Jet Impingement Cooling Research Articles

Numerical Study of Eccentric Jet Impingement Cooling on a Heated Cylindrical Surface

Abstract This article presents a comprehensive numerical analysis of the effects of cooling a cylinder using an eccentric slot jet impingement cooling (SJIC). The study focuses on examining the thermal and fluid behavior when the slot jet is offcenter, during impingement cooling. Several turbulence models from the k–ε and k–ω families were compared by evaluating the local Nusselt number profiles at different locations around the cylinder, and these results were compared to experimental data. The findings indicate that the SST k–ω model outperforms the other turbulence models in estimating the Nusselt number in the stagnation region, while the standard k–ω model shows improved performance elsewhere on the cylinder. Furthermore, this study reveals a decrease in the maximum local Nusselt number and a shift in the direction of the nozzle displacement. The presence of swirling/recirculating fluid at the trailing end of the cylinder enhances heat transfer near the back end of the cylinder. The separation and the reattachment of the fluid stream differ depending on the Reynolds number, with low Reynolds numbers resulting in reattachment on the side of the slot jet and higher Reynolds numbers leading to reattachment in the opposite direction. Additionally, the length of the recirculation and swirling zones increases as the nozzle-to-cylinder spacing (H/S) increases. However, as the eccentricity (E/S) increases, the size of the swirl circulation zones decreases and completely vanishes for E/S = 4. This study provides valuable insights for optimal cooling design.

Influence of Buoyancy and Inter-Surface Radiation on Confined Jet Impingement Cooling of a Semi-Cylindrical Concave Plate

Abstract In this article, the confined jet impingement cooling of a semicylindrical concave plate is analyzed numerically. The finite volume approach is applied to two-dimensional numerical simulations in the transient regime. Air is employed as the working fluid and is regarded as nonparticipant for radiation. The investigation is done for different jet Reynolds numbers (Rej) ranging from 100 to 1000, as the Richardson number (Ri) corresponding to this interval ranges between 0.1 and 10. For any Richardson number, the modified Grashof number (Gr*) is fixed at 105. When analyzing the impact of intersurface radiation between the target plate and confined surfaces on the overall cooling performance, three emissivity values (ε= 0.05, 0.5, and 0.95) are taken into consideration. Additionally, simulations are done for the pure convective heat transfer, ignoring intersurface radiation (ε= 0.0). The influence of surface emissivity and the Richardson number on velocity, temperature, and pressure distribution in the flow domain, local dimensionless temperature (θ) alterations on the target plate and confined walls, alterations in convective (Nuc), radiative (Nur), overall Nusselt numbers (Nuovr), pressure coefficient (Cp), and ratio of radiative Nusselt number to overall Nusselt number (Nur/Nuovr) on the target plate are highlighted. The findings demonstrate that surface emissivity has a significant influence on thermal and hydrodynamic boundary layer formation, buoyancy induced flow and heat transfer, and the proportion of intersurface radiation in overall heat transfer rises as the Richardson number and surface emissivity increase. At low Richardson numbers, the pressure in the stagnation region is greater than the atmospheric pressure. However, as the buoyancy effect increases, the pressure in the stagnation region falls below the atmospheric pressure and rises toward the exit.

Jet Impingement Cooling of a Microchannel Heat Sink with Microgroove

The present study works on opportunities in improving the design of micro-channel heatsink (MCHS). The present study focuses on investigating numerically the effects of adding grooves at the MCHS which subject to jet impingement cooling. Commercial software ANSYS Fluent is used and realizable k-epsilon model is adopted to conduct a parametric study on the width and depth of rectangular longitudinal grooves at a constant heat flux of 250 W/cm2 applied at the base of MCHS. Two type of channel designs with grooves i.e. center-groove and side-groove were created and investigated numerically. Results show that addition of grooves generally give improvements in cooling performance and reducing the pressure drop. Some designs of side-grooved channels and center-grooved channels improve the temperature uniformity. The size of the groove affects the flow within the grooves and therefore affect the cooling performance.

