Experimental investigation of flow and heat transfer characteristics in single-tube liquid-solid fluidized bed heat exchangers

Resource recovery of CaO and SO2 from phosphogypsum: Autothermal potential evaluation of oxygen-enriched atmosphere and conventional air calcination processes.

Microchannel liquid cooling technology, characterized by high heat-transfer efficiency, represents an effective solution for thermal management in high heat-flux density electronic devices. Existing research has mainly focused on optimizing the structural design of microchannel heat sinks, while neglecting the specific effects of inlet manifold configurations on their heat transfer and flow performance. To obtain more systematic data on microchannel heat transfer performance and internal velocity distribution, this study designed microchannels with single-inlet and triple-inlet configurations. A microchannel cooling performance testing platform was established, and visualization experiments of the internal flow field in straight microchannels were conducted using a particle image velocimetry (PIV) system. The velocity distribution uniformity and heat transfer performance were compared between single-inlet and triple-inlet microchannels with varying channel spacings. The results show that under the same flow conditions, the triple-inlet splitter structure yields a more uniform flow distribution, a lower peak temperature for the heat source chip, and improved heat transfer performance, with its pressure drop reduced to 11.1-26.6% of that of the single-inlet configuration. Furthermore, smaller channel spacings yield improved heat-transfer efficiency in microchannels.

Hybrid nanofluids flow in a u-bend double-pipe heat exchanger: effectiveness and thermal performance evaluation

Abstract This study aims to experimentally investigate the influence of heat exchanger orientation and heat transfer fluid (HTF) injection direction on the thermal performance of a latent heat thermal energy storage (LHTES) system using a phase change material (PCM). A comparative analysis is conducted between horizontal and vertical double-pipe heat exchanger configurations, considering both top and bottom injection of the HTF. The experimental methodology involves systematic variations of inlet temperature and volumetric flow rate while monitoring temperature evolution, charging and discharging durations, heat transfer coefficients, and Nusselt numbers. The results demonstrate that the direction of HTF injection plays a critical role in governing heat transfer behavior. Top injection promotes faster charging by enabling the PCM to reach higher average temperatures, whereas bottom injection enhances convective heat transfer, yielding the highest Nusselt numbers and heat transfer coefficients, albeit with longer charging and discharging times. In the horizontal configuration, increasing the flow rate from 60 to 120 L h −1 reduces the charging time from 70 to 60 min, corresponding to an improvement of 14.2%. Discharge tests performed at inlet temperatures of 70 °C and 80 °C reveal performance reductions of 8.9% for the horizontal configuration, 43.3% for bottom injection, and 42.6% for top injection at a constant flow rate. Overall, the horizontal configuration exhibits the fastest thermal response during both charging and discharging processes, while bottom injection achieves the highest thermal efficiency. These findings highlight the importance of heat exchanger orientation and flow direction optimization for improving the performance of LHTES systems.

Artificial intelligence mapping of turbulence data of fluid flow in heat exchangers occupied with porous foam

Modeling and analysis of flow and heat transfer maldistribution in a supercritical CO2 hybrid mini-channel heat exchanger based on spatial thermal resistance networks

Numerical Investigation of Flow and Heat Transfer Characteristics in Hairpin Heat Exchanger

International audience

Abstract This study employed an orthogonal experimental design, coupled with range and variance analysis, to investigate the sensitivity of the flow and heat transfer performance in a microchannel heat exchanger to header structural parameters. The results show that the degree of influence on the flow and heat transfer performance follows the order: the diameter of the inlet and outlet tubes, the lateral distance between the inlet and outlet tubes, and the header width. Increasing the diameter of the inlet and outlet tubes significantly improves the uniformity of fluid distribution and heat transfer coefficient, thereby enhancing total heat exchange capacity while reducing pressure drop. In contrast, increasing the lateral distance between inlet and outlet tubes reduces fluid distribution non-uniformity but increases heat transfer non-uniformity. Variations in the header width have a relatively minor impact on both the flow and heat transfer performance and their distribution uniformity. In the design of microchannel heat exchangers, the header width should be maintained at a relatively small value.

The study focuses on the preparation of Cu–SiO2 hybrid nanofluids in a glycerol and water base at different volume loadings. Thermophysical properties of the nanoparticles are measured at 20–80°C and characterized using FESEM, EDX, and XRD. Thermal conductivity and viscosity are tested using a TPS-500S hot disk thermal constants analyzer and a Brookfield Viscometer. The study finds that temperature and concentration both increase thermal conductivity, while viscosity increases with concentration and falls as temperatures rise. The highest thermal conductivity enhancement is found with 1% concentration at 80°C, while viscosity is least at 0.2% concentration. Heat transfer experiments are conducted in a double tube heat exchanger, showing that 1% concentration increases overall and convective heat transfer coefficients by 26.3 and 49.4% over base liquid at 36°C.

