# Modelling conductive/contact heat transfer in a vacuum

• jfoster
In summary, the engineer is thinking about how to model a system where a block with a lengthwise stroke of about 4" provides a 100W heat load against a contact interface between two heat exchangers, each made of copper. The smaller block has a lengthwise stroke of about 4", and both contact surfaces can be specified with a very high surface quality. The force which holds the two blocks together is up to the engineer. The system needs to be reliable for about 100k cycles or 10 years.
jfoster
Hello,
I have a little problem I'm thinking about for work. We are considering a design that moves heat across a contact interface between 2 heat exchangers, each made of copper, in a high vacuum environment. There will be one fixed heat exchanger, maintained at 25 C by coolant flow. This fixed heat exchanger is about 2" x 6" x 1/2" thick. Against this slides a 2" x 2" x 1/2" thick block, which provides a 100W heat load. The smaller block has a lengthwise stroke of about 4". Both contact surfaces can be specified with a very high surface quality, and will be lubed with vacuum grease. The force which holds the two blocks together is up to me. The system needs to be reliable for about 100k cycles or 10 years.

I am just a lowly mechanical engineer, trying to model this system to figure out something about performance. I use COSMOS/works fairly well, but I have no idea how to model this interface with any kind of accuracy. I know that without the grease, no matter how well the surfaces are finished there will be only a few points of contact. In vacuum, there will be no convective heat transfer, so transfer is up to the grease. The problem is, I don't know what the grease will be like in 10 years or if it will have all been scraped off.

I have considered modelling this system in COSMOS/works by putting a thin layer of material (2 thou, or so) between the two blocks which has a thermal conductivity which is less than the published thermal conductivity of the vac grease by a factor of say, 2 - 5, and see what happens... Any better ideas?

MS Paint pic below

I am just wondering if some sort of grooved surfaces would hold the grease in longer than completely flat surfaces - something like diamond striations on each part.

## What is conductive heat transfer?

Conductive heat transfer is the transfer of heat between two objects that are in direct physical contact with each other. Heat is transferred from the hotter object to the cooler object until both objects reach the same temperature.

## What is contact heat transfer?

Contact heat transfer is a form of conductive heat transfer that occurs when two objects are touching each other. The heat energy is transferred from the hotter object to the cooler object through direct contact.

## How is conductive/contact heat transfer different in a vacuum?

In a vacuum, there is no medium for heat transfer such as air or water. This means that conductive/contact heat transfer cannot occur through direct contact between objects. Instead, heat is transferred through radiation, where energy is emitted as electromagnetic waves.

## What is the importance of modelling conductive/contact heat transfer in a vacuum?

Modelling conductive/contact heat transfer in a vacuum allows us to better understand and predict the behavior of objects in space and other environments where a vacuum may be present. It is also crucial for designing and testing equipment that will be used in these environments.

## What are the key factors to consider when modelling conductive/contact heat transfer in a vacuum?

The key factors to consider when modelling conductive/contact heat transfer in a vacuum include the temperature and material properties of the objects involved, the distance between the objects, and the presence of any external heat sources. It is also important to consider the effects of radiation and the geometry of the objects being studied.

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