“Vacuum Boost” for steam heating system

izhadano

I suppose that energy savings of vacuum heating system come from:

• even heat distribution through the system (that's alone is significant; rule of thumb: one degree F of building overheat = 3% more fuel usage)
  
• quicker system heat up (smaller pipe diameter, less heat loss, less condensate in supply line)
  
• improved heat transfer in boiler (regime of heat transfer changed from conduction to boiling)
  
• lower temperature vapor usage in a autumn/spring heating season
  

More savings can be expected by zoning, automation and optimization of vacuum system.

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jumper said
@gennady proved this with the steam system versus the mod-con. He's a bit shocked by it himself. A mod-con with a combustion efficiency of 90% beat the steam system by only 4%.
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Three years ago I put a blog on Home Energy Pros questioning condensing boilers efficiency
http://homeenergypros.lbl.gov/profiles/blogs/scrutinizing-condensing-boilers-with-the-second-law-of.
May I see more @gennady info on this comparison? Just curious ...

izhadano

Hatterasguy said:
If we believe the exergy efficiency has any real effect on the total efficiency, the mod-con cannot exceed the efficiency of a CI boiler, which we know is not the situation.

Also, if we believe the exergy efficiency of a vacuum steam system, we find it is less efficient than a traditional steam system due to the lower boiling point.

So, this efficiency reduction must be negligible in the grand scheme of things otherwise your vacuum steam system wouldn't have a prayer of beating a traditional steam system.
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The Second Law of Thermodynamic is a fundamental law like gravity law and can't be circumvented. The exergetic efficiency (or efficiency by Second Law of Thermodynamic) is not a subject of personal preferences or believes, it's reality we should deal with.
This link is to a very good article about exergy
http://oaktrust.library.tamu.edu/bitstream/handle/1969.1/92450/ESL-IE-88-09-71.pdf
Ken Nelson, a prominent energy efficiency specialist, in real life, over 700 energy saving projects initiated by Nelson and his followers saved millions of dollars and produced on average 170- 340% ROI in 10 years period.

Yes, temperature of vapor in steam system is higher then vapor in vacuum system (so amount of heat per lb of vapor is higher) but

• boiler efficiency is lower
  
• heat distribution through the system is not even, building is overheated
  
• system heats up slower
  
• no control on vapor temperature
  
• no additional heat is sucked from the boiler after stop
  

izhadano

Hatterasguy said
Our "work analysis" and "enthalpy analysis" for the process would give very similar results.
===============================
In Nelson's article - p.399, Fig.4:
BOILER COMBUSTION EFFICIENCY =72.1% - steam@475 psi
(27.9% OF ABILITY TO DO WORK IS LOST)
There are additional losses in the boiler. When a 38OOoF
flame temperature is used to make steam at 950oF. over
15000 F of approach temperature is wasted. This is very
inefficient.
The remaining losses are small. Only 2.5% of the work is
lost up the stack. This compares with 15.7% heat loss
when enthalpy is used as the measurement.
===============================
If steam in boiler is produced at atmospheric pressure, the boiler combustion efficiency would be even less so the difference between "work analysis" and "enthalpy analysis" results would more significant.

izhadano

Hatterasguy said
We already know the combustion efficiency at atmospheric pressure in a residential steam boiler.
We also know the system efficiency if we know the heatloss.
So, if your analysis is anything close to accurate, we would be creating energy as the heatloss is greater than the boiler output at your supposed combustion efficiency.
The entire premise makes not a whit of sense.
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Please, note that the heat loss through chimney "we already know" is of low temperature/work potential. Real "work potential" loss happens in combustion chamber when heat of 3800oF used for heating water to 180-214oF, you don't see this through heat loss.
The heatloss is not equal to work loss (exergy loss), that's the reason of confusion.
We'd better stop comparing apples versus oranges.

izhadano

Dear Hatterasguy,
the exergy discussion started when I tried to explain why
"@gennady proved this with the steam system versus the mod-con. He's a bit shocked by it himself. A mod-con with a combustion efficiency of 90% beat the steam system by only 4%"
The explanation is - BTUs from boiler of any type should be tied to a temperature of supplied heat. The higher is supplied temperature the better, but the heat loss from chimney is also higher.
Hope, you agree on this.

