BT-31 Intube Flow Boiling of Fluids with Noncondensable Gases

L. Huang

Noncondensable gases in boiling fluids bring benefits, as well as complications, to the boiling process. In thermosiphons, for example, circulation increases and the convection heat transfer is enhanced, but noncondensable gases introduce additional vapor-phase resistance. HTRI conducted experimental and theoretical intube flow boiling research for boiling hydrocarbons mixed with noncondensable gases. Flow boiling data were collected over a wide range of operating conditions using n-pentane/ nitrogen, p-xylene/nitrogen, and n-pentane/p-xylene/nitrogen as test fluids. Current HTRI methods for intube flow boiling can predict the data reasonably well at low concentrations of nitrogen. The improved vaporphase resistance method in this report greatly improves our prediction at high concentrations of noncondensables. This report also discusses the non-equilibrium condition with noncondensable gases and provides guidelines for design or rating of heat exchangers with noncondensable gases.