Study On Thermodynamics Properties Of Humid Air At High Temperature And Pressure

Due to crisis emergences in power engineering and environment pollution all of the world, high efficient gas turbine is urgent needed. The humidity air turbine (HAT) is one of the thermodynamic systems, which have features of high efficiency, low cost and low emissions because of the addition of water into the compressed air. The operating temperature may be up 250℃and the pressure may be higher than 5MPa in key components (the saturator) of HAT. Meanwhile, this technology can be used for compressed air energy storage (CAES) in which the working pressure may be up to 15MPa. For HAT, properties of humid air have been calculated at high pressures and low temperatures as well. The great deviation of thermodynamic parameter will be brought on the calculation of thermodynamics process by using the common idealized assumption for humid air. These deviations are not acceptable for typical calculations in HAT. Similar problems occur for CAES plants. In order to meet the demands of engineering design, the humid air must be regarded as a kind of real gas and more accurate thermodynamic properties of the humid air are acquired at high temperature and high pressure.On the basis of virial state equation and the corresponding-states principle, a state equation of corresponding-states-virial is proposed to calculate thermodynamics properties of humid air, which is used as working substance in humid air turbine and compressed air energy storage (CAES) system at high temperature and high pressure. The activity coefficient method and EOS method are utilized to calculate the vapor-liquid equilibrium state of humid air. Main contents of study listed as following:1. Previous experimental data of humid air have been collected. According to the parameter range of humid air used in humid air turbine and compressed air energy storage(CAES) system, the applied range of thermodynamics properties of humid air is determined .2. Based on virial state equation and the corresponding-state principle, expand-corresponding-state principle is introduced to describe the virial coefficients of state equation. A new model, which is expand-corresponding-states form with 4 characteristic parameters, is built. The second and third virial coefficients of dry air, water vapor and humid air are determined. The results are compared with the data offered by ASHER.3. The factors of compressibility of humid air are calculated by this new state equation.