Help with Steady State Heat Transfer Problem

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Discussion Overview

The discussion revolves around a steady state heat transfer problem involving a heat flux source of 400 W/m² and the calculation of heat flux through a surface placed in space with air in between. Participants explore methods to determine temperature distribution and heat flux, considering boundary conditions and geometry.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant seeks assistance in calculating heat flux through a surface using the equation ∫∫(-k∇T)*(n dS) but is uncertain about the term ∇T.
  • Another participant suggests that finding the temperature T requires solving the heat equation with a local heat source and emphasizes the need for boundary conditions, such as wall temperatures.
  • A participant confirms that if the heat source is inside the surface, the heat flux remains 400 W/m² due to energy conservation under steady state conditions.
  • There is a mention that a constant temperature distribution implies that the heat added must equal the heat leaving through the walls to maintain steady state.
  • A participant requests a simple example to aid in visualizing the solution.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and approaches to solving the problem, with no consensus on a specific method or solution. Multiple viewpoints on how to proceed with the calculations remain present.

Contextual Notes

Participants have not fully defined the boundary conditions or the specific geometry of the problem, which may affect the solution process. There is also an assumption of a constant temperature distribution that has not been explicitly verified.

Who May Find This Useful

This discussion may be useful for students or practitioners dealing with heat transfer problems, particularly those involving steady state conditions and the application of mathematical models in thermal analysis.

Diego Saenz
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Hello everyone,

I have this setady state, heat transfer problem; I hope you can help me with it.
I have flux source of 400 W/m² (a lamp), and i want to calculate the heat flux passing through a surface arbitrarily placed and oriented in the space. There is air in between. How can i do this?

I thought that I could use ∫∫(-k∇T)*(n dS)
But i don't know what ∇T is...

Thanks.
 
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That will give you the answer once you've found T. Finding T involves solving the heat equation with a local heat source. You'll need some more boundary conditions to do this, e.g. what are the temperatures of the walls?

If your geometry is simply you can solve for T analytically then differentiate to find your heat flux through a surface.

If not, you'll need some software.
 
Hi mikeph,

My surface is simple, is a square. Is it possible to use this information to solve for T? Can you explain how can I do this?

Thanks
 
If the heat source is inside the surface then it's just 400 W/m^2, this is from energy conservation using the steady state assumption.

If you have a constant temperature distribution then the heat being added inside the box (400) must equal the heat leaving through the walls, otherwise the temperature of the box would have to increase which would introduce a time variation.
 
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I really appreciate your help mikeph.
But I have problems visualizing the solution, could you provide simple example?
 

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