Conjugate Heat Transfer Evaluation of Turbine Blade Leading-Edge Swirl and Jet Impingement Cooling With Particulate Deposition

Abstract Internal cooling structures for gas turbine engines are becoming more complicated to push the hot gas temperature as high as possible, which, however, allows particulates drawn into the coolant air to be more readily to deposit within these passages and thus greatly affect their flow loss and thermal performance. In this study, internal swirl cooling and jet impingement cooling subjected to particulate deposition were evaluated and compared using a conjugate heat transfer method, with an emphasis on the thermal effects of the insulative deposits. To accomplish the goal, an unsteady conjugate mesh morphing simulation framework was developed and validated, which involved particle tracking in an unsteady fluid flow, particle–wall interaction modeling, conjugate mesh morphing of both fluid and solid domains, and a deposit identification method. The swirl and the jet impingement cooling configurations modeled the internal cooling passage for the leading-edge region of a turbine blade and were investigated in a dust-laden coolant environment at real engine conditions. Coupling effects between the dynamic deposition process and the unsteady flow inside the two cooling channels were examined and the insulative effects of the deposits were quantified by comparing the temperatures on the external and internal surfaces of the metal channel walls, as well as on the deposit layers. Results demonstrated the ability of the newly developed, unsteady conjugate simulation framework to identify the deposits from the original bare wall surface and to predict the insulation effects of the deposits in the dynamic deposition process. The dust almost covered the entire impingement channel, while deposits were only seen in the vicinity of the jets in the swirl channel. Despite this, a dramatical decrease of convection heat transfer was found in the swirl channel because the swirling flow was sensitive to the interruption of the deposits. In contrast, the deposits improved the heat transfer rate in the impingement channel. When the thermal effects of the deposit layer were taken into account, the wall temperatures of both two cooling geometries were substantially elevated, exceeding the allowable temperature of the metal material. Due to the denser deposit coverage, the impingement channel wall had a greater temperature increase than the swirl channel. In terms of flow loss, the presence of the deposits inhibited the swirl intensity by interrupting the swirling flow and thus reduced the friction loss, whereas the pressure loss was improved by the deposits in the impingement cooling.

Effects of Variable Pressure Outlets for Array Jet Impingement Cooling With a Bidirectional Exit Air Scheme

Abstract Array jet impingement in conjunction with other cooling methods such as effusion cooling is used in gas turbine combustion zones to provide optimized cooling in the form of double wall cooling around a combustion chamber. Utilizing a transient liquid crystal (TLC) technique an experimental investigation into the effects of pressure gradients and single versus multiple exits for array jet impingement crossflow is evaluated in the form of a detailed heat transfer analysis. In this study, four pressure gradients to bias mass flow ratios as (1:1), (2:1), (3:1), and (1:0), two jet array configurations either inline or staggered with jet to jet spacings (x/D = y/D) of 1.4, 1.9, and 2.2, three jet to target distances (z/D) ranging from 2 to 4, and three Reynolds number from 5000 to 15,000 are considered. In total, a test matrix of 72 different performance conditions was evaluated. Results are presented as local and area averaged Nusselt number plots along with local heat transfer coefficient contours. Overall, Nusselt number decreases with increased (z/D) and increased pressure gradient bias toward a single exit from (1:1) to (1:0). There is also slightly better performance from inline jet array configurations compared to staggered configurations.

Experimental and Numerical Study on the Combined Jet Impingement and Film Cooling of an Aero-Engine Afterburner Section

The recent advancement of cooling methodologies for critical components such as turbine blades, combustor liners, and afterburner liners has led to the development of a combination of impingement and film cooling. The present study proposes an efficient cooling technique for a modern aero-engine afterburner liner based on the combination of jet impingement and film cooling. To achieve this, a numerical model is devised to model the film flow over a corrugated liner with several jets impinging over it. The numerical model is validated in a set of in-house experiments as well as against experimental data available in the literature. The experiment is performed for a limited temperature range (i.e., with a low-density ratio). However, the numerical simulations are carried out by varying the blowing ratio from 0.3 to 0.6. The density ratio during the simulations is kept at 3.5. The minimum distance between the impinging plate and the liner is kept at h/D = 1. A detailed analysis of the numerical results indicates a significant drop in the temperature distribution over the liner surface because of the employed cooling technique. The present study also reveals that, under similar operating conditions, the combined jet impingement and film cooling system has the ability to achieve the targeted cooling effect at a lower bleed air flow rate due to its higher effectiveness than that of the standard film cooling arrangement.

