Brazed Plate Heat Exchanger Near Freezing Point

[Leonardo Netto]

Have you ever tried to design and build a water chiller that goes very close to freezing point ?

I had the chance to supply a water chiller for a poultry slaughter house that requires 8 meter cube of water to be cooled from + 28 Deg C to +1 Deg C. [One pass cooling]

The easy part is the design & build. The difficult part is the testing and commissioning of the chiller.

The evaporator pressure regulator has to set to close at -2.2 Deg C.
The hot gas by pass valve has to be set to start injection only when the outlet water temperature goes to 0.8 Deg C.
You can go down to as low as 0.5 Deg C out let temperature without freezing the plates.
You have to have a accurate digital thermometer.
The sensor probe should be placed in the outlet flow of the plate heat exchanger as near as possible to the plate pack.
You will see the temperature go lower and reach to about 0.4 Deg C / 0.3 Deg C and then begin to go up.
This is because a layer of ice is starting to build up on the plates. The ice acts as an insulator, causing the temperature to go up. At this point the hot gas by pass must be set to start injection. The hot gas injection will wash away the thin layer of ice build up. At this point you will see the outlet temperature go down again.

When commissioning this type of water chiller, please make sure you have calibrated your pressure gauges & Digital thermometer. Pressures and temperatures should be checked carefully. Settings should be checked twice over. There is no room for mistakes.

Going down to 0.5 Deg C is the extream and the risk of a freeze up is high. For the set I had built, We set the outlet water temperature to maintain at +1 Deg C.
The water chiller is still in operation today. I commissioned the plant in 1997.

See the pipe diagram. You don't need to use an electronic evaporator pressure regulator. A mechnical one will do the job.
If "Danfoss" a PM with CVP. will be accurate enough.

Have fun & keep it cool.
Regards,
Leonardo Netto.
ACE COOL

[Josip]

Hi, Leonardo

Nice,

Similar in control (SS shell&tube for CIP) but ammonia direct heat exchanger I installed in brewery to chill young beer. It was 1985 and still working

what are you cooling with this water?

Best regards,

Josip

[US Iceman]

Hi Leonardo,

Welcome to the RE forums.

The system you are describing is similar to most of the red water chillers used for poultry. It's also the same as beer chillers as Josip said.

One question... Were you forming ice on purpose?

I would have thought the pressures would have been slightly higher to stay above the freezing point to prevent the loss of capacity.

[bruceboldy]

My old company ISOTHERM designs and builds packaged water chillers Shell only not a compressorized unit, to operate at or just above freezing. The units are guaranteed to do the job properly. The process is a spray chill design. Units can be designed for most conditions espicaly high entering temps and 32 degree f water out. with high flow rates.. R-22 or ammonia

let me know if you need info i know they will be glad to visit.

bruceboldy

[bruceboldy]

A bit more , the spray chill design allows for some flexibility in controls. The suction temp control is not as critical due to the controlling side (spray chill refrigerant )being able to immediately start or stop aleviating the dreaded freeze up of the tubes in a flooded or partially submursed chiller design, You should check it out it is the best design available.

[Josip]

Hi, US Iceman

The system you are describing is similar to most of the red water chillers used for poultry.

Do you speak about spin chillers (with water and ice)? I think that is not allowed in Europe, because you have to pay for frozen water inside of chicken the same price like for meat

Can you, please, explain this

In my Merriam-Webster's Collegiate Dictionary:
red water noun (1594)
:any of several cattle diseases characterized by hematuria

Best regards, Josip

[Peter_1]

Food may not be submerged nor sprayed with chilled water, unless it's vacuum packed.
Here, there's even a law which explains what sort of water you have to use for cleaning and rinsing floors and walls.
We even have laws for laws

[US Iceman]

Hi guys,

What we call a red water chiller is just a shell & tube spray chiller used for cooling water, which cools the fresh cut poultry.

These have large tubes in the shell to prevent plugging that may occur from occasional pieces of the birds that get suspended in the water.

We call them red water chillers, since the water is red from the the blood that mixes with the water.

All of the equipment contacting the water is stainless steel.

If the water flow is stopped for any reason, or the outlet temperature drops too low, the refrigerant flow is stopped immediately to prevent freezing.

[Josip]

Hi guys,

What we call a red water chiller is just a shell & tube spray chiller used for cooling water, which cools the fresh cut poultry.