Regarding energy savings of steam system converted into vacuum heating, - it's documented/verified in fuel gas savings and fuel bills, - not by utilizing an exergy comparison.
End of confusion?

Paul48

Can you point me to the huge advantage of vacuum in this table? I'm a novice, and can't see it.

https://armstronginternational.com/files/products/traps/pdf/N1_2~7.pdf

SWEI

Not enough information in that table. It's the combination of lower boiling point and increased steam velocity that makes it compelling.

Paul48

Over a properly vented system with TRV's?

jumper

Here's a straight forward way to think about exergy. You're burning expensive fuel to increase temperature of fluid in boiler AND to move that heat to rooms in building. Air in system requires more work to do the latter.

Non-condensibles like air make both boiling a fluid and condensing it more difficult.And more expensive.

Paul48

You get the steam to the radiators faster, but with less available btus. The slight increase you get in latent heat is offset by the increase in volume. All things being equal, at 10" of vacuum, you would have 50% more available heat with a convention system. Please correct me if I'm wrong.

AMservices

I for one can't wait to be installing Dr. Zhadanovsky's system.
If you think the numbers are impressive now, just think what the numbers will be like when he's not using leaking 100 years old pipe and the steam is traveling through well insulated polycarbonate pipe into a properly sized radiator, in a newly built home with air tight construction.
This is only the beginning. As old as steam heating is, it's still in its infancy, thinking about how much more it will continue to evolve from here.
And if your in pump sales, I wouldn't worry to much, not everyone will be able to convert their lousy, high maintenance mod-cons over night for a higher level of efficiency, vapor vacuum steam system.

ChrisJ

Honestly, for vacuum systems I really wish people would start using PSIA. 14.7 PSIA being 0 PSIG.

It'd make everything easier to understand.

Henry

The apartment complex that I was talking about with the one pipevacuum system. https://en.wikipedia.org/wiki/Linton_Apartments

izhadano

A "proper" one pipe steam system doesn't waste a lot of fuel and probably operates at close to 75% system efficiency. There is a fellow on here that compared two identical buildings.............one with steam and one with a new HW mod-con. The mod-con beat the steam building by 4% in fuel.
So, the question begs how this massive efficiency savings with vacuum is going to be obtained? I do not see it physically possible to save anything even close to 10% (as this would now be exceeding the combustion efficiency).
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Dear Hatterasguy:
Please, check Dan H. info on Paul system in “The Lost Art of Steam Heating”:
“I often wonder why we don't use Paul's ideas as a retrofit for today's older one-pipe systems. The fuel-savings documented in the old days were nearly 35 percent when the system was added to standard one-pipe”.

My system works in a higher vacuum, employs smaller diameter tubes and different control paradigm. Saying the truth, I expected better results but the results scale is similar (probably, because smaller system suffer less from uneven heat distribution).
Unfortunately, you have problem with those results.
Hopefully, with some luck the intricacies of vacuum heating system will be clarified in near future and I'm doing my best for testing and explaining new results. IMHO, exergy analysis is an invaluable tool to compare efficiency of different heating systems apples versus apples.
I might be wrong but it looks like your don't bother to look through the supplied references, especially exergy related. That makes the discussion difficult to continue.

