Pre-chiller problems

[wailingguitar]

When we got our 10bbl brewhouse, we had a pre-chiller installed in lieu of a CLT. Specifically this model: http://www.brazetek.com/products/det...xchanger-1-1/4

It was set up to counterflow glycol against our filtered cooling water. It works great during the cold months, but our groundwater gets warm (70Fish) during the warmer months. During winter I could KO in 25-30 minutes, but last summer and so far since the weather has warmed this year, KO is more like 50-55 minutes. Not a big deal on single brew days, but it stacks up on double brews. SO, we decided to add a second pre-chiller into the mix.

Talking to the manufacturer of our system (I will leave their name out of this, but just say they are well known and respected), as well as the plumber who did the installation, it was decided we could hook the 2nd pre-chiller up to run with the water IN SERIES, but the glycol PARALLEL. The idea was that I could cut off glycol to the 1st chiller during the cold months, but have it on when it was warm to bolster cooling.

The glycol comes off the solenoid, hits a T with lines feeding each chiller. Each of these lines has a ball valve to cutoff or restrict flow. The glycol out of each chiller returns to a T and back into the loop. There is also a single ball valve on the return. Once again, I will say both the brewhouse manufacturer and the plumber believed this would work.... It didn't...

I am getting only marginally better cooling, at best, with this installed. Basically a difference of the VFD on the brewhouse pump at 24 instead of 22.5 for the same outflow temp... as opposed to being able to run it at 35-38 during cold months.

Am I going to need to alter the plumbing and run the glycol in series as well? What then about cold months when the ground water is already cool? Would I be able to maybe throttle back the glycol inflow to avoid having the water too cold?

Any thoughts would be most appreciated, I am going crazy here

[barleyfreak]

Can't speak much on the plumbing side. Don't immediately see why it wouldn't work. I also run through a single pre-chiller and am in a similar boat in terms of winter/summer water temps and knock out times. What I do to help out when the water is coming in at about 70 is when I sani the target FV, I'll turn off the glycol to the other FV's, lower the target FV to ~40deg and then run the sani loop (PAA) about an hour before knock out. The FV will stay quite cool during that time and then cools the incoming wort slightly during the first 10-12 minutes or so. I've done it with and w/o this step and it saves about 6-8 minutes overall. The whole process still will take ~45m when the temps are high but it used to be 50-55 before I started doing this.

[J.Scholb]

Temperatures, flow rate and approach

There are many reasons for the problem, but it is pretty simple math to calculate how much heat you are transferring and how much you need to transfer. Here are two principles you need to understand.

Heat transfer. Since water and wort have about the same heat capacity, think of it simply as: if one gallon of water heat ups by 10 degrees then one gallon of wort has cooled by 10 degrees.

The second principle is approach temperature. This is how close the two streams of liquid can get in temperature. It depends on the design of the heat exchanger, but is probably not lower than 20 degrees. This means water at 40F will only get the wort down to 60F. You can cheat, by slowing the flow of the wort way down, which is what you have done.

The suggested fix: "hook the 2nd pre-chiller up to run with the water IN SERIES, but the glycol PARALLEL" assumes the glycol system can handle to heat load, and assumes the problem is that one heat exchanger is too small. This would mean the water flows out before the cold glycol has enough time to cool it. If this were true the glycol should be coming out colder than the water.

Can you provide some temperatures of all the streams in and out and relative flow rates?

[wailingguitar]

There are many reasons for the problem, but it is pretty simple math to calculate how much heat you are transferring and how much you need to transfer. Here are two principles you need to understand.

Heat transfer. Since water and wort have about the same heat capacity, think of it simply as: if one gallon of water heat ups by 10 degrees then one gallon of wort has cooled by 10 degrees.

The second principle is approach temperature. This is how close the two streams of liquid can get in temperature. It depends on the design of the heat exchanger, but is probably not lower than 20 degrees. This means water at 40F will only get the wort down to 60F. You can cheat, by slowing the flow of the wort way down, which is what you have done.

The suggested fix: "hook the 2nd pre-chiller up to run with the water IN SERIES, but the glycol PARALLEL" assumes the glycol system can handle to heat load, and assumes the problem is that one heat exchanger is too small. This would mean the water flows out before the cold glycol has enough time to cool it. If this were true the glycol should be coming out colder than the water.

Can you provide some temperatures of all the streams in and out and relative flow rates?

The two chillers are identical, as in the link above. The incoming glycol is about 27F (set point is 26 on the chiller and it varies from 26 to 28), I cannot say what the flow rate in is. The water coming into the pre chillers is about 70F. The original idea was to split the in flow of glycol between the two chillers so that EACH chiller would be hit with 27F glycol, dropping the water temp coming out of the first to the previous lowest available water temp then for the second chiller to drop it further.

I have no way of measuring the actual temperature of the water coming out of the pre-chiller. It is hard piped into the brewhouse. The only temp/flow rate I can measure is the wort out. I can only hit 75F on the wort and that is at a flow rate of about 5.5 to 6gpm. Achieving this actually requires nearly shutting off glycol flow to one of the two pre-chillers. In essence, there is virtually NO DIFFERENCE between running a single pre-chiller and both pre-chillers. The water going into the wort chiller hits about the same temp regardless

[J.Scholb]

Pre-chiller problems

More information is needed to determine the cause. Just touching the outlet piping should give an indication of the temperature. My guess is the glycol is coming out pretty warm, above 55F and the water should be 65F or hotter to only cool the wort to 75F at low flow rate.

It's still not clear if the problem is low flow of water, low flow of glycol or a small HX (although if two HX's don't help then it's probably not the problem)


This tool is very helpful as well for troubleshooting, only $35.

Non-Contact Infrared Thermometer With Laser Targeting

http://www.harborfreight.com/non-contact-infrared-thermometer-with-laser-targeting-69465-8905.html

[Bonanza]

Pre and and chiller

I have to struggle with this problem all year long.
I live in Ecuador in the coast with an ambient and water temperature of around 86F.
We use a similar chiller you have for a 5BBL brew house as a primary chiller, followed by a inline chiller I made.
That chiller is refrigerant cooled and brings the wort to 68F for Ale yeast pitching and 55F for Lager. It’s a 40 plate 18” long duda diesel chiller connected with a 3 HP cooling compressor.
I would not be able to get to pitching temps without this gadget, it’s so important that I will build another one as a spare chiller.
As I have 86F cooling water the wort gets in the pre chiller to around 92F, than pass the inline chiller where I can regulate by flow control the temperature to what ever I want in the fermenters.

We use single wall fermenters in a walk in cooling room and chilling down in the tanks is no option.
Joe