Raising Temperature with RIMS

[Diggy]

I recently built a new electric brewing system with RIMS. One of the reasons for this is to do step mashing. On Sunday I did my first brew with it and the step mashing took way too long (18 min to get from 144 to 153).

What I did:
• Used a 240v 4500w Element in RIMS tube set to 240v (I put it on a switch so I can run it at 240v or 120v). I had no scorching at all.
• Had a temp probe in the mash and at the end of the RIMS tube
• I set the RIMS tube to 2 degrees higher than the desired Mash Temp and the RIMS heating element set on PID mode based upon the RIMS tube temp probe.
• I had the wort being pumped at 0.5 gal / min (I have a rotameter on my pump)

I just did the math and it simply does take 18 min to change 6 gallons of water from 144F to 153F when heating 0.5 gals/min to 155F. Therefore, if I want to try and raise the temp faster I need to either speed up the pump or increase the temp of the RIMS tube even higher than the mash.

Questions:
• How fast do you recirculate your wort in the mash?
• What temp do you set your RIMS tube when trying to change the MASH temp? I could set the RIMS tube all the way up to near boiling and it will change the MASH temp faster but I feel it would probably denature the enzymes.

 

[golfindia]

If you are using a PID, and you increase the set temperature, the PID is going to run wide open until the measured temp is equal to the set temp. It doesn't matter if you your set temp is 400 degrees, if your measured temp is lower the output of your element is going to be the same (100%). I do 10 gal step mashes frequently with my RIMS tube (1650w 120v). I just split the required rise time between the two mash steps that are on either side. Has worked fine so far.

Pump speed is a tougher one. I try to crank it up as high as I can without getting a stuck mash so that wort didn't get scorched during steps. Lots of corn/rice requires turning for down to almost a trickle. The most important thing is to keep the flow rate constant throughout the mash. Slowing and speeding it up makes the PID go berserk.

 

[Diggy]

If you are using a PID, and you increase the set temperature, the PID is going to run wide open until the measured temp is equal to the set temp. It doesn't matter if you your set temp is 400 degrees, if your measured temp is lower the output of your element is going to be the same (100%). I do 10 gal step mashes frequently with my RIMS tube (1650w 120v). I just split the required rise time between the two mash steps that are on either side. Has worked fine so far.

On my brew on Sunday the element was not on very much because the PID was tightly controlling them temp at the end of the RIMS tube to be only 2 degrees hotter then the desired Mash Tun temp. The element could easily heated the Mash Tun faster if I left it on 100%. However I was worried that going hotter then that would start denaturing the enzymes (Are the enzymes floating around in the wort or do they remain in the grain?).

Are you saying that you run your element at 100% until the Mash Tun is at the correct temperature and do not worry about the temp inside the RIMS tube?

Pump speed is a tougher one. I try to crank it up as high as I can without getting a stuck mash so that wort didn't get scorched during steps. Lots of corn/rice requires turning for down to almost a trickle. The most important thing is to keep the flow rate constant throughout the mash. Slowing and speeding it up makes the PID go berserk.

Reading through a lot of old posts today it sounds like people are pumping their mash a lot faster then I was.

 

[dyqik]

To raise the temperature of the whole grain bed uniformly, you need to recirculate all the fluid through it at least once, more like twice if you only set the incoming fluid temperature to close to the target temperature. You simply don't get much mixing of the returning wort with the cooler wort deeper in the mash, so you need to move all the fluid through the bed and tube at least once. Since you also have to raise the temperature of the grain and vessel, it'll take more than one pass.

Pump speed is critical - I can raise my mash from 152 to 168f mash out in about 10 minutes with a 1500W element for a 4 gal mash for a 6gal batch

 

[golfindia]

If your mash is 140, and you set your PID to 155, your PID will turn on your element full blast (100%) until you get close to 155. The temp inside the rims tube will be whatever your RIMS probe says it is. It cannot be hotter in it RIMS tube than what your set temp is. If it was, your PID would turn the element off.

I still prefer to mash in an igloo cooler, it is much easier to step mash with less heat loss. I always get the recirculation going good before I turn on the rims. It takes a while for the mash temp to even out. If I turn on the RIMS at the same time as the pump, the PID has a tough time chasing the temp swings.

 

[Diggy]

If your mash is 140, and you set your PID to 155, your PID will turn on your element full blast (100%) until you get close to 155. The temp inside the rims tube will be whatever your RIMS probe says it is. It cannot be hotter in it RIMS tube than what your set temp is. If it was, your PID would turn the element off.

I must not be explaining myself very well. I totally understand what the RIMS and PID controllers are doing to control the mash temp, what I do not understand is how the temp in the RIMS tube affects the enzymes that convert the mash.

I want to figure out how hot I can run the RIMS tube while trying to change the average mash temperature before I denature the enzymes.

 

[wilserbrewer]

I want to figure out how hot I can run the RIMS tube while trying to change the average mash temperature before I denature the enzymes.

I believe the denaturing of the enzymes is both time and temperature dependent, and the short time spent in the rims heater above desired mash temp will likely not be substantially detrimental to enzymes.

