• Boiling Heat Transfer Correlations
  • Different models exist and there is no single view on this aspect.
  • We shall just list the correlations for application purposes
• Nucleate Boiling
  • Rohsenow’s correlation is most popular

                         

• C_s,f , n depends on Surface/fluid combination (Given in Table 10.1 of Incropera and Dewitt). Typical values are C_s,f = 0.013) n=1.
• Critical Heat Flux
  • Lienhard’s correlation

                          

• Minimum Heat Flux (Leidenfrost’s point)
  • Adapted from Zuber’s correlation

Not very reliable

• Film Boiling
  • Both Convection and radiation effects are important.
  • Bromley’s correlation is most quoted

                      

                      

	Vapour properties are evaluated at average film temperature, liquid property at saturated temperature

For cylinder and sphere, the convective heat transfer coefficient is modified as

           

where D is the diameter
The value of C for Horizontal cylinder = 0.62, for sphere, C = 0.67.

As an approximation, when