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IslaRefri
28-08-2017, 04:09 PM
Hello all,

I was just at a very small dairy plant (1500-3000 ltr/day) and they are not able to meet their cooling demands. Currently they have two 1900 ltr tanks, which I believe in the past held a glycol solution. Now there is only water. In the tanks there is a helical bare pipe 5/8 copper evaporator that basically creates ice during the night but only a small amount since its one row around the outside of the tanks all the way to the bottom. Im guessing there are about 14 - 20 passes (hard to tell since the tank was full of water). The ice get fairly thick, about 4 - 5 inches or so which I think is to thick. Im estimating the tank in the morning would be around 10-20%ice and the rest chilled water. They do not want to pump glycol around the plant, only chilled water. The evaporator is a 1 pass. The owners are small co-op of farmers and want to use what they already have and cannot invest in a new ice bank or some other system.

My question is, would it be possible to throw some more evap circuits in the existing tank, maybe about 4" of spacing between the pipes to create 1.4" ice in helical spirals from the top of the tank to the bottom? There would be a larger loop on the outside and subsequently smaller loops the further you got to the middle. The goal would be to try to create about 65% ice in the tank or tanks. I was thinking around 4-5 evap circuits fed by one TXV and a distributer. I cant seem to figure out how to properly balance each circuit. The middle smaller one would freeze first and then that would end up limiting the TXV for the rest of the circuits.

The condensing units they are using are two FH4524F HR R22 Tecumseh. Ive done some rough calculations and the condensing units may not be enough to create all the ice over night. So I could get a larger condensing unit and use it on one of the tanks and use two of the old ones on the other tank. Just some ideas.

The total daily load for the plant and full future production will be around 1 MBtu/ 293kwh

Im in a very remote region with very limited access to things, yes things. I do not have much experience in this sort of thing, just want to help these guys out if I can. Any ideas, concerns or objections would be most appreciated. Thank you!!

monkey spanners
29-08-2017, 09:30 PM
Rule of thumb for ice bank milk cooling is around 2.6KW @ -5C evap duty condensing unit per 900L of milk from 36C to 3.5C with a run time around 16 hours. In old money its a 1hp R12 Copeland unit on a 200 gallon milk tank. The cooling duty comes from the melting of the ice not so much the low temperature of the water so not sure glycol will help unless the system really is designed to work that way.

How do they use the chilled water at the dairy? Can you give a brief description of their set up?

hookster
30-08-2017, 06:50 AM
The ice is a thermal store to reduce the capacity of the refrigeration system required to provide the cooling duty. For the system to be effective there needs to be a recovery period for the ice bank to build ice (thermal store) this energy is then released during the peak demand.

I would assume if the refrigerating plant is running effectively then, then your client refrigerating demand has risen above initial design demand and additional cooling is required.

An option would be to install a plate heat exchanger with its own refrigeration plant and circulate the water from the ice bank through it. The design would be to reduce the delta T of the water and go into bypass before freezing. This will then accelerate the recovery time for the ice bank as it has a lower delta T to work through.

HVACRsaurus
30-08-2017, 11:30 AM
Hi Man,

Maybe the esteemed Monkey Spanners could respond - Is anyone using an Air pre cooler?

If milk comes out of a cow at 36 Celsius, could the milk be lowered to 20 odd Celsius with an ambient air cooled circuit prior to entering the chilled tank?

monkey spanners
30-08-2017, 04:52 PM
I've not seen air cooling but often they will have a two stage plate heat exchanger with mains water through one side and chilled water through the second side. The warmed mains water is fed to troughs for the cows to drink and also to a storage tank for washing down the parlour after milking, its basically free cooling as its water that would be used anyway.

IslaRefri
30-08-2017, 05:46 PM
Hey guys thanks for the replies. Sorry I was out in the boonies for day or so with no reception or internet.

To answer your question monkey spanners; it looks like the set up they have now, they had glycol in the two 1900 liter tanks and used that to chill everything. Their milk production was a lot less before but now they are ramping things up a little bit. Hoping to do 3000 liters/day in the future. At the moment there is only water in the tanks and the coils do get a fair bit of ice formed on them during the night but there is only one helical spiral going from top to bottom. Basically there is still well over 80% of the water in the tanks not being used to make ice. Question is, has anyone ever converted 2 cylindrical tanks to make ice instead of chill glycol? I have many ideas in my head on how to make this evaporator but keeping running into problems with, balanced circuits, oil return, spacing of pipes, yada yada. Im in very remote region and it can be very difficult to order things in, especially big things.

They do not want to use glycol in the tanks any more also, they just want to pump cold water to where they hold the milk and some of there pasteurizers. If they could get 65% ice in both of their tanks over night that should be more than enough for there needs.


Rule of thumb for ice bank milk cooling is around 2.6KW @ -5C evap duty condensing unit per 900L of milk from 36C to 3.5C with a run time around 16 hours. In old money its a 1hp R12 Copeland unit on a 200 gallon milk tank. The cooling duty comes from the melting of the ice not so much the low temperature of the water so not sure glycol will help unless the system really is designed to work that way.

How do they use the chilled water at the dairy? Can you give a brief description of their set up?

chemi-cool
30-08-2017, 05:46 PM
I have built for dairy farm a supply water\milk heat exchanger.
It cools the milk free of any energy input by 15C before it enters the tank.

We don't use in our part of the world ice banks, only DX cooling tanks.