Hydraulic Oil Cooler Repurposing for Aftercooler

[MrSurly]

I picked up a hydraulic oil cooler (took it off of a salvage Bobcat trencher) that I’m going to install as an after cooler on my compressor set up. It looks perfect for the job in its size, but I’m wondering what is going on inside the silly thing. Looking inside the thing I find that there are some aluminum components installed within the tubes.
I’m curious if any of you happen to know what these are?
My first two guesses: spiral “swirl inducers” OR
(This is what has me worried a bit) thermal elements that restrict or regulate flow???






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[PaintDog1]

I’m no expert, but my guess the inner tube forces the hydraulic oil to the outside wall of the outer tube to maximize heat transfer. Without it, more oil would flow down the center of the tube, so less efficient heat transfer. Think of how a river flows, faster in the middle, and slower along the shore.


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[matt_i]

The design of the heat exchanger uses internal "fins" to purposefully cause turbulent flow within each cross-tube, in order to get max heat transfer efficiency.

If the fluid is just allowed to just run thru without restriction, just the fluid at the OD of the tube will experience max heat transfer, and the major flow stream at the centerline will experience minimal cooling.

Also: make sure that you feel certain that the cooler can take the full line pressure of the A/C system. It might have been installed on a fluid return to tank that experiences almost zero pressure (other than that developed by its internal restriction).

 

[MrSurly]

I think you're both on point; some version of flow directing device. Not needed for air but not expected to create any problem, either, would be my guess.

The cooler was definitely installed as a return-side fluid cooler at the oil tank of the machine. That said, the build of it (silver-brazed heavy copper tubing, all round-section) suggests that it can handle significant pressure. I'm confident that it could handle 500 PSI. My application won't exceed 180.

 

[pcmeiners]

This is a common heavy duty oil cool rated at 300-350 lbs. psi. Hayden, Allison, and others sell them. Your are correct, they are swirl tubes and function as Matt I explained. They will not cause significant restriction. I would not use the (reducing) tube adapters, too restrictive.

https://www.haydenindustrial.com/

 

[MrSurly]

Yeah the jic adapters are out. I’m building out the system with .75 ID copper and .84 ID stainless. There will be one “high volume” port and several standard (3/8 npt) outlets.


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[Lelandwelds]

If you plumb it between your pump and tank, I suspect it won't cause a significant flow restriction. Most pumps aren't that high volume and the tank is downstream to handle demand peaks. If you need it after your tank, add another tank down stream near your largest air hog.

I doubt you need a surge tank. I doubt that monster poses a restriction. I doubt you need an aftercooler. But then, my projects always include some ridiculous overkill.