Thermal Diffusivity in practice

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The discussion focuses on estimating heat flow between two gases separated by a wall in a heat exchanger, particularly when one gas's temperature changes due to an external agent. Thermal diffusivity is identified as a key factor, but its application is unclear since it is expressed in mm²/sec rather than the expected mm/sec. The assumption of uniform temperature across the wall's surface simplifies the analysis, but diffusion through the wall's thickness remains a concern. An electrical analog is considered for easier analysis, although a direct correlation for thermal diffusivity is not readily available. The solution involves applying the 1D heat equation with specific boundary conditions to accurately model the heat transfer.
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I have a system with two gasses separated by a wall as in a heat exchanger. One of the gasses changes temperature by the action of an outside agent and I'm trying to estimate the heat flow between the two gasses over time.
I know that thermal diffusivity is a factor in this, but I don't know how to apply the numbers given for it to my situation. The units for thermal diffusivity are something like mm2/sec. I can assume that the temperature over the surface of the wall is uniform, so I don't have to worry about diffusion in those dimensions, but I do need to account for diffusion through the thickness of wall. I would expect to need a factor in mm/sec, but I have mm2/sec.
Also, I was thinking that an electrical analog might make this easier to analyze as I have access to programs for simulating electrical circuits, but I can't find a definite analog for thermal diffusivity.
 
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solve the 1D heat equation subject to your specific boundary conditions. The thermal diffusivity is the factor in front of del^2 T
 

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