Advanced nanofluids, also known as ternary nanofluids, impressed engineers and scientists with their unique molecular structure and enhanced heat transfer capabilities. These might help in aerodynamics, biomedical engineering, aeronautical science, and electrical gadgets. These may be utilised as coolants in a variety of industrial applications, particularly in the electrical and chemical sectors. The Casson-Maxwell fluid model is used to explain a unique combination of nanoparticles, copper, silver, gold, and engine oil in a base fluid that has good thermodynamic characteristics for improving thermal and electromagnetic effects. Engine oil is used as the foundation fluid running through a Riga plate. The controlling PDEs are converted to ODEs. The bvp4c approach is used to determine the solution in order to the ordinary differential equation. This model employs a revolutionary calculating numbers intelligently technology, a perceptron with many layers that uses feed-forward and back-propagation, as well as a technique for artificial neural networks based on the Levenberg-Marquardt formula. The data is collected for neurological network confirmation, examination, and training. The one that models effectiveness and the average square error are derived using artificial neural networks.

ABSTRACT The artificial ground freezing (AGF) method is frequently affected by groundwater seepage. Due to the combined effects of convective heat transfer by water flow and conductive heat transfer from the cold source, the artificial freezing curtain in a seepage field exhibits significant asymmetry. Most existing studies focus on brine freezing, whereas the ultra‐low temperature properties of liquid nitrogen make it suitable for freezing projects in high‐seepage environments. This study investigates the temperature field of three‐pipe liquid nitrogen freezing. An equivalent partitioning and segmentation method is employed to determine the shape of the freezing curtain, an analytical solution for the steady‐state temperature field of a three‐pipe liquid nitrogen freezing curtain under high seepage‐flow is derived. Through model tests and numerical simulations, the evolution of the three‐pipe liquid nitrogen freezing temperature field under varying seepage conditions is analyzed, and the validity of the formula is verified. The results indicate that the calculated freezing temperature aligns well with both experimental and numerical results, confirming the validity of the analytical solution through model testing. A high‐flow environment enhances heat transfer efficiency at the solid surface. As the flow rate increases, heat transfer efficiency improves, and the asymmetry of the freezing curtain becomes more pronounced. In multi‐pipe freezing, the “adjacent pipe effect” occurs. When adjacent freezing fronts contract to the critical threshold ( L c ), the freezing front expands more rapidly, shortening the intersection time of the freezing curtain. These findings provide valuable insights for designing liquid nitrogen artificial freezing systems in high seepage‐flow.

ABSTRACT This review presents a comprehensive assessment of active strategies for enhancing pool boiling heat transfer, with a focus on techniques that do not rely solely on the boiling surface modification. It examines a broad range of methodologies including fluid additives, external fields, mechanical interventions, and thermal‐geometric tuning that influence fluid flow guidance, bubble dynamics, and phase‐change behavior. These approaches aim to mitigate the incipient boiling hysteresis, increase the heat transfer coefficient (HTC), and improve the critical heat flux (CHF), particularly when employing dielectric coolants with inherently poor thermophysical properties. The present work also highlights the limited availability of robust data sets for each enhancement technique, which hampers the development of predictive models and design tools for advanced thermal management systems. The main implementation variables such as fluid properties, boiling surface size and orientation, enhancement geometry and scale, and operating pressure, among others, are often underreported or inconsistently characterized in the literature. This gap restricts the applicability of existing findings to the design of advanced cooling solutions for temperature‐sensitive electronic and power devices. Furthermore, this review addresses practical considerations including thermal performance, manufacturability, reliability, and durability over time. Where available, these factors are critically evaluated, and current challenges are outlined. The paper concludes with recommendations for future research to advance the understanding and integration of non‐surface‐based boiling enhancement techniques in modern cooling technologies.

