Reciprocating Air Compressor

MECHCHIC

The definition of mechanical efficiency of a reciprocating air compressor is as follows:

It is a measure of the power lost due to mechanical friction, as in the bearings, ect., not including air friction. It is the ratio of the power consumed in the compressor cylinders, shown on indicator cards, to the power delivered to the shaft of power driven compressors, i.e., the b.h.p., or to the power applied in the steam cylinders of a steam driven machine, i.e, the i.h.p. in the steam cylinders.

Hope this helps,

Best regards,

N6377B

Since you are writing a REPORT, it may perhaps be useful to deal the subject in detail.

Efficiency – Any reference to efficiency must be accompanied by a qualifying statement which identifies the efficiency under consideration, as in the following definitions of efficiency:

Efficiency, Compression - Ratio of theoretical power to power actually imparted to the air or gas delivered by the compressor.

Efficiency, Isothermal - Ratio of the theoretical work (as calculated on a isothermal basis) to the actual work transferred to a gas during compression.

Efficiency, Mechanical - Ratio of power imparted to the air or gas to brake horsepower (bhp).

Efficiency, Polytropic – Ratio of the polytropic compression energy transferred to the gas, to the actual energy transferred to the gas.

Efficiency, Volumetric - Ratio of actual capacity to piston displacement

Simplistically the efficiency is the ratio of power output to power input.

You need to decide where to 'start' for input (electric, steam, petrol, diesel, etc) and whether you want to take the efficiency of prime-mover into account.

Then there is the actual efficiency of the compressor itself (shaft input) to drive ancillary equipment (friction, windage, oil pumps, inter-coolers, after-coolers, etc) compared the power transferred to the compressed air - which depends on the thermodynamic efficiency of compression process.

The latter will depend on the design of the compressor and what you want the air for.

There are standard thermodynamic formulae for various compression processes - as applicable to perfect gasses - of which atmosheric air is not - due to water vapour - and then contamination by oil.

Sorry my reply does not give a direct answer, but it gives you enough ammo to explain why you 'lab results' might be nothing like predicted by theory.