The Experts below are selected from a list of 3621 Experts worldwide ranked by ideXlab platform
Yongping Yang - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation on flow and heat transfer of Fin and tube heat exchanger with longitudinal vortex generators
International Journal of Thermal Sciences, 2015Co-Authors: Li Li, Xiaoze Du, Lijun Yang, Yuwen Zhang, Yongping YangAbstract:Abstract Fin-and-tube heat exchangers with plain Fins are widely used in direct air-cooled condenser system in the power plant, because of its relatively simple property compared to some other Fins with variable cross-sectional area channel. In the present study, heat transfer performance and pressure drop for Fin-and-tube heat exchanger with longitudinal vortex generators (LVGs) on the Fin Surface were numerically investigated. Rectangular and delta winglet pairs were punched/mounted on the Fin Surfaces to enhance the heat transfer of the air-side of the Fin-and-tube heat exchangers. The results showed that the Nusselt numbers increased up to 20% for LVGs on plain Fins comparing with plain Fins channel without LVGs. The heat transfer enhancement by rectangular winglets was more significant than that of the delta winglets. The rectangular winglet with angle of attack of 25°showed the best overall performance than any other angles of attack in rectangular winglets configurations. Additionally, the delta winglet with angle of attack of 45° showed the best overall performance than the other angles of attack in delta winglets configurations.
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heat transfer enhancement of wavy Finned flat tube by punched longitudinal vortex generators
International Journal of Heat and Mass Transfer, 2014Co-Authors: Xiaoze Du, Lili Feng, Li Li, Lijun Yang, Yongping YangAbstract:Abstract Punched longitudinal vortex generators (LVGs) were employed to enhance air-side heat transfer on the wavy Fin Surface of flat tube used in direct air-cooled condenser. The heat transfer enhancement of four types of the longitudinal vortex generators with different attack angles were compared by numerical simulations. It was found that the delta winglet pair with attack angle 25° could reach the greatest performance evaluation criteria (PEC) under the conditions of the inlet air flow velocity varied from 1 m/s to 5 m/s. The influences of locations on the wavy Fin Surface and the row number of the longitudinal vortex generators were also discussed. One delta winglet pairs at the middle of the wavy Fin Surface and the minimum row number, n = 1, with the average PEC is 1.23, has the best heat transfer performance of all conditions, which can be recommended for practical applications. Experimental study in wind tunnel with flow field visualization by Particle Image Velocimetry (PIV), as well as the numerical simulations verified that the delta winglet pairs can generate obvious longitudinal vortex pairs at the down-sweep zone, which can enhance the heat transfer between the cooling air flow and heated wall Surface with acceptable pressure loss.
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experimental study on heat transfer enhancement of wavy Finned flat tube with longitudinal vortex generators
Applied Thermal Engineering, 2013Co-Authors: Xiaoze Du, Lili Feng, Yongping Yang, Lijun YangAbstract:Abstract The performance of direct air-cooled condensers in power plant is affected significantly by air-side flow and heat transfer characteristics of the wavy Finned flat tube. Experimental investigations were conducted for air-side flow and heat transfer with and without delta winglet pairs punched on the Surface of the wavy Fin. The different temperature fields of the heated wavy Fin Surface with and without delta winglet pairs were obtained by the infrared thermography technology. Both experiments and numerical simulations showed that a substantial increase in the heat transfer with six delta winglet pair generators on the wavy Fin was obtained with the Reynolds number varying from 1500 to 4500, which was the range of the air flow in practical direct air-cooled condensers. The average Nusselt number increased by 21–60% with the Reynolds number varying from 1500 to 4500 and the average friction factor increased by 13–83% with the Reynolds number varying from 500 to 4500 in experiments. The average performance evaluation criteria, PEC, can be up to 1.31 with six delta winglet pairs punched on the wavy Fin Surface, indicating the high potential of heat transfer enhancement to direct air-cooled condensers by longitudinal vortex generators.
