Handbook of Turbomachinery Second Edition Revised - Ventech!

Some of the studies have found that converging cooling passages, such
as found in trailing-edge applications, can reduce heat transfer by as much
as 20% compared to the constant-pin height case. A clearance above partial
pins (typical of vane geometries where truncated, or partial length, pin fins
are used adjacent to an impingement tube insert) or gaps between opposing
truncated pins result in reduced heat transfer and friction compared to full
length pins. For these partial length pin fin geometries, the heat-transfer rate
has been found to decrease linearly with increasing clearance from the full
pin value to that for the smooth channel. However, friction loss reduction
was found to be more pronounced than the reduction in heat-transfer
coefficient. Partial length pin fins could be effectively employed in situations
where there is a significant difference between the heat loads of opposite
walls in a cooling passage. The partial-length pin fins would often be used
on the surface where a higher rate of heat transfer is desired. Also these
geometries, with their lower friction loss characteristics, could be employed
in designs where the available pressure drop is limited to preclude full-length
pin fins. For further information and test data on these geometry cases, see
[63].
Pin fins have been effectively combined with turbulators for moderate
increases in heat transfer and friction (Fig. 19). By staggering the
turbulators, a 35% increase in heat transfer can be obtained. A
comprehensive review of pin fin literature related to turbine-cooling
applications is given in [78].
Figure 19 Pin fin geometry definition.
Copyright © 2003 Marcel Dekker, Inc.