Selection of Compressor

Which manufacturers have been approached, and what equipment rejected for what reasons?

@pwslack....actually i haven't approached any manufacture till date. I just want to make sure myself what possible options are there for my requirements. my most imp. criterion is low inlet temp. around 60-70 'C.

You say pressure rise is low, but that could mean anything, specially at inlet pressure 80 bar. You need to specify required pressure rise to enable supplier to make recommendation.

Cheers.........Codey

@codemaster...actually helium will be running through closed loop so the pressure will be remain same. i have finalized 1-stage centrifugal compressor due to its good part load performance under varying mass flow rate for my requirement but not sure. will it be fine?

for a single stage machine assuming a pressure rise of 1 bar from inlet to outlet and using maximum throughput of 1.8 kg/s you could look at a single little impeller of around 5" running at around 20,000 rpm. If you assume an efficiency of around 75% you will then need a motor of about 28 kW.

Look up Sundyne LMC compressor - not cheep but.

@guest...hi, thanks for providing the info.Can u explain me how do u approach the calculation for power input of compressor?

As there's no reply so far to this, I'll tell you how I do it.

Power to compress the gas W = P₁*Q₁/n*((P₂/P₁)ⁿ - 1)

Where P₁ = inlet pressure, P₂ = outlet pressure, Q₁ = inlet flow, n = polytropic exponent, usual value 0.23. All in SI units of course, to get answer in watt. To work out inlet flow, don't forget that at 81 bara, density is about 81 x greater than value at std conditions.

To get compressor shaft power, divide by compressor efficiency, typically 65%.

I work that out to about 21 kW, rather lower than guest #5, but he may be right. 80 barg inlet pressure is a bit unusual. The compressor supplier will give you a figure. You might let us know what he says. Also the 1 bar pressure rise is a shot in the dark.

Cheers.........Codey

Sorry, I plead guilty to being Guest #5 and for not responding - thanks for doing so.

Nothing wrong with your power estimate I don't think. I looked at installed power which gives some margin over actual gas power - also not sure what assumptions you made with regard to discharge pressure.

Apart from what you have explained, I got the rpm and impeller size by assuming some typical values for Mach # around 0.95, Speed coefficient somewhere between 0.2 and 0.3 and head coefficient around 0.4 to 0.55. These could be way out. However, they come from the Demag compressor selection literature and are good enough to get some idea of what type of machine you are looking at.

Next step is the OEM and the specifics.

Hello Kaisan

Thanks for that. I used inlet pressure 80 barg, ΔP 1 bar, discharge pressure 81 barg.

Cheers.........Codey

Even on a closed loop system there must be a pressure drop round the system and an equal pressure rise across the compressor. If there's no pressure drop you don't need a compressor. Depending on the actual duty I don't see why a 1-stage centrifugal compressor shouldn't be OK, but I'm not an expert on selection.

Cheers..........Codey