izhadano

Hatterasguy said :
If the 43% was anything close to accurate, our fuel consumption figures would be nearly 2X the current usage. It's either that or the entire premise regarding our measurement of heatloss is fundamentally flawed.
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Sorry for delay in answering - quick and easy writing is not in my skill set.
Yes, I believe that entire premise regarding measurement of heatloss based on first law of Thermodynamics (not on the second law) is fundamentally flawed. And I'm not alone : “It’s amazing. Every year, we find somebody who comes up with a way of going around the second law (of Thermodynamics) and somehow convinces people who are very smart that it will work.” MIT lecture on Thermodynamics and & Kinetics, Spring 2008
Would you mind looking through this ppt
https://drive.google.com/open?id=0B-5hKw5FhaA4ckxnWGozczB3ZHc
It’s a great explanation of exergy and importance of exergy analysis. I can't do better. And if you still find the exergy concept of no value I’d better rest my case. No bad feelings.
Have a great weekend,
Igor

Steamhead

I highly doubt the Paul system (or any vacuum-based system) would have caught on unless it really did lower fuel consumption as advertised. Not sure where Dan got his figures, but knowing him, the source was reliable. So this is not a new discovery. Everything old is new again.

Dr. Igor is doing vital work for our industry, and for our country's energy consumption. When the project has progressed to where we can buy the equipment as a turn-key solution, i.e. "this type of system with this much radiation gets these components, and everything is guaranteed for X number of years" rather than putting everything together from scratch, our company will market it. At least in our customer base, the interest is definitely there.

Steamhead

Ahhh, but the increased ΔP from the vacuum did the same thing, as well as allowing lower steam temperatures. Sort of a one-two punch.

And remember, with those old coal-fired boilers, the steam only came up once a day. So the bulk of the savings would have been from lower steam temperatures.

Steamhead

We'll see. Dr. Z's results are quite encouraging. Our company has several buildings whose baselines are being established after our usual venting upgrades. When the vacuum equipment is ready as previously described, we'll get some therms-per-degree-day savings figures as we have before.

I predict that most of the early action will be in larger buildings- apartments and very large residences. If we can show a payback period of, say, 3-5 years or better, the upgrade will be a no-brainer.

Steamhead

Read my post again. I said:

Steamhead said:

Our company has several buildings whose baselines are being established after our usual venting upgrades.

This means, we've already done a venting upgrade to speed up the steam distribution and make the system as efficient as we can without using vacuum.

Then I said:

Steamhead said:

When the vacuum equipment is ready as previously described, we'll get some therms-per-degree-day savings figures as we have before.

This will establish what the benefits are of going to vacuum operation, over and above the now-standard venting upgrade.

Steamhead

You've completely missed the point, which is: that when buildings like I described are retrofitted to run with this vacuum setup after they were upgraded with modern venting, we will have a way to compare Dr. Z's vacuum technique with simply upgrading the venting. We will know how much fuel those buildings used, on a therms-per-degree-day basis, before any work was done; we will know the effect the venting upgrade had (which in one case was good for a 1/3 reduction in fuel consumption, not chump change by any standard- see our Find a Contractor ad for more); and we will know what effect the vacuum upgrade had.

In this case, the building's heat loss does not play any part. In fact, changing the heat loss and/or the system's capacity would completely muddy the waters. Why? Because it would introduce another variable. In any truly scientific comparison, it is essential to eliminate any and all variables other than the one you are studying.

The question of the building's heat loss and how closely the heating system matches that heat loss is entirely separate from upgrading to vacuum operation. I'm not saying it doesn't matter in the total picture, but we're not looking at the total picture just yet.

SWEI

Assuming the interior temperatures are the same, it's actually a pretty decent experimental protocol IMO.

Steamhead

Hatterasguy said:

BTU/DD/square foot is not a measure of efficiency.

Actually, it is. It is a measure of how efficient the building is. The heating system is but one part of the building's efficiency picture.

Hatterasguy said:

The heatloss of the building is critical and absolutely necessary.

No one is denying that. But in this thread, we are discussing “Vacuum Boost” for steam heating system. If you want to discuss how the heat loss figures into the total picture, maybe you should start another thread.

SWEI

Hatterasguy said:

The only way to determine the efficiency of the heating system is to know the heatloss of the building.

