What does Biot number represent?
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.
What is the value of Biot number?
the convective resistance of fluid is negligible. the conductive resistance of the fluid is negligible. the conductive resistance of the solid is negligible.
What does low 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 Biot number and Fourier number?
Fourier number is a measure of heat conducted through a body relative to heat stored. The Biot number is the ratio of the internal resistance of a body to heat conduction to its external resistance to heat convection.
What are Biot and Fourier numbers?
What is the difference between Biot number and Nusselt number?
Biot number uses thermal conductivity of the body (not fluid), whereas Nusselt number uses thermal conductivity of the fluid. Nusselt number can be used for heat exchangers, because fluid convection dominates, calculation of the heat transfer coefficient of various flows such as in pipes.
What is the correct formula for Biot number?
The Biot number equals the product of the heat transfer coefficient and the characteristic length divided by thermal conductivity.
What is difference between Biot no and nusselt no?
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.
Where are fins used?
Uses. Fins are most commonly used in heat exchanging devices such as radiators in cars, computer CPU heatsinks, and heat exchangers in power plants. They are also used in newer technology such as hydrogen fuel cells.
What does the Biot number tell us about a body?
Biot number represents the ratio of conduction resistance within the body to convection resistance at the surface of the body. The Biot number is more likely to be larger for poorly conducting solids since such bodies have larger resistances against heat conduction. What does Biot number tell us?
What is the importance of Biot number in heat transfer?
Biot number. The Biot number (Bi) is a dimensionless quantity used in heat transfer calculations. It is named after the eighteenth century French physicist Jean-Baptiste Biot (1774–1862), and gives a simple index of the ratio of the heat transfer resistances inside of and at the surface of a body.
How is the Biot number used in LSA?
The Biot number is a dimensionless number whose value can be considered as a criterion of applicability for the Lumped System Analysis (LSA). Ratio of transfer between the fluid and body (convection) and within the body (conduction).
When does the error in the Biot number occur?
Generally, in bodies of simple geometry, e.g., plates, cylinders, spheres, the error introduced by the assumption of uniform body temperature will be less than 5% when the internal resistance is less than 10% of the external resistance, i.e., when the Bi < 0.1. Figure 1.