Film boiling is usually not desired in commercial equipments, because

Related MCQs

• Boiling point elevation for a strong and concentrated solution is found by Duhring's rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.
• In case of __________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface.
• Boiling of milk in an open vessel is an example of __________ boiling.
• It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30°C. The boiling point of the solution is 110°C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/kg.K. The rate at which the heat has to be supplied in (kJ/min) to the evaporator is
• When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as __________ boiling.
• Film boiling occurs at __________ pressure.
• Water is normally used as a coolant in the heat exchange equipments mainly because of its
• In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by
• The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is
• If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is