Otherwise you are simply comparing two data points.

He's not trying to determine the efficiency of the heating system. He's trying to learn what, if any improvement a vacuum boost does over a properly balanced and vented conventional system.

Steamhead

Hatterasguy said:

The maximum potential that exists (unless Igor rewrites the First law) is the difference between the current system efficiency and the combustion efficiency. We ought to know that value before the test begins.

That's where the bottom drops out of your argument. This thread does not address the efficiency of the boiler or the building's heat loss. It is concerned solely with the effects of one particular modification to a building's heat-distribution system. And, as I've said before, no one denies that there are other factors that go into the total efficiency picture. But this thread is concerned with just the one change.

Can you come up with a better way to gauge the effect of this one modification, i.e. adding vacuum to a building's steam distribution system?

Can you?

SWEI

If the normalized fuel use decreases more than a small amount after the vacuum retrofit, then it would appear the original (properly vented, balanced, and controlled) steam system was less efficient than had been assumed.

The most detailed heat loss calcs still include quite a bit of headroom.

Guess we'll just have to wait and see. I for one am looking forward to the data.

Steamhead

The "starting point" is the status of the system before we started working on it, as outlined earlier. The question was, what effect does adding vacuum to a system have, and how does that compare to just upgrading the venting?

Earlier I said:

when buildings like I described are retrofitted to run with this vacuum setup after they were upgraded with modern venting, we will have a way to compare Dr. Z's vacuum technique with simply upgrading the venting. We will know how much fuel those buildings used, on a therms-per-degree-day basis, before any work was done; we will know the effect the venting upgrade had (which in one case was good for a 1/3 reduction in fuel consumption, not chump change by any standard- see our Find a Contractor ad for more); and we will know what effect the vacuum upgrade had.

It's actually pretty simple. We are attempting to answer three questions:

1- How much fuel did the building use on a therms-per-degree-day basis before we started working on the steam system? This is the "baseline".

2- How much fuel did we save, relative to the baseline cited in #1 above, by upgrading the air venting to modern standards?

3- This is a two-part question: a- How much fuel did we save, relative to the baseline cited in #1 above, by upgrading to vacuum? b- How does this compare to the amount of fuel saved in #2 above?

Ir's just that simple. These are the questions, and I've described how I will find the answers. We have a baseline and two courses of action which we know will reduce the building's fuel consumption relative to that baseline. And the results are, or should be, repeatable.

Steamhead

Based on the vacuum setups I've seen so far, it may or may not short-cycle. Most of the larger boilers can be run low-high-low, often by a control upgrade if not already set up that way. We'll see.

And it may be that a properly vented steam system is "close" to the efficiency of a mod-con, but a vacuumized system can equal it. Again, we'll see.

ChrisJ

24" HG (2.8 PSIA) will get you to 140F.
Not very hard to achieve with a tight system.

ChrisJ

Hatterasguy said:

ChrisJ said:

24" HG (2.8 PSIA) will get you to 140F.
Not very hard to achieve with a tight system.

Very hard to achieve and maintain on a typical steam system with threaded joints and radiator valves.

You're saying NPT threaded black iron and brass valves cannot handle a 12 PSI pressure differential?

While I agree old radiator valve packing may not be up to the task that can be rectified.

We're talking about a vacuum of about 120,000 microns.

gerry gill

what a pissing contest. All i know is the old timers would not have used vacuum if it didn't reduce fuel usage.

Steamhead

I said the same thing earlier, but it didn't register...........

ChrisJ

Hatterasguy said:

gerry gill said:

what a pissing contest. All i know is the old timers would not have used vacuum if it didn't reduce fuel usage.

All I know is that if a vacuum system was that fantastic at reducing fuel usage, you'd still see it offered today. Try and find one that was installed in the last 10 years. There has to be a reason for that.

That's your argument?

Steamhead

Hatterasguy said:

Steamhead said:

I said the same thing earlier, but it didn't register...........

