Heat exchangers are integral parts of important industrial units such as petrochemicals,medicine and power plants.Due to the importance of systems energy consumption,different modifications have been applied on heat e...Heat exchangers are integral parts of important industrial units such as petrochemicals,medicine and power plants.Due to the importance of systems energy consumption,different modifications have been applied on heat exchangers in terms of size and structure.In this study,a novel heat exchanger with helically grooved annulus shell and helically coiled tube was investigated by numerical simulation.Helically grooves with the same pitch of the helical coil tube and different depth are created on the inner and outer wall of annulus shell to improve the thermal performance of heat exchanger.In the first section,thermal performance of the shell and coil heat exchanger with the helical grooves on its outer shell wall was compared with same but without helical grooves.At the second section,helically grooves created on both outer and inner wall of the annulus shell with different groove depths.The results showed that the heat exchanger with grooves on both inner and outer shell wall has better thermal performance up to 20%compared to the heat exchanger with grooves on only outer shell wall.The highest thermal performance achieves at lower flow rates and higher groove depths whereas the pressure drop did not increase significantly.展开更多
In this study,mixed convection heat transfer and fluid flow is numerically investigated in an open system enclosure containing a heated obstacle.Effects of the positions of both obstacles and fluid flow outlet on the ...In this study,mixed convection heat transfer and fluid flow is numerically investigated in an open system enclosure containing a heated obstacle.Effects of the positions of both obstacles and fluid flow outlet on the flow field and heat transfer within the enclosure were studied.Richardson number ranging from 0.1 to 10 was examined for a constant Grashof number at different Reynolds numbers in both base fluid and fluid mixed with Cu nanoparticles(0 to 4%of volume fractions).It is found that the obstacle and outlet position as well as the Richardson number greatly affect the flow field and heat transfer rate.The maximum heat transfer rate occurs for Richardson number 0.1,when the outlet and obstacle position are located at the bottom of the right side of the enclosure(P3)and near right side of the enclosure(8 H),respectively.Also,the heat transfer rate is higher when the obstacle is placed close to the inlet(2 H)and outlet(8 H)compared to the center of the enclosure(5 H).It is shown that although the change of volume fraction of nanofluid does not have significant effect on the flow pattern,however,it enhances the heat transfer rate through improving the effective thermo-physical properties of the base fluid.展开更多
文摘Heat exchangers are integral parts of important industrial units such as petrochemicals,medicine and power plants.Due to the importance of systems energy consumption,different modifications have been applied on heat exchangers in terms of size and structure.In this study,a novel heat exchanger with helically grooved annulus shell and helically coiled tube was investigated by numerical simulation.Helically grooves with the same pitch of the helical coil tube and different depth are created on the inner and outer wall of annulus shell to improve the thermal performance of heat exchanger.In the first section,thermal performance of the shell and coil heat exchanger with the helical grooves on its outer shell wall was compared with same but without helical grooves.At the second section,helically grooves created on both outer and inner wall of the annulus shell with different groove depths.The results showed that the heat exchanger with grooves on both inner and outer shell wall has better thermal performance up to 20%compared to the heat exchanger with grooves on only outer shell wall.The highest thermal performance achieves at lower flow rates and higher groove depths whereas the pressure drop did not increase significantly.
文摘In this study,mixed convection heat transfer and fluid flow is numerically investigated in an open system enclosure containing a heated obstacle.Effects of the positions of both obstacles and fluid flow outlet on the flow field and heat transfer within the enclosure were studied.Richardson number ranging from 0.1 to 10 was examined for a constant Grashof number at different Reynolds numbers in both base fluid and fluid mixed with Cu nanoparticles(0 to 4%of volume fractions).It is found that the obstacle and outlet position as well as the Richardson number greatly affect the flow field and heat transfer rate.The maximum heat transfer rate occurs for Richardson number 0.1,when the outlet and obstacle position are located at the bottom of the right side of the enclosure(P3)and near right side of the enclosure(8 H),respectively.Also,the heat transfer rate is higher when the obstacle is placed close to the inlet(2 H)and outlet(8 H)compared to the center of the enclosure(5 H).It is shown that although the change of volume fraction of nanofluid does not have significant effect on the flow pattern,however,it enhances the heat transfer rate through improving the effective thermo-physical properties of the base fluid.
