Jet Impingement Research Articles

Damage characteristics of high-temperature sandstone impacted by cetyltrimethylammonium bromide-enhanced jet

High-pressure water jet technology is an efficient and eco-friendly method with the potential to enhance rock-breaking efficiency in deep-earth high-temperature environments. This study introduces the use of the surfactant cetyltrimethylammonium bromide (CTAB) in water jets to improve thermal exchange between low-temperature jets and high-temperature rocks, aiming to optimize rock-breaking efficiency under high-temperature conditions in deep reservoirs. Experiments were conducted using jets with varying CTAB concentrations impacting rock at different temperatures to assess the feasibility and elucidate the underlying rock-breaking mechanisms. Computed Tomography (CT) combined with three-dimensional reconstruction was employed to establish the internal damage field of the rock, thereby analyzing the jet rock-breaking mechanisms. The findings indicate that the erosion pit formed in sandstone under the impact of a pure water jet has a regular inverted “Ω”-shape, while the pit formed under CTAB-enhanced jets resembles a “J”-shape. Furthermore, at elevated rock temperatures, the depth and volume of erosion pits created by jet impacts are greater than those at room temperature. At 100 °C, the rock-breaking volume increases by 16.81% with a pure water jet, whereas it increases by 75.46% with a jet containing 500 ppm CTAB. Optimal concentrations of CTAB additives range from 500 to 1000 ppm, substantially enhancing rock-breaking efficiency at high temperatures by bolstering heat exchange between the jet and rock and intensifying the water wedge effect. These findings provide a theoretical basis and novel approaches for hydraulic fracturing of deep, high-temperature hard rock.

Multi-objective geometric optimization of protrusion, droplet ribs, and inclined upper plate of a slit jet impingement heat sink to enhance its thermal performance

To meet the needs of heat transfer and temperature uniformity in the heat dissipation of high-heat-flux electronic devices, a novel slit jet impingement heat sink with a protrusion in the stagnation region, droplet ribs in the wall jet region, and an inclined upper-plate (PDI-SJIHS) is proposed, the coolant is Al2O3-H2O nanofluid. The influences of the structural parameters of the above three components and the Reynolds number on the heat transfer and flow of the PDI-SJIHS are studied numerically. Using the comprehensive heat transfer and temperature standard deviation as objective functions, a multi-objective optimization of PDI-SJIHS is conducted using non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ). The results indicate that the combination of the three components enhances the thermal performance of the PDI-SJIHS, compared with the slit jet impingement heat sink with only one of the above components. Rising the Reynolds number can enhance the thermal characteristics of the PDI-SJIHS. For a Reynolds number of 8000 and nanofluids with a 3% volume fraction, the average convective heat transfer coefficient, friction coefficient, and comprehensive heat transfer coefficient of the optimized PDI-SJIHS are increased by 182%, 153%, and 108%, respectively, and the standard deviation of temperature is 91% less than that of F-SJIHS.

Numerical simulation study of temperature non-uniformity on the surface of array jet impingement cold plate

Numerical simulation study of temperature non-uniformity on the surface of array jet impingement cold plate

Flow and heat transfer characteristics of a novel jet impingement cooling with multi-layer drainage channels at blade leading edge

Flow and heat transfer characteristics of a novel jet impingement cooling with multi-layer drainage channels at blade leading edge

Numerical study on leakage, diffusion and accident consequences of liquid hydrogen jet and analysis of influencing factors

Key equipment in liquid hydrogen refueling stations (LHRS), such as liquid hydrogen (LH2) storage tanks or cryogenic pumps, are usually equipped with multiple protective measures. The likelihood of a catastrophic explosion is minimal. More commonly, valve or pipeline failures occur, leading to LH2 jet release. This study utilizes three-dimensional computational fluid dynamics (CFD) software FLACS to develop a numerical simulation method for LH2 jet release. A simple open environment scenario was created, and experimental data were used to verify the feasibility of the numerical simulation principles. The study analyzed the effects of parameters such as wind speed and direction, presence of barrier walls, and the height and distance of these walls on the consequences of LH2 jet release incidents. Results indicate that for LH2 impingement jet, the longitudinal dispersion distance is greatest under downwind conditions. Under crosswind conditions, the horizontal dispersion distance, flammable volume, and flammable mass are highest. Under upwind conditions, the equivalent stoichiometric cloud volume, explosion overpressure, and damage area are the largest, resulting in the most severe consequences. As wind speed increases, the explosion overpressure and damage area under upwind conditions initially increase and then decrease, with the most dangerous wind speed being 5m/s. Walls can effectively reduce the hazard range of explosions and fires following liquid hydrogen leakage from small holes. The optimal wall height is between 3m and 4m, and the optimal distance from the leakage point is around 9m. These findings provide crucial engineering guidelines for optimizing barrier wall design and wind mitigation strategies in LHRS. Furthermore, by improving safety standards and reducing the risks of explosions, this research plays a pivotal role in fostering public trust and promoting the broader use of LH2 as a clean energy source.

