Thermal transfer estimation (to simulate a game)

  • #1

Main Question or Discussion Point

I am trying to get a formula to estimate the heat lose in an airship.

Is a mod for KSP, things that have into account: pressure, wind speed, temperature, air viscosity, thermal capacity of the atmosphere, gravity, etc.

There are things that can be ignored as shape (or just use constant aproximations) wind direction, etc.

I was reading a lot, but I am not sure how to combine all heat transfer equations.

Theory: if I have an airship with higher temperature inside.
How the heat trasnfer works?

We have a heat transfer between the interior gas with the exterior envelope, (here the gas may be hydrogen and there is not external wind speeds).
Or maybe this step can be ignore?

Second step, heat transfer through the envelope (conduction), this step can be ignored too?

Third step heat transfer due convection and radiation from the envelope.
Here I have some doubts, I need to add these 2? In case heat transfer by convection is higher, then the surface will be cold, so heat transfer due radiation should be lower?
This taking into account that heat transfer from the gas inside is not so good as the outside.

What happens if the envelopes has a good insulator?
then the heat transfer is just the value which can cross the insulator and I ignore the exterior effects?

I wanna be sure of this before show any equation. Thanks.
 

Answers and Replies

  • #2
Bystander
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Second step, heat transfer through the envelope (conduction), this step can be ignored too?
You're talking a thin enough envelope for most lighter than air craft that, "Yes," you can ignore it.
Third step heat transfer due convection and radiation from the envelope.
Here I have some doubts, I need to add these 2? In case heat transfer by convection is higher, then the surface will be cold, so heat transfer due radiation should be lower?
This taking into account that heat transfer from the gas inside is not so good as the outside.
The thermal conductivity of hydrogen (and helium) is higher than that of any gases in which a hydrogen filled ship will be buoyant.

then the heat transfer is just the value which can cross the insulator
Yes.
 

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