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Chris Zahrt
08-10-2001, 10:18 PM
I am a mechanical engineering student at Purdue University. For our senior design project, we have to design a small refrigerator to cool workstation microchips. Anyway, I'm looking for how to design the capillary tube used for throttling. I've looked in the ASHREA handbook, but it only gives curves for R22 and some other refrigerant. We're using R134a. Any advice you could give would be appreciated. Thanks in advance.

Brian_UK
08-10-2001, 10:41 PM
Hi Chris and welcome.

You might like to look at the following site for information on sizing cap-tubes:-

http://cbg.cubigel.com/english/tecinf3.htm - Electrolux Compressors-

I haven't studied it in detail but appears to have some good pointers.

Also if you do a search on this site, using the button at the top, on capillary you will find some other comments on the subject.

Good luck on your project.

subzero*psia
17-10-2001, 04:55 PM
Hello Chris,

I have asked similar questions regarding captube sizing.

Here is something to consider.... you can select any diameter captube (practically) but you need to focus on pressure drop over the length of the tube. So in a nutshell what you will find is there is a basic rule of thumb but nothing carved in stone so to speak.

What works in one unit may or may not work in another unit of similar design. That is also why you will find so many manufacturers of captube systems use uncommon size tubing quite often.... if the captube is replaced in the field, the tech will usually try to use OEM parts.

I can use an .039 captube instead of an .049 if I adjust my length to correct for pressure drop. Its often experimentation that leads to a chosen size.... even at the manufacturing level. You would also have to consider any bends or loops in the captube and if you will be subcooling the liquid to help prevent premature flashing in the capillary.

Sounds like you have a tuff'n! ;)

Have you considered another possible metering device... perhaps an orifice instead? I hate to do this but my professors always quoted it to me... "your question is system dependant." Perhaps you can elaborate more regarding the load, space available etc. Sounds like you are working on something very small.... to replace the old familiar "heat sink"? That leaves you with redesigning the cabinet... it will probably be about the size of a college dorm room refrigerator by the time you get all your components in there! LOL!! :p

Shailesh Achary
04-06-2009, 07:03 PM
Hi!
I am also trying to find option of cap tube replacement while replacing compressor.

Shailesh Achary
04-06-2009, 07:07 PM
Hi!
If you get your ans. pl inform me

icecube51
04-06-2009, 09:16 PM
go to the Danffos site,they have a nice program there cald "Dancap", its free and very handy. give you a good head start.

Ice