Calculating Temperature Change

[ColdBeerLuke]

Back in the days of high school chemistry and slide rules, we were taught a formula for calculating how long temperature changes take to occur. For example, how long it takes 23 litres of water at 50C to come down to 20C in air at 10C.
I thought it was related to specific heat of the two substances, but I'm buggered if I can remember it, or find anything in my old high school parchments.
Does anyone remember chemistry/physics/whatever well enough to steer me towards working this out?

 

[sosman]

Search "specific heat" or "thermal mass" on google

You have to find out how much energy it takes to raise a certain mass a certain temperature. Eg kJ/C/kg.

To get that in terms of time, you need to work out the power output of your heat source minus the losses. Gas burners are often stated in terms of MJ/hour.

 

[Tim]

energyin KJ = mass x heat constant x change in heat
is this the formula you are thinking of??

If you wanted to use this sort of thing you would have to calibrate the heat constant of your mash tun and adjust from the heat constant of wort. the heat constant of water is 4.12 or something similar (cant remember of the top of my head!).

I have all the data on this sort of stuff as im a chemist (well organic chemist anyway)

 

[ColdBeerLuke]

Good memory Tim. It's actually 4.18, but I'll pay that off the top of your head. And yes, your formula is exactly what I had in mind. Thanks.
Thanks sosman. I searched "specific heat" before, but "thermal mass" narrowed the search.
I am now doing a complete revision of high school chemistry and physics. If I ever understand it completely, I'll post the results here. :unsure: :blink: