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giovanni
16-01-2007, 04:08 AM
If we were to change out the proplyene to ethylene would it be as simple as flusing it out with water and recovering it. Do we have to wait for the ice to melt or can we simply shut the chiller, wait a period of time so the water would not freeze while flushing.

Josip
16-01-2007, 10:04 AM
Hi, Giovanni :)


If we were to change out the proplyene to ethylene would it be as simple as flusing it out with water and recovering it. Do we have to wait for the ice to melt or can we simply shut the chiller, wait a period of time so the water would not freeze while flushing.

The best is to shut the freezer with glycol pump running, wait some time to defrost system to avoid any problem;) and then drain it completely but recover and maybe to sell it later to someone;) .

Flush the system with clean water and drain again, but not into sewage:eek:

If you know approximately the amount of glycol you need you can prepared it outside and then just pump it in.

Someone can say no need for all of this but you must know what and how much you put in your system to make a proper paper work, whatever....

Yes, a lot to do but we must take care about environment :D

Best regards, Josip :)

US Iceman
16-01-2007, 02:03 PM
I worked on a glycol system one time that had the wrong type of glycol pumped into the system. The contractor decided to use automotive anti-freeze instead of heat transfer glycol.

It was his first and last chiller project.:rolleyes:

The chiller was a Dunham-Bush unit with their semi-hermetic recip. compressors.

Dunham-Bush (at that time) told me to flush the entire piping system (chiller, pipes, and coils) with clean water first to remove as much of the old anti-freeze as possible. Then use warm water and some detergent (dishwasher soap I believe it was) to clean the system. After that, one more flush with clean water.

I believe you need to use very clean water (almost distilled) to pre-mix the new glycol in the proper concentration. Then pump in the pre-mixed fluid into the piping system.

It was a pain to do all of this, but it seemed to work very well.

Are you using Dowfrost for the new fluid?

frank
16-01-2007, 08:38 PM
I believe you need to use very clean water (almost distilled) to pre-mix the new glycol in the proper concentration. Then pump in the pre-mixed fluid into the piping system.

Thats right Iceman. If you use ordinary tap water you can run the risk of introducing contaminants that eventually cause a build up of scale in the system. De-mineralised water should always be the first choice. http://www.propyleneglycol.co.uk/antifreezeguide.html

US Iceman
16-01-2007, 08:55 PM
4. Automotive antifreeze should not be used in industrial cooling systems, as the high levels of silicate therein can reduce heat transfer rates and precipitate as sludge.


That's exactly what I found. The anti-freeze looked like some polymer goo that was nasty. The stuff coated the tubes, so the TXV's could not control the superheat steady and flooded the compressors.

It was about 25 years ago when I had the "opportunity" to work on this system, and I have to say, I learned more about chillers on this one project than any other time.

One other thing I recently learned about is bacteria in some glycol systems. Some of these "bugs" eat the glycol and make a similar kind of goo, which plugs up strainers.

giovanni
17-01-2007, 08:41 AM
Thanks for the replies guys. Josip we are using an air cooled chiller with 2 screws for an ice rink. When you say defrost the system do you mean the chiller or the ice in the rink? How long to defrost chiller if that is what you are referring to?

Us Iceman, we currently are using dowfrost 40 percent solution (proplyene) and it has been in the system for about 9 years and thinking of changing to ethylene for a better heat transfer and less geling of the glycol. Also is there a life expectancy on glycol?

Frank, I wasn't aware of the demineralized water issue thanks

And of course protecting the enviornment is a fundamental issue....

absrbrtek
17-01-2007, 12:33 PM
Why do you want to change from propylene to ethylene glycol? Most people go the other way due to the environmental concerns.

US Iceman
17-01-2007, 02:44 PM
...thinking of changing to ethylene for a better heat transfer and less geling of the glycol. Also is there a life expectancy on glycol?


Don't think of the glycol as "gelling up". Think of it as an increase in thickness. As the temperature decreases the viscosity increases. It's true propylene glycol is worse than ethylene glcyol for pumping and heat transfer, but I don't think I would change it.

The corrosion inhibitors can wear out. You need to periodically test the glycol for these. And, make sure any water make-up valve is turned off. I've seen some systems with these and they create some problems if a leak develops. Besides the leak itself.

giovanni
17-01-2007, 10:03 PM
Here is some data that I recieved in using different liquids in a Carrier 30XA 220 ton air cooled unit.

