Investigation On The Characteristics Of The Heat Transfer And Flow Resistance Inside An Innovative Vortex Tube

At present,the problems on the environmental pollution and energy depletion are becoming much more severer.The enhanced heat transfer tubes are widely utilized in various industries and daily-life,because they can remarkably increase the thermal efficiency of the heat-exchange equipments and reduce energy consumption.In this thesis,an innovative enhanced heat transfer tube-vortex tube is proposed with the aid of the characteristics of the dimpled tubes,and then the thermal-hydraulic performance of the vortex-shaped tube is further explored by using the numerical simulation method.At first,based on the theory of the structural mechanics,the finite element method is used to establish the geometric model of the vortex tube.The established geometrical model is more consistent with the actual physical model,and can reflect well the plastic deformation of the real tube wall.Additionally,the geometrical model is also constructed by using the computer aided design(CAD)method,which is ofen adopted in the existed literature.The 3D numerical simulations are carried out to study the behaviors of the heat transfer and flow processes of the fluid inside the tube by the realizable k-? turbulence model,and compared with the thermo-hydraulic performance of the two models.The results show that the protrusion structure induced by the vortex structure can significantly enhance the heat transfer performance and homogenize the flow field,accomparised by increasing the flow resistance.The model obtained by the structural mechanics can reflect more reliably the flow and heat transfer characteristics,which are characterized by the more effective heat transfer enhancement,much smaller flow resistance and larger thermal performance factor.In the range of 5000<Re<30000,compared to the smooth tube,the heat transfer performance of the vortex tube is increased by 22~53%.The field synergy principle is utilized to elucidate the heat transfer enhancement mechanism of the vortex tube.Furthermore,the vortex tubes with the different geometrical parameters are established by the structural mechanics simulation,and then the effects of the geometrical parameters on the heat transfer and flow characteristics are analyzed in detailed.Meanwhile,the effect behaviors of the different geometrical parameters are identified and the corresponding geometrical parameter set of the optimal thermal-hydraulic performance is found(?=60°?s=25 mm?h=8 mm and R=30 mm).With the optimal geometric parameters,the comprehensive performance factor of the vortex tube can reach to 1.19~1.27.Then,the multiple regression analysis of the numerical results is carried out,and the fitted formulas of Nu and f are attained.Finally,the effects of the structural parameters and inserting spoilers inside the tube on the heat transfer and flow resistance are studied.The results show that the global Nu of the vortex tube increases further by 8.4~20.8%,after adding a cavity in the circumferential direction.For inserting the smooth twisted belt in the mainstream regime,the heat transfer enhancement is limited and lower than the pressure loss.