Heat transfer to boiling liquids in a single vertical tube thermosiphon reboiler

An experimental investigation of heat transfer to boiling liquids has been carried out on a single tube natural circulation reboiler. Experiments were performed with distilled water, methanol, benzene, toluene, and ethylene glycol to cover a wide range of boiling points and thermophysical properties. The heat transfer section consisted of an electrically heated stainless steel tube 25.56 mm I.D. and 1900 mm long. Uniform heat flux values were used in the range of 4.1 to 43.0 kW/m2 while inlet liquid subcooling was varied from 0.5 to 11.6°C. Liquid submergence levels were maintained around 100, 75, 50, and 30%. All the data were generated with increasing heat flux at atmospheric pressure. The effect of heat flux and liquid submergence on the variation of wall and liquid temperatures have been graphically presented and discussed. The heat transfer coefficients in the nonboiling and boiling regions for all the test liquids have been correlated by two separate correlations in terms of dimensionless groups. The experimental results are compared with different correlations given in the literature.