Optimization Turbine Blade Cooling by Applying Jet Impingement Cooling Channels

Abstract The aim of this paper is to optimize turbine blade cooling channels by applying jet impingement Method. The selection of experiment data for NASA 3CX turbine blade, and 3D model using solidworks software and create computational fluid dynamics (CFD) simulations used to model the coolant flow and temperature distribution in the vane, while experimental testing can validate the CFD results and provide additional insights into the cooling system's performance., ANSYS FLUENT code was used as a CFD solver, and ANSYS ICEM-CFD was used for mesh generation. MATLAB code is used for calculation using experiment data and this was helpful for simulations. Heat transfer conjugation analysis bases SST shear stress analyses K-ω turbulent model. The results conclude that providing additional information about the cooling channels and how they differ in the studies being compared. The results demonstrate that the cooling channels' hydraulic diameter decreases by a significant percentage (up to 49.70%–69.55%) as they are drawn to the trailing edge of the blade. This can have a significant impact on the heat transfer coefficients and the performance of the cooling system. The pressure side of the turbine blade is observed to follow the Hylton Model, while the current study predicts a large over-anticipated heat transfer coefficient around the Turbine blade head and on the bulk of the suction side. In terms of average heat transfer coefficient, the two models differ by 23.36%. The authors found that the cooling effectiveness for the Optimized jet impingement model is 0.4892 for whole blade and compared it with the cooling effectiveness for the optimized jet impingement model, which is 0.6936, The results of the comparison between the base model and the optimized jet impingement model suggest that the optimized model has a significantly higher cooling effectiveness. The increase in cooling effectiveness of 29.46% for the whole blade and 28.823% for the trailing edge indicates that the optimized jet impingement design provides improved cooling performance. These results highlight the importance of considering optimized cooling designs for turbine blades to maintain efficient and safe operation.

Numerical Investigation of Jet Impingement Cooling with Supercritical Pressure Carbon Dioxide in a Multi-Layer Cold Plate during High Heat Flux

Numerical Investigation of Jet Impingement Cooling with Supercritical Pressure Carbon Dioxide in a Multi-Layer Cold Plate during High Heat Flux

A Review on Experimental and Numerical Investigations of Jet Impingement Cooling Performance with Nanofluids.

Nanofluids offer great potential heat transfer enhancement and provide better thermophysical properties than conventional heat transfer fluids. Application of nanofluids in jet impingement cooling is used for many industrial and scientific purposes as it manages to effectively remove high localized heat. Owing to its tremendous improvement of the heat transfer field, the use of nanofluids in jet impingement cooling has caught the attention of many researchers. This paper reviews previous research and recent advancements of nanofluid jet impingement via both experimental and numerical studies. In experimental approaches, Al2O3-water nanofluids are the most used working fluids by researchers, and most experiments were conducted with conventional impinging jets. As for the numerical approach, the single-phase model was the preferred model over the two-phase model in obtaining numerical solutions, due to the lower computational time required. A deep insight is provided into nanofluid preparation and methods for stabilization. Parameters affecting the performance of the jet impinging system are also investigated with comparison to numerous publications. The main parameters for jet impinging include the jet-to-plate distance (H/D), the shape of the impinged plate (curved, flat or concave), nozzle configurations and the twisted tape ratio. Studies on conventional impinging jets (CIJs), as well as swirling impinging jets (SIJs), are presented in this paper.

Assessment of Convective Heat Transfer Characteristics for Elliptical-Shaped Pin-Roughened Surface for the Jet Impingement Cooling

Abstract In a jet impingement cooling (JIC) system, the layout of the target surface and length of the jet holes can change both the flow field and the heat transfer characteristics. Elliptical-shaped pins (ESPs) with different heights and layouts on the target surface of the extended jet hole configurations were examined numerically in a jet impingement system. The ESPs were arranged in a staggered and circular form. Normalized nozzle length (Gj/Dj = 1.0, 2.0, 6.0) and normalized pin height (Hp/Dj = 0, 0.167, 0.417, 0.667) were investigated as geometric parameters. Also, the effect of different pin layouts (R1, R2, R3) on heat transfer dissipation was studied by changing the number of pin rows in particular configurations. A numerical model was developed and verified with experimental and numerical data from the literature. Numerical analyses were conducted with the shear stress transport (SST) k–ω turbulence model taking the boundary conditions into account under turbulent flow conditions (16,250 ≤ Re ≤ 32,500). Nusselt (Nu) numbers, pressure drop, and the thermo-hydraulic performance of the physical model were quantitatively researched to elucidate the underlying mechanisms of enhanced heat transfer by the ESPs. Results were compared with the orifice surface (Hp/Dj = 0 and Gj/Dj = 6.0). Results showed that area-averaged Nu number on the target wall increased up to 35.82% for Re = 16,250 by R2_Gj/Dj = 1.0 and Hp/Dj = 0.167 compared to the conventional JIC system. The performance evaluation criterion (PEC) was used to analyze the thermo-hydraulic performance of the examined physical models. According to the PEC values, the most feasible parameters for all Re numbers were R3_Gj/Dj = 1.0 and Hp/Dj = 0.167. Furthermore, increasing the number of pin rows in the channel also increased the uniformity of the local heat transfer distribution according to Nu contours.

