Experimental And Simulation Study On Heat Transfer And Flow Characteristics Of New Type Heat Storage Elements

In order to alleviate the ash accumulation and low temperature corrosion problems of rotary air preheater caused by SCR technology,enamel heat storage elements are generally used in cold end of rotary air preheater.Compared with the Cowden steel heat storage element,some basic parameters of the enamel heat storage element have changed,the heat transfer effect of the heat storage element has become worse,and the flow resistance will also change accordingly.Therefore,the study of the heat transfer and flow characteristics of enamel heat storage elements is very important for the selection of cold end enamel heat storage elements of rotary air preheater and the design and calculation of rotary air preheater.The main research object of this paper is DN and DU heat storage elements.The heat transfer and flow characteristics of these two types of heat storage elements are studied by experimental and numerical simulation methods.The experimental system of alternating hot and cold air scour was established.By changing the flow rate of hot and cold air to simulate the actual flow rate of flue gas,the heat transfer and resistance characteristics of two kinds of heat storage elements were studied respectively,and the heat transfer and resistance performance of DN and DU were compared.In addition,the change of heat transfer and resistance properties before and after enamel modification of the regenerative element is also discussed.The physical models of DN and DU heat accumulator were established.The turbulence model of Realizable k-ε and the enhanced wall treatment near the wall were used to simulate the heat transfer and flow characteristics of DN and DU heat accumulator.The results show that the surface of DN regenerative element becomes smooth and its equivalent diameter increases after enamel treatment.Compared with before enamel treatment,the convection heat transfer coefficient of DN regenerative element decreases by 9%,and the Darcy resistance coefficient F decreases by 36%.As the Reynolds number increases,the Nussel number of the two plates increases,on the contrary,the drag coefficient decreases gradually.Compared with DU type heat accumulator,the Darcy resistance coefficient F of DN type heat accumulator is reduced by 17% and the heat release coefficient is increased by 32%.The internal flow field and temperature field of DN and DU are studied by numerical simulation.Compared with DU plate,DN plate increases oblique ripple,which enhances the fluid disturbance and has better convective heat transfer effect.As the number of oblique ripples increases,the size also decreases,which reduces the resistance of the flow.As the Reynolds number increases,the Nussel number of the two plates increases,on the contrary,the drag coefficient decreases gradually.Compared with the experiment,the Darcy resistance coefficient F of DU type heat accumulator decreases by 14.9%,and the heat release coefficient increases by 12.3%.The Darcy resistance coefficient F of DN type heat accumulator decreases by 12.7%,and the heat release coefficient increases by 13.9%.