Jet Impingement Technique Research Articles

Assessment of the impact of jet impingement technique on the energy efficiency of air-cooled BIPV/T roof tile

Assessment of the impact of jet impingement technique on the energy efficiency of air-cooled BIPV/T roof tile

Experimental and Numerical Investigation for Hydrothermal Performance of the Jet Impingement Microchannel Heat Sink

Abstract This study experimentally investigated the hydrothermal and overall performance of the microchannel heat sink incorporating the jet impingement technique. Later on, a numerical model is developed using the finite volume-based tool fluent of the commercial software ansys and validated with the experimental results. Improvement in the cooling performance for the fluid impinging normal to the surface is observed in comparison to the parallel flow of fluid in the microchannel. Similarly, variation in the jet impingement microchannel heat sink performance for the single-jet and multijet is also explored. Hydraulic and thermal characteristic parameters such as pressure drop, average heat transfer coefficient, maximum wall temperature, and figure of merit are evaluated for the analysis. Multijet impingement flow exhibited superior heat transfer with respect to the parallel flow and single impingement flow but offered remarkably higher pressure drop. However, the Figure of Merit value is superior for the multijet impingement flow technique with 5 number of jet nozzles. In addition, increasing as well as decreasing the number of jets from 5 jet nozzles for the same mass flowrate diminishes the overall performance of the jet impingement microchannel heat sink.

Tribo-Corrosion Control with Molecules of Bio-Origin: Experimental Studies and Theoretical Insights

Tribo corrosion control of 6061 aluminum alloy was done by using naturally available Boswellia serrata (BWS) extract as green inhibitor. Studies were done in artificial sea water slurry containing 0.03% sand particles via a submerged jet impingement technique. Electrochemical studies were the majour techniques adopted for corrosion rate measurement in the absence and in the presence of inhibitor. Investigation was done at different flow rates and at different temperatures. Detailed surface study was done for sand particles before and after impingement using scanning electron microscope. Surface morphology of aluminum sample was done before and after the addition of inhibitor. For a given flowrate inhibition efficiency decreased with increase in temperature. This suggested the possibility of physical adsorption. Results were fitted into suitable adsorption isotherm. Mechanism of adsorption was supported and substantiated by quantum chemical calculations using Density Functional Theory (DFT). The best corrosion–erosion resistance was obtained at a concentration of 1000 ppm Boswellia serrata at 303 K under 4 L min−1. DFT studies supported the adsorption mechanism of the inhibitor on the surface of metal under tribological conditions. The outcome of this work will help in research that is focused on development on green inhibitors for corrosion inhibition under dynamic multi flow conditions.

Experimental investigation of effects of convective heat transfer and thermal performance of impinging jet on a metal plate with porous media

This experimental investigation is aimed to evaluate the effects of convective heat transfer phenomena in an aluminium metal flat disc/plate placed below metal foam using a single round jet of air impinging in a confined region. The Jet impingement technique contains pressurized air, which is configured for certain specific application. It is designed to spray the fluid with the help of a nozzle on the surface of the disc or plate which is being heated or is being cooled. To understand the heat transfer phenomena in a metal plate with metal foams facing round air jet impingement; three metal foams of similar geometries but of different porosities and permeabilities are taken for study. Each experiment is performed with seven different flow rates and at two different heights with two different heat flux values. The recorded measurements are temperatures, pressure differences, flow rates, resistance voltages and currents, and time. The outcomes of the experimental data are analysed and compared results of all four distinct kinds of metal foams with different jet to plate height and at different heat fluxes. It is concluded that heat transfer efficiency may or may not increase depending upon the metal foam used. Overall, the conclusions are extremely useful in engineering.

Analysis of Heat Flux Quenching of a SS-316L Rod Using Nanofluids

Quenching is one of the rapid cooling processes; however, the jet impingement technique is an efficient method for cooling in constrained space. In the nuclear reactor, to prevent the loss of coolant accident condition, de-ionized water is stored in the repository of the emergency core cooling system. Nanofluids exhibit better heat removal capacity, thus, the present article investigates experimentally an optimum oxide based nanofluid under various parameters such as set wall temperature, mass flow rate, and concentration. Quenching curves with different working fluids at a particular heat flux condition have been recorded at different locations of the heater surface. In case of heat flux quenching, limiting heat flux is defined as the boundary heat flux after which the quench front is not able to cool the heater surface. Quench front velocity calculation is the criteria to decide the limiting case. In case of nanofluids, it was observed that there was enhancement in the value of limiting heat flux under various parameters as compared to de-ionized water.

