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EFFECTS OF BLOCKAGE LOCATIONS FOR ENHANCED HEAT TRANSFER AND FLOW VISUALIZATION IN A TESTED DUCT WITH DUAL-INCLINED BAFFLES (DIB): A CFD ANALYSIS
(2022-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Numerical analysis of fluid flow mechanism and heat transfer in a heat exchanger duct (HXD) with dual-inclined baffles (DIB) are reported. Three DIB types are examined: 1. “Type A” is located at the center of the HXD, 2. “Type B” is located on the upper-lower duct walls (as an orifice) and 3. “Type C” is a combination of the type A and B (as double orifices). The impacts of the ratio of DIB heights (b) to the square duct height (H; b/H) on increased heat transfer and friction loss are analyzed. Laminar flow (Re = 100 – 2000 based on the entry condition of the tested duct) is discussed. The simulated problems of the HXD equipped with various DIB types are analyzed by a commercial code (the finite volume method). To confirm accuracy results, the simulated domain of the HXD with the DIB is validated (optimum grid check and smooth duct validation). The simulated solutions are illustrated in terms of heat transfer and flow features. The performance assessments of the HXD with different DIB types are also presented in terms of thermal enhancement factor, Nusselt number and friction factor. It is interesting that the changed DIB position at an identical flow-blockage-ratio leads to the changed flow structure that impacts the variations of both the Nusselt number and pressure drop of the HXD. It is found that type C DIB provides the greatest thermal potentiality. The heat transfer rate of the HXD equipped with type A, B and C DIB is 1.38 – 13.93, 1.00 – 14.19 and 1.31– 14.45 times higher than that of the smooth duct, respectively, depending on the DIB height and Reynolds number. Additionally, the best thermal enhancement factor (TEF) of 4.04 is found for the HXD with the type C DIB at b<inf>1</inf>/H = 0.05 and b<inf>2</inf>/H = 0.15 at Re = 2000.
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Numerical investigations on flow structure and heat transfer in a square duct equipped with double V-orifice
(2020-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Numerical predictions on heat transfer characteristic, flow topology and thermal performance assessment in a square duct are presented. The passive technique, insertion of the vortex generator, is opted to develop the heat transfer rate in the square duct heat exchanger. The vortex generator of the present research is Double V-Orifice (DVO). The square duct equipped with DVO is tested with various parameters. The influences of DVO height, b, to the duct height, H, or b/H, gap spacing between the outer edge of the orifice and the duct wall, s, to the duct height or s/H and flow directions (tip-pointing-Downstream and tip-pointing-Upstream) on flow pattern and heat transfer profile are considered for laminar flow regime with similar pitch, P, to duct height or P/H of 1. The Reynolds number, Re, based on the hydraulic diameter, D<inf>h</inf>, of the square duct around 100 – 2000 is discussed. The numerical model is solved with the commercial software (finite volume method). As the numerical result, the square duct inserted with the DVO offers greater Nusselt number, Nu, than the plain duct around 1.00 – 14.80 times. The maximum thermal enhancement factor, TEF, for the square duct inserted with the DVO is found to be about 3.60 depended on s/H, b/H and flow direction. The flow and heat transfer profiles in the square duct inserted with the DVO are also illustrated.
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Thermal performance improvement in a square channel heat exchanger with various parameters of V-wavy plates
(2019-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Numerical examinations on flow and heat transfer behaviors in a square channel heat exchanger equipped with various configurations of V-wavy plate are performed. The pitch-to-channel height ratios, wavy height-to-channel height ratios and flow directions of the test section are investigated for the Reynolds number in the range of 100 – 1000 (laminar flow regime). The finite volume method is selected for the present investigation. The results are reported in terms of flow and heat transfer mechanisms in the channel. The thermal performance assessments of the square channel fitted with the V-wavy plate are also concluded. As the numerical results, the V-wavy plate can produce the swirling flow through the heating channel. The swirling flow disturbs the thermal boundary layer on the heat transfer surface that leads to enhance heat transfer rate and thermal efficiency.
