Aug 2026· Machines· Vol 14, pp. 921· 0 citations· 41 references
Abstract
Pressure losses in heating, ventilation, and air-conditioning (HVAC) duct elbows significantly increase fan power requirements and reduce overall system efficiency. This study presents a comprehensive computational fluid dynamics (CFD) investigation aimed at identifying effective strategies for reducing pressure losses in 90° HVAC duct elbows. The numerical methodology was first validated against published experimental measurements, demonstrating excellent agreement and providing confidence in the predictive capability of the CFD model. The validated model was then employed to evaluate the influence of duct geometry, inlet velocity, guide vane configuration, inter-vane spacing, perforated guide vanes, and duct material roughness on aerodynamic performance using the SST k–ω turbulence model. The results show that round elbows reduce pressure losses by approximately 50% compared with hydraulically equivalent rectangular elbows, highlighting the strong influence of duct geometry on flow separation. Among the flow-control strategies investigated, curved guide vanes produced the greatest improvement, with an optimized three-vane arrangement and a non-dimensional spacing of s/Dh≈0.15 (corresponding to 150 mm for the specific geometry tested) reducing pressure losses by approximately 31% relative to the baseline elbow without guide vanes. In contrast, the investigated perforated guide vane provided only marginal improvement, indicating that its geometry requires further optimization to minimize blockage and mixing losses. The material roughness study showed that smooth, rigid duct materials produced only minor differences in pressure loss, whereas flexible ducts generated noticeably higher losses because of their increased surface roughness. These findings demonstrate that optimizing elbow geometry and guide vane design is considerably more effective than modifying duct material or using the investigated perforated vane configuration. The study provides practical design recommendations for improving the aerodynamic performance and energy efficiency of HVAC duct systems.
Despite the widespread application of Computational Fluid Dynamics (CFD) in vehicle aerodynamic analysis, limited studies have focused on high-performance sports cars under varying operating speeds. This study investigates the aerodynamic characteristics of the Audi R8 V10 using three-dimensional CFD simulations performed in SOLIDWORKS Flow Simulation. The objective is to evaluate the influence of vehicle speed on aerodynamic drag and lift forces affecting vehicle stability. Simulations were conducted under steady-state external flow conditions at vehicle speeds of 20, 40, 60, 80, and 100 km/h using standard atmospheric properties. The convergence criterion was monitored until all engineering goals reached 100% convergence, ensuring numerical stability and solution reliability. The simulation results indicate that increasing vehicle speed significantly increases both drag and lift forces due to higher aerodynamic loading on the vehicle body. Pressure contour and airflow streamline analyses further reveal the formation of high-pressure regions at the vehicle front and flow separation behind the rear section, which contribute to aerodynamic resistance. The findings demonstrate that CFD provides an effective approach for evaluating aerodynamic performance and can support the optimization of aerodynamic devices, such as spoilers and diffusers, to improve vehicle stability and energy efficiency at higher operating speeds.
Andreas Lumban Gaol, Margono Sugeng· International Journal of Ind...· 0 citations
Aerodynamic drag significantly influences vehicle performance and fuel efficiency, making its reduction a key focus in automotive design. This study examines the drag reduction of the simplified Ahmed body model by integrating diffusers at 8° and 10° angles. Using Computational Fluid Dynamics (CFD) simulations, airflow analysis was conducted on Ahmed bodies with 25° and 30° slant angles, both in baseline and modified configurations. The results show that diffuser-equipped models achieved a notable reduction in drag coefficient compared to the original design and previous literature. This improvement is primarily due to minimized turbulence in the wake region, as the diffuser slows airflow and enhances pressure recovery, thereby lowering drag. Both 25° and 30° slant configurations demonstrated substantial aerodynamic benefits with diffuser integration, with greater improvements observed at higher slant angles. Overall, the study highlights the effectiveness of diffusers in enhancing aerodynamic efficiency, offering valuable insights for vehicle design aimed at improving fuel economy, performance, and sustainability.
This research presents a detailed computational assessment of a shell-and-tube heat exchanger equipped with helical baffles, emphasizing the
influence of baffle pitch on the system’s overall thermal and hydraulic behavior. The primary aim was to enhance heat transfer capability while
limiting pressure losses, which is an essential requirement for industrial sectors such as energy production, petrochemicals, refrigeration, and
HVAC (Heating, Ventilation, and Air Conditioning) applications. The heat exchanger model was constructed in CATIA V5, and CFD (Computational
Fluid Dynamics) simulations were performed in ANSYS Fluent 15.0 to analyze the impact of different baffle pitches (ranging from
26 to 50 mm) on shell-side performance parameters: pressure drop, temperature difference, and total heat transfer rate over a mass flow range
between 0.1571 and 0.6284 kg/s. The computational results found a 38-mm baffle pitch as the most efficient configuration, yielding a maximum
heat transfer rate of 14.9 kW and a temperature reduction of 8.4 °C, with a moderate pressure penalty. Visualization of the flow field confirmed
the formation of stable swirling and crossflow zones that promote effective mixing without introducing excessive resistance. The study delivers
a systematic CFD-based analysis covering a broad range of operating conditions and offers practical guidelines for perfecting industrial heat
exchanger designs. The novelty of this work lies in its quantitative evaluation strategy, which decides the best configuration through balanced
consideration of both thermal enhancement and fluid dynamic efficiency. In addition to conventional thermal and hydraulic parameters, the
study introduces a thermal–hydraulic performance metric based on the heat transfer rate per unit pressure drop(Q/ΔP). This index provides
an integrated measure of heat transfer effectiveness compared to pumping power. Analysis of this performance index further confirms that the
38 mm pitch delivers the highest thermal–hydraulic efficiency, confirming it as the best configuration across all tested operating conditions.
