Homemade Heatpipe as model for One-pipe steam system

JK_Brown

I came across this video of a homemade heatpipe (strong vacuum evaporative heat transfer) showing the concept. The demo with temps, thermal camera and graphs is basically what happens in a one-pipe steam riser. It boils at low temp, about 78F, at the 1:00 mark showing the steam shoot to the upper end of the pipe. He also test simple heat conduction of the pipe to contrast.

https://youtu.be/BCQKwMSgmRI

ChrisJ

JK_Brown said:

I came across this video of a homemade heatpipe (strong vacuum evaporative heat transfer) showing the concept. The demo with temps, thermal camera and graphs is basically what happens in a one-pipe steam riser. It boils at low temp, about 78F, at the 1:00 mark showing the steam shoot to the upper end of the pipe. He also test simple heat conduction of the pipe to contrast.

https://youtu.be/BCQKwMSgmRI

Heat pipes are all over electronics.
Video games, PC's, laptops etc.

We tested one from a motherboard chipset where I used to work and it seemed to just be filled with water in that case.


I still see absolutely no reason the concept cannot be implemented into a home or even large building heating system. They can even work upside down and sideways and around obstacles if a wick is installed.

The Steam Whisperer

The concept is nothing new. Any system with a mechanical vacuum pump works this way. Change the vacuum, change the steam temp. There were one pipe steam systems that operated with vacuum pumps or naturally induced vacuum. One thing I was thinking is that there are a lot of materials that phase change at lower than 212F. I would imagine these could be used in a steam system to lower operating temps at atmospheric pressure. This would set things up for a rather simple condensing steam boiler.

ChrisJ

The Steam Whisperer said:

The concept is nothing new. Any system with a mechanical vacuum pump works this way. Change the vacuum, change the steam temp. There were one pipe steam systems that operated with vacuum pumps or naturally induced vacuum. One thing I was thinking is that there are a lot of materials that phase change at lower than 212F. I would imagine these could be used in a steam system to lower operating temps at atmospheric pressure. This would set things up for a rather simple condensing steam boiler.

Methyl formate boils at something like 89 degrees at atmosphere.  But the issue would be it's going to leave the system rather fast even when things aren't running.

I suspect most refrigants would unless it's a sealed system.

The Steam Whisperer

ChrisJ said:

The Steam Whisperer said:

The concept is nothing new. Any system with a mechanical vacuum pump works this way. Change the vacuum, change the steam temp. There were one pipe steam systems that operated with vacuum pumps or naturally induced vacuum. One thing I was thinking is that there are a lot of materials that phase change at lower than 212F. I would imagine these could be used in a steam system to lower operating temps at atmospheric pressure. This would set things up for a rather simple condensing steam boiler.

Methyl formate boils at something like 89 degrees at atmosphere.  But the issue would be it's going to leave the system rather fast even when things aren't running.

I suspect most refrigants would unless it's a sealed system.

We're talking sealed systems here.... Or nearly so, so the material should stay in the system pretty well. We have systems from the 1930's that will hold 5 to 6 inches vacuum for days without any assistance from a vacuum pump.

Jamie Hall

Sealed systems are, of course, getting to be quite common -- heat pumps are, after all. And they have been around for a long time -- mechanical refrigeration predates most of us.

Now having said that, it's rather important to keep in mind that a system which operates internally at some pressure which is reasonably close to constant and in which the phase change being used to add or remove heat takes place at that pressure and is driven by adding or removing heat externally, such as with a burner or a solar panel or a radiator or some such, is a very different critter from on in which the heat is transferred by means of pressure differences driving the phase change at reasonably similar temperatures, such as a standard heat pump or air conditioner of mechanical refrigeration system

The key difference is this: in the former class of systems, such as the steam systems to which @The Steam Whisperer is referring, the presence of a non-condensable gas, such as air, is not much of a problem. While they will work best with little or no non-condensable gas in them, they will tolerate a quite surprising amount. Were this not so, most steam heating systems wouldn't work at all; the whole idea of venting -- or in the low pressure systems the vacuum pumps or eductors -- is to remove the air which gets in to improve the operation. Small amounts of non-condensable gas are not a problem, and even large amounts can be tolerated without difficulty, although it is best if they can be removed.

