District heating in Russia

Christian Egli

I like your compared steam and water 10 inch pipe

But don't forget, steam only needs one 10 inch pipe, while water will need a return too, so technically we should derate the hot water numbers by one half.

To answer your question, here is what I think.

Steam generates its own pressure at the boiler, it is also what makes with so little cost. Pressurized water is not left on its own, if so it would turn to steam. The pressure in a hot water system is artificially created with a pump, just high enough to make sure that no steam will appear anywhere in the system. It follows that even when the water cools, the pressure in the system does not drop.

Water does not move on its own, for that there are circulators that develop a head. In relation to this there is a drop in head along the sytem.

In practice, district systems on water use a lot of pumping stations and also a lot of heat exchangers. I have not heard of district sytems that rely on gravtiy.

Tony Conner

At...

... 75 PSIG you can get about 5,000 #/hr steam through a 4" line, on 100 or 150 feet or so of run. A huge number of steam systems have boilers with safety valves that lift at 150 PSIG. They'll typically maintain header pressures of 125 PSIG. You can stuff 120,000 #/hr down a 12" line under those conditions. On most steam systems with long (as in several city blocks), the pressure drops become a factor before velocity. On the mains under the streets (and most industrial applications), you can take velocities that result in noise that would cause complaints in buildings like apartments or offices. Steam is limited as to how far you can push it out from the central plant. A mile or so is usually about it. Hot water, on the other hand, can be pumped for 20 or 30 miles. Hot water systems have to buy, operate and maintain pumps, while steam systems don't. On the other hand, hot water boilers usually have slightly lower stack temps, and higher efficiencies.

I know of one hot water system that operates at about 420*F. This is close to steam temps at 300 PSIG. The system has big expansion tanks with 350 PSIG of nitrogen in them to make sure that the water STAYS water. You can have some pretty exciting water hammer events in high temp hot water systems where the pressure falls enough to let some of this water start flashing into steam.

Clif Heeney_2

District Heating In Estonia, Part II

Hi Dan and all Wallies,

Maybe you would like to travel here and while visiting the best preserved medieval city in northern Europe, we could go visit one of the district heating plants. What say you?

If you are interested in seeing some of what the original part of Tallinn looks like, what we call Old Town, go to http://www.tallinn.info/html/

You asked about life in Estonia and how I came to live here. Life here is good, we have made tremendous progress as a nation since independence came in 1991. Progress both economically as well as technologically. We have very high penetration rates concerning mobile phone usage as well as internet access -- with every school in our nation having broadband internet access. Economically we are without a doubt the most transformed and the most progressive of all the former republics of the USSR. We recently we admitted into NATO and on 1 May joined the European Union.

I have had several careers during my life, including holding a plumbing license from Washington State. In 1994 I began my university time of life -- at age 40. I graduated in 1998 with double majors (B.A.) in Biblical Studies and Biblical Counseling. To make a very long story short, I ended up in Tallinn, Estonia serving as a missionary. This is home for me and my wife who is Estonian, and our two small children. Thanks for asking!

DanHolohan

Lovely place!

Maybe we should have a Wetstock there.

It's it wonderful where life takes us?

Clif Heeney_2

Wetstock in Estonia

Sounds like a GREAT idea to me Dan!! The only question is timing -- When would you like to set it up??

Less than two years ago I was working towards replacing the old Soviet era coal-fired boiler, in the multi-use building where we live, with a gas boiler. I asked some questions on The Wall which were quickly answered. I also asked you how to obtain a copy of the Heat Loss Calculator by Slant Fin. You graciously sent me a copy of that program at your expense. Thanks again for sending it to me! Anyway, when Wetstock comes to Estonia (isn't that a great idea, even though it will probably never happen), we can have a tour here at the house and see the new boiler and photos of the old one.

If there is anything that I can do for you, PLEASE let me know!! Abundant GRACE to you!

Aidan (UK)

Somewhere on the web

Somewhere on the web, there are reports published by the US Army Corps of Engineers, heavy-duty academic stuff. One of them compared the overall fuel efficiency and maintenance costs of some large army bases with centralized boiler plant and district heating systems, i.e., steam, HTHW, MTHW & LTHW. The recommendations were in favour of LTHW, if I recall it correctly. The standing losses and maintenance costs were lower.

Using HP steam for space heating, via heat exchangers, is redundant technology. Pumps have become cheaper and more reliable, so steam heat distribution has lost it's main advantage (no pumps). In the UK, the Pressure System Regulations impose serious inspection, maintenance and insurance cost penalties on anything operating at 100degC or more. Most large institutions had centralized coal-fired steam boiler plants in the 60s. These have mostly been replaced with de-centralized gas-fired (North Sea gas) LTHW boiler plants. The emissions and acid-rain problems made coal fired plant impractical for everything other than large power stations with flue-gas cleaning plant.