The continuous advancement of automotive technology has intensified the demand for innovative materials that improve vehicle performance, energy efficiency, and sustainability. Nanofluids colloidal suspensions of nanoparticles within conventional base fluids have gained considerable attention due to their remarkable thermal and tribological properties. This review examines the current progress in nanofluid research, emphasizing their potential to enhance heat transfer, thermal management, and fuel economy in automotive systems. Nanofluids containing nanoparticles such as Al₂O₃, CuO, and carbon-based materials dispersed in base fluids like water or ethylene glycol have demonstrated superior thermal conductivity, enabling more compact and efficient heat exchangers, radiators, cooling systems, and engine lubricants. The review further explores their tribological advantages in minimizing friction and wear, as well as their contribution to improved combustion efficiency and reduced emissions in fuel systems. Despite these promising outcomes, challenges remain regarding nanoparticle dispersion stability, cost, and long-term performance. Economic factors, including raw material costs, synthesis requirements, and lifecycle considerations, also influence their practical adoption. Future research should focus on optimizing synthesis and stabilization techniques, assessing environmental implications, and developing hybrid nanofluids to maximize efficiency across diverse automotive applications. Overall, this review highlights the transformative potential of nanofluids in advancing automotive technologies while underscoring the need for continued research to address existing limitations and enable practical implementation.

The Microreactor Applications Research Validation and Evaluation (MARVEL) microreactor utilizes natural circulation as a core cooling mechanism and liquid metal as a primary coolant. Moreover, the reactor core has a pitch-to-diameter ratio of 1.054, which is considered a tight lattice configuration. Numerous studies have widely reported that Reynolds-averaged Navier-Stokes (RANS) turbulence models inaccurately predict heat transfer in liquid metals and fail to capture flow pulsations that can occur within tight lattices, leading to further inaccuracies in simulation results. Therefore, evaluating the accuracy of RANS turbulence models in the thermal-hydraulic analysis of the MARVEL microreactor core is crucial for assessing reactor safety. In this study, a large eddy simulation (LES) of the MARVEL microreactor core subchannel was conducted and compared with a RANS simulation to evaluate the accuracies and conservatism of the RANS model. In comparison with the RANS model, LES captures flow pulsations in a tight lattice that enhance heat transfer, whereas the RANS model underpredicts heat transfer in liquid metal flow. As a result, the RANS model predicts a higher peak cladding temperature than LES. However, owing to the high thermal conductivity of the liquid metal, the discrepancy between the two approaches is limited. These results indicate that the steady-state RANS model is adequate for the thermal analysis of the liquid metal–cooled MARVEL microreactor core and can provide conservative, yet not excessively overpredicted, results for safety assessment.

Ice slurry offers a promising solution for enhancing energy efficiency and environmental sustainability in industrial refrigeration and thermal energy storage applications. This review critically examines the effects of additives and production methods on the thermo-physical properties of ice slurry, focusing on viscosity and heat transfer performance. Additives such as ethylene glycol (6.5–10.3%), sodium chloride (up to 9%), and propylene glycol (5–24%) significantly enhance heat transfer coefficients by up to 33%, while alumina-based nanofluids (0.2 wt%) increase thermal conductivity by as much as 67%. Optimal ice packing factors (10–25%) and advanced production techniques, including direct contact and fluidized bed methods, improve energy efficiency, scalability, and operational reliability while mitigating issues such as particle agglomeration and viscosity rise. The study emphasizes rigorous methodological transparency with explicit equation definitions, controlled variables, and standardized measurement units (e.g., W/m²K for heat transfer, kg/m·s for viscosity). These findings provide valuable insights to guide the development of robust, high-performance ice slurry systems for large-scale cooling and energy storage applications.

Interaction between inverted flags: Application in heat transfer enhancement

Subcooled flow boiling in microchannels: Heat transfer enhancement via topology optimization and transient characteristics of microbubble emission

Influence of local perforations on heat transfer enhancement in inclined rib turbulators

This study numerically investigated the suppression mechanism of heat transfer deterioration of supercritical carbon dioxide (CO2) in heated vertical channels with an internal protruded teardrop dimple (IPTD). The effects of IPTD structure parameters and management on flow field, vortex structure, buoyancy effect, thermal acceleration, heat transfer, pressure drop, and performance evaluation criterion (PEC) were analyzed. The results revealed that the complicated vortex reformation induced by IPTD could effectively suppress the heat transfer deterioration witnessed by peak wall temperature reduction and well-distributed as well as heat transfer coefficient improvement. It was indicative that the internal protrusion in teardrop dimple without additional heat surface could mitigate the formation of large primary-recirculation flow in the dimple cavity and generate the small secondary-recirculation flow surrounding the protrusion, shifting the flow separation and reattachment, weakening the flow impingement, while reducing the form drag and friction drag, which contributed to heat transfer enhancement and less pressure drop penalty, consequently PEC improvement. In addition, dimple depth increased, neighbor dimple space decreased, circumferential dimple number increased, and disordered arrangement could further boost the heat transfer performance by promoting vortical motion, flow pattern transition, and intensified flow mixing.

