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Steam is old school!!!


Dehner Distillery

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At or distillery we are expanding at an incredible rate. So naturally we are looking to up grade everything, and I mean everything. So I called on a buddy of mine that has done steam systems for over 35 years. We started talking and he made me stop and think. He said that steam is old school "it is ancient technology". Over all nothing has change over the last 200-300 years, same basic ideas.

He said the way to go now is simply "Water Boiler" not steam. With chemicals you can heat up to 250f with out boiling. Think about it, if you have 1 cubic foot and you heat it up to 250F with steam that is at 15psi, so condense that amount back in to liquid and it is about 1-2 oz of water. You can only put so many btus in the volume. Ok now take that same 1 cubic foot and fill it up with water at 250F that would be about 7.48 gallons at 250F. That is about 500 times more btus that can be put into the same space. Plus, he also was pressing the fact that the energy savings, would be about 80% less than a steam system. Example- one lb of water to heat to 212F takes about 150-180btus, and to boiler it into steam takes another 900-1000btus. The other cool thing is we can store btus too! So basically the boiler holds about 40 gallons of hot water at 250F there is a pump that runs the main feeder line, it pumps into a 50-90 insulated storage tank that holds 250F water , go out in the main loop and returns back to the boiler. We will tap into the main line or run plate fin heat exchanger to pull the energy to the units they will power. The nice thing is we can store heat for several days if we don't use our system.

When asked the cost of the whole install, misc parts, boiler, pumps,ect...everything I about fell over. He said $8000 but with a max of $10,000. We are also going to get a boiler way bigger than we need and he will just block off a section of the burners so we can expand at a later date. We are looking at a 350,000 btu boiler (not steam), he said it would be about the same as a 2,000,000 btu steam boiler. I am going to take his word on it. He is awesome! Now we fully automate our whole plant.

We are very excited to get this system installed. To me it just makes so much sense. I am just tired for these over priced steam systems.

Thoughts?

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Find another plumber. The steam or water are not the power sources, they are only the energy transfer mechanisms from the fuel burner to the point where heat is needed.

Given our options, there is no heat transfer math that makes a 350kbtu burner equal a 2,000kbtu burner, even if you had ideal heat transfer (no losses). This certainly won't happen with water, because we know the heat transfer efficiency of steam is better in comparison. How can a worse heat transfer mechanism result in less input heat being required? It can't.

At 15psig, steam will have 5 times the heat carrying capacity of water, 218btu/lb vs 1164btu/lb. Even if you were to run it at higher pressures and boiling points with the water, at best you might be pushing the water/glycol to about 260btu/lb. In addition, steam has a higher heat transfer coefficient than water and water/glycol mixtures. Not to mention that glycol mixtures have an even lower specific heat than straight water, which means they perform even worse than water does. So the "chemicals" are a trade off, higher BP for less heat carrying capacity. Steam can move more heat from point A to point B, and it can do it with higher efficiency.

The cost for a water vs steam boiler of the same size (hell even the same model) is not going to be significantly different (For example, something like a cast-iron boiler that can be used for either hydronic or steam). Sure, the steam trim is different than the water trim, but we're not talking night and day differences in the cost of any of this equipment.

Perhaps you can make do with only 350kbtu of input heat, but I suspect you will be incredibly disappointed with the heat up times. Probably take you 3 hours to bring 1000 liters to a boil, if it ever boils. In addition, jackets, coils, and heat exchangers that are using water are going to have to be larger/longer than their steam counterparts.

There is a reason steam is so widely used for this purpose. It has nothing to do with doing things the old way.

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Our twin 450 liter stills run off a 350k low pressure steam boiler. If we crank them up at the same time, it is roughly 45 minutes to heads. We shut the boiler off completely when not in use. Even the pilot light. It takes about the same time to heat the system up, as it does to fill the stills. The best thing about steam is that it's basically idiot proof, with virtually no moving parts, except a condensate return pump to keep the boiler full, run off an external float valve/switch.

