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Suguru Masuzaki - One of the best experts on this subject based on the ideXlab platform.
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influence of boiling initiation surface superheat on subcooled water flow boiling critical heat flux in a sus304 Circular Tube at high liquid reynolds number
International Journal of Heat and Mass Transfer, 2016Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:Abstract The subcooled boiling heat transfer and the steady-state critical heat flux (CHF) in a vertical Circular Tube for the liquid Reynolds numbers ( Re d = 3.65 × 10 4 –3.08 × 10 5 ) and the flow velocities ( u = 3.95–30.80 m/s) were systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test Tube of inner diameter ( d = 6 mm) and heated length ( L = 59.5 mm) was used in this work. The boiling initiation noise of outer surface of the test Tube in the open air was simultaneously measured up to CHF point by the sound level meter (SLM) and the microphone of a video camera (MP). The outer surface temperatures of the SUS304 test Tube with heating were also observed by an infrared thermal imaging camera (ITIC) and the color temperatures of outer surface of the test Tube in the open air were observed by a video camera (VC). The subcooled boiling heat transfer and CHF for SUS304 Circular Tube were compared with the values calculated by authors’ and other researchers’ correlations for the subcooled flow boiling heat transfer. The influences of flow velocity on the boiling initiation surface heat flux, the boiling initiation surface superheat, the subcooled boiling heat transfer and the CHF were investigated into details based on the experimental data. At the flow velocities higher than 13.3 m/s, boiling initiation surface heat fluxes were close to the CHFs and surface superheats at the CHF were over to the homogeneous spontaneous nucleation temperature as well as the lower limit of the heterogeneous spontaneous nucleation temperature. The dominant mechanism of the subcooled water flow boiling CHF on the SUS304 Circular Tube was discussed at high liquid Reynolds number.
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mechanism of critical heat flux during flow boiling of subcooled water in a Circular Tube at high liquid reynolds number
Experimental Thermal and Fluid Science, 2016Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:The subcooled boiling heat transfer and the steady state critical heat flux (CHF) in a vertical Circular Tube for the liquid Reynolds numbers (Red = 2.77 × 104–3.08 × 105) and the flow velocities (u = 3.95–30.80 m/s) are systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test Tube of inner diameter (d = 6 mm) and heated length (L = 59.5 mm) is used in this work. The outer surface temperatures of the SUS304 test Tube with heating are observed by an infrared thermal imaging camera and a video camera. The subcooled boiling heat transfers for SUS304 test Tube are compared with the values calculated from correlations due to other researchers for the subcooled boiling heat transfer. The influence of flow velocity on the subcooled boiling heat transfer and the CHF is investigated in detail based on the experimental data. Nucleate boiling surface superheats at the CHF are close to the lower limit of the heterogeneous spontaneous nucleation temperature and the homogeneous spontaneous nucleation temperature. A suggestion as to what the dominant mechanism is for the subcooled flow boiling CHF on the SUS304 Circular Tube is made at high liquid Reynolds number. On the other hand, the RANS equations (Reynolds Averaged Navier–Stokes Simulation) with k–e turbulent model in a Circular Tube of a 3 mm in diameter and a 526 mm long are numerically solved for heating of water on heated section of a 3 mm in diameter and a 67 mm long with various thicknesses of conductive sub-layer by using PHOENICS code under the same conditions as the experimental ones previously obtained and with temperature dependent thermo-physical fluid properties. The Platinum (Pt) test Tube of inner diameter (d = 3 mm) and heated length (L = 66.5 mm) was used in this experiment. The thicknesses of conductive sub-layer from non-boiling regime to CHF are measured. The thicknesses of conductive sub-layer at the CHF point are predicted for various flow velocities. The experimental values of the CHF are also compared with the corresponding theoretical values of the liquid sub-layer dry-out models suggested by other researchers, respectively. A suggestion as to what the dominant mechanism is for the subcooled flow boiling CHF on the Pt Circular Tube is made at high liquid Reynolds number.
