Study On Comprehensive Heat Transfer Performance Of Horizontal Liquid-solid Two-phase Flow With Tube Inserts

The heat exchanger will produce fouling in the working process.The serious fouling situation have negative influence on the regular production.The study of new type heat exchanger has great engineering significance.The particles distribution are not uniform in the horizontal liquid-solid circulating fluidized bed heat exchanger,which affect the heat transfer effect of the heat exchanger,due to the existence of particles gravity.Installing Kenics static mixer in pipe can not only improve the distribution of particles and liquid through the Kenics static mixer produces spiral motion.Because of the augment of turbulence,the heat transfer coefficient is also improved.This paper based on CFD software star-ccm+,analyzing of the temperature filed and velocity field,The tube inserted different Kenics static mixer with twist rate were investigated by analyzing the synergy angle.The results show that the synergy angle decreases with the twist rate decreasing.According to the field-synergy theory,the smaller Kenics static mixer with twist rate can improve the heat transfer more obviously.The horizontal liquid-solid circulating fluidized bed heat exchanger with Kenics static mixer was studied by this experiment.The effects of Kenics static mixer with twist rate,the installation method of Kenics static mixer,flow rate and particle volume fraction on heat transfer performance and flow resistance performance were investigated.Results show that the performance evaluation criteria of Kenics static mixer with twist rate Y=1.5,2.5,4,6 are over 1 in the range of Reynolds number 10000-45000,which indicates that the horizontal fluidized bed heat exchanger with Kenics static mixer can enhance heat transfer.The performance evaluation criteria of horizontal fluidized bed heat exchanger reaches 1.09 at most,when the Reynolds number reaches about 42000,the twist rate of Kenics static mixer is Y=4 and the particle volume fraction is 4%.The effects of Kenics static mixer with twist rate and flow rate on heat transfer performance and flow resistance performance were investigated by CFD software.The Results show that the horizontal tube of uniform particle distribution length increases with the flow rate increasing under the condition of the same twist rate.The horizontal tube of uniform particle distribution length increases with the twist rate decreasing at the same flow rate.Under the condition of the flow velocity is 1.5m/s,The uniform particle distribution length of the Kenics static mixer with twist rate Y=1.5 is 1640 mm.The uniform particle distribution length of the Kenics static mixer with twist rate Y=6 is 760 mm.The numerical simulations also research that the effect of Kenics static mixer with twist rate on heat transfer performance and flow resistance performance.The performance evaluation criteria of Kenics static mixer with twist rate Y=4 reaches 1.1 at most,according to the comprehensive enhanced heat transfer performance.Installing a Kenics static mixer with twist rate Y=1.5 in a 2m-long horizontal fluidized bed heat exchanger can achieve the effects of improving particle distribution and heat transfer performance,when the velocity is more than 1.5m/s.