Heat transfer from a flat surface to a moving fluid

257 Pages·21.683 MB·English

by  Ali, Abdel Fattah Hassan

5 "°\ \ ^
ProQuest Number: 10800369
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Th® writer wishes to his deep gratitude,
to Mr® Y®G* Davies* B«So®(Eng* ) M»X»3trfc6h»S®.
for Ms constant guidance, advice and ©noorjmgemeat.
in the • supsrcLsion ©f this research w©rka
He further &okno@rledges 'the assistance received
from Mr® W®J« Beok* K.jBiag*,-3SoI*M9oh*B* and. Mr* A®JS
BeSca(E&g* )3 A*M*I»Medh*S* in the course '
of Ms work; also the helpful ©cooperation of the
staff of the Workshop and' the EXectrio&l department
at the Polytechnic®
LIST OF & M 30LS
The following symbols were. used 1b this thesis, except whan
otherwise stated s
jm m mo m L qu/®xtxis
1 'Area of heat transfer surface, s<i«ft*
a 0©©ffi©ient ©f volumetric expansion (for perfect gas « «L )
' r
b Perimeter* ft®
Op Specif is heat at constant pressure, B«ThFJ/lh&0p
X> Di&s&ter, ft*
Da Bspiv&Leat diameter a I*. & ft*
b
o
: F Frictional $&e® per unit area of surface* lb ic g/ft^;'>,.lb/ft
f Friction factor* dimensionlesa*
G Mass velocity* lb/hr* S€j['3 ft®
g Local acceleration dm to- gravity, approsdmtgly 52o'£* ft/see
or 4*17 x 10^ ft/hr?*-...
h . Surface convective conductance coefficient of heat transfer
B*Xh.*tf/ft2 hr.®?.
hm ’ Average vain© of h*
Ii _ Maxinsam value of h
max®
^,hp*.*hg Local value of h«
K Thermal conductivity, B*Xh®IJ/ft9lir®0F
L Length, ft*
Lt|i Thermal 'length i®e* the. heated length®
“Hot length measured from, the end of the honeycomb*'
m Mass* lb*
Gout
:<*>
P Pressure. lb/sq..ft* ^
Q • Quantity of heat. B.Th.11*
ci Convective conductance heat transfer rate, B«3!h«U/hr«
Radiation. heat transfer rats® B.Th.U./br.
(R.H.) Relative- humidity®
P
S Cross-section. ft
T Tenperature. &©g» F.(Absolute)
t 'Temperature, dag* F® 5
t for room temperature .or inlet of theh ulk of the air
a stream temperature*
for outlet of the bulk ©f the air stream teisper&tus
o
t for average temperature of the hulk of the air stream
m temperature ■ = (t * t^) / 2
t for average tesperature of the hot surface*
for film temperature » _{t t ^w) / 2
for average temperature of tunnel walls*
V
V Average velocity of the air stream. ft/seo.
v Speoiflo volume ( ) * ou*ft»/lb*
x Distance along x»axis,' ft®
Greek
0 Temperature difference °P
/A Absolute viscosity, lb/ft* hr.-
“I • Kinematic viscosity* ft^/hr*
Density lh/ou*ft.
Time* in hours unless otherwise stated®
Ill
a
LIST OF m s
H6i :
1 « 10 »*• Calibration of wind tunnel {observations}
14 -» 15 «©«> Calibration of wind tunnel (results)
16 «* 26 . **« Observations (First heater)*
27 23 « 29 »«• Results - average coefficient of heat transfer
(First heator)
30 -» 31 ■- 32 Physical constants end dimensicnless numbers
calculated at tap* (tm) (First heater)
33 « 34 “ 55 *«« Bagrsical constants ©n& dijBenaionless nujabors
calculated, at temp* (tf) (First heater)
36 «, 37 « 35 Temperature distribution over the hot surface
(First heater)*-'
39 - 40 «*« Results• » inlet thermL effect (.First heater)
41 ««• '; Observations' • Second, heater cospared with
first heater*
42 “ 45 Observations - Second heater*
46 • Results *» local coefficient of heat transfer
(Second heater)
47 ««« • Results *» average coefficient of heat.• transfer
( Second' haater )
48 *«* B^rsioal constants and di&ensiohXess numbers
calculated at tasp* (tm) (Second heater)
49 ««* Physical constants and diioensionless numbers
calculated at tenp* .(tp) (Second heater)
50 »*« RUsselt Rusher (Mi)^ f and Reynolds
number (P©)^ m > (Second heater)
LIST OF FIGURES
Apparatus used by Jurges
Apparatus used by Rowley* Algren *& Blaokshaw.
Apparatus used by Pariid.ee & Hueb sober.
