Sizing a Chiller Storage Tank/Pump Skid

Hey all.

I need some help. Right now, I have spec'd out a chiller I need for my application. The application is a blow molding dept consisting of 9 blow molding machines. We'll require a 100 ton chiller to accomodate the machinery, give/take because not all run all the time.

How do I go about sizing the storage tank/pump skid? Right now, I have about a 225' stretch of 2" pipe going down the wall of the plant, and then returning to the chiller. There are drops going to each machine on this stretch of piping.

By the looks of it, I have to have a minimum of 267 gpm of flow to all machines if I want to run everything. Pressure needs to be 60 psi min, but I'd like upwards of 80 psi. I'm not sure either what size piping would work for 267 gpm, but am leaning towards 6" to be safe.

Please, any help would be greatly appreciated.

Thanks
-Tim

most plastic manufacturers here use cooling towers only. dependent on temps required. too cold and moulds start sweating and imperfections on product, so have high flow rates and dew point control.

You have to decided, what are you using the tank for.
Expansion/Contraction
To seperate the plant and chiller flows for optimum performance "split buffer tank"
Or as a thermal Buffer, this does depend upon how you control the cooling capacity of the chiller.
If we go very basic and your chiller is all On then all Off, and the chiller moter has a rating of 6 starts max per hour, then the size of your tank need to equal 10 mins worth of plant cooling capacity, this can be in the form of a large voulme and small temp split, or reduced volume and increased temp split. If your chiller has load control (and it should at that size), you can reduce the tank size, by how much depends upon the diversity of the plant (If you have one platic plant going do you sundenly turn on the rest or are they staged)

you need at least 4 litres of water per kW of cooling capacity. more would be better for stable operation of the chiller. The chiller should have a turndown (capacity control) to at least 25%. slide valve control down to 10% would be better.

For the application you are looking at, generally you want to use a split tank with a baffle and two pumps. One pump for the system and one for the chiller flow. Size the tank for at least 5 times the pumping rate fro the system users. ie. if you are pumping 300 GPM, size the tank for a minimum of 1500 gallons.

There are cheaper ways to do this, but this will provide the smoothest operation.

Ken

Ken is correct. A two loop operation works best process. Make sure the chiller pump flows 10 -20% more than the max flow on the system pump and that the internal baffle or cross over on the tanks is at 50 to 65% of the height. The two flows between the chiller and the process loop will never match; therefore with the chiller pump flowing more the tank always spills over coldside to "hot" side. This allows greater consistincy in control and tem to the process. Most times on the process side I use a drive on the pump and control it on pressure. That way I get consistent flow to each invidual piece of equipment regardless of the number of pieces on line. In addition chillers like constant flow; so the chiller pump alway pumps the same volume through the chiller.


James