I would always opt for easier vs complex, especially when there is no known way to squeeze substantially more btu's out of water vs. steam. There of course might be some transfer time differences between water vs. steam but it's not really conceivable that one form of heating unit (properly insulated) should perform substantially different from another, to heat x lbs of liquid.

I think your steam guy may be confusing lbs and gallons, with cu.ft. of steam, because there is virtually no way to heat a gallon of water with significantly less BTU's than a like "liquid gallon" of steam. It's just fuel in, converted to heat, and Delta-T out.

However this does remind me that I should insulate my condensate return tank.

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Delta T is helpful but not the most important thing when moving heat.

1 lb of water with a 20 degree delta T compared to your wash, Will add 20 btu's to the wash (in a perfect world)

1 lb of Steam condensing from steam to liquid water, will move 1000btu's

even if you could get a 100 degree Delta with your hot water, you would still need to move 10x as much water by weight than steam.

the reason steam is such an old technology is because it works, and havent found anything better yet.

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ok, great points. I under stand there are lees moving parts.

But, I normal Dehner fashion I would like to give the points that stick out. I am saying this in a funny way. Here I go...

1. 250F is still 250F degrees.

example- would you like to get crushed by a 1 ton elephant or one ton of feathers?

2. specific gravity, over all not really a problem...

example- would you rather get hit in the face with a cast iron or aluminum frying pan? They have different SG.......one is twice as heavy as the other..

3. btus per LB of water? neat but. lets look at btus per Cubic volume. Water turned into steam expands 1700 times it own volume so one LB of water is about 16 oz so what your saying is 1164 btus per 1lb of water = 16x1700= 15.74cubic feet of volume or 117.73 cubic gallons. By what your saying in the "hot water" world 1 cubic foot = 7.48 gallons @ 8lb per gallon= 59.84lbs of water per 1 cubic foot, so at your 218btus per lb of water 218x59.84= 13,045.12 btus per 1 cubic foot vs 73.95btus per cubic foot with steam (1164/15.74).

I am not trying to prove anyone wrong, just trying to see where I am wrong.

4. 350,000 btus of hot water vs steam is different because of the extra energy needed to over come the power needed to turn water into steam and maintain steam production. So I do feel, and research can prove that as long as you don't break that "Steam Barrier" far less energy is required.

I truly think this new system will be super efficient and do more than a great job for us. Also, not cost a lot.

Thanks for feed back.

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Correct, the temperature of a 250 degree liquid and 250 degree steam (15.15psig) are the same. However, the energy stored in 1 pound of each is different. Don't talk in volumes, we're not talking apples to apples, you need to talk in mass. A pound of water and a pound of steam - when boiled, a pound of water turns into a pound of steam, which turns into a pound of condensate (water). Why is volume irrelevant? The reason is that steam can flow faster through piping than water can. Typical steam velocity is around 100 feet per second for low pressure steam, maximum water velocity is like 5 feet per second. In addition, a water to water heat exchanger will generally need to be larger than a steam to water heat exchanger, so you can't assume they are operating within the same fixed volume (besides, steam will win if they do).

The bit you are missing is latent vs sensible heat, and the energy transferred as a result of the phase change from vapor to condensate, which is exactly the same energy required to turn the water into steam. So when that 1 pound of steam at 15psi condenses on the walls of the jacket or in the heat exchanger, it gives up all of the 1164 BTU to the transfer medium as part of the condensation process - this is a huge amount of energy. Then, as condensate, it also transfers heat. But, it is significantly less - which would be the same as with water, because it's not undergoing the phase change, you only have the sensible heat to work with. A pound of water at 15psi only has a total of 218 BTU/LB, and realistically, it can't give it all up (it would need to leave the jacket at 32'F to have given up all it's heat, not realistic - right). ASD mentioned it above, if the pound of water can only realistically give up 20-30BTU per pound, versus the 1164BTU per pound for steam. It's too early to do the math, but theoretically, you are probably need the water system to be sized more similarly to a fire sprinkler system main than a residential hydronic heating loop.