Exactly how hot you can go I have no idea....

 

[golfindia]

I want to figure out how hot I can run the RIMS tube while trying to change the average mash temperature before I denature the enzymes.

You are either heating wort flowing past the element (element is on) or you arent (element off). You cannot control the "temperature of the RIMS tube". As long as liquid is flowing past the element at all times you will not have issues.

 

[Diggy]

I believe the denaturing of the enzymes is both time and temperature dependent, and the short time spent in the rims heater above desired mash temp will likely not be substantially detrimental to enzymes.

Exactly how hot you can go I have no idea....

Thanks Wilserbrewer, that was my general feeling as well but had nothing to substantiate it with.

It looks like I will have to run a few tests, bumping up the flow rate and then raise the temp of the RIMS PID with each successive batch until I notice an impact on the beer.

 

[wilserbrewer]

.... until I notice an impact on the beer.

You may never get there

Hoping you don't have enough power to denature enough of the enzymes to even make a noticeable difference.

This may be one of those things that in theory is concerning....but in actual practice doesn't actually happen. Sometimes we all can be guilty of thinking too much lol cheers!

 

[BrunDog]

I have quite a bit of experience here, as I also switch my RIMS between 5500W and 1350W... I don't think the 18 minutes is that big a deal (other than time efficiency). If you are doing step mashes, they will take time to conduct the steps. Now, I do not ever mash at 5500W - I think you are possibly asking for trouble with proteins burning or caramelization/scorching at too slow a flow rate.

That said, I feel that 0.5 gal/min is too slow a recirc rate. At that slow rate, the wort in the RIMS will heat up and turn off the element, thereby reducing heat input into the whole system. You want to get your flowrate as fast as possible without causing a stuck mash. With a higher flowrate, the element is never off that much, because it is getting the heat pulled out of it more rapidly.

In my experience, doing ~1050 beers in a 15 gal MLT with ~4.5gal water, I can flow about 5 qts/min initially increasing to ~8-10 qts/min once the mash is well underway. That's 1.25 - 2.5 gals / min.

Now, one of the caveats of RIMS tubes is the high centralization of heat around the element. The liquid around the element is not rapidly mixed, which would cause better heat transfer. Instead you get very hot liquid by the element and very cool at the surface of the tube. I wrapped my element in single conductor stainless steel wire to promote turbulence and heat transfer, and I believe it helps. Someday someone will produce an effective super ultra low watt density element that also has high wattage. A coiled element like the RIMS rocket from Blichmann would be great, but with at least 5-6k of power.

Hope that helps!

 

[Diggy]

You may never get there

Hoping you don't have enough power to denature enough of the enzymes to even make a noticeable difference.

This may be one of those things that in theory is concerning....but in actual practice doesn't actually happen. Sometimes we all can be guilty of thinking too much lol cheers!

I totally agree with you, especially with the modern highly modified malts with lots of diastatic power.

To be honest, I was simply hoping someone using RIMS was just going to say that.

 

[Diggy]

Thanks BrunDog!

I have quite a bit of experience here, as I also switch my RIMS between 5500W and 1350W... I don't think the 18 minutes is that big a deal (other than time efficiency). If you are doing step mashes, they will take time to conduct the steps. Now, I do not ever mash at 5500W - I think you are possibly asking for trouble with proteins burning or caramelization/scorching at too slow a flow rate.

Do you keep it at 1350W while trying to step up the Mash temp or just when you are holding the temperature steady? I was debating about this while making my system. It takes me very little power to keep the temp steady.

During a step, are you controlling the temp of the wort flowing through the RIMS tube with a PID? If so what is the highest temp you let it get to while trying to step up the mash temp?

That said, I feel that 0.5 gal/min is too slow a recirc rate. At that slow rate, the wort in the RIMS will heat up and turn off the element, thereby reducing heat input into the whole system. You want to get your flowrate as fast as possible without causing a stuck mash. With a higher flowrate, the element is never off that much, because it is getting the heat pulled out of it more rapidly.

In my experience, doing ~1050 beers in a 15 gal MLT with ~4.5gal water, I can flow about 5 qts/min initially increasing to ~8-10 qts/min once the mash is well underway. That's 1.25 - 2.5 gals / min.

This is perfect! Simply increasing my recirc rate will shorten the time between steps a lot.

Without crossing the line and getting a stuck mash it is hard to know where that line is so I can have my flow rate as fast as possible. Knowing what you are doing gives me a good ballpark of where I can test and shoot for. Thanks!

Now, one of the caveats of RIMS tubes is the high centralization of heat around the element. The liquid around the element is not rapidly mixed, which would cause better heat transfer. Instead you get very hot liquid by the element and very cool at the surface of the tube. I wrapped my element in single conductor stainless steel wire to promote turbulence and heat transfer, and I believe it helps. Someday someone will produce an effective super ultra low watt density element that also has high wattage. A coiled element like the RIMS rocket from Blichmann would be great, but with at least 5-6k of power.

Hope that helps!

This is a big help, thanks for the advice!

