Counterflow Chiller - how long to make it?

[The-Engineer-That-Brews]

About to order the bits for a counterflow chiller of the pipe-in-pipe variety, using 8mm micro-bore copper pipe; and I'm trying to decide whether to go for 5m or 10m.

Obvs the longer it is, the faster flow rate can be for a given cooling performance... but equally there's not much benefit going up to 10m if 5m is already doing the business for the flow rate when draining under gravity.

Could anyone who's made one of these share their experience please?

Ta!

 

[simon12]

To much depends on your mains water pressure and temp. What batch size are you wanting to cool?

 

[The-Engineer-That-Brews]

To much depends on your mains water pressure and temp. What batch size are you wanting to cool?

Thanks! I agree that there are intangibles but I was just seeking empirical experience of the "I made mine 5m long, and it's ok so long as I run it slowly" type...

For what it's worth, my mains pressure is 3 Bar at 5-7ºc and the batch size is 21 litres.

Counterflow is a continuous process of course, so when you mention batch size perhaps you were going to suggest an alternative cooling method like an immersed coil... in fact that's what I I do at the moment, but it's a bit slooooow :-) Also I'm thinking I can use a counterflow device to beef up my HERMS setup

 

[simon12]

Normally I would suggest immersion for that batch size for simplicity, but since you are using HERMS thats not what you want. My guess is 5m will be plenty for that batch size. I once made one from 5x3m of 15mm pipe inside 24mm pipe and it cooled 200l in an hour I shaved off 10 mins by recirculating back to the boiler until it hit 80c but any longer added alot more time. Off the top of my head I think the water pressure was 3.5 bar but 10-13c. You could tell that the 1st 3m did around half the cooling and the last 3m was added later and only cut the cooling time 3-5mins.

 

[The-Engineer-That-Brews]

Cheers Simon

I once made one from 5x3m of 15mm pipe inside 24mm pipe

Hmmmm... you know, that's not a bad shout to make it out of 3m straight sections... I could clip it to the wall and it'd be pretty neat.
I'm currently planning to use 8mm microbore copper inside silicone hose, as for HERMS the temperatures look a bit marginal for generic 'hot water hose' (70ºC rated). But the silicone isn't cheap, so maybe 8mm copper inside 15mm sections would be neater. Will definitely look at that.
:thumb:

 

[terrym]

For what it's worth, my mains pressure is 3 Bar at 5-7ºc and the batch size is 21 litres.

Counterflow is a continuous process of course, so when you mention batch size perhaps you were going to suggest an alternative cooling method like an immersed coil... in fact that's what I I do at the moment, but it's a bit slooooow :-) Also I'm thinking I can use a counterflow device to beef up my HERMS setup

Recirculation of the wort batch will assist in cooling. That way you can take advantage of the initial large temperature driving force and that means if you want to, you could reduce the working surface area. The other advantage is that if the pump rate is high enough you might get turbulent flow which is better for heat transfer than laminar flow which you will get with a simple oncve through gravity feed. If you do that I would put the wort through the side which has the least cross sectional area. And I would guess small variations in mains water pressure will not make all that much difference to water flowrate unless you are working in an outhouse with a hose pipe feed from the mains supply when the dP through the hose might be significant.

 

[Dads_Ale]

I use a homemade CF chiller that uses 3m of 8mm copper tube with garden hose pipe outer. This will cool from about 90c to 30c in one pass using gravity (dependent on temp of ground water). So would really need to be longer to get down to say 20c.
I also have an Exchillerator bought CFC that uses larger bore pipe, looks like 10mm, and is about 10m in length (think is has a ridge on the outside of the copper to promote turbulence to increase cooling.. This will chill down to ground water temp in one pass with only minimal water flow. It also has a temp gauge on the output so as you can adjust flows to get the temp you need.
You have to be careful with silicone hose and water pressure as it will blow up like a balloon if you shut the flow off.