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Flow and heat transfer characteristics of air in square channel heat exchanger with c-shaped baffle: A numerical study
(2019-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
The purpose of the present work is to study flow configuration and heat transfer behavior in a square channel heat exchanger equipped with C-shaped baffle. The influences of flow attack angle and baffle size on flow and heat transfer characteristics are considered for the laminar flow regime with the Reynolds number around 100 – 2000. The numerical study with finite volume method is selected for the present investigation. The SIMPLE algorithms is opted to solve the numerical problem. The numerical results are concluded in terms of flow and heat transfer mechanisms in the tested section. The thermal performance analysis; Nusselt number ratio (Nu/Nu0), friction factor (f/f0) and thermal enhancement factor (TEF), are also summarized. The numerical model of the smooth square channel is validated with the correlations on both Nusselt number and friction factor. The numbers of grid cell for the computational domain are also compared. The numerical results reveal that the C-shaped baffle in the tested section leads to the appearance of the thermal boundary layer disturbance on the channel walls that the important cause for heat transfer rate and thermal efficiency enhancements. The maximum TEF of the square duct with C-shaped baffle is around 3.89. In addition, the optimum gap spacing value for the square channel inserted with C-shaped baffle is around 5%.
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Influence of ring size and location on flow topology, heat transfer structure and thermal efficiency in heat exchanger square channel placed with 30-degree inclined square ring
(2019-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
This paper presents the numerical investigations (finite volume method with SIMPLE algorithm) on flow structure, heat transfer behavior and performance assessment in heat exchanger square channel placed with 30<sup>o</sup> inclined square ring (ISR). The influences of ring size and placement on flow and heat transfer characteristics are considered for laminar flow region with the Reynolds number in the range around 100 – 2000. The purpose for the insertion of the ISR in the square channel is to induce the vortex flow and also increase the turbulent mixing. The numerical result reveals that the ring size and location have effects for the changes of the flow and heat transfer behaviors in the tested section. The present of the ISR in the tested section gives the maximum heat transfer rate around 8.13 times above the smooth square channel. In addition, the optimum thermal performance at similar pumping power or TEF is around 3.10.
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Effect of geometrical parameters on turbulent flow and heat transfer behaviors in triple-start corrugated tubes
(2018-01-01)
Promthaisong, Pitak
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Jedsadaratanachai, Withada
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Eiamsa-Ard, Smith
Computational results of flow structure, pressure loss and heat transfer characteristics in triple-start corrugated tubes are reported. The influences of the depth ratio (DR = 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14 and 0.16) and pitch ratio (PR = 0.5, 0.65, 0.75, 1.0, 1.5 and 2.0) were investigated in turbulent flow regime, Re = 5000 to 20,000. The computational results indicated that the triple-start corrugated tubes generate main swirl flow and helical swirl flow which helps to reduce the thermal boundary layer thickness and enhance the heat transfer rate. The flow and heat transfer become under fully developed periodic condition around x/D = 6.0. The friction factor monotonically increases with the rise of DR values and decrease PR values while maximum heat transfer rate is found at DR = 0.08 and PR = 0.75. Nusselt numbers and friction factors of triple-start corrugated tubes in the investigated range are found to be 0.8 to 2.31 and 1.0 to 17.14 times over those of the straight circular smooth tube, respectively. For the range studied, the triple-start corrugated tube with DR = 0.06 and PR = 0.75 offers the maximum thermal enhancement factor of 1.21 at Re = 5000.
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Numerical predictions on flow and heat transfer in heat exchanger tube equipped with various flow attack angles of inclined-wavy surface
(2018-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
Numerical analysis on flow configuration, heat transfer behavior and thermal performance in the heat exchanger tube equipped with various flow attack angles of the inclined wavy surface are presented. The laminar flow (Re = 100 – 1200) and turbulent flow (Re = 3000 – 10000) are considered for the present investigation. The flow attack angles of the inclined wavy surface are varied as 15° – 60°. The finite volume method with SIMPLE algorithm is selected to evaluate the current problem. The numerical results are reported in terms of flow and heat transfer mechanisms. The performance evaluations in forms of the Nusselt number ratio (Nu/Nu<inf>0</inf>), friction factor ratio (f/f<inf>0</inf>) and thermal enhancement factor (TEF) are also concluded. As the results, the vortex flow, impinging flow and thermal boundary layer disturbance are detected when inserted the inclined wavy surface in the heat exchanger tube. These behaviors effect for the augmentation of the heat transfer rate, pressure loss and thermal performance. The optimum flow attack angle of the inclined wavy surface for the laminar and turbulent flows are also concluded.
