Calculating Grashof's Number for Natural Convection

In summary, the conversation discusses the use of Grashof's number in dealing with natural convection. The film temperature is calculated using the heated plate temperature and the surrounding air temperature. The equation for Grashof's number is provided and the conversation ends with a reference to a book for further clarification.
  • #1
lazypast
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HI

when dealing with natural convection, we use grashof's number. suppose we have a heated plate of temperature Tp. and heat being transferred to surrounding air by convection, air of temp Ta.

So film temp is Tf = 0.5(Tp + Ta)

If grashofs numbers, [tex]Gr = \frac { \beta gL^3 \delta T}{\nu^2}[/tex]

im wondering what [tex]\delta T[/tex] and what [tex]\beta[/tex] we use.

thanks
 
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  • #3
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Related to Calculating Grashof's Number for Natural Convection

What is Grashof's Number and why is it important in natural convection?

Grashof's Number, also known as the Grashof criterion, is a dimensionless number used to predict the onset of natural convection in a fluid. It is important because it helps determine the conditions under which natural convection occurs, which is crucial in many engineering and scientific applications.

How is Grashof's Number calculated?

Grashof's Number is calculated by dividing the product of the fluid's density, acceleration due to gravity, and the square of the characteristic length by the fluid's dynamic viscosity squared.

What is the characteristic length in Grashof's Number?

The characteristic length in Grashof's Number refers to the length scale of the system in which natural convection is occurring. It can vary depending on the geometry of the system, such as the diameter of a pipe or the height of a vertical plate.

What is the significance of the value of Grashof's Number?

The value of Grashof's Number is significant because it determines the type of fluid flow that will occur. A value less than 1 indicates laminar flow, while a value greater than 1 indicates turbulent flow. It also helps determine the heat transfer rate and critical temperature difference for natural convection.

How can Grashof's Number be used in practical applications?

Grashof's Number is used in various engineering and scientific fields such as heat transfer, fluid dynamics, and geophysics. It can help predict the heat transfer rate in heat exchangers, optimize cooling systems, and study natural convection in Earth's atmosphere and oceans.

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