ME 309 Homework #1- Short Answer Questions
Jan 9, 2014: General Heat Transfer Concepts:
1. What are the physical mechanisms associated with heat transfer by conduction,
convection and thermal radiation?
- Conduction is the transfer of heat through a solid
Incropera Problems 2.3 & 2.4
KNOWN: A spherical shell with prescribed geometry and surface temperatures.
FIND: Sketch temperature distribution and explain shape of the curve.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state conditions, (2) One-dimensional conduct
Incropera Problems 2.5 2.8
KNOWN: End-face temperatures and temperature dependence of k for a truncated cone.
FIND: Variation with axial distance along the cone of q , q , k, and dT / dx.
x
x
SCHEMATIC:
ASSUMPTIONS: (1) One-dimensional conduction in x (ne
Incropera Problems 2.11 & 2.12
KNOWN: Two-dimensional body with specified thermal conductivity and two isothermal surfaces
of prescribed temperatures; one surface, A, has a prescribed temperature gradient.
FIND: Temperature gradients, T/x and T/y, at the
Incropera Problems 2.9 & 2.10
KNOWN: Plane wall with prescribed thermal conductivity, thickness, and surface temperatures.
FIND: Heat flux, q , and temperature gradient, dT/dx, for the three different coordinate systems
x
shown.
SCHEMATIC:
ASSUMPTIONS: (1
Incropera Problems 2.1 & 2.2
KNOWN: Steady-state, one-dimensional heat conduction through an axisymmetric shape.
FIND: Sketch temperature distribution and explain shape of curve.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state, one-dimensional conduction, (2) Co
Incropera Problems 2.17 & 2.18
KNOWN: Electrical heater sandwiched between two identical cylindrical (30 mm dia.
60 mm length) samples whose opposite ends contact plates maintained at T .
o
FIND: (a) Thermal conductivity of SS316 samples for the prescribe
Incropera Problems 2.15 & 2.16
KNOWN: One-dimensional system with prescribed surface temperatures and thickness.
FIND: Heat flux through system constructed of these materials: (a) pure aluminum, (b) plain carbon
steel, (c) AISI 316, stainless steel, (d) p
Incropera Problems 2.13 & 2.14
KNOWN: A rod of constant thermal conductivity k and variable cross-sectional area Ax(x) = Aoeax
where Ao and a are constants.
FIND: (a) Expression for the conduction heat rate, qx(x); use this expression to determine the
tem
Incropera Problems 2.21 & 2.22
KNOWN: Diameter D, thickness L and initial temperature T of pan. Heat rate from stove to bottom
i
of pan. Convection coefficient h and variation of water temperature T (t) during Stage 1.
Temperature T of pan surface in cont
Incropera Problems 2.23 & 2.24
KNOWN: Temperature distribution in a one-dimensional wall with prescribed thickness and thermal
conductivity.
FIND: (a) The heat generation rate, q , in the wall, (b) Heat fluxes at the wall faces and relation to
q .
SCHEMAT
Incropera Problems 2.21 & 2.22
KNOWN: Diameter D, thickness L and initial temperature T of pan. Heat rate from stove to bottom
i
of pan. Convection coefficient h and variation of water temperature T (t) during Stage 1.
Temperature T of pan surface in cont
PROBLEM 1.9
KNOWN: Masonry wall of known thermal conductivity has a heat rate which is 80% of that
through a composite wall of prescribed thermal conductivity and thickness.
FIND: Thickness of masonry wall.
SCHEMATIC:
ASSUMPTIONS: (1) Both walls subjected
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-direction,
PROBLEM 1.21
KNOWN: Upper temperature set point, T , of a bimetallic switch and convection heat
set
transfer coefficient between clothes dryer air and exposed surface of switch.
FIND: Electrical power for heater to maintain T
set
when air temperature is T
PROBLEM 1.13
KNOWN: Hand experiencing convection heat transfer with moving air and water.
FIND: Determine which condition feels colder. Contrast these results with a heat loss of 30 W/m2 under
normal room conditions.
SCHEMATIC:
ASSUMPTIONS: (1) Temperatur
PROBLEM 1.5
KNOWN: Inner and outer surface temperatures of a glass window of prescribed dimensions.
FIND: Heat loss through window.
SCHEMATIC:
ASSUMPTIONS: (1) One-dimensional conduction in the x-direction, (2) Steady-state
conditions, (3) Constant proper
Exam 2 TH Soln Problem 1
Monday, May 2, 2016
32 points
7:45 PM
1. A 1 [cm] diameter copper ball heated to 400oC is dropped in an oil tank. The oil temperature is 20oC and the average heat
transfer coefficient is 50 [W/m2K]. What was the average velocity o
ME 309 Heat Transfer
Spring 2014
CHAPTER1. INTRODUCTION
Homework 1 (Due: January 21, 2013)
Part one: problems:
1.1;
1.18;
1.30;
PROBLEM 1.1
KNOWN: Thermal conductivity, thickness and temperature difference across a sheet of rigid
extruded insulation.
FIND
Exam 3 Solution Page 1 Short Answer
Tuesday, May 3, 2016
4:32 PM
Convection Page 1
Exam 3 Problem 2-1 Solution
Tuesday, May 3, 2016
4:20 PM
A steel cylinder with a surface temperature of 100oC is exposed to 25oC air flowing across at 20[m/s]. What is the
Exam 1 Problem 2-1
Tuesday, March 8, 2016
5:28 PM
2.1. Water flows through a thin copper pipe with an outside diameter of 26 [mm] and covered
by a cylindrical layer of 10 [mm] thick insulation with k = 0.080 [W/(mK)] ). The contact
resistance for a unit a
HW Quiz 4 Solution
Tuesday, February 16, 2016
8:24 AM
An ovens walls consist of thin metal sheets sandwiching 5[cm] of insulation with thermal
conductivity of 0.04 [W/(m K)]. The inner wall is exposed to a net radiative flux of 100 [W/m2] and
a convection
PROBLEM 2.5
KNOWN: Symmetric shape with prescribed variation in cross-sectional area, temperature
distribution and heat rate.
FIND: Expression for the thermal conductivity, k.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state conditions, (2) One-dimensional conduc
PROBLEM 6.4
KNOWN: Surface temperatures of a steel wall and temperature of water flowing over the
wall.
FIND: (a) Convection coefficient, (b) Temperature gradient in wall and in water at wall
surface.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state conditions, (
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 5.8
KNOWN: The temperature-time history of a pure copper sphere in an air stream.
FIND: The heat transfer coefficient between the sphere and the air stream.
SCHEMATIC:
ASSUMPTIONS: (1) Temperature of sphere is spatially uniform, (2) Negligible rad
PROBLEM 4.38
KNOWN: Internal corner of a two-dimensional system with prescribed convection boundary
conditions.
FIND: Finite-difference equations for these situations: (a) Horizontal boundary is perfectly insulated
and vertical boundary is subjected to a
60 (MM OAS
ME 309 Heat Transfer . Name:
Closed book/notes with one side of Exam 1 CWID:
one page of notes allowed
Instructions. Closed book, closed notes with one side of one page of notes (A4 size) allowed.
Part 1. Multiple Choices and Short Answer.
1) (
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ME 309 0 M‘t’l on § Heat Transfer Name:
Closed book closed notes with one side Exam 2 CWID:
of one page of notes allowed
Instructions. Closed book and closed notes with one side of one page of notes (A4 size) allowed.
Part 1. Multiple Choices.
1) (