Preheater?

[vawtman]

Awhile back Finsawyer mentioned spinning a fan inside a tank with a rooftop vawt to preheat and that got me thinkin.

Why not use the incoming water pressure/flow to spin blades or some other restrictions inside a heat exchanger before the water heater. It could be made fairly long and use no power.Not sure what the gains would be.

 Seems feasible doesnt it.

 V......?:>/

[Ungrounded Lightning Rod]

The heat comes from the power supplied - as flow rate times the pressure drop.  You'd get virtually no heat from it.

Further, you'd get the SAME heat whether you "spin a fan" or just let the incoming water lose some of its pressure through turbulence.  So why add a moving part (and trouble) for no gain?

The heat in the Finsawyer system comes from the power used to spin the fan against the water's friction.  You can shape your fan to generate a LOT of water friction - and consume a lot of power - to "waste" that power by turning it into a lot of heat.

[vawtman]

The supply line of the water heater comes in at 50degrees with lets say a 3/4in pipe thats alot of makeup.But what if we expanded that to 4in over a 10ft lenght with restrictions of some sort and then fed the heater.

 5 or even 10 degrees would really add up over time.

 I know im off base most of the time.Just Thoughts

 Thanks for the reply Rod

 

[Stonebrain]

To convert kinetic energy in heat directly you need

quite a huge 'paddlewheel'.

See my own experience

http://www.fieldlines.com/story/2006/11/7/202828/758

With a 15 liter 'paddlewheel'drum I didn't get

more then 6watt.

The energy in the waterflow is probably negligable and

anyhow you need to power a pump to make it flow.

cheers,

stonebrain

[Stonebrain]

This result was at 100-120 rpm maxi.

At higher rpm's the result might be a lot better.

[vawtman]

Stonebrain i saw your posting with the Torkmaster COOL.

 Ive always wanted to spin a squirlcage fan in water with the turbine but havent tried it yet cause i cant come across a big enough unit.

 Thanks for the reply.