Copper coiled water heater.

Hello all.

I’m wondering if anyone here had tried what I’m hoping to try: an open boiler pot with the insides coiled with copper pipe. The copper pipe is pressurized to about 25 psi from my main line, loops through the boiler coils to become my hot water. The idea is that since steam can only be steam once it gets hot enough to leave the water, my copper pipe that is submerged inside should not boil and there for hopefully will not explode upon me and my dog.

Another idea to combine with this is to attempt to close the system in a sort of, “pressure cooker” esk style and use the excess steam and pressure to power my Tesla turbine. Only problem with that is of course with higher pressure comes lower boiling point which could affect the entire “ no boiling in the pipes” theory.

Ideas?

I cannot state this enough: you do not want to do this!

First and foremost, anything above 15 PSI is considered high pressure steam, requires schooling and licensing, and for VERY good reason. 25 PSI is twice the pressure of most heating systems (12 PSI) and would do a tremendous amount of damage should it explode. Most likely, it would. This is why even electric, low temp, 90 PSI working pressure water heaters have pressure relief valves on them.

Rocket Mass Heaters may not always be the perfect heating appliance for a home granted, BUT one of their best features is that they are non-pressurized making them extremely safe. To try and pressurize part of the system would be extremely dangerous and ill advised.

With that out of the way, some of your theory is flawed. The only thing that keeps water from becoming steam at 212 degrees at sea level; is pressure. Submerging a pipe in water will still flash to steam with catastrophic results, it will just do so when the water inside reaches 240 degrees and not 212. The water surrounding it, if unpressurized will also boil off. On a boiler system replacing this water is called "feed water" and is so critical that there are triple back-up pumps to ensure make up water is ALWAYS added.

The other part that is scary is that you rightfully explain the dangers of pressure and water, but get the theory backwards. Pressure INCREASES the boiling point of water, not lowers it. This is how boilers work everywhere.

At the renewable energy plant where I used to work as a boiler operator, the 31 megawatt boiler operated at 700 psi, making the water boil at 534 degrees. BUT that only worked as long as we could maintain the pressure. The second a weld broke, or a valve blew its gasket, the pressure would go to 0, and the boiling point would drop to 212 degrees. Thats a problem when water is at 533 degrees. We had safety measures to deal with that steam explosion, but copper pipe is not a boiler tube, and I am sure you're not a pressure vessel boilermaker.

I LOVE, LOVE, LOVE steam, and know it can do a lot of work, but even as a licensed boilermaker and operator of high-pressure steam, I know too much to ever make a homemade system. Many people who have tried, have been killed.

I cannot state this enough to ANYONE: This is extremely dangerous and ill-advised.

I'm not sure if you found science on your side, but here's a good reference to see if your math is in order...

https://thermodyneboilersblog.wordpress.com/2017/01/23/what-is-boiler-horsepower/

Are you trying to get anything other than heat out of this.  You'll have to evaporate 40lbs of water per hour ( assuming some inefficientcies) to generate one horsepower)

Whatever you do, use pressure release valves...
Paul

Dean Chiasson wrote:Hello all.

I’m wondering if anyone here had tried what I’m hoping to try: an open boiler pot with the insides coiled with copper pipe. The copper pipe is pressurized to about 25 psi from my main line, loops through the boiler coils to become my hot water. The idea is that since steam can only be steam once it gets hot enough to leave the water, my copper pipe that is submerged inside should not boil and there for hopefully will not explode upon me and my dog.

Another idea to combine with this is to attempt to close the system in a sort of, “pressure cooker” esk style and use the excess steam and pressure to power my Tesla turbine. Only problem with that is of course with higher pressure comes lower boiling point which could affect the entire “ no boiling in the pipes” theory.

Ideas?

Hi Dean, So as noted above steam is big time dangerous as in explosive boil your flesh off dangerous But maybe lets try to figure out what you are trying to accomplish. From the sounds of it you want to move heat via liquid from the heatsource to where you want to heat up using a makeshift heat exchanger not a boiler per say. Did I get that right? If so then the answer is maybe. If you make sure your pot contains water and is not pressurized you will never go above 100 degrees celcius. Run your pressurized tubing for your hot water heater? through it with a circulator motor or via natural heat rise and the water in it will never reach boiling point. If there is any pex in the system though its heat point is much lower that boiling (pex is rated to 75 degrees celcius) so be aware. Any system like that you would want to make sure you have pressure release valves in place and an automatic mixing valve on the hot water heater to avoid scalding.
If you want to go down the pressurizing the pot of water route you are on your own. There are many more efficient far less dangerous paths to generating electricity from heat other that steam such as thermo electric generators or stirling engines, or gasifiers to name buta few. I find it telling that as soon as internal combustion engines became available all the small steam driven generators disappeared very quickly even though you had to buy fuel. Those early users well understood that steam was a demanding beast that had no mercy to it.
cheers,  David Baillie

I heartily agree with Steve on this. I spent enough time at coal-fired power plants during my career to hear the horror stories of steam leaks and the poor people that got caught in them. The lucky ones died immediately and the unlucky ones suffered for weeks with extensive burns inside (lungs) and outside their bodies. Whenever my travels through the plant put me near steam pipes, I moved faster past them because you never know when a pipe will give out.

