If I direct compressed air to the inlet of a compressor, would I expect a benefit because of a higher inlet presssure or would it be at ambient pressure since it is released? I beleive I am asking the correct forum?
Depends on how you direct it. If you pressurize the inlet, the amount of work needed by the compressor will indeed be less. If you are using the outlet of Compressor #1 to feed the inlet of Compressor #1, that is not the case.
That is what is called two stage (or any) compression, in which air (or any gas) is compressed initially to certain pressure, cooled down and again compressed to the required pressure. For optimum energy consumption the ideal intermediate pressure should be sqrt(p1*p2). Both pressures are absolute values.
The mechanical strength of the two stages are designed as per the pressures. You cannot put high pressure air on lower stage compressor.
Note: You have to take care not to expand the air before entering the cylinder.
Regards,
Truth: Even the hardest of the problems will have atleast one simple solution. Mine may not be one.
omer2000
i am agree with above anseer for design of two stage compressor but if we used two compressors in series we shoulld put in our mained what is recmended inlet temp. and max. inlet pressur for 2nd comp.
Omer, cooling the interstage gas is typically done to reduce the compressor Hp requirements (eg. it takes more power to compress a hot gas from P1 to P2 than a cool gas) and/or to prevent excessive discharge temperatures from the next stage.
TD2K,i,am agree for the importance of cooling inter stage pressur but my note is why for ambient temp.? many desigens of inter stage over ambient temp.about 20c
thanks
Omer, I'm not sure what you mean about cooling to ambient.
What can you can cool the first stage gas to is dependent on your cooling medium and how close of an approach you want to design your cooler for be it air, water or some other medium. The closer an approach, the more area you need but you save on compressor Hp, it's a trade-off.
For air coolers, 10C approach is a common lower limit, 20C would not seem unrealistic. If someone is trying to tell you they need the interstage gas cooled to ambient air temperatures using an air cooler (and I'm guessing this from your post), they don't know what they are talking about. It's impossible.