Thank you for reopening this subject in a thread specific to this topic.

Such pronouncements as "it is just a siphon" don't do the job when they violate the normal conditions that pertain to siphon arrangements.

Some comments may have been a bit cryptic but now we can openly debate and I don't believe their is more to this than a simple misunderstanding or misapplication of principle.

Picture this for example, you run out of gas an a passerby allows you to siphon from their tank to a container. What is the principle relationship of the tank and container that allows the siphon? It's not the orientation of one container to the other but the level at which the hose used picks up and discharges, is it not?

Okay now I'll step as side for the review and application of mighty minds to complete this puzzle.

I think you need to define exactly what you are talking about first.
Are you talking about systems which involve a change of state gas/liquid/gas? Or just liquid circulation due to change in density caused by heat?
I've had a couple of properties where the heating and hot water circulation was by the latter effect and there was no pump.
Del

Yep agreed but the thermo-siphon doesn't go through the coils is is an open tank. The in coming service water goes through the coils in the tank.

The answer to this question remains ambiguous. Two systems have been described. The first involves a basement atmospheric tank with piping up to and back down from a rooftop solar collector about 50 feet (15 m) above. No vaporization was mentioned. The tank is maintained at about 160 dF (71 dC). The water going up to the collector is cooler, and therefore denser, than the water coming back down. I don't see how that works. Also, if the pressure at the bottom is atmospheric, the pressure 50 feet up should be less than perfect vacuum. This makes me think that the original description is inaccurate or incomplete. There is no pump, but other details such as piping traps or inverted traps or check valves were not provided.

A different type of system trademarked "Cricket" has also been mentioned. This is a closed system of methanol and water at subatmospheric pressure, and it apparently involves evaporation/condensation. Part of the description seems off ("head" in the upper manifold), but if I think more on it, I may be able to see how the upward moving fluid is less dense than the downward, which will make this concept work.

I agree that liquid density differences alone are a weak driver. But with evaporation, the up column can be much lighter than the down. In flooded ammonia refrigeration, it is estimated that the mass of liquid moved is about three times the amount that is evaporated. For screw compressors, thermosiphon oil cooling is now a prominent choice (no pumps, no corrosion of the cooler).

BTW, I am mystified that some posts here have been marked off-topic. I gave GA's to those to help cancel the OT's. Thanks for the input.

Exactly what I mean...If you are going to talk about anything with condensation/evaporation with other fluids then I'm out 'cos I just don't get all that stuff.
I'd go for simple every time, a pump and some coils on a heat collector.

something like this but scaled up with bigger bore pipes.
The Ducks are optional.
Del

Hi Del,

The solar siphon has the added Methanol (alcohol) which means the liquid, in the closed, and so pressurised system (pressurised once the Sun starts shining) gets to Boiling Point at a lower Temperature, ~65/70°C ( ~150/158°F). Boiling at a lower temp' gets things moving sooner.

I have never used a solar siphon, but the system it uses in part can and is also used in the 6" hot water pipes in a long run in a Factory, where they have say, 21' (~7m) of alternate wide 6" pipe and narrow 3" pipe, to help push or pull the water through the huge heating system in a Factory.

Can anyone confirm this or was it only in the Factory I was last in?

Take care

AAarrrgghhh.
Exactly what I was trying to ascertain at the start.
Surely for a swiming pool one would want to keep to a simple water only system?
I think 2 separate discussions are required, and I have no knowledge of the sort (with vapour stuff!) you are talking about...
Del

Hi wire,

I could not agree with you more when you say it is all about locating in a geographically sympathetic site, and either building your home structured on the hillside.

Or buying a home and if possible re-landscaping the back and front gardens to allow two or three steps down from the furthest most place at the back of the garden. Moving down hill, then have a wide flat area, (he says tongue in cheek-----for Tennis Courts and swimming pool, he he,) then the slope where the house is runs down to the back garden with the house on a hillock and on down to a level front garden.

Or it can slope down to the house from the back garden and still have a level front garden. But with the house still on a small hillock.

The slopes are decided by the design of your garden and its size and whether you do actually want a pool in it, and want to make use of all the sun you can grab from that south facing hill, and/or North facing hill and pool with a south south facing solar heaters, or any number of solar-siphons.

With possibly another roof solar-siphon for heating the water for the house in the summer, and using at least part of the solar energy from the lower, cooler sun in the winter. I have tried to explain that solar-siphons can also be used in the garden as well as in/on the house.

The slope also automatically gives you head (^{Can I say that}?) for ease of water flow, just like the old English Mansions They ran water from several miles away to power a hugely powerful jet or fountain in the centre of the water garden/fountain.

They had no pumps then, so used the weight of the water and gigantic head falling several hundred feet to supply the house and fountains and water to keep the garden green!

Nice one wire.

Take care.

PS. Sorry for the bad explanation, there were a couple of words I was going to use but they floated away.

PPS. This has not slipped back to the pool heater thread, I was just trying to say what I had in mind where a solar siphon could possible be made to work better to heat pools as well as a houses.

Hmm...I think I think we're over thinking this.

First let's determine what factors would need to be present for a siphon to occur in the given scenario:

1) an open tank of about one thousand gallons water aprox...4' H x 8' D

2) a 1" tube fixed at 6" depth under the surface of water in the tank, extending 50' upward then about 40' horizontal and then returning about 50' again into the tank

What would the orientation of the tube end returning to the tank need to be in order to maintain a siphon? In other words where in relation to the input tube end would the discharge end need to be to maintain a siphon?

The location of the resevoir is not that critical. the location of the heat sink relative to the heat source is more critical. it is much easier to design a reliable thermosyphon with a heat source below the level of the heat sink.

benbenben

it is much easier to design a reliable thermo-syphon with a heat source below the level of the heat sink.

Thank you...use the model please

Allow me to reword the answer more directly:

There is no problem in locating resevoir beneath the heat source of a thermosyphon, as long as there is a heat sink that is located above the level of the heat source.

benbenben

In a vertical column of water the pressure decreases 1 psi per each 2.31 feet of height. At 34 feet above the level in the open tank, the pressure is zero (absolute) = full vacuum. (The vapor pressure of 160 dF water is approx. 5 psia, which occurs about 23 feet above the tank level.) Even a perfect vacuum pump couldn't suck water that high in the liquid state; instead the water will boil. This would make a good science demo: Submerge one end of a 40-foot clear tube in a bucket, 40 feet above attach a vacuum pump to the other end, and watch the water boil in the tube. How high up it starts boiling will depend on how warm the water in the bucket is.

This is why I don't yet understand the system as described.

Because of the many possible variations, it is hard to devise a one-size-fits-all abstract description. But I'll make this attempt: A thermosiphon consists of two vertical columns of liquid, with the bottoms connected to each other and the tops likewise. Heat is applied to one column but not the other. The warm fluid expands and/or boils, making the fluid in the warm column less dense than in the other. The greater weight of fluid in the cool column causes down flow in the cool column, pushing the less dense fluid up in the warm column.

The phrase "heat rises" is imprecise, but it more or less fits. In the case of the "Cricket," it appears that solar heat is applied near the top of the up column, but nonetheless still in the upward direction of flow, so that the average density in the up part of the whole system is less than in the down. This makes sense and ought to work. In the picture I can't quite see how the slender vessel near the final upturn of the collecting tubes is connected, so I don't yet know its purpose.

A thermo-siphon consists of two vertical columns of liquid, with the bottoms connected to each other and the tops likewise.

This maybe a part of the confusion, in the method I'm describing the bottom ends are not connected to each other.

The question is, what orientation (refer to post #8) would be required of the bottom ends in order to maintain a siphon beginning with the tube full of water?

It shouldn't matter. For a simple siphon, once it gets going, the free surface of liquid that the down portion discharges to must be lower than the free surface of the liquid that is feeding into the up portion. You can't siphon from a tank back to the same tank unless the densities of the up and down fluid are made unequal, or unless the tank is partitioned and the siphon is from a higher level to a lower. Further, if the up and down tubes both go into the tank, then the bottoms are indeed connected, via the tank.

Okay, now I have a tube filled with water and both ends in the same tank, the water will not escape, true?

At the zenith of the tube is a solar collector. What effects will be observed when the sunshines on the collector?

I'm not so sure about that. For the reason mentioned before, at the top of tube (or u-tube) that high, if the bottom is at atmospheric pressure, the top should be vapor (steam).

Is this of a closed or open system?

This assumed an open system, atmospheric pressure at the bottom, just as you're describing with the tank. A closed system 50 feet high could have zero or near zero pressure at the top, but the bottom would be at 50/2.31 ~~ 21.6 psi. (Divisor varies a bit according to temperature.)

Alright though the system does work well actually so how could this? Is as guest wrote:

There is no problem in locating reservoir beneath the heat source of a thermo-syphon, as long as there is a heat sink that is located above the level of the heat source.

What could it be?

Hi Tornado,

The simplest version of thermo-syphonic heat transfer could be found on early internal combustion engines( much used by the farming fraternity) where-in the engine cooling water system was comprised of an open topped tank possibly 2ft in diameter and 6ft tall standing alongside the engine with the cold ,return from the tank entering the cold end of the cylinder and the hot flow leaving from the cylinder head and connected by a continuously rising pipe to a point below the water surface in the tank. As per all such systems they had to be self venting as there was no motive power applied to the water circuit.