My training is Chemical Engineering with a focus on power plants and I would not attempt what you are considering. I personally don't like working with systems that will blow up on me when I make a mistake. And I know that I will make mistakes at some point or another. Take care of yourself and your dog.

The way many of these responses have been worded, it's hard to tell which half of Dean's proposal is super dangerous.  The first bit, the second bit or both.

I believe they apply to the second part with the pressure cooker.

As for the first part (big pot with coil of city pressure water in it) I'll tentatively say that it seems pretty safe.  You'd want to be sure you know what happens if the pot simmers away all its water.  You'd only have as much hot water as is contained in the coil but you could slowly pump that into an insulated tank to accumulate some volume of hot water.

Nope, super dangerous.

It does not
Matter if the heated tank is non-pressurized, the water in the pipe is, making its boiling point 240 instead of 212. It does not matter if a non- pressurized caldron of water heats it to 240, or a nuclear reactor.

At that temp it flashes to steam, and steam expands at 700 times its original size. It will blow the pipe into shreds and no different than a literal pipe bomb.

You can put a pressure relief valve in, but
It has to open instantly to its full size or it will still detonate on you.

The Boston Bombing was a done with a pressure cooker and so was the digester explosion at the Jay paper mill in Maine. Watch videos of both and it’s apparent this is playing with explosives.

I'm missing something here...  If the water in the coil boils at 240F, and it's in an open pot of water that boils around 212F, how would it ever get to the point of turning to steam?

Mike Haasl wrote:I'm missing something here...  If the water in the coil boils at 240F, and it's in an open pot of water that boils around 212F, how would it ever get to the point of turning to steam?

In case i was not clear that was my main stipulation.

David Baillie wrote:

Mike Haasl wrote:I'm missing something here...  If the water in the coil boils at 240F, and it's in an open pot of water that boils around 212F, how would it ever get to the point of turning to steam?

In case i was not clear that was my main stipulation.

Because, while the water itself in an open vessel cannot get above 212 degrees, once it is converted to steam it certainly can.

You would be alright if:

The coil entered and exited the caldron BELOW the water line. Anything above that would be in the steam the fire created and well above 212.

The rate the water boiled off (keeping in mind you have no condenser to recover the steam back to water) was meticulously maintained to that water depth and never any lower. That would require a second means of keeping it to that level.

If he last point seems redundant and unnecessary, then keep in mind, all it would take is for the original poster to be taken a shower, the flow going to the boiling vessel slows, at the same time the fire roars. Unable to fill faster than the water boils off, the water level drops exposing the pipe to high temperature steam.

Boom.

That easy. That fast.

This is EXACTLY how boiler explosions happen.

Your safety valve might save the day, but that better be plumbed outside to atmosphere or there might be steam scalding.

It can be done, but by certified boilermakers and boiler operators who are licensed.It really is for a reason.

Ah, so the steam could get hotter if heat is still being applied to it.  That makes sense.

If the cauldron/pot has a wide open top, and it is boiling, and the heat is being applied to the bottom of the pot, am I correct in assuming that the steam won't get much over 212F?  Seems like once it leaves the surface of the hot water and is encountering room temp air, it would start cooling down...

Many old cook stoves had a water coil in the firebox with a reservoir on the side the reservoir being open (not pressurized) and above the inlet of the coil. When water turns to steam there is an incredible diference in volume. To give a visual a water column the size of a roll of dimes when converted to steam would take up the space of 340 rolls of dimes. Steam is an incredible power source but like Steve is pointing out it is an incredibly dangerous thing to play with.

Mike Haasl wrote:Ah, so the steam could get hotter if heat is still being applied to it.  That makes sense.

If the cauldron/pot has a wide open top, and it is boiling, and the heat is being applied to the bottom of the pot, am I correct in assuming that the steam won't get much over 212F?  Seems like once it leaves the surface of the hot water and is encountering room temp air, it would start cooling down...

Maybe, but here is the rub,,,

The safer the system is, the more inefficient it is as well.

The basic premise of a Rocket Mass Heater is how efficient it is. Does the original poster want to consume a lot of wood, using it to heat water that makes steam, that is not run through a condenser to recover the water in the steam? Because of that lost steam, this design also means a lot of cold water is introduced into the system that must use wood energy to heat up, with much of it being lost to steam yet again, in what is a revolving door of inefficiency.

The more pressure you introduce to the system, the more efficiency the owner will get, but at a price; not only is it an illegal build, AND operated system; it is a dangerous one to have in a home.

I am ALL ABOUT homebuilt stuff, as I know it is impossible to homestead by using your checkbook to pay for everything, but high pressure steam is not the place for homebuilt stuff.

Steve Zoma wrote:

Mike Haasl wrote:Ah, so the steam could get hotter if heat is still being applied to it.  That makes sense.

If the cauldron/pot has a wide open top, and it is boiling, and the heat is being applied to the bottom of the pot, am I correct in assuming that the steam won't get much over 212F?  Seems like once it leaves the surface of the hot water and is encountering room temp air, it would start cooling down...