Effect of Hybrid Nanofluids Concentration and Swirling Flow on Jet Impingement Cooling

Nanofluids have become increasingly salient in heat transfer applications due to their promising properties that can be tailored to meet specific needs. The use of nanofluids in jet impingement flows has piqued the interest of numerous researchers owing to the significant heat transfer enhancement, which is vital in the technological dependence era in every aspect of life, particularly in engineering applications and industry. The aim of this current work is to investigate the effect of hybrid nanofluids concentration and swirling flow on jet impingement cooling through experimental approach. The hybrid nanofluids are prepared through a two-step method and the characterization process is carried out to study the stability and morphological structure of the sample prepared. The prepared hybrid nanofluids are then used as a cooling agent to evaluate the heat transfer performance of jet impinging system. The experimental investigation compares the performance of swirling impinging jets (SIJs) with conventional impinging jets (CIJs) under various jet-to-plate distance (H/D) ratios and nanofluid concentrations. The effects of adding surfactant on nanofluids are also examined. The heat transfer performance of ZnO/water and CuO/water mono-nanofluids are used as comparison to ZnO-CuO/water hybrid nanofluid. The results show that the thermal performance of ZnO-CuO/water hybrid nanofluid is better than that of the mono-nanofluids. Furthermore, as the mass fraction increases, the heat transfer rates improve. The effect of heat transmission by swirling impinging jets is better than that of conventional impinging jets under similar operating conditions. At H/D = 4, Re = 20,000 and hybrid nanofluid concentration at 0.1% under SIJ is observed to have the highest overall Nusselt number.

Application and CFD-Based Optimization of a Novel Porous Object for Confined Slot Jet Impingement Cooling Systems under a Magnetic Field

A novel porous object for the control of the convective heat transfer of confined slot nanojet impingement is offered under magnetic field effects, while optimization-assisted computational fluid dynamics is used to find the best working conditions to achieve the best performance of the system. The flow, thermal patterns, and heat transfer characteristics were influenced by the variation in rotational Reynolds number (Rew), Hartmann number (Ha), permeability of the porous object (Da) and its location (Mx). There was a 14.5% difference in the average Nusselt number (Nu) at the highest Rew when motionless object configuration at Ha = 5 was compared, while it was less than 2% at Ha = 25. At Rew = −600, the average Nu variation was 22% when cases with the lowest and highest magnetic field strength were compared. The porous object provides an excellent tool for convective heat transfer control, while the best performance was achieved by using optimization-assisted computational fluid dynamics. The optimal sets of (Rew, Da, Mx, AR) for porous object were (−315.97, 0.0188, −1.456, 0.235), (−181.167, 0.0167, −1.441, 0.2), and (−483.13, 0.0210, −0.348, 0.2) at Ha = 5, 10, and 25, respectively. At the optimal operating point, the local Nu enhancements were 19.46%, 44.86%, and −0.54% at Ha = 5, 10, and 15, respectively, when the no-object case was compared, while the average values were 7.87%, 8.09% and 5.04%.

Improved design and comparative evaluation of controlled water jet impingement cooling system for hot-rolled steel plates

This work focuses on improved design modification and development of Controlled Water Jet Impingement Cooling System for improving mechanical and metallurgical properties of steel using locally sourced materials. The modification comprised introduction of water pump, adjustable impingement gap mechanism and replacement of complicated hydraulic/chain conveyor mechanism with screw conveyor mechanism. The plant was designed, fabricated and instrumented with temperature and flow probes to simulate the actual operating conditions of steel mill industry. Comparative performance results revealed 8% increase in cooling rate of the improved system over the existing technology. Moreover, with a test-plate initial temperature at 550 °C, a controlled cooling temperature of 160 °C was achieved which produced film and nucleate boiling heat extraction effect. This influenced microstructural properties of the test plates. The plates post treatment exanimations of the grain microstructure and mechanical properties revealed good martensite-phase transformation and enhanced “advanced-steel” hardness of Rockwell 59.9, respectively. In addition, impact energy test showed good value range of 56 to 63 J which compared favorably with AISI standard of 44.3 J. This therefore, gave 53% hardness and 26% to 42.2% impact of improved mechanical and desirable hardened martensite needle-like structure of metallurgical properties thereby saving the high cost of alloying.