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experimental and numerical study of heat transfer over a Finned elliptical flat tube fitted with longitudinal vortex generators on the rectangular Fin Surface
Journal of Enhanced Heat Transfer, 2013Co-Authors: Li Li, Xiaoze Du, Lijun Yang, Yuwen Zhang, Chao Xu, Yongping YangAbstract:An experimental study of heat transfer over a Finned elliptical flat tube fitted with and without longitudinal vortex generators (LVGs) mounted on the rectangular Fins was carried out in a wind channel. Numerical simulation was performed to compare the experimental results and to verify the turbulence model. The test models were magnified four times greater than the original react model and correspondingly simplified according to the principle of similitude. Several Fins were designed to construct the periodic boundary condition. Thermo couples were used to measure the temperatures on the Fins and tube of the flow and Surfaces. The experimental results showed that in the low Reynolds number regime, the heat transfer decreased continually from the entrance along the stream wise direction. However, in the high Reynolds number regime, the heat transfer had a maximum value in the middle points of the Fins along the stream wise direction. It was demonstrated through the numerical simulation and experimental results that the configuration of the Fin and tube with the LVGs on the Fins could attain enhanced heat transfer without too much pressure drop.
Liangbi Wang - One of the best experts on this subject based on the ideXlab platform.
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numerical study of flow and heat transfer enhancement of circular tube bank Fin heat exchanger with curved delta winglet vortex generators
Applied Thermal Engineering, 2015Co-Authors: Liangbi WangAbstract:Abstract To reduce the peeling wake area and generate longitudinal vortices at the rear of circular tube employed in tube bank Fin heat exchanger, a new Fin pattern with curved delta-winglet vortex generators (CDWVGs) punched on Fin Surface was proposed. A conjugate heat transfer numerical method is employed to investigate the heat transfer performance of the staggered circular tube bank Fin heat exchanger with CDWVGs. Their radial and circumferential locations, height and length are the main parameters to investigate. CDWVGs can not only guide the flow to reduce the size of the wake region, but also generate secondary flow to enhance heat transfer of the Fin Surface. CDWVGs can effectively enhance heat transfer under either identical pumping power or identical mass flow rate constrains. The optimal geometry parameters and position parameters of CDWVGs are found for the majority of studied Re. If the effect of the main working, geometry and position parameters on heat transfer is cast into the relationship between the secondary flow intensity and Nusslet number, the intensity of secondary flow mainly determines the heat transfer ability of the Fin Surface.
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heat transfer characteristics of a circular tube bank Fin heat exchanger with Fins punched curve rectangular vortex generators in the wake regions of the tubes
Applied Thermal Engineering, 2015Co-Authors: Bao Gong, Liangbi WangAbstract:Vortex generators (VGs) applied on the Fin Surfaces of circular tube bank Fin heat exchangers can increase the intensity of secondary flow and reduce the size of wake regions behind circular tubes. In this study, a new type of the Fin is reported, on which curve rectangular vortex generators (CRVGs) are punched. A numerical method is used to investigate the fluid flow and heat transfer characteristics of the Fin. The average Nusselt number, friction factor and secondary flow intensity are larger than that of the reference plain Fin at different Re, respectively. The local Nusselt number on the Fin Surface contacting with the wake region increases significantly. The circumferential position, the radial position, the base arc length and height of VGs and the Fin spacing are the main parameters investigated to disclose their effect on the heat transfer performance of the Fin. When the leading edge of VGs is located in the transversal axis of the tube, the diameter of the base arc length of VGs is large, the height of VGs is about 0.8 times of the Fin spacing, heat transfer performance is optimal, and the base arc length of VGs is about 3.8 times of the optimal height of VGs, better heat transfer performance can be obtained. For working condition of different Reynolds number, when the ratio of the Fin spacing to the tube outer diameter is 0.239, better heat transfer performance is obtained.
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Secondary flow intensity determines Nusselt number on the Fin Surfaces of circle tube bank Fin heat exchanger
International Journal of Heat and Mass Transfer, 2013Co-Authors: Wan-ling Hu, Ke-wei Song, Yong Guan, Li-min Chang, Liangbi WangAbstract:Abstract Secondary flow is the flow on the cross section normal to the main flow. It can greatly enhance the convective heat transfer. Mounting or punching vortex generators (VGs) on heat transfer Surface can produce secondary flow. The heat transfer of circle tube bank Fin heat exchanger with VGs or without VGs on the Fin Surface having ten different configurations (different Fin spacing, height and attack angle of VGs) was numerically studied. It is found that if a non-dimensional parameter based on the absolute vorticity flux is introduced to specify the intensity of secondary flow, the volume average non-dimensional intensity of secondary flow has one-to-one correlation with Nusselt number for all the cases studied, but there is no such correlation with the friction factor. Considering the pressure drop produced by the shape of VGs, the ratio of cross section area reduction after introducing VGs is introduced to modify the friction factor. At the same Fin spacing, both Reynolds number and the volume average non-dimensional intensity of secondary flow have one-to-one correlation with the modified friction factor. These results reveal that secondary flow intensity determines the heat transfer characteristics of the Fin Surfaces of circle tube bank Fin heat exchanger only.
