The Design And Research Of The Superheated Steam Saturator

This paper is analyzed and studied the principle of flow and heat transfer in superheated steam saturator, trying to combine the microcosmic evaporation process of single water droplet and macroscopic character of flow and heat transfer, and better to understand the change regularity of superheated degrees and main influencing factors in superheated steam saturator which means in the mixing duct.First, the evaporation process of a single droplet is explored and analyzed. Based on the principle of heat and mass transfer, the evaporation rate of a single saturated water droplet is derived according to different heat transfer mode between phases. Compared with the thermal convection, the evaporation rate is 13 times higher than one by thermal conduction. Then, the evaporation process of water droplets with no relative speed is simulated by use of the FLUENT software. The droplet diameter changing with the degree of superheat is obtained due to the evaporation process.Secondly, the simplified two-phase model in the mixing duct is constructed between the superheated vapor and saturated liquid. On the basis of a single droplet evaporation model, the volume evaporation rate is successfully derived which established a bridge between the single droplet and macroscopic properties. Through solving continuity equation and energy equations, the mass flow and the degree of superheat changing map in the mixing duct are obtained. The influence of the inter-phase heat transfer about the mixing tube length is explored. It is found that the volume evaporation rate in the mixing tube mostly depends on three factors: the initial diameter of the droplet, the degree of superheat,the mass flow of saturated water and relative velocity between superheat vapor and saturated water. The heat and mass transfer process between two phases is also simulated by use of COMSOL software in the mixing duct. The result is consistent with the result of the aforesaid solution.At last, the structure of superheated steam saturator is designed. The shape size of saturator and the length of internal packing box are determined according to the specific working condition. Two fluid supply devices, the gravity tank type or fluid mechanical pump type, are put forward, which depends on the field installation conditions and user needs. The new type of superheated steam saturator is to ameliorate the shortcomings of existing saturation device and to expand the application field, which improves the practical work performance.