Performance Assessment of Jet Impingement Cooling With Cross Flow

Performance Assessment of Jet Impingement Cooling With Cross Flow

Comparative performance of jet and spray impingement cooling in steel strip run-out table: experimental results

ABSTRACT This paper presents a comparative performance study of cooling techniques based on air-assisted water spray and jet impingement for heated moving metallic plates. To achieve the heat transfer characteristics of spray and jet cooling methods, an experimental setup was developed to accommodate the spray (SIC) and jet impingement cooling (JIC). The temperature at different locations of the plate was taken by K-type thermocouples embedded therein and attached to CHINO-make data acquisition system. The cooling curves obtained were utilised for computing the cooling rates. Experiments were conducted by varying the parameters, e.g. pressure of air and water, distance between plate and nozzle tip and speed of plate as per Taguchi design of experiments. The results revealed that SIC has great advantage over the JIC method under the same thermal conditions. There was a fall of cooling rate with increase in plate thickness for both SIC and JIC. The requirement of shorter length of run-out table (ROT) in case of SIC has established the cost effectiveness of using SIC compared to JIC. The cooling process played a critical role in steel manufacturing industry where the determined cooling rates evaluated the setup costs during planning phase of the project.

A computational study on nanofluid impingement jets in thermal management of photovoltaic panel

Thermal management is essential to improve the overall performance of photovoltaic (PV) cells. This study presents a comprehensive numerical study on a PV panel to achieve economic efficiency cooling system. A nanofluid jet impingement cooling (JIC) system with different configurations is developed and integrated into the PV panel to control the surface temperature. A three-phase mixture model shows a satisfactory agreement between the simulation and measurement values. Then, the simulations are conducted to understand the importance of different influencing parameters, including inlet temperature (20–40 °C), number of nozzles (8−24), mass flow rate (0.045–0.12 kg/s), jet-to-surface distance (5.1–55 mm), and nozzle diameter (1 and 2 mm). Numerical results demonstrate that uncooled PV temperature reaches 68.5 °C, while using the JIC system reduces that by 36.4 °C. Lower inlet temperatures and larger mass flow rates result in higher PV efficiency. The number of nozzles affects the surface temperature and its uniformity. Small jet-to-surface distances enhance the turbulence kinetic energy and the heat transfer rate. For the nozzle diameters of 1 and 2 mm, the maximum power increment increases to 20.36% and 20.19%, respectively. However, the nozzle diameter of 1 mm increases the pumping power with a coefficient of energy of 1.18.

Jet Impingement Cooling Enhanced with Nano-Encapsulated PCM

In the present study, the laminar flow and heat transfer of water jet impingement enhanced with nano-encapsulated phase change material (NEPCM) slurry on a hot plate is analytically investigated for the first time. A similarity solution approach is applied to momentum and energy equations in order to determine the flow velocity and heat transfer fields. The effect of different physical parameters such as jet velocity, Reynolds number, jet inlet temperature, and the NEPCM concentration on the cooling performance of the impinging jet are investigated. The volume fraction of NEPCM particles plays an essential role in the flow and heat transfer fields. The results show that NEPCM slurry can significantly enhance the cooling performance of the system as it improves the latent heat storage capacity of the liquid jet. However, the maximum cooling performance of the system is achieved under an optimum NEPCM concentration (15%). A further increase in NEPCM volume fraction has an unfavorable effect due to increasing the viscosity and reducing the conductivity simultaneously. The effect of adding nano-metal particles on the heat transfer performance is also investigated and compared with NEPCM slurry. NEPCM slurry shows a better result in its maximum performance. Compared with the water jet, adding nano and NEPCM particles would overall enhance the system’s thermal performance by 16% and 7%, respectively.

Numerical Investigation on Flow and Heat Transfer Characteristics of Single Row Jet Impingement Cooling with Varying Jet Diameter

Numerical Investigation on Flow and Heat Transfer Characteristics of Single Row Jet Impingement Cooling with Varying Jet Diameter

Effect of Slot-Shaped Pins on Heat Transfer Performance in the Extended Jet Impingement Cooling

Effect of Slot-Shaped Pins on Heat Transfer Performance in the Extended Jet Impingement Cooling

Local Heat/Mass Transfer of Array Jet Impingement Cooling With Pin-Fin Heat Sinks

Impingement cooling is an effective method for removing heat from a high temperature target surface using sprayed jets oriented to impinge on the surface. Detailed local heat-/mass-transfer distributions are measured using the naphthalene sublimation method. The main parameters of this study are jet hole spacing ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$s/d = 4$ </tex-math></inline-formula> , 8) and crossflow rate. The heat-/mass-transfer coefficients on the target surface are significantly influenced by the crossflow volume and pin-fin structures, and the degree of this influence is affected by different jet hole spacings. The results indicate that a small hole spacing increases the heat/mass transfer by 15%–30% than a large hole spacing for the Reynolds number of 15 000.