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SCENARIO:

I have been tasked with finding the heat transfer across a composite wall on Mars.

On the left of the wall there is air maintained at Earth atmospheric conditions and room temperature (101 KPa, $21^\circ C$). On the right there is Martian air, residing at approximately 1 Kpa and $0^\circ C$ perhaps with a light breeze of 4 m/s.

The diving wall is made up of an internal sheet of aluminium, 5cm thick, and a slab of Martian soil 50cm thick.

QUESTION:

From left to right, heat enters the wall through convection + radiation, travels through the wall via conduction, and leaves the wall through conduction and radiation. I believe if I can compute R values for each of these, I can combine them in parallel and series to find an overall R coefficient in order to find the power required to maintain the temperature at 21 C.

My struggle is to find the correct R values for convection and radiation, most importantly because I do not know how to find the convective heat transfer coefficients. I have looked through literature but not found anything useful. Any advice?

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    $\begingroup$ How are you going to calculate the R value of the Martian soil? What terrestrial analog are you going to use? $\endgroup$ – Rick Mar 15 at 16:01
  • $\begingroup$ At such low temperatures you can neglect radiative losses. $\endgroup$ – Gert Mar 15 at 16:58
  • $\begingroup$ This should be of interest: fc.civil.tamu.edu/resources/en/engr214/chapter7/node13.html $\endgroup$ – Gert Mar 15 at 17:03
  • $\begingroup$ @Rick Various sources are available which estimate the thermal conductivity of Martian soil (this is one example researchgate.net/publication/…) which estimates a k value of 0.144 W/mk, leading to an R value of R = t/k = 0.5/0.144 $\endgroup$ – D Young Mar 15 at 17:27
  • $\begingroup$ @Gert thanks for the link that is very useful. If I was to include radiation would I simply add it in as one of the boundary conditions mentioned in that paper? i.e. instead of conduction = convection, we have conduction = convection + radiation. Some sources I have read have stated that radiation on Mars would be quite significant compared to convection due to the atmosphere and low temp compared to the temp of the wall $\endgroup$ – D Young Mar 15 at 17:30

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