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Quote:
Originally Posted by DetroitAC
When liquids are chilled to very low temps, the liquid becomes thick and velocity is decreased. The use of high pressure increases the linear velocity. In theory....the process should be the liquid will maintain low temps without decreased velocity. :rolleyes:
Hope this explains,;)
Going to be fun trying to figure out the balance between heat dump from the pump (due to the amount of work it must do) vs advantage of speed of flow.
Any particular liquid you had in mind?
Amaxing Work
I have a back up plan if the heat dump from the pump is more than expected or the compressor can't handle the load. I will add a in line coil heat exchanger and 1/4 hp compressor to help with the cooling. :D The liquid I will be using is DowFrost Heat Transfer Fluid.... good for temps to -51C....its used in cooling industrial machinery.Quote:
Originally Posted by jinu117
Thanks for the comment. :)
Wow, viscousity of thing is damned huge....
Have you looked at others that might not have as good thermal transfer rate but have less viscousity?
I've looked at a few heat transfer fluids...but they are very expensive and I have two gallons of DowFrost just sitting around....so, I though maybe giving it a try to see how it does. What would you suggest for a good heat transfer fluid with less viscosity?Quote:
Originally Posted by jinu117
Been trying to think of a polite way to respond...thanks for the lecture on fluid mechanics ;) ...umm...I'm a mechanical engineer with 10yrs experience, I'm that guy that blew the curve in engineering fluid mechanics. Can't think of any more polite way to put it than that. It's really hard to tell who you're talking to, perhaps why Mytekcontrols has his resume in his sig? Probably cuts down on the misunderstandings?Quote:
Originally Posted by Sweeper
I usually try to give someone the benefit of the doubt, and not just haul off lecturing them, sometimes it comes across like I don't know anything, because I ask questions, really I'm just trying to be polite. Like I said, you never know who you're talking to, you could have a PhD in refrigeration and 30yrs experience in low temp liquid cooling for all I know!
OK, that having been said...your pump is a vane type carbonator pump, and that means a very flat pump curve. It will force almost it's rated flow at any head pressure, and the discharge pressure will rise to what is dictated by the resistance curve of your system. Unless you've done some upfront calculations to estimate what your resistance curve will be (correct me if you have), I don't think you could estimate what the pump discharge pressure will be. Plugging in a pump that is rated for high pressure, does mean high pressure will exist, the intersection of the pump curve and the system curve determines what pressure will exist. (you can now impress me by posting these curves)
Carbonator pumps sometimes require a positive pressure at the pump suction port to keep from cavitating. If you have such a pump, unless you are externally pressurizing the system or using an expansion tank and a closed system, you will cavitate the pump.
This is offtopic but as DetroitAc seems to be the pump man ill ask here.
I tried to pump dryice cooled methanole with grundfos ups 25-40 but when methanole got cool enough, (like under -50c or something, dont know exactly) the flowrate got down to zero. I assume this happened due cavitation. I heard some speculation that there is water in methanole which causes this but i dont understand the effect.
In school we have been teached that cavitation possibility happens in high temperatures. Closer the boiling point in current pressure, higher the cavitation possibility (which seems very reasonable).
Any ideas?
http://www.ecopumpen.de/pd-2124594576.htm?categoryId=4
Let's try to keep this short so we don't hijack Sweeper's thread, as it's pretty much his build log.
If your pump was cavitating you would hear the motor speed increase (since it's load is reduced, and it usually gets louder. I don't have any references that list the boiling point of methanol/water solutions as a function of pressure, but you can probably find them by googling. Cavitation is very easy to happen with highly viscous fluids if you have too much pumping capacity compared to suction hose area and suction hose pressure head. You are correct that being close to the boiling point also makes it easy to happen. Other than these very broad statements, I don't know how to help other than say Yes, maybe it was cavitation. :shrug:
Quote:
Originally Posted by DetroitAC
First of all, thanks for being polite with your comments. I'm definitely not a expert in fluid mechanics... but, I have research many sources to find most commercial chillers use Vane type pumps for circulation. Its impossible to determine the resistance curve and fluid pressure without the proper diagnostic equipment. I can only experiment with different pumps and monitoring devices to find which is best for circulating the low temp fluid. I hope to accomplish a high pressure system.... but, the main goal is to circulate the fluid and maintain low temps.
If I start having problems with the system....atleast I know you can possibly give me a few pointers. ;)
Gotta love it when advices are given politely and taken politely... :) I am seriously looking forward to where this is going :)
Kudos to both of you guys :) :up:
truly extreme - i can't wait to see the results
Well, I've completed one compressor and currently working on the other. I've decided to not hook up the compressor to the plate heat exchanger, until the second compressor is installed in the case. As you can see in the pics....I may have to rearrange a few components to make sure everything will fit in the case and I have access to complete both system.
Insulating the lines will be a nightmare!:eek:
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Very nicely built condensing unit there :)
Everything is very nicely built.
:up: to your planning and execution.
Nice build :up:
But why a desuperheatercoil? Or is it something else?
Thats is a DSHC, adds a bit more cooling range but also take the viberations out from the compresser.
Very very neatly done, im mega impressed dude
I know what is it ;) . I asked why he uses it. I don't think it is needed with the condensors he is using, and I think it is ugly (but that's just personal)Quote:
Originally Posted by Pete
You use it for antivibration too. Maybe thats why?
Great looking unit there mate, if everything is as clean as it's been so far you'll be up there next to Cold_ice and Bazx in my top cleanest builders :D
It was added for more cooling and vibration. I know a couple of loops would be plenty for vibration and I'm sure the condenser will do just fine....but I got on a roll and ended up with more than a couple loops. :D As far as the appearance....I like the way it looks. :rolleyes: I guess everyone has there own preference when it comes building custom systems.:shrug:Quote:
Originally Posted by bassie
Your right, it is just a thing i would have done different. Personal matter.Quote:
Originally Posted by Sweeper
Succes with your build :)
This thread is great. The project is great!
The less you have on length there better it is... but since it will be chiller.... probably won't matter too much :)
I'm curious to know why less tubing between the compressor and condenser is better. Correct me if I'm wrong...but I thought better cooling for the hot gas during cycle would result in lower temps.Quote:
Originally Posted by jinu117
More refrigerant so higher pressures i think.Quote:
Originally Posted by Sweeper