Heat transfer enhancement in a microchannel via passive vortex generators combining with cylinder and symmetrically clamped elastic flaps

This study proposes a novel configuration of inclined dimples and presents experimental and numerical investigations of its thermal-hydraulic performance and economic viability. Previous research has primarily focused on tube-side enhancements, with experimental studies restricted to the laminar flow. The work explores inclined dimple configurations in an annular flow heat exchanger under a turbulent flow regime, incorporating thermal and economic evaluation along with design optimization. The purpose is to enhance heat transfer in heat exchangers used in various applications, such as thermal power systems, refrigeration and air conditioning, and food processing. The dimple inclination angle was varied from 0° to 75°, while other geometric parameters such as pitch, height, and circumferential columns, were kept constant. Distilled water (DW) was used as the working fluid, with Reynolds numbers ranging from 8000 to 16000. The results demonstrate that the dimple inclination angle modifies flow behaviour and influences the heat transfer performance. Compared to a smooth rod, the dimpled configurations enhanced heat transfer by a factor of 1.16–2.32, while increasing the friction factor by 1.33–3.13 times. The 45° inclined dimple configuration yielded the best thermal and economic performance, with performance evaluation criteria (PEC) values ranging from 1.48 to 1.77 and an estimated cost reduction of approximately 2.01 %. These findings provide valuable insights for optimizing heat exchangers to enhance heat transfer. The proposed design opens opportunities for compact and micro-level applications and offers significant potential for use with advanced working fluids, such as nanofluids, for efficient thermal systems.

Abstract We perform Direct Numerical Simulations (DNS) of turbulent channel flows with riblets in the drag-increasing regime. The objective is to investigate whether sufficiently large riblets diverge from the typical k -roughness regime and to evaluate whether some geometries, compared to a smooth channel, enhance heat transfer more than momentum transfer. To obtain different riblets viscous sizes, we vary the riblet size in outer units and adjust the Reynolds number. The results for friction are consistent with experimental findings from von Deyn et al. [17] for the same trapezoidal riblets geometry and indicate that these geometries deviate from the k -roughness regime. Furthermore, all tested geometries can improve the Reynolds analogy factor relative to a smooth channel by ≈ 1 − 2%.

Cosine-Shaped Stenotic Arteries Optimization of CPHNF Flow for Performance Enhancement in Unblocking Using Taguchi and Response Surface Methodologies

Numerical investigation of heat transfer and flow characteristics in eccentrically twisted oval tubes

Membrane filtration is a widely applied technology for water and wastewater treatment and for separation and purification in e.g. food and pharmaceutical industry. However, the applicability is severely limited by fouling. Several methods have been proposed to monitor membrane fouling, yet none have proven effective for full-scale implementation. The 3ω sensing is introduced as a novel approach for monitoring membrane fouling and shows promising potential to scale for in situ fouling monitoring. Promising results have been obtained for measuring filter-cake build up and compression (fouling) in dead-end filtration. In the current study, 3ω sensing is investigated for monitoring fouling in crossflow filtration to simultaneously measure how heat convection from the surface of the membrane depends on crossflow and formation of organic and inorganic fouling. A 3ω sensor was integrated onto the surface of a microfiltration membrane, and crossflow filtrations of kaolin and E. coli suspensions were conducted. It was observed that application of crossflow leads to a reduction of 3ω signal as it enhances heat transfer from the sensor. Measurements of 3ω signals at stagnant conditions (no crossflow) showed lower signals for membranes with inorganic fouling (thermally conducting) compared to a clean membrane, while measurements of a membrane fouled with E. coli shows a signal similar to that of a clean membrane due to the similarity in thermal conductivity between the feed and the fouling layer. Hence, the E. coli fouling layer could not be sensed in stagnant conditions. However, measurements in crossflow mode showed increasing 3ω signals by the formation of both kaolin and E. coli fouling layers. This happens because the fouling layer acts as a protective barrier against heat convection from the 3ω sensor, initially increasing the 3ω signal, regardless of the thermal conductivity. This phenomenon is coined shielding and has the notable consequence of increasing resolution of 3ω sensing for a foulant with thermal properties similar to those of water. This makes 3ω sensing an effective technique for detecting membrane fouling, with the potential to characterize both the type and thickness of the fouling layer with high resolution in crossflow filtration. These findings pave the way for advanced fouling diagnostics, predictive maintenance, and optimized cleaning strategies, offering substantial benefits for full-scale membrane operations in water and wastewater treatment, food, and pharmaceutical industries.

