Study on Flow Instability inside Multiple Parallel Pipes of Direct Steam Generation

摘要

Flow instability in parallel pipes is closely related with the application of direct steam generation (DSG) for parabolic trough solar power technology. Maldistribution of the flow rate may occur in heated parallel pipes with common inlet and outlet manifolds. The theoretical analysis on four parallel pipes that undergoes a process of heating and evaporation during different heating loads is carried out to indicate all the possible steady-state solutions. Stable solutions and unstable solutions are differentiated through linear stability analysis. It is shown that the more number of heated pipes, the more stable steady state solutions of the splitting ratios, and the greater range of uneven flow rate distribution. Transient analysis is applied to simulate the response of the system to finite disturbances and the performance due to variations in operating conditions by Simulink of Matlab. The results confirm the correctness of the linear stability analysis, and a hysteresis phenomenon is observed when a solution is turning to another solution, even for unstable ones. In addition, A method is proposed to improve flow distribution uniformity in parallel pipes by installing a resistant orifice at the inlet of each pipe where is not heated.