EXPERIMENTAL INVESTIGATION OF ENHANCEMENT HEAT TRANSFER OF INSERT TWISTED TAPE OF CIRCLAR CUT WITH WIRE COIL IN THE DOUBLE PIPE HEAT EXCHANGER

The combined effect of wire coil with twist tape inserted in a circular tube using hot air as the test fluid on heat transfer rate and pressure drop were investigated experimentally. The twisted tape used in this work is made of an aluminum sheet with dimensions (1250 mm length, 18 mm wide, 1 mm thick, twist ratio y =8 and y=5.8). The wire coil was made of copper with diameter (d=3mm), the wire coil with two coil pitch ratio (CR=p/d=10 and CR= p/d=5). Reynolds number used in experiments ranged between (9648 to 18144) and the inlet temperatures for hot and cold fluid are 750C and 300C respectively. The experimental results showed that combined wire coil with twisted tape gives 1.268 enhancement efficiency higher than those with each device alone and plain tube, also give better performance as compared to the twisted tape and wire coil alone.