Lijun Yang - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation on flow and heat transfer of Fin and tube heat exchanger with longitudinal vortex generators
International Journal of Thermal Sciences, 2015Co-Authors: Li Li, Xiaoze Du, Lijun Yang, Yuwen Zhang, Yongping YangAbstract:Abstract Fin-and-tube heat exchangers with plain Fins are widely used in direct air-cooled condenser system in the power plant, because of its relatively simple property compared to some other Fins with variable cross-sectional area channel. In the present study, heat transfer performance and pressure drop for Fin-and-tube heat exchanger with longitudinal vortex generators (LVGs) on the Fin Surface were numerically investigated. Rectangular and delta winglet pairs were punched/mounted on the Fin Surfaces to enhance the heat transfer of the air-side of the Fin-and-tube heat exchangers. The results showed that the Nusselt numbers increased up to 20% for LVGs on plain Fins comparing with plain Fins channel without LVGs. The heat transfer enhancement by rectangular winglets was more significant than that of the delta winglets. The rectangular winglet with angle of attack of 25°showed the best overall performance than any other angles of attack in rectangular winglets configurations. Additionally, the delta winglet with angle of attack of 45° showed the best overall performance than the other angles of attack in delta winglets configurations.
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heat transfer enhancement of wavy Finned flat tube by punched longitudinal vortex generators
International Journal of Heat and Mass Transfer, 2014Co-Authors: Xiaoze Du, Lili Feng, Li Li, Lijun Yang, Yongping YangAbstract:Abstract Punched longitudinal vortex generators (LVGs) were employed to enhance air-side heat transfer on the wavy Fin Surface of flat tube used in direct air-cooled condenser. The heat transfer enhancement of four types of the longitudinal vortex generators with different attack angles were compared by numerical simulations. It was found that the delta winglet pair with attack angle 25° could reach the greatest performance evaluation criteria (PEC) under the conditions of the inlet air flow velocity varied from 1 m/s to 5 m/s. The influences of locations on the wavy Fin Surface and the row number of the longitudinal vortex generators were also discussed. One delta winglet pairs at the middle of the wavy Fin Surface and the minimum row number, n = 1, with the average PEC is 1.23, has the best heat transfer performance of all conditions, which can be recommended for practical applications. Experimental study in wind tunnel with flow field visualization by Particle Image Velocimetry (PIV), as well as the numerical simulations verified that the delta winglet pairs can generate obvious longitudinal vortex pairs at the down-sweep zone, which can enhance the heat transfer between the cooling air flow and heated wall Surface with acceptable pressure loss.
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experimental study on heat transfer enhancement of wavy Finned flat tube with longitudinal vortex generators
Applied Thermal Engineering, 2013Co-Authors: Xiaoze Du, Lili Feng, Yongping Yang, Lijun YangAbstract:Abstract The performance of direct air-cooled condensers in power plant is affected significantly by air-side flow and heat transfer characteristics of the wavy Finned flat tube. Experimental investigations were conducted for air-side flow and heat transfer with and without delta winglet pairs punched on the Surface of the wavy Fin. The different temperature fields of the heated wavy Fin Surface with and without delta winglet pairs were obtained by the infrared thermography technology. Both experiments and numerical simulations showed that a substantial increase in the heat transfer with six delta winglet pair generators on the wavy Fin was obtained with the Reynolds number varying from 1500 to 4500, which was the range of the air flow in practical direct air-cooled condensers. The average Nusselt number increased by 21–60% with the Reynolds number varying from 1500 to 4500 and the average friction factor increased by 13–83% with the Reynolds number varying from 500 to 4500 in experiments. The average performance evaluation criteria, PEC, can be up to 1.31 with six delta winglet pairs punched on the wavy Fin Surface, indicating the high potential of heat transfer enhancement to direct air-cooled condensers by longitudinal vortex generators.
