The critical heat flux is an important point on the boiling curve and it may be desirable to operate a boiling process near this point. However, one could become cautious of dissipating heat in excess of this amount. Zuber, through a hydrodynamic stability analysis of the problem has developed an expression to approximate this point.
Units: critical flux: kW/m; h: kJ/kg; σ: N/m; ρ: kg/m; g: m/s.
It is independent of the surface material and is weakly dependent upon the heated surface geometry described by the constant C. For large horizontal cylinders, spheres and large finite heated surfaces, the value of the Zuber constant . For large horizontal plates, a value of  is more suitable.
The critical heat flux depends strongly on pressure.  At low pressures (including atmospheric pressure), the pressure dependence is mainly through the change in vapor density leading to an increase in the critical heat flux with pressure.  However, as pressures approach the critical pressure, both the surface tension and the heat of vaporization converge to zero, making them the dominant sources of pressure dependency.
For water at 1atm, the above equation calculates a critical heat flux of approximately 1000 kW/m.