Study On Collaborative Optimization Of Flow Field And Temperature Field Of Power-law Fluid In Spiral Tube

Polymer flooding technology,which is widely used in oil production engineering,benefits from the property of high viscosity and low thermal conductivity of power-law non-Newtonian fluid,which is higher than that of ordinary water flooding.At the same time,the shear degradation effect of spiral channel is smaller than that of conventional straight channel,and the polymer solution in the pipe is in high viscosity,which further promotes the oil production.Therefore,it is the foundation of engineering application to deeply explore the flow and heat transfer characteristics of power-law fluid in the spiral tube,which provides theoretical basis for the research of actual heat transfer technology,and has important practical significance to meet the needs of energy conservation in the economic development.In this paper,CMC aqueous solution,a common power-law fluid in engineering,is chosen as the flow medium.Referring to the complex physical properties of non-Newtonian fluid,the viscosity and thermal conductivity of the medium are set as the variable physical parameters with the change of temperature.The model is established and verified by grid independence.CFD software is used to simulate the flow resistance and heat transfer characteristics of non-Newtonian power-law fluid in the spiral tube.The results of numerical simulation in this paper are compared with the results of correlation calculation in the literature to verify the rationality of the mathematical model and simulation calculation method in this paper.Then,according to the influence of three different flow conditions,structural parameters and relative roughness on the resistance coefficient and heat transfer Nusselt number along the spiral pipe,the curve chart of the change rule of the two coefficients is drawn,and the relationship between the cooperation angle,Reynolds number and Nusselt number is further established by using the cooperation of flow and heat transfer field,and the cooperation degree of temperature field and velocity gradient field is comprehensively analyzed.Based on the analysis of the flow and heat transfer law of the typical spiral tube by the field synergy principle,six improved models of the typical spiral tube structure in this paper are proposed.According to the parameters of the improved model,the influence of the size and shape of the groove structure on the performance of the tube is analyzed qualitatively.CFD technology is used to simulate the distribution of velocity field,pressure field and temperature field in the channel with different slot structures.The evaluation standard of pipeline performance is the comprehensive performance evaluation factor of flow and heat transfer.At the same time,in the form of cloud chart,the value of coordination angle can be directly reflected.The results show that under laminar flow conditions,the increase of the curvature of the spiral tube will lead to the increase of the resistance coefficient and the Nusselt number.This is mainly because the curvature value is directly related to the twist degree of the spiral tube.The disturbance caused by the increase of the twist degree of the tube hinders the flow and weakens the thickness of the boundary layer,making the flow resistance increase and the thermal resistance decrease.When the fluid is in the laminar flow state,with the change of Reynolds number,the law of resistance coefficient and Nusselt number is just opposite,the resistance coefficient decreases and Nusselt number increases.The energy loss is affected by the Reynolds number and the relative roughness of the tube wall.The larger the flow velocity is,the rougher the tube wall is,the better the heat transfer effect is.From the perspective of field synergy,the magnitude of synergy angle is inversely proportional to the curvature value and directly proportional to the Reynolds number.In other words,the smaller the synergy angle of temperature field and velocity gradient field is,the better the synergy degree of the two fields is when the slow flowing fluid flows in the pipe with large bending degree.The change of groove structure and size will directly affect the convective heat transfer in the tube,but the change of groove depth has a greater influence on the comprehensive performance evaluation factor of flow and heat transfer than the change of groove width of the same size.In addition,with the increase of flow rate,the comprehensive performance evaluation factors change regularly.In the process of increasing the Reynolds number,the evaluation factor will first slowly decrease to the minimum value with the increase of the Reynolds number,then the Reynolds number will continue to increase,and the evaluation factor will also increase to the maximum value,then decrease and finally tend to be stable.The cloud chart of field synergy angle distribution shows that the overall value of synergy angle at the entrance of the pipeline is the smallest,and the angle gradually increases with the flow.In this paper,based on the field synergy theory and advanced computer technology,the flow and heat transfer process of power-law non-Newtonian fluid in the spiral tube channel are analyzed with the support of numerical simulation technology.The purpose of the study is to discuss the various factors that affect the flow and heat transfer in the spiral tube and to explore the mechanism of resistance loss and heat transfer along the tube.Then,based on the cooperative principle of flow field and temperature field,the degree of convective heat transfer in the tube is evaluated comprehensively,and the influence of structural parameters on the overall enhanced heat transfer performance is explored.The significance is to optimize pipeline design and improve economic benefits.