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transient critical heat fluxes of subcooled water flow boiling in a sus304 Circular Tube caused by a rapid decrease in velocity from non boiling regime
Experimental Thermal and Fluid Science, 2015Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:Abstract The flow transient critical heat fluxes (FT-CHFs, qcr,sub) in a SUS304-Circular Tube caused by a rapid decrease in velocity from non-boiling regime are systematically measured for various initial flow velocities, initial heat fluxes, inlet liquid temperatures, outlet pressures and decelerations caused by a rapid decrease in velocity by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-Circular Tubes of inner diameter (d = 6 mm), heated length (L = 59.5 mm), L/d (=9.92) and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.89 μm) are used in this work. The flow transient CHFs for SUS304-Circular Tube are compared with authors’ steady-state CHF data for the empty VERTICAL and HORIZONTAL SUS304-Circular Tubes and the values calculated by authors’ steady-state CHF correlations against outlet and inlet subcoolings for the empty Circular Tube. The influences of initial flow velocity (u0), initial heat flux (q0) and deceleration caused by a rapid decrease in velocity (α) on the flow transient CHF are investigated into details and the widely and precisely predictable correlations of CHF and flow velocity at the flow transient CHF for the Circular Tube is given based on the experimental data. The correlations can describe the flow velocity and the CHFs at the flow transient CHFs for SUS304-Circular Tube obtained in this work within ± 20% difference.
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transient critical heat fluxes of subcooled water flow boiling in a sus304 Circular Tube caused by a rapid decrease in velocity from non boiling regime
2014 22nd International Conference on Nuclear Engineering, 2014Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:The flow transient critical heat fluxes (FT-CHFs, qcr,sub) in a SUS304-Circular Tube caused by a rapid decrease in velocity from non-boiling regime are systematically measured for initial flow velocities (u0=7.057 to 13.635 m/s for conditions of u0=6.9, 9.9 and 13.3 m/s), initial heat fluxes (q0=15.59 to 17.34 MW/m2), inlet liquid temperatures (Tin=290.12 to 308.51 K), outlet pressures (Pout=698.38 to 1288.97 kPa) and decelerations caused by a rapid decrease in velocity (u(t)=u0+αt, α=−7.357 to −0.326 m/s2) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-Circular Tubes of inner diameter (d=6 mm), heated length (L=59.5 to 59.7 mm), effective length (Leff=48.7 to 50.2 mm), L/d (=9.92 to 9.95), Leff/d (=8.12 to 8.37) and wall thickness (δ=0.5 mm) with average surface roughness (Ra=3.89 μm) are used in this work. The flow transient CHFs for SUS304-Circular Tube are compared with authors’ steady-state CHF data for the empty VERTICAL and HORIZONTAL SUS304-Circular Tubes and the values calculated by authors’ steady-state CHF correlations against outlet and inlet subcoolings for the empty Circular Tube. The influences of initial flow velocity (u0), initial heat flux (q0) and deceleration caused by a rapid decrease in velocity (α) on the flow transient CHF are investigated into details and the widely and precisely predictable correlations of CHF and flow velocity at the flow transient CHF for the Circular Tube is given based on the experimental data. The correlations can describe the flow velocity and the CHFs at the flow transient CHFs for SUS304-Circular Tube obtained in this work within ±20 % difference.Copyright © 2014 by ASME
Koichi Hata - One of the best experts on this subject based on the ideXlab platform.
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influence of boiling initiation surface superheat on subcooled water flow boiling critical heat flux in a sus304 Circular Tube at high liquid reynolds number
International Journal of Heat and Mass Transfer, 2016Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:Abstract The subcooled boiling heat transfer and the steady-state critical heat flux (CHF) in a vertical Circular Tube for the liquid Reynolds numbers ( Re d = 3.65 × 10 4 –3.08 × 10 5 ) and the flow velocities ( u = 3.95–30.80 m/s) were systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test Tube of inner diameter ( d = 6 mm) and heated length ( L = 59.5 mm) was used in this work. The boiling initiation noise of outer surface of the test Tube in the open air was simultaneously measured up to CHF point by the sound level meter (SLM) and the microphone of a video camera (MP). The outer surface temperatures of the SUS304 test Tube with heating were also observed by an infrared thermal imaging camera (ITIC) and the color temperatures of outer surface of the test Tube in the open air were observed by a video camera (VC). The subcooled boiling heat transfer and CHF for SUS304 Circular Tube were compared with the values calculated by authors’ and other researchers’ correlations for the subcooled flow boiling heat transfer. The influences of flow velocity on the boiling initiation surface heat flux, the boiling initiation surface superheat, the subcooled boiling heat transfer and the CHF were investigated into details based on the experimental data. At the flow velocities higher than 13.3 m/s, boiling initiation surface heat fluxes were close to the CHFs and surface superheats at the CHF were over to the homogeneous spontaneous nucleation temperature as well as the lower limit of the heterogeneous spontaneous nucleation temperature. The dominant mechanism of the subcooled water flow boiling CHF on the SUS304 Circular Tube was discussed at high liquid Reynolds number.
