Two-phase Flow Instability Of Parallel Pipes In Solar Thermal Power Plant

The problems of uneven flow distribution of vapor-liquid in the parallel pipes widely exist in power boilers, steam generators, heat exchangers and boiling water reactors. The root cause of instability is that the pressure drop versus mass flow rate curve of the system shows an "N-shape" behavior. To solve this two-phase instability, the simplest and the most effective method is to install the throttle valve at the entrance of pipeline, so that the pressure drop characteristics of flow shows monotonic,however,at the same time the installation of the throttle valve consumes more pump power.The calculation of required pressure drop between exports and imports of heating pipe and the Relationship between The pressure drop and flow rate are of great importance for the practical engineering. The pressure drop characteristic curve is not only the basis of analysis,but also the root cause of pressure drop oscillations and density wave oscillation.This paper mainly deals the calculation of inlet pressure for heating pipe if knowing the conditions of outlet pressure, inlet temperature, etc. We select the appropriate model taking into account the different pressure range:phase model of low pressure and homogeneous model under high pressure; the most appropriate empirical formula of void fraction for different conditions. The pressure drop is calculated using MATLAB in horizontal pipe and vertical pipe through writing programs. Meanwhile, in order to avoid the occurrence of drift phenomenon in the parallel pipeline, minimum pipe inlet orifice coefficients are calculated, the most appropriate diameter of throttle is in turn calculated by throttle coefficient.Based on the calculation procedure, the two-phase flow in parallel pipe which occurs in direct steam generation of solar trough system was verified. In order to optimize the operation, we analysis the different parameters having an impact on characteristics of flow rate drift. At the same time, the required minimum mass Flow rate which can avoid stratified flow in parallel pipe is also obtained and the pros and cons of different methods is Compared.