Abstract: The water-lubricated twin-screw air compressor has attracted wide attention because it can provide absolutely oil-free clean air. In order to study the heat and mass transfer characteristics of the water-lubricated twin-screw air compressor, a working process model considering the flow, heat and mass transfer of dry air, water vapor and liquid water is established, and the calculated results are verified by the experimental data from the perspective of p-V diagrams. By comparison, it can be found that the simulation results are in good agreement with the experimental results, and then the heat and mass transfer characteristics of three-phase fluids are studied. The results show that a large amount of water injected into the rotor cavity still does not achieve the full heat exchange with the wet air, so that the wet air still has a large temperature rise in the compression process. The maximum temperature rise of liquid water is less than 15 K, which proves that the evaporation of liquid water is caused by the convective mass transfer phenomenon driven by the density difference between liquid water surface and wet air. Moreover, the convective mass transfer phenomenon is that the water vapor in the wet air condensed into liquid water in most of the compression and exhaust process. Therefore, the wet air is far from saturated state in the compression process, and it is closer to the dry air as the compression process goes forward.

Key words: water lubrication, twin-screw air compressor, wet air, heat and mass transfer, convection