home brew Heat Transfer

[jcw0220]

I'm looking to come up with the governing equation for the Temperature of my wort (stuff that gets boiled before making beer) as I chill it with a simple heat exchanger. It's a copper coil submerged with tap water running through it. Being out of school for a year or so it seems I've forgot a lot and I'm trying to exercise my brain again. The way I see it is I have two places where heat is being transfer if I neglect radiation. I have heat lost to the ambient air through the kettle a simple qair=hA(Tair-Tkettl). Heat transferred to the tap water through the pipe that will be a function of the surface area of the chiller and inlet temp of chiller. If I remember right I'll add the q's together and set that equal to the change of internal energy (dU) of the wort.
Thanks

 

[hacksaw]

forget the theory you probably should not have copper in contact with the mix

 

[willard3]

You will also have evaporation and latent heat loss.

 

[dcasto]

cooper is ok. Here's how I solved it.

I took my 1/4" cooper line an put it inside a garden hose. On each end I used a 1/2" tee with the cooper line coming out the straight run. The tees are affixed to the hose with normal tapered fittings and clamps. Now the tricky part. You need a comprssion fitting 1/2" NPT to 1/4" compression. You take the fitting over to the drill press and drill it out to the OD of 1/4" cooper. This way the cooper can go all the way though the fitting. Compress the fitting and its sealed. I coiled it up in a 12" coil with 25' of cooper (typical roll).

I then sphyon the wort slowly through the 1/4" and have cool tap water running. Forced convetion on both side, huge transfer rate.

 

[jcw0220]

What latent heat loss where there be, it's not boiling when I start to chill?
and I will make a contour flow chiller one day. It's just not in my invintory yet.

 

[moltenmetal]

You'll get latent (evaporative) heat loss until the moment that the vapour pressure in the air surrounding your wort pot equals the vapour pressure of your wort. Water doesn't have to be at 100 C to evaporate!