These have large tubes in the shell to prevent plugging that may occur from occasional pieces of the birds that get suspended in the water.
We call them red water chillers, since the water is red from the the blood that mixes with the water.

Thus, water is reused, how many times what about bacterias and other impurities??

I was thinking process water for washing is always fresh and cooling only in shock freezers with air for fresh use or freezing in tunnel.

Food may not be submerged nor sprayed with chilled water, unless it's vacuum packed.

Food is very wide term, do you mean that only fresh tap (warm) water can be used?

Best regards, Josip

[Peter_1]

All what's for human consumption may not be sprayed because there's to much risk for contamination.

You may clean the trucks and the walls outside the building with rain water or water gained form a well /ground source (pumped from deeper layers in teh earth) but all the cleaning inside the factory must be cleaned with tap water.

Cleaning the plastic containers must allways be more then 65°C.

If warm water is used in contact with food, then this should always be tap water but the system must also heat once/day all the lines to a temperature of more then 70°C (158°F).
To do this, every tap point must be connected in such a way that a closed loop can be formed. A pump is then fitted between the lines so that during the lower night rates this can be heated to a return water temperature of 70°C or more.
This is to kill all the legionella bacteria.

[javeedsalam]

i thik this plant looks like an gram plant what he has attached

[The MG Pony]

Why not infuse Ozone to the water thus sterilizing it as it goes through the loop?

[wolf]

use anti frizing ,
keeps temp over 0
degres

[The MG Pony]

Wolph this is food handling you can not use anti freeze.

[Peter_1]

Food grade antifreeze then, we even have it in stock
A new product
http://www.dehon.com/gb/index_gb.php...ion=3&idn3=306

We maintain a plant with 3.000 l in it.

Another one http://www.dehon.com/gb/index_gb.php...oul=2&idn3=196

[US Iceman]

Propylene glycol is listed as a food grade freeze point depressant. It does have terribly high viscosity at low temperatures though. Here is one link...

http://www.dow.com/heattrans/family/dowfrost/index.htm


Or, you can use an alternative fluid that is also labeled as suitable for food use. see the link below. This one has a much better viscosity.

http://www.cptherm.com/CPThermF.pdf


Here is something else that may be interesting...

http://www.floridachemical.com/dlimo..._constants.htm

http://www.floridachemical.com/pdf/D...DES%20MSDS.pdf

[Leonardo Netto]

The water chiller was used in a duck slaughter house.
Yes U could call it a Red water chiller.[Plenty of blood]
I mentioned that it was a one pass water chiller. That means water comes into the plates at 27 Deg C and comes out at 1 Deg C.
The hot gas by pass valve & evap reg were there to fine tune the capacity.If by any chance the water entered the HX at 26 Deg C , U would want to still have it comin out at 1 Deg C and thats when the HG comes in to burn off some capacity.
THE WATER IS NEVER REUSED! For this application.
No Antifreeze was used !
This was an R22 system Running on single stage BITZER compressors.
We put together systems to suit the customer's requirments.
When I first visited this slaughter house, I noticed that they were using a number of flake ice machines to melt the ice in a tank with water to obtain chilled water at 1 Deg C.
It was easy for me to sell them my system on ROI {Return of Investment}
When u freeze and melt the ice, lots of power is wasted.
Your evaporation temperature is much lower when u freeze.
When I built this system I was working for a small contracting company in Singapore.
Today I have a company called "ACE COOL". I do consultancy work. My most recent project was to design and build a low temperature Cascade system for the "Ngee Ann Polytechnic" I built this for the purpose of teaching the students the do's & don't in low temperature Refrigeration.[R507 & R23]
Kind Regards,
Leonardo Netto.

[jamcool]

Leonardo,
With the chill water going to drain,is there still a good (ROI) y was it not filtered and reused in your design as spoken about by the others?

[The MG Pony]

Or at the very least utilize it for sub cooling, or was this don?

Because a secondary HX on the Liquid line to sub cool it with the exhaust water would surly improve the CoP of the system no?

[Sledge]

Hi All;

What is meant by a spray type chiller? Is that another name for direct expansion?

I have done a little work in a poultry plant in Canada, but it was air chilled. I did hear some talk about the water chilling process here years ago...where line speed was matched to inlet water speed...basically a big swimming pool where the chickens were dragged through on a conveyor, and a certain gallonage of water is added per chicken. The concern I heard was that since the water ws being added into a tank, that was already contaminated, hence any water added also became contaminated, regardless of the fact that a quantity of water was discarded at the rate that water was added.

I am wondering why didnt you use an intermediate stage to prevent freeze-up. If the chiller barrel was chilling brine, or glycol, then that glycol or brine loop could be circulated to chill the water and completely eliminate any fear of freeze up? I realize that would add cost to the job, but that cost would be easily justified when compared to the danger of possible freeze-up.

[US Iceman]

What is meant by a spray type chiller?

Imagine the tube bundle of a DX chiller if you will.

In a spray chiller, the water is circulated through the tubes. Refrigerant is sprayed over the outside of the tubes by a refrigerant pump. The liquid being sprayed onto the tubes will evaporate. This becomes the suction gas sucked back to the compressor(s).

Therefore, the water is said to be on the tube-side of the heat exchanger, and the refrigerant is said to be sprayed over the tubes in the shell.

These are completely different from a DX chiller operation.

[Sledge]

In a spray chiller, the water is circulated through the tubes. Refrigerant is sprayed over the outside of the tubes by a refrigerant pump. The liquid being sprayed onto the tubes will evaporate. This becomes the suction gas sucked back to the compressor(s).

Thanks for the explanation. I have never seen one of these. What is the advantage?
I am guessing that this type of evaporator will provide a more consistent heat absorption rate throughout the whole of the chiller barrel? Am I on the right track?

[US Iceman]

Based on what I know about these devices the biggest benefits are:

A) high heat transfer rates
B) very small refrigerant charge

Unlike a DX chiller, a spray chiller essentially has no evaporator superheat, so I guess you could say the heat transfer rate would be more uniform.

One other potential benefit is when the chillers are operating close to freezing temp.'s. If the water pump stops or the water temperature drops, you can shut off the refrigerant pump. The tubes immediately dry off and the cooling stops.

If there is no liquid refrigerant on the tube, it can't cool anything.

[Peter_1]

Or at the very least utilize it for sub cooling, or was this don?

Because a secondary HX on the Liquid line to sub cool it with the exhaust water would surly improve the CoP of the system no?

MGPony, this is indeed a good observation and something to consider.

[binman54]

Leonardo Netto.

In your image "liquid%20chiller.jpg" you show some device on the outlet of the oil separator that is not labelled. Is this a condenser pressure regulator?
Do you control the head pressure? Does it matter?
Cooling water that close to the freezing point I would be concerned about the increase in capacity of the compressor with low head pressures in the winter.
We do this sort of thing using a secondary glycol loop. We closely control the glycol temperature and use it to cool the water. So long as the water is kept above freezing we don't worry about it's temperature. The customer accepts the water at whatever temperature he can get. The water is used for batch cooling of dough; if the water temperature varies then the time to cool varies.

Binman54

[Mike W]

I have seen spin chillers in a ploutry plant that use and ice maker to dump flake ice in the water tank where the chickens floated through to maintain a near zero Deg C water temperature. Another option to get near zero Deg C water temperature is a Jester Jensen evaporator or an ice bank.

Mike W

[snak]

hi
is there any one would like to help me about my project to find the right thick of wall in tropical zone.
and thanks to exept me in your community

[Electrocoolman]

Hello Snak,

I think you will need to start a new thread in order to get answers on this.

I assume you are refering to a coldroom or a freezer?

[Lowrider]

For a chocolate factory in Holland we use a screw chiller producing -10dgr C with glycol and have a separate system with a heatexchanger and large buffer to cool the chocolate. All in stainlesssteel!
Laws in Holland are very strict on keeping any chance off polution of foodstuff to a minimum!

We also have some in poultry-plants with the same setup but with a shell/large tube heat exchanger in stead off a plate heatexchanger due to the possible chuncks of meat in the proces water.

[coztemur]

Hi Leonardo
If you need a precise and reliable solution why do not you put a primer circuit with a buffer tank? You can put a water chiller and set water temp to -5 and you should put some glycol into water. Instead of brazed heat exchanger I think shell and tube H.Ex. is much better alternative because if you have any freezing you 100% will break the plate h. ex. You can get precise point by 3 way valves
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Best regards…
>>
Coskun

[w.l.ong]

Hello Sanderh,
can you send me more info for chocolate cooling process, like cooling tunnel..

for -10dgr C with glycol what thire use for it?
in here i doing lots chocolate packing room and
sometime cooling chocolate machine...

regards.
w.l.ong