Heat Transfer Characteristics of Passive, Active, and Hybrid Impinging Jets: A Review

Heat Transfer Characteristics of Passive, Active, and Hybrid Impinging Jets: A Review

Outlet Configuration of a Reversed Circular Flow Jet Impingement Photovoltaic Thermal (PVT)

The utilization of the jet impingement technique is a prevalent approach in enhancing the efficiency of photovoltaic thermal (PVT) collector through the augmentation of heat transfer rate. The present work introduces a novel approach known as the reverse circular flow jet impingement (RCFJI) on a PVT collector. The performance analysis of the PVT collector was assessed through the utilization of CFD simulation. The RCFJI was installed to a jet plate which incorporates 36 holes. The holes were positioned at a spacing of 113.4 mm (x-axis) and 126 mm (y-axis). The air outlet channel of the jet plate has been configured into four different configurations: one hole (1h), three holes (3h), four holes (4h) and five holes (5h) to analyze the best outlet configuration leading to the highest energy performance. The simulation evaluation encompassed a range of solar irradiance spanning from 600 W/m<sup>2</sup> to 900 W/m<sup>2</sup>, while the mass flow rates varied from 0.01 kg/s to 0.14 kg/f for each geometrical design. Based on the research, the configuration that records the highest efficiency was 1h. The maximum photovoltaic efficiency recorded was 11.38% at 600 W/m<sup>2</sup> and mass fl ow rate of 0.14 kg/s. While the maximum thermal efficiency was 63.2% at solar irradiance 900 W/m<sup>2</sup> and mass flow rate of 0.14 kg/s.

Three-dimensional analysis of turbulent twin-swirling jets onto a heated rectangular prism in a channel

Purpose The purpose of this study is to investigate the impact of swirling jet flow on the cooling performance of a heated rectangular prism placed within a channel. The primary aim is to explore the influence of varying aspect ratios (AR) of the prism and different fluid Reynolds numbers (Re) on the cooling efficiency. Design/methodology/approach The numerical analysis is performed using a finite volume-based solver, which incorporates the large eddy simulations (LES) turbulence model. The setup consists of twin 45° swirling jets directed at isothermally heated bodies, with water used as the cooling medium. The rectangular prism is oriented perpendicularly to the channel flow direction, positioned one unit distance from the inlet. This study examines three distinct aspect ratios (AR = 0.5, 1 and 1.5) and a range of Reynolds numbers (6000 = Re = 20000). Findings The results indicate that cooling efficiency improves as the aspect ratio decreases and the Reynolds number increases. Higher Reynolds numbers enhance jet impingement and turbulent mixing, which are crucial for efficient heat transfer. Conversely, lower Reynolds numbers lead to diminished impingement and reduced cooling efficiency. Increasing the Reynolds number from 6000 to 20000 elevates the average Nusselt number by 35% (for AR = 0.5) and up to 45% (for AR = 1.5). It was observed that lower aspect ratios produce superior cooling effects due to intensified localized jet interactions. Originality/value This research significantly contributes to the fields of fluid dynamics and thermal engineering by elucidating the influence of swirling jet flows on the cooling of heated surfaces. The findings offer valuable insights for optimizing the design and performance of cooling systems across various industrial applications.