Proper choice of refrigerant and pressure can enable this type of system to transfer heat from a higher temperature source to a lower one over a very wide range of temperatures. Methyl formate -- which is a very flammable and somewhat toxic gas, by the way -- is quite useful for applications near room temperatures, as its boiling point at atmospheric pressure is about 31.5 Celsius. The importance of leak prevention in these systems is to avoid the loss of refrigerant, if possible. If the refrigerant is water, this is at worst a nuisance. If the refrigerant is flammable or toxic or otherwise undesirable -- such as R22 -- this is a more serious problem.

What they cannot do is transfer heat from a low temperature source to a high temperature sink -- that is, function as a heat pump. To do that one must take advantage of the change in boiling point of the phase transfer fluid with pressure, and provide a means of pressurizing the fluid and later expanding it in a controlled way. This type of system can also use a variety of refrigerants, depending on the application. What they cannot do is tolerate even very small quantities of non-condensable fluid in the system. Thus leak prevention is considerably more important.

Please note that there is an entirely different class of heat transfer systems which make use of the heat released or absorbed when one material -- often ammonia -- is dissolved in another -- often water. Completely different physics.

ChrisJ

Jamie Hall said:

Sealed systems are, of course, getting to be quite common -- heat pumps are, after all. And they have been around for a long time -- mechanical refrigeration predates most of us.

Now having said that, it's rather important to keep in mind that a system which operates internally at some pressure which is reasonably close to constant and in which the phase change being used to add or remove heat takes place at that pressure and is driven by adding or removing heat externally, such as with a burner or a solar panel or a radiator or some such, is a very different critter from on in which the heat is transferred by means of pressure differences driving the phase change at reasonably similar temperatures, such as a standard heat pump or air conditioner of mechanical refrigeration system

The key difference is this: in the former class of systems, such as the steam systems to which @The Steam Whisperer is referring, the presence of a non-condensable gas, such as air, is not much of a problem. While they will work best with little or no non-condensable gas in them, they will tolerate a quite surprising amount. Were this not so, most steam heating systems wouldn't work at all; the whole idea of venting -- or in the low pressure systems the vacuum pumps or eductors -- is to remove the air which gets in to improve the operation. Small amounts of non-condensable gas are not a problem, and even large amounts can be tolerated without difficulty, although it is best if they can be removed.

Proper choice of refrigerant and pressure can enable this type of system to transfer heat from a higher temperature source to a lower one over a very wide range of temperatures. Methyl formate -- which is a very flammable and somewhat toxic gas, by the way -- is quite useful for applications near room temperatures, as its boiling point at atmospheric pressure is about 31.5 Celsius. The importance of leak prevention in these systems is to avoid the loss of refrigerant, if possible. If the refrigerant is water, this is at worst a nuisance. If the refrigerant is flammable or toxic or otherwise undesirable -- such as R22 -- this is a more serious problem.

What they cannot do is transfer heat from a low temperature source to a high temperature sink -- that is, function as a heat pump. To do that one must take advantage of the change in boiling point of the phase transfer fluid with pressure, and provide a means of pressurizing the fluid and later expanding it in a controlled way. This type of system can also use a variety of refrigerants, depending on the application. What they cannot do is tolerate even very small quantities of non-condensable fluid in the system. Thus leak prevention is considerably more important.

Please note that there is an entirely different class of heat transfer systems which make use of the heat released or absorbed when one material -- often ammonia -- is dissolved in another -- often water. Completely different physics.

Jamie,
So what are you saying?
That you feel it's impractical to create such a system?

I feel a heating system could be made with either just a heat pipe style system, or a vapor compression setup. I see no reason why both systems wouldn't work if you have a heat source.

If you want to do a heat pump, then obviously you need a, well, pump.....

mattmia2

I wonder if you could use a vacuum pump to keep relatively deep vacuum on a system and arrange you heat exchangers and liquid and steam phases in such a way to make a condensing steam boiler. I suppose it wouldntvwork with existing steam systems so you might as well just do hot water at that point.

