How to heat and keep hot a large volume of water?

[Kidds]

I want to heat a tank of water to 75-80°C and keep it there.
Until now I have used 3x 3kw washing machine elements in the tank but my new place doesn't have electric other than a generator.
My plan was to use an old oil central heating boiler but how to transfer the heat to the water in the tank or just run the tank water through the boiler? Submerge a big cast radiator in the tank and transfer heat to water in the tank like that?

This is to pasteurise apple juice. Juice is in 75cl bottles, 20 per crate, 3 crates per tank. Take them out after 40 ish minutes and replace with cold batch. My present setup needs the elements on constantly or very nearly to do this.
Text in bold is the question.

 

[Highland Mule]

how to transfer the heat to the water in the tank or just run the tank water through the boiler? Submerge a big cast radiator in the tank and transfer heat to water in the tank like that?

Either would work. You’re not needing a massive heat input at single digit kW, so it really depends which you prefer.

I’d probably direct plumb the boiler to your tank water, with a nice CH pump to circulate the water.

 

[Sharpy]

I would run the boiler water through the tank, as long as the water is clean there should be no problem.

 

[Kidds]

Thanks, that encourages me to give it a go and find out.
The water is clean to start with but have to admit to it getting bits in it sometimes. Maybe just try harder at not setting crates on floor.

 

[Sharpy]

Thanks, that encourages me to give it a go and find out.
The water is clean to start with but have to admit to it getting bits in it sometimes. Maybe just try harder at not setting crates on floor.

Briefly sit them in a shallow tank to clean them before immersion maybe? Plenty of time between batches surely?

 

[Highland Mule]

Thanks, that encourages me to give it a go and find out.
The water is clean to start with but have to admit to it getting bits in it sometimes. Maybe just try harder at not setting crates on floor.

If you’re worried, a good old fashioned radiator might be a deal. Problem is you’re looking to get the juice to 80°C, so the water needs to be a bit hotter. If you have a secondary cycle, it will need to be a bit more again, and there’s not a lot of headroom beyond 99°C for water! Check the boiler is happy to put out water that hot before you go too far - radiators would be at 60°C or less in your house, I’d think.

 

[Kidds]

Briefly sit them in a shallow tank to clean them before immersion maybe? Plenty of time between batches surely?

Time between batches is spent frantically trying to deal with the last batch and get the next one ready but enough time to dunk them in another tank

 

[Kidds]

If you’re worried, a good old fashioned radiator might be a deal. Problem is you’re looking to get the juice to 80°C, so the water needs to be a bit hotter. If you have a secondary cycle, it will need to be a bit more again, and there’s not a lot of headroom beyond 99°C for water! Check the boiler is happy to put out water that hot before you go too far - radiators would be at 60°C or less in your house, I’d think.

I have the boiler so no big stretch to set it up and see what happens re water temp in the tank.

 

[Sharpy]

Time between batches is spent frantically trying to deal with the last batch and get the next one ready but enough time to dunk them in another tank

Aahh. Just that you said 40 mins per batch.

 

[milkloss]

I’d go secondary circuit an run some sort of coolant in the circuit to avoid the boiling water issue. A couple of big second hand rads will do I guess. Boiler would also need a good adjustable thermostat that’s capable of the higher temps.
@Adeptandy might be the man for this?

 

[DrWazzock]

Use your generator cooling water circuit, if it has one. Combined heat and power. Generator would need a bit of load though.

 

[Kidds]

Generator would need a bit of load though.

How about 9kw of heating elements?

It's probably one of those things you just have to give it a go. So easy to overthink these things and it's a pretty simple task.
Looked up boiler spec and it switches at 55-81C so tank fairly close to boiler should keep it fairly hot and if I give a decent length of run for the return it should keep it up there rather than letting it go back down to 55.
In practice, once the tank gets up to temp it takes some time to cool down anyway. Longer than I need to keep the bottles in there. These days I have a nifty little computer thingy that calculates the time needed as it goes. It sounds an alarm when the correct time and temperature have been reached so time and temp are monitored for me.

 

[Green grower]

Have a look how a bulb steriliser works
Basically a large tank with a oil burner at the bottom with a flue through the Base usually runs at 44c but could just raze thermostat also a circulation pump to keep a even temp

 

[PSQ]

Genny with electric elements, but insulate the tank with Kingspan/ Celotex sheets to minimise the heat loss and massively speed up the time from cold to 'hot'. Best paying bit of Cellotex will be the sheet that you float on the open top of the tank.
I'd do a test with a pan on the stove first, to see at what temperature Celotex melts or to see if it taints the sterilising water horribly.
And if for some reason your venture goes tits up, at least you'll have a hot tub to woo the ladies in.

 

[Adeptandy]

How big is the tank and what fuel are you running the boiler on ?
You really need a secondary circuit, but 80*C will take some maintaining as its the top end of most boilers as you've discovered.

 

[jamj]

A boiler to bring it up and an element to help maintain it, as boiler will be at limit.

 

[Dry Rot]

Insulate the tank for minimal heat loss. If heat loss is minimised, i won't take much to maintain the temperature.

But the first question that occurs to me, is there no way to sterilise the cider and the bottles separately? i.e. heat the cider to 80 degrees in bulk and use another method (radiation?) to sterilise the bottles? I don't know, just throwing some ideas around before you spend money!

 

[upnortheast]

1st thought is it would be easier to pasterurise the apple juice before you bottle it ??
Then you could use a batch pasteruriser which is speced to get to 80 degrees then hold the contents there.

 

[thesilentone]

Mmm, not sure here.

If you are pasteurising, I assume you have to.

If you have to, I assume it is a regulation.

If it's a regulation you need a permit/licence/other.

If so, you need to meet the regulation.

A home made system may not meet the permit (if checked) as there are several other issues, particularly relating to condensate from the liquid being pasteurised.

Needs checking out.

There is a way around it.

 

[Grandad Pig]

Really need to pasteurise in the bottles to avoid airborne yeasts getting in. I used to put kids on loose, heat and tighten kids as it cooled.

often wondered if a big microwave oven would do the trick.