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mechanism of critical heat flux during flow boiling of subcooled water in a Circular Tube at high liquid reynolds number
Experimental Thermal and Fluid Science, 2016Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:The subcooled boiling heat transfer and the steady state critical heat flux (CHF) in a vertical Circular Tube for the liquid Reynolds numbers (Red = 2.77 × 104–3.08 × 105) and the flow velocities (u = 3.95–30.80 m/s) are systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test Tube of inner diameter (d = 6 mm) and heated length (L = 59.5 mm) is used in this work. The outer surface temperatures of the SUS304 test Tube with heating are observed by an infrared thermal imaging camera and a video camera. The subcooled boiling heat transfers for SUS304 test Tube are compared with the values calculated from correlations due to other researchers for the subcooled boiling heat transfer. The influence of flow velocity on the subcooled boiling heat transfer and the CHF is investigated in detail based on the experimental data. Nucleate boiling surface superheats at the CHF are close to the lower limit of the heterogeneous spontaneous nucleation temperature and the homogeneous spontaneous nucleation temperature. A suggestion as to what the dominant mechanism is for the subcooled flow boiling CHF on the SUS304 Circular Tube is made at high liquid Reynolds number. On the other hand, the RANS equations (Reynolds Averaged Navier–Stokes Simulation) with k–e turbulent model in a Circular Tube of a 3 mm in diameter and a 526 mm long are numerically solved for heating of water on heated section of a 3 mm in diameter and a 67 mm long with various thicknesses of conductive sub-layer by using PHOENICS code under the same conditions as the experimental ones previously obtained and with temperature dependent thermo-physical fluid properties. The Platinum (Pt) test Tube of inner diameter (d = 3 mm) and heated length (L = 66.5 mm) was used in this experiment. The thicknesses of conductive sub-layer from non-boiling regime to CHF are measured. The thicknesses of conductive sub-layer at the CHF point are predicted for various flow velocities. The experimental values of the CHF are also compared with the corresponding theoretical values of the liquid sub-layer dry-out models suggested by other researchers, respectively. A suggestion as to what the dominant mechanism is for the subcooled flow boiling CHF on the Pt Circular Tube is made at high liquid Reynolds number.
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transient critical heat fluxes of subcooled water flow boiling in a sus304 Circular Tube caused by a rapid decrease in velocity from non boiling regime
Experimental Thermal and Fluid Science, 2015Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:Abstract The flow transient critical heat fluxes (FT-CHFs, qcr,sub) in a SUS304-Circular Tube caused by a rapid decrease in velocity from non-boiling regime are systematically measured for various initial flow velocities, initial heat fluxes, inlet liquid temperatures, outlet pressures and decelerations caused by a rapid decrease in velocity by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-Circular Tubes of inner diameter (d = 6 mm), heated length (L = 59.5 mm), L/d (=9.92) and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.89 μm) are used in this work. The flow transient CHFs for SUS304-Circular Tube are compared with authors’ steady-state CHF data for the empty VERTICAL and HORIZONTAL SUS304-Circular Tubes and the values calculated by authors’ steady-state CHF correlations against outlet and inlet subcoolings for the empty Circular Tube. The influences of initial flow velocity (u0), initial heat flux (q0) and deceleration caused by a rapid decrease in velocity (α) on the flow transient CHF are investigated into details and the widely and precisely predictable correlations of CHF and flow velocity at the flow transient CHF for the Circular Tube is given based on the experimental data. The correlations can describe the flow velocity and the CHFs at the flow transient CHFs for SUS304-Circular Tube obtained in this work within ± 20% difference.