Sure you said it.

But without a baseline for comparison, there is no way to calculate the savings.

I guess I have to repeat it again:

Compare a vacuum system to an old one pipe with undersized NBP and little to no main venting and you get a fantastic result.

Compare a vacuum system to a modern one pipe with a large drop header and massive main venting and you most likely cannot get much more out of that.

Do you have drop headers and exceptionally dry steam on the buildings for which you intend to perform this comparison? If not, your baseline is lower and your vacuum system will look much better.

See the difference?

The devil is in the details of the existing system and the total current fuel efficiency of that system would let the devil out.

There you go again- it didn't register.

We are not talking about several different buildings here.

We are talking about modifications to one system at a time. How does changing the air elimination and operating pressure or vacuum on a given system, affect its fuel consumption?

And why would the Dead Men have spent the extra money to produce vacuum if it didn't lower a system's fuel consumption?

hvacfreak2

Whatever that heat loss number is , so long as it does not change within the time period of the testing for either system configuration , is not a factor for the comparison being discussed. ( dead horse sorry )

I believe that a good point has been mentioned however , where will this dramatic savings come from ? The beniefit of vacuum showed on low fire conditions , as the coal fire went low. The coal fire burn cycle lasted all day ( or weeks or months ) , not on / off 20 minute cycles like we operate.

But it is neat stuff , and if this shows something barely marginal I'm in.

Gordy

Interesting debate.
I have a question.

Igor used panel rads in his conversion. In panel rads verses standard CI steam rads. Panel rads I would think have a faster response time, and take advantage of lower steam temps in a vacuum system verses a standard CI steam rad.

Any data on this?
It certainly adds to efficiency of the system. Vacuum equals quicker time steam gets to rads. High output panel rads equals shorter emitter heat up, and faster delivery of btus to the space.

Faster delivery of btus to the space equals shorter time for space to heat up, and be satisfied. This equals shorter system run times.

This one emitter component change can heavily impact results in my opinion.

Gordy

I'm not saying one way, or the other.......yet.

The question becomes reaction time of the total system. Yes CI rads are slow to heat up, and slow to release btus. The lower the delivery temp of media choosen the more extended this cycle becomes.
However the question becomes in the slow release of the btus are they still needed? The space has already reached setpoint in the cycle. So the slow cool down of a CI rad either contributes to an over shoot of the space, or off sets the heat loss of the space during its cool down period. The chances of the latter equaling the loss of the space is a crap shoot. If it ends up as an over shoot its wasted energy.

Gordy

I guess the data I seek is the output of steam panel rads at various steam temps. If such data exists like panel rads for HW.

Gordy

I will add the luxury of old CI radiation in a HW setup is their over sizing either do by chance to installer error, or upgrades to the envelope. This allows for lower SWT to gain efficiency. The same has to apply to steam. If one of the goals of a vacuum system is to be able to lower the delivery temperature of the steam. Also if lowered steam temp gains admirable efficiency points.

Gordy

I look at it like this. The boiler, and system is most efficient when it is off. If it takes 20 min. To heat up a CI rad to make set point, or 10 min. To heat up a panel rad to make setpoint, and both are using the same temp steam which one will add more efficiency.

Gordy

So let's say the starting point is a very inefficient decrepit steam system.

A first step conventional improvement is to make sure the delivery system is as good as it possibly can be. Venting, piping etc.

Second improvement would be a more efficient boiler. If one is not already in place.

Third improvement would be to put a vacuum system in place to speed up delivery, and lower the temp of the steam.

Forth improvement would be to further increase response time to faster responding panel rads.

I suppose other efficiency improvements would be zoning, and trvs.

To calculate total efficiency increase of each improvement would be to start from original static system with each improvement.

Or you can base each efficiency increase per improvement off the previous improvement changes. This breaks down each change increase in efficiency over the last.

Obviously the most stellar improvement percentages would all be based off original system conditions.