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experimental and numerical study of heat transfer over a Finned elliptical flat tube fitted with longitudinal vortex generators on the rectangular Fin Surface
Journal of Enhanced Heat Transfer, 2013Co-Authors: Li Li, Xiaoze Du, Lijun Yang, Yuwen Zhang, Chao Xu, Yongping YangAbstract:An experimental study of heat transfer over a Finned elliptical flat tube fitted with and without longitudinal vortex generators (LVGs) mounted on the rectangular Fins was carried out in a wind channel. Numerical simulation was performed to compare the experimental results and to verify the turbulence model. The test models were magnified four times greater than the original react model and correspondingly simplified according to the principle of similitude. Several Fins were designed to construct the periodic boundary condition. Thermo couples were used to measure the temperatures on the Fins and tube of the flow and Surfaces. The experimental results showed that in the low Reynolds number regime, the heat transfer decreased continually from the entrance along the stream wise direction. However, in the high Reynolds number regime, the heat transfer had a maximum value in the middle points of the Fins along the stream wise direction. It was demonstrated through the numerical simulation and experimental results that the configuration of the Fin and tube with the LVGs on the Fins could attain enhanced heat transfer without too much pressure drop.
Xiaoze Du - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation on flow and heat transfer of Fin and tube heat exchanger with longitudinal vortex generators
International Journal of Thermal Sciences, 2015Co-Authors: Li Li, Xiaoze Du, Lijun Yang, Yuwen Zhang, Yongping YangAbstract:Abstract Fin-and-tube heat exchangers with plain Fins are widely used in direct air-cooled condenser system in the power plant, because of its relatively simple property compared to some other Fins with variable cross-sectional area channel. In the present study, heat transfer performance and pressure drop for Fin-and-tube heat exchanger with longitudinal vortex generators (LVGs) on the Fin Surface were numerically investigated. Rectangular and delta winglet pairs were punched/mounted on the Fin Surfaces to enhance the heat transfer of the air-side of the Fin-and-tube heat exchangers. The results showed that the Nusselt numbers increased up to 20% for LVGs on plain Fins comparing with plain Fins channel without LVGs. The heat transfer enhancement by rectangular winglets was more significant than that of the delta winglets. The rectangular winglet with angle of attack of 25°showed the best overall performance than any other angles of attack in rectangular winglets configurations. Additionally, the delta winglet with angle of attack of 45° showed the best overall performance than the other angles of attack in delta winglets configurations.
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heat transfer enhancement of wavy Finned flat tube by punched longitudinal vortex generators
International Journal of Heat and Mass Transfer, 2014Co-Authors: Xiaoze Du, Lili Feng, Li Li, Lijun Yang, Yongping YangAbstract:Abstract Punched longitudinal vortex generators (LVGs) were employed to enhance air-side heat transfer on the wavy Fin Surface of flat tube used in direct air-cooled condenser. The heat transfer enhancement of four types of the longitudinal vortex generators with different attack angles were compared by numerical simulations. It was found that the delta winglet pair with attack angle 25° could reach the greatest performance evaluation criteria (PEC) under the conditions of the inlet air flow velocity varied from 1 m/s to 5 m/s. The influences of locations on the wavy Fin Surface and the row number of the longitudinal vortex generators were also discussed. One delta winglet pairs at the middle of the wavy Fin Surface and the minimum row number, n = 1, with the average PEC is 1.23, has the best heat transfer performance of all conditions, which can be recommended for practical applications. Experimental study in wind tunnel with flow field visualization by Particle Image Velocimetry (PIV), as well as the numerical simulations verified that the delta winglet pairs can generate obvious longitudinal vortex pairs at the down-sweep zone, which can enhance the heat transfer between the cooling air flow and heated wall Surface with acceptable pressure loss.