Maybe, but here is the rub,,,

The safer the system is, the more inefficient it is as well.

The basic premise of a Rocket Mass Heater is how efficient it is. Does the original poster want to consume a lot of wood, using it to heat water that makes steam, that is not run through a condenser to recover the water in the steam? Because of that lost steam, this design also means a lot of cold water is introduced into the system that must use wood energy to heat up, with much of it being lost to steam yet again, in what is a revolving door of inefficiency.

The more pressure you introduce to the system, the more efficiency the owner will get, but at a price; not only is it an illegal build, AND operated system; it is a dangerous one to have in a home.

I am ALL ABOUT homebuilt stuff, as I know it is impossible to homestead by using your checkbook to pay for everything, but high pressure steam is not the place for homebuilt stuff.

When I read the OP I picture an outdoor wood "boiler" which isn't really a boiler as it operates at atmospheric pressure with a heat exchanger coil inside the tank... Hopefully he will respond with details.

I was picturing a big stock pot or tank sitting on a wood stove that is already heating their house.  It would only boil when the stove is really ripping.  Ideally it would be adjusted away from the heat (spacers/shims) so that it never boils and maxes out in the 150-190 range.  Then it only needs to be topped up with water every week.  

Mike Haasl wrote:I was picturing a big stock pot or tank sitting on a wood stove that is already heating their house.  It would only boil when the stove is really ripping.  Ideally it would be adjusted away from the heat (spacers/shims) so that it never boils and maxes out in the 150-190 range.  Then it only needs to be topped up with water every week.  

This was what I was thinking as well, except that they wanted to use high pressure to accomplish it.

It has a few problems. Energy can neither be created nor destroyed, just converted or moved, so in this case taking heat from the pot of water is going to chill the water as it is used to heat another area. To keep it at the right temperature, it will take a constant, or at the very least, a fire kindled more often. This will make a stove that is already efficient, and add an inefficiency to it.

Another problem is that it's a complicated way to move heat. Water controls are expensive, and while 600 times more dense than air, why not just put a fan on top of the stove and move air to adjacent rooms like that, either through a simple fan blowing towards the next room, or a blower with duct work? If that is not really an option, then considering the low cost of the rocket mass heater, why not build a second one?

It really not done because there are other, better ways to accomplish the same task with one of these stoves. There are stoves designed to do just what the original poster wants, and I have one, and it is an inside boiler that burns wood. But it is low pressure. Going to high pressure just flat out makes it dangerous and illegal to build and operate.

I have not said much about the making of electricity in the original posters post despite being dedicated to making power 24/7/365 in my work life from renewable power for the grid. I haven't because it is almost impossible to make micro-power from steam in any practical way in a home environment. As someone else mentioned, it takes a huge amount of fuel to make steam, and even more under enough pressure and volume to make electricity. That conversion is so hard to maintain that there is almost no work-around. Its cheaper to get it from the grid, or use other means to make power.

The other aspect to think about tough, is the sudden lack of electricity. With a woodburner, that would leave the steam and water systems without a means to move water, making for another potential steam explsoion.

The Tesla Turbine is ingenius, but also impractical.

The real problem with electricity is not in making it, but making quality power. To do that means controlling it, and that can be tough. My back-up system at my house is 20 KW, so plenty of amps (100) and voltage (245 volts), but matching the load to frequency (hertz) can be a bear at times. It seems it is often either to high or too low, and the difference between bad to good is only a few decimal points off of 60 hertz.

We have the same problem at work, stepping up the 116 rpm runner to 600 rpms to spin the turbine. A complicated set of blade pitch controls, along with disc brake is employed to keep it from being a runaway at no-load start-up, but coupled to the grid, it is electronically controlled at 60 hertz naturally. Even then there are times we get into leading or lag too much, not to mention getting nailed on kvar discrepancies. Get everything right and you got really good quality electricity, but get it wrong and you have a brownout, and a lot of burned-out electric motors in the house.

Like most things: when something is dual-purpose, it seldom does each function really well. Most of the time it just does neither well either. In my opinion a rocket mass heater is best used to just heat a space. Keep it simple is not a bad philosophy, and we get into trouble when we do home-built to do complex things.

Dean Chiasson wrote:I’m wondering if anyone here had tried what I’m hoping to try: an open boiler pot with the insides coiled with copper pipe. The copper pipe is pressurized to about 25 psi from my main line, loops through the boiler coils to become my hot water. The idea is that since steam can only be steam once it gets hot enough to leave the water, my copper pipe that is submerged inside should not boil and there for hopefully will not explode upon me and my dog.

It sounds to me like his goal is to get hot water.  Not transfer heat around a property.  The 25psi he's talking about is the natural water pressure amount in a household water pipe.  I've been assuming his goal is to connect that coiled hot water pipe into his house plumbing so that when he turns on the shower, the hot comes from the coil.  Instead of from a grid powered water heater.  Perhaps the dream includes an insulated tank so the water in the coil is slowly moved into a larger tank to store it.  In that case he'd have 10-30 gallons of hot water on demand.