Process chiller - Typical operating temperatures?

Hi everyone,

I have an application where the client wants to dehumidify a process gas stream, using a cold water flow.

I have two options:
1. Standard chiller circuit : 7'C delivery, 12'C return.
2. Antifreeze/water circuit : temps to be determined.

I have option (1) fairly well covered, it's option (2) where I need a lot more info.

How low a temp in an antifreeze/water circuit is typical in the industry?
Which antifreeze is preferable : ethylene-glycol, or propylene-glycol (less toxic), from a performance point of view?

Are there any particular additional safety features that should be considered for a low-temp chiller, over that of a standard chiller circuit?

Thanks everyone.

Hi DesA,
propylene is the food grade for incidental food contact and more "expensive ", for a 0.0'C water design have a gycol solution mix for at least -10'C. You will get a chiller HX de-rating, and slight water pump Kw increase with the higher spec density. The chiller HX rating will reduce approx 10 > 15 %, suggest having a buffer tank.

Hi Magoo,

Thanks so much for your applied wisdom. Over here, the ethylene-glycol mix seems to be the main one used, with propylene-glycol a bit of a rarity. The buffer tank makes sense.

We have a similar system with etylene glycol.

It has a back pressure regulator & compressor unloads as well 100/75/50%.

Buffer tank is good if you want constant temps as well as to allow for cycling off
on limit start timer etc.

We used PHE condensoe & evaporator

If the standard chiller option will get you what you need I would avoid the glycol alltogether. It is less effecient and comes with enviornmental issues.

Thanks Ranger1.

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Originally Posted by Emmett

If the standard chiller option will get you what you need I would avoid the glycol alltogether. It is less effecient and comes with enviornmental issues.

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Thanks Emmett. I agree on the efficiency reduction for the heat-exchangers in the water-glycol circuit - these are fairly significant.

If anyone perhaps has a simple flow circuit for the chilled-water side, with buffer tank included, I'd be most grateful.

Hi, desA :)

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Originally Posted by Emmett

If the standard chiller option will get you what you need I would avoid the glycol alltogether. It is less effecient and comes with enviornmental issues.

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Agree with Emmett... sounds like a petrochemical plant... make it simple and your life easy...;)


Best regards, Josip :)

Thanks so much Josip. Much obliged.

chiller barrel with steel case and copper pipe
after staring the chiller there is dust in the chilled water......
from where it is? from the barrel? i mean barrel rusting?
no chemical in the water...
this chilled water used for some critical machinaries?
how we can avoid barrel rusing and cahanging water clour?

please reply

Quote:

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Originally Posted by desA

If anyone perhaps has a simple flow circuit for the chilled-water side, with buffer tank included, I'd be most grateful.

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Hi DesA,

only just seen this one,

I dont have any chilled water circuit diagrams sorry, as they are normally pinned to the plant room wall, A3 size as well, but if they are any use I do have a number of chiller flow charts if interest to you, from standard to de-superheaters & full heat recovery, was just thinking with your hot water from thin air, you might want to consider using available wasted energy with your install

R's chillerman

Quote:

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Originally Posted by desA

Are there any particular additional safety features that should be considered for a low-temp chiller, over that of a standard chiller circuit?

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Hi DesA

a split vessel is a nightmare so as much protection as possible is a must, there is only one thing worse than water in the fridge system and thats glycol, they are both a b*tch to remove

In addition to flow switch, differential pressure switch (water in/out) plus a must if running 7c setpoint that the lp switch is set to at least 0c preferably 1c, you should get away with 1c without tripping when pulling down, then at least you have backup if flow switch fails + dp & flow switch dont always trip when flow is there but low, the lp will

below 6c heat transfer as mentioned above deteriates alot as you will need at least 12c protection below setpoint and 20c below setpoint to be safe on R407c

Hope I am not trying let you know the obvious here mate, but rather look like I am than hear your vessel splits

R's chillerman

Does the stream need to be simply dehumidified or dehydrated?

All comments make sense but for the buffer tank I have some remarks. You only need one if you have a wide varying load and not the possibility to cycle on your compressors (part load ability) If your smallest part load on you chiller matches +/- the smallest load on your system, then you don't need one.
You can also use a(don't now the correct English name) an equilibrium vessel.http://www.caleffi.lt/Resources/cale...i_q/548006.gif
I scanned some pages from the books of Kotza which I will send you (to big to post here) They're in French, ..sorry.

Quote:

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Originally Posted by ckgireesh

chiller barrel with steel case and copper pipe
after staring the chiller there is dust in the chilled water......
from where it is? from the barrel? i mean barrel rusting?
no chemical in the water...
this chilled water used for some critical machinaries?
how we can avoid barrel rusing and cahanging water clour?

please reply

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ck
First when you have a specific question you want to ask it is best to start your own thread.
Second you must add a rust inhibitor or you will continue to degrade the metal in the system and always have discolored water.
Third to clean up the mess you already have I suggest you install a side stream filter and gradually reduce the microns of the filter until the system is clean.

Quote:

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You can also use a(don't now the correct English name) an equilibrium vessel

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Maybe "hydraulic disconnector"?

Quote:

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Originally Posted by Peter_1

an equilibrium vessel.http://www.caleffi.lt/Resources/cale...i_q/548006.gif
.

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Evening Peter

have viewed all day on/off waiting for someone to say what this is

Clues
1. equilibrium vessel
2. air vent on top
3. drain valve at bottom
4. inlet/outlet x4

Not seen or heard of one before so don't know what it's called but at the risk of becoming 'your signature' I shall jump in with both feet now....does flow & return run into this vessel where their temperatures equalize...keeping a more constant load on the system ???

R's chillerman