Boiling and Condensation Questions and Answers

Answer: C

The shape of the heating surface is the property that does not affect nucleate boiling in the key. Nucleate boiling depends on the heating surface material and its roughness (which decides the nucleation sites), the liquid properties, the pressure and the agitation. The first two and the last are factors named in the key as affecting it, so the third option, shape of the heating surface, is the one that does not.

In nucleate boiling the number of active bubble sites and the rate of bubble growth set the heat flux, which is why surface roughness, liquid properties and pressure matter, in the key's view, more than the geometry of the surface.

Answer: B

Pool boiling is the boiling heat transfer phenomenon that occurs in steam boilers with natural convection, as the key says. In pool boiling the heated surface is submerged in a pool of liquid that is not forced to flow, and the movement of the fluid is due to the buoyancy of the bubbles and natural convection. Forced convection boiling needs a pump to make the liquid flow past the surface, so it is not the one for natural convection.

Pool boiling is different from flow boiling, in which the liquid is forced through a tube, so it is the case that goes with natural convection.