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Hi all. First post! (besides saying "hi" in the nubie section)
We have a few sites where lowering the head pressure in lower ambients would be very benificial for saving ebergy but going too low may cause problems by starving the liquid injection oil cooling. Has anyone tried using a liquid pressure boost pump to over-come this limitation? This refers to NH3 screw compressors of different manufactures and sizes.
Brad
Hi Brad,
Welcome aboard.
You have a couple of options.
One; is to use a positive displacement pump to provide the necassary liquid injection pressure, or
Two, use a different liquid injection valve that has an acceptable range of operation that will work.
The simpler approach would be to use a different valve. That would eliminate any potential pump problems and higher costs.
I believe that we discussed this liquid pump application on another thread.
My fear of replacing just the valve was that when conditions changed (Summer/Winter), and the head pressure climbed the TX valve would be oversize and prone to hunting. The plant I am thinking of has a Condenser that is oversize in Winter and sufficient in Summer. Seasonal variation goes from subzero to 80F (If one fan fails the head could climb. At the moment they are operating with no water on the Evap due to the outside temperature.
Perhaps something other than the standard Sporlan Valve would be better?
Hi:)
you could fit the new Danfoss ICM:D
Kind Regards Andy:)
I have used dual liquid injection valves on machines with extreme condnesing pressure swings. Use a condensing pressure sensor to determine which TXV to use. You can also pipe the TXV's into different injection ports.
As an alternate, you can upgrade to an electronic TXV by Danfoss which has a much larger control range.
Ken
Thanks for the quick responese!
The reason that I was leaning toward a liquid pump is that these machines range from newer FES and Mycoms to older Sullairs and I thought retrofitting them with newer valves might be an issue. The other concern is the cost of retrofits as some of these plants have 10 or more compressors.
Brad
Andy and US iceman as usual have great ideas!
We discussed the Danfoss motorized valve on another thread. http://www.refrigeration-engineer.co...4147#post54147
We are waiting to see how the Danfoss motorized valve works out on the new machine we are going to install before deciding which way to go in the other plant I referred to.
Having as many compressors in one plant may well make the Liquid Pump more cost effective after you consider installation costs.
One thing you might consider is talking to FES. They provide us with a lot of help with other people's machines as well as their own. They recently helped us pick the pieces for a recent conversion of a thermosyphon to liquid injection on a a Stahl.
As for using dual valves it is a idea I have never seen but will remember for the future.
Interesting, I talked to two other people here in NB Canada and they both suggested FES as a good resource. Thanks againQuote:
One thing you might consider is talking to FES.
Brad