95 degF Outdoor Air, 200 gpm of 40% ethylene 15degF setpoint (Leaving water temperature "LWT") = 78 tons capacity.
Same conditions with Calcium Chloride would increase the ton capacity to 106! That assumes the 200 gpm will remain constant but that will increase with the use of CC as the viscosity is much less making it easier to pump thru the system.
75 degF Outdoor Air, 200 gpm of 40% ethylene 15degF setpoint (LWT) = 80.1 tons capacity. With CC you will increase to 112 tons.
We are currently using 40% proplyene and the above numbers seem to suggest an increase in efficiency by changing to either ethylene or CC. Any comments or ideas ?

NH3LVR
17-01-2007, 10:46 PM
Giavanni;
This is a little outside of my area, so please consider these as much as a questions as comment.
Is the increase in capacity based on the theoretical heat carrying capacity of the glycol versus the CC?
Can the chillers provide the additional cooling?

US Iceman
18-01-2007, 12:53 AM
NH3LVR, the increase is strictly due to the difference in fluid properties. Think of it like this: Q=M X Cp X TD

Q=Btu/hour
M=pounds per hour circulated
Cp=Specific heat of the fluid
TD= temperature difference between entering and leaving fluid temperatures

If M & TD are held constant, the increase (or decrease) of the specific heat due to the fluid properties raises or lowers the overall amount of heat transferred.

Calcium Chloride is a good brine if used with care. It's not a silver bullet or cure-all. The same could be said for the alcohols.

Giovanni, have a look at some of these fluids too.

http://www.cptherm.com/

If you are looking for energy efficiency, you should not have used air-cooled condensers. These really limit the amount of discharge pressure reduction you can achieve.

giovanni
18-01-2007, 02:43 AM
From what I was made to understand was that changing to ethylene or Brine would increase flow and heat transfer and therefore render the system more efficient. I am not an expert in this field and just trying to ascertain if the info is correct and is it worth the effort. We are having a bit of a problem using the proplyene due to its viscosity and looking to change it out if its more efficient and helps our energy savings.

NH3LVR
18-01-2007, 03:17 AM
The reason I questioned this is because I once ran a system with two 270 ton chillers. The propylene glycol percentage was 30%. The design engineer told me if I dropped the % to 25% I could get more cooling.
Unfortunately that was not the case.
Although the specific heat of the 25% solution was greater, in times when I needed it the most the air cooled chillers were maxed out. Any further heat transfer only caused the compressors to unload on high amperage.
I do realize the efficiency is greater with better heat transfer. Whether or not that is significant is another question.
I was went buy a local hospital that is reopening the other day. Two brand new air cooled chillers siting outside. By my calculations they cost about one third more to operate than a evaporative condenser system.

US Iceman
18-01-2007, 03:20 AM
We are having a bit of a problem using the proplyene ...


What exactly are the problems you are experiencing? If you could list them for us, we can take a shot at each one.

PS. Who is suggesting the change in fluid? Carrier or a fluid salesman?

giovanni
18-01-2007, 06:29 AM
We are not able to reach the set point for the water leaving temperature of 15 degrees "F." The average LWT is about 18.5F and the unit is set for 15F. The glycol seems to thicken up and flow is reduced. Yet when we were using a rental chiller "Trane 200 ton air cooled" we were able to have perfect ice with the same glycol (proplyene). Suppossedly the chiller barrel configuration where the glycol is chilled was changed with the introduction of this new unit where the ***** is in the barrell and the glycol flows thru tubes inside. The opposite is true with the Trane Unit. (so we were told) My boss had them re-hook up the rental and again we have no problems with ice conditions. Its a puzzling situation. The manufacturer is recommending the glycol change. The reason they bought an air cooled system is that funds were limited and this is a sort of mom / pop business. Also thanks for the link, interesting site and product...

US Iceman
18-01-2007, 02:55 PM
Suppossedly the chiller barrel configuration where the glycol is chilled was changed with the introduction of this new unit where the ***** is in the barrell and the glycol flows thru tubes inside.


Now that is interesting. That sounds like a flooded chiller. What is the listed refrigerant charge? Do you have a model number for the Carrier chiller? I can't imagine a manufacturer using DX feed on the shellside of a chiller.

If the tubes are 5/8" or less, then you might well have some problems due to viscosity. On a small tube, you need a lot of velocity (increased pump power) to establish good heat transfer.



The manufacturer is recommending the glycol change.


