instant hw from steam?

[Natrat]

I was just musing over the thread on tankless hw systems that was bumped.

I was wondering, has anyone used a steam unit to make instant HW? I'm thinking that a little tube shaped calandria or similar mounted just by the mash tun could heat water to strike temp and probably sparge, too. Seeing as our boiler is oversize, getting up that much steam seems viable.

Anyone done something like this? Sure would be nice to get some of my real estate back from the hlt!!

nat

[jwalts]

Yup, one of the breweries I used to work at made hot water on-demand. The steam heat exchanger was immediately downstream (from the cooling water's perspective) of the wort chiller. Even when we weren't chilling wort, we could turn on the steam and route cold water through the heat exchanger to the HLT. Any heat exchanger that can handle steam flow through one "side" would probably work. You could probably even maintain a specified HLT temp with a solenoid-controlled steam loop if you wanted to.

Joe

[liammckenna]

A shell and tube hot water heater is what you want for hot water generation from steam. It is kind of like a calandria lying on its side. It is basically an array of small tubes surrounded by a large tube carrying live steam.

Works best dumping into a HLT but can be sized for 'on demand' if you have lots of extra peak demand power from your boiler. As with other 'on demand', the pressure drop across the system can be a primary concern for on demand use.

Pax.

Liam

[Woolsocks]

Cool idea. I wonder, though, if you'd get hot water any faster than just heating it up in your steam-fired kettle or HLT. Either way, you need a certain amount of time to transfer a certain amount of heat into a certain amount of water, right? And the boiler can only put out steam so fast.

[Natrat]

I knew it could be done...I was just wondering about efficiencies. The thing is, I have a 920000 btu boiler going here that could heat the kettle AND preheat mash/sparge water at the same time.

And the thing is, there's a brazed plate heat exchanger around here somewhere that I refused to use because I couldn't take it apart to clean it. I think I'm going to find out what the ratings on that are (if I can find it) and see if it can handle my steam. This might be worth a go! Thanks guys!

How would I rig up that temp feedback loop? Or I guess I could just have a small reservoir (say, an enlarged bit of piping) where I could control temp. Easiest might just be to have it run full bore all the time and have a metered cold water valve at a little mixing fitting...?

Actually, I think it'd be best if I (as you say) use it to preheat water going in to my hlt. I really like using my knockout to preheat the water for the next brew.

[Woolsocks]

Probably would be more efficient to not heat your HLT and instead run liquor from it through the steam heatex to bring it up to temp. The reason this would be more efficient is that the hotter your HLT is, the faster it loses energy.

[Laughing Dog]

Does anyone have a manufacturer of one of these steam water heaters?

Laughing Dog

[liammckenna]

Probably would be more efficient to not heat your HLT and instead run liquor from it through the steam heatex to bring it up to temp. The reason this would be more efficient is that the hotter your HLT is, the faster it loses energy.

While this is true from a physics standpoint, it really depends on the size of the HLT more than anything. More specifically, the surface area to volume ratio. The lower the better.

Also will depend on the lagging/insulation on your HLT and the ambient temperature of the room that houses it. Ours is always cool to the touch. It is extremely well lagged and thus functions as a heat sink for all sorts of things for us (refrigeration condenser cooling water, vapour condensers from the kettle stacks, cooling water etc.)

On a practical level, I need my HLT to act as a sink for me. I do not have on demand hot water. Like most of us, I consume vast amounts of hot water when it is available to me. Thus far, touch wood, I've never run out. This may be because my HLT is twice the size of my brew length and has a massive steam coil in it.

YMMV.

Pax.

Liam

[BrewinLou]

I have not used one, just looked into it so far.

http://www.hubbellheaters.com/html/modelf.htm

[mfos]

I just set up a similar system to this one using a shell and loop exchanger fed by steam and controlled by valve.

http://www.bellgossett.com/Press/BG-techtk699b.asp

The shell and loop exchangers come in all sizes (seen some 20+ feet). Mine is a small 3 feet and I found on Ebay for $90. Valve from local equipment surplus supply was $200. Works great.