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transient critical heat fluxes of subcooled water flow boiling in a sus304 Circular Tube caused by a rapid decrease in velocity from non boiling regime
2014 22nd International Conference on Nuclear Engineering, 2014Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:The flow transient critical heat fluxes (FT-CHFs, qcr,sub) in a SUS304-Circular Tube caused by a rapid decrease in velocity from non-boiling regime are systematically measured for initial flow velocities (u0=7.057 to 13.635 m/s for conditions of u0=6.9, 9.9 and 13.3 m/s), initial heat fluxes (q0=15.59 to 17.34 MW/m2), inlet liquid temperatures (Tin=290.12 to 308.51 K), outlet pressures (Pout=698.38 to 1288.97 kPa) and decelerations caused by a rapid decrease in velocity (u(t)=u0+αt, α=−7.357 to −0.326 m/s2) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-Circular Tubes of inner diameter (d=6 mm), heated length (L=59.5 to 59.7 mm), effective length (Leff=48.7 to 50.2 mm), L/d (=9.92 to 9.95), Leff/d (=8.12 to 8.37) and wall thickness (δ=0.5 mm) with average surface roughness (Ra=3.89 μm) are used in this work. The flow transient CHFs for SUS304-Circular Tube are compared with authors’ steady-state CHF data for the empty VERTICAL and HORIZONTAL SUS304-Circular Tubes and the values calculated by authors’ steady-state CHF correlations against outlet and inlet subcoolings for the empty Circular Tube. The influences of initial flow velocity (u0), initial heat flux (q0) and deceleration caused by a rapid decrease in velocity (α) on the flow transient CHF are investigated into details and the widely and precisely predictable correlations of CHF and flow velocity at the flow transient CHF for the Circular Tube is given based on the experimental data. The correlations can describe the flow velocity and the CHFs at the flow transient CHFs for SUS304-Circular Tube obtained in this work within ±20 % difference.Copyright © 2014 by ASME
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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numerical study on heat transfer enhancement of Circular Tube bank fin heat exchanger with interrupted annular groove fin
Applied Thermal Engineering, 2014Co-Authors: Liangbi Wang, Yongheng ZhangAbstract:Abstract A variation in fin surface geometry is an effective approach to improve streamline pattern when fluid flows through the channel form by Circular Tube bank fins. The structure of interrupted half annular groove (IHAG) fin is different from commonly used fin patterns. In this paper, a conjugate heat transfer numerical method is employed to investigate the average heat transfer and fluid flow characteristics of the staggered Circular Tube bank fin heat exchanger with IHAG fin. The reference fin is the plain fin with a corresponding configuration. The annular groove's radial and circumferential locations are the main parameters to investigate. The results reveal that (1) The interrupted annular groove has dual efficacy of fluid flow guiding and detached eddy inhibition to reduce the size of wake region; (2) At lower Reynolds numbers, the interrupted annular groove fin surface could not efficiently enhance heat transfer under identical pumping power criteria, and the excellent performance of the interrupted annular groove fin can be achieved at higher Reynolds numbers. There is an average 35% increase in the friction factor, while for Reynolds number ranged from 600 to 2500, the average Nusselt number is increased by 10%–40%, and the corresponding thermal performance factor ranges from 7% to 27%; (3) The studied annular groove's radial and circumferential locations have a fairly limited effect on the average heat transfer and fluid flow characteristics.
Katsuya Fukuda - One of the best experts on this subject based on the ideXlab platform.
