Author Topic: Mash tun volume and strike temps  (Read 3893 times)

Offline kbonura

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Mash tun volume and strike temps
« on: January 22, 2018, 07:07:11 AM »
I posted recently regarding a discrepancy between strike temps between the PC and mobile app. (despite exactly the same profiles, the mobile app wanted me to strike much hotter than the PC version).
I played around with equipment profiles and noted that if I was to change the profile and use a smaller volume mash tun the required strike water temp was actually higher than if I used a larger volume tun. Only variables changed were the tun volume and weight (both cut in half).
I would think the larger tun would require the hotter strike temp & vice versa.
Can anyone offer any suggestions as to why this might be the case? this might help solve my problem of mobile vs pc discrepancy.

Thanks!

Offline jtoots

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Re: Mash tun volume and strike temps
« Reply #1 on: January 22, 2018, 09:49:19 AM »
Here's my hunch:
You have less water, so to get the mass of grains up to a given temp it needs to be hotter.  There's more thermal mass in a larger amount of water, so the temp doesn't need to be as high.

Offline kbonura

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Re: Mash tun volume and strike temps
« Reply #2 on: January 22, 2018, 11:24:11 AM »

The only change is the volume and weight of the tun. grain weight to water ratio is the same for both.

Offline Oginme

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Re: Mash tun volume and strike temps
« Reply #3 on: January 22, 2018, 11:43:01 AM »
If you are changing the weight of the mash tun, the strike temperature WILL change when you have the 'adjust temp for equip' option checked.  The units for specific heat (in BeerSmith terms) are cal/g-degC, where the weight in grams determines the mass of the mash tun which needs to be raised from the starting temperature up to the mash temperature.  If you change the volume of the mash tun independently of the weight, the strike temperature does not change (at least in my version it didn't), so the volume has no bearing on the amount of heat needed, only the weight.

Recycle your grains, feed them to a goat!

Offline kbonura

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Re: Mash tun volume and strike temps
« Reply #4 on: January 22, 2018, 12:02:46 PM »
but why when the weight decreases does the necessary temperature increase? shouldn't it it be less heat required for less weight? regardless of the volume of the tun, i will still be using (arbitrary number) 2.5gal strike water.
« Last Edit: January 22, 2018, 12:04:22 PM by kbonura »

Offline Oginme

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Re: Mash tun volume and strike temps
« Reply #5 on: January 22, 2018, 12:52:25 PM »
That is one thing that I am not seeing.  As I double the weight, the temperature goes up accordingly.  If I halve the weigh, the temperature decreases accordingly.

So I started with a 3.81 kg kettle at 65?F and had a strike temp of 162.8?F;
I doubled the weight to 7.62 and the strike temperature increased to 165.4?F;
I halved the original weight to 1.9 kg and the strike temperature wend down to 161.6?F.

Your mobile vs PC discrepancy aside, the desktop version seems to be acting as it should.

Recycle your grains, feed them to a goat!

Offline kbonura

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Re: Mash tun volume and strike temps
« Reply #6 on: January 22, 2018, 12:57:35 PM »
I'll have to send some screen shots tonight. There's gotta be something I'm brain farting on.

Offline kbonura

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Re: Mash tun volume and strike temps
« Reply #7 on: January 22, 2018, 05:26:25 PM »
That is one thing that I am not seeing.  As I double the weight, the temperature goes up accordingly.  If I halve the weigh, the temperature decreases accordingly.

So I started with a 3.81 kg kettle at 65?F and had a strike temp of 162.8?F;
I doubled the weight to 7.62 and the strike temperature increased to 165.4?F;
I halved the original weight to 1.9 kg and the strike temperature wend down to 161.6?F.

Your mobile vs PC discrepancy aside, the desktop version seems to be acting as it should.


Offline kbonura

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Re: Mash tun volume and strike temps
« Reply #8 on: January 22, 2018, 05:35:35 PM »
I found it...I'm a jedi dumbass... the specific heat was backwards in the test. it was 0.21 instead of 0.12 for stainless.
sorry for wasting your time guys.

Offline GigaFemto

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Re: Mash tun volume and strike temps
« Reply #9 on: January 22, 2018, 05:39:31 PM »
I just noticed that and was composing a reply when the forum told me that there had been a new reply since I started composing! Glad you found it.

--GF

Offline kbonura

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Re: Mash tun volume and strike temps
« Reply #10 on: January 23, 2018, 06:43:11 AM »
whats even weirder now is that the mobile vs pc discrepancy doesn't seem to be happening anymore (even with the old and initially correct specific heat). Ah well, not gonna question it.
thanks again for the advice.