Compressors Air cooling
In the case of small single stage compressors, natural air cooling may be sufficient using finned cylinders. The performance of such a compressor can be expected to vary with changes in the ambient temperature, as the effectiveness of the cooling varies with the difference in temperature between the cylinder and the ambient. Forced draft cooling is to be preferred, generated by an engine driven fan or from a power take-off on the compressor shaft, as this can provide more effective heat dissipation and more consistent heat transfer. If the compressor is located in a warm atmosphere it may be advantageous to draw the cooling air from a lower temperature source, eg through ducting led to the outside of the building. The amount of cooling required by a compressor is higher than that considered optimum for an internal combustion engine. The aim is to lower the compressor temperature as far as possible rather than to maintain it at an efficient running temperature as in the case of an engine.
Forced draft air cooling may be adequate for both small and large compressors, particularly if the latter are low capacity or multi-stage machines. For the latter, the increase in temperature per stage is lower than that of a single-stage machine of the same pressure ratio. Air cooling has its limitations when the compressor has a high capacity and is run continuously.