Grease + Graphite

[aojorda]

I'm trying to make about a 50/50 grease and graphite mixture to make a thermally conductive heat transfer mastic. Basically this compound will fill the air gaps between a carbon steel process pipe and a bolted on heating pipe to transfer the energy. We've tried several greases and oils and we run into the same problems;
1. it gets so thick you cant spread it
2. the thermal properties are too low
3. oil additives come out of solution
4. adhesion to the pipe is too low.

The material should be able to withstand up to 400F, have the consistancy close to penut butter, withstand outside conditions, and good thermal conductivity.

Any suggestions on new greases to try will be helpful. We've also looked into silicone greases used for computers etc and they are too expensive or they drip out.

Thanks

 

[jstutz]

Welcome to the forum! There are some pretty sharp guys on here that hopefully can help you out. Unfortionally, i am not one of them but you have a fairly interesting request and im interested in seeing the answer. Why must it be thermally conductive?

 

[SuperDave456]

Let me get this straight.

You are building a heat sink, or some type of radiator, and attaching it to the closed off coolant loop with grease?

If I understand this correctly Im not sure there is something on the market for you.

Although there are many engineering solutions, I don't see a modified grease being one of them.

 

[roadrunner1]

Originally Posted By: aojorda
I'm trying to make about a 50/50 grease and graphite mixture to make a thermally conductive heat transfer mastic. Basically this compound will fill the air gaps between a carbon steel process pipe and a bolted on heating pipe to transfer the energy. We've tried several greases and oils and we run into the same problems;
1. it gets so thick you cant spread it
2. the thermal properties are too low
3. oil additives come out of solution
4. adhesion to the pipe is too low.

The material should be able to withstand up to 400F, have the consistancy close to penut butter, withstand outside conditions, and good thermal conductivity.

Any suggestions on new greases to try will be helpful. We've also looked into silicone greases used for computers etc and they are too expensive or they drip out.

Thanks


read your post and i'm sure there are several alternatives, but i have in front of me a john deere spec sheet on oils, grease, and coolant.
deere offers a "multi-purpose extreme-duty synthetic" that looks to fit your requests
high-temp, extreme-pressure grease (-45` to 450` f)
multi-purpose; recommended for most applications
non-toxic,odorless, food grade
synthetic base oil

don't know if this will work for what you are looking for or not, but it fit into your temp specs

 

[m37charlie]

What about mercury?

Charlie

 

[Kaboomba]

You might find more useful information on Engineer's Edge and Eng-Tips, but I'll clock in anyhow:

1. What is your desired heat transfer rate? (W/m^2, or in terms of dT/kg process or similar)
2. What are the temp extremes?
3. Can your "heating element" supply enough energy?

Final notes:

Grease is a relatively poor heat conductor, graphite is not much better. You would be uber-better-off building a plastic tank around the whole juction and filling it with water/propylene glycol! ANother cheapo solution would be to heat up and glop the whole junction with lead solder.

Depending on your desired rate of heat transfer and desired process flow rates, you may need to spring for a genuine heat exchanger.

 

[jstutz]

Keep in mind i really dont know anything about this, but why not a material like copper based high temp neversieze? It covers the high temp by a great margin, it lubricates the joint and is conductive.

 

[bonnie john]

food grade silicon grease ?

 

[roadrunner1]

Originally Posted By: bonnie john
food grade silicon grease ?


i didn't make it, i just read then typed what it said, i have never had any reason to use that particular product, so i have no first hand knowledge

 

[mechtech2]

HOw about an epoxy?
When/if you need to take things apart, use a torch to break it down.

 

[MolaKule]

jstutz's suggestion makes sense.

You might want to try this as well.

Get some Bar and Chain oil that is really tacky and mix it with Engine Restorer. ER has copper, lead, and steel gunk, the B&C oil will help it stick.

 

[dwendt44]

Wasn't dielectric grease (silicon) used for heat sink a few years ago?
I recall changing the module in a GM distributor and using that grease for the heat sink area.

 

[mechtech2]

Dielectric grease is not a good heat sink medium.
People use it because they recognize the name.

 

[deoxy4]

Maybe this would work.

http://www.permatex.com/documents/tds/Automotive/24125.pdf

 

[bruce381]

high moly/graphite aniti sieze as in for bolts and threaded fasteners