Why either 77kw or 28kw power can boil similar volume kettle
Recently, I just discussed with one client about the heating power for his 1500L brewery kettle. They are currently use a only 28kw heating power to boil 1200L batch wort and it works good. However, our standard heating elements for 1500L volume is around 77kw.
So we together exchanged the calculation and operation details, and do find some interesting thing.
How we calculate our electric heating power for 1500L kettle: We calculate the power mainly according to the Heat exchange principle.
Our calculation is to heat up the mash/wort with a speed of 1-1.5℃ per minute.
To heat up the 1500L wort from 78℃ to 100℃, it needs estimated energy of around: 1500Lx4200J/kg.℃x22℃=1.386x10^8 J=38.5KW.h
If we assume to heat up the wort from 78℃ to boiling temperature within around 0.5hr (heat up 0.7℃ per minute, slower than 1-1.5℃ as we want to minimum the heating power), then the heating elements power will be finally around:
38.5KW.h/ 0.5hr=77kw
We standardly mount the elements inside the 1500Lkettle in this way:
9kwx6pcs+ 8.3kwx4pcs=87.2kw, one of the 4pcs 8.3kw is for spare using.
What is the heating speed with the 28KW heating elements power in the client current experience? ‘So what I do at the moment with the Elements is once the Liquid is over the top of them I switch them on and fiddle with it until I am at total Volume in KTL. It generally takes mer about half an hour to get a rolling boil once the KTL is full doing it this way.
The Elements I have currently are 4 x 7KW 3 Phase Elements. This is in both the KTL & HLT.
It will take at least 1 hour to spare/Lauter probably more like 1.5 so The slow heat up time shouldn't be an issue as its what I do to date.
I haven't had any problems with Scorching yet and the way your elements are set up is much better than mine at the moment which are 4 x 1200mm Straight Elements in the one place’
So we found that the different is that we calculate the power based on the situation that start the heating after the full 1500L wort is transferred.
And the client’s experience is to heat the wort once the wort is over the top of the heating elements. So it is still ok with a only 28kw heating power as they actually heat over around 1.5-2 hours (they heat from the lauter process).
After combining the client’s experience and also considering to ensure a enough heating capacity once needed, finally we got agreement on a solution: We will make three breakers for the 77kw power to divide the elements into three small groups.
For example: 27kw+24kw+26kw
The client could start any of the group to heat the wort, like what they are doing now with their existing brewhouse.
And they can also start two groups of the elements or fully start them once any necessary.
This also decrease the scorching risk as they can freely choose to only open one or two groups elements once there is a scorching problem.
What is your experience or advice?
We are manufacture of beer brewing equipment. We hope to exchange ideas with you. It is interesting and make sent to keep improving the equipment design based on your feedback or advice.
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