Investigations On Drag Reduction With Polyacrylamide In Microtubes

Microsystems have been widely used in industry and biomedical medicine,such as micro-heat exchangers,micro-mixing and separation processers,fuel cells and so on.However,compared with the liquid flow resistance in conventional scale tubes,it is necessary to concern that resistance in microtubes increases significantly and thus requires a higher pumping power.Since lower energy consumption is one of the aims of the microsystem,the reduction of the required pumping power is highly desirable.In this work,the performance of polyacrylamide(PAM)as drag reduction agent in stainless steel microtubes was investigated and pure deionized water was also used as a reference,then the Fluent software was used to simulate the flow characteristics of PAM aqueous solution and pure deionized water,respectively.The main contents are as follows:1.The density ?(285.15-306.15 K)and viscosity ?(285.15-313.15 K)of PAM aqueous solutions were measured,and also was the rheological property(288.15K)of PAM aqueous solutions.Using the similar-Arrhenius equation,the viscosity data of PAM aqueous solutions are associated,and the power law model is used to associate the rheological properties of PAM aqueous solutions,both of which showing satisfied correlation effect.2.In this work,the performance of PAM(M_w=3 million and 10 million)as drag reduction agent in stainless steel microtubes with diameters in the range 116-1016?m were investigated.Experimental results indicated that drag reduction characteristic with PAM aqueous solution in microtube was different from that in conventional scale tubes.The friction factor of PAM aqueous solutions in the laminar flow region is larger than that of deionized water;drag reduction was observed in the transitional flow region,and the range of transitional flow region is wider than that of deionized water;the difference of friction factor between PAM aqueous solution and deionized water becomes smaller in the turbulent flow region.3.The maximum DR(%) is found to be 59.30%for 30 ppm PAM(M_w=10 million)aqueous solutions when Reynolds number equals to 5016 and the diameter of stainless steel microtube is 523?m.A parameter ? was used to describe the deviation of friction factor between PAM aqueous solution and deionized water,as well the Moody equation is modified with the characteristic parameter ? to better predict the friction factor of PAM aqueous solution flow in the turbulent flow region(AAD%is 2.04%).4.The Fluent software was used to simulate the flow characteristics of PAM aqueous solution and pure deionized water,respectively.It was found that AAD% between simulation results and experimental results of different flow regions:the laminar flow region,the transitional flow region and the turbulent flow region is 5.21% for deionized water.Besides,the flow resistance of PAM aqueous solution increased in the laminar flow region,which is in agreement with the experimental results;and the drag reduction didn't occur in the transitional flow region and as well as the turbulent flow region,which is yet not in consistent with the experimental results and the related reasons are discussed and analyzed in this work.