Experimental And Numerical Study Of Mixed Convective Heat Transfer In A Large Vertical Rectangular Channel

The passive containment cooling system is an important part of the advanced pressurized water reactor passive safety system.The basic principle is that under the accident condition,the water storage tank at the top of the containment will automatically release water under the action of gravity to cool the outer wall of the containment.However,if the accident lasts for too long,the cooling water in the storage tank will be exhausted,and the system can only generate heat from the convective heat transfer through the natural circulation of air in the rectangular-like passage and the outer wall of the containment.Under normal circumstances,the convective heat transfer capacity of the air and the wall is poor,so it is the key to the safety of the system.In this paper,two double-shell slabs were constructed to simulate the double-shell structure of the containment,and experiments were conducted to study their heat transfer.Through the obtained experimental data,it is analyzed in principle that the share of natural convection in mixed convection can not be neglected within a certain range of Reynolds number,and an empirical relationship is fitted,from which a certain Reynolds number can be predicted.The quantitative relationship between mixed convective heat transfer and forced convection and natural convective heat transfer.Based on the experiment,the heat transfer in the rectangular channel was simulated based on the applicable numerical model,and the effect of the orifice plate was verified.It was found that the orifice plate can enhance the convective heat transfer to a certain extent.In small Reynolds number ranges,natural convection has a great influence on mixed convection,eddy current will be generated at the flow channel section,which greatly reduces the convective heat transfer capacity.