Is the manufacturer the same one who told you his chiller would work?

And,

His he also paying for all of the rental chiller charges, changes, lost business, and fluid replacements while still providing a warranty?

frank
18-01-2007, 08:55 PM
This sounds like the heat exchanger has been replaced and has a smaller LMTD which will affect the original calculations.

giovanni
19-01-2007, 08:31 AM
the model is a Carrier 30XA 220 tons and yes they recommended this model. We had the rental hooked up last week and we are not being charged for its use. Using the rental there is only a 5 lb difference in pressure relative to the glycol coming in and out. In the Carrier unit when it is reset the difference is about 7 lbs but rises to 20 lbs difference in about an hour or two and supposedly it is the proplyene glycol that they are saying needs to be changed. Our pumps have a 200GPM rating. Amazingly all is well with the rental unit. The chillers are basically the same , 2 screw compressors , air cooled except for flow in the the chiller barrel , so we were told.

US Iceman
19-01-2007, 04:20 PM
Using the rental there is only a 5 lb difference in pressure relative to the glycol coming in and out. In the Carrier unit when it is reset the difference is about 7 lbs but rises to 20 lbs difference in about an hour or two...


If the pumps and the glycol are the same for either chiller, and the operating conditions are the same, the only reason the pressure differential would be any different between the two chillers is:

1) The pressure loss of the hoses (to the rental chiller)
2) The pressure loss of the chiller barrels

The pressure should not vary headly at all other than the minor differences noted above.

You mentioned something about resetting the Carrier unit. What are you resetting?



...and supposedly it is the proplyene glycol that they are saying needs to be changed.


That does not make any sense at all. If the glycol works on the rental chiller, why does it need to be changed on the permanent chiller? See what I mean?

giovanni
20-01-2007, 08:09 AM
When the pressure differential reaches a 20 lb difference (pressure into the barrrel and pressure out of the barrel,which is usually 80 lbs in and 60 lbs out) we were told to shut it down and restart the unit until a final solution can be found. The problem is the flow of the glycol in and out of the barrel and their solution is the changing of the glycol to ethylene or use brine. They claim the glycol is freezing up in the barrel. The rental is running fine with a pressure of 68 lbs in and 63lbs out as an average and stays within a 5 lb differential which is puzzeling. I understand perfectly what you are saying relative to it working fine with the rental. Same pumps, same glycol. Were starting to think the new unit is a LEMON

Again their claim is the configuration inside the barrel of the new unit.

US Iceman
20-01-2007, 06:33 PM
Were starting to think the new unit is a LEMON


Well, I did not want to be the one to say this first.;)

The thing to remember when analyzing a problem is to look at the obvious and visible facts. If the ice is OK with the rental chiller, and the existing pumps and glycol then why does changing the glycol correct any problem?

It is certainly not a problem with your existing pumps or glycol, or the rental chiller is it?



Again their claim is the configuration inside the barrel of the new unit.


Then that's their problem not yours directly. In sofar as its your problem, this only is apparent by the lack of performance of the new chiller.

If they cannot make their new chiller work at the same conditions as the rental (which I assume is meeting all of your requirements), then someone has an equipment liability issue and contractual obligation. But I'm not a lawyer either.:)

NH3LVR
20-01-2007, 08:08 PM
I was just wondering if there was a minimum suction setpoint on the chiller controls? Or are the slide valves set by the LWT only?:confused:

US Iceman
20-01-2007, 11:48 PM
HI NH3LVR,

It sounded to me as if the chiller was running flat out and still not achieving the LWT. Probably due to whatever problem that exists in the new chiller.

The new chiller capacity is either insufficient to produce the capacity they need and they want to change the glycol to improve that situation, or, something is wrong with the new chiller.

It really burns my backside when I hear of customer buying new equipment that doesn't work. There is absolutely no reason for those guys (the ice rink owners) to have to go through this painful process.

giovanni
26-01-2007, 08:15 AM
The new chiller is actually 20 tons bigger than the rental and the rental is working like a charm. We had glycol analyzed and it came back excellent. Pumps are also in good condition. This is a new product that Carrier put out. They have sold a few already but I'm leaning in the direction that this one just might be a lemon.

US Iceman
26-01-2007, 03:02 PM
I recently had a conversation with a contractor who has installed several of these chillers and a similar one from Trane.

Apparenty, the chiller uses some type of spray header over the tube bundle. The TXV meters the refrigerant into the spray header, and the refrigerant sprays down over the tube bundle.

