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A numerical study of a novel discrete X-V baffle for heat transfer enhancement in duct heat exchangers
(2026-09-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
This study proposes a novel vortex generator, referred to as a discrete X-V baffle (DXVB), for enhancing heat transfer (H-T) in a square cross-section tube heat exchanger. The DXVB is developed by integrating the design concepts of a V-baffle and a V-orifice. A numerical approach based on the finite volume method is employed to investigate the thermal–hydraulic characteristics under turbulent flow conditions, with Reynolds numbers ranging from 3000 to 16,000. The effects of DXVB thickness and installation clearance are systematically examined. In addition, both co-current flow (+x direction) and counter-current flow (−x direction) configurations are considered. The results are presented in terms of dimensionless parameters, along with detailed analyses of flow structures (FS), H-T characteristics, and the underlying physical mechanisms occurring within the heat exchanger system. The findings reveal that the incorporation of DXVB significantly enhances the H-T rate, achieving a maximum increase of up to 6.29 times compared to a plain tube without inserts. Furthermore, the thermal enhancement factor (TEF), representing the overall performance, reaches a maximum value of 1.32.
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Enhancing convective heat transfer coefficient in a circular heat exchanger tube mounted with modified V-orifice (MVO): CFD analysis and correlations
(2026-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
This study investigates the airflow dynamics and heat transfer (HT) profiles in a circular heat exchanger tube (CHET) mounted with a modified V-orifice (MVO) acting as a turbulator/vortex generator, which is a passive technique to enhance HT. A numerical modeling approach based on the finite volume method using a commercial software package was employed to provide detailed insights into the air flow profile, which is essential for the design of both the turbulator and the CHET system. The MVO is a turbulator derived from the orifice concept, an established engineering device, and has been adapted in combination with a V-shaped structure to effectively generate vortices and enhance HT. Key parameters expected to influence the flow and HT behavior were investigated. These include the ratio of the MVO thickness, b, to the CHET diameter, D (referred to as the blockage ratio, B-R), which was studied in the range of 0.05–0.30, and the ratio of the MVO spacing, P, to the CHET diameter (pitch ratio, P-R), which was considered at values of 1, 1.5, and 2. Attack angles of 30°, 45°, and 60° were examined for both + x and–x flow directions. The study covered turbulent flow conditions corresponding to Reynolds numbers in the range of 3,000–16000, representative of the operating conditions at the CHET inlet. The results indicate that MVO installation in the CHET acts as a flow obstruction, generating a pressure difference that induces vortex formation. These vortices play a key role in modifying the HT behavior, resulting in increased convective HT coefficients. The outcomes are summarized in forms of dimensionless variables. The highest observed HT enhancement reached 9.93 times that of the plain CHET, while the maximum thermal enhancement factor (TEF) was 1.92, obtained at an attack angle of 30°, P-R = 1, B-R = 0.25, in the +x fluid-flow direction at Re = 3,000.
