BT-30 Tubeside Boiling in Vertical Upflow and Downflow

L. Huang

2004; rev 10/2005

HTRI conducted extensive experimental research on upflow and downflow boiling simultaneously in a vertical serpentine test section of our Multipurpose Boiling Unit (MBU). The data cover a wide range of operating conditions using five test fluids: water, n-pentane, p-xylene, mixtures of n-pentane and p-xylene, and a C5 to C11 hydrocarbon mixture. Based on the data, we developed improved boiling heat transfer and pressure drop methods, including

• a less conservative upflow pressure drop method for non-aqueous fluids with r_l over r_v > 90
• a downflow boiling pressure drop method that includes static head gain
• an improved upflow convective boiling correlation that is more accurate at low heat flux and in laminar and transition flow regimes
• an accurate downflow boiling heat transfer method based on flow regimes

This report points out the turnaround enhancement effect near dry-wall conditions and discusses the 180-degree return effect on downflow tube wall dryout mechanisms in mist and film boiling.