RIMS Exit Temp Higher than Setpoint

[jonathonhagerty]

Hi Brundog. Thanks for taking a look. You have a great website on automation, and a great reputation on this site. I automate for a living, and damn! Good job.

When I tested vertically, the probe detected the peak temperature, and the actual exit temp (sparge tube in the MT) was lower. Lower than the probe temp. Am I just fighting a losing battle here with stratification? Will some stainless wire really unify a 15F delta? It'd have to be some thick wire. Does your quadzilla's baffles have some thick fins?

Thanks, she's rockin my world. Doesn't matter how my day went, it's amazing hanging with them afterwards.

 

[BrunDog]

Hi Brundog. Thanks for taking a look. You have a great website on automation, and a great reputation on this site. I automate for a living, and damn! Good job.

When I tested vertically, the probe detected the peak temperature, and the actual exit temp (sparge tube in the MT) was lower. Lower than the probe temp. Am I just fighting a losing battle here with stratification? Will some stainless wire really unify a 15F delta? It'd have to be some thick wire. Does your quadzilla's baffles have some thick fins? I'd love to go your quadzilla route, but man this RIMS concept is giving me issues. I'm considering using my CFC as a herms coil. And using a 240V RIMS to heat the strike volume inside the MLT to the higher temp which, after doughing in, will hit thermal equilibrium at my mash temp. Just worried I'm overcomplicating this as my first e-brewing-venture. Is it overkill to use the RIMS only for raising the strike temperature to hit dough in mash-temp spot on? I know you're anti herms. I want your honest opinion. Because I want to use my CFC as a HERMS coil (just so I don't scorch anything). I plan on mashing out, but not really step mashes. With only 4gal left in the HLT, reaching 170 from 149 should be quick with 5500W and HLT recirc.

Hi. Thank you for the compliments! What you are seeing is the same phenomenon - the hot liquid is rising along the element and heating the sensor. The cooler water slides along the sides, mixes with the heated liquid, and exits ad a lower temp. The biggest issue is your oversized tube - there is just too much deadspace. Maybe at high flow it would work, but at 1 QPM, you will get lots of stratification. The key is create as much mixing / turbulence as possible. I actually tested a re circulation circuit with a pump that took most of the exit water and pumped it back into the tube again - this worked great but isn't practical.

I used to use a 5500W element in a 1.5" tube to heat sparge water on the fly. I used a relatively thick stainless wire (maybe 0.063" or so), woven in a zig-zag around the element. This helped quite a bit compared to the element alone. There is a picture on my rig's build thread - I'll try to find it. But again, downsize to a smaller tube first. I'd love or you to have a QuadZilla but I think you can honestly do what you want with your current element.

That said, the QZ has thin baffles, but it has holes in it to permit flow but mix up the flow. It has three baffles - they are movable but we suggest one in the middle, one at the 75% mark, and another at the top. They are probably overkill but there is no stratification!

I wouldn't go HERMs - but then you know I'm already biased. I think you can make your setup work. How many watts is the element?

Edit: Here is the pic: https://www.homebrewtalk.com/forum/threads/brundog-50a-erig-no-hlt-for-me.542899/page-3#post-7285005

 

[jonathonhagerty]

5500W at 240V, or 1360W at 120V

 

[Vale71]

When I tested vertically, the probe detected the peak temperature, and the actual exit temp (sparge tube in the MT) was lower. Lower than the probe temp.

Which is what you should expect since you have the wort running through quite a length of silicone tubing with no insulation. Of course this might be coumpounded by measurement errors if your hand-held thermometer and your PID probe are not in agreement, so the difference might not be actually as large. You could try putting some insulation on the output hose (while you're at it you could also insulate the other hoses as you'll have heat loss in all of them) and see by how much the temp difference decreases. Using smaller ID hoses (i.e. smaller surface area for the same lenght) and possibly shortening them would also reduce thermal loss.

 

[jonathonhagerty]

Brundog,

If I run the RIMS at higher flow, and vertically, I avoid this stratification.

I'm considering using my CFC as a herms coil for single infusion mashes. HLT would heat all water to mash temp. Then RIMS to heat the strike volume the rest of the way so dough in will hit mash temp. Would this work? I'd then switch back to the CFC to recirculate everything at one temp. Do others do this? Would it work? I have the MoreBeer copper CFC.

 

[BrunDog]

Brundog,

If I run the RIMS at higher flow, and vertically, I avoid this stratification.

