Wall Jet Region Research Articles

Flow and Heat Transfer Characteristics of Swirling Impinging Micro-Slot Jets by Adopting Circular Ribs in the Wall Jet Region

The flow and heat transfer behaviors of swirling impinging micro-slot jets using circular ribs in the wall jet region have been numerically studied. In this study, the total spiraling length was defined as 290 mm due to the two complete revolutions of the helix generated at a slot nozzle thickness of 1.0 mm. The range of circular rib radius ratios varied from 1 to 4 under the jet-to-target spacing ratio at 2 and 4. Predictions were made using the turbulent kinetic energy-epsilon model at Reynolds numbers ranging from 5000 to 20000. The results showed that the heat transfer enhancement on the target wall depended on the circular rib radius ratios. The jet flow at a low circular rib radius ratio generated recirculating ambient fluid behind the rib zone and a minuscule vortex within a circular rib region. At a high ratio, the jet’s potential flow directly affected the top rib surface and generated secondary flows in the circular rib. The heat transfer rate tended to increase as the Reynolds number increased. The average heat transfer value at a circular rib radius ratio of 3 became the best, up to 18.1% for jet-to-target spacing of 2. Whereas above 14.8% average value at a circular rib radius ratio of 1 in the case of jet-to-target spacing of 4 gained the highest.

Flow and heat transfer behavior of acoustically excited pulsating air jet impinging on a flat surface

Experiments are carried out to understand the flow and thermal behavior of a pulsating jet. The pulsating jet is generated using acoustic excitation. The study considered variations in Reynolds number (Re = 2800, 4900, and 6800), Strouhal number (St = 0–0.84), pulsation amplitude (A = 0–60 %), and nozzle-to-surface distance (z/d = 1–8). Findