Flat Plate in Parallel Flow
Chapter 7
Section 7.1 through 7.3
Physical Features
Physical Features
As with all external flows, the boundary layers develop freely without constraint.
Boundary layer conditions may be entirely laminar, la
Two-Dimensional Conduction:
Finite-Difference Equations
and
Solutions
Chapter 4
Sections 4.4 and 4.5
Finite-Difference Method
The Finite-Difference Method
An approximate method for determining temperatures at discrete
(nodal) points of the physical system
MEM 345
HEAT TRANSFER
Heat: A form of energy that appears only in transit
(recall work and heat interactions in your study of
thermodynamics)
What is meant by heat transfer?
Heat Transfer is thermal energy in transit due to temperature difference
For eng
PROBLEM 1.4
KNOWN: Dimensions, thermal conductivity and surface temperatures of a concrete slab. Efficiency
of gas furnace and cost of natural gas.
FIND: Daily cost of heat loss.
SCHEMATIC:
ASSUMPTIONS: (1) Steady state, (2) One-dimensional conduction, (3
PROBLEM 2.3
KNOWN: Hot water pipe covered with thick layer of insulation.
FIND: Sketch temperature distribution and give brief explanation to justify shape.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state conditions, (2) One-dimensional (radial) conduction, (3)
PROBLEM 3.3
KNOWN: Temperatures and convection coefficients associated with air at the inner and outer surfaces
of a rear window.
FIND: (a) Inner and outer window surface temperatures, Ts,i and Ts,o, and (b) Ts,i and Ts,o as a function of
the outside air
PROBLEM 5.2
KNOWN: Plane wall whose inner surface is insulated and outer surface is exposed to an
airstream at T. Initially, the wall is at a uniform temperature equal to that of the airstream.
Suddenly, a radiant source is switched on applying a uniform
Chapter Five
Transient Conduction
A heat transfer process for which the temperature varies with time, as well as location
within a solid.
It is initiated whenever a system experiences a change in operating conditions.
It can be induced by changes in: