Can Biot number be greater than 1?
Biot numbers much larger than 1 indicate more difficult problems due to non-uniformity of temperature fields within the object. It should not be confused with Nusselt number, which employs the thermal conductivity of the fluid and hence is a comparative measure of conduction and convection, both in the fluid.
What is LC in heat transfer?
Lc [m] is the characteristic length of a material, h [W/(m² * K)] is the heat transfer coefficient at the material’s surface, k [W/(m * K)] is the thermal conductivity of the material. Bi is the resulting Biot number.
What is infinite plate in analysis of transient heat conduction?
Transient Heat Conduction in an Infinite Plate With a Transverse Circular Cylindrical Hole. The boundary conditions are zero temperature on the cylindrical surface and arbitrary but axisymmetric temperature distributions on the plane surfaces.
What does a small Biot number mean?
Because the Biot number is the ratio between the external resistance of a body to convection energy exchange and internal resistance to transmitting energy by conduction, a small Biot number implies low resistance to transmission by conduction, and therefore very low temperature gradients within the body; thus leading …
What is Nusselt number formula?
the Nusselt number, which is NuDh = 890. the hydraulic diameter of the fuel channel is: Dh = 13,85 mm. the thermal conductivity of reactor coolant (300°C) is: kH2O = 0.545 W/m.K. the bulk temperature of reactor coolant at this axial coordinate is: Tbulk = 296°C. the linear heat rate of the fuel is: qL = 300 W/cm (FQ ≈ …
What is H in Nusselt number?
h = convective heat transfer coefficient.
Which is the fastest mode of heat transfer?
Radiation
Radiation: Thermal radiation generated from electromagnetic waves. Radiation occurs through vacuum or any other material medium. The heat is transferred at the speed of the electromagnetic wave in the medium, which is the speed of light in the medium. So radiation is the fastest among the three due to this reason.
What is the correct formula for Biot number?
What is the correct formula for the Biot number? Biot number formula h [W/(m² * K)] is the heat transfer coefficient at the material’s surface, k [W/(m * K)] is the thermal conductivity of the material. Bi is the resulting Biot number.
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.
Who found Nusselt number?
Wilhelm Nusselt
nondimensional group which is named the Nusselt number after Wilhelm Nusselt (1882–1957). For the formal relation between h and Nu see Equation (2).
What are the 4 types of heat transfer?
Various heat transfer mechanisms exist, including convection, conduction, thermal radiation, and evaporative cooling.
Which is the correct formula for the Biot number?
The Biot number is defined as where kf is the film mass transfer coefficient, dp is the particle diameter, and Deff is the effective diffusion coefficient. The kf value of bovine serum albumin in silica monoliths was calculated to be about 2 × 10 – 5 ms – 1 and the effective pore diffusivity about 2 × 10 – 12 m 2 s – 1 [ 82 ].
Are there any problems with a small Biot number?
In general, problems involving small Biot numbers (much smaller than 1) are thermally simple, due to uniform temperature fields inside the body.
What is the Biot number for a monolith?
The particle diameter must be replaced for monoliths by the diffusional length [78 ]. The Biot number is defined as where kf is the film mass transfer coefficient, dp is the particle diameter, and Deff is the effective diffusion coefficient.
When is the fouling Biot number is large?
When the fouling Biot number is large, the overall heat transfer resistance is dominated by fouling. When the fouling Biot number is small, the overall heat transfer resistance is dominated by factors other than fouling.