Water pumping in tall buildings ?

[Cliff_J]

Ok, read the solar tower stuff in a couple threads here, and the complexity of pumping water to great heights in terms of pumping losses and pipe requirements surpized me. So, thinking about the skyscraper express elevator/floor elevator setup like the WTC had seems applicable to water.

Obviously we can calculate (and govt regulated) on how much pressure and piping we need to pump water a given amount, say 40 stories but to get to 80 or 120 stories, our requirements would normally change by some square or cube factor. But what if like the express elevator the orignal 40 stories pumped into a collection pool, and then we repumped the next 40 stories and so on. Would our original 40 story requirements be sufficient for each additional 40 story step?

Sure our efficiency is lower since we have so many repetitive pumping steps, but leaving that aside wouldn't this lower the piping requirements tremendously and also have some small efficiency recovery in the lower pumping pressures needed?

Cliff

 

[Artman]

Yes. this is one way to overcome the tremendous water pressure of tall buildings. Everytime there is an air break, the pressure requirements are renewed, so the only static head is from the water directly above to the next pool above. This solves the pressure restrictions on the piping and pumps, however, it will still require as much or more horsepower to lift the amount of water required to the top of the tower.

 

[NateTG]

You can just put a pump inline every 40 stories, or whatever. There really isn't much need for a collection pool unless you need one for efficiency/pressure reasons.

This type of problem is much more interesting in deep mines where the height difference (and consequences of failure) can be a good lot more spectacular. Some mines are more than a mile deep, which is a good sight more height difference than buildings provide.

 

[Cliff_J]

Ok, so an inline pump accomplishes the same because its all about the pressure gain from the pump that could be designed so each pump/pipe only supports a column of water X feet tall then. And here I thought fluid mechanics was tough...

Yes, the mine thing is quite amazing, and I forgot that mining was the impetus for steam engines and horsepower and what not. Astoundingly, I can't believe what was accomplished before the 20th century's knowledge and technology expansions. And the danger level is unreal to me - one of the History channel shows on man-made disasters showed footage of a salt mine under a lake that was accidentally drilled by an oil company. Wow!

Cliff

 

[Artman]

Actually, it's the check valves on the pump discharges that allow this arrangement to work. Otherwise, should the intermediate pumps be off for some reason the full static pressure of the column of water would rest on the bottom pump and pipe system.