Provided the top pipe remained submerged beneath the water surface in the tank the engine would dissipate the heat to the tank where a temperature gradient would be established. The tank acted as reservoir, heat dump and the return side of the gravity column.

OK so far, when the water level in the tank fell below the riser dischage (thru' evaporation) all density driven circulation would cease and the engine would then cause the stagnant contents of the jacket to boil whereupon steam and water would be discharged into the tank with a replacement volume flowing in from the tank. This then became known as a 'hot cooled' engine!

The open vented domestic 'gravity' hot water system is another example; but all have one thing in common, the hot store or heat dump must be above the centre line of the heat source. The greater the vertical interval the better the rate of circulation.

Like most things the simpler the better.

Massey

Hi Tornado,

I am so pleased you started a dedicated thread on this subject. It is an interesting one for sure.

I have not read more than a couple lines but I am sure you will get more involvement here in your own thread.

Take care

C'mon guys it's not rocket science...
We are trying to heat a cold swimming pool right?
If you want a thermal circulation the heat source must be below the pool.
So dig a hole to put the sun in a stop messing about.
Or maybe put the pool on the roof and the solar panels on the back lawn.
Cheeses H whatsits.... use the circulation pump before I set Kris onto this thread.
Del

The layout that guest "benbenben" describes tends to promote better flow. Think about it this way: If the heat input is at a low location, the fluid there and all the way up is warm. If the heat sink is high, the fluid there and all the way down is cool. This is optimal for creating a density difference throughout the length of the up and down columns.

Del's descriptions of weakly performing thermosiphons seem to stem from from less effective, but not necessarily kaput, layouts.

Thanks to Massey for the history. The "heat cooling" he describes is the same as ebullient cooling, which I have done by accident (lost radiator cap) but is sometimes a useful design.

Flooded ammonia refrigeration has been around a long time, and though not historically called thermosiphon, that it exactly what it is. When thermosiphon coolers were first put in for screw compressor oil cooling (1970-ish?), there was for a while a confusing variety of layouts such as sloped shell-and-tube coolers. This was soon discovered to be unnecessary. Horizontal works fine, and now there is a move toward furnace nickel-brazed stainless plate exchangers. In most if not all of these refrigeration applications, the heat source is at or near the bottom, with the heat sink and reservoir higher.

To be a bit abstract again, this latter criterion is not absolutely necessary. Anything that results in the average density of the up column being less than that of the down column will generate flow. It will be sluggish in the case of all-liquid, but if the up column contains vapor, flow rates will be usefully high.

In the system "bwire" described, I suspect there may be a second coil in the tank that connects the up/down portions into a closed loop, as in the "Cricket" system that has a double-wall exchanger at or near the bottom, and hence is a closed system. But this is the "mystery," the detail of the schematic that remains uncertain.

(I haven't found the right combination of AutoCAD plus export method for inserting importable images into these threads. No doubt simple, and I hope for suggestions. Then I could do schematics.)

Hi Tornado,

I have pasted the discription of the solar siphon below for any ref:

----------------------------------------------------------------------------------------

Edition #74: Spring 1993

"Copper was the only material we could trust to last at least 50 years in our solar water heater." This is how Bob Block, president, Sage Advance Corporation, endorsed the selection of the high-heat-transmission, corrosion-resistant metal for the critical elements in his company's "Copper Cricket."

The Cricket is unique among solar water heaters. It doesn't require any pumps, valves, controls or other moving parts or electric power to function. How can the Cricket operate without the costly complications of competing systems?

The array of copper collector tubes inside the Cricket.

"It functions like a coffee percolator," said Dr. Eldon Haines, the physicist who invented and patented it. Bubbles generated in the 15 percent methanol 85 percent water solution inside the copper collector tubes push the solution up to the header pipe at the top of the roof-mounted unit. Because the sealed system operates under vacuum, the solution inside only has to be heated to 65 F by the sun's rays to start bubbling.

The bubbling solution gathering in the header pipe generates enough head (pumping pressure) to be pushed down to a heat exchanger located underneath the user's existing water tank. There solar heat is trans ferred to the water in the tank. The now-cold solution is then pushed back up to the array of copper collector tubes by the down-flowing hot solution.

The all-copper heat exchanger, which can be located as much as 36 feet below the header, is double-walled. This safety precaution is needed because methanol is toxic. Because the methanol/water combination, unlike pure water, shrinks when it freezes, the copper tubing can never be ruptured by freezing. The systems are warranted for 10 years.

Just how much of a user's annual hot-water load can be provided by the Cricket? The contribution ranges from a substantial 91 percent in sunny Phoenix, Arizona, to a beneficial 41 percent in cooler Boston. Made in Eugene, Oregon, the Cricket is cost effective even in its often overcast home state.

