DIY tankless water heater for sparge water

[greengt]

My mind started thinking about this a week or so ago, do any of you have this set up? Comments?


So the idea is to basically take my HLT heating element and stick it in a SS tube which has an IN and an OUT (same as a DIY rims tube). Like said same as rims tube but without the recirulation, city water in and correct sparge water temp out.

The PID to control the output temp would have to be precise and fast....or i could try it with a manual control...

Like I mentionned above this is just a tough for now, but id like to see what you guys think. Is it possible? Any forseeable pitfalls?

 

[BrunDog]

It's a great idea!

 

[highland_brewer]

I think Bobby from Brewhardware did a video on this very thing once upon a time, In the video he was switching between 120 and 240v for the "on demand" sparge water. I'll see if I can locate it.

 

[BrunDog]

In my brew video at 5:40, the relay to switch the high/low power to the RIMS tube is shown.

https://youtu.be/bxUSwpv2H-s?t=5m40s

 

[thekraken]

I think Bobby from Brewhardware did a video on this very thing once upon a time, In the video he was switching between 120 and 240v for the "on demand" sparge water. I'll see if I can locate it.

Here ya go:
[ame]https://www.youtube.com/watch?v=0AGUOCeM-WU[/ame]

 

[augiedoggy]

Keep in mind, in order for it to heat the water in one pass like a tankless water heater you need a large amount of heated surface area (a big heat exchanger) or a very low flow rate.. Brundog how are you accomplishing this in your setup?

 

[thekraken]

In Bobby's video he used what I think is a standard 5500 watt ulwd water heater element in a RIMS tube and was getting a temp delta of 130F in one pass at a flow rate of a little more than 1 liter per minute. At one point he gets boiling in his RIMS tube but I'm not sure if he slowed down the flow rate or not.

 

[BrunDog]

I also use a 5500W straight foldback in a RIMS tube. I have done a lot of testing with this arrangement. First, it MUST be vertical. At slow flow (~1 qt/min), I got too much local boiling yet not enough net temperature rise in a horizontal or diagonal arrangement. This seems backwards, but it happened. I can only guess that the heated water rises up off the element and slowly runs along the tube at the top edge, so the heat gets concentrated. I tried some different baffles to create turbulent flow, but they often captured stray grain causing clogging. The best result has been intertwining the element with stainless wire - this helps pull some of the heat off the element and disrupts the liquid's laminar flow.

THere was another thread recently which discussed thermal wire wrapping, and I suggested a good design would be 4x 1500W cartridge heaters in a 2" TC tube - that would be lots of surface area and minimal volume. I haven't pursued this yet because my solution works well, but this might be better.

Also, the OP suggested PID. There is no point using PID, and I have learned this the hard way. Because the incoming water temp and flow rate through the tube is held constant, duty cycle (PWM or manual mode) works best for sparge temp consistency. PID can work but tends to get unstable given the sensing delay. If the flow rate varies even the slightest, it goes unstable. Because sparge temperature is not critical, I don't sweat it and let the temp be in the range 165 - 175. With ambient water ~80 degrees, 1.1 q/m flowrate, a ~60% duty is enough, which tells me there is a bit of headroom for cooler water. My old system automated flow rate, and my new one automates both flow rate and and temperature adjustment, but these can be accomplished in a manual system just as easily. The harder part of fly sparging is emptying the MLT at the same rate as filling it.

 

[TexasWine]

At slow flow (~1 qt/min), I got too much local boiling yet not enough net temperature rise in a horizontal or diagonal arrangement. This seems backwards, but it happened.

You're probably experiencing film boiling. Increasing the Reynolds number with your stainless wire will definitely help.

View attachment 1491418374270.jpg

 

[BrunDog]

I don't think so - the element would have to be wicked hot for that. Anyway, no matter, because it works perfectly with a vertical orientation.

 

[Bobby_M]

The biggest pitfall with the plan is not really if you can build the hardware to do it but rather the fact that there is no way to treat the incoming water if necessary. At the very least you would want to get rid of the chlorine. At sparge rates, you'd want to run through at least two 10" carbon filters before the heat source. The Auber EZ boil set in mash mode would be a great way to set the output temp once you establish your desired flow rate. You could also set a high temp alarm at like 175 just in case it starts to run away.

 

[BrunDog]

^This is true. That said, because I use RO water which I take from my undersink RO filter, I store it in two 5 gallon tanks. I used to treat that water by putting the salts in it, but I have since changed to using straight RO into my mash tun, adding all the salts there (making sure the pH is ok), then sparging with just the RO water. Martin says this is OK and his sheet allows for it, so that's what I do!

 

[Choti]

I am currently working on such a project. And I'm very interested in your posts and advice. Thank you. Only me watering the process of cleaning my apparatus, you can use the method of cleaning the water heater, for example in this way? Have you thought about this?
What are your suggestions and methods?

 

[BrunDog]

I would not pursue a tankless heater unless you acquired one at little to no cost. I have an experiment coming up with a new style RIMs tube. This should allow anyone to direct sparge safely and have very low watt density in the process.

 

[augiedoggy]

I would not pursue a tankless heater unless you acquired one at little to no cost. I have an experiment coming up with a new style RIMs tube. This should allow anyone to direct sparge safely and have very low watt density in the process.

This is somewhat related to the discussion so I'll throw it in here..
I may have mentioned this elsewhere but as many know I use a very ultra low watt density cartridge rims tube setup and on my last three brew sessions I experimented by slowing the sparge rate way down when I fly sparge vs what I was doing when I sparged at about 1-1.2 gallon per minute achieving 86% average efficiency...
The results at the slower sparge rate where 88.3%, 88.7% and on the last brew (a schwarzbier) I got over 91% efficiency.(also used a new sack of avanguard pils for the last one vs an older sack of the same stuff being the base for the others).. This beer has just hit the estimated final gravity and is going to be kegged this week. This proves to me that there can be additional efficiencies gained by sparging slower even after recirculating during the entire mash period. I dont know if channeling was still occuring at some rate or if its just the additional contact time but even with 170 degree sparge water my efficiency does go up.
I should add that I currently dont use my rims to heat sparge water but at a low flow rate such as im using (about .3-.4 gallons per minute)any rims would work.

 

[BrunDog]

Thanks @augiedoggy. Just for reference, I sparge at about 1.1 qpm but I don't get those efficiency levels, so perhaps it is my vessel/FB design. I think your braided pickup under the FB makes for efficiency gains as there is not a single point of draining under the FB.

Also, for reference, my system set the 5500W element to about 68% power when heating sparge water at this rate from ambient (~80 deg F) to sparge temp (~168 deg F), so I don't think that an element < 3000W will work. That said, I am working on a solution based upon your cartridge heater implementation. Stay tuned...

 

[processhead]

With these systems you guys are building, I am curious how long it takes for the temperature to stabilize at the desired level prior to starting the sparge?

What, if any, flow diversion takes place prior to directing flow over the grain bed?

 

[BrunDog]

Good question @processhead. I employ empiric values at the start, which are based on the normal stable values historically reached. My system tunes the flowrate and sparge temp as the sparge occurs. Obviously changing one also affects the other, so I have found the best way is to monitor the flow rate. If it is outside the window, it is adjusted via the proportional valve. If it is within the window, the temperature is then checked and adjusted if needed.

The initial water out of the RIMS tube is ambient, but it probably takes <20 seconds before appropriate flow and temp is reached. I don't divert this water, as my strong belief is a little bit of colder water will not make any significant impact. Tests have been done with cold water sparging and found little to now impact other than slightly reduced efficiency. High temps > 170 should be avoided of course.