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Fig. 6. Dependency of the combined thermal geometrical parameter
A
∗
on finning
paramemeters at
β
= 30
◦
and Bi = 0.04 (see legends in Fig. 5)
Fig. 7. Dependency of the convective component of the efficiency criterion
K
Q
0
on
the flow mode for various fins crossing angles:
—
β
= 20
◦
; —
β
= 30
◦
;
N
—
β
= 45
◦
cross finning. Within this framework, the energy efficiency of CC for LRE
chamber cooling was estimated, both numerically and analytically.
The coplanar channel efficiency with regard to the convective component
K
Q
0
(at
β >
30
◦
, Fig. 7) reaches considerable values (from 1.5 to 4 and
more), with the thermal geometric parameter
A
∗
being no lower than unity
within the investigated range, this can mean that the coplanar flow has a
positive cooling effect in the whole recommended range of Re numbers.
However, there is no efficiency at
β <
30
◦
.
The final results of the efficiency estimation by the criterion
K
Q
confirm
these expectations. It was also found out that the decisive factor for the
efficiency is determined by the fins crossing angle
β
and the finning Biot
number. Thus, when the angle
β
increases from 30
◦
to 40
◦
,
K
Q
increases
ISSN 0236-3941. HERALD of the BMSTU. Series Mechanical Engineering. 2015. No. 2 51