BACKGROUND: The paper presents the design of a shell-and-tube recirculation gas cooler for marine diesel engines and analyzes its performance. The study is necessitated by the ever-stricter regulations on monitoring and reducing marine engine emissions. AIM: To improve the exhaust gas recirculation (EGR) system to reduce NOx emissions and increase the engine performance by improved cooler design. METHODS: We used Ansys Fluent software to simulate the flow and temperature distribution in the cooler to increase cooling efficiency and improve the system design. Process simulation showed that coolant flow rate and heat exchanger tube structure adjustment significantly improves cooling efficiency and reduces energy consumption. RESULTS: The study shows that at gas recirculation rates of 30% and 40%, the selected cooler design fully meets the recirculated gas cooling requirements and the minimum cooling temperature can be reduced to 133 ˚C. The analysis may be used in calculations to improve and increase the cooling efficiency of an existing cooler. CONCLUSION: The method used in the study may be applied to other marine diesel engines to improve fuel efficiency and reduce environmental impact.

Abstract A numerical study using ANSYS Fluent 18.1 software was conducted to examine the fluid flow and heat transfer characteristics in a cross-flow heat exchanger equipped with rectangular, hexagonal, and semi-elliptical finned tubes. Simulations were performed for Reynolds numbers ranging from 3422 to 11980. The results show that rectangular fins produce the highest heat transfer values with a high pressure drop. However, semi-elliptical fins offer superior thermal and hydraulic efficiency. At Re = 5990, the semi-elliptical configuration improves overall efficiency by 5.17% and reduces pressure drop by 47.86% compared to the rectangular fin design.

• Turbulence intensity depends on U-tube bend radius and flow rate. • Increased turbulence boosts heat transfer but also erosion risk. • Experimental PIV validated CFD for flow in curved heat exchanger pipes. • Turbulence stabilizes downstream within a distance of 7 pipe diameters. • Regression model links flow rate and bend radius to turbulence intensity. Efficient and durable operation of heat exchangers requires understanding the flow behavior at high Reynolds numbers, especially in curved pipe segments such as U-bends. The study is motivated by quantifying turbulence-related erosion and flow maldistribution in compact heat exchangers. It is hypothesized that turbulence intensity downstream of the bend significantly depends on the pipe curvature and flow rate. To verify this, experimental velocity field measurements using Particle Image Velocimetry and numerical simulations based on the Reynolds-averaged Navier–Stokes equations with the k–ε model were performed for various U-bend radii (0.009–0.039 m) and flow rates (0.05–0.30 m 3 /h). The results show that smaller bend radii produce up to 45 % higher turbulence kinetic energy, while the flow stabilizes within 7 pipe diameters downstream. The relative increase in turbulence was expressed as a function of curvature and flow rate using a linear regression model, with R 2 > 0.99 for experimental and >0.89 for numerical results. These findings support improved thermal–hydraulic design of tubular heat exchangers by linking geometry with both performance enhancement and erosion risk mitigation.

Experimental insights into synergistic and competitive interactions among flow, heat transfer, and catalytic conversion in cryogenic hydrogen plate-fin heat exchangers

Optimization of heat-exchanger manifolds can significantly improve the flow distribution inside their cores, improving the heat exchange and reducing flow obstruction. It also reduces the overall mass of the system and with it, the cost of additive manufacturing. However, during optimization, domains are typically modeled as 2D to minimize computing effort. Likewise, laminar flow is prescribed even when turbulence is expected in operation. The accuracy of such assumptions and their effect on optimized geometry is unclear. In this work, 2D topology optimization was first performed on an inlet manifold for both laminar and turbulent inlet boundary conditions. The resulting geometries were found to be starkly different, illustrating a difference in design concepts for different flow regimes. The laminar flow cases were then topology optimized with a 3D domain that modeled out-of-plane walls. This produced yet more different geometry, showing that these walls cannot be ignored. Experimental validation by testing stereolithography 3D prints proved that 3D optimization involves far more accurate flow modeling and the results are therefore likely to have better flow distribution.

Enhancement of Heat Transfer in a Counter Flow Heat Exchanger Utilizing Elastic Wall Effect

Control of turbulence through use of lattice meshes has been a main topic in fluid-dynamic literature since mid of last century. A specific class of lattice meshes, known as expanded metal meshes, EMS, has been proposed for baffles design in novel longitudinal flow heat exchanger technology for promotion of turbulence under limited pressure drops about two decades ago. Present investigation aims at developing a simple model for the design and optimization of suitable EMS geometry for its utilization as turbulence promoter in shell&tube heat exchangers for industrial applications. Novelty of approach relies on pressure drops based geometry design for improved functional product features.

Numerical study on fluid flow and heat transfer characteristics in spiral wound heat exchanger with helical rods

Experimental study of heat transfer performance in a novel stacked granule flow heat exchanger: Strengthening mechanism based on multi-parameter coupling