-
experimental study on heat transfer enhancement of wavy Finned flat tube with longitudinal vortex generators
Applied Thermal Engineering, 2013Co-Authors: Xiaoze Du, Lili Feng, Yongping Yang, Lijun YangAbstract:Abstract The performance of direct air-cooled condensers in power plant is affected significantly by air-side flow and heat transfer characteristics of the wavy Finned flat tube. Experimental investigations were conducted for air-side flow and heat transfer with and without delta winglet pairs punched on the Surface of the wavy Fin. The different temperature fields of the heated wavy Fin Surface with and without delta winglet pairs were obtained by the infrared thermography technology. Both experiments and numerical simulations showed that a substantial increase in the heat transfer with six delta winglet pair generators on the wavy Fin was obtained with the Reynolds number varying from 1500 to 4500, which was the range of the air flow in practical direct air-cooled condensers. The average Nusselt number increased by 21–60% with the Reynolds number varying from 1500 to 4500 and the average friction factor increased by 13–83% with the Reynolds number varying from 500 to 4500 in experiments. The average performance evaluation criteria, PEC, can be up to 1.31 with six delta winglet pairs punched on the wavy Fin Surface, indicating the high potential of heat transfer enhancement to direct air-cooled condensers by longitudinal vortex generators.
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experimental and numerical study of heat transfer over a Finned elliptical flat tube fitted with longitudinal vortex generators on the rectangular Fin Surface
Journal of Enhanced Heat Transfer, 2013Co-Authors: Li Li, Xiaoze Du, Lijun Yang, Yuwen Zhang, Chao Xu, Yongping YangAbstract:An experimental study of heat transfer over a Finned elliptical flat tube fitted with and without longitudinal vortex generators (LVGs) mounted on the rectangular Fins was carried out in a wind channel. Numerical simulation was performed to compare the experimental results and to verify the turbulence model. The test models were magnified four times greater than the original react model and correspondingly simplified according to the principle of similitude. Several Fins were designed to construct the periodic boundary condition. Thermo couples were used to measure the temperatures on the Fins and tube of the flow and Surfaces. The experimental results showed that in the low Reynolds number regime, the heat transfer decreased continually from the entrance along the stream wise direction. However, in the high Reynolds number regime, the heat transfer had a maximum value in the middle points of the Fins along the stream wise direction. It was demonstrated through the numerical simulation and experimental results that the configuration of the Fin and tube with the LVGs on the Fins could attain enhanced heat transfer without too much pressure drop.
Y M Kang - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of MWCNT–water nanofluids flow and convective heat transfer characteristics in multiport minichannels with smooth/micro-Fin Surface
Powder Technology, 2020Co-Authors: Y H Diao, C Z Li, Ji Zhang, Y H Zhao, Y M KangAbstract:Abstract This paper reports on the results of an experimental study on the heat transfer and flow performance of multiwalled carbon nanotubes (MWCNT) in aqueous suspensions flowing in multiport minichannel flat tubes with smooth/micro-Fin Surface under a constant heat flux condition. The MWCNT–water nanofluids volume concentrations are 0.001%, 0.005%, 0.01%, and 0.1%. Results indicate that the friction factor and the Nusselt number of the nanofluids are higher than those of water. The Nusselt number does not increase with volume concentration. The heat transfer of nanofluids in the micro-Fin tubes is higher than that of nanofluids in the smooth tube. However, the heat transfer enhancement of nanofluids in the micro-Fin tubes is lower than that of nanofluids in the smooth tube. The effect of micro-Fin spacing is more evident in nanofluids than in water. Nanofluids with a concentration of 0.01% flowing in the tube with closely spaced micro-Fin tube exhibit the optimal thermal performance in accordance with the performance evaluation criterion.
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experimental investigation of mwcnt water nanofluids flow and convective heat transfer characteristics in multiport minichannels with smooth micro Fin Surface
Powder Technology, 2017Co-Authors: Y H Diao, C Z Li, Ji Zhang, Y H Zhao, Y M KangAbstract:Abstract This paper reports on the results of an experimental study on the heat transfer and flow performance of multiwalled carbon nanotubes (MWCNT) in aqueous suspensions flowing in multiport minichannel flat tubes with smooth/micro-Fin Surface under a constant heat flux condition. The MWCNT–water nanofluids volume concentrations are 0.001%, 0.005%, 0.01%, and 0.1%. Results indicate that the friction factor and the Nusselt number of the nanofluids are higher than those of water. The Nusselt number does not increase with volume concentration. The heat transfer of nanofluids in the micro-Fin tubes is higher than that of nanofluids in the smooth tube. However, the heat transfer enhancement of nanofluids in the micro-Fin tubes is lower than that of nanofluids in the smooth tube. The effect of micro-Fin spacing is more evident in nanofluids than in water. Nanofluids with a concentration of 0.01% flowing in the tube with closely spaced micro-Fin tube exhibit the optimal thermal performance in accordance with the performance evaluation criterion.