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Effect of location in transverse plane for 45-degree V-baffle on flow and heat transfer mechanisms in a square channel
(2018-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
Numerical predictions on flow and heat transfer in a square channel heat exchanger placed with V-baffle are examined. The gap spacing between the V-baffle and channel wall is varied for all baffle heights. The laminar regime with Re = 100 - 1000 is considered. The numerical model for the square channel heat exchanger placed with V-baffle is validated. The preliminary result reveals that the computational domain has reliability to predict flow and heat transfer in the channel. The mechanisms on flow and heat transfer in the heat exchanger channel are illustrated at the numerical result section. The thermal performance analysis of the heating section when inserted with the V-baffle is also reported in forms of the Nusselt number ratio (Nu/Nu0 or NuR), friction factor ratio (f/f0 or fR) and thermal enhancement factor (TEF). As the results, it is found the gap spacing has extremely effect for flow structure and heat transfer behavior in the test section. The optimum gap spacing ratio may help to reduce the pressure loss or improves the heat transfer rate in the channel heat exchanger. The selection for the gap spacing ratio in the heating section at various baffle heights is also concluded. In addition, the gap spacing ratio around 5 - 10% is suggested for the range investigation.
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3D numerical investigation on laminar forced convection and heat transfer in a circular tube inserted with right triangular wavy surfaces
(2017-01-01)
Jedsadaratanachai, Withada
;
Boonloi, Amnart
Numerical investigations on flow and heat transfer characteristics in a circular tube heat exchanger inserted with right triangular wavy surfaces are reported. The configurations of the wavy surfaces; incline and V-shape, are studied with flow attack angles of 30°, 45° and 60° for the Reynolds numbers, Re = 100-2000. The numerical results are compared with the smooth circular tube. The mechanisms on flow and heat transfer in the tube heat exchanger with the wavy surface are presented. As the results, the wavy surface can generate the vortex flow and impinging flow through the test section that helps to improve the heat transfer rate and thermal performance. The impingement of the flow on the tube wall disturbs the thermal boundary layer that is an important factor to enhance the heat transfer rate. The V-Downstream wavy surface can create the highest strength of the impinging flow that leads to the highest heat transfer rate. In the range investigate, the augmentations are around 1.2-7.6 and 4-43.6 times above the smooth tube for the heat transfer and friction loss, respectively. In addition, the optimum thermal enhancement factor, TEF, is around 2.42 for the V-Downstream wavy surface at α = 30° and Re = 2000.
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Numerical investigation on turbulent forced convection and heat transfer characteristic in spirally semicircle-grooved tube
(2016-12-01)
Promthaisong, Pitak
;
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Turbulent forced convection and heat transfer structure in the spirally semicircle-grooved tube heat exchanger are numerically examined. The computational problem is solved by finite volume method (FVM) with the SIMPLE algorithm. The influences of groove depth and helical pitch on heat transfer, pressure loss, and thermal performance are investigated for turbulent regime, Re = 5000–20,000. As a result, the swirling flow is found through the test section due to the groove on the tube wall. The flow structure in the spirally semicircle-grooved tube can separate into two types: main and secondary swirling flows. The main swirling flow is found in all cases, while the secondary swirling flow is detected when DR ≥ 0.06. The swirling flow disturbs the thermal boundary layer on the tube wall that is an important reason for heat transfer augmentation. In range studies, the enhancements on heat transfer and friction loss are around 1.16–1.96 and 1.2–10.8 time above the smooth tube, respectively. The optimum thermal performance is around 1.11, which detected at DR = 0.06, PR =1.4,andRe = 5000. The correlations of the Nusselt number and friction factor for the spirally semicircle-grooved tube with PR =1.4 are produced to help to design the tube heat exchanger.

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