Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
Trending News
Low-temp heat exchanger fluid?
We have a portable closet-sized temperature chamber that I want to use to cool an external mass to -40C, which will be used to provide cooling to a larger chamber. I envision a heat exchanger external to the larger chamber that I clamp the smaller chamber to, with lines running from it to the mass inside of the larger camber. A separate set of lines and fan would be used to transfer cold from the mass (perhaps an insulated box of several tons of sand?) to the large chamber.
My question is, what might be some choices for the fluid and pump used in the heat exchanger? I don't expect air will give sufficient performance? Again, the operating temperature will be -40C. Experienced refrigeration answerers only, please. Thanks.
Thank you , OFT, and to clarify, the sand is to be the thermal mass, which will have coolant plumbed through it. The sand will be in an insulated box, which would have a second set of heat exchanger plumbing to cool the testing chamber.
The idea is to give the small temp chamber whatever time it needs to cool the sand mass, a week, whatever. Once done, we should be able to cool the large chamber quickly to a min of -20C once we actually start running tests, and hopefully be able to go back and forth several cycles from -20 to +40 or 60 and back with the test unit in the large chamber before the mass gets too warm to continue. Obviously we want a $100,000 environmental chamber on a $10,000 budget.
So, since I can't email you, I'm hoping you can repost or email me with suggestions such as source for low-temp pumps and fans and an idea of what I could expect it air was only fluid - like I said, we don't care much if it takes a week to get the mass cooled prior to actual usage.
2 Answers
- oil field trashLv 71 decade agoFavorite Answer
If you are using a closed circulation system then you need a fluid like an alcohol or a water/antifreeze mixture that will still be liquid at that temperature. There are also some hydraulic fluids (used in aircraft) that should also meet the -40 degree requirement.
I would think a simple centrifugal pump would be fine to circulate the fluid. I have used them to circulate several -40 deg fluids at different times.
To comments, at -40 degrees your metals can be subject to brittle fracture unless they are properly selected. Normal steel, cast iron or cast steel are not used at these cold temperatures unless the stress levels are kept very very low. There are some specific carbon steels that can be used for these applications (see ASME and ASTM codes). Stainless steel will work to temperatures much below -50
To insulate the box, I would think you would use perlite, foamglass or maybe even fiberglass as insulating materials. I'm not sure sand will be a very practical choice.
Source(s): 35 years of experience of refrigerating natural gas and other fluids to -50 degree and colder.
