Abstract:

To enhance the heat transfer on shell side of a double-pipe heat exchanger with helical fins on the outer wall of the inner tube, some pin fins were installed along the centerline of the helical channel formed by helical fins. The heat transfer enhanced by these fins was investigated experimentally and the enhancement mechanism was analyzed by applying the field coordination theory. The heat transfer coefficient in the exchanger with helical fins and pin fins was 1.53—2.53 times as much as that with helical fins only at the same pitch and was 3.08—4.87 times that without the fins for Reynolds number ranging from 4000 to 14000. The performance of the exchanger with pin fins and helical fins was much better at the same mass flow rate, pressure drop and pumping power. Reducing the pitch of pin fins by half, the heat transfer was much better. At the same pressure drop and pumping power, the heat transfer in the exchanger with odd-numbered pin fins within one pitch was a little better than that with even-numbered pin fins. The pin fins increased the radical velocity. Accordingly, the resultant effect of temperature field and velocity field improved the heat transfer.