I still don't see how you are getting a 350,000BTU boiler to do the same work of a 2,000,000BTU boiler. The work is being done where the fuel is begin burned, everything else is just wiring the battery to the lightbulb. Even assuming 100% efficiency of the transfer (which is hogwash), 350000BTU/HR (boiler output, not boiler input) is only sufficient to take ~265 gallons from ~60F to ~212F in 1 hour time.

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This has been studied for hundreds of years. It is taught in engineering classes all over the world:

http://www.tlv.com/global/TI/steam-theory/overall-heat-transfer-coefficient.html

It's the overall heat transfer coefficient of steam... or more accurately the convective portion of the overall heat transfer coefficient.

Bednar is also correct about the energy stored in the latent heat and the fact that a boiler rated for 350,000 BTU can only produce 350,000 BTU... not 2,000,000 BTU

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It's not a matter of BTU density in the fluid either

it's total transfered btus

a 300,000btu/h system can only do so much work compared to a 1 million btu/H system

It's all about how easily you are able to move heat from one place to another.

Go ahead and spend the money to try and prove physics wrong. I guarantee you will find a little success but not enough to justify the expense or prove out a viable product. It all begins and ends with the math.

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I am not arguing, I am just trying to make some sense here. Good talk. I feel it is good to question why sometimes.

1. One of my thought is that it that it takes X amount of btus to heat water up to a certain temp. Then to turn it in to vapor it takes X plus Y amount of btus to do a phase change. So I have been told that I could heat water safely up to 300F as a liquid at no psi. Since it is still a liquid the extra or Y amount of btus is not needed.

2. How much of a 1million btu steam boiler is used to push past the liquid to vapor barrier, and maintain the vapor?

-----kinda like an air plane, it takes a lot of HP to get the plane off the ground but at cruising altitude minimal HP is required. So my idea of a steam boiler is reverse, it takes very little HP to get it up to temp and then it takes a lot HP to create lots of steam.

3. Volumes, volumes do matter. It is one of the only ways to compare the two as far as heat or btus per volume. The question would be -- given the jacket of said device what is the temp heat of the water or vapor or whatever leaving.

Like I told my guy, I don't care about wasting a couple hundred of dollars in fuel, when we are producing thousands and thousands of dollars in alcohol.

Good talk people. Keep it up. And play nice.

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Joe - as a pilot, I can tell you that you don't have the flying thing quite figured out either :) I think you might be confusing issues about flight by not taking into account inertia, as related to the energy (hp) needed to get any object moving from a stand still, the effect of friction on the ground, and then things like the decreased density of air at altitude.. Not to mention things like the stoichiometric / adiabatic variables of said less dense air at altitude which affects the amount of fuel being burned, and it's effect on hp output.

Back to the boiler, I can't honestly see how there would be any significant difference between heating liquid to 300 (with chemicals that would keep it as a liquid) than heating the same amount (lbs) of water through steam phase. I believe there are various types of equipment in industry that use hot oil baths to transfer heat, and maybe even some stills. But I don't think they give you any energy advantage and they also require you to maintain pumps that operate under extreme temps, that degrade seals and motor integrity, if taken to high temp.

I also don't get the theory that it takes X-BTU's extra to convert water to vapor. i would also wonder at what temp your guy thinks this magic happens. The header on my low temp steam boiler reads about 240 degrees at 5 psi. Does he consider that liquid or steam ?

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Edit: Was driving today and realized someone said that the energy used to phase change goes right back into heating the product when it condenses.

Very interesting read though. As a science nerd I learn more stuff off this form by accident than I learn intentionally--I love it!

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Out here water boilers are dirt cheap, and steam boilers are very expensive. I am talking Craigslist, homeowners that put in radiant floor heating and then changed their minds. I just bought a used water boiler, 150,000 BTU, rated for 250 degrees, for $175. I could have bought, and might eventually anyway, a 350,000 BTU boiler for $300. These boilers cost thousands new. I am building a 100 gallon still, and have a 300 gallon milk tank that I HOPE it will heat for a mash tun. Next question is whether it will heat a larger 250 gallon still? I am doing this on the cheap, steam is not even an option.