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influence of boiling initiation surface superheat on subcooled water flow boiling critical heat flux in a sus304 Circular Tube at high liquid reynolds number
International Journal of Heat and Mass Transfer, 2016Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:Abstract The subcooled boiling heat transfer and the steady-state critical heat flux (CHF) in a vertical Circular Tube for the liquid Reynolds numbers ( Re d = 3.65 × 10 4 –3.08 × 10 5 ) and the flow velocities ( u = 3.95–30.80 m/s) were systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test Tube of inner diameter ( d = 6 mm) and heated length ( L = 59.5 mm) was used in this work. The boiling initiation noise of outer surface of the test Tube in the open air was simultaneously measured up to CHF point by the sound level meter (SLM) and the microphone of a video camera (MP). The outer surface temperatures of the SUS304 test Tube with heating were also observed by an infrared thermal imaging camera (ITIC) and the color temperatures of outer surface of the test Tube in the open air were observed by a video camera (VC). The subcooled boiling heat transfer and CHF for SUS304 Circular Tube were compared with the values calculated by authors’ and other researchers’ correlations for the subcooled flow boiling heat transfer. The influences of flow velocity on the boiling initiation surface heat flux, the boiling initiation surface superheat, the subcooled boiling heat transfer and the CHF were investigated into details based on the experimental data. At the flow velocities higher than 13.3 m/s, boiling initiation surface heat fluxes were close to the CHFs and surface superheats at the CHF were over to the homogeneous spontaneous nucleation temperature as well as the lower limit of the heterogeneous spontaneous nucleation temperature. The dominant mechanism of the subcooled water flow boiling CHF on the SUS304 Circular Tube was discussed at high liquid Reynolds number.
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mechanism of critical heat flux during flow boiling of subcooled water in a Circular Tube at high liquid reynolds number
Experimental Thermal and Fluid Science, 2016Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:The subcooled boiling heat transfer and the steady state critical heat flux (CHF) in a vertical Circular Tube for the liquid Reynolds numbers (Red = 2.77 × 104–3.08 × 105) and the flow velocities (u = 3.95–30.80 m/s) are systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test Tube of inner diameter (d = 6 mm) and heated length (L = 59.5 mm) is used in this work. The outer surface temperatures of the SUS304 test Tube with heating are observed by an infrared thermal imaging camera and a video camera. The subcooled boiling heat transfers for SUS304 test Tube are compared with the values calculated from correlations due to other researchers for the subcooled boiling heat transfer. The influence of flow velocity on the subcooled boiling heat transfer and the CHF is investigated in detail based on the experimental data. Nucleate boiling surface superheats at the CHF are close to the lower limit of the heterogeneous spontaneous nucleation temperature and the homogeneous spontaneous nucleation temperature. A suggestion as to what the dominant mechanism is for the subcooled flow boiling CHF on the SUS304 Circular Tube is made at high liquid Reynolds number. On the other hand, the RANS equations (Reynolds Averaged Navier–Stokes Simulation) with k–e turbulent model in a Circular Tube of a 3 mm in diameter and a 526 mm long are numerically solved for heating of water on heated section of a 3 mm in diameter and a 67 mm long with various thicknesses of conductive sub-layer by using PHOENICS code under the same conditions as the experimental ones previously obtained and with temperature dependent thermo-physical fluid properties. The Platinum (Pt) test Tube of inner diameter (d = 3 mm) and heated length (L = 66.5 mm) was used in this experiment. The thicknesses of conductive sub-layer from non-boiling regime to CHF are measured. The thicknesses of conductive sub-layer at the CHF point are predicted for various flow velocities. The experimental values of the CHF are also compared with the corresponding theoretical values of the liquid sub-layer dry-out models suggested by other researchers, respectively. A suggestion as to what the dominant mechanism is for the subcooled flow boiling CHF on the Pt Circular Tube is made at high liquid Reynolds number.
