Home→ Chemical Heat Transfer →The thermal boundary layer at NPr > 1 ?

Nucleate boiling is promoted __________?
At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe ?
The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co-efficient at this time is __________?
Cpμ/K is termed as the __________ number?
In a single evaporator system, the steam economy __________ by creating vacuum in the evaporator?
In case of a super-cooled solution, which is on the verge of crystallisation, the free energy of the solution as compared to that of the solid is __________?
Maximum heat transfer rate is obtained in __________ flow?
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.) ?
In a shell and tube heat exchanger, floating head is used for __________?
Dittus-Boelter equation used for the determination of heat transfer co-efficient is valid __________?
With increase in temperature, the total emissivity of conductors__________?
A multiple effect evaporator as compared to a single effect evaporator of the same capacity has __________?
Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ?
“The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium”. This is __________ law?
In a forward feed multiple effect evaporator, the pressure is __________?
For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is__________?
The non-dimensional temperature gradient in a liquid at the wall of a pipe is the __________?
The film co-efficient between condensing vapour and metal wall increases with __________?
With increase in temperature, the thermal conductivity of most liquids__________?
In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass __________ through the heat exchanger ?
The driving potential for the crystal growth during crystallisation is the __________ of the solution?
Heat flux, as defined in heat flow is analogous to __________ in electricity flow?
Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)?
LMTD can’t be used as such without a correction factor for the__________?
Heat sensitive materials can be concentrated in an evaporator employing__________?
For what value of Prandtl number, St = f/2 ?
In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid__________?
Grashoff number is given by__________?
If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law?
Which of the following is the most widely used heat insulating material for pipelines carrying steam ?
Evaporator tubes are generally__________?
In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is __________ the outlet temperature of the cold fluid?
Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer?
Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the__________?
Reason for operating an evaporator in multiple effects is to secure __________?
All analogy equations connecting friction factor and heat transfer co-efficient apply only to __________?
Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface) ?
For a laminar flow of fluid in a circular tube, ‘h1’ is the convective heat transfer co-efficient at velocity ‘V1’. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is__________?
A graph between __________ is called Wilson plot?
Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer coefficient is „3k/l’. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade ?
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__________?

The thermal boundary layer at NPr > 1 ?

A. Is thicker than hydrodynamic boundary layer
B. Is thinner than hydrodynamic boundary layer
C. And the hydrodynamic boundary layers are identical
D. Disappears

Correct Answer: Is thinner than hydrodynamic boundary layer ✔

Last Updated: March 03, 2019