Help with chiller expansion tank and pressure.

[miked_34]

I have a chiller with a cooling capacity of 23 kw and a pump head of 25 m. my system volume is about 60 gallons. The highest point of my system Is 102in . The set point will be around 27 degrees F, High temp ambient inside air = 90 F . 35% propylene glycol , 65% water. two cooling jackets have a max rating of 15 psi.

I need help determining if my system can run under these conditions and if so, what size expansion tank would i need ( thinking 3 gal) .

I am also worried about cavitation of the glycol if my system pressure has to be below 15 psig. I tried finding phase diagrams of propylene water mixes at various pressures but didn't have any luck. any other ideas on how i could determine this ?

attached is a diagram of my system.




Thanks for your time !

[gitchegumee]

Your system sounds fine, although I didn't see any attachment for diagram. You do not need an expansion tank with an open glycol system. You will want an air eliminator at high point(s) in your system. You will not cavitate at these temperatures unless you really, really try hard--so don't worry about that. Good luck!

[miked_34]

the pic shows up on my end. when i view on a desk top. maybe the file was too big . I attached a cropped photo to this message.

[asampaio]

HI Miked_34

I am happy to support you with the design of your glycol loop - see my contact data at the end of this post.

In the meantime here are some useful hints:

- whenever possible build your mainline above the connections to the tanks to avoid air traps and requiring a de-vent valve at each connection;
- design your loop using the first-in/last-out principle, so the path of resistance for the glycol to reach each tank is the same. This ensures all tanks will be able to perform identically. The way you have it designed will benefit the tanks closer to the chiller and the ones further apart will be struggling to get to the right temperatures;
- design a by-pass at the end of the supply towards the return so fresh glycol is always circulating and doesn't warm up for standing still;
- use a strainer on the return line before reaching the reservoir, to avoid particles depositing there.
- Install de-vent valves on the higher points of the installation - you want to get the air out easily when filling up the pipeline;
- Consider adequate pipe material to handle glycol and fluids at temperatures below freezing
- Consider the correct type and thickness of insulation to avoid condensation (and mold) as well as temperature (energy) loss along the lines.

Let me know if I can be of further support.

Cheers!

Angela Sampaio
Market Segment Manager Cooling – Food & Beverage
Mobile : +1 949 343 3713
angela.sampaio@georgfischer.com

Georg Fischer LLC
10540 NW 26th St. #G-304
Doral, FL 33172
United States

https://www.gfps.com

[miked_34]

My system is a closed system. I am wondering if i need to install an air vent on every outlet pipe that is above my return manifold. I am also not sure how I should size the pressure release valve. the highlighted valve is going to be a back pressure regulator also don't know how to size that. pipe ID is 1 in

thanks for your help

[gitchegumee]

What kind of chiller do you have that is closed? Those are not very common and will require a bit of thought. I'd MAKE it an open chiller if it were mine. Try to plan glycol piping so that there are no traps in it. Start with your glycol supply line low, rising through the fermenters, and the return line high if you can. One air vent at highest point of return before coming down into the chiller.

The way you have this drawn, your first tank has shortest distance on supply AND on return lines. This means it will perform better than the last tank which has much higher line friction. To balance pipe friction and tank back pressure, I would run return line all the way to the right end before picking up F1, then F2, F3, etc; going from right to left. In this way, each fermenter has same combined pipe friction.

I also put the strainer just after pump on chiller outlet so that a clogged strainer doesn't compromise your tank jackets: 25 meters of head at pump zero flow is more than jackets are rated.