two-stage heat exchanger pros and cons

[lhall]

We are looking at going to a two-stage heat exchanger for our wort cooling. Can someone who has this type of system comment on its pros and cons? We knock out 16 bbls at a time, three times a day, our city water temp hits 90F in the summer, and we have a 7 ton chiller that we can use. I'm thinking that we can isolate the chiller just for the knockout and hopefully quickly get its temp back down afterwards to use for fermenter crashing, etc.

[boussh]

We use a two stage Mueller (first stage is 40 plates city h2o, second stage is 15 plates glycol) at the pub, the only con i have about it is that on a nice summer day and more than 2 10bbl tanks at 50 or below, our 7 ton compressor cant keep up and the draft lines get a little warm, causing some foaming at the tap. Usually catches back up in about 15-20 minutes after knock out. I try to time my brew day so that this happens after our lunch rush and before happy hour. Doesnt always happen though.... During the winter thats another story!

[dick murton]

I assume you use the recovered hot water from the PHE for mashing, sparging and cleaning. If you are not, that is what you use the first stage for, and the second stage for cooling directly from (gulp!!) about 100 F down to pitching temperature. You could try using the chiller to cool a batch of water whenever the demand is required for FV cooling, and if this can use cheap rate electricity, (we get this in the UK overnight, when the bulk of the office workers are home and asleep, not partying or watching the box - not sure what your situation is). Then the water is ready cooled for chilling wort. You still need to re-use it though.

[Todd]

A dual phase heat exchange process can put significant cooling loads on your chiller causing tempurature rises in other areas of the brewery. You definately need to analyze the cooling requirements and specs for your heat exchange process and the current demands and capacity of your chiller. I would avoid doing this blindly! If you have spare room, you might consider a CLT with a pre trim cooler for incoming city water. This trim cooler and CLT method will have a less significant impact on the demands of your chiller, while minimizing your cooling water requirements.

- Todd

[jimvgjr]

Here's a cooling load example related to second stage cooling:

Batch size: 10 Bbls
processing time: 60 minutes
Wort starting temp: 90 F
Wort ending temp: 70 F

cooling load: approx. 52,000 BTU/HR

This load scenario would require a 5 to 7.5 HP chiller system.

The previous posts were right on, if you don't have the surplus chiller capacity, a cold liquor tank is a great option. It allows you to stretch this cooling duty out over several hours, and possibly cool it down during off peak electrical rate hours (as Dick mentions).

Good Luck,

Jim

[Michael Murphy]

My system has two seperate HE's, I used to run the wort through both and used the second smaller one with glycol as needed. But one day the glycol HE was clogged so I bypassed it and I realized I could knock out the wort in half the time, so what I did was run my cooling water through the glycol HE and I use that to cool the city water for the first HE if needed. It can still get the wort down to lower than 10c if I want it.

Its also one less HE to deal with...

[Fred Scheer]

We are looking at going to a two-stage heat exchanger for our wort cooling. Can someone who has this type of system comment on its pros and cons? We knock out 16 bbls at a time, three times a day, our city water temp hits 90F in the summer, and we have a 7 ton chiller that we can use. I'm thinking that we can isolate the chiller just for the knockout and hopefully quickly get its temp back down afterwards to use for fermenter crashing, etc.


Sorry to reply today, but was out for several days.
Linus, following is a brewkettle info I used in the past:

City water: average *F during summer time
Hot wort in .... *F
specifi heat of wort........ .92
BBL/hr
weight of wort............lbs


How much heat must be removed from X BBL/hr of X *F cooled to ..*F?

BTU = Wt. X specific heat X ∆ T

How much water must be used to remove BTU/hr wort cooled from...*F to... *Ffrom wort with X*F water inlet, X*F water outlet?

BBL/hr = BTU/hr/T / (wt/bbl)

How much heat must be removed from X BBL/hr of X*F City water to cool to X*F?

BTU/hr = WT X ∆ T

How much water must be used to remove X BTU/hr from water with inlet temperature of X*F, outlet temperature of X*F ?

BBL/hr = BTU/hr / ∆ T / wt/bbl

I hope the forgoing helps, and if you need more help, just stop by...we have a beer and discuss............. :)

Fred