Which area is used in case of heat flow by conduction through a cylinder ?
Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place
The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is
Finned tube heat exchangers
The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation.
Which one gives the monochromatic emissive power for black body radiation ?
For what value of Prandtl number, St = f/2?
In a shell and tube heat exchanger,
Dietus-Boelter equation used for the determination of heat transfer co-efficient is valid
The equation, , corrosponds to __________ analogy.
For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it
Out of the following four assumptions used in the derivation of the equation for LMTD , which one is subject to the largest deviation in practice ?
Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because
Resistance to heat flow by conduction is proportional to (where, t & ρ are thickness & density of the material respectively and A = area normal to the direction of heat flow. )
Temperature profile in steady state heat transfer is
For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it
When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as __________ boiling.
Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter)
Stefan-Boltzman law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in oC T = absolute temperature in oK )
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is
What is the unit of thermal conductivity ?
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 30oC. The boiling point of the solution is 110oC, 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
It is not preferable to use superheated steam in evaporators, because of its very
The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of 'n' is exactly 4 for
LMTD for counterflow and prallel flow heat exchanger will be the same, when the