Giant enhancement of near-field radiative heat transfer enabled by a finite-size waveguide

Abstract Control and enhancement of convective heat-transfer in wall-bounded turbulent flows, particularly in pipe flows, is crucial for many industrial applications. A common strategy to enhance heat-transfer is introducing controlled perturbations, such as Jets In Cross-Flow (JICF). Studies have shown that pulsed jets, actuated at specific frequencies and duty cycles, outperform steady jets. However, these findings are limited to a narrow range of Reynolds number, and studies at higher, industrially-relevant values are missing. This work extends the one of Castellanos et al. to higher Reynolds numbers, investigating the scaling of the optimal frequency. Experiments are conducted in a high-Reynolds number facility, namely the Long Pipe at the CICLoPE laboratory. Results show a peak heat-transfer enhancement at 150 Hz, which corresponds to a Strouhal number St = 6.3. At 75% duty cycle and 150 Hz, the pulsed jet outperforms steady-jet actuation, demonstrating enhanced heat-transfer with reduced mass-flow input. Further investigations will assess whether this optimal frequency scales with turbulence parameters as a function of Reynolds number.

Jet impingement enhances heat transfer and is characterized by the complex flow patterns formed when a jet impacts a plate aligned normal to it. While traditional round jet impingement has been extensively studied to comprehend flow and associated heat transfer, there is still room for research when it comes to the investigation of flow structures in swirl jet impingement. This paper focuses on the flow topology of swirl jets generated by a 45° axial vane swirler, impinging on a flat plate studied at dimensionless jet-plate distances (H/D = 1–4) and Reynolds numbers (Re = 16 600 and 23 000). The flow structures, the mean velocity components, and the turbulence characteristics using two-dimensional particle image velocimetry (PIV) experiments at the front (r-z) and top (r-θ) planes of impingement are presented. Furthermore, results from the three-dimensional numerical simulations are presented to support the results in studying impingement cases where the PIV study had experimental limitations. The effect of impingement distance or jet-plate distance (H/D) on the mean flow properties and turbulence parameters is discussed. A proper orthogonal decomposition analysis has been performed to understand the dominant coherent structures at different cases of impingement distance (H/D). We show that the turbulence parameters are more pronounced at smaller jet-plate distances (H/D ≤ 2), which could explain the enhancement of heat transfer with these jets at smaller H/D.

Dimples on a tube surface can cause flow separation and generate secondary flows over the upper half of the dimples. The secondary flows disrupt the velocity and thermal boundary layers, which can enhance heat transfer rates. This work makes several contributions: it numerically investigates the effects of twisting and dimpling a straight smooth circular tube (SSCT) on hydraulic and thermal performance, examines the influence of different dimple geometries on SDCTs and TDOTs, and compares in-line and helical dimple arrangements in SDCTs regarding their thermo-hydraulic characteristics. Therefore, this study aims to examine and compare the hydraulic and thermal performance of SDCTs and TDOTs with three dimple shapes: spherical, elliptical, and teardrop. For SDCTs, spherical and elliptical dimples are implemented in both helical and in-line configurations, while for TDOTs, spherical, elliptical, and teardrop-shaped dimples are employed in an in-line configuration. The study considers Reynolds numbers (Re) from 5,000 to 25,000 at a fixed Prandtl number of 1.7, using the performance evaluation factor (PEF) to compare the thermo-hydraulic performance of various cases with that of an SSCT. According to the simulations, the SDCT with spherical dimples in a helical pattern enhances the convective heat transfer coefficient by as much as 2.1 at Re = 5,000 compared to the SSCT, while the corresponding friction factor ratio increases by only 7.85 at Re = 25,000. In contrast, the SDCT with helically arranged elliptical dimples attains the highest PEF value of 1.15 at Re = 5,000.