AUGMENTING THE HEAT-TRANSFER BY TURBULATING PLANE CHANNEL FLOWS IN THE LOW RANGE OF THE REYNOLDS-NUMBER

We represent an experimental study of fluid dynamic and heat transfer behaviour in plane channels at Re below 2000. The experimental study c onsidered different turbulators as a means of augmenting the fluid-wal l heat transfer. It included flat grid or fins placed in mide-channel, corrugated nets and cylinders in distant in-line and staggered arrang ements. Turbulence parameters in the channel with the grid were measur ed. Turbulence intensity was up to 20% and over at some locations. The influence of turbulator parameters on the critical Re number value an d on some turbulence parameters was determined. Hydraulic drag and hea t transfer similarity equations for channels with turbulators of all t ypes were compiled. Corrugated nets were most effective, they increase d Nu by a factor up to 3.5 and more. General principles for the heat t ransfer augmentation by the means of effective turbulation at the low range of Re were formulated. The results are intended for design calcu altions of modern, efficient heat exchangers, as well as for evaporati on coolers and heat-recovery units.