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Numerical investigation of thermal profile and air-flow visualization in a tube heat exchanger with discrete X-V vortex inducers (DXVVI)
(2025-12-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
This study presents the implementation of discrete X-V vortex inducers (DXVVI) as a passive heat transfer enhancement technique in circular heat exchanger tubes. The DXVVI devices are introduced to improve the convective heat transfer coefficient, heat transfer rate, and thermal performance. Numerical simulations using a commercial CFD code were employed to investigate the flow structure and thermal behavior within the heat exchanger system. The DXVVI concept is developed based on a combination of the V-Orifice and V-shaped baffle, aiming to retain the thermal performance of the V-shaped baffle while maintaining the structural strength of the V-Orifice. The discrete configuration was selected to enhance turbulence levels and reduce pressure drop. Two DXVVI design groups, referred to as “GROUP 1” and “GROUP 2”, were proposed. Key parameters influencing the flow and thermal characteristics were investigated, including the pitch ratio (PRT), defined as the ratio of the longitudinal pitch or pitch distance (P) to the circular tube diameter (D), i.e., P/D, and the flow-blockage ratio (BKRT), defined as the ratio of the DXVVI thickness (b) to the circular tube diameter, i.e., b/D. The simulations were conducted under turbulent flow conditions with Reynolds numbers (Re) ranging from 3000 to 20,000, considering both co-flow (+x) and counter-flow (−x) directions. In GROUP 2, small gaps were introduced in various configurations to enhance turbulence intensity, increase the number of vortex cores, and further reduce pressure drop—leading to improved heat exchanger performance. The numerical model was validated using appropriate academic standards, confirming its reliability in predicting thermal and flow behaviors. The numerical results are performed in terms of fluid-flow structure (e.g., streamline plots in transverse planes and 3D flow visualizations) and thermal characteristics (e.g., fluid-temperature contours in cross-sectional planes and Nusselt number distributions on the tube surface). Performance evaluation was also carried out using dimensionless metrics, including the Nusselt number ratio (Nu/Nu₀), the friction factor ratio (f/f₀), and the thermal enhancement factor (TEF) under equal pumping power conditions. The best heat transfer rate augmentation was observed to be up to 8.07 times greater than the reference case (smooth tube). The highest TEF, equal to 3.14, was observed in GROUP 2 for configuration 5B5G5B with a pitch ratio (PRT) of 1.
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Numerical Study of Turbulent Forced Convection in a Square Duct with Discrete X-V Inducing Turbulators (DXVIT)
(2025-04-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
This research is an extension study that applies a vortex generator previously developed and tested under laminar flow conditions to investigate its performance under turbulent flow conditions, covering the operating range of various heat exchanger systems. This type of vortex generator is called the discrete X-V inducing turbulator (DXVIT), which is derived from the V-baffle, known for its high heat transfer enhancement efficiency, combined with the structure of an orifice that provides durability and stability when installed in heat exchanger systems. The DXVIT is installed to modify the primary flow structure and disrupt the thermal boundary layer (ThBL), resulting in an increase in the convective heat transfer coefficient. This study examines the effects of DXVIT size, installation spacing, flow direction, and DXVIT type on the heat transfer and flow behavior under turbulent flow conditions with Reynolds numbers ranging from 3000 to 16,000. The investigation is conducted using numerical simulation methods. The results are presented in terms of flow and heat transfer behavior, along with an analysis of thermal performance using dimensionless parameters. The findings indicate that the heat transfer rate increases up to 5.29 times, and the thermal performance factor reaches 2.65 under the same pumping power conditions.
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Turbulent forced convection in a square duct heat exchanger (SDHX) equipped with combined vortex turbulators (CVT): A numerical investigation
(2025-02-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
This research presents a numerical study on flow structures, heat transfer, and thermal performance evaluation in a square duct heat exchanger (SDHX) equipped with combined vortex turbulators (CVTs). The aim of installing CVTs is to create vortex flow, impinging flow, and disrupt the thermal boundary layer, thereby enhancing the convective heat transfer coefficient and increasing the heat transfer ability and SDHX performance. V-shaped ribs and rectangular winglets are selected as CVTs due to their effectiveness in enhancing heat transfer rates. The study investigates the effects of CVT height (the values of a/H and b/H range from 0.05 to 0.20.), flow direction (V-apex pointing downstream (V-Downstream) and V-apex pointing upstream (V-Upstream)), and CVT arrangement (in-line and staggered arrangements) on flow structure and heat transfer characteristics. A comparison between V-shaped ribs and rectangular winglets is presented in terms of CVT types (A and B). The study focuses on turbulent flow with Reynolds numbers ranging from 3000 to 20,000. The results demonstrate that the flow behavior aligns with the proposed hypotheses, leading to increased heat transfer rates, which are 1.24 to 7.71 times greater than those of the empty duct. For thermal performance evaluation, the highest thermal enhancement factor (TEF) value of 1.77 is observed with type A CVT, in a staggered arrangement, and with the V-Upstream flow direction, when considering a Reynolds number (Re) of 3000. Additionally, the results of the study are presented in the form of TEF contours and correlations to assist in the design of vortex turbulators for heat exchange systems.
