Compressed Air 1

[rguil]

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?

 

[ChasBean1]

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.

 

[quark]

rguil!

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.

 

[borjame]

It would depend on if the compressor inlet is open to the environment(ambient).

 

[omer2000]

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.

 

yes we can do that but must take in our consider the tempruter and end in the firest stage must cooled to ambent tep-and keep the pressure not change

 

[omer2000]

please sewafy why we need to cool the outlet temp of first stage to ambient temp. it is coastly and need a big condenser and a big quqntity of colant

 

[TD2K]

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.

 

[omer2000]

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

 

[mucour]

It is traditional in compressor sizing to limit the maximum temperature to 150deg C.

The reasons cited are metallurgical, lubrication and efficiency factors.

So connecting the compressed air into the inlet of another compressor muct be checked for the temperature of the compressed gas.

 

[TD2K]

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.