----------------------------------------------------------------------------------------

Take care

Hi Burnt Silicon,

Here on in known as BS or burnt!

I think that was a pretty good answer hence the GA Sir.

Take care.

And another GA to "BurntSilicon." I can't yet agree that a column of liquid will move upward vis-a-vis a top-and-bottom connected column of vapor downward, but the rest of this is a gold mine of good info. I am most familiar with reservoir-at-top configurations, and that this helps. But I don't see that it is absolutely essential (see various posts). Thanks especially for describing the narrow vessel near the upper end of the "Cricket" system. I'll have to think about that a bit more, and maybe even dig up some curves on methanol-water absorption. Hey, if it used ethanol-water, a leak in the system would give you a hot toddy on tap, instead of being poisonous and requiring a double-wall heat exchanger! Oh well, dream on, I guess. Probably would be illegalized as a still, too. Damn infernal revenooers.

Hi Tornado,

Why not make a small scale model, say about A4 in size from glued clear plastic, making sure you glue the joints properly? You can then watch what happens?

Ethanol or what it is actually 100% alcohol at 15% water at 85%.

Bobs your Mothers Brother!

Take care, and if you do try this please send in a pic, OK?

Scale models are often useful, but in this situation, the full-scale vertical head is critical. Atmospheric pressure versus zero can push a column of water 34 feet high, but no higher. Thus a scale model say 15 feet high may not yield valid results for 60 feet high. This, or something like it, seems to be the sticking point among all these considerations.

Hi Tornado,

OK my friend, it was only a suggestion, which if I had the tools I would have done myself, but no matter.

You mentioned atmospheric pressure with reference to this. Can I remind you most kindly that the 'Cricket' is a sealed system which builds its own 'head' pressure by dint of the Ethanol.

Take care

This is puzzling, if the pipe is primed full of water already then what happens?

Thank you for the warm welcome, Baby Bear and Tornado.

Ready for more BS from BS?

The Cricket is not a thermosiphon. It is considered a "heat Pipe".

In a heat pipe no siphon action takes place. Heat pipes almost always use a phase change (The exception being- All gas filled heat pipes). Thermosiphons transfer heat by single-phase convection.

There is one more force involved in getting the methanol back to the collector - capillary pressure. Sintered metal powder, wicks of various materials, even micro grooves cut parallel to the pipe axis are used.

I don't Know what the following means.

"Allow me to reword the answer more directly:

There is no problem in locating reservoir beneath the heat source of a thermosyphon, as long as there is a heat sink that is located above the level of the heat source."

benbenben

Think of the reservoir as a pot of water and the heat source is the stove. I always put the pot above the heat source on the stove. If you put it below the heat source you will not eat hot food tonight.

A thermosiphon heats an insulated tank of water indirectly. It pulls the cold water from the bottom heats it a few degrees and returns it to the top of the tank. With each pass the water gets hotter.

What you need is two tanks, tank one is Insulated, and holds 95% of the systems water. Place tank one at least 12-20 inches above the bottom of tank two.

Tank two (The collector) should have tons of surface area to capture the heat and hold 5% of the total systems water. #2 should be shorter than #1 or placed at an incline so it is below the top of #1.

The two tanks are connected top to top and bottom to bottom. The piping should be run at a gentle slope down to the collector (tank 2). Run the top piping the same, a nice gentle slope up to the top of the tank.

PIPING

Larger piping will give you good flow but lots of lower temp water. Smaller piping will give some resistance to flow and the water will stay in the collector longer and get hotter. The hotter water at the top of the tank will also slow the flow. It self balances it's self, water can't move to the top of the tank unless it is hotter than the water that is already there. Remember more work can be done with 50gals. of 160F water than 100gals. of 90F water.

Give it a try.

Any heat you can catch is heat you don't have to pay for.

The sketch in the lower right of this last post conforms to what I have been saying all along, but I can see how other arrangements could also work. Of all possible geometries, it all comes down to the principle that the up column must have less avarage fluid weight (density) than the down column. There may be regions in which this condition is not met, but other regions can overcompensate.

The Cricket system has a down column of warm liquid. Some heat is removed in the heat exchanger at the bottom. Cooler liquid then move upward through part of the up column. Near the top, this liquid evaporates in the solar collector, so when we consider the up column as a whole, its overall density is less than in the down column. Hence the flow.

The write-up on the Cricket mentions a maximum height difference of 36 feet, as I recall (?), which makes sense. If more than that, the denser up column would outweigh the lighter down column by more than what the solar collector could evaporate in compensation. Less than 36 feet difference, the presence of vapor in the up leg makes the overall up density lower, which induces flow in the desired direction. Thus I'm fine with the Cricket, which is a closed loop.