Machine learning algorithms to study the relative roles of jet convection and natural convection in the presence of surface roughness elements on enhancement of jet impingement heat transfer

Based on data-driven approaches, eight machine-learning algorithms have been proposed to characterize the heat transfer performance of turbulent jet impingement cooling. These algorithms are designed to cool high-heat-flux surfaces modified with single protrusions, multi-protrusions, or V-grooves. To train these algorithms, an experimental dataset was used, which included 184 experiments with Reynolds numbers ranging from 10,000 to 33,000, nozzle exit-to-plate distances ranging from 2 to 10 jet diameters, and two different heat inputs of 60 W and 90 W. Multiple linear regression algorithms in Python programming were used to model jet impingement cooling, showing that the proposed machine learning models provided more accurate predictions with a 20.4 % to 66.5 % relative residual improvement over the existing conventional regression model based on performance metrics like R2 and relative residual. This improvement was leveraged to quantify natural convection's impact on the effectiveness of heat transfer enhancement due to different types and sizes of roughness elements in high-temperature applications. The research found that as the protrusion surface area increased from 0.02 % to 0.188 % compared to the flat plate, the effectiveness of heat transfer enhancement decreased from 2.69 % to 8.37 % at similar operating conditions. These results revealed that natural convection, which opposes forced jet impingement, was strengthened with increased heat input values, roughness element surface area, and the local turbulence generated. The higher natural convection weakened the enhancement afforded by jet impingement on the modified plates relative to the flat plate. Additionally, the capabilities of machine learning algorithms were explored to unlock the full potential of the jet impingement technique and to overcome the associated complexity in jet impingement applications for next-generation electronics cooling. Finally, the Decision Tree Classifier algorithm was applied to classify the performance of the surface roughness element as either effective or ineffective.

Differential Microstructure and Properties of Boron Steel Plates Obtained by Water Impinging Jet Quenching Technique

Soil‐working tools in agriculture are made of boron‐containing steels with high wear resistance and hardenability. Nevertheless, these tools are subject to high impacts, abrasive wear, and fatigue and are therefore prone to failure. To combine varying levels of properties within one component in as‐quenched condition can be beneficial for such products. To obtain this property variation, a component must undergo a complex and controllable cooling. Therefore, the aim of this work is to obtain a microstructure gradient along two 15 mm‐thick steel plates in a newly developed test rig by water jet impingement technique to confirm its controllability and flexibility. Furthermore, a quenching simulation model is created for hardness prediction using phase transformation data from a machine learning tool. Microstructure variation is observed using light optical microscopy and the electron backscatter diffraction technique. Mechanical properties are studied through tensile tests and hardness measurements and are also compared with simulation results. The 0.27 mass% C steel sample is obtained in almost fully martensitic state transitioning to a softer ferritic/bainitic condition, while the 0.38 mass% C steel sample results predominantly into a fully hardened martensitic state and slightly shows ferritic and bainitic features along the sample. The quenching simulation model shows promising hardness prediction for both steels.

Energy and exergy analysis of a solar-thermal air collector design utilizing a novel jet impingement technique: an experimental study

Energy and exergy analysis of a solar-thermal air collector design utilizing a novel jet impingement technique: an experimental study

Numerical Study of Jet Impingement on Heated Sink Covered by a Porous Layer

This numerical study aims to enhance the heat transfer efficiency by dissipating the heat Emitted from electronic processors. A jet impingement technique is utilized with porous layer covering a metal fin as a heat sink. Forced convection and normal convection (due to the buoyancy effect) are taken into consideration. The two equations model (Local Thermal Non-Equilibrium LTNE) employed to describe the energy equations of the two phases of the porous surface. Finite Element Method (FEM) used to discretize these equations to obtain the numerical solution. To make this study closest to the reality, constant heat flux boundary condition is applied underneath the metallic heat sink. The geometry comprises of three domains: Free flow channel, Porous layer and Metal fined heat sink. In order to simulate the heat transfer, isotherms; streamlines and Nusselt number have been considered. Investigation has been done by inspecting the effects of the pertinent non-dimensional parameters such as: Reynolds number (Re = 100-900), Darcy number (Da = 10-1-10-6), Richardson number (Ri = 0.1-100) and Porosity (ε = 0.85-0.95). The results show that increasing Re and decreasing ε lead to enhance Nusselt number. Richardson number below 100 has no significant effects on Nu. At Re above 400, Nusselt number proportional with Darcy number. The enhancement of Nusselt number is found to be 250 % by increasing Re from 100 to 900, 290 % by decreasing ε from 0.95 to 0.85 and about 13 % by increasing Darcy number from 10-6 to 10-1.