Apparatus umd by Jakob & Dow*
Apparatus used by SI©g©X *Ss Hawkins*
Results obtained by Siegel Sz Bawkins*
Secondary flow in channel corners*
A photograph of the wind tunnl*
Cons true tion of the first heater,
A photograph of the heaters*
The elctrical connection-to'the first heater* ;
Diagram of thermocouples connastioa,
Conneotion diagram of the tunnel motor to-Vickers
motor generator sot*
Final arrangement of the tunnel* heater, and
measuring instruments*
Arrangement of the wind tunnel for calibration
Calibration of 26 gauge copper constant an thermopouples.
Calibration of the wind, tunnel,
A forced convection heat transfer based on (hm) and (%.)
(First heater)*
Comoarison of forced convection heat transfer based on
Oont s-
urea (Gont*)
Fig® 21 C m ipariaon ©f forced correction heat transfer basod on
(hra) and (Ym) with the results obtained fey Jurges and
those obtained by Slog©! & Hawkins*
22, 23
0 Forced convection heat transfer correlation based
L
fX + (Dm) and (He)® (First heater).
23® **» Comparison the exporiiKsental correlation based on
of
(Hu) and (He) calculated at different temperature
.assumptions* (First heater)®
op. p*7
a' io Forced convection heat transfer correlation based
28 **• on
(Hu) and (Fe) (First heater)®
29« Comparison of the' experin&ntal correlation based on
(Ha) and (l^c) calculated at different tsispsy&tui’O
assumptions#
30. *,» Oos^arison between present and previous results obtained
by Jurges and Ellas®
31. Comparison between present and previous results obtained
by Siegel and Hawkins*
32 to 37 Te&tperatur© distribution of the hot plats surface*
38* ■«■■•« Arrangements to measure the air ©ratur© at the
t m m
boundary layer®
39 40
^ £$/••• Tenperatur© me&suressents of the air at boundary layer®
42. . ••• ('tWg - ta) versus rise in temperature (A^) for constant
air velocity*
43* ' (tWg <*• ta) versus mean bulk of the air stream (Vffi) for
.constant rise in temperature -(A t)
44a »•» . Mean temperature as oompared with temperature distribution
43a »»'• Distribution ©f heat flow in the hot brass plat©.
46* „«* Construction of the second heater®
4/®. ••• Electrical circuit for the second haater*
GOnt s*=*
v&i
List of Figures (Pont,) .. .
Pig* 48* *** Temperature distribution of th© hot plate surface*
49* m . A photograph of msasurisxg instruments used for 8©oond
h©at©r«
50 to 55* Local coefficient of oonveotiv© h@at transfer*
56* «•* A forced convection heat transfer hasod on (li.ui^) aisd(Vsa
(Second heater)
57. Comparison "between (hm) obtained by first heater and
(hioj) obtained by second hsafcer*.
58 59
1 in ••• Forced convection heat transfer correlation, based on
(Hu) and (Ho) (Second heater)
61* »*, ■Comparison of the ©xperimsiatal correlation based on
(Mu) and (He) calculated at different teispsratur©
assumptions* (Second heater)
62 63
*** Forced eonvection heat transfer correlation based on
o is
(Wu) and (p©) (Second heater)
65* »•» Qots^&rluon of the ©%p©riia©ntal correlation based on
(Ku) and (P©) calculated at different teijperaturs
assumptions. (Second heater)
66* «*• Comparison between the correlation, obtained bj the firs
heater with those results obtained by th© second
heater*
6?”& «•« Data for gas flowing parallel to a single plane
(MacAdams - p*106) '
67 68
^ §o^** A forced convection E*T* correlation based on Reynolds
• -number and the J factor* (First heater*)
70* m * Comparison of the experimental correlation for Hsynolds
nmiber and the J factor calculated at different
temperature assumptions (First heater*)
ft ftft ft Comparison of Figs* 67 & 73 with the results obtained
by Jorges*.
?2« **» Comparison of Figs* 68 & 74 with .the results obtained
by Siegel and Hawkins*
Cont