Custom, High Density Power Modules Enabled by Thermal Integration Technologies

Researchers at the University of Arkansas are achieving significant strides in power electronic packaging, focusing on the critical needs for high power density and integrated thermal management. They have introduced an innovative non-metallic jet impingement cooler, produced via advanced additive manufacturing techniques, which has proven to be effective in lowering thermal loads. Specifically, it reduces junction temperatures by as much as 30°C and attenuates electromagnetic interference, a crucial factor for the efficiency of high-power silicon carbide MOSFET-based inverters. In response to the 2021 PowerAmerica Institute challenge, the team engineered a high-voltage power module, achieving the specifications of 1.7-kV/1600-A within a confined volume of 100 cm³. This module exemplifies the successful integration of thermal and electrical systems in a space-efficient package, highlighting the practical resolution of high-density packaging challenges. The process has provided insights into the behavior of thermal resistance in such compact modules and the associated operational constraints. Further extending their research, the team has examined advanced cooling techniques employing dielectric fluids, targeting applications surpassing 1.2 kV. They have balanced the turbulence within fluid movement and the fluid’s voltage blocking capacity, essential for the stability of thermal management systems in high-voltage electronics. Moreover, the group has developed an empirical model for direct jet impingement cooling using dielectric fluids, optimizing for enhanced cooling performance with minimal flow rates. They are also researching in the area of two-phase immersion cooling, with a focus on maintaining electrical isolation, especially during phase changes, and conducting assessments of breakdown voltages in boiling dielectric fluids. These efforts are pivotal in guiding the next generation of efficient, compact power electronic packaging solutions, contributing significantly to the field’s future advancements.

Inertial collapse of a gas bubble in a shear flow near a rigid wall

Despite the extensive research on bubble collapse near rigid walls, the bubble collapse dynamics in the presence of shear flow near a rigid wall is poorly understood. We conduct direct simulations of the Navier–Stokes equations to explore the bubble dynamics and pressures during bubble collapse near a rigid, flat wall under linear shear flow conditions. We examine the dependence of the bubble collapse morphology and wall pressures on the initial bubble location and shear rate. We find that shear distorts the bubble, generating two re-entrant jets – one developing from the side opposite to the mean flow and the other from the far end toward the wall. Upon impact of the jet on the opposite side of the bubble, water-hammer shocks are produced, which propagate outward and interact with the convoluted bubble shape. The shock stretches the bubble towards the wall, resulting in a closer impact location for the jet originating from the far end compared with the case with no shear flow. The water-hammer pressure location can be approximated as the theoretical distance travelled by a particle initialised at the bubble centre with the corresponding constant shear flow velocity. The maximum wall pressures can thus be predicted by considering the distance between the far jet impingement location and the wall along the wall-normal direction. As the shear rate is increased, the maximum wall pressure increases, although only marginally. We determine the critical initial stand-off distance from the wall at which the bubble morphology is shear dominated, i.e. characterised by converging re-entrant jets.

Competing pathways of intracranial aneurysm growth: linking regional growth distribution and hemodynamics.

The complex mix of factors, including hemodynamic forces and wall remodeling mechanisms, that drive intracranial aneurysm growth is unclear. This study focuses on the specific regions within aneurysm walls where growth occurs and their relationship to the prevalent hemodynamic conditions to reveal critical mechanisms leading to enlargement. The authors examined hemodynamic models of 67 longitudinally followed aneurysms, identifying 88 growth regions. These regions (of enlargement) were pinpointed through alignment and distance mapping between baseline and follow-up models. Aneurysm wall subdivisions were created based on saccular anatomy and flow-related characteristics, which were used to assess local hemodynamics. The distribution of growing regions across these subdivisions was then studied and stratified by aneurysm location and morphology to reveal distinct growth patterns. Statistical significance was evaluated using the Kruskal-Wallis and Mann-Whitney tests. Growth predominantly occurred in the body (p < 0.0001) of aneurysms, with anterior communicating artery (ACom) (p < 0.0001) and lateral (p = 0.002) aneurysms showing a significantly greater tendency for growth in this region. In comparison, middle cerebral artery (MCA) (p < 0.0001) and bifurcation (p = 0.0001) aneurysms demonstrated growth in both the dome and the body. Notable differences in growth distribution across saccular regions included ACom versus MCA (neck, p = 0.038), bifurcation versus lateral (neck, p = 0.008), and so forth. The central flow region saw the most growth (p < 0.0001); although not significant, ACom (p = 0.196) and lateral (p = 0.218) aneurysms showed a tendency for growth in inflow and central zones, while MCA (p = 0.001) and bifurcation (p < 0.0001) aneurysms were more likely to grow in the central flow region. Two primary mechanisms seem to influence aneurysm growth: high-flow impingement jets in the neck, body, and inflow zones leading to wall degeneration/thinning, mainly in ACom aneurysms; and slow, oscillatory flow conditions in the dome and central flow zones promoting wall remodeling/thickening, mainly in MCA aneurysms. This latter mechanism is also observed as secondary flows in ACom aneurysms. These findings emphasize the need to understand the distinct and sometimes concurrent mechanisms of aneurysm growth, advocating for targeted monitoring and interventions that mitigate rupture risks by considering the unique hemodynamic environments within different aneurysm regions and locations.