D. M. Yadav, M. Basha, Dr. B. Omprakash et al.· Journal of Thermal Engineeri...· 0 citations
Unlike many previous high-speed train Heating, Ventilation, and Air Conditioning (HVAC) studies that combined numerical and experimental analyses within the cabin, this study evaluates the supply duct independently, offering a more targeted assessment of internal duct airflow and thermal performance. The research comprised two numerical stages and an experimental validation. The first stage evaluated four ducting geometry variations and identified the ducting system arrangement of 20 supply diffusers with a 45° air grille blocking angle as optimal for the Kereta Cepat Merah Putih (KCMP) case, keeping air velocity within the thermal comfort range for all simulated passengers. This geometry was then manufactured as a full-scale prototype and assessed in a second numerical stage against experimental measurements. The air velocity yielded a mean absolute deviation (MAD) of 0.57 m/s and a relative mean deviation (RMD) of 34.22%, while the air temperature showed an MAD of 2.13 °C and an RMD of 8.16% at duct planes, and 0.80 °C and 3.06% at duct outlets. These results demonstrate that the proposed approach of testing the supply duct independently of the cabin is able to capture the general internal duct airflow trends, even though, particularly for the temperature parameters, a large temperature discrepancy occurs at downstream locations traced to three factors: uncontrolled ambient thermal conditions in a large-scale indoor facility, simplified thermal boundary conditions in the simulation, and additional uncertainty from the non-standardised temperature measurement method. Nonetheless, it offers a promising preliminary reference for HVAC system development, prior to integrated carbody testing, although further method refinements are still required to strengthen the reliability of this approach.
F. Fauzun, Muhammad Arkan Febian Hermada, Fakhreza Areli et al.· Engineer· 0 citations
In air-assisted orchard spraying, airflow characteristics strongly determine spray performance. This study designed a tower-shaped fan for grape canopies and investigated its aerodynamic behaviour. A three-dimensional computational fluid dynamics (CFD) model of the internal flow field was established to quantify the effects of shroud taper, upper and lower guide-vane angles, inlet diameter, and inlet position on outlet air-velocity uniformity. Single-factor simulations confirmed that all selected structural parameters significantly affect the outlet air velocity’s coefficient of variation (CV). Based on these results, central composite design was applied for multi-parameter optimisation. A second-order regression model was developed to describe the relationship between guide-vane angles, shroud taper, inlet position, inlet diameter, and air-velocity CV response. Analysis of variance showed that the influence of the factors decreased in the following order: guide-vane angle > inlet position > inlet diameter > shroud taper. Numerical optimisation identified the optimal configuration as a guide-vane angle of 118.37°, shroud taper of 23.84°, inlet position of 29.35 mm, and inlet diameter of 493.92 mm. Under these conditions, the predicted air-velocity CV decreased to 12.07%. A field validation experiment was conducted using representative measurement points selected from the simulated velocity distribution. The maximum relative error between measured and simulated values was below 6%, indicating strong agreement. These results confirm the reliability of the CFD model and demonstrate its effectiveness for structural optimisation of orchard air-assisted spraying equipment.
P. Zhan, Z. Y. Sun, Q. Meng et al.· Journal of Applied Fluid Mec...· 0 citations
Electric ducted fans (EDFs) have emerged as promising propulsion systems due to their compact design, high thrust density, and enhanced operational safety. Accurate prediction of aerodynamic thrust is essential for EDF design and performance evaluation; however, existing numerical studies have not yet provided a systematic comparison of the thrust-prediction capability of different k-ω-based turbulence models in micro-EDF applications. In this study, a dedicated thrust-measurement platform was developed for a 120 mm EDF, and experimental thrust data were obtained under three representative hover operating conditions. Based on these measurements, six turbulence models, including SST, SKω, BSL, GEKO, EARSM, and SST-γ(alg.), were evaluated using three-dimensional CFD simulations. The numerical model was assessed through thrust validation, centerline velocity comparison, power-consistency analysis, grid independence verification, and qualitative flow-field interpretation. A two-factor full-factorial analysis was further conducted to quantify the effects of rotational speed and turbulence model on prediction accuracy and computational cost. The results show that the turbulence model has a stronger influence on the normalized thrust-prediction error than the rotational speed factor over the investigated operating range. The SST-γ(alg.) model achieves the highest thrust-prediction accuracy, with an average relative deviation of 0.47%, but requires the highest computational cost. In comparison, the SST model provides a favorable balance between accuracy and efficiency, with an average relative deviation of 1.79% and an average computation time of 184.33 min, approximately 33% lower than that of the SST-γ(alg.) model. The centerline velocity and power-consistency results further support the comparative model assessment. Overall, this study provides an experimentally validated comparative reference for turbulence model selection in simulations of similar 120 mm EDF under hover conditions. Considering both prediction accuracy and computational efficiency, the SST model can serve as a practical turbulence model choice for engineering parameter optimization of similar micro-EDF configurations.k−ω
Shenglun Zhang, Chuanping Tang, Hamza Blala et al.· Aerospace· 0 citations
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