I'm considering using my CFC as a herms coil for single infusion mashes. HLT would heat all water to mash temp. Then RIMS to heat the strike volume the rest of the way so dough in will hit mash temp. Would this work? I'd then switch back to the CFC to recirculate everything at one temp. Do others do this? Would it work? I have the MoreBeer copper CFC.

Yes, because there is more turbulence and mixing. 1 qpm is very slow, so lots of heat gets dumped into a small volume of liquid.

It could work but sounds awefully complex. I think I have heard of hybrid systems but I honestly dont see the benefit. I'd go all HERMs or all RIMs. I personally really enjoy the best of all worlds with a high power RIMs element - heat water at 5500W and wort at 1350W. Clean, simple, fast, and no downside IMO. Again, that 2" tube is too big though.

 

[processhead]

At the lower flow rates he is running, I can see the potential benefit of a smaller heater tube with less volume.

 

[postalbunny]

I can think of only two reasons your PID would be showing lower temp than a thermopen at the mash tun where wort is returning... there is no way the wort is actually gaining heat after it exits the tube. Your PID must not be able to grab the temp

1) You may have air pockets... if there is an air pocket over by the probe it may not be reading correctly. You may be able to fix this by tilting your setup so that the right/entrance is lower than the left/exit side. That way any air is coaxed out if it's in the middle. I'm not a fan of the probe being on the far left, you may end up with an air pocket there.

2) the wort by your probe is possibly not in the flow... air pocket or a current may be taking wort straight out and not replacing/swirling where the probe is. This is probably what you have if changing the flow rate makes everything work, and slower flows stop working.

3) Just a thought, if you're using a thermowell then the RTD may not be getting good contact. You can put some thermal paste/grease in the well that will help conduct the heat between the walls and the probe. You can verify this by yanking your RTD probe out and using your thermopen there. If the pen reads the same as the PID at the thermowell then the issue has something to-do with that thermowell and/or it's placement.

Depending on your probe length... maybe do what I've done? I put the probe where you normally have the "egress" port and put the exit for the wort on the end of the tube. I titled the whole thing and that way air flows out the exit and ensures no air pockets. My probe is just long enough to stick out into the middle of the tube and is about 1/2" away from the end of the element. Therefore i'm measuring the temp of the liquid directly at the element. This helps if there is a pump failure, the probe will detect the heat from the element and reach set-point... turning itself off and preventing scorching. (i also have a flow switch as an extra precaution)

*Mash enters left side horizontally through flow switch, entire tube is tilted slightly up, just after element is the RTD probe on the right, then the "top" of the tube on the far right has a 90deg exit back to the mash tun.

 

[augiedoggy]

View attachment 623809

Hotter wort will rise. With your tube in the horizontal position, the hotter wort leaves the tube, whilst cooler wort is near the probe. You will notice this more with slower flow rates and bigger temperature ramps, and it is significant. In the vertical position this issue is eliminated.

I dont have this issue... I have a horizontal rims with 1.5-1.8 measured flowrate. my probe is only about 1/2" from element though. its mounted in the end of the tube not out the top. I believe this is because along with the length /additional heating time, the inside diameter of my rims does not have the dead space to allow as much if any uneven heating.

I think the OP is on the right track to think a 2" tube with that short element is leaving a lot of unheated liquid past and temps just arent even at the probe area.

the element is 36" long to temps are totally even and reached by the time the liquid gets from one end to the other.

 

[BrunDog]

Augie are you saying your flow is 1.5 - 1.8 gal per min or qt per min? I’ll assume gals. At this flow rate, you are right - there is a lot of mixing and turbulence that assures heat is more evenly distributed into the liquid. Especially given your cartridge design.

Now contrast that with a very slow flow rate at 1 qpm. The liquid is moving so slowly it is not mixing and totally stratifying. This is the issue the OP had.

 

[augiedoggy]

Augie are you saying your flow is 1.5 - 1.8 gal per min or qt per min? I’ll assume gals. At this flow rate, you are right - there is a lot of mixing and turbulence that assures heat is more evenly distributed into the liquid. Especially given your cartridge design.

Now contrast that with a very slow flow rate at 1 qpm. The liquid is moving so slowly it is not mixing and totally stratifying. This is the issue the OP had.

True, I missed that important piece of info. thanks for clarifying. my flow at home is 1.5-1.8 gallons per minute.