Abstract: Due to the issues of large-scale central-air-conditioning water humidification systems, such as operational difficulty under high loads, uneven humidification, and easy fogging, numerical simulations were performed using the FLUENT software. Models were established for vertical and horizontal supply pipes connected to the multioutlet pipes for studying flow discharge along the route (five-hole configuration vs. symmetrically distributed six-hole configuration) in large central-air-conditioning water humidification systems. Based on the volume of fluid model, the transport characteristics of wet steam in these configurations were investigated. The pressure, flow velocity, and density distributions of the steam along the pipe at different volume fractions were analyzed, and the uniformity of steam outflow under different operating conditions was studied. The results showed that in the vertical supply pipe, pressure gradually increased from the inlet to the end, whereas in the horizontal supply pipe, pressure was high at the inlet and low on both sides of pipe; moreover, as the volumetric fraction of the steam decreased, the pressure became more uniform on both sides. The six-hole horizontal supply configuration achieved the most uniform flow distribution under the current model settings. Density analysis revealed that decreasing the steam volumetric fraction significantly increased the outlet moisture content in the horizontal supply system. This study provides a reference for the design of water humidification equipment and research on along-the-route steam outflow in a multioutlet pipe, offering a theoretical basis for related multiphase outflow scenarios paths.

Key words: Central air conditioning, water humidification system, two-phase flow, multioutlet pipe, numerical simulation