optimum position of hot water tank/ stove for thermosiphon

[mab]

Hello all,

I want to connect a hot water tank to a wood burning stove so that it works by thermosiphon.

I can position the tank either:-

A/  alongside the stove (about 18" away), such that the cold pipe from the tank to the stove is straight, and there is a short vertical length in the hot pipe.

or

B/ raise the tank so that there is a vertical section in the cold pipe and a longer vertical in the hot pipe.

I was thinking that A/  would be best as it gives the shortest pipe runs (less friction; less heat loss), but then wondered if B/ would give a stronger thermosiphon.

Does B/ give a stronger thermosiphon? and if so what would the optimum height be (only have a few feet to work with as I'm in a caravan).

Any advice welcome

Thanks

mab

[JW]

I want to connect a hot water tank to a wood burning stove so that it works by thermosiphon

Its more the tube location.

Do a searh on "Boiler downcomer"

hope this link works-
http://www.google.com/imgres?imgurl=http://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/3/3/Fig_3_3_2.gif&imgrefurl=http://www.spiraxsarco.com/resources/steam-engineering-tutorials/the-boiler-house/water-tube-boilers.asp&h=319&w=267&sz=12&tbnid=rWpLkzQ1pPh3NM:&tbnh=90&tbnw=75&prev=/search%3Fq%3Dboiler%2Bdowncomer%26tbm%3Disch%26tbo%3Du&zoom=1&q=boiler+downcomer&usg=__otkTKm1tKRCLvTyicXzkgIAqt_8=&docid=HgmY7x7gp1Y-UM&sa=X&ei=zyAXUJbcA4Gm8QTg-IHICg&ved=0CHMQ9QEwBA&dur=2995

[mab]

Thanks JW,

the link works fine - and I think it answers the question:-

However, when the pressure in the water-tube boiler is increased, the difference between the densities of the water and saturated steam falls, consequently less circulation occurs. To keep the same level of steam output at higher design pressures, the distance between the lower drum and the steam drum must be increased, or some means of forced circulation must be introduced.

I'm not pressureising my system, still less producing superheated steam but it looks like a longer 'riser'' & 'downcomer' work better.  so it looks like my option A/ without a downcomer isn't a good choice.

m

[JW]

Thanks Mab,

  Since your application is not pressurized you can get the most convection and be able to use shorter tubes. As long as your downcomer isnt in the fire zone you should be able to get pretty good convection circulation.

JW