Effect of new design of elongated jet hole on thermal efficiency of solar air heater

Effect of new design of elongated jet hole on the thermal efficiency (ηth) of a solar air heater (SAH) has been numerically studied in this paper. Jet impingement technique, which is one of the important active techniques, has been implemented on the absorber plate of the SAH surface to increase the convective heat transfer performance. Several designs of elongated jet hole (EJH) technique (gradually increasing, gradually decreasing along the crossflow direction, and equally extended), which is highly effective application to get rid of cross-flow, has been inserted to the jet plate. The main interest of this paper is to investigate the effect of different EJH configurations on convective heat transfer performance and ηth of the SAH. 15 × 7 array of jets have been mounted on the confinement plate. Results have been compared with the conventional SAH, which has the jet impingement Case1. Numerical computations have been conducted using RNG k-ε turbulence model. Average Nusselt number (Nu) on the absorber plate surface, ηth of the SAH, and performance evaluation criteria (PEC) have been quantitatively investigated comprehensively. As a result of calculations, the Nu and ηth of SAH can be enhanced by 31.80 % and 2.46 %, respectively, using Case4 instead of Case1 at Re = 25000. Besides, the pressure drop of SAH dramatically rises by 10.26 %, when Case4 and Case1 compared with each other at Re = 25000. Despite increment in pressure drop, the PEC value achieves to 1.28. Finally, it is concluded that the equally extended EJH presents well performance compared to gradually increasing and decreasing EJH.

Comparative analysis of cross flow and jet impingement techniques of heat sink in electronics cooling

New and advanced technologies lead to the miniaturization of electronic devices with high energy densities. Though this is commendable progress in electronic technology, cooling these systems has become arduous due to the high heat flux generation from these devices. Traditional cooling systems are lagging due to these challenges, which brings up the demand for novel cooling techniques for this purpose. This research paper focused on the comparison of cross flow and jet impingement cooling techniques used in the heat sink, the peak temperature raised and the pressure drop across the heat sink is reported. The computational Fluid Dynamics (CFD) technique is used to investigate the flow and heat transfer characteristics. Among the cases studied, it is identified that the cross-flow shows superior thermal attributes as compared to the jet impingement method, due to which the base temperatures of pin fins in the cross-flow is noticed an average of 14.5° C lower than that of jet impingement.

Jet impingement in a V-rib roughened solar air heater: an experimental approach

ABSTRACT The present research article is an experimental investigation of an impinging jet solar air heater with V-patterned ribs on a modified absorber plate. The study attempts to combine active-passive jet impingement techniques focusing on varying jet parameters and variation in the arrangement of the V pattern. The experimental trials are conducted by varying parameters as follows: streamwise pitch ratio of circular jets X s t / D h d from 0.35 to 0.50, the span-wise pitch ratio of circular jets Y s p / D h d from 0.79 to 0.94, and width ratio of V-patterned ribs w/W from 1 to 6. The geometrical parameter is kept constant, viz. angle of attack (α) = 60°, pitch ratio P/e = 10, and rib height ratio e / D h d =0.043. The range for Reynolds number is kept between 4000 and 16,600, and solar insolation was 1000 W/m2. The results indicated that jet impingement on the ribbed absorber plate enhances thermal and thermohydraulic efficiencies. The maximum reported Thermal-Hydraulic Performance in the present study was 3.301.

Novel Method to Improve Heat Transfer Rate Through Delta Swirl Tape for a Swirl Jet Impingement Study

With advancement of electronic equipment’s, there is a need to have an efficient method or mechanism that helps remove heat from the system. Air jet impingement is generally implied method for effective heat removal from these equipment’s. There are several types of air jet impingement techniques used and among them swirl air jet is one of most prominent and proven method. In this study, a novel method is proposed to improve heat transfer of a swirling air jet impingement. Experimental study has been performed with swirl tape and novel delta tape having twist ratio (T.R) = 2 for jet to plate distance of z/d=2 to 8 and Re varying between 1500 to 9000. This study is basically carried out to improve the heat transfer at low Re conditions. Thermal imaging technique is used to derive centerline Nu values for different jet to plate distances (z/d=2 to 8). Study shows that novel delta tape adds significant improvement in heat transfer for above mentioned conditions.

