Nucleate boiling regime

The single tube values for hb have been correlated by equation 14.2, which applies to the true nucleate boiling regime and takes no account of the factors which eventually lead to the maximum heat flux being approached. As discussed in Volume 1, Chapter 9, equations for maximum flux, often a limiting factor in evaporation processes, have been tested by Palen and Taborek , though the simplified equation of Zuber is recommended. This... 

Water in a tank is to be boiled at sea level by a 1-cm-diameter nickel plated steel heating element equipped with electrical resistance wires inside, as shown in Fig. 10-16. Determine the maximum heat flux that can be attained in the nucleate boiling regime and the surface temperature of the heater in that case. 

Water is boiled at 90 C by a horizontal brass heating elemeni of diameter 7 mm. Determine the maximum heal flux that can be attained in the nucleate boiling regime. 

Water is boiled at 100°C electrically hy an 80 cm long, 2-mm-diameter horizontal resistance wire made of chemically etched stainless steel. Dclerntiiie (n) the rale of hear iransfer to the water and the rale of evaporation of water if the temperature of the wire is 1 t5°C and (b) the maximum rate of evaporation in the nucleate boiling regime. 

The boiler will operate in the nucleate boiling regime, and the design heat flux will not exceed 60 percent of the critical heat flux to provide an adequate safety margin,... 

A pure nucleate boiling regime, which occurs at high values of Co in this regime, the value of hlhi is constant independent of Co. 

FIGURE 5.10 Schematic view of heat flux as a function of A7i On the left of the maximum (the peak heat flux) is the nucleate boiling regime where cylinders of vapor form as the peak is approached. On the right of the peak is the region of film boiling. 

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