 

[TexasWine]

Without crossing the line and getting a stuck mash it is hard to know where that line is so I can have my flow rate as fast as possible. Knowing what you are doing gives me a good ballpark of where I can test and shoot for. Thanks!

This is a big help, thanks for the advice!

If you have a sight glass, just watch it. If the level starts to fall to much, throttle back your pump.

This is really the only reason I have a sight glass in my system.

 

[BrunDog]

I keep the power at 1350 anytime the mash steps are occurring. I use the high power for strike water heating and mashout. Yes it takes some time but the steps do happen. I suppose with a fast enough flow you could step on high power. Just keep the PID following the RIMs tube temp sensors to one or two degrees above your desired step temp.

 

[rudylyon57]

I have quite a bit of experience here, as I also switch my RIMS between 5500W and 1350W... I don't think the 18 minutes is that big a deal (other than time efficiency). If you are doing step mashes, they will take time to conduct the steps. Now, I do not ever mash at 5500W - I think you are possibly asking for trouble with proteins burning or caramelization/scorching at too slow a flow rate.

That said, I feel that 0.5 gal/min is too slow a recirc rate. At that slow rate, the wort in the RIMS will heat up and turn off the element, thereby reducing heat input into the whole system. You want to get your flowrate as fast as possible without causing a stuck mash. With a higher flowrate, the element is never off that much, because it is getting the heat pulled out of it more rapidly.

In my experience, doing ~1050 beers in a 15 gal MLT with ~4.5gal water, I can flow about 5 qts/min initially increasing to ~8-10 qts/min once the mash is well underway. That's 1.25 - 2.5 gals / min.

Now, one of the caveats of RIMS tubes is the high centralization of heat around the element. The liquid around the element is not rapidly mixed, which would cause better heat transfer. Instead you get very hot liquid by the element and very cool at the surface of the tube. I wrapped my element in single conductor stainless steel wire to promote turbulence and heat transfer, and I believe it helps. Someday someone will produce an effective super ultra low watt density element that also has high wattage. A coiled element like the RIMS rocket from Blichmann would be great, but with at least 5-6k of power.

Hope that helps!

+1 on all your comments Brundog. I have contemplated replacing my PID controlled SSR with an SSVR to provide finer control between full 240V and 120V operation to bridge the 4:1 power difference. Not quite sure how that would work along with the PID though. I performed some CFD work to understand the flow and heating of wort through a typical RIMS tube. It is in fact a non-ideal situation with the flow generally moving parallel to the heater. As you suggested, introducing turbulence or using a tangential inlet (to create swirl) may help.

 

[BrunDog]

First, I think incorporating the SSVR would be tricky. With a dumb enough and properly tuned response, a standard PID can vary the power from top to bottom via duty cycle. If you want to go high/low like I did, use a big enough relay to switch one hot let with neutral going to one side of the element.

Second, HOW FRIGGIN COOL is that fluid dynamic plot!?! That is awesome and if it weren't really awkward, I'd hug you!

My initial tests doing rapid heating for on demand sparge water heating showed local boiling in the tube really easily when the tube was mounted horizontally but went away when mounted vertically. This leads me to believe vertical is better for all applications but I can't guarantee that. Your plot shows how the warmed fluid rises and hot pockets (zones) get created.

Any chance you could do the model vertically? And with varying heat inputs (say 1500W and 5000W)?

 

[BrunDog]

Here is the post where I added the wire and discussed my flow concerns:

https://www.homebrewtalk.com/showpost.php?p=7285005&postcount=88

 

[WI_Wino]

X2 on the awesome plot. Auggiedoggy has a really long cartridge heater, I wonder how that would model out. I would guess the hot spots would be reduced as you have a longer tube and lower watt density. But that's why we model.

 

[BrunDog]

Yes his design is good due to length and small liquid cavity inside tube. It would not work for my purposes personally but it's a good design.

 

[rudylyon57]

My (okay my employers) CFD software does not have the guts to model nucleate, film or multi-phase regimes of heat transfer. Brundog...I think the onset of localized boiling is where your observation of a vertical mounting being better stems from. The bubbles of vapor are more likely to rise and separate, improving heat transfer, from the hot surface than if horizontal...just a guess.

 

[Diggy]

That plot is awesome!

 

[BrunDog]

My (okay my employers) CFD software does not have the guts to model nucleate, film or multi-phase regimes of heat transfer. Brundog...I think the onset of localized boiling is where your observation of a vertical mounting being better stems from. The bubbles of vapor are more likely to rise and separate, improving heat transfer, from the hot surface than if horizontal...just a guess.

You tease!! Haha that's cool, no problem.

My initial testing was vertical and I could heat ~75 - 170 in one pass at almost 1.4 qts/min without local boiling at 5500W. When I mounted it horizontally on my rig, all hell broke loose and I was boiling with little to no effort.

 

[wilserbrewer]

all hell broke loose.

I like how the discussion went from exact figures to "all hell broke loose" lol

No data available...

Might the bubbles rise and condense again in the vertical position while in a horizontal position you have a miniature pressure cooker on your hands...

 

[BrunDog]

Yep, gotta keep some drama in the mix!

 

[wilserbrewer]

Lol rims tube turns into a steam generator.