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transient critical heat fluxes of subcooled water flow boiling in a sus304 Circular Tube caused by a rapid decrease in velocity from non boiling regime
Experimental Thermal and Fluid Science, 2015Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:Abstract The flow transient critical heat fluxes (FT-CHFs, qcr,sub) in a SUS304-Circular Tube caused by a rapid decrease in velocity from non-boiling regime are systematically measured for various initial flow velocities, initial heat fluxes, inlet liquid temperatures, outlet pressures and decelerations caused by a rapid decrease in velocity by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-Circular Tubes of inner diameter (d = 6 mm), heated length (L = 59.5 mm), L/d (=9.92) and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.89 μm) are used in this work. The flow transient CHFs for SUS304-Circular Tube are compared with authors’ steady-state CHF data for the empty VERTICAL and HORIZONTAL SUS304-Circular Tubes and the values calculated by authors’ steady-state CHF correlations against outlet and inlet subcoolings for the empty Circular Tube. The influences of initial flow velocity (u0), initial heat flux (q0) and deceleration caused by a rapid decrease in velocity (α) on the flow transient CHF are investigated into details and the widely and precisely predictable correlations of CHF and flow velocity at the flow transient CHF for the Circular Tube is given based on the experimental data. The correlations can describe the flow velocity and the CHFs at the flow transient CHFs for SUS304-Circular Tube obtained in this work within ± 20% difference.
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transient critical heat fluxes of subcooled water flow boiling in a sus304 Circular Tube caused by a rapid decrease in velocity from non boiling regime
2014 22nd International Conference on Nuclear Engineering, 2014Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:The flow transient critical heat fluxes (FT-CHFs, qcr,sub) in a SUS304-Circular Tube caused by a rapid decrease in velocity from non-boiling regime are systematically measured for initial flow velocities (u0=7.057 to 13.635 m/s for conditions of u0=6.9, 9.9 and 13.3 m/s), initial heat fluxes (q0=15.59 to 17.34 MW/m2), inlet liquid temperatures (Tin=290.12 to 308.51 K), outlet pressures (Pout=698.38 to 1288.97 kPa) and decelerations caused by a rapid decrease in velocity (u(t)=u0+αt, α=−7.357 to −0.326 m/s2) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-Circular Tubes of inner diameter (d=6 mm), heated length (L=59.5 to 59.7 mm), effective length (Leff=48.7 to 50.2 mm), L/d (=9.92 to 9.95), Leff/d (=8.12 to 8.37) and wall thickness (δ=0.5 mm) with average surface roughness (Ra=3.89 μm) are used in this work. The flow transient CHFs for SUS304-Circular Tube are compared with authors’ steady-state CHF data for the empty VERTICAL and HORIZONTAL SUS304-Circular Tubes and the values calculated by authors’ steady-state CHF correlations against outlet and inlet subcoolings for the empty Circular Tube. The influences of initial flow velocity (u0), initial heat flux (q0) and deceleration caused by a rapid decrease in velocity (α) on the flow transient CHF are investigated into details and the widely and precisely predictable correlations of CHF and flow velocity at the flow transient CHF for the Circular Tube is given based on the experimental data. The correlations can describe the flow velocity and the CHFs at the flow transient CHFs for SUS304-Circular Tube obtained in this work within ±20 % difference.Copyright © 2014 by ASME
Yongheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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numerical study on heat transfer enhancement of Circular Tube bank fin heat exchanger with interrupted annular groove fin
Applied Thermal Engineering, 2014Co-Authors: Liangbi Wang, Yongheng ZhangAbstract:Abstract A variation in fin surface geometry is an effective approach to improve streamline pattern when fluid flows through the channel form by Circular Tube bank fins. The structure of interrupted half annular groove (IHAG) fin is different from commonly used fin patterns. In this paper, a conjugate heat transfer numerical method is employed to investigate the average heat transfer and fluid flow characteristics of the staggered Circular Tube bank fin heat exchanger with IHAG fin. The reference fin is the plain fin with a corresponding configuration. The annular groove's radial and circumferential locations are the main parameters to investigate. The results reveal that (1) The interrupted annular groove has dual efficacy of fluid flow guiding and detached eddy inhibition to reduce the size of wake region; (2) At lower Reynolds numbers, the interrupted annular groove fin surface could not efficiently enhance heat transfer under identical pumping power criteria, and the excellent performance of the interrupted annular groove fin can be achieved at higher Reynolds numbers. There is an average 35% increase in the friction factor, while for Reynolds number ranged from 600 to 2500, the average Nusselt number is increased by 10%–40%, and the corresponding thermal performance factor ranges from 7% to 27%; (3) The studied annular groove's radial and circumferential locations have a fairly limited effect on the average heat transfer and fluid flow characteristics.