Maybe it could work with existing 2 pipe systems with oversized existing radiation.

jumper

The Steam Whisperer said:

The concept is nothing new. Any system with a mechanical vacuum pump works this way. Change the vacuum, change the steam temp. There were one pipe steam systems that operated with vacuum pumps or naturally induced vacuum. One thing I was thinking is that there are a lot of materials that phase change at lower than 212F. I would imagine these could be used in a steam system to lower operating temps at atmospheric pressure. This would set things up for a rather simple condensing steam boiler.

Some fifties apartment buildings in Toronto used eductors to refresh vacuum periodically. Less air enables smaller pipes.

Putative reason for preferring HHW was no worry about slopes. I believe pump marketing had a lot to do with it. Give original installer a proprietary pump to sell replacement pumps; couplings; and motors.

Jamie Hall

Hmm. Well, that was a more than usually rambling post, wasn't it? Sorry about that.

No, I think what I was trying to clarify -- with a stunning lack of success -- is that a heat pipe is another -- and very interesting and sometimes very useful -- way to move heat from a hot source to a cool sink. As is a steam system. Or a system using some other phase change refrigerant (like methyl formate or whatever) or a hot air system or a hot water system. If it's a phase change system -- heat pipes included -- the hot source must be at a temperature above the boiler point of the refrigerant at the system pressure, and the cool sink must be below that temperature. Without the phase change pressure is not relevant, but much more mass must be used. Heat pipes have a certain fascination, though, as they can move the condensed phase against gravity in an ingenious way, and in the same pipe.

If you want to move heat from a cool source to a hot sink, however, you have to use a phase or state change of some kind, and if it is a phase change you have to use a pressure change as well. Hence a heat pump or any mechanical refrigeration. The fascinating exception is the gas fired refrigerator which uses both a state change and a phase change -- dissolved gas to vapourized gas to condensed gas to dissolved gas and back -- instead. I always have to think twice about those dang things to get my head around why they work at all...

ChrisJ

Jamie Hall said:

Hmm. Well, that was a more than usually rambling post, wasn't it? Sorry about that. No, I think what I was trying to clarify -- with a stunning lack of success -- is that a heat pipe is another -- and very interesting and sometimes very useful -- way to move heat from a hot source to a cool sink. As is a steam system. Or a system using some other phase change refrigerant (like methyl formate or whatever) or a hot air system or a hot water system. If it's a phase change system -- heat pipes included -- the hot source must be at a temperature above the boiler point of the refrigerant at the system pressure, and the cool sink must be below that temperature. Without the phase change pressure is not relevant, but much more mass must be used. Heat pipes have a certain fascination, though, as they can move the condensed phase against gravity in an ingenious way, and in the same pipe. If you want to move heat from a cool source to a hot sink, however, you have to use a phase or state change of some kind, and if it is a phase change you have to use a pressure change as well. Hence a heat pump or any mechanical refrigeration. The fascinating exception is the gas fired refrigerator which uses both a state change and a phase change -- dissolved gas to vapourized gas to condensed gas to dissolved gas and back -- instead. I always have to think twice about those dang things to get my head around why they work at all...

I've wondered about and I think even asked about absorption air  conditioning.

mattmia2

There are large commercial absorption chillers run off of district steam. Not sure about residential. It makes a lot more sense as a packaged chiller than a split system.

ChrisJ

mattmia2 said:

There are large commercial absorption chillers run off of district steam. Not sure about residential. It makes a lot more sense as a packaged chiller than a split system.

I was thinking about them running off of solar.

jumper

Jamie Hall said:

Hmm. ....... The fascinating exception is the gas fired refrigerator which uses both a state change and a phase change -- dissolved gas to vapourized gas to condensed gas to dissolved gas and back -- instead. I always have to think twice about those dang things to get my head around why they work at all...

Way to think about those refrigerators is that partial pressures are equal throughout. So with three components the system can purify ammonia enough for it to condense and become a refrigerant when it vaporizes to be absorbed by water. Steam heating has only two components, but the water is both vapor and liquid. The similarity is that ammonia has to be pure enough to condense in refrigerator's condenser just like steam has to be in order to yield its latent heat in radiator.

Difference is that refrigerator is small so that it can be easily sealed. If you can adequately seal a steam heating system then you can transfer lots of heat after you've evacuated enough air.