NUCLEATE POOL BOILING ON HORIZONTAL TUBES - A CONVECTION-BASED CORRELATION

Pool boiling on horizontal tubes leads to a bubbly flow layer around t he lower periphery of the tube in which bubbles slide around the surfa ce. Heat transfer is by enhanced liquid convection at the surface arou nd the bubble and by rapid evaporation of a thin layer under the slidi ng bubble. Both these mechanisms are a function of the vapour flow rat e and a correlation of the following form is developed: Nu = AF(p)Re(b )0.67 Pr0.4. A is a function of the critical pressure alone, F(p) is a function of the reduced pressure alone and Re(b) is based on the mean vapour mass flux from the surface and the tube diameter. The correlat ion applies to water, refrigerants and organics boiling on tubes of 8- 50 mm in diameter. Bearing in mind the wide scatter found in pool boil ing experiments the correlation fits well with the available world dat a and is particularly suitable for use in equipment design calculation s.