Thanks to "BurntSilicon" (GA) for helping to clear that part up. There is still a

Hi BS,

Welcome aboard! Your diagram is definitely worth a 100 words (saved). If you refer to my earlier comment you will see all the components to which you refer ie heating zone, circulatory parts and the resevoir/heat dump.

Your reference to the phenomenon of the large flow and small delta T versus small flow and large difference still share one thing in common and that is the same Q as the available heat remains unchanged.

The real issue in this question of 'geometry' is what makes it function and we are all going in approximately the same direction in this respect. However there are two distinct genres apparent in the forum and they do need to be defined to avoid further confusion.

Firstly the hydraulically 'solid' system where the entire arrangement is full of liquid phase fluid, which remains so and this is likely to be characterised by large bore pipes and possibly modest differential temperatures. Large buildings in the 19th Century possessed complex heating systems without any form of ''accelerator'' now called a pump. The boiler was always in the cellar, and large bore cast and malleable iron pipes connected all the radiators, onlythe F&E tank was in the attic. They did take the precaution however of sticking a vent pipe out thru' the roof in case something dramatic happened 'down below'!

The internal driving force being the density difference between the hot and cold legs of the system; in a large system different legs would produce flows proportional to the cooling effect created by the radiators and the frictional losses of the pipework and therefore would have different delta Ts.

Next we have the bi-phase system.(open) In this there is the production of a fragmented hot column with a resultant reduced 'weight' much more so than in the previous 'solid' system. The perfect example being the percolator as with a 'head' of say 6'' of liquid in the body (reservoir) the rising main can project spurts of boiling water and steam another 3''upward. The clue to the modus operandii of this system is the collector in the base of the percolator and the relatively small bore rising pipe. If that pipe was of a larger bore nothing much would come out of the top. The column of fluid must become discontinuous to permit a sufficiently large density difference to drive the column upwards faster than the gravitational forces can send it back down.

The house heating vent pipe could deliver a 'percolator' style display if some character got a blast furnace going in the boiler!

When we consider the 'Cricket' type system we have a bi-phase closed system with the upper parts under a sufficiently low pressure to permit ebullition to occur at modest temperature and the liquid/vapour flow to depart from the heat source which encourages cold solution to re-enter the heater section. Without the benefit of any valves the effectiveness of these systems will be very dependant upon the physical layout and guarantees such as ''it will work anywhere'' must be questioned. Pipe diameters and routes will become much more critical than I think we are given to believe.

I think that the categorisation into mono and bi-phase thermosyphon systems, both open and closed variants may help in understanding the process dynamics.

Comments are encouraged,

Have fun,

Massey.

Hello Guest, AKA Massy,

Why do you not join CR4, it, as you have seen is a great place to thrash ideas out and to finally agree at the end!........... Well, sometimes anyway!

I had a 'back-boiler' actually behind the back of the lounge fire. It WAS the heat pump, though I only had it set up to get hot water for cleaning, not heating, we were 'hard' in those days! ............. But, no fire, no circulation, and so no hot water. With this system the back-boiler pipe who's water got very hot from the virtually direct fire, went up through the bottom of the hot water collecting tank. Did about thirty spirals and came out of the top of the tank and down to the back-boiler again.

The point being that the back-boiler water never came into contact with the water its spiral was heating. But as I say, it worked if there was a fire (heat pump) only.

There was no sloping pipe and fancy geometry, just a straight up and down pipe.

I think the reason the cricket works apparently so well depends on two things. That the liquid in its closed system is between 15%/20% Ethanol (alcohol) and the placing of the tank of water it is heating. I see this as no problem, because you could:

1) make sure you researched all the details necessary and got the water tank to be heated by the cricket correctly positioned first time. Or,

2) move either the cricket or the water tank up or down slightly until it did work.

The alcohol boils at a lower temperature so the water will never be boiling in the system is is heating but, it will be about 30 °C from BP.

Let me know your opinions on this please. Oh, BTW, are you a plumber?

Please bear in mind I am no professional Plumber and have never used the Cricket.

Take care.

Hi babybear,

Yep, its only me incognito! Seems like the login failed to work and I didn't notice it until just now. A real bummer as I've notched up a pair of GAs to boot!! I wonder if I can get them credited somehow, after all we need them real bad in this crazy depressed economy.

Yes, CR4 does help focus the mind and is (in general) a great place to explore avenues of thought, I have appreciated the new contacts.

No, I'm not a registered plumber just an engineer who has spent most of his life it seems around piped services,its always been a challenge to look at an appararently random and nondescript collection of pipes and then be able to suss out what it was really intended to do.

