Study On Turbulent Heat Transfer Characteristics And Correlation Of Internal Threaded Tube

In the actual operation process of the internal threaded pipe,the pipe components and materials have a certain role in the fluid medium,as well as the physical and chemical characteristics of the fluid medium itself,the uncertain environmental parameters around the tube and inside the tube occupy a large proportion in the assessment of the overall heat transfer performance.Fluid medium and environmental factors combined with the formation of turbulence,the turbulent flow medium formed in the tube is the actual production application of fluid water.In this paper,221 sets of data of heat transfer mechanism of internal threaded tubes with ten fin numbers,seven spiral angles and nine fin heights were numerically calculated and analyzed.When Re is 20000,30000,40000,50000,60000,internal thread Angleαis 15°,20°,25°,30°,35°,40°,45°,thread fin number Ns is 10,16,20,24,30,36,40.In the range of wing height E of 0.20 mm,0.25 mm,0.30 mm,0.35 mm,0.40mm,0.45 mm,0.50 mm,0.55 mm and 0.60 mm,the effects of flow velocity,internal helix Angleα,threaded fin number Ns and wing height E on Nu were analyzed.By analyzing fin parameters and velocity and other factors,the heat transfer characteristics of internal threaded pipe are discussed in depth,and the heat transfer performance of internal threaded pipe is studied,and the heat transfer correlation formula is developed.In this paper,the thermal characteristics of internal threaded pipe are analyzed by heat transfer theory and fluid mechanics theory.The basic physical and mathematical model of internal threaded pipe is established by energy equation and turbulence model,and the heat transfer process of fluid water from inlet to outlet is calculated by using the established model.Self-programmed calculation,and the data results are processed in a graphical manner.The enhanced heat transfer law of water under different Reynolds numbers is obtained while calculating the model structure,which determines the theoretical basis for the operation of internal threaded pipe in heat exchanger equipment,and lays the foundation for the heat transfer performance of new air conditioning,refrigeration system and other heat exchange equipment technology.The following conclusions are drawn:（1）Under the same parameter conditions,Re has a good effect on the convective heat transfer.With the increase of Reynolds number Re,the heat transfer effect is better,and Nu number changes by 0.41～1.70 times.The influence of fin number Ns on heat transfer flow was basically unchanged or little changed,and Nu number varied from 6.9 to 24.4%.With the increase of wing height E,the flow heat transfer effect also increased,and Nu number changed by 7.1～19.4%.Helix Angleαand Nu number varied 12.4～20.9%.Re has the most significant effect on heat transfer.（2）When analyzing the influence of flow heat transfer,the f Re^0.25 number increases by12.1%with the increase of Reynolds number.With the increase of wing number Ns,f Re^0.25increased by 15.0%.With the increase of wing height E,f Re^0.25 increased by 44.5%.With the increase of helix Angleα,f Re^0.25 increases by 84.7%.It can be seen from the analysis of simulated tube data that the influence of helix Angleαchanges most obviously.（3）The calculation result associated Ravigurajain is closer to the data value than associated Gnielinski.However,there is some deviation with the experimental data,when the wing height is 0.20～0.60 mm,the maximum error of Gnielinski is between 17.0～24.0%,the maximum error of Ravigurajain is between 21.0～27.0%.When the number of wings is44,48 and 52,the error range of association Gnielinski is 35.9～40.3%,and the error range of Ravigurajain is 34.9～39.4%.When the Reynolds number is 20000～60000,the error range of association Gnielinski is 31.6～35.3%,and that of Ravigurajain is 28.8～34.4%.The numerical results are consistent with the correlation results,and the calculation method and results are reliable.（4）Under the fluid heat transfer conditions in these types of tubes,the increase of heat transfer coefficient of internal threaded tubes is different from the increase of resistance ratio.Based on the evaluation index of the same mass flow rate（Nu_a/Nu_s）/（f_a/f_s）,the overall heating condition of the fluid ranges from 0.934 to 1.123.With the increase of wing height E,the variation range of evaluation index（Nu_a/Nu_s）/（f_a/f_s）was 1.020～1.123.With the increase of Reynolds number Re,the variation range of evaluation index（Nu_a/Nu_s）/（f_a/f_s）was 0.934～0.988.（5）Based on the three calculated correlations,Nusselt predicted the correlations through simulated data fitting,and the average error of the calculated results of the correlation fitting was 0.2987.