What is faster?

[mckenry]

There are tons of threads on HEX and HERMS in general, but I have a question that if it has been covered I cant find it.

I want to know which of these is the faster method of getting my strik water in the MT up to temp.

Equipment.
HLT - 50L keg with the 2400w element and HERMS coil in it. I use the water to sparge with also. Normally has 42L of water in it.
MT - 50L keg. Normally has ~33L water in it prior to adding grains.
My HLT needs to be at about 75° to get my MT to 68°, for a simple single infusion at 63°.


What is faster?
Start heating the water in the HLT and start running the MT water thru the HERMS immediately, bringing the entire 75L up to temp at the same time,
or
Heat the 42L in the HLT up to 75°C before any MT water is running thru the HERMS, then bring the remaining 33L up to temp?

I havent experimented yet. I may have to if no-one already knows or some wiz can work it out.

Cheers
mckenry
BTW - if this has been covered, please link it for me.

 

[Camo6]

I imagine the second option would be a tad quicker as you're not accounting for the heat loss through the MT. Do you recirc the HLT, Mckenry?
One advantage I've found with having a standalone HERMS is having the two heat sources for quicker heating times. And means I don't need as big a HLT.


Edit: Sorry, didn't read it properly. I'm probably wrong but guess it is pretty close either way.

 

[The Judge]

Option 1 is taking 75L of water from ambient to 68C with 2.4 kW.

Option 2 is taking 42L of water from ambient to something higher than 68C with 2.4 kW, because you want the two volumes of water (42L of hot water and 33L at ambient) to reach an equilibrium temperature which you can then add more heat to via the element in order to reach strike temp.

Given that heat transfer occurs at a higher rate for bigger differences in temperature (LMDT) it suggests that Option 2 would lose heat at a higher rate to the surroundings given it will be required to be at a higher starting temperature, thereby using more energy and taking longer.

Caveat: I'm a pretty bad engineer, so best to double check by experiment

 

[Adr_0]

Man this is why I get on my soapbox about HERMS.

Heating less volume (42L) would be quicker, but you will lose a couple of degrees because you haven't pre-heated your mash tun, and then you might lose more once you start circulating through your HERMS to keep the temperature stable.

The best solution would probably be to put the required strike volume in your MT, circulate, have the bare minimum water level/volume in your HLT and blitz the crap out of that with elements, burners, searing hot iron, etc.

Heat loss to surroundings is a factor, but it's barely in the same order of magnitude as an element, i.e. it's about 10-30W for circulating pipe and 50-150W for the hot vessel.

 

[TheWiggman]

Agree 100% with Judge's logic, and based on that I would go first option. The obvious answer is try both and see how you go.

 

[Adr_0]

Yeah. I would get everything circulating, whatever is needed for strike - 75L or hopefully a touch less - and go with that. Less volume to heat = faster but by the time you dick around with all of your setpoints you have lost any time you might have gained I reckon.

 

[dblunn]

Reduced water volumes may not be an option as you will need your strike volume plus enough water left in the HLT for HERMS action and sparging. What about a timer to get it started in the early morning?
Dave

 

[Adr_0]

Reduced water volumes may not be an option as you will need your strike volume plus enough water left in the HLT for HERMS action and sparging. What about a timer to get it started in the early morning?
Dave

Oh dear...

Is there no way - for example, turning the circulation off for 10min while HLT gets heat back - then turn the circulation on again?

Otherwise, yeah, plan A it is for the sake of minimising disruption/chasing temperatures.