I will cite a recent example. 'Vacuum steam heating' A glorious example of early 20th century space heating in a 50,000 sq ft building. Someone had decided in the 1970s to do away with all the steam side kit, fill the whole damned thing up with water and make it into a LPHW system ( oh yes they had remembered to remove the steam traps from each rad).

Sorting it all out without ripping it out and making it work in an energy efficient manner was stimulating and rewarding.

Enough said for the moment.

All the best,

Massey.

Hi Massey,

really nice to see you are no longer 'incognito'!

If you think you may have lost any GA's, why not post admin on PM and explain what happened? Though, as I understand it, and may well be wrong, but I thought any GA would be set to your name whether you are posting your own user-name or your incognito self?

It shows in your posts that you are a professional Engineer by the way you really understand and explain to this thread and especially in your last few posts.

Certainly sounds as if you had your hands full trying to figure out what to do with the Vacuum Steam Heating, and would imagine you had to fettle some pretty special items to make this work? I have not heard of this before so, congrats!

Take care, and my sincere thanks for the reply.

More BS from BS.

Stop lumping heat pipes and thermosiphons together, they are similar but not the same. They are as different as Diesel and Gas engines.

Thermosiphons:

Uses single phase heat transfer

They can be open or closed loop systems

The Target medium is heated directly (The water).

Heat Pipes:

Uses a 2 phase heat transfer

The system is always closed loop.

The target medium( the water) is indirectly heated because of the toxic nature of the working medium(The methanol,Ammouna,ect...)

Besides heat pipes are harder to construct, handling toxic chemicals, tools for produceing a low pressure enviroment inside the system and the system has to be totally sealed. Not to mention an interface, to transfer the heat and seperate the water and methanol .

Thermosiphons are made from stock plumbing supplies, No special tools, no interface, and no toxic chemicals.

I hope this helps to clear thing up for a few people.

Hi BS,

How to confuse me without really trying!

Having not used one, I took it that a 'Cricket' was a Thermo-siphon..... Oh well.........

When is someone going to post a description of exactly how are where the Cricket should be fitted? Or was I yawning then..............

Take care

On a roof...

Check this out...

The flat, glass-topped Copper Cricket resembles a skylight when mounted on a roof.

Hi wire,

So, in your pic........... Touch od deja vu going on here!..........

In your pic the cricket would be fittet near the ridge?

Giving enough space and 'head' for the pipe going to the borrom of the tank?

Take care

Patent 4,478,211 describes the Cricket mechanism in detail. When I searched on a while back, I didn't find anything (or maybe too many things to notice the right one). Some of the operation seems thermosiphon in nature, but not all. The inventors emphasize geyser pumping as a (or even the) main principle. I found this via the search phrase "cricket solar collector". The patent was among the first few hits. Interesting read.

This may be a matter of preference in terminology, but I would consider a heat pipe to be a special-case geometry of thermosiphon. If by "two-phase" we mean liquid and vapor as the two phases, this most closely fits my experience, in which liquid/vapor oil coolers are standardly called thermosiphon. They have separate up and down pipes, unidirectional flow in each, with heat source lower than heat sink. If by "two-phase" we mean counterflow within the same pipe, (as in liquid sluicing down along the bottom of a pipe while vapor moves up along the top of the pipe) ("sewer flow"), then this is more like a heat pipe.

Thanks to all for the interesting input and several GAs.

Hi Tornado,

I would be interested in viewing that search page, thanks.

Take care.

What is a heat pipe on globalspec

Thanks Baby Bear,

Great PDF file. If you can wade through the two header/vapor condenser designs they throw at you. It gives allot of info.

The devil is always in the details. The vapor condenser allows the system to work over a larger temperature range. When the collector gets too hot and makes more vapor and pushes less liquid alcohol into the header. The condenser tube steals some of that heat and condenses the alcohol back to a liquid so it can travel to the lower part of the system to heat the water.

It looks like a good system for cool climates. The alcohol would keep it safe from freezing and since it's not a thermosiphon it won't reverse and turn the collector into a radiator. Stealing paid for heat from your water heater. I bet it would vapour lock in warmer climates and be ineffective for a large portion of the day.

Just my observations.

Thanks again for the PDF. That got you a GA from me alone.

Hi BS,

Unfortunate two upper case letters there my friend! Makes me smile.

Thank you for your welcome reply post, OK?

I thank you Sir for your GA.

I feel I had to list it if not for anything else, for the double header, was not at all obvious from any pic of the assembled Cricket, or, at least not obvious to me. You are very correct, the devil is in the detail, though I have to say at such a price it is pushing it somewhat when all the parts can be bought for something less than one quarter of the total. Perhaps this is shown by the relatively few actually sold? For what it's worth I feel a whole lot more units would have been moved, and far less copies of this product would have happened. That is just my personal opinion, OK?

