HOMEWORK No 9
DR. CONG NGOC THANG
HEAT TRANSFER
Problem 1:
Use orderofmagnitude analysis to show that the characteristic time for radiation
transport is on the order of L /c, and is thus negligible for the typical heat transfer
problem.
Problem 2:
Use W
MIDTERM 1008
HEAT TRANSFER
1. Two objects have the same areas and the same emissivities but object A has a
temperature of 150 K and object B has a temperature of 450 K. How much
radiation is emitted per second from object B compared to object A?
2.
If yo
MIDTERM 1007
HEAT TRANSFER
1. In outer space heat transfer by convection and conduction cannot occur. How is
thermal energy removed from a spacecraft?
2. Two objects have the same areas and the same emissivities but object A has a
temperature of 150 K an
MIDTERM 1006
HEAT TRANSFER
1. In outer space heat transfer by convection and conduction cannot occur. How is
thermal energy removed from a spacecraft?
2. You remove a roasted chicken from the oven but will not be ready to serve it for
15 minutes. What ca
MIDTERM 1005
HEAT TRANSFER
1. In outer space heat transfer by convection and conduction cannot occur. How is
thermal energy removed from a spacecraft?
2. You remove a roasted chicken from the oven but will not be ready to serve it for
15 minutes. What ca
MIDTERM 1004
HEAT TRANSFER
1. The inner and outer surfaces of a 0.55cm thick 5m by 5m window glass in
winter are 9C and 4C, respectively.If the thermal conductivity of the glass is
0.78 W/mK, determine the amount of heat loss through the glass over a
MIDTERM 1003
HEAT TRANSFER
1. The inner and outer surfaces of a 0.6cm thick 3m by 3m window glass in winter
are 14C and 9C, respectively.If the thermal conductivity of the glass is 0.78
W/mK, determine the amount of heat loss through the glass over a
MIDTERM 1002
HEAT TRANSFER
1. The inner and outer surfaces of a 0.3cm thick 4m by 4m window glass in winter
are 10C and 9C, respectively.If the thermal conductivity of the glass is 0.78
W/mK, determine the amount of heat loss through the glass over a
MIDTERM 1001
HEAT TRANSFER
1. The inner and outer surfaces of a 0.5cm thick 2m by 2m window glass in winter
are 10C and 3C, respectively.If the thermal conductivity of the glass is 0.78
W/mK, determine the amount of heat loss through the glass over a
HOMEWORK No 7
DR. CONG NGOC THANG
HEAT TRANSFER
Problem 1:
Air at atmospheric pressure and 90F flows past a flat plate maintained at 600F. The
plate is 3 ft long and the air velocity is 105 ft/sec. Find the heat transferred from the plate,
per foot of wid
HOMEWORK No 5
DR. CONG NGOC THANG
HEAT TRANSFER
Problem 1:
Redesign the thermal outfall system so that the surface area of the river which is heated to
temperatures greater than 80F is one acre or less.
Problem 2:
Show that the timeaveraged form of the c
HOMEWORK No 4
DR. CONG NGOC THANG
HEAT TRANSFER
Problem 1:
If the gap between the glass plates were filled with a low viscosity oil, would the effect of
convective transport be increased or decreased?
