Heat transfer - aeroheating and material thickness

In summary, the conversation is about determining the necessary thickness of a carbon fiber shroud to prevent overheating of avionics housed inside during a rocket launch. The shroud will be subjected to a maximum heat rate of 908 kW/m^2 based on aeroheating analysis, and the avionics have a maximum temperature rating of 85 C (358 K). The individual has attempted to use Fourier's law for a first-order analysis, but it is not yielding accurate results for the desired inside temperature. They are seeking advice on how to approach calculating the thickness and do not have an estimate for the heat transfer coefficient in this scenario.
  • #1
engineer23
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Heat transfer -- aeroheating and material thickness

I'm trying to size the thickness of a shroud to encapsulate a payload on a small rocket. We're using carbon fiber pre-preg (k=6.83 W/m-K) and (per the aeroheating analysis based on the trajectory) the max heat rate is 908 kW/m^2.

The avionics housed inside the shroud are rated to 85 C (358 K).

How can I get an idea of what the thickness of the shroud needs to be to prevent overheating?

I tried to use Fourier's law for SS conduction through a plane wall as a crude first-order analysis to get an idea. So the outer temp. on the shroud moldline (To) is given by q"L/k + Ti. I've been picking inside temps. (Ti) that are some percentage of the max. temp the electronics can take (say, 50% or 179K) and a material thickness (ex. 1/8") and then comparing the predicted outer temp. with the glass transition temp. for the material. This doesn't seem like a very sound analysis, as it's also predicting overheating for basically every thickness I select.

Ideally, we could estimate the outer wall temp. and then calculate the thickness based on a desired inside temp. How should I approach this? I also don't have an estimate for h (heat transfer coefficient for convection) in this scenario.

I haven't had heat transfer in many years, so I think I'm feeling in the dark to some degree!
 
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  • #2
you should always gauge using maximum temperature of outer wall to calculate the thickness.
 

1. What is heat transfer and how does it relate to aeroheating and material thickness?

Heat transfer is the process of thermal energy moving from one object to another. Aeroheating is the transfer of heat between a solid surface and a high-speed fluid flow, often encountered in aerospace applications. Material thickness plays a role in heat transfer as it affects the rate of heat transfer and the amount of heat that can be stored within the material.

2. How does aeroheating affect the performance of materials?

Aeroheating can have a significant impact on the performance of materials as it can cause thermal stress, material degradation, and even failure. The high temperatures and rapid heating and cooling cycles can weaken materials and decrease their lifespan.

3. What factors influence the rate of heat transfer in aeroheating?

The rate of heat transfer in aeroheating is influenced by several factors, including the temperature difference between the fluid and the solid surface, the material properties of the solid surface, the flow velocity, and the angle of attack.

4. How can material thickness be optimized to withstand aeroheating?

Material thickness can be optimized to withstand aeroheating by selecting materials with high thermal conductivity and high melting points, as well as increasing the thickness to allow for more heat storage. Thermal protection systems, such as insulation and heat shields, can also be used to reduce the impact of aeroheating on materials.

5. What are some common applications of aeroheating and material thickness in the aerospace industry?

Aeroheating and material thickness are crucial considerations in the design and development of aerospace vehicles, such as spacecraft, missiles, and aircraft. They are also important in the manufacturing and maintenance of these vehicles, as well as in the design of thermal protection systems for re-entry vehicles.

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