Studies on Water Flow Boiling Heat Transfer Characteristics in Vertical Narrow Rectangular Channel

A single-side heating apparatus is set up to study the flow boiling and heat transfer in vertical narrow rectangular channel,experiment research on flow boiling and heat transfer characteristics in a vertical narrow rectangular channel with the section of 250mm × 5 mm is carried out. According to the experimental analysis:( 1) With the increase of dryness,the local heat transfer coefficient firstly increases then decreases,there is a maximum,which is saturated nucleate boiling region,the steam quality is close to zero,also it is close to the onset of boiling. Accordingly flow mode of fluid is from single phase,bubble,slug, churn to annular flow.( 2) For flow boiling heat transfer,nuclear boiling heat transfer is significantly affected by heat flux,but liquid film evaporation is nearly not. So it is assumed that heat transfer is caused by the change of heat flux.( 3) The change of inlet temperature has influence on single-phase flow heat transfer coefficient,but flow boiling heat transfer coefficient has great relationship with flow pattern and generated bubbles,and not inlet temperature.