Conclusions
Experimental study has been carried out to investigate air flow
friction and heat transfer characteristics in a high aspect ratio channel
fitted with different rib turbulators for the turbulent regime, Reynolds
number of 4000 to 16,000. The use of the rib turbulators with e/H=0.3
causes a very high-pressure drop increase, specially for the in-line rib
arrangement and also provides considerable heat transfer augmentations,
Nua/Nu0=2.6–4.4, depending on rib geometry. Nusselt number
augmentation tends to increase with the rise of Reynolds number. The
staggered triangular rib should be applied instead of the rectangular
one to obtain higher heat transfer and performance of about 50–65%,
leading to more compact heat exchanger. The best operating regime
for all rib turbulators is found at the lowest Reynolds number values.