This works well on industrial chillers, but for some reason (unknown) you are having problems with yours. Does the rental chiller have the TXV's feeding the tubeside of that chiller. Just curious.

giovanni
27-01-2007, 09:03 AM
From what I was told, (I am not a refrig engineer,but learning alot), On the Trane unit(rental, model RTAA200) the ***** is in tubes and glycol runs through the chiller barrel. On the Carrier unit the glycol, when pumped into the barrel, passes through tubes in the barrel and is then cooled as it passes through the barrel. This is supposedly why there is such a large pressure differential in the Carrier unit relative to pressure in and pressure out of the barrel . When the Carrier unit is restarted (a manual reset) there is about 8 lbs of differential and then increases to 20 or more lbs within a hour or so. The Trane unit keeps a steady 4-6 lb differential at all times. I hope this is what you are asking. Thanks

Andy
28-01-2007, 07:50 PM
Hi Giovanni

A flooded barrel as described by the fluid in the tubes should have a lower pressure drop on the fluid side, dependant on the passes (the number of times the fluid goes up and down the chiller).
I think you have a chiller barrel design problem.
Tell carrier such and ask them to change the barrels for a new larger design. If this does not work or they won't let them keep the chiller and sue them for your deposit.

Kind Regards Andy

Josip
28-01-2007, 08:18 PM
Hi, :)


Hi Giovanni

A flooded barrel as described by the fluid in the tubes should have a lower pressure drop on the fluid side, dependant on the passes (the number of times the fluid goes up and down the chiller).
I think you have a chiller barrel design problem.
Tell carrier such and ask them to change the barrels for a new larger design. If this does not work or they won't let them keep the chiller and sue them for your deposit.

Kind Regards Andy

Seems that Carrier has made some optimization on chiller, the question is for whom?;)

Best regards, Josip :)

giovanni
29-01-2007, 07:25 AM
Supposedly they tried to optimize the barrel (or so we were told). On the Tranel unit (rental, we are not being charged for it) the pressure has a steady 4-5 lbs of difference in and out of the barrel which averages 55 in and 59 out. On the new Carrier unit the difference in pressure starts at approx 68 in and 60 out when started but rises to 80 in and 60 out in about an hour or so and cannot reach its set point of 15 degrees F. It just barely hits 18 degrees F and both compressors are running flat out as opposed to the Trane which is just running one compressor at only 60% capacity. Both users guides describe the barrels as shell and tube.

giovanni
29-01-2007, 07:46 AM
I had to post a 2nd reply. Tried to edit and couldnt save the post..
Both barrels are shell and tube but the Carrier unit mentions "flooded" in the manual and is also a "1 plus pass." As US Iceman mentioned earlier the Carrier unit is running flat out and cannot reach the set point of 15 degrees F. Whereas the Trane unit is running only 1 compressor at 60 % capacity and conditions are perfect. Andy, Thanks I'll mention your advice about the barrel to the owner and take it from there. And "THANK YOU" to all who took the time and patience for all your input. It is greatly appreciated.

Perseus
24-11-2007, 06:27 AM
Chiller barrel design is dependent on quite a few parameters. One of these is what the specific secondary fluid is and what concentration it is. Typically the ice rink chillers are ethylene glycol with a 40/60 mix. If the wrong fluid is used the design could be off. If this is the case the chiller running at full capacity to pull down to temp can possibly have a lower core temperature in the chiller. This will cause the fluid to gel. Having the wrong percentage of glycol in the mix also causes other problems that can be related to this. If the chiller is designed for 40/60 and someone puts in 45 or 50 percent of glycol the pumps will have a harder time moving the fluid(the pump curves will be different) and the heat transfer in the chiller is less causing a loss of efficency.

I have also seen in a DX chiller the suction filters plugged to the point of lowering the suction temp to below the freeze protection of the secondary fluid. This caused the chiller to start to freeze up. The unit was fine in the morning, but as the day progressed the temperature of the fluid kept rising and the system compressors all cycled on to bring the temp down. But with a semi-frozen chiller it would not get any better until the load was reduced in the evening. Things settled down and the process started out again the next day.

WINJA
24-11-2007, 09:10 AM
What exactly are the problems you are experiencing? If you could list them for us, we can take a shot at each one.

PS. Who is suggesting the change in fluid? Carrier or a fluid salesman?
Good question , cause ive never dumped glycol , i just measured the specific gravity and altered acordingly