Height limitation for natural circulation thermosiphon

In summary, there is no known limitation on the height of an overhead tank that uses natural circulation through a thermosiphon and heat exchanger. In some cases, starting the circulation may be more difficult at greater heights due to higher pipe losses and a smaller percentage of water being heated. However, there is no specific analysis for determining the ideal height for this system.
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rollingstein
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Suppose I have an overhead tank that heats hot water by natural circulation via a thermosiphon (& a Heat Exchanger with some source of waste heat), is there a limitation on how tall this loop can be?

e.g. Can there be an elevated tank at 30 feet with a heat exchanger at ground level that heats the water via a thermosiphon? What's the right way to analyse this?

Even more fundamentally, does a more elevated tank make a thermosiphon harder or easier to get going?
 
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Not an expert but I can't think of a reason why there would be a limit on height (unless perhaps you want to heat a space station or something). As i recall the flow rate increases until the pressure difference (due to the different densities in each leg) can no longer overcome the pressure drops in the pipework. I think starting will be harder with height because the percentage of water heated is smaller yet pipe losses are higher.
 
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What is a natural circulation thermosiphon?

A natural circulation thermosiphon is a type of passive solar water heating system that uses the principle of convection to circulate water through the system, without the need for a pump. It consists of a solar collector, storage tank, and connecting pipes.

What is the purpose of height limitation for natural circulation thermosiphon?

The height limitation for natural circulation thermosiphon is to ensure that the system can effectively circulate water through the system without the need for a pump. If the system is too tall, the water may not be able to overcome the force of gravity, resulting in poor circulation and reduced efficiency.

What is the maximum height for a natural circulation thermosiphon?

The maximum height for a natural circulation thermosiphon is typically around 3 meters (10 feet). This can vary depending on factors such as the size and design of the system, as well as the temperature difference between the collector and storage tank.

What happens if the height limitation is exceeded?

If the height limitation for a natural circulation thermosiphon is exceeded, the system may not be able to circulate water effectively, resulting in poor performance and reduced efficiency. In some cases, the system may not work at all.

Can the height limitation be overcome?

Yes, the height limitation for a natural circulation thermosiphon can be overcome by using a pump to assist with water circulation. However, this would defeat the purpose of having a passive system and may increase energy consumption and cost.

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