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Numerical Investigation of Diffuser-Shaped Vortex Generators with Semi-Open Angles on Cylindrical Towers
(2025-01-01)
Sudsanguan, Anan
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Boonloi, Amnart
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Jedsadaratanachai, Withada
This study presents a numerical investigation into the flow configurations and pressure distribution of cylindrical towers equipped with various vortex generators. The primary objective is to reduce the energy consumption of ventilation in these towers. Different diffuser-shaped vortex generators with semi-open angles are compared to determine the optimal angle for generating an upward suction draft. The study also examines the effects of air velocity and vortex generator size on flow configuration. The finite element method, implemented through commercial software, is employed to solve the main problem. The numerical results reveal that the suction draft speed within the tower is directly proportional to the crosswind speed. The diffuser-shaped vortex generator with a height equivalent to 2D provides the most effective ventilation. Furthermore, a semi-open angle of 8° proves to be the most suitable for cylindrical towers, with increasing semi-open angles resulting in enhanced updraft wind speeds.
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Numerical Assessments on Laminar Airflow, Thermal Characteristic, and Performance Improvement in a Round Tube Equipped With Combined Vortex Generators
(2025-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
A round tube heat exchanger (RTHE) with combined vortex generators (CVGs) is subjected to numerical assessments of its airflows and thermal characteristics. The CVGs are V-shaped ribs and rectangular winglets. The effects of CVG arrangement (A-1, A-2, and B), blockage ratio (b<inf>1</inf>/H and b<inf>2</inf>/D), and airflow direction (+x, −x) on airflow and thermal behavior are considered. To solve the numerical problem, a commercial program’s finite volume technique is chosen. Presenting streamlines, fluid temperature distributions, and local Nusselt number contours (on the tube wall) are the numerical findings obtained in the RTHE fitted with the CVG. The study presents the performance analysis of RTHE using dimensionless variables, including the thermal enhancement factor (or thermal performance factor), averaged friction factor, and averaged Nusselt number. The numerical results indicate that the general flow configuration in the RTHE is dramatically altered by the CVG. The mixing quality of the fluid seems to be enhanced. The vortex flows are found through the RTHE. As a result of the vortex flows impinging on the RTHE wall, the thermal boundary layer (T-BL) over the heat transfer surfaces changes. Enhancing the convective heat transfer coefficient, heat transfer ability, and thermal performance in the RTHE is mostly because of the reduction of the T-BL thickness. When compared to a smooth round tube, the maximum enhanced heat transfer of the RTHE fitted with the CVG is 13.83 times greater. Furthermore, at Re = 2000, type B, b<inf>1</inf>/D = 0.15, b<inf>2</inf>/D = 0.05, and V-Upstream scenario, the optimal TEF is 3.81.
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Investigations of Air-Flow Configuration, Heat Transfer Behavior and Thermal Performance in Heat Exchangers with XVB-Type Turbulence Generators Under Turbulent Flow Conditions
(2025-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
This study employs numerical modeling using the finite volume method to analyze airflow and thermal structures when vortex flow (VTF) generators are installed in heat exchanger square ducts (HX-SD). The VTF generator used in this study is the X-V baffle (XVB), which is designed to enhance heat transfer rates. The XVB is an evolution of the V-baffle, a type of VTF generator known for its efficiency in improving heat transfer. It features an X-shaped structure (considered in the cross-sectional (CS) plane, y-z plane) to further optimize the design. The present research investigates the effects of XVB thickness, represented by the thickness ratio (b) to the HX-SD height (H) or hydraulic diameter (Dh) (b/H), with B-R values ranging from 0.05 to 0.20. Additionally, three XVB configurations (Types A, B, and C) are examined, along with two airflow directions: AFD-VD (airflow direction – V-Downstream) and AFD-VU (airflow direction – V-Upstream). The investigation focuses on turbulent flow conditions, analyzing air velocity within a Reynolds number range of Re = 3,000 to 16,000. The results indicate that VTF is generated throughout the HX-SD due to the pressure difference caused by flow obstruction from the XVB in all cases examined. By enhancing air mixing and disrupting the thermal boundary layer (Th-BL), the induced VTF significantly increases the heat transfer rate. The maximum observed increase in heat transfer was 7.95 times higher than that of a smooth, empty duct.
