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This paper aims to provide improvements to the newest version of the k‐ ω turbulence model of Wilcox for convective heat transfer prediction in turbulent axisymmetric jets impinging onto a flat plate.

Improvements to the heat transfer prediction in the impingement zone are obtained using the stagnation flow parameter of Goldberg and the vortex stretching parameter of Wilcox. The third invariant of the strain rate tensor in the form of Shih et al. and the blending function of Menter are applied in order make negligible the influence of the impingement modifications in the benchmark flows for turbulence models. Further, it is demonstrated that for two‐dimensional jets impinging onto a flat plate the stagnation region Nusselt number predicted by the original k‐ ω model is in good agreement with direct numerical simulation (DNS) and experimental data. Also for two‐dimensional jets, the proposed modification is deactivated.

The proposed modification has been applied to improve the convective heat transfer predictions in the stagnation flow regions of axisymmetric jets impinging onto a flat plate with nozzle‐plate distances H/D = 2, 6, 10 and Reynolds numbers Re = 23,000 and 70,000. Comparison of the predicted and experimental mean and fluctuating velocity profiles is performed. The heat transfer rates along a flat plate are compared to experimental data. Significant improvements are obtained with respect to the original k‐ ω model.

The proposed modification is simple and can be added to the k‐ ω model without causing stability problems in the computations.

The purpose of this paper is to examine entropy generation rate in the flow and temperature field due pulsed impinging jet on to a flat plate. Heat transfer of pulsed impinging jets has been investigated by many researchers. Entropy generation is one of the parameters related to the second law of thermodynamics which must be analyzed in processes with heat transfer and fluid flow in order to design efficient systems. Effect of velocity profile parameters and various nozzle to plate distances on viscous and thermal entropy generation are investigated.

In this study, the flow and temperature field of a pulsed turbulent impinging jet are simulated numerically by the finite volume method with appropriate boundary conditions. Then, flow and temperature results are used to calculate the rate of entropy generation due to heat transfer and viscous dissipation.

Results show that maximum viscous and thermal entropy generation occurs in the lowest nozzle to plate distance and entropy generation decreases as the nozzle to plate distance increases. Entropy generation in the two early phase of a period in the most frequencies is more than steady state whereas a completely opposite behavior happens in the two latter phase. Increase in the pulsation frequency and amplitude leads to enhancement in entropy generation because of larger temperature and velocity gradients. This phenomenon appears second and even third peaks in entropy generation plots in higher pulsation frequency and amplitude.

The predictions may be extended to include various pulsation signal shape, multiple jet configuration, the radiation effect and phase difference between jets.

The results of this paper are a valuable source of information for active control of transport phenomena in impinging jet configurations which is used in different industrial applications such as cooling, heating and drying processes.

In this paper the entropy generation of pulsed impinging jet was studied for the first time and a comprehensive discussion on numerical results is provided.

Impinging jets have been widely studied, and the addition of swirl has been found to be beneficial to heat transfer. As there is no literature on Reynolds-averaged Navier Stokes equations (RANS) nor experimental data of swirling jet flows generated by a rotating pipe, the purpose of this study is to fill such gap by providing results on the performance of this type of design.

As the flow has a different behaviour at different parts of the design, the same turbulent model cannot be used for the full domain. To overcome this complexity, the simulation is split into two coupled stages. This is an alternative to use the costly Reynold stress model (RSM) for the rotating pipe simulation and the SST k-ω model for the impingement.

The addition of swirl by means of a rotating pipe with a swirl intensity ranging from 0 up to 0.5 affects the velocity profiles, but has no remarkable effect on the spreading angle. The heat transfer is increased with respect to a non-swirling flow only at short nozzle-to-plate distances H/D < 6, where H is the distance and D is the diameter of the pipe. For the impinging zone, the highest average heat transfer is achieved at H/D = 5 with swirl intensity S = 0.5. This is the highest swirl studied in this work.

High-fidelity simulations or experimental analysis may provide reliable data for higher swirl intensities, which are not covered in this work.

This two-step approach and the data provided is of interest to other related investigations (e.g. using arrays of jets or other surfaces than flat plates).

This paper is the first of its kind RANS simulation of the heat transfer from a flat plate to a swirling impinging jet flow issuing from a rotating pipe. An extensive study of these computational fluid dynamics (CFD) simulations has been carried out with the emphasis of splitting the large domain into two parts to facilitate the use of different turbulent models and periodic boundary conditions for the flow confined in the pipe.

The purpose of this study is to do a numerical analysis of the jet to a body filled with phase change material (PCM). The melting of the PCM filled body was investigated by the hot jet flow. Four different values of the Reynolds number were taken, ranging from 5 × 103 = Re = 12.5 103. Water, Al₂O₃ 1%, Al₂O₃ 2% and hybrid nanofluid (HNF; Al₂O₃–Ag mixture) were used as fluid types and the effects of fluid type on melting were investigated. At 60 °C, the jet stream was impinged on the PCM filled body at different Reynolds numbers.

Two-dimensional analysis of melting of PCM inserted A block via impinging turbulent slot jet is numerically studied. Governing equations for turbulent flow are solved by using the finite element method via analysis and system fluent R2020.

The obtained results showed that the best melting occurred when the Reynolds number increased and the HNF was used. However, the impacts of using alumina-water nanofluid were slight. At Re = 12,500, phase completion time was reduced by about 13.77% when HNF was used while this was only 3.93% with water + alumina nanofluid as compared to using only water at Re = 5,000. In future studies, HNF concentrations will change the type of nanoenhanced PCMs. In addition, the geometry and jet parameters of the PCM-filled cube can be changed.

