BT-24 Heat Transfer and Pressure Drop Methods for Intube Flow Boiling with Twisted Tape Inserts

L. Huang
2002; rev 05/2012

Using n-pentane and a mixture of n-pentane and p-xylene in the Multipurpose Boiling Unit (MBU), HTRI has collected flow boiling data covering different flow regimes and boiling mechanisms for tubes with twisted tape inserts. From these data, we developed heat transfer and pressure drop methods that incorporate the enhancement effect of swirl flow on intube boiling. The correlations include a C factor for friction pressure drop, a two-phase convection factor, a nucleate boiling suppression factor, and mixture correction factors for twisted tapes. The heat transfer methods cover both subcooled and saturated flow boiling and all regimes from wet-wall to complete vaporization or film boiling. The new and/or revised heat transfer and pressure drop methods accurately predict all our experimental data for twisted tape inserts.