The reason I was messing around with vacuum pumps in my last post is so I can pull wort through a new type of chiller. Now that I've got the pump part somewhat figured out, I did some work on the chiller part.
Unfermented beer (wort) needs to be boiled and then rapidly chilled, since there are some chemicals that form in hot wort that can produce off flavors in the final beer. Ideally you want to take the wort from 220F to 80F in around 15-30 minutes. There are various methods and devices that are typically used to do this.
One method that I have not seen used before is using a graham condenser tube. This is usually used in chemistry labs to condense vapor into a liquid. It's basically a spiral glass tube with a larger straight glass tube on the outside. Cold water is pumped through the outer glass jacket around the inner spiral glass tube to cool it down. the vapor is passed through the inner spiral tube and it hopefully coalesces into a liquid before coming out the far end of the tube.
The only difference between chilling wort and the usual use-cases for the graham condenser is that liquid, not vapor, would be the input to the inner tube of the condenser. Besides that the goals are the same: lowering the temperature of the input liquid/vapor. I bought this graham condenser to try.
I had a cheap submersible fountain pump pushing water through condenser tube, from output to input (opposite direction to the way the hot water will go). The coolant reservoir is about 1 gallon of normal tap water. During the tests I had to tip the condenser tube at about 45 deg angle to get the input water to flow through the tube via gravity. I had several thermometers measuring the temperature of the coolant water reservoir, the temp of the input water, and the output water. I heated the input water using a tea kettle on my stove.
Coolant water was at 62F and input water was 126F for a delta of 64F. After passing through the condenser I got an output of 87F. The temperature delta from the input to output is about 40F. The coolant water was 64F after processing the hot water, so only a 2 degree increase in the coolant.
Coolant water was at 64F and input water was 143F for a delta of 80F.
After passing through the condenser I got an output of 93F. The
temperature delta from the input to output is about 50F. The coolant
water was 68F after processing the hot water.
This time I put ice in the coolant reservoir. Coolant water was at 43F and input water was 150F for a delta of 107F.
After passing through the condenser I got an output of 91F. The
temperature delta from the input to output is about 60F. The coolant
water was 48F after processing the hot water.
Dropping 60 degrees in less than a foot with a pretty quick trip through the tube seems like a really good result! At this point the condenser is showing enough promise to keep going with the experiment. Next I'd like to tie in the vacuum pump to make it more like the final project I have in mind, and give an easier way to pull hot water through the condenser tube. As part of that I may need to put some pressure feedback in the vacuum pump line in order to tightly control how quickly the hot water flows through the tube. So I've got lots of connecting differing diameters of tubing in my future...