Effects of impinging jet onto PCM filled block and control of melting via impinging hot jet of PCM. Thus, novelty of the work is to control of melting in a block by impinging hot jet and nanoparticles.

A numerical scheme that has already proved to be efficient and accurate for laminar heat transfer is extended for turbulent, axisymmetric heat transfer calculations. The extended scheme is applied to the steady‐state heat transfer of axisymmetric turbulent jets, impinging onto a flat plate. Firstly, the low‐Reynolds version of the standard k‐ε model is employed. As is well known, the classical k‐ε turbulence model fails to predict the heat transfer of impinging jets adequately. A non‐linear k‐ε model, with improved ε‐equation, yields much better results. The numerical treatment of the higher order terms in this model is described. The effect on the heat transfer predictions of a variable turbulent Prandtl number is shown to be small. It is also verified that the energy equation can be simplified, without affecting the results. Results are presented for the flow field and the local Nusselt number profiles on the plate for impinging jets with different distances between the pipe exit and the flat plate.

A numerical investigation to determine the velocity and heat transfer characteristics of multiple impinging slot jets in rib‐roughened channels in the presence of cross‐flow has been carried out. Fluid flow is modeled using an explicit algebraic stress model. A simple eddy diffusivity and a generalized gradient diffusion hypothesis are applied for the modeling of turbulent heat fluxes. The computations are validated against available experimental fluid flow and heat transfer data. Different size and arrangement of jets and ribs are considered in detail, while the Reynolds numbers of a jet and the channel inlet are fixed at 6,000 and 14,000, respectively. Results show that the ratio (B/W) between the size of the jets and ribs is most important. An explanation is that the ribs inhibit the motion of eddies by preventing them from coming very close to the surface when B/W is low, e.g. B/W = 1, although the ribs will increase the turbulence intensity. This blockage limited the heat transfer enhancement effect of the ribs and impinging jets.

Jet impingement onto surface finds wide application in industry. In laser processing an assisting gas jet is introduced either to shield the surface from oxidation reactions or initiating exothermic reaction to increase energy in the region irradiated by a laser beam. When an impinging gas jet is used for a shielding purpose, the gas jet enhances the convective cooling of the cavity surface. The convective cooling of the laser formed cavity surface can be simulated through jet impingement onto a cavity with elevated wall temperatures. In the present study, gas impingement onto a slot is considered. The wall temperature of the cavity is kept at elevated temperature similar to the melting temperature of the substrate material. A control volume approach is used to simulate the flow and temperature fields. The Reynolds Stress Turbulence model (RSTM) is employed to account for the turbulence. To examine the effect of cavity depth on the heat transfer characteristics, the depth is varied while keeping the cavity width constant. It is found that impinging jet penetrates into a cavity, which in turn, results in a stagnation region extending into the cavity. An impinging gas jet has considerable effect on the Nusselt number along the side walls of the cavity while the Nusselt number monotonically changes with varying cavity depth.

A direct numerical simulation code with cylindrical geometry has been developed. A direct numerical simulation (DNS) of an impinging round jet into parallel disks is performed for a Reynolds number of 10,000 based on the nozzle exit velocity and the nozzle diameter (D). Mean flow variables, turbulent intensity, pressure distribution and turbulent kinetic energy budgets are obtained at various radial locations. The present DNS results are in fairly good agreement with the two‐dimensional PTV measurements by Nishino and co‐workers in 1996. Some flow features of this impinging round jet regarding a turbulent transition process are discussed.

The purpose of this study is to make a numerical analysis of a wall jet with a moving wall attached with a heated body. The hot body is cooled via impinging wall jet. Thus, a jet cooling problem is modeled. The Reynolds number is taken in three different values between 5 × 10³ ≤ Re ≤ 15 × 10³. The h/H ratio for each value of the Re number was taken as 0.02, 0.04 and 0.0, respectively.

Two-dimensional impinged wall jet problem onto a moving body on a conveyor is numerically studied. The heated body is inserted onto an adiabatic moving wall, and it moves in +x direction with the wall. Governing equations for turbulent flow are solved by using the finite element method via analysis and system Fluent R2020. A dynamic mesh was produced to simulate the moving hot body.

The obtained results showed that the heat transfer (HT) is decreased with distance between the jet outlet and the jet inlet. The best HT occurred for the parameters of h/H = 0.02 and Re = 15 × 10³. Also, HT can be controlled by changing the h/H ratio as a passive method.

Originality of this work is to make an analysis of turbulent flow and heat transfer for wall jet impinging onto a moving heated body.

This study aims to focus on the surface curvature, jet to target spacing and jet Reynolds number effects on the heat transfer and fluid flow characteristics of a slot jet impinging on a confined concave target surface at constant jet to target spacing.

Numerical simulations are used in this research. Jet to target spacing, H/B is varying from 1.0 to 2.2, B is the slot width. The jet Reynolds number, Rej, varies from 8,000 to 40,000, and the surface curvature, R2/B, varies from 4 to 20. Results of the target surface heat transfer, flow parameters and fluid flow in the concave channel are performed.

It is found that an obvious backflow occurs near the upper wall. Both the local and averaged Nusselt numbers considered in the defined region respond positively to the Rej. The surface curvature plays a positive role in increasing the averaged Nusselt number for smaller surface curvature (4-15) but affects little as the surface curvature is large enough (> 15). The thermal performance is larger for smaller surface curvature and changes little as the surface curvature is larger than 15. The jet to target spacing shows a negative effect in heat transfer enhancement and thermal performance.

The surface curvature effects are conducted by verifying the concave surface with constant jet size. The flow characteristics are first obtained for the confined impingement cases. Then confined and unconfined slot jet impingements are compared. An ineffective point for surface curvature effects on heat transfer and thermal performance is obtained.