Thermal Diffusivity in practice

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In summary, the conversation discusses the estimation of heat flow between two gasses separated by a wall, with one gas changing temperature due to an outside agent. The speaker mentions the importance of thermal diffusivity and their struggle in applying the given numbers for it to their situation. They also mention the need to account for diffusion through the thickness of the wall and their consideration of using an electrical analog to analyze the situation. Ultimately, the conversation suggests solving the 1D heat equation with specific boundary conditions, with the thermal diffusivity being a factor in front of the del^2 T term.
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mynode
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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
 

1. What is thermal diffusivity and why is it important in practice?

Thermal diffusivity is a measure of how quickly heat can pass through a material. It is important in practice because it helps us understand how materials will respond to changes in temperature and how quickly they can transfer heat. This is important in fields such as engineering, materials science, and thermodynamics.

2. How is thermal diffusivity measured in practice?

In practice, thermal diffusivity is typically measured using a technique called the laser flash method. This involves heating a small sample of the material with a short pulse of light and then measuring the temperature change over time. From this data, the thermal diffusivity can be calculated.

3. How does thermal diffusivity vary between different materials?

The thermal diffusivity of a material depends on its thermal conductivity, density, and specific heat capacity. Generally, materials with higher thermal conductivity and lower density have higher thermal diffusivity. Metals and ceramics tend to have higher thermal diffusivity than polymers and insulators.

4. How can thermal diffusivity be used in practical applications?

Thermal diffusivity has many practical applications, such as in the design of building materials, thermal insulation, and electronic devices. It can also be used in industrial processes, such as in the production of metals and the cooling of molten materials.

5. What are some common challenges in measuring thermal diffusivity in practice?

One of the main challenges in measuring thermal diffusivity is ensuring that the sample is homogeneous and free from defects or impurities. Another challenge is accurately controlling the temperature and heat flow during the measurement. Additionally, different measurement techniques may have different sources of error, so it is important to carefully consider the method used for each specific application.

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