Page 144 - Mechanical Engineer's Data Handbook

THERMODYNAMICS AND HEAT TRANSFER 133

for PrGr= lo5 to lo8
N~=0.47(PrGr)~,”
Nu=O.lO (PrGr)0.j3 for PrGr> lo8
Approximate heat transfer coefficient:

h=1.32(:)”” for Gr=104 to 109 F
h = 1 .2560.j3 for Gr = 10’ to 10”
where : L
6 =temperature difference between cylinder and fluid
-I
d =diameter of cylinder

t

4

Natural convection from a vertical plate or
cylinder

for
N~=0.56(GrPr)~.’~ Par= lo5 to IO9
Nu=0.12 (GrPr)0.j3 for PrGr> 10’
Approximately :

h= 1.42($’”’‘’ for Gr= 104 to 109

h= 1.310°.33 for Gr= lo9 to 1OI2 49 4
Horizontal plate facing upwards

a+b
Characteristic dimension L = -
2
N~=0.54(GrPr)~.~’
for GrPr= lo5 to lo8
N~=0.14(GrPr)’.~~
for GrPr> lo8