Cooling mixing tanks with a chiller, selecting chiller size

[HollyBoni]

At our company we make various cosmetics products like creams, gels, ointments. We use jacketed mixing machines to mix these products. Usually the products have a water and oil phase. We put the water phase in the mixing machine, heat up the water in the jacket with the built in heating elements, which heats the product inside the tank. We heat the oil phase seperately. When everything is up to temp, we mix the two phases, and we cool the product to around 25-30C.
So far we used tap water to cool these machines, but this is a huge waste, and our tap water is very hard, which ruins everything.
I'm looking for a chiller to cool the jacket of these mixing machines. I contacted a few different companies, but my issue is that a lot of them usually work in HVAC and don't seem to understand what we're doing. I've had companies recommending chillers anywhere from 15 to 150kw.

To give you some numbers, we have a 150l mixing machine for example. We usually mix 120-130l of product in it. The volume of the jacket is 40-50l. I built a cooling/heating system for this machine that could be used with a chiller in the future. It has a circulation pump on the jacket side, plate heat exchanger, PID controller which controls the heating elements, and controls a motorized ball valve which lets tap water flow through the other side of the HX.
We usually heat the jacket water and product inside the tank to 75-80c, then we cool the product to around 25-30c. Currently if the jacket and product temp is at 75-80c and I set 20c (temp of the jacket water) on the PID to turn on cooling, the jacket water reaches 20c in around 13-15 minutes. Tap water is usually 13C and flow is 10-15lpm.
After the jacket water cooled down to 20c, the PID lets it get up to 22c, then turns on cooling again. This happens every few minutes (like 5) as the product cools down. I measured last week, and cooling 120kg of product inside the mixing machine from 75C to 28C took around 40 minutes from the moment I turned on cooling on the PID controller.

I contacted Trane, their representative came to our factory and they gave me an Excel calculator made for mixing vessels. You put in some numbers like mass off product, mass of vessel, start temp, desired product temp etc. then it gives you a "duty kW" in kW/hr at the end.

My problem is with cool down period. If I set 15 minutes (this is how long it takes for the jacket water to cool down from 75c to 20c, which is fine, i'd like to keep that) I get 14kw. But the 120kg of cream can't physically cool down in 15 minutes, due to the slower heat transfer between the jacket and the cream. If I set 40 minutes for cool down time, I get 5kw.

So i'm a bit lost on how to size the chiller for this application. It needs to be able to handle multiple machines. We have this 150l machine, there is a 75l machine on the way, and we're also planning another machine, but the size of that is not known yet.

I'm wondering if any of you has experience with this who could help me in sizing a chiller?

 

[LittleInch]

Or maybe the water flow can be reduced if you air cool a lot down to 40 odd C?

 

[HollyBoni]

I'm with Ed here and I think you need to consider all the implications of a chiller.

Normally you don't go round installing large complex, energy hungry bits of equipment like a chiller unless you really need to.

That is usually when you need to cool below ambient air temp plus 7C, which is about as low as you can practically go.

In you case at least half the reject heat is able to be cooled this way (air HX) and probably more as the DT is higher between your substances in the Vat and the jacket water.
Then to finish it off, but only during the summer, you might need a chiller, but this can be a lot lower power than if you're trying to cool the whole lot.
During the winter you don't need a chiller at all.

You could just try this using a car or truck radiator and a 12V fan motor. Car radiators are good for 90C and will emit at least 15kW when air is blown through.

Your current system looks very stop start? and not modulated. If you want to get fancy you can introduce control valves and regulate water flow to the radiator using a temperature control PID.

I think symbolically this is what you have and would like in dashed.

If you can get the data of temperatures over time it will let us all do some numbers and see what chiller capacity you need.

I'll definitely need at least 20C coolant, but a bit lower than that would be better. My problem is that our summers are getting hotter and hotter, and the temps are creeping up in the fall and spring as well. Today it was ~36C, but sometimes we have even higher temperatures. I know that impacts the chiller as well of course.

I haven't ruled out a hybrid chiller + dry cooler approach. But of course that means a more complicated system with more components.
We're currently fixing up an indoor area where we'll have a few machines like an air compressor, RO water system, CIP system. There is no heating here currently. If I put a smaller air cooled chiller here, it would heat up the room pretty nicely during the cooler months. Of course, we will need proper ventilation in the summer.

When it comes to power consumption, the ~12-13kw chiller i'm looking at consumes 5.9kw max according to the specifications. That doesn't sound like much, and the machine itself isn't even that expensive all things considered.

Currently we only have one mixing machine with automated heating/cooling control. On this machine I chose a PID controller with one 4-20mA output, and one relay output. The 4-20mA output controls the heating elements between 0-400V. The relay output turns on and off a motorized ball valve.
So it's half on/off, but works great. Of course I can change this setup in the future.

I'll try to record a full cooldown as soon as I can.