Problem 2:
Air at 72oF and I atm (v = 0.16 cm'/sec) fl
HOMEWORK No 2
DR. CONG NGOC THANG
HEAT TRANSFER
Problem 1:
Solve for the temperature field in a cylindrical rod subject to the boundary conditions
B.C.I T = To, z=O
B.C.2 T = Ta, z=L
B.C.3 T = Ta, r = ro
Problem 2:
Use Eq. 3.172 to obtain an expression f
HOMEWORK No 6
DR. CONG NGOC THANG
HEAT TRANSFER
Problem 1:
Nitrogen at atmospheric pressure is to be heated from 60F to 120F in smoothwalled
tubes whose inside walls are maintained at 140F. If the inner diameter is ~ in. and the
average velocity of the n
HOMEWORK No 8
DR. CONG NGOC THANG
HEAT TRANSFER
Problem 1:
A heat exchanger is to consist of 300 tubes 5 ft long and 1in. in outer diameter. The
tubes are to be arranged in 15 staggered rows with transverse and longitudinal
pitch of 2 in. For a tube surfa
HOMEWORK No 1
DR. CONG NGOC THANG
HEAT TRANSFER
Problem 1:
Given a long copper wire in still air at 68F, calculate the maximum current it can carry if
the maximum temperature of the wire is not to exceed 200F. Take the specific resistance
to be 1.6 x 106
HOMEWORK No 3
DR. CONG NGOC THANG
HEAT TRANSFER
Problem 1:
Consider a flat plate, infinite in the y and zdirections, which is initially at a uniform
temperature To. At a time (4.5) t = 0 the surface x = 0 is suddenly raised to a new
temperature TJ while
HOMEWORK No 10
DR. CONG NGOC THANG
HEAT TRANSFER
Problem 1:
Lubricating oil at 1500P is to be cooled to 105P by water available at 700P in a dOUblepipe, countercurrent flow, heat exchanger. The oil and water flow rates are 225 and
1951bm/hr respectively,
A HEAT TRANSFER
HEAT
THIRD
TEXTBOOK EDITION
John H. Lienhard IV / John H. Lienhard V
A Heat
Transfer
Textbook
Lienhard
& Lienhard
Phlogiston Press
ISBN 0971383502
PSB 01040249
A Heat Transfer Textbook
A Heat Transfer Textbook
Third Edition
by
John H.
Chapter 5
Heat Exchangers
5.1
Introduction
Heat exchangers are devices used to transfer heat between two or more uid streams
at dierent temperatures. Heat exchangers nd widespread use in power generation,
chemical processing, electronics cooling, aircond
ECH 142Heat Transfer
Spring 2011
Exam 2 (Open book, open notes)
1. A double pipe heat exchanger contains water both inside the tube and in the annulus. The water
enters the annulus at 20C and leaves at 60C, and has a flow rate of 0.2kg/s. The film heat tr
ECH 142Heat Transfer
Spring 2010
Exam 2 (open book and notes)
1. A cocurrent, doublepipe heat exchanger has water in the inner pipe flowing at a rate of 1.1kg/s,
and engine oil in the annular space flowing at a rate of 0.7kg/s. The inlet temperature of
ECH 142Heat Transfer
Spring 2009
5/28/09
Exam 2 (open book, open notes)
water
air
(kg/m3)
1000
1.14
Properties of water and air
CP (kJ/kg.K)
k (W/m.K)
(cm2/s)
4.18
0.60
0.010
1.00
0.026
0.16
Pr
7
0.7
HV kJ/kg
2450

1. Steel pipe with ID 0.10 m and OD 0
1. c ph sau v xc nh hp cht:
C7H12Br MW = 171.04
2. What is the log mean temperature difference? Write the formula for:
 Parallel Flow
 Countercurrent Flow
 Mixed Flow
3. Ti sao c bnh ng v kinh t v chnh tr con ngi mi c c t do?
Tinh thn dn ch xy dng trn
Tr chi : Cp C
Tng thi gian : 60 pht, mi lt chi s c 20 pht
Chia phe: Chng ta s chia cc i lm hai phe. Phe phng th trn i (1 i), phe tn cng cp c
( 2 i)
Chng ta s c 3 lt chi, mi i s c phng th trn ni mt ln.
Lut chi nh sau: i phng th trn ni s c nhim v gi cho bng
Radiation
Thermal radiation occurs through a vacuum or any transparent medium (solid or fluid). It is the
transfer of energy by means of photons in electromagnetic waves governed by the same laws.[1]
Thermal radiation is energy emitted by matter as electr
Convection[edit]
Main article: Convection
The flow of fluid may be forced by external processes, or sometimes (in gravitational fields) by
buoyancy forces caused when thermal energy expands the fluid (for example in a fire plume), thus
influencing its own
Convectioncooling
See also: Nusselt number
Convective cooling is sometimes described as Newton's law of cooling:
The rate of heat loss of a body is proportional to the temperature difference between the body and
its surroundings.
However, by definition,