Properties of Air Leaving a Hydraulic Air Compressor (HAC)

An analysis is made of the diffusion-rate-controlled absorption of air into the water in the two-phase flow processes occurring in a hydraulic air compressor (HAC). The analysis enables calculation of the fraction of air absorbed, when implemented as an addition to an earlier computerized model for the flow in an HAC, which did not account for air absorption. Furthermore, the calculations account for oxygen and nitrogen absorption separately, and thus allow determination of the mole fraction of oxygen in the compressed air. Excellent agreement was found for the calculated results when compared with a single point of experimental data from a large, old HAC. It was found that the efficiency of low-head HAC is greatly decreased by the air absorption phenomena, while the efficiency of higher-head HAC is much less affected.