 

[The-Engineer-That-Brews]

I use a homemade CF chiller that uses 3m of 8mm copper tube with garden hose pipe outer. This will cool from about 90c to 30c in one pass using gravity (dependent on temp of ground water). So would really need to be longer to get down to say 20c.
I also have an Exchillerator bought CFC that uses larger bore pipe, looks like 10mm, and is about 10m in length (think is has a ridge on the outside of the copper to promote turbulence to increase cooling.. This will chill down to ground water temp in one pass with only minimal water flow. It also has a temp gauge on the output so as you can adjust flows to get the temp you need.
You have to be careful with silicone hose and water pressure as it will blow up like a balloon if you shut the flow off.

Brilliant - many thanks for that, really useful

 

[The-Engineer-That-Brews]

OK after umm-ing and ahh-ing for the normal extended period I decided to go with the 8mm in silicone hose option. I'd actually have preferred to go with four straight runs of 8mm in 15mm copper; I did the full design for that, but annoyingly there were a few impediments to fixing it to the wall where I wanted to.
Anyhow many thanks for the helpful inputs and I'll stick some pictures up when I've got the bits.

 

[The-Engineer-That-Brews]

When I was planning to make it from several straight runs of rigid pipe, it took me a while to think of a good way to do the 'corners' at each end - so I'll share it here in case it's useful to anyone in future.
You could make it slightly more compact by replacing the 'centre' bit of 15mm tubing with a 90º elbow...

 

[Wynne]

I made a counterflow based on silicone hose and 8mm copper piping. I soldered a spiral of copper wire around the outside of 8mm tompromote turbulent flow. I found soldering the end fittings a faff, particularly, the 8mm pipe to reducer joint whilst keeping the silicone hose out if harms way. I kept getting drips from that joint at one end and have dismantled it to have a clean start for another attempt. The whole thing is about 8m long and resembles a giant red Slinky - I need to find a way to stabilise the coils. It cooles 30litres from around boiling to 18C quickly in a single pass but is a bit if a beast compared to a plate chiller.

 

[The-Engineer-That-Brews]

I soldered a spiral of copper wire around the outside of 8mm tompromote turbulent flow

Oh that's genius!
On stabilising the coils, my plan is to wind it onto an old cable drum and clamp the ends to the end-plates of the drum - but we'll see...
Concerning the soldering, I'd definitely better pay close attention to those 8mm to 15mm reducer joints then... I've also seen some people recommend using JB Weld on them instead...

 

[The-Engineer-That-Brews]

Well one of these “10m” pipes ain’t 10m... the orange sprinkler marks the end of the copper one inside the silicone :-)

 

[The-Engineer-That-Brews]

 

[terrym]

What did that lot cost?

 

[ppsmith]

Looks like a really neat job

 

[The-Engineer-That-Brews]

£30 for the 10m x 13mm silicone hose, £17 for the 8mm copper tubing; say a tenner altogether for the fittings...?
Could have shaved £15 or so if I’d done it in garden hose, but I wanted to be able to run it at high temperatures for HERMS

 

[The-Engineer-That-Brews]

Looks like a really neat job

Thankyou, kind sir. I won’t show the piccy of the first end-feed elbow I botched up LoL

 

[fusi]

For the counterflow chiller I will build, I will use 6m of OD10mm/ID8mm copper pipe and OD19mm/ID15mm clear PVC tube. To be able to use the PVC tube without melting it by soldering, I bought 10mm ring compression to 1/2" adapters . The others details are very similar to the pictures in post #14 (thanks
The-Engineer-That-Brews) .Maybe it's not be necessary but I decided to wrap a copper wire around the pipe to allow the water contact all around the pipe . The use of higher diameter pipe would increase the heat transfer surface. True, the flow speed could be detrimental higher but this can be adjusted by acting on the ball valve position.

 

[Wynne]

i made something similar using 10mm copper but chose silicone tube because of concern regarding the safe operating temperature for pvc. I soldered a spiral of copper wire around the outside of the pipe to promote turbulent flow in the cooling water.
It cools very effectively but is a bit unstable as I have yet to find a satisfactory way of holding the all the turns in the coil together. Good luck.