Building your own glycol chiller

I am exploring the option to build my own chiller. I would like to use a brazed plate heat exchanger, with a liquid glycol/water side, and a refrigerant side. Does anyone know what direction the refrigerant fluid flows in the evaporator? In from the top, out from the bottom (with gravity), or the opposite (against gravity)?

The general design is going to feature a condensing unit, centrifugal pump for glycol, brazed plate exchanger for the evaporator. The unit would be medium to high temp.

It seems like this can be done for $5,000 for a 5hp chiller


I’d go to a PC overclocking forum like xtremesystems and look at phase chilled liquid setups if I were you

@hashmandu this was the surna I used to cool two 6 light flips. Ran great for almost 3 years. Maybe you can reverse engineer. As you see it started to freeze itself to death. Opted for a real one soon after.


perhaps a evaporator back pressure regulator to put a lower limit on evaporator temperature, as well as plenty of insulation.

@SidViscous probably has helpful pointers to share.

Typically the output of your chiller goes into the lower end of the heat exchanger, and the top of the heat exchanger returns to the chiller. Although I’m willing to bet it’s not standard across everything…


Yeah so it doesn’t really matter which side enters on the low end, as long as they are counterflow. I’d recommend the refrigerant side leaving from the bottom to assist oil return but that’s pretty minor.

Only thing I will say is that NPT joints don’t belong anywhere in a refrigerant system, so I’d recommend having a different style welded on. You’ll have nothing but heartache if you just use a threaded adapter

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Thanks for your reply. You were wise to discern it was the oil flow which concerned me. I continued my research, and the final word on what determined the evaporator design was a function of refrigerant velocity, refrigerant temperature, and cross sectional vector area. In a medium to high temp system, the heat exchanger plates are close enough together for the shear of the refrigerant to carry the oil against gravity.

Yeah for low temp and VLT applications, I’ve found oil separators and return lines on the compressor discharge is a good investment. Between low vapor densities and low temperatures, oil return can get dicey.