Analysis of Density Wave Oscillations in a Boiling Channel By A New analytical model

Two-phase flow instabilities are observed in many areas of industrial applications such as turbomachinery, refrigeration systems, water boiling reactors and similar systems. Predicting fluid flow parameters such as pressure drop, stability region during boiling and oscillation characteristics are the determining factors in the design and operating conditions of two-phase flow equipment. In this paper, density wave oscillations type instability in boiling process is analyzed.By introducing appropriate dimensionless variables, an integrated model for the process is presented. The model is solved for steady state response of the system by using numerical analysis of a developed numerical method based on weighted residual method (WRM). Stability region is determined in reaction frequency versus ratio of reaction frequency to inlet mass flow plane. In addition, friction number effect on stability threshold is assessed. The effect of mass flow rate, inlet subcooling, system pressure and other important process parameters on the oscillation characteristics as well as the instability boundary are investigated.The results show that with increasing mass flow, the system becomes more stable for DWO occurrence. The critical quality of the exhaust vapor also decreases with increasing mass flow. On the other hand, the period of DWO oscillation and its amplitude increases with increasing mass flow.