Single-phase Heat Transfer Coefficient Research Articles

Heat transfer during flow boiling of cryogenic fluids in vertical and horizontal tubes

Present knowledge about heat transfer at saturated flow boiling of cryogens has been summarized. Correlations are given for both boiling regions, the forced convective and the nucleate boiling region. Heat transfer at convective boiling can be predicted by a generalized correlation which is a function of the density ratio, p′/ p″, and the flow quality using the respective laminar or turbulent single phase heat transfer coefficient. Nucleate boiling in vertical tubes, however, depends only on the heat flux, the reduced pressure, the tube diameter, the surface roughness and the fluid properties calculated at a standard state. In addition to the above mentioned factors, the perimeter averaged heat transfer coefficient in horizontal tubes is dependent on mass velocity and flow quality. This shows the effect of the partly wetted perimeter at stratification and/or the dry-out of the liquid layer at the top of the tube.