Experimental investigation of thermo-hydraulic efficiency and performance characteristics of an impinging jet-finned type solar air heater

The current experimental study aimed to assess the overall performance of a sustainable design solar air heater (SAH). The investigated design comprise of mutual combination of jet impingement technique and application of fins. The array of longitudinal and continuos fins extends the rear side of the absorber and just below to it a jet plate is also encapsulated which consist of inline pattern of holes. For experimentation and testing natural climatic conditions were considered under specific range of design parameters enlisted in Table.1. The influence of the listed parameters is investigated on effective efficiency, outlet air temperature and friction factor respectively. The results are compared with the similar literature available. The outlet air temperature is enhanced while increasing the solar intensity values in comparison to the smooth duct. The maximum effective efficiency obtained is 82.5% for X/Dh = 0.46 respectively. With an increase in the values of Re friction factor decreases and the maximum friction factor has been observed at stream wise pitch ratio of 0.46, jet diameter ratio of 0.046 and least fin spacing of 0.23 yields low values of friction factor. The maximum efficiency in case of impinging jet with fins type design (IJWFSAH) obtained is 84% with 6% and 16% enhancement as compared to simple impinging (IJSAH) and smooth configuration. On the basis of comparative analysis between the theoretical and experimental results of thermal efficiency for IJSAH and IJWFSAH. An average deviation of ± 2% for (Re < 9000) and ± 2.2–3% for (Re > 9000) has been reported for IJWFSAH. The average deviation noted for IJSAH is ± 1.5% for (Re < 9000) and ± 2–3% for (Re > 9000) respectively. The data of comparative analysis shows a good agreement between the experimentally evaluated and theoretically calculated values.

CFD Simulation of Showerhead Jet Impingement at Leading Edge of a Gas Turbine Blade

The performance of gas turbine improves with increase of turbine inlet temperature and leading edge of the turbine blades are subjected to the highest temperatures. To decrease the temperature, jet impingement technique is used for the leading-edge blade cooling. In this present study, showerhead arrangement is used for the jet impingement cooling. This showerhead arrangement consists of a central jet and it is surrounded by four jets resembling a shower. As the area/region of influence in the showerhead arrangement is hemi-spherical, an improved heat transfer is expected. The cross-section of the jet impinging holes is circular. The study is carried out by varying the Reynolds number from 11000 to 50000 for a jet impinging length of R/2. Steady-state simulations are carried out using commercial CFD code, ANSYS Fluent and turbulence model used is kω-SST. Wall temperature distribution decreases with increase in Reynolds numbers and it is observed to be minimal at the jet impingement point (i.e., stagnation point). Wall temperature distribution of the showerhead arrangement with straight impingement tubes is lesser compared to showerhead arrangement with bended impingement tubes. Mixing of jets prior to impingement on the wall is visualized for showerhead arrangement with bended impingement tubes leading to ineffective cooling for this arrangement. Nusselt number of the showerhead arrangement with straight impingement tubes are higher compared to showerhead arrangement with bended impingement tubes indicating better convective heat transfer.

Jet-impinged based solar air heating system: An overview of flow dynamics and heat transfer phenomena

Solar-air Heater (S-AH) is the simplest device that helps in converting solar-energy to heat and the extracted heat can either be used for heating space, or drying crops, etc. In the present investigation, the jet-impingement technique is employed and the effect of relative-jet diameter is analysed on the performance of S-AH. A commercial software is used to simulate the S-AH with a jet which strikes at the centre of the absorber plate (with uniform heat-flux) and the problem is modelled on a two-dimensional computational domain under steady state using a finite volume method. The relative-jet diameter is a non-dimensionalized parameter which is defined as the ratio of jet-diameter to the hydraulic diameter of the passage, and it is varied from 0.25 to 0.75 in three sets. In comparison to simple solar air heaters, the considerable increase in Nusselt number is obtained. The best performance obtained for a solar air heater with a relative jet-diameter of 0.5 which is approximately 207% higher than the simple one.

Heat Transfer Augmentation through Different Jet Impingement Techniques: A State-of-the-Art Review

Jet impingement is considered to be an effective technique to enhance the heat transfer rate, and it finds many applications in the scientific and industrial horizons. The objective of this paper is to summarize heat transfer enhancement through different jet impingement methods and provide a platform for identifying the scope for future work. This study reviews various experimental and numerical studies of jet impingement methods for thermal-hydraulic improvement of heat transfer surfaces. The jet impingement methods considered in the present work include shapes of the target surface, the jet/nozzle–target surface distance, extended jet holes, nanofluids, and the use of phase change materials (PCMs). The present work also includes both single-jet and multiple-jet impingement studies for different industrial applications.

