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IMPACT OF THREE DIFFERENT DOUBLE BAFFLE DESIGNS ON THE THERMAL PERFORMANCE OF SQUARE DUCTS
(2022-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
CFD analyses of flow characteristics and heat transfer topology in a heat exchanger duct (HXD) placed with three various configurations of the double V-baffles (DVB) are reported. Parameters of interest are DVB height ratios (b/H = 0.05 – 0.25), gap spacing ratios (g = 0.05 – 0.40), flow directions (+x,-x), and DVB configurations (Type I, II and III). Laminar flow with Reynolds numbers (based on the inlet conditions) between 100 – 2000 is measured. The present problem is solved with the finite volume method (a commercial program). Fluid flow and heat transfer characteristics in the tested duct are described. Thermal assessments of the tested duct are also presented. Simulation results showed that the installation of the DVB in the HXD results in higher heat transfer rate due to the creation of the vortex flow and the disturbance of the thermal boundary layer (TBL). Different flow structures and heat transfer behavior are observed when gap spacing ratios, flow directions and DVB shapes are changed. In addition, the type II DVB provides the highest TEF of 3.55 at b/H = 0.10, g/H = 0.25 for the-x flow direction.
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Variations of heat transfer mechanism and flow structure in a heat exchanger tube fitted with 30° inclined ring
(2020-03-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Flow prediction, heat transfer pattern, and thermo-hydraulic efficiency in a heat exchanger tube fitted with vortex generator are chosen for the present research. The 30° inclined ring is opted to develop the performance of the heat exchanger tube. The effects of inclined ring configuration and placement in the heat exchanger tube on the patterns of flow and heat transfer are investigated. The Reynolds number (at the entry zone of the periodic model) in the range of around 100–2000 (laminar flow region) is discussed. The heat transfer ability, pressure loss, and efficiency of the heat exchanger tube fitted with 30° inclined ring are analyzed with the numerical method (finite volume method). The SIMPLE algorithm of the commercial code is picked for the present study. The simulated results in the heat exchanger tube fitted with 30° inclined ring are offered in patterns of streamlines, temperature contour, and Nusselt number contour. From the preliminary result, it is found that the creation model of the heat exchanger tube fitted with 30° inclined ring has sufficient reliance to measure flow and heat transfer profiles. The installment of the 30° inclined ring in the heat exchanger tube leads to greater heat transfer ability and thermo-hydraulic performance because of the creation of the vortex flow and thermal boundary layer disturbance on the heat exchanger tube surface. The heat transfer ability in the heat exchanger tube fitted with 30° inclined ring is found to be around 1.00–10.56 times above the plain circular tube. In addition, the installation of the 30° inclined ring in the heat exchanger tube gives the maximum thermal enhancement factor around 3.18.
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Forced convective heat transfer and thermal efficiency assessment in square channel equipped with 10° wavy thin rib
(2020-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Forced convective heat transfer and thermo-hydraulic efficiency in the heat exchanger square channel (HESC) inserted with 10° wavy thin rib (WTR) are reported numerically. The effects of rib height, pitch distance and flow velocity on flow and heat transfer profiles are considered. The rib height to the channel height; e/H or H<inf>R</inf>, is varied in the range 0.05–0.30, while the rib pitch to the channel height; P/H or P<inf>R</inf>, is varied in the range 0.50–1.25. The air velocity in the HESC inserted with the WTR is considered in terms of Reynolds number. The Reynolds numbers (Re = 100–2000) for the present investigation is analyzed at the inlet condition. The finite volume method (commercial code) with SIMPLE algorithm is picked to solve the present problem. The numerical model of the HESC inserted with the WTR is validated for both grid independence and verification of the smooth HESC. The numerical results of the HESC inserted with the WTR are printed in terms of flow and heat transfer profiles. The values of Nusselt number, friction factor and thermal efficiency factor in the HESC inserted with the WTR are also plotted. As the numerical result, it is found that the WTR in the HESC can produce the vortex flow that the reason for the enhancements of heat transfer and efficiency. The increment of the heat transfer ability in the HESC is detected when increasing rib height and Reynolds number. In addition, the greatest thermal efficiency factor in the HESC inserted with the WTR is around 3.43 at H<inf>R</inf> = 0.20, P<inf>R</inf> = 1, and Re = 2000.
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LAMINAR FORCED CONVECTION AND PERFORMANCE EVALUATION IN A SQUARE DUCT HEAT EXCHANGER PLACED WITH WAVY THIN RIB
(2020-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Simulated examinations on convective heat transfer and flow topology in a square duct heat exchanger placed with wavy thin rib (WTR) are presented. The influences of WTR heights, pitch distances and flow directions on flow and heat transfer characteristics are investigated for the laminar flow regime at the inlet condition (Re = 100 – 2000). The finite volume method (SIMPLE algorithm) is picked to analyze the numerical problem. The numerical validations; grid independence and verification of the smooth duct, are presented. The simulated results of the heat exchanger duct placed with WTR are reported in terms of flow and heat transfer visualizations. The relations of the Nu/Nu0, f/f0 and TEF with Re and P/H in the heat exchanger square duct inserted with WTR are also plotted. The numerical result reveals that the heat transfer and friction loss increase when augmenting the Reynolds number and WTR height. The optimum pitch spacing ratio may give the highest heat transfer rate and thermal performance.
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Thermo-hydraulic performance improvement, heat transfer, and pressure loss in a channel with sinusoidal-wavy surface
(2019-09-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Thermal efficiency development in a square channel heat exchanger attached with sinusoidal wavy surface is presented numerically. The affectation of flow attack angles (α = 30°, 45°, and 60°), flow directions or sinusoidal wavy surface arrangements (V-apex directing downstream named “V-Downstream” and V-apex indicating upstream named “V-Upstream”), and amplitude ratios (blockage ratios = 0.10, 0.15, 0.20, and 0.25) for heat transfer and flow structure are examined for laminar flow regime (Re = 100–1000). The physical model for the present investigation is validated with the correlation data. The current problem is resolved with the finite volume approach (semi-implicit method for pressure-linked equations algorithm). The computational information is illustrated in forms of flow topology and heat transfer mechanism in the square channel heat exchanger. The understanding of flow topology and heat transfer mechanism in the square channel heat exchanger is important knowledge to develop the heat transfer coefficient in the heat exchanger. The present of the sinusoidal wavy surface in the square channel heat exchanger can expand the heat transfer coefficient greater than the plain channel in all examples (Nu/Nu<inf>0</inf> > 1). The maximal heat transfer rate is around 5.58 times above the plain square unit with the optimal performance around 1.98.
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Performance analysis and flow visualization in a round tube heat exchanger inserted with wavy V-ribs
(2017-09-01)
Jedsadaratanachai, Withada
;
Boonloi, Amnart
This article presents thermal performance analysis, flow visualization, and heat transfer characteristic in a round tube heat exchanger inserted with wavy V-rib. The novel design of the wavy V-rib not only allows mass production and simple installation in the heating system but also remains the thermal performance and the heat transfer rate as near as those of the V-baffle design. The numerical investigation with finite volume method is selected to study and describe the mechanisms in the test section. The effects of rib thickness, rib height, and flow direction are considered for the turbulent regime. The numerical results are reported in terms of flow structure and heat transfer behavior. The relationship of the Nusselt number, friction factor, and thermal enhancement factor with various parameters is also concluded. The numerical results reveal that the optimum thermal performance is detected for the wavy V-rib at b/D around 0.1-0.15, while the optimal t/D is around 0.15-0.20 when considered at the simplicity of the wavy V-rib production.

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