Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer cannot take place__________?
The thickness of condensate layer in filmwise condensation depends on the__________?
The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation?
Steam economy in case of a triple effect evaporator will be __________?
In a forward feed multiple effect evaporator unit__________?
Dropwise condensation is promoted on a/an __________ surface?
Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger ?
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__________?
Fqra cold viscous feed, backward feed gives __________ than forward feed?
The Graetz number is concerned with the__________
The unit of conductance in SI unit is__________?
Which of the following has the lowest Prandtl number ?
In case of a multipass shell and tube heat exchanger, the temperature drop in the fluid __________?
The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the__________ ?
Nusselt number is a function of Prandtl number and __________ number of fluid in natural convection heat transfer?
Radiation energy is emitted by all the substances, which are above__________?
The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is__________?
Loss of heat from untagged steam pipe to the ambient air is by __________?
In Biot number, the characteristic length used is the ratio of the __________ of the solid?
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?
Stefan-Boltzmann law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K) ?
The equation, (NSt × N2/3 Pr) = f/2, is the __________ analogy ?
The range of electromagnetic spectrum important in heat transfer by radiation is __________ microns?
Boiling point of a solution according to Duhring’s rule is a linear function of the __________ of water?
Prandtl number for most of dry gases is about__________?
Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the__________?
The purpose of providing expansion bellows in the shell of tubular exchanger is to __________?
Multipass heat exchangers are used__________?
It is not recommended to use a 1-2 shell and tube heat exchanger for a particular heat duty, whenever the LMTD correction factor is__________?
Finned tube heat exchangers__________?
Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator?
The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter D. as __________?
For heat flow through very thick walled cylinder, use __________mean radius?
In a shell and tube heat exchanger, the shell side fluid velocity can‟t be changed by changing the__________?
LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counter-flow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow?
The maximum heat transfer co-efficient from steam heating will be attained when the steam is__________?
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__________?
Which of the following has maximum thermal conductivity ?
Thermal diffusivity of a material __________?
Nusselt number is the ratio of the temperature gradient at the wall to__________?
What is the unit of thermal conductivity ?
Tubes are held between top and bottom tube sheets in Calandria type evaporator by keeping__________?
What is the emissivity of a black body ?
In SI units, thermal conductivity is expressed in__________?
In pipe flow, heat is transferred from hot wall to the liquid by__________?
Heat transfer rate described by Fourier’s law will decrease, if the __________ increases?
In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will__________?
Which one gives the monochromatic emissive power for black body radiation ?
Absorptivity and reflectivity of a perfect black body are respectively __________?
Water is normally used as a coolant in the heat exchange equipments mainly because of its__________?
Stefan-Boltzmann law applies to __________ body?

In sub-cooled boiling ?

A. Temperature of the heating surface is less than the boiling point of the liquid
B. Temperature of the heating surface is more than the boiling point of the liquid
C. Bubbles from heating surface are absorbed by the mass of the liquid
D. Very large vapour space is necessary

Correct Answer: Temperature of the heating surface is more than the boiling point of the liquid ✔

Last Updated: March 03, 2019