Insulated SS Kettle Specific Heat

Systems, Gear, & DIY
1

I brewed on my new DIY BIAB electric system this weekend.  I set up a new equipment profile for my kettle in Beersmith 3 in order to figure out what strike temp to use, but I ended up being about 8 degrees too high after dropping in grain. I fortunately stirred to get to temp pretty quickly and gravity came out okay but it wasn’t ideal to have to mess with it at all.

My BIAB brew kettle is stainless steel, which is the value I used for the specific heat (.12) in in Beersmith.  I think the problem was I failed to correct for having insulated the outside of my kettle with a wrap of Reflectix bubble wrap insulation.

Long story short: I have the wrong specific heat value for an insulated stainless steel kettle. Does anybody have a similar setup, and if so, what value do you put in for specific heat in Beersmith?

2

Hi Koch!

I had to mess with this same issue quite a bit in Beersmith.  I have an SSBrewTech MT that is double walled SS with insulation inbetween (think yeti cup). I had to simply adjust this through trial and error, but mine came out to be .18.

There is, however a more scientific way to go about this that I learned in my chemistry class.

Weigh your vessel empty, write this down.
Fill with 2.5 gallons cold water, weigh this, subtract the difference of the vessel, this is the weight of the water ( use metric weight)… Water weighs 1g/ml or 1kg/L.

In a separate vessel, pour another 2.5gallons and record it’s weight as well.  Begin heating this water to 80*C. (Being accurate with all measurements is important).

Meanwhile, place an accurate (to .01*C) thermometer in your kettle and record it’s temperature.  Record the initial temperature of water, stir gently, record a temp reading every minute for 4 minutes.  On the fifth minute it should have balanced out.

When your hot water is ready, pour it into the cold water and watch your thermometer.  Stir, cover, record temp quickly.

Record temp every 30 sec for 5 minutes.

In Excel or another spreadsheet program, enter the time as your x-value and temp as your y-value and create a graph.  Use the best fit option for a line overlay.  This is only the data from the time you added your hot water to the calorimeter (kettle in your case).

Take the final temperature (temp at time 5mins) and subtract the initial temp from the final temp.  Multiply this number by the mass of the cold water and 4.184 to find the amount of energy gained by the cold water in Joules.

Finally subtract the energy gained by the cold water from the energy lost by the hot water, this is the energy absorbed by the calorimeter (kettle) then divide the energy gained by the kettle by the change in temperature, this is the calorimeter constant for your kettle that you will use in BeerSmith.

Hope this helps, I had to refresh myself on this myself, here’s a website that I got the info from.

3

The simple way is to ignore that value.  If you fill the kettle with strike water that’s about 10 degrees hotter than your strike temp (with no specific heat), you only have to wait (and maybe stir) until the temp comes down to what you need then mash in the grain.

4

Thanks Brewtopalonian! I recalled some of that from high school chemistry but thanks for the detail, plus your own calculated value.

Hokerer, I am able to hit my set strike temperature fine (Clawhammer controller is pretty nifty) easily; the problem is that adding the grain didn’t result in as low of a mash temperature as I estimated it would.

5

Oh, you’re using Clawhammer?! Nice! I’ve been wanting to try that system.  I think I wouldn’t even worry about it then!  I would just put my grains in at the set mash temp and let it rise.  Shouldn’t take but a couple minutes if that.

6

Iiiinteresting. I hadn’t thought of that. Not that my technique thus far in my homebrewing has been uber-precise, but is there any risk of under/over-doing the fermentables if the mash spends a few minutes at lower temp like in that scenario? Most of the time I aim for light or medium body, but just curious. That certainly sounds easier!!!

7

When heating water in an electric BIAB system, the thermal mass of your kettle doesn’t matter when determining the strike temperature. In BeerSmith, un-check the box on the mash tab that says “Adjust Temp for Equip”. If you are putting hot water into a cold kettle you need to know how much heat the kettle will absorb as the kettle and water equalize their temperatures. If you are heating the water in your kettle then the kettle will be the same temperature as the water so it doesn’t matter. You just need to know your water volume, grain weight and grain temperature to calculate the strike temperature. Just give your system a few minutes at strike temperature with well-stirred water before adding the grains and everything should be fine.

In my electric BIAB system the difference between strike temperature and mash temperature is only about 6 degrees, so just setting to the mash temperature would result in mashing about 6 degrees too low for a few minutes. If  you are looking for a light-bodied, highly fermentable wort then there is no problem with doing this (and I do it on purpose sometimes). If you want a higher-bodied beer with a higher mash temperature then you probably want to start with strike temperature higher than the mash temperature.

8

Thanks for the confirmation and clarification, Richard. That makes perfect sense.

9

Custom equipment profiles are a must. Guesses won’t cut it. You will need to take actual measurements to determine all of your losses. Here are a couple of tutorials to show you what you need and how to do it.

10

Another thought is to just get a hold of the guys at Clawhammer and ask them to send you their equipment profile.  If you watch their YouTube videos you’ll see that they use BeerSmith, so I’d assume they also have an equipment profile already built.

11

To clarify, I bought the brewing controller and heating element (110v), but i installed it on my old Brewmaster 8 gallon kettle.

I gotta tell yah, drilling the small hole for the 1/2 inch bulkheads for the ball valve and thermowell with a step bit was pretty care-free, but I was terrified using a hole saw to drill the 40mm hole for the 1.5 inch tri-clamp port (the Clawhammer element comes with a 1.5 inch triclamp attachment). The hole came out pretty ugly, but after deburring it, the weldless ferrule sealed fine.

I went to my LHBS to get some silicone tubing and pick up some of their brew (they brew and have taproom onsite), and told the owner about my ordeal. He told me he has a step bit big enough for the triclamp port and he’d have done it for free! That’s what I get for being skittish about not being every piece of equipment from them.

12

But no one uses the same equipment in the same way even on identical systems. It doesn’t take a lot of work and it’s worth it to have a fully customized profile.

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“Relax, don’t worry, have a Homebrew!”