It hardly matters whether it is called a 'Thermo-Siphon' or 'Heat-Tube', ............

Take care and thank you once again.

Some earlier heat pipe descriptions seemed no different, really, from the thermosiphon concept (the wicking feature was not mentioned). Bwire's excellent link explains this feature nicely, and I will adjust my terminology to recognize "heat pipe" as a distinct variation. Thanks!

Still unexplained is how the apartment system with the lower atmospheric heat sink and tank, and the 50' higher heat source, works. Perhaps a wicked heat pipe concealed? (That's wicked as in past tense of wick, not as in evil--pronounce as one syllable!)

OT: Who is "Ralfe" Waldo Emerson? I know of two Ralphs, one the 19th-century essayist, the other a shipyard VP around 1980.

Hi Tornado,

Thanks for the reply post.

I edited my profile several weeks ago and kinda got the spelling just screwed up, sorry. But this is the Ralph Waldo Emerson I was referring too. It is correct now.

With respect to "Ralph Woldo Emerson"

GA. Both your drawing and your explanation are clearer than the patent documentation.

Thanks Tornado,

I think I will RAR the JPEG'S and upload them to rapidshare and post the link.

If you guys think it would help.

Hi BS,

I would definitely think of changing your user name in light of what you say is a "Wrong" definitive!

Been there done that............. And although my memory is terrible I still recall in detail the 'slapped wrists' I got from one or two members! It is called being Human, right? Respect to you for continuing to mull it over and coming 'clean' so as to speak. I was not going to visit this thread anymore because from the OP's details, I at first thought I had figured out how a 'Thirmosiphon' worked. Then you and perhaps one other, I can't recall now, put the kibosh on that by altering the definition which was 'set in stone' on the Patent.

Problem is, when there is just two 'choices' or definitions, anyone can be 100% right or, 100% wrong?

Then another came along and called the system a heat pipe. I just got totally confused. Which is when I stopped posting.

On coming back after getting the notification you had posted I see there has been a whole lot of changes to the GA votes, oh well se la vie!

Is the illustration in the post I am answering one of your drawings? If so it's pretty good drawing. Shame about the text not being clear. One day CR4 may even be able to receive any picture document and translate it correctly?

Take care.

I think you're quite right here. I'm not sure that the term "thermosiphon" has a widely agreed-upon definition, especially in theoretical versus practical usages. Thus simple convection, change of state, fractional distillation, geyser pumping, wicking, and perhaps other effects, might be involved. Or not, depending on where some line is drawn.

In my refrigeration world, this is a common technique, and in that context it usually applies to a descending column of liquid versus an ascending column of vapor-liquid mix, or possibly even all vapor.

This also leaves aside the difference between liquid-vapor mixtures consisting of vapor pockets alternating with liquid slugs (Cricket), versus a relatively homogeneous froth (more likely in refrigerant piping). It would be interesting to see these processes through transparent piping. (I have actually seen a Freon system built out of blown glass, except for the compressor.)

When thermosiphon oil cooling was first introduced in refrigeration (1970s I think), there was for quite a while a weird proliferation of designs in which it was thought that the cooler had to slope, etc., but over time this has pretty well sorted out.

Hi Tornado,

Thank you so much for your reply post...........

Fully agree with your opinions here! There is too many to visit but this is the reason I and I think you have based there ideas on the Cricket 'Thirmosiphon'!

I do not want to go through the ins and outs of a thousand details of what someone may call a 'thirmosiphon', because as you say unless the detail is centred or focused of a specific Patented idea and physical model as with the Cricket, whatever is said can always be referenced back to the Patent drawing and text. If that is not mentioned, well, it really depends on the site any particular info' is gathered, and/or the 'third person' ideas of a poster.

Not having used the cricket, I am very careful to base any judgements on it as I know of it on the Patent details. In that respect a "wheel" is always round.

Hi babybear,

I think I will keep BS as a user name it serves me right for making a few quick assumptions about a design on my first post..

I always learn from my mistakes, so in my book being wrong is not too hard to admit.

Don't get too caught up in the terms, Thremosiphon, heat pipe, or even the thermal geyser pump. They all are passive heat engines. I learned a great deal studying the PDF you posted. The only piece of info missing is how do you match the size of your collector with the size of the heat exchanger. The only reference I found was to make the capacity of the exchanger larger than the header.

The drawing is mine. Not to scale. Made with pencil and paper, scanned and labeled with MS Paint. I should RAR it, upload it to rapidshare and post the link.

If you would like I will draw you an illustration of my thermosiphon-100Gal., 54sqr.Ft of collection surface. It works great and my wife and I never run out of hot water.