Study of Rewetting Behavior in AHWR Fuel Cluster During Loss of Coolant with Water Jet Impingement

This study investigates the rewetting behavior of an Advanced Heavy Water Reactor (AHWR) fuel rod bundle during a loss-of-coolant accident using computational fluid dynamics simulations with ANSYS CFX. The analysis focuses on the cooling effectiveness of radial jet impingement at varying flow rates and its impact on rewetting temperature and wetting delay. Simulations were conducted by maintaining a constant initial wall temperature, with cooling curves and contour profiles extracted from various angular positions along the axial rod surfaces. The results reveal that rewetting is faster near the jet sections due to enhanced coolant interaction, while areas farther from the jets exhibit delayed wetting and elevated wall temperatures, where vapor accumulation hinders heat dissipation. Higher flow rates minimize wetting delays and improve cooling by promoting transition and nucleate boiling. However, irregular coolant splashing and vapor dominance disrupt the uniformity of rewetting across the bundle. The study highlights the limited impact of increased flow rates on achieving consistent rewetting along the entire rod length, with substantial fluctuations observed in cooling performance at different vertical positions. The findings emphasize the need for further research under high-temperature steam conditions to better understand boiling mechanisms and improve the stability of emergency cooling systems in nuclear reactors.

Effect of Target Surface Rotation and Jet Exit Reynolds Number on Thermal Performance in Single and Multiple Jet Impingement(s)

Effect of Target Surface Rotation and Jet Exit Reynolds Number on Thermal Performance in Single and Multiple Jet Impingement(s)

Numerical Analysis of Liquid Jet Impingement through Confined Uniform Cooling Channels Employing Porous Metal Foams

Numerical Analysis of Liquid Jet Impingement through Confined Uniform Cooling Channels Employing Porous Metal Foams

EFFECT OF SECONDARY JET INCLINATION ANGLE ON HEAT TRANSFER IN A CONFINED IMPINGING JET ARRAY

In this study, the heat transfer effects on the impingement surface in confined impinging array jet flows with inclined secondary jets were experimentally investigated. Temperature distributions were obtained with a thermal camera throughout the center axis of the target plate for Reynolds number values of 20,000 and 30,000, inter-plate aperture values of 0.5, 1, 3, and 6, and secondary jet inclination angles of 45&amp;deg;, 52.5&amp;deg;, and 60&amp;deg;. From the temperature distributions obtained, the influence of Reynolds number, inter-plate aperture, and inclination angle of secondary jets on the Nusselt distributions on the target plate was investigated. It was perceived that the Nusselt values on the target plate increase with increasing Reynolds number and decrease with increasing inter-plate aperture. The location of the top points of the Nusselt number distribution is shaped on the target plate in line with the axes of the secondary jets. These distributions shift to larger &amp;#177; r/D values as the aperture between the plates increases. As the inclination angle of the secondary jets increases, the positions of the secondary jets on the target plate approach the primary stagnation zone, and the top points at these positions become stronger. The most homogeneous Nusselt number distribution occurs when the secondary jet inclination angle is 60&amp;deg; and the aperture H/D &amp;#61; 1.

