Heat flow in low pressure, knudsen number

AI Thread Summary
Heat transfer in low-pressure environments involves complex interactions between conduction, convection, and radiation. In a vacuum chamber where the object's size is smaller than the mean free path of air, traditional methods of calculating heat transfer may not apply effectively. The discussion highlights that while heat radiation can be easily quantified, the conduction and convection to surrounding air are significantly reduced. The challenge arises from the fact that the air is too sparse for viscous flow and too dense for molecular flow, complicating the heat transfer analysis. Understanding these dynamics is crucial for accurate thermal management in vacuum systems.
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Hi! Been lurking around here for a while but joined today :)

My question is about heat transfer in low pressures. I have an object in a vacuum chamber that is much smaller than the mean free path of the air in the chamber. However, the general dimensions of the chamber are much larger than the air mean free path. Heat radiation from the object is easy to calculate but how about conduction/convection to the surrounding air? I'm pretty sure it is low, but how low?
 
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I thought i couldn't use molecular flow because the air in the chamber is viscous, but I can't use viscous flow either because the air molecules are so likely to 'miss' the heated object.
 

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