Page 357 - Mechanical Engineers' Handbook (Volume 4)

346 Heat Pipes 450 Ksintered

Effective Thermal Conductivity, Keff (W/km) 400 Kparallel

Kspheres
350
Kseries
300
Kwrapped screen
250
200
150
100
50
0
0 0.2 0.4 0.6 0.8 1
Porosity
Figure 4 Plot of effective thermal conductivities presented in Table 3.

ƒ Re s q (s)

dK dp d I s l 0 h ƒg ds
(33)
3
ds ds 2 (s) l
for the steady-state evaporating process of a thin film, where the meniscus curvature, K, can
be found by

2
d /ds 2
K (34)
23 / 2
[1 (d /ds)]
Using the following boundary conditions

BULK VAPOR
Meniscus film region

Evaporating
thin film region
Nonevaporating
thin film region
s Control
volume
BULK LIQUID δ

s
s Heat flux

Figure 5 Thin-film evaporation.