印度中部某三级眼科护理中心的角膜屈光手术 实践

A time-domain calculation model was developed to study the density wave instability of steam- water two phase flow in parallel multiple channel system. Based on the collocated mesh method, the flow domain along each channel was split into a series of sections, and the discretized mass?momentum, and energy equations were established for each section with consideration of the property variation. According to relevant parameters of boiler water wall under low load conditions during deep peak shaving?the model was used to study the density wave oscillation characteristics among parallel multiple channels under low system pressure (p= 8-10 MPa) and low system mass flow rate (G= 300-500 kg/(m² • s)). The axial heat flux distribution on the pipe wall was simplified, and it followed a linear distribution law that increases first and then decreases along the pipe. Results show that the stability of the system is gradually weakened with the decrease of system pressure and system mass flow rate. With the increase in the non-uniformity of the axial heat flux distribution, the density wave oscillation of the flow rate tends to diverge, and the corresponding threshold heat power gradually decreases, indicating that the system tends to be unstable. The change trend of the threshold heat power with the non-uniformity of the axial heat flux distribution is nonlinear.