Research On Prediction Model Of Particle Fouling On The Surface Of Riflrd Tube

In industrial production,scaling on heat exchange surfaces is widespread,which has a serious impact on the normal operation of heat exchange equipment,resulting in a large amount of energy waste and economic losses.The problem of fouling is one of the most concerned problems in the field of heat transfer,but it has not been completely solved.Researches on fouling mechanism,fouling prediction model and fouling inhibition have attracted widespread attention.Heat transfer tube elements are often used in heat exchange equipment as a means of enhancing heat transfer.Due to the long fouling cycle,the styles of the enhanced heat transfer tube components are complex and diverse,and the relevant fouling prediction models are still relatively lacking.First of all,this paper takes the rifled tube as the research object,conducts a numerical simulation study on the deposition process of the particulate dirt in the tube,and analyzes the growth characteristics of the particulate fouling with time.According to the actual structural parameters(pipe length,inner diameter,outer diameter,pitch p,rib height e and number of thread heads Ns)of the rifled tube and smooth pipe selected for the particle fouling experiment,the corresponding physical model was established using the SOLIDWORKS software and grid file was generated by ICEM software.In the process of meshing,the quality of the mesh should be improved as much as possible to avoid the negative impact of the low-quality mesh on subsequent simulation calculations.Secondly,the particle fouling deposition process in the rifled tube was studied.After a comprehensive stress analysis of the fouling particles,an improved deposition model was proposed.Compared with the conventional deposition model,this model has more pressure gradient force,virtual mass force,and thermophoretic force,which is convenient for the subsequent field analysis of particulate fouling deposition.Then,an ablation model is established in combination with an empirical formula,and the calculation method of the thermal resistance value of the fouling is given.Analysis of numerical simulation results shows that the RSM model has higher calculation accuracy than the standard k-? model and RNGk-? model,so it is used as the model for fouling simulation in this paper.According to the verification results,the appropriate number of grids for different heat exchange tubes are selected for subsequent simulation calculations.Thirdly,the FLUENT software was used to simulate the deposition process of particulate fouling under the conditions of different flow rates,different concentrations,different particle sizes,different types of dirt,etc.,and the characteristics of the increase of the thermal resistance value of the fouling with time were analyzed and summarized.The prediction model of the thermal resistance of the particulate fouling on the rough heat transfer surface of the rifled tube is established.The establishment of this model is not only conducive to the analysis of the subsequent physical field,but also provides a reference for the subsequent research of the particulate fouling in the rifled tube.Finally,the calculation results are processed using Tecplot and CFD-POST software to study the distribution characteristics of the velocity field and temperature field in the rifled tube on different cross sections.Program in Tecplot to calculate the angle between the two vectors of velocity and temperature gradient in the entire fluid domain.A qualitative analysis was made from the perspective of deposition and erosion on the summary of the growth characteristics of the thermal resistance value of the fouling with time,and the distribution law of the particulate fouling in the microscopic scan of the fouling,combined with the distribution characteristics of the velocity field,temperature field,and synergy angle.