Calculation of spray-type steam evaporator

For the understanding of the different thermodynamic and gasdynamic processes in a spray-type evaporator, a theory is developed to calculate the two phase flow with change of phase with any change of evaporator cross section. Firstly the calculation model for the problem is given. The control volume is divided into three control volumes: For water droplets in preheating phase, for water droplets in saturation state, and for the steam phase. The fundamental equations were formulated under different assumptions for the steam- and water control volumes. After the transformation of the fundamental equations, they are solved numerically. The number of drop groups and the number of drops in every group are determined. The distribution of the drop spectrum, the end steam wettness, and the steam temperature along the evaporator are calculated. The numerical results have shown, that the steam temperature, and the steam wettness decrease very strongly at the beginning of the evaporator. This is a result of the high degree of steam superheat, and due to the high steam wettness. After the initial strong decrease of steam temperature and steam wettness, it is varied by a smaller rate along the evaporator, so that it lead to a strong increase of the evaporator length, especially when small values for end steam wettness and end steam superheat are prescribed at the evaporator outlet.