What is the continuity condition for the heat flux through a boundary?

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SUMMARY

The continuity condition for heat flux through a boundary separating two media with different thermal conductivities, κ₁ and κ₂, is defined by the equation -κ₁(d[T₁]/dn) = -κ₂(d[T₂]/dn). This indicates that the heat flux, represented by the temperature gradient normal to the boundary, must be continuous across the interface. The temperature distributions in the two media are denoted as T₁(r,θ,φ) and T₂(r,θ,φ), respectively. The correct relationship emphasizes the importance of the normal derivative of temperature at the boundary.

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Thermal engineers, physicists, and students studying heat transfer principles will benefit from this discussion, particularly those focusing on boundary conditions and heat flux continuity in multi-material systems.

LordGfcd
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Assume there is a boundary separates two medium with different heat conductivity [κ][/1] and [κ][/2]. In one medium, the temperature distribution is [T][/1](r,θ,φ) and on the other medium is [T][/2](r,θ,φ). What is the relationship between [T][/1] and [T][/2] ?
Is it - [κ][/1]grad [T][/1]=- [κ][/2]grad [T][/2] or - [κ][/1](d[T][/1]/dn)=- [κ][/2](d[T][/2]/dn) ?
 
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LordGfcd said:
Assume there is a boundary separates two medium with different heat conductivity [κ][/1] and [κ][/2]. In one medium, the temperature distribution is [T][/1](r,θ,φ) and on the other medium is [T][/2](r,θ,φ). What is the relationship between [T][/1] and [T][/2] ?
Is it - [κ][/1]grad [T][/1]=- [κ][/2]grad [T][/2] or - [κ][/1](d[T][/1]/dn)=- [κ][/2](d[T][/2]/dn) ?
If n signifies the normal to the boundary, then the latter is correct.
 

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