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Air Flow, Thermal Profile, and Thermohydraulic Performance Assessment in a Square Duct Heat Exchanger With Combined Vortex Generators: CFD Analysis
(2025-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
Numerical simulations of laminar air flow, heat transfer behavior (thermal structure), and thermal performance evaluation in a square duct with combined vortex generators (CVGs) are presented. The CVG configuration consists of a combination of rectangular winglets and V-shaped baffles. The thermal performance of two types of CVGs is compared. Type I includes a set of rectangular winglets placed on the upper and lower walls, with a V-shaped baffle in the middle. Type II features V-shaped baffles placed on the upper and lower walls, with a rectangular winglet in the middle. The purpose of the CVGs is to induce vortex flows, impinging flows, swirling flows, and to disturb the viscous sublayer over the duct surfaces, thereby improving the convective heat transfer coefficient and thermal efficiency. Based on the finite volume method, numerical modeling is used to analyze the effects of the position and height of CVGs on fluid and thermal characteristics for Reynolds numbers ranging from 100 to 2000. Thermal assessments of the CVGs are presented in terms of the Nusselt number ratio, friction factor ratio, and thermal enhancement factor. It is found that Type II outperforms Type I, showing the best Nusselt number ratio of 19.36 when b<inf>1</inf>/H = b<inf>2</inf>/H = 0.20 in the positive x-direction. However, Type I exhibits the greatest thermal enhancement factor, 4.39, which is higher than Type II when the blockage ratios are b<inf>1</inf> = 0.15H and b<inf>2</inf> = 0.05H in the +x FFD.
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Turbulent Airflow and Thermal Analysis in a Circular Tube Heat Exchanger Fitted With Turbulence-Inducing Vortex Generators (X-V Baffles)
(2025-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
The research presents an investigation into airflow configuration, thermal behavior, and convective heat transfer enhancement in a circular heat exchanger tube fitted with turbulence generators. These turbulence generators, referred to in this study as X-V baffles (XVBs), were developed to generate swirling flow within the heat exchanger tube, which is directly related to the enhancement of heat transfer rates and the overall performance of the heat exchanger. Additionally, the XVBs were designed with consideration for practical application and ease of maintenance in real-world industrial settings. The study examines the variables influencing airflow topology and thermal structure, including the blockage ratio (g/D = 0.05–0.20), pitch ratio (P/D = 1–2), flow direction (FD-VD and FD-VU), and types of turbulence generators (Type S and Type T XVBs). The research was conducted within the turbulent flow regime, with Reynolds numbers ranging from 3000 to 12,000 (Re = 3000–12000). The results are presented in terms of observed flow behavior within the test tube, such as cross-flow streamlines, streamwise flow streamlines, Nusselt number distribution, and fluid temperature distribution. The findings clearly show the formation of swirling flow in the heat exchanger tube when XVBs are installed. An increase in the blockage ratio and a decrease in the pitch ratio lead to a more intense swirling flow. The intensity of this swirling flow is directly correlated with the degree of disturbance in the thermal boundary layer (TH-BL). The maximum enhancements in Nusselt number and friction factor due to XVB installation are 7.24 and 58.01 times greater, respectively, compared to a smooth tube without XVBs. The maximum thermal enhancement factor (TEF) achieved is 2.27, obtained from the case with the Type T XVB at a blockage ratio of g/D = 0.05, a pitch ratio of P/D = 1, and a flow direction in the FD-VD configuration.

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