Compressor Power Consumption Ratio

When using a compressor what you want is compresser air and what you need to put in is mechanical energy. So how do you define what you have termed "Consumption Ratio" ? In general the compression process will be near adiabatic and so in addition to pressurising the air its temperature too will be increased. Unfortunately when pressurised air is stored in a tank this heat will leak away and so you end up with far less energy than you put in. If the compression could be more isothermal (at constant temperature) you need to do less work to achieve the same end. This is what multistage compression with inter-coolers try to do.

Hi,

When lecturing at an agricultural engineering college some years ago I set up a lab. experiment for the students which used a 10 hp compressor with a 250 litre receiver.

We measured the amps and time to fill the receiver and therefore we could establish a power consumption and a stored energy figure so could measure how much power was available for work to be done. This was two stage piston compressor and the efficency is awlful, somewhere around 25% if my memory serves me right.

Compressing a gas is fraught with losses both mechanical and partciularly heat loss due to the compression process. Air certainly is not cheap.

Regards

Oliver Dunthorne