What is physical significance of these numbers? Fourier number is a measure of heat conducted through a body relative to heat stored . Thus, a large value of the Fourier number indicates faster propagation of heat through a body.
What is Fourier number and its significance?
The Fourier Number (Fo) is a dimensionless group which arises naturally from the nondimensionalization of the conduction equation . It is very widely used in the description and prediction of the temperature response of materials undergoing transient conductive heating or cooling.
What is the physical significance of Biot and Fourier number?
Biot Number expresses the ratio of Heat Conduction Resistance through the solid mass to Heat Convection Resistance between the body and environment showing how the temperature varies from the mass interior to the atmosphere.
What is the significance of Prandtl number?
The Prandtl number is an example of a dimensionless number that is an intrinsic property of a fluid . Fluids with small Prandtl numbers are free-flowing liquids with high thermal conductivity and are therefore a good choice for heat conducting liquids.
What is Biot number explain its physical significance?
The Biot number (Bi) is a dimensionless quantity used in heat transfer calculations . ... This ratio determines whether or not the temperatures inside a body will vary significantly in space, while the body heats or cools over time, from a thermal gradient applied to its surface.
How is Fourier number calculated?
- Fourier Number : Fo = αt/L 2
- Thermal Diffusivity : α = Fo L 2 /t.
- Characteristic Time : t = Fo L 2 / α
- Characteristic Length : L = √αt/Fo.
- Where, Fo = Fourier Number, α = Thermal Diffusivity, t = Characteristic Time, L = Characteristic Length.
What is the significance of Grashof number?
The significance of the Grashof number is that it represents the ratio between the buoyancy force due to spatial variation in fluid density (caused by temperature differences) to the restraining force due to the viscosisty of the fluid.
When would you use a Biot number?
The numerical value of Biot Number (Bi) is a criterion which gives a direct indication of the relative importance of conduction and convection in determining the temperature history of a body being heated or cooled by convection at its surface .
What is the difference between the Biot number and the Nusselt number?
Biot number indicates how much solid temperature can change quickly based on the convection heat transfer in fluid. Biot number uses thermal conductivity of the body (not fluid), whereas Nusselt number uses thermal conductivity of the fluid.
Which type of condensation is better *?
Drop nucleation, growth, and condensation have important practical consequences. Significantly, heat transfer rates in dropwise condensation can be much higher than in filmwise condensation. Thus dropwise condensation is often preferred to filmwise condensation in heat exchangers.
Can Nusselt number be less than 1?
Nu can not be less than one since it gives relation between conduction and convection of the liquid.
What is significance of Reynolds number?
The Reynolds number, referred to as Re, is used to determine whether the fluid flow is laminar or turbulent. ... Technically speaking, the Reynolds number is the ratio of the inertial forces to the viscous forces . This ratio helps to categorize laminar flows from the turbulent ones.
What is the difference between natural and forced convection?
The key difference between natural and forced convection is that in natural convection, the motion of the fluid is influenced by natural means whereas, in forced convection, the motion of fluids is influenced by external means.
What does Fourier series represent?
Fourier series is just a means to represent a periodic signal as an infinite sum of sine wave components . A periodic signal is just a signal that repeats its pattern at some period. The primary reason that we use Fourier series is that we can better analyze a signal in another domain rather in the original domain.
What is effectiveness of fin?
2 Fin Efficiency and Surface Effectiveness. Fin efficiency is defined as the ratio of actual heat flow of the fin to that which would be obtained with a fin of constant temperature uniformly equal to the base surface temperature, that is, one with infinite thermal conductivity.
What is overall heat transfer coefficient?
The overall heat transfer coefficient, or U-value, refers to how well heat is conducted through over a series of resistant mediums . Its units are the W/(m 2 °C) [Btu/(hr-ft 2 °F)].
