Author Topic: Help Understanding The Strike Water Temp Calculation  (Read 1270 times)

Offline mdeaves

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Help Understanding The Strike Water Temp Calculation
« on: May 28, 2020, 04:54:08 PM »
I'm trying to understand a little bit more about how BeerSmith calculates the strike temp. I have a simple grain bill of 5,808 g. In the advanced options I have malt specific heat set to 0.38 cal/g*C, my strike water mass is 15,140 g, and my target mash temp is 64.44 C. My grains and mash tun are at 20 C before mashing. Water has a specific heat of 1 Cal/g*C. My mash tun weight is 5,000 g and has a heat capacity of 0.3 Cal/g*C.

If I un-check 'Adjust Temp For Equip' it gives me a strike temp of 70.92 C, which is easy to verify as,

64.44 + (64.44 - 20) * 0.38 * 5,808 / (15,140 * 1) = 70.92

So far so good. Now my understanding is that selecting the 'Adjust Temp For Equip' check box will increase the strike temp in order to provide enough thermal energy to heat the mash tun from 20 C to 64.44 C, so our strike temp should be,

64.44 + [(64.44 - 20) * 0.38 * 5,808 + (64.44 - 20) * 0.3 * 5000]/ (15,140 * 1) = 75.32 C

However BeerSmith gives me 73.42 C. What am I missing?

The interesting thing is if I use the infusion tool instead it gives me the correct temp of 75.32 C

Are these two calculations supposed to be different? Is there another setting somewhere I am missing?

Offline Oginme

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Re: Help Understanding The Strike Water Temp Calculation
« Reply #1 on: May 28, 2020, 05:20:24 PM »
I have now tried this with three recipes, comparing the infusion tool to the recipe with the 'adjust temp for equip' turned on.  I get the same results from the infusion tool as from the recipe each time.

Not sure what is going on with your copy, but I cannot replicate it with mine.

Maybe do a screen shot of the infusion tool versus the mash tab of the recipe, include your equipment profile and I'll see if there is something I can pick out between them.

Recycle your grains, feed them to a goat!

Offline mdeaves

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Re: Help Understanding The Strike Water Temp Calculation
« Reply #2 on: May 28, 2020, 05:28:59 PM »
Thanks for the super quick response!

I've attached the infusion tool, my mash tab of my recipe, and the equipment profile.









Offline GigaFemto

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Re: Help Understanding The Strike Water Temp Calculation
« Reply #3 on: May 28, 2020, 07:45:01 PM »
It is possible that BeerSmith is considering how much of the mash tun needs to be heated. In the infusion tool there is no reference to the mash tun volume, so it assumes the entire tun mass is raised to the strike temperature. In the mash tab it knows that only half of the mash tun will be used, so only part of the mass needs to be heated to the strike temperature. In order to do this accurately BeerSmith would need to know mash tun dimensions, bottom thickness, etc. but one could do a reasonable guess since most mash tuns have similar geometry. I don't know for sure that this is what is going on, but it is a guess that fits the data.

--GF

Offline mdeaves

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Re: Help Understanding The Strike Water Temp Calculation
« Reply #4 on: May 29, 2020, 06:20:38 AM »
That's it!

If I change my equipment profile so that my mash tun is 5 gallons in size (my needed mash volume), the infusion tool and the mash tab on my recipe both give 75.32 C.

It's a weird way to make that calculation though isn't it? My mash tun is a cooler with a lid so it's going to absorb the same amount of heat regardless of the size of my mash.

Offline Oginme

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Re: Help Understanding The Strike Water Temp Calculation
« Reply #5 on: May 29, 2020, 06:55:10 AM »
Good job, GF!

From my experience when I was using a cooler mash tun, I adjusted the specific heat in my equipment profile using actual measurements and did not run into any issues with getting very good strike temperature targets from the program.
Recycle your grains, feed them to a goat!

 

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