Non-Thermostatic Vacuum Vents?

jumper

Harry said:

On the matter of naming boilers: At a previous employer's we had two 300 ton Lithium-Bromide absorption chillers we named "Miss Jessie" and "Miss Bessie," after two elderly cleaning ladies who used to work in the building. It's not just boilers!

Those lithium machines operate under REAL vacuum. I read that Carrier tried using the chilled water directly without a heat exchanger before WWII. Must have been a really tight system. And the machine would have to be at high point. Those machines are heavy.

jumper

Harry said:

Even our air conditioning was steam driven, since we used Lithium-Bromide absorption chillers to cool the water that ran to our air washers. No coils for the a/c, all water sprays with dew point humidity control. They cleaned the air, cooled it, dehumidified, and in the winter, humidified.

Do you remember what water temperature you used to cool & dehumidify?

Unless you require quite low temperature or your steam is very low pressure steamjet refrigeration is more economical and reliable than lithium.

Harry_6

We couldn't have used steam jet since the engine room was below an exit vestibule adjacent to the auditorium, so noise was an issue. And absorbers are quiet. Also, we only had about 50 PSI if steam, and that's a bit too low. The absorbers were on a basement floor, so their weight wasn't an issue. And, yes, they required a vacuum of around 6mm of mercury to run. You can imagine, the water has to be able to boil into steam at 45 degrees! Absorbers are kind of a black art, since everything happens with liquids flowing over tubes and baffles and trays, all out of sight inside. You have to rely on thermometers at all the important points in the system, and after a while you can tell what's going on inside by laying hands on the shell to feel temperatures, or seeing if portions of it sweat while running. Old absorber guys are worth their weight in gold. I knew one who could tell by the sound and temperatures on the shell what the Bromide concentration was. He used to work in R&D at Carrier many years ago.

As for the air washers, they would take any temperature water, as long as it was still liquid. Unlike the original CO2 compressors, which chilled coils in a Baudelot cooler (look it up), the absorber had a design temperature of 44 degrees for rated capacity. If you started to lower the water temp below design, the chiller capacity decreased. As with all things, a trade-off. We tended to run at a set point of 42 degrees, but if we weren't keeping up, it would rise until system equilibrium was reached. With air washers, the colder the water, the more efficient the dehumidification effect. The Baudelot coolers could have made water at 32 degrees, as long as you kept it moving, and boy, would that have worked! But typically even the original operators ran at around 45-50 degrees. The lower the temp, the lower the tonnage.

But the best thing about the plant was that you could redirect cooling capacity to where it was needed. If the auditorium wasn't keeping up, we could shut the lobby down and steal its capacity, as all the chilled water was stored in a central tank and drawn off by the air washer pumps as needed. On one occasion a celeb was doing signings in the lobby and wanted it as cold as possible. We shut down the auditorium and doubled the pressure to the lobby washer (more PSI, more GPM, more BTUs), allowing us to apply something like 325 GPM at 42 degrees to the lobby system. You could have stored meat in there.

Because the system allowed us to separately control the auditorium and lobby systems, with only the main floor foyer as an area where they overlapped, I always wanted to try warming and humidifying one, while chilling and dehumidifying the other to see if I could make fog in the foyer. Never got around to trying it, but technically possible!



Didn't have any engine room pictures on this computer, but here are a couple of the auditorium and lobby. "Retired" now, but still miss it.

jumper

Important feature of air washer is no coil to foul. Later compact air washers were available.

What did you use those Nash pumps for,Harry?

Harry_6

Along with the 5,000 seat theatre we had a ten-story office building. The office building was originally heated with under-window radiators. One duplex Nash pump pulled vacuum for that system. The theatre is heated by radiators in vestibules and in the dressing rooms, but the public areas are heated by means of big steam coils (originally Aerofins) in the ventilation fan rooms adjacent to the air washers. There are preheaters to keep the air washers from freezing in the winter, and reheaters to adjust the outgoing air temp based on return air temp., and to lower the high humidity of the outgoing air washer air. All controlled by 1928 Johnson pneumatic thermostats. We also had some small booster coils on the lobby system to aid during those times in the winter when the front doors were wide open. The second duplex Nash pump (the big one) maintains vacuum on that system. There are three steam zones (lobby, auditorium, perimeter) which we typically ran at about 5" vacuum on the mains, although in very cold weather we might go up to 2 PSI. Steam is purchased from a downtown utility and supplied at about 50 PSI, which we use PRVs to drop to operating pressure. So, no boilers there. That's the way the place was built in 1928.

ratio

Thanks for the pics, @Harry. They don't make 'em like that any more, do they.

jumper

Those older set ups are so interesting @Harry. Thank you for sharing the knowledge. When the radiant was under vacuum how was the condensate expelled? 5" vacuum required pretty deep hotwell?

Harry_6

I should also have mentioned that the absorbers did not use vacuum, but operated at 0-15 PSI, depending on load.

As for expelling the condensate, the Nash pumps have a return accumulator tank, which is under vacuum, and from which the pumps draw both water and air. The pumps discharge water at a positive pressure of something like 30 PSI. Interestingly, the condensate then travelled to an economizer for the domestic water heating system, so that the hot water for sinks, etc. could be preheated (minimizing the need for steam water heating, which made up the difference), while cooling the condensate, which then ran through a meter and was sent down the drain. Detroit Edison long ago determined that, a) they couldn't measure steam flow for billing purposes, but they could measure condensate, and, b) it wasn't worth all the additional infrastructure to send the condensate back to the power plant, except in the case of the very largest consumers. Thus, they didn't add boiler chemicals, they just distilled the heck out of their feed water before using it. No chemicals. So down the drain it goes.

In recent years, what with technological "advancements," they have been retrofitting steam flow meters to the old systems, which were rife with cheaters installing hidden piping to reroute some of their condensate around the condensate meter. In a pipe space two-thirds of the way up a thirty-five story building I once found copper lines installed to take the condensate from every other riser in the upper ten floors of the building and route it into a roof drain pipe. People.