Numerical investigation of heat transfer and flow characteristics of a double-wall cooling structure: Reverse circular jet impingement

• The reverse jet impingement is shown to be more resistant to the crossflow effect. • The extended nozzles minimize the crossflow effect. • Increasing the internal heat transfer surface area improves the total heat transfer rate. • To maximise Nu, optimum nozzle-to-target spacing is around 3 jet diameter. Double-wall cooling structures are commonly used to enhance the heat transfer in combustor liner and aerofoil internal cooling within gas turbine engines and other industrial applications. This is the first study to adopt a novel reverse jet impingement technique into a double-wall cooling structure in order to achieve a higher heat transfer rate with relatively lower pressure drop. This paper uses the computational fluid dynamics to study crossflow, nozzle configuration, inlet orientation, and jet-to-target spacing distance effects on the heat transfer rate and the discharge coefficient. In this study, jet-to-target spacing was varied from 1.6 to 7 jet diameter, jet-to-jet spacing was 3.4 jet diameter, the reverse tube diameter was 3.2 jet diameter, and jet Reynolds number was set at 23,000. Procedural optimisation throughout the study initially evaluated that nozzles extended through the crossflow channel are more effective than the square-edged nozzles in eliminating the crossflow effect and promoting higher heat transfer. Variation of inlet condition yielded no significant optimisation was found. Jet-to-target spacing was optimised at jet-to-target spacing around 3 jet diameter. The most significant variable affecting nozzle discharge coefficient was the flow area of the outlet. The reverse jet impingement design showed capacity to enhance heat transfer by increasing the internal surface area, and minimise negative crossflow effects, without excessive reduction in the discharge coefficient.

Numerical optimization of pulse frequency and heat transfer for a subsonic impinging jet array

Jet impingement technique with pulsed jet arrays has proved to be one of the most efficient heat transfer technologies for cooling applications. Detailed investigations are required to optimize the different parameters to achieve maximum heat transfer. Present study is an effort in this direction by analyzing the heat transfer from a flat heating film of dimension 60 × 60 × 0.1 mm. The chip generates a heat of 30 W which is to be carried away by means of air jets. The nozzle plate at the top generating the air jet has a set of 9 nozzles arranged in a 3x3 inline configuration. Two sides of the flow arrangement are confined and flow is only along one direction. The nozzle diameter is 5 mm and pitch length from center to center X/D and Y/D are 3. The nozzle plate, heating plate gap Z/D is 4. The Reynolds number values are in the range 3500 to 14000. The cross-flow approaches in a direction perpendicular to the jets and mixes with the jet flow. The results obtained predict a dominance of pulsed jets over steady jets, if heat transfer is considered. Among pulsed jets, those with higher amplitudes and lower frequencies showcase better heat transfer and more uniform distribution throughout the heated plate.

Influence of Photodynamic Therapy on Bacterial Attachment to Titanium Surface.

In periodontitis and peri-implantitis, plaque-forming microorganisms develop biofilms in which the microbes become protected from washing and antibiotics. While the antibiotics often become partially ineffective and traditional scaling to implant surface becomes challenging on such biofilm, Photodynamic Therapy (PDT) can be a useful option against these protected microorganisms. In this investigation, a unique combination of PDT and water rinsing force representing physical removal (using jet impingement techniques) were applied to biofilms of Streptococcus mutans (ATCC strain 27351) grown on commercially pure titanium (Ti). The experiment examined the force required to detach a biofilm (shear stress) as a way to determine changes in the biofilm's attachment strength after applying PDT. Colony-forming-unit (CFU) counts and Alamar Blue (A.B.) assays were used to measure the vitality and metabolism of the bacteria before and after the treatment. Multiple Attenuated Internal Reflection Infrared (MAIR-IR) spectra of identical biofilms grown on germanium prisms having surface properties similar to those of Ti were used to test differences in biofilm removal susceptibility. Using independent samples t-test, PDT-treated biofilms were significantly (p<0.05) more susceptible to removal from their substrata by water-jet impingement forces in comparison to the untreated biofilms. Varying thicknesses of untreated control biofilms required more shear stress (144 and 228 dynes/cm²) to delaminate from titanium surfaces when compared to less shear stress (90 to 140 dynes/cm²) required to removed PDT-treated companion biofilms. Moreover, an exopolymer matrix of polysaccharide (P.S.s) within layers of biofilm required less shear stress when compared to the force needed to detach biofilm from substrata. However, also needing further less force for treated biofilm (between 39 and 51 dynes/cm²) and (57 and 68 dynes/cm²) for PDT treated and control, respectively. Multiple Attenuated Internal Reflection Infrared (MAIR-IR) results confirmed the superiority of PDT-induced removal, predominantly of the protective polysaccharide part of the biofilm. These results suggest that PDT can weaken biofilms at different levels of maturity, allowing easier detachment using simple rinsing forces, which has promising future application in the dental practice where traditional scaling of implant surfaces is challenging.