Spray nozzle pressure going into direct contact condenser

[newzeadan]

Hello,

I am working on a direct contact condenser design, and have a differing opinion with a colleague. They want the pressure coming out of the water spray nozzle to be equal to condenser pressure (.6psia). Since this is on a fresh water line they are putting in a pressure reducing valve upstream of our water control valve in order to obtain the correct pressure to achieve this.

Now that may be correct, but I am wondering, will it have any effect on the condenser vacuum or anything else, to come out of the nozzle with a bit of extra pressure? I would think extra pressure would be needed to get a good spray pattern out of our nozzle?

So, say we have 50 psig on the water line, and a 5 psig drop through spray nozzle. We are .6psia on the condenser, so he wants pressure upstream of nozzle to be like 6 psia. would it matter if we were say 10psig upstream of nozzle? Even if you take the vacuum out of the equation and just look at simple pipe of 4 in dia, expanding into a 36in dia (condenser), your pressure is going to decrease dramatically, so I would think the extra pressure would be negligible to the vacuum?

Any help is appreciated!

Thanks,

Dan

 

[Lnewqban]

This is a dynamic problem where two very different masses get mixed per unit of time.
Pressure inside the pipe only moves the drops of water into the air stream and has little to do with the pressure of the air.
The key to keep the proper vacuum is the rate at which the mass of condensate is sucked from the condenser.

"Where the spirit does not work with the hand, there is no art." - Leonardo da Vinci

 

[newzeadan]

That makes sense, and I guess the concern they have is that if discharge of the nozzle is not the same as the condenser pressure, the butterfly valve upstream of it all will cavitate.

His scenario is as follows: water pressure at 50psig. Takes a 20psig drop through control valve, so we now have 30psig water to spray nozzle. We have 5psig drop (calculated) through spray nozzle. Condenser is at say .7psia, and we have water at 25psig at nozzle outlet.

This is where I have trouble. What happens to excess pressure? Will it translate through pipe and make control valve cavitate to achieve the drop or is it dissipated in the condenser?

Or is it something completely different?

Thanks

Dan

 

[MikeHalloran]

I once saw a direct contact condenser that was disassembled for maintenance.
I was very impressed by the mirror finish inside that giant venturi.
I still have no idea how it works.



Mike Halloran
Pembroke Pines, FL, USA

 

[Lnewqban]

This is where I have trouble. What happens to excess pressure? Will it translate through pipe and make control valve cavitate to achieve the drop or is it dissipated in the condenser?

I see no reason for any cavitation upstream the condenser; the downstream condensate pump could cavitate, but you should be able to calculate that.

I have assumed that you have been referring to a spray-type direct contact condenser (steam-water).

"Where the spirit does not work with the hand, there is no art." - Leonardo da Vinci