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Need help with a phase changing system - Page 2

post #11 of 16
Thread Starter 
Hmm well then it's down to making that entire thing by almost pure trial and error on what would work? The case that it's in cools everything fine and I dont have the money, or space in this dorm, to make 2 phase changers and house them. Especially since its a military college. Or am i just SoL on making a dual evap system?
post #12 of 16
I've been making phase units for 7 years. I've done maybe ~10 dual evaporators. And balance can take weeks of tuning. I never do them for sale, because they vary they're "balance" based on loads. It's not the right way to get phase on multiple things. Better off learning, then you can cut it up and try again with more evaps if you want.

The only way I do dual evaporators, and any of the major manufactures (Cooler express) do dual evap, is oversizing all the components, and effectively just flooding all the evaporators. And they still have to worry about floodback and low load issues.

You could experiment with serial evaporators though, fed by one metering device.
post #13 of 16
Thread Starter 
When i make it ill probably follow one the guides that you have written. Absolutely genius and where i was basing most of my knowledge of phase changers mechanics on.
post #14 of 16
If you have specific questions ask, most of the guides don't feel very up to date.
post #15 of 16
Yeah, couldn't you just run the two evaporators in series and use a suction accumulator? What about an external equalized TXV with the evaps in series? You could also use a high concentration calcium chloride brine solution as a secondary refrigerant with a single evaporator, as the eutectic point at 30% mixture is ~ -50 deg C, but the pump requirements will be high since the viscosity is significantly higher than water. Not to mention it may corrode things. A 60% mixture of ethylene glycol will also give you freeze protection down to -55 deg C and you can get that at walmart in the car section. Depends on how cold you want to get, but I'd imagine going below that in evaporating temp would require more exotic equipment and refrigerants, and you have the temperature difference between the actual boiling liquid and the surface of the heat exchanger in contact with the glycol as a buffer.

But I agree that you're going to end up with a mess and have no idea in h3ll what's going on with it and why it doesn't work right if you have never messed with or built any refrigeration systems before. Start with something simple so you get an idea of how it works and what affects what before adding more factors and variables. It's like trying to understand advanced mathematics without mastering algebra. wink.gif
Edited by RADEON - 9/6/12 at 1:39pm
    
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CPUMotherboardGraphicsRAM
E4300 @ 2.64 GHz ASUS P5LD2 Evga GeForce 7950GT 512MB 2 x 1 GB PQI TURBO DDR2 800 
Hard DriveOptical DriveCoolingOS
2x Seagate Momentus 7200.3 in RAID 0 Samsung lightscribe DVD burner intel stock Cu core with old 3 blade Thermaltak... Windows 7 Ultimate 64 bit 
MonitorKeyboardPowerCase
Samsung SyncMaster B2230HD Dell Dell 350W generic 
MouseMouse PadAudio
logitec The desk Creative SBLive! 
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post #16 of 16
This is why for multiple evaporators its often a smarter smooth to make a liquid chiller. Industrial applications prefer liquid chillers. And it allows you to use a valve like a thermostatic expansion valve (TXV) that helps solve many issues.

"Accumulators" though are never prescribed. Sure with a series evaporator system on captube you might have floodback. But an accumulator is a band aid on a chainsaw wound. It means you messed up to begin with, and your now in a tough spot. Almost all systems can avoid needing an accumulator. Even in a rotary compressor the accumulator is more there to regulate oil return.
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