Re: Heating water with a TLUD #tlud #water

Geoff Thomas

Daniel and Shaked, an important fact used in hot water heating is that hot water rises as opposed to cold water.

How conventional, and or glass tubed, hot water systems generally work is that the hot water is below the tank, so it rises into the tank, generally entering in at the top, simply because it is lighter, and therefore leaves the hot pipes.
As it does that, cold water from the bottom of the tank sinks down to replace it, and finds itself in the entry to the hot pipes, - whereupon it becomes hot and rises in it’s turn, - this requires ‘no' energy but it does require that the pipes from the tank always rise, - no downward dips to block the flow, and likewise for the thermo syphon down to the bottom of the storage tank, +,  being close helps.
When the water in the pipes warms, the process begins, - without any senses, switches etc,

So, for eg in a solar hot water domestic situation you often have the tank directly under the hot water solar panels,- up on the roof, the classic configuration, or the tank in the ceiling above the woodstove down in your loungeroom, kitchen etc.
The thermosyphon requires no pumps, instruments. temperature switches, etc. - the water in the pipe gets hot and rises,but of course one can make a system with those, - and often necessary, but  not needing that extra level of equipment etc..
Hope that that muddies the water appropriatly. :)


On 2 Jun 2021, at 7:45 pm, Shaked From <shakedfrom@...> wrote:

Hi all,
I'd love some design advice on this.

I use a 200L drum TLUD every couple of weeks. The feedstock is usually paper/ cardboard/ sticks... It usually runs for 40-60 minutes depending on feedstock. Temperatures are around the 550c at the front.


I'd love to use the heat while making biochar. The latest idea was heating water. A copper coil inside the chimney?
I found a 200L stainless steel insulated hot water tank, and an old spa pool past it's used by date (but with no cracks in the main body).

The idea is to roll something like 10m of 1/2” copper pipe inside a stainless steel 150mm chimney section. A hose would be connected to the bottom end, with a valve before entering the copper, and have it free flowing through the copper and into the water tank, overflowing into the spa pool, with a result of having them both filled up with hot water by the end of the burn. Adjustment of the heat of the water in the copper pipe would be by adjusting the flow of water, and the idea of avoiding a valve after the copper pipe is to prevent restricting the water too much and avoiding any over pressuring.. This will all be happening outside of course. The spa poll will be insulated at the bottom and around the walls with some sort of insulation bats or pumice, and then cobb around. When the water in the pool gets too cold it can be topped up from the tank.


A few questions:
1. Would the copper survive the heat without water in it? Some copper pipe off the shelf has something like up to 120c or something like that on it? I could have it done in a way that the flue section with the copper in it can be removed during burns that are not running water.
2. When the copper has water running through it it can't go over 100c, but what about when I turn the water off, after tank and pool are full? 
3. What would happen to water left in the copper pipe but after turning the valve off, not pushing it out... Of course it will boil? Assuming theer is no change in height of more then 2 meters, would it just push through? Would it create too much pressure with risk to the copper pipe?
4. Does 10m of 1/2” pipe seem long enough and appropriate size? Too small would not allow enough flow and get too hot/boil/unefficient use of the heat. Too large would allow the flow but harder to roll into the flue, also provides less surface area...

Anything else that seems problematic or could be done better?

Thank you

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