Analysis Of Heat And Mass Transfer In Polymer Processing

In order to improve the properties of polymer materials,it is significance to study the rheological properties,heat and mass transfer during processing.In this paper,the flow and heat transfer in the processing of polymer films,as well as the heat and mass transfer of polymer fluids in porous medium are discussed.The contents of the study are as follows:1)According to the rheological experiment data of welan gum solution,the Maxwell-power-law constitutive relation with shear thinning and viscoelastic characteristics has been proposed.Combining with Cattaneo-Christov theory,the flow and heat transfer of Maxwell-power-law fluid film are investigated.Furthermore,a corresponding thermal Marangoni convection expression is presented.The coupled similar ordinary differential equations are obtained by similarity transformation,and obtained by double-parameter transformation expansion method(DPTEM).The effects of physical parameters on the flow and heat transfer of Maxwell-power-law fluid film are analysed.2)In order to explore the mechanism of extrusion speed and temperature affecting the quality of polymer film during tape casting,the flow and heat transfer characteristics of ethylene vinyl acetate(EVA)nanofluid film prepared by tape casting are studied.Rheological experiment shows that the melted EVA(28% VA)is a power-law fluid.According to the similar principle of momentum transfer and energy transfer,the modified Fourier's law is presented.And then,the corresponding new convective heat transfer equation has been proposed.The flow and heat transfer governing equations of EVA nanofluid are established.Moreover,a power-law velocity slip model,which is well suited for describing the slip characteristics of polymer films,has been newly developed.With the skillful inverse variable transformation,the velocity and temperature fields at any time and space are first obtained.The effects of relevant parameters on the flow and heat transfer of EVA nanofluid film were explored.3)Polyacrylamide aqueous solution as a significant oil displacement agent,adding nanoparticle can greatly improve its oil recovery.Based on the influences of specific enthalpy on the heat transfer of nanofluids,a developed Cattaneo-Christov heat flux theory is proposed to describe the thermal conductivity of polyacrylamide nanofluids.Maxwell constitutive relation is introduced to describe the viscosity and elasticity of polyacrylamide aqueous solution.The relation between temperature and dynamic viscosity is verified by rheological experiment.Meanwhile,the relation between temperature and thermal conductivity is confirmed by thermal conductivity experiment.Flow,heat and mass transfer of polyacrylamide nanofluid in porous underground strata are established.Moreover,a convective heat transfer coefficient associated with the spatial position is introduced.Using inverse similarity framework along with the analytical method,the distributions of velocity,temperature and concentration at any space are obtained.The effects of relevant parameters of nanofluid on velocity,heat transfer efficiency and concentration diffusion rate are discussed.The theoretical model in this study plays a decisive factor in the flow,heat and mass transfer of polymer fluid in the processing process.The calculating results are consistent with the previous works,which verified the analytical methods.This can supply the relevant academic foundation for the processing of polymer materials,and also provides a new way to solve the similarity solutions.