Optimal plate chiller operation

The forum for discussing all kinds of brewing paraphernalia.
Post Reply
Patterd Ale
Hollow Legs
Posts: 418
Joined: Tue Jun 29, 2010 6:40 pm
Location: Gloucestershire

Optimal plate chiller operation

Post by Patterd Ale » Thu Jan 23, 2014 7:17 pm

Evening All, plate chillers are simple bits of kit to operate. Usually I put cold to maximum (commercially), start hot flow from slow and increase until it reaches desired temperature. Then knock back the cold input and adjust for maximum efficiency. Theoretically when the hot water flow out is at its hottest it must be removing the most heat, I usually find that from this point a small increase in the cold flow is optimal.
Does anyone have a better method please?
Also, one commercial chiller I use works as expected for 2/3 of the transfer, then the temperature increases and nothing I can do consistently controls it. The cold input water appears the same, as does the hot wort in. No apparent leaks. Any ideas? Most infuriating!
Thanks all.
PA

Patterd Ale
Hollow Legs
Posts: 418
Joined: Tue Jun 29, 2010 6:40 pm
Location: Gloucestershire

Re: Optimal plate chiller operation

Post by Patterd Ale » Wed Jan 29, 2014 9:24 pm

It appears that extending the plate pack is less straight forward that one might think. Apparently it may now be configured incorrectly, oopsy. To be fair the instructions are quite confusing!

User avatar
gregorach
Under the Table
Posts: 1912
Joined: Wed Jun 08, 2011 10:07 am
Location: Edinburgh
Contact:

Re: Optimal plate chiller operation

Post by gregorach » Thu Jan 30, 2014 2:14 pm

Patterd Ale wrote:Theoretically when the hot water flow out is at its hottest it must be removing the most heat
Not at all - when the wort out is coldest is when it's removing the most heat. Say you pump the entire Atlantic Ocean through the cold side of your plate chiller - you're going to chill the wort to exactly the same temperature as the coolant, yet the coolant will show no measurable rise in temperature, simply because there's so much of it. Temperature and heat are different things - there's far more heat in a warm bath than there is in a boiling kettle.

The key question here is: what do you mean by "efficiency"? Are you trying to cool the wort to pitching temperature in the shortest possible time, or are you trying to minimise the amount of water used? If it's the former, then you want the maximum wort flow rate that you can cool to the desired temperature with the coolant temperature and flow rate you have available. If it's the latter, that's when you want to adjust for the maximum coolant outflow temperature that can still give you the desired wort temperature.
Cheers

Dunc

Patterd Ale
Hollow Legs
Posts: 418
Joined: Tue Jun 29, 2010 6:40 pm
Location: Gloucestershire

Re: Optimal plate chiller operation

Post by Patterd Ale » Thu Jan 30, 2014 6:30 pm

My physics has always been poor!
I want to cool the wort as quickly as possible, meaning the highest flow rate possible and damn the water usage. Perhaps your knowledge may be able to give a theoretical ideal? I suspect that maximum flow rate of cold through the chiller is not the way to achieve the maximum cooling possible. But, what principle is?
Trial and error has always worked, I would like to understand the principle better.
Cheers.

millmaster

Re: Optimal plate chiller operation

Post by millmaster » Thu Jan 30, 2014 11:34 pm

The theory ( or some of it ! ) works roughly like this

The heat exchanger needs to be connected up such that coolant going in meets wort going out ( counter flow ? )
You will never get wort out colder than coolant in
You will never get coolant out hotter than wort in

Operating it in the way you describe solves for minimum coolant flow ( hottest coolant out ) for set wort out temperature so its pretty efficient way to operate I'd say.

I presume you use mains water as a coolant ? If so then water and wort have the much the same heat capacity, so with an appropriately sized clean heat exchanger, then coolant and wort flow should be much the same

Increasing heat exchanger area will allow more wort to be cooled to the same temperature
Increasing coolant flow in by increasing the pressure ( it may not be an option ) will allow more wort to be cooled to the same temperature

Its all in the heat transfer equations ( like physics, but real world physics ie engineering ! )

You refer to a chiller working erratically, but I'm not sure exactly what you mean ? Are you referring to the heat exchanger itself or to a refrigerator type unit that cools the water that then goes through the plate heat exchanger ?

If you mean some sort of fridge, then does it need re-gassing ? Fridges need a gas to move the heat about, that gas can leak and as the volume of gas reduces as it leaks then the fridge performance decreases - my air-con in the car failed like that, it got less and less effective until I had it re-gassed

User avatar
gregorach
Under the Table
Posts: 1912
Joined: Wed Jun 08, 2011 10:07 am
Location: Edinburgh
Contact:

Re: Optimal plate chiller operation

Post by gregorach » Sat Feb 01, 2014 1:31 pm

Patterd Ale wrote:My physics has always been poor!
I want to cool the wort as quickly as possible, meaning the highest flow rate possible and damn the water usage. Perhaps your knowledge may be able to give a theoretical ideal? I suspect that maximum flow rate of cold through the chiller is not the way to achieve the maximum cooling possible. But, what principle is?
Trial and error has always worked, I would like to understand the principle better.
Cheers.
If you want to cool as quickly as possible, then you simply want to maximise the flow rate of the coolant. You're not trying to heat the coolant, you want to maintain the maximum temperature difference between the coolant and the wort, and you want as much coolant as possible going through the chiller as quickly as possible. You also want the coolant to be as cold as possible.
Cheers

Dunc

Post Reply