Last June I looked in the back yard (ground mounted) and thought I saw smoke. It was a warm 103F day here in AZ and the output pipe coming from the collector (190F )sprung a pin hole leak at a sweated connection. There was only 32psi in the system but the leak was flashing to steam once it hit atmospheric pressure.

It has only one moving part. An electric ball valve I made. The valve is either open or closed. It is controlled by a simple comparator circuit. The valve opens in the morning only when the output from the panel is 5F or more hotter than the top of the tank. At the end of the day the valve closes when the circuit senses the pannel output and the top of the tank to be the same temp. It is common at the end of the day for the valve to close and a few minutes later open again. The flow of liquid is stopped and the heat builds up in the pannel enough to open the valve. The hot water flows into the tank and the pannel output cools to the same temp as the top of the tank and the valve closes. If this valve was left off of my system the siphon would reverse at night and my collectors would become radiators and I would take cold showers.

In the summer months I turn off the valve and leave it open all the time. The water gets too hot to use, after it gets above160F.

Hello BS,

Your first line summed it up! I to made assumptions on one of my first posts and "quoting" stuff here to the experts, on things I thought I knew but which were 'grapevine' led and at least in part rubbish, does not work here!

Lets put it like this,............... Members will remember your name for sure!

I would be interested in your drawing an outline of your system, if you can find the time, thank you. That will be one of those documents filed under, "arr-now I know"! Well, until I forget it!

With this basic hot water system, as well as other things I have come across a few times, members and non members seem to worry about 'not getting it right'. That is to say, not getting any installation they may try 'correct'. Well, if it is anything like this 'thermo-siphon' or your system, it is really no big deal, because there is only a couple of pipes to attach to the collector on the roof, if I for instance get it wrong, and as you say the water comes out cold rather than at least warm, as long as you have a little forethought and leave a draining lug, (can't recall for the moment what they are called, even though I must have used them hundreds of times!, sorry) partly drain down, cut the pipe and move the 'Cricket' (shorter than thermo-siphon to type) and start again.

It is like rebuilding an Engine and getting the timing 180° out. Nothing is broken, so you keep at it until like me you realise the mistake, rectify it and bobs your Mums Brother, in it?!

Interesting to see you enjoy schematic drawing as I do, though I have no way at the moment to copy stuff to the web, I have always enjoyed it. It started when I had to draw and explain my intentions to the local council Architect, when a sewer broke on an old house, and this was in an area where I was not able to just change any type of connection of any pipe type from the inside to the outside without first getting permission from the little 'Gods' at the council. No pressure at all on me, much! I had to sit in the drawing office, borrow a pencil and draw what I intended to do (giving sizes and flow rates which, then, I had in my head anyway), right under the nose of people who had been doing it all their lives! I have since drawn the plans for three homes and the heating systems and, as long as there is no pressure, can make a reasonable job of it.It is only since I started here on CR4 that I have had to re-learn how to figure sizes and flow rates, because I had forgotten them. It was not something I used all the time anyway, but it woke my two brain cells up! They are having a right good chat at the moment!

I have yet to learn how to do so on a computer, but when I had to do it there were no computers.

Sounds like you must have some meaty pipes in your 'Cricket' panel if it holds a 100 Gallons? The couple I have dealt with were not 'Cricket' types but the same as you have with six 6' x 4' panels giving 144 ft².

I do not know the amount of water it held but it was in both times to heat an outside swimming pool. A pumped system which actually used the water from the pool which was collected from after it had been filtered, pumped round these 'rads' and returned to the water.

It took about 4 to six weeks to heat the pool water to a comfortable warmth. And cost nothing. The rads were taken from a house a few metres away where they were getting a completely new system fitted. We used second-hand angle-iron (2" x 2") (50 mm X 50 mm) for the frame to stand the 'rads' on and bought so either ¾" or 1" (18mm/25mm) copper. Remade all the joints on the 'rads' and de-scaled them and that was that. Painted the rads black and enclosed them in Polycarbonate. It kept them clean and also helped in the heating and kept the heat in.

Sorry got carried away there!

Take care.

Sorry for the bad drawing. The labels were bigger before I uploaded them.

I have photo shop I have never used. let me see if I can get a better image up.

.

Hi BS,

Is this supposed to be the link? 'Cos it didn't work my friend.

And yes it would help a whole lot!

Hi,babybear

I tried to use rapidshare, but they are playing games with there service. It used to be that if you had a file of 100MB or less you could upload it to Rapidshare and post a link. The restrictions being that each user would be limited to one free download every three hours, now they play hit and miss.

I tried the link right after I uploaded it and it said no free down loads at this time, Please check back later.

I edited the post, that's why it's blank.

What a waist of time. I will find somewhere else to post the files.

Sorry again.