New Giveaway - Wort Monster Conical Fermenter!

Home Brew Forums > Home Brewing Beer > Electric Brewing > RIMS Tube Heat Issue




Reply
 
LinkBack Thread Tools Display Modes
Old 03-28-2011, 02:33 PM   #1
Malintent
Feedback Score: 0 reviews
Recipes 
 
Join Date: May 2010
Location: Ceilin
Posts: 377
Liked 8 Times on 7 Posts
Likes Given: 5

Default RIMS Tube Heat Issue

Just ran my new PID-controlled RIMS HEX for the first time in production... and had a startling problem. I heated my strike and sparge water in a conventional manner (fire) to 167F. I doughed in, mixed well.. gave it a minute to settle, and then started recirculating very slowly (wild guess - about 1/4 gallon a minute). I visually confirmed the flow before firing the element. according to my PID, I was 20 degrees F low (!!!!). So at 100% power I let it ramp up. After 15 minutes, only gaining about 10 degrees F, I suspected a problem. I eased up on the output valve to increase flow just a little bit... and all hell broke loose. The PID started reading 150...155..160...165...168 (!!!!) in a matter of seconds. I immediately snapped the element cutoff switch off. The PID leveled out around 169, and then over the next 20 minutes or so cooled down to my original target of 153. The PID easily held that once I put the power to the element back on.

During my pre-production beta testing of the tube, I had run into issues with overheat, due to air getting into the system... that I fixed... and resultantly became VERY aware of the symptoms of having an exposed element / probe causing problems with boiling the liquid / steam producing / false readings. I had that resolved with reorientation and proper "burping" of the system (a gentle rocking of the tube back and forth to dislodge any air bubbles).

I have no idea how a system, with NO air in it, running at a low flow rate, can heat the wort a full 20 degrees greater than the probe (3 inches away) reads. It is not physically possible for it to have cooled that much from the element to the probe, even if the pump was completely off and I wrapped the tube in frozen towels.

I intend to install an 'economy' plastic flow meter at my RIMs outlet and determine my minimum allowable flow for this system to be accurate... but I still am baffled as to what happened... Opinions would be very helpful.



__________________
Malintent is offline
 
Reply With Quote Quick reply to this message
Old 03-28-2011, 02:55 PM   #2
Sawdustguy
Feedback Score: 1 reviews
Recipes 
 
Join Date: Mar 2009
Location: Manorville, New York
Posts: 2,758
Liked 27 Times on 25 Posts

Default

Quote:
Originally Posted by Malintent View Post
Just ran my new PID-controlled RIMS HEX for the first time in production... and had a startling problem. I heated my strike and sparge water in a conventional manner (fire) to 167F. I doughed in, mixed well.. gave it a minute to settle, and then started recirculating very slowly (wild guess - about 1/4 gallon a minute). I visually confirmed the flow before firing the element. according to my PID, I was 20 degrees F low (!!!!). So at 100% power I let it ramp up. After 15 minutes, only gaining about 10 degrees F, I suspected a problem. I eased up on the output valve to increase flow just a little bit... and all hell broke loose. The PID started reading 150...155..160...165...168 (!!!!) in a matter of seconds. I immediately snapped the element cutoff switch off. The PID leveled out around 169, and then over the next 20 minutes or so cooled down to my original target of 153. The PID easily held that once I put the power to the element back on.

During my pre-production beta testing of the tube, I had run into issues with overheat, due to air getting into the system... that I fixed... and resultantly became VERY aware of the symptoms of having an exposed element / probe causing problems with boiling the liquid / steam producing / false readings. I had that resolved with reorientation and proper "burping" of the system (a gentle rocking of the tube back and forth to dislodge any air bubbles).

I have no idea how a system, with NO air in it, running at a low flow rate, can heat the wort a full 20 degrees greater than the probe (3 inches away) reads. It is not physically possible for it to have cooled that much from the element to the probe, even if the pump was completely off and I wrapped the tube in frozen towels.

I intend to install an 'economy' plastic flow meter at my RIMs outlet and determine my minimum allowable flow for this system to be accurate... but I still am baffled as to what happened... Opinions would be very helpful.
It would be really handy to see a diagram and picture of your setup along with information on sensor location, PID parameters etc. before we even speculate. I can say something is very wrong......


__________________

Guy

Brewery URL: Black Dog Brewery NY

BBQ Team URL: Two Fat Polocks BBQ Team

Sawdustguy is offline
 
Reply With Quote Quick reply to this message
Old 03-28-2011, 03:15 PM   #3
Malintent
Feedback Score: 0 reviews
Recipes 
 
Join Date: May 2010
Location: Ceilin
Posts: 377
Liked 8 Times on 7 Posts
Likes Given: 5

Default

It is nearly identical to the "RIMS for Dummies" build: http://www.homebrewtalk.com/f51/rims-dummies-114997/

except the output tee is oriented such that both the probe and the output valve are perpendicular to the tube (as opposed to having the probe "pointing" towards the element - the liquid hits the probe side-on, and the probe is lower than the output... the output being the highest point in the system).

As for PID parameters, I will have to check at home and repost, but the problem wasn't with how the PID behaved, but with the temperature reading from the probe.

In short, at X flow rate it read the temperature 20 degrees low. at 2X flow rate it read the temperature correctly. I guess the question is, "can wort loose 20 degrees in temperature by traveling though the stainless steel tube a few inches very slowly". OR (just now thought of this) can there be "dead space" where new liquid pumped in does not mix with liquid already in the tube, that is getting hotter and hotter, and the new liquid passes over the 'old' liquid without mixing with the hotter liquid.. until I up the flow to force a mixing of the liquid (does that make sense)?

__________________
Malintent is offline
 
Reply With Quote Quick reply to this message
Old 03-28-2011, 03:42 PM   #4
Malintent
Feedback Score: 0 reviews
Recipes 
 
Join Date: May 2010
Location: Ceilin
Posts: 377
Liked 8 Times on 7 Posts
Likes Given: 5

Default

New thought....

If the rate of flow is very slow, would liquid surrounding the probe (which is lower than the tube - it points down) not mix with the heated liquid flowing through the tube... such that I am measuring relatively stagnant liquid, and my (too hot) liquid is merely passing over it and out without being measured?

Experiment:

take a length of 2" PVC pipe and cut a hole in the side, near one end. Fit and seal a small cup to the hole by its rim so it maintains a watertight seal. with the pipe horizontal, and the cup on the bottom, pass increasingly heated water through the system very slowly.

Test:

Does the water that fills the cup warm up at the same rate as the water flowing through the pipe? Does increasing the flow of water through the pipe cause the water in the cup to mix more and therefore heat at the same rate?

__________________
Malintent is offline
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options
Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Aluminum RIMS tube McCuckerson Electric Brewing 16 08-19-2011 02:39 PM
Grounding and potting a RIMS tube magnj Electric Brewing 3 02-27-2011 05:40 PM
Budget RIMS tube.. clearwaterbrewer Electric Brewing 3 02-21-2011 05:36 PM
Brewershardware RIMS tube Layne Electric Brewing 24 01-24-2011 10:48 PM
SS RIMS tube Layne Electric Brewing 54 01-05-2011 08:04 PM