Immersion Chillers - why does cold water feed the bottom of coil?

I was reworking my IC yesterday and when hooking up my inlet & outlet hoses, I thought: If heat rises, why send the cold water feed to the bottom of the coil (where wort is cooler) vs sending it to the top of the coil where the heat is of the wort is greatest?

Wouldn't it be adventageous to have the coldest water meet the warmest wort - that's at the top?

Just wondering what the thought is on this.

I would think that the wort would be hotter at the bottom due to the contact with the bottom of the pan. Just like soup in a bowl... it cools at the surface quicker than at the bottom where there is no air.

I can only guess that because you’re shooting cold water directly to the bottom of the coil and then having it work its way up, you’re getting broader coverage of cold/cool water throughout the wort.

That cold water heats up very quickly once it enters the submerged tubing and if it begins to coil on the down-direction instead of the up direction, the span of cold/cool water is smaller.

Probably because someone didn't think it through. Feeding cold water to the bottom of the cooler will result in stratification if you don't stir. Some coolers are designed with most of the coils near the top, but that can be a problem if you have a wide kettle and they aren't submerged.

Gentle stirring speeds up the process, regardless of the flow direction or coil configuration.

My IC is set up with the same connections on the IN as well as the OUT. Never really paid attention which end I hooked up to the house or drain. So, basically I haven't noticed any difference in over a year of using it.

without having a good picture in my head what it is you have going on I can tell you that I got enormous improvement in my immersion heat exchanger when I did three things:
1.) I added an extra coil that runs horizontal inside the larger diameter coil that coils vertically http://s1002.photobucket.com/albums/af143/zydaco/?action=view&current=0107101512a.jpg&newest=1
2.) ran each coil on fresh cold water to double the cold water flowing through the coils http://s1002.photobucket.com/albums/af143/zydaco/?action=view&current=0107101513a.jpg&newest=1
3.) and raised the whole rig on little legs to keep it up near the top of the wort.



The result is I get un-stratified cooling of the wort 'cause the cold wort falls and the warm rises. The thermally driven movement of the warm and cold wort does all the stirring for me.

I always hook mine up so the cold water goes into the top.

I always stir my IC. It decreases the chill time from 20-25 min to 12 min.
I have a cheap home-made IC, the copper tube is probably too thin, but it's long, and it's a real messy coil, but I use it to stir the cooling wort and it works great. It takes about 10 gallons of cold tap water to chill 5 gallons from boiling to almost room temp. in 12 minutes.

Air rises, so having water go in at the bottom and out the top ensures that no air pockets will build up?

here's my 50' x .375. i cool top and bottom with separate coils.

Good question....seems like if you cooled top-down, the cooled wort at the top would start sinking and create turbulence in the wort. There would be no stratification, and stirring probably wouldn't be necessary? Who knows?

I think if you soldered SS tubing to the inner sides of a pot you could have a nice integrated design...you could start at the top and go directly through the bottom of the pot with your exhaust, keeping the design low profile. 100% of the coolant would touch your wort this way. Does all this make sense?

avshook said:

I always stir my IC. It decreases the chill time from 20-25 min to 12 min.

Click to expand...

That was one of the problems I was looking to address when I revamped mine. It worked wonderfully.
No more stirring for me.

I have a cheap home-made IC, the copper tube is probably too thin,

Click to expand...

It's only too thin if it is so fragile (because of how thin it is) that it breaks. Otherwise, thinner is better. Metal will has its own thermal inertia. Thicker metal has more.

I always give a stir using the cooler its self and that definitely speeds up the process.

In theory, if the coldest water hit the warmest wort (the top) the heated water will not be as effective cooling the wort in the bottom of the kettle. I'm sure it won't make more than a few minutes difference but it should go to the bottom first so when the water is the hottest it's exiting the cooler. Same hold true for a condenser on a still.

All the discussions about which way the water should flow in an IC is just silly. There's no reason to kill your cooling efficiency by trying to let convection currents move the warmer wort around. You should be stirring (by hand or with a wine-degasser), or pump whirlpooling.

I have a feeling that on our scale, it doesnt really matter much. Most people are stirring thier wort as they cool and such anyway, or recirculating thier wort.

I think that in 5-10 gallons of wort you wont see much difference in cooling with top or bottom fed chillers. Mine has the same fittings on both ends, I can choose... but I dont think it matters.

mordantly said:

here's my 50' x .375. i cool top and bottom with separate coils.

Click to expand...

Now, THAT's a chiller! Nice job.

avshook said:

I always stir my IC. It decreases the chill time from 20-25 min to 12 min.

Click to expand...

That was one of the problems I was looking to address when I revamped mine. It worked wonderfully.
No more stirring for me.

I have a cheap home-made IC, the copper tube is probably too thin,

Click to expand...

It's only too thin if it is so fragile (because of how thin it is) that it breaks. Otherwise, thinner is better. Metal will has its own thermal inertia. Thicker metal has more.

Jknapp said:

Now, THAT's a chiller! Nice job.

Click to expand...

thanks. cost: $45 for the roll of copper at ace.

25' wrapped around a 5# alumi co2. 25' wrapped around 20# alumi co2.

i have warped my head thinking about it. once the inlet water has removed heat energy, it can't remove anymore. thus i cool both ends of the keggle simultaneously, although, i might need to remove the outlet 2-1. (i might have uneven flow). also need to rework the top bends with elbow joints to make it sit a smidge lower in.

mordantly said:

i have warped my head thinking about it. once the inlet water has removed heat energy, it can't remove anymore.

Click to expand...

Which is why most of these discussions are a waste of time.

If you want to make a better chiller, focus on methods of getting more volume of water through the wort, and stirring the wort.

A whole bunch of real short coils with independent water supplies would cool about as quick as possible.

heat exchangers operate on temperature differentials. Cold wort vs a slightly colder chiller will cool the wort some more at the bottom. As the cooling fluid moves up the heat exchanger it will warm up, but will be chilling hotter wort, maintaining a temperature differential. That's the theory anyways. On our scale probably not enough variation in temperature from top to bottom to worry about. stirring does help though by keeping colder spots from forming near the chiller.

The best way to increase temperature differential is not to pipe water from the surface to the bottom, but to force convection. If the flow around and flow inside the chiller is not turbulent, then a temperature gradient will form and heat transfer will plummet.
stir, stir, stir.