Thermal performance enhancement in a square channel heat exchanger(HX)using a passive technique is presented.Vortex turbulator insertion in a square channel HX as a passive technique is selected for thermal improvemen...Thermal performance enhancement in a square channel heat exchanger(HX)using a passive technique is presented.Vortex turbulator insertion in a square channel HX as a passive technique is selected for thermal improvement.The vortex turbulator of interest is discrete X-V baffles(XVB).The discrete XVBs are inserted in the square channel with the main aim of generating vortex flow.The vortex flow generated can support the enhanced convective heat transfer coefficient and also enhance HX performance.Effects of baffle configuration(type A and B),baffle size(w/H=0.05,0.10,0.15 and 0.20),baffle distance(e/H=1,1.5 and 2)and flow direction(±x air flow paths)on fluid flow and thermal topologies are numerically investigated by using a commercial code.As shown by the numerical results,the predicted flow configuration with the discrete XVB insertions,which include impinging and vortex streams,is found through the HX channel.The perturbing thermal boundary layer and greater air blending are also found through the HX channel inserted with the discrete XVB.These mechanisms promote and augment the convection heat transfer coefficient,heat transfer rate and rise thermal potentiality.The maximum Nusselt number of the channel with the baffles inserted is 11.01 times upper than that of the smooth channel,while the greatest thermal performance factor(TPF)is observed to be around 3.45.展开更多
Trace amounts of Zr and V can increase the recrystallization temperature of Al-Mg-Si wrought aluminum alloys,which is expected to regulate the recrystallization grain.In this paper,trace amounts of V and Zr were added...Trace amounts of Zr and V can increase the recrystallization temperature of Al-Mg-Si wrought aluminum alloys,which is expected to regulate the recrystallization grain.In this paper,trace amounts of V and Zr were added to recycled Al-Mg-Si alloys,and their e ffects on the microstructure and mechanical properties of the cast alloys were studied by scanning electron microscopy(SEM)and synchrotron radiation X-ray tomography(SRXT).The results show that the addition of Zr significantly increases the grain sizes due to the“Zr poisoning”;V addition has no significant effect on the grain size.The morphology of Fe-rich phase gradually changes from the large Chinese-script shape to the fine short rod and curved long strip shape,and the distribution uniformity is improved with the combined addition of V and Zr.The three-dimensional(3 D)morphology of Fe-rich phase includes granular,short rod-like,simple branch and multi-branch structures.The individual addition of V and Zr has no significant effect on the morphology of Fe-rich phase;but the combined addition of V and Zr significantly increases the number and volume fraction of Fe-rich phase with small size(diameter£15μm),the number of branches in the largest Fe-rich phase is significantly reduced,resulting in the improvement of elongation.This work provides a theoretical basis for the development of new recycled Al-Mg-Si alloys in industrial application.展开更多
以 L i2 CO3 和 NH4 VO3 为原料 ,低温合成了 L i1+ x V3 O8.通过对中间产物的热分析 ,选定了低温合成 L i1+ x V3 O8的适宜煅烧温度为 30 0℃ .研究表明 ,L i1+ x V3 O8,原料 L i/ V摩尔比应大于1∶ 3.以 Li1+ x V3 O8作为正极材料 ,...以 L i2 CO3 和 NH4 VO3 为原料 ,低温合成了 L i1+ x V3 O8.通过对中间产物的热分析 ,选定了低温合成 L i1+ x V3 O8的适宜煅烧温度为 30 0℃ .研究表明 ,L i1+ x V3 O8,原料 L i/ V摩尔比应大于1∶ 3.以 Li1+ x V3 O8作为正极材料 ,金属锂为负极组装了模拟电池 ,高、低温合成材料具有较高的放电容量和放电电压 .XRD、SEM分析结果说明低温合成样品的结晶度低、粒径较小 .展开更多
文摘Thermal performance enhancement in a square channel heat exchanger(HX)using a passive technique is presented.Vortex turbulator insertion in a square channel HX as a passive technique is selected for thermal improvement.The vortex turbulator of interest is discrete X-V baffles(XVB).The discrete XVBs are inserted in the square channel with the main aim of generating vortex flow.The vortex flow generated can support the enhanced convective heat transfer coefficient and also enhance HX performance.Effects of baffle configuration(type A and B),baffle size(w/H=0.05,0.10,0.15 and 0.20),baffle distance(e/H=1,1.5 and 2)and flow direction(±x air flow paths)on fluid flow and thermal topologies are numerically investigated by using a commercial code.As shown by the numerical results,the predicted flow configuration with the discrete XVB insertions,which include impinging and vortex streams,is found through the HX channel.The perturbing thermal boundary layer and greater air blending are also found through the HX channel inserted with the discrete XVB.These mechanisms promote and augment the convection heat transfer coefficient,heat transfer rate and rise thermal potentiality.The maximum Nusselt number of the channel with the baffles inserted is 11.01 times upper than that of the smooth channel,while the greatest thermal performance factor(TPF)is observed to be around 3.45.
基金Project(2024YEE0109100) supported by the National Key R&D Program of ChinaProjects(52074131,52104373) supported by the National Natural Science Foundation of ChinaProjects(2022YFJH001,2024YFJH001) supported by the Science and Technology Plan Program of Qingyuan City,China。
文摘Trace amounts of Zr and V can increase the recrystallization temperature of Al-Mg-Si wrought aluminum alloys,which is expected to regulate the recrystallization grain.In this paper,trace amounts of V and Zr were added to recycled Al-Mg-Si alloys,and their e ffects on the microstructure and mechanical properties of the cast alloys were studied by scanning electron microscopy(SEM)and synchrotron radiation X-ray tomography(SRXT).The results show that the addition of Zr significantly increases the grain sizes due to the“Zr poisoning”;V addition has no significant effect on the grain size.The morphology of Fe-rich phase gradually changes from the large Chinese-script shape to the fine short rod and curved long strip shape,and the distribution uniformity is improved with the combined addition of V and Zr.The three-dimensional(3 D)morphology of Fe-rich phase includes granular,short rod-like,simple branch and multi-branch structures.The individual addition of V and Zr has no significant effect on the morphology of Fe-rich phase;but the combined addition of V and Zr significantly increases the number and volume fraction of Fe-rich phase with small size(diameter£15μm),the number of branches in the largest Fe-rich phase is significantly reduced,resulting in the improvement of elongation.This work provides a theoretical basis for the development of new recycled Al-Mg-Si alloys in industrial application.
文摘以 L i2 CO3 和 NH4 VO3 为原料 ,低温合成了 L i1+ x V3 O8.通过对中间产物的热分析 ,选定了低温合成 L i1+ x V3 O8的适宜煅烧温度为 30 0℃ .研究表明 ,L i1+ x V3 O8,原料 L i/ V摩尔比应大于1∶ 3.以 Li1+ x V3 O8作为正极材料 ,金属锂为负极组装了模拟电池 ,高、低温合成材料具有较高的放电容量和放电电压 .XRD、SEM分析结果说明低温合成样品的结晶度低、粒径较小 .