Heat Transfer Characteristics of Oil Jet Impingement Cooling on a Stator Segment Exterior Surface for Traction Motors with Concentrated Windings

Heat Transfer Characteristics of Oil Jet Impingement Cooling on a Stator Segment Exterior Surface for Traction Motors with Concentrated Windings

FINNED AND UNFINNED THERMAL RESISTANCES OF A METAL FOAM UNDER JET IMPINGEMENT CONDITIONS

Heat transfer in a flat plate with metal foam under impinging jet conditions is a complex combination of conduction (finned) and convection (unfinned) heat transfer. This study reports an analytical approach for the quantification of finned and unfinned heat transfer from a targeted plate with metal foam under impinging jet conditions. Along with the quantification of heat transfer modes, the interstitial heat transfer, the efficiency of metal foam as a fin, and thermal resistances are also quantified analytically. The analysis is carried out for rectangular slot jet and multiple air jet impingement conditions. The varying parameters are jet-to-plate spacing, metal foam thickness, and Reynolds number. The results suggest that for the slot jet case, the finned and unfinned heat transfer is around 70 and 30 percent of the total heat transfer independent of the foam thickness. However, for multiple jet case, finned and unfinned heat transfer is around 50 percent each except for 12 mm thickness. The interstitial heat transfer coefficient and fin efficiency increase with a decrease in the thickness of the foam. For both slot and multiple jet impingement cases, the thermal resistance to unfinned heat transfer is greater in comparison with the finned heat transfer. The presence of metal foam on the flat plate incenses the overall heat transfer by two times the smooth flat plate.

Impinging jet ventilation: Mitigating influenza transmission through partition and exhaust layout optimization

This paper investigates the transmission characteristics of cough droplets from infected individuals in office environments under the influence of an impinging jet ventilation (IJV) system based on the Eulerian–Lagrangian model. The accuracy of the dispersed phase model and the IJV system simulation was validated by analyzing a single droplet evaporation model, publicly available jet experimental results, and previously simulated results. The effects of different exhaust locations, the relative positioning of the IJV system to the infected individual, and the application of partitions on the spatial propagation characteristics of droplets are explored. The results indicate that partitions exhibit a significant ability to obstruct and capture droplets. Under static conditions, they are capable of capturing over 36% of droplets generated by coughing, although this efficiency may be slightly influenced by the ventilation system. The IJV system notably affects droplet movement, with droplets progressively converging toward the upper-left corner of the room as the airflow develops. The positioning of the exhausts, in combination with the IJV system, is crucial in impeding and removing droplets. Taking into account variations in the infected individual's position, a centrally located exhaust arrangement might provide the more effective inhibition of virus droplet dispersion.

Carbon Neutrality Perspective: Enhanced Failure Performance and Efficiency of Circulating Particle Jet Impact Drilling in Deep-Hard Rock

Carbon Neutrality Perspective: Enhanced Failure Performance and Efficiency of Circulating Particle Jet Impact Drilling in Deep-Hard Rock

Optimizing the Ventura Nozzle for Abrasive Jet Plant

Pneumatic abrasive surface treatment is an integral part of many technological processes used for applying coatings, performing repair or doing a restoration work, etc. The operation efficiency of the pneumatic abrasive plant is characterized by several factors. The main factor is the time of surface treatment of the material. The faster the surface treatment, the higher the treatment efficiency since a large amount of compressed air and abrasive material is required for the operation of a pneumatic abrasive plant. The efficiency of the pneumatic abrasive plant is most affected by the operating nozzle, the design of which defines the characteristics of the air-abrasive mixture. The operating nozzle is designed to form a jet and increase the speed of the working flow consisting of continuous and dispersed phases. The effect on the geometric dimensions and design of the nozzle can be varied by its characteristics. The operating characteristics of the nozzle are its main parameters that define the processing time of the material surfaces, in particular the speed of the working mixture at the nozzle outlet, the mass flow rate of the dispersed and continuous phases, the reaction force of the jet, and the value of contact stresses on the processed surface caused by the jet impact. The purpose of this research is to optimize the geometry of the operating nozzle of the pneumatic abrasive plant. The implementation of the set goal is ensured by using the plan of the full factorial experiment, performing a series of numerical studies using the ANSYS software package. The obtained data are verified on a special experimental stand designed for studying the operating nozzles of the pneumatic abrasive plant. Based on the obtained research data we can give practical recommendations for the design of operating nozzles used for the abrasive jet processing of material surfaces.