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We decided to go the fluid heater route instead of steam but not because we believed it would be more efficient. Our main purpose was to get away from having a costly boiler room and inspections especially since we're in a small space. We have a glycol/water electric heater that can sit on a skid next to the still and isn't a pressurized vessel, so no inspections and no additional space required for probably similar price to a boiler.

But since we're not running yet I can't say how good or bad it all works.

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I've been following this thread and thought I would add my two cents (for what its worth). This whole thread reminds me of similar Thermo 101 test questions in college. I've got a BS in ME and have done my fair share of heat calculations.....

The basic question is: Will a hot water (or similar liquid) system work to heat a still up to operation? My answer is yes (I've seen similar systems in operation). You could go the route of a hot water boiler or use a Baine Marie type system. But........

Will it be as 'efficient' as a steam system? For that you need to define what you consider 'efficient'. In the hot water system you are moving heat from the hot water to the still metal wall to the mash via conduction. The rate of heat transfer is many times smaller than a steam system so the warm up times are going to be much, much longer.

Why is the rate of heat transfer so much slower? In this application the power of steam is in the condensation of vapor to liquid. In a change of state such as evaporation/condensation there is a tremendous heat exchange. The energy required to convert water to steam is "carried" in the steam. When the steam condenses on the still wall the same amount of energy it took to create the steam is released back into the condensing surface. This energy is measured as Enthalpy and its the same process that allows an air conditioner or heat pump to operate. Evaporation and condensation allow an ultra efficient transfer of heat from one area to another. When a liquid evaporates it removes energy(think of sweating) and when it condenses it imparts energy. In a steam boiler the evaporating water removes energy from the boiler via steam and in the still the condensing steam releases that same energy into the steam jacket wall which then transfers it by conduction to the mash.

For a given mass of water the amount of btu's per square inch imparted by steam condensing at 212 degrees is a little more than 5 times what the same mass of hot water can do via conduction for the same given surface area. Its important to talk about mass and not volume. Volume is really irrelevant. Its the mass and the energy it contains that is relevant. Most energy calculations are done based on mass flow because it is a constant in the system.

In my 15 psi steam still it takes about 40~45 minutes to get 250 gallons of corn mash to heads from room temp. If I was using hot water to heat my still I am guessing it would take about 5 times (over 3 hours) that to get up to temp and I think running the still would be problematic as the 'throttle' response time of heat changes would take much longer to occur.

Is a hot water system more efficient from a fuel standpoint? Boiler efficiency aside and miscellaneous heat losses aside I think both systems would use roughly about the same amount of fuel to heat the mash up. Basically its the amount of btus to raise a given mass to a a given temp.

For a little tutorial see http://www.wermac.org/steam/steam_part3.html

Which system do I prefer? I love my steam system. I get fast heat ups, simple operation and a lot of flexibility. But I also got my steam boiler and mash kettle for free so I never had to budget for it so I can understand the budgetary desire to go with a 'hot water' solution. But given my experience I would recommend users of hot water based systems to think of steam when the budget allows.

Just my opinion......

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Many of the small cast iron hydronic boilers that we are talking about here can run either as steam or hot water based on the trim and ancillary equipment. Our 16hp Weil McLain 80 Series can run as either steam or hot water based on how it is plumbed (granted it's a bit bigger). There is no difference in the boiler body itself, it's the ancillary equipment, water feeders, low water cutoffs, pressuretrol, plumbing, and condensate feed that are different.

Very easy to find Weil Mclain EG series cast iron boilers on the used market these days. Technically, the conversion between water and steam is a matter of removing the hydronic components, and bolting on the steam components. Likewise, it's relatively common to find somewhat larger used steam boilers in Oil trim in the Northeast, converting to natural gas is as easy as replacing the burner (and selling the oil burner for good money).

We got our boiler for free as well, came out of the basement of a church where it had gone unused for almost 10 years. They had converted from oil to gas something like two years later, and their contractor installed a brand new boiler right next to this one. They shut it down and let it sit, because it would be too expensive to remove and dispose of. When we asked, they were ecstatic to have it hauled away. Win for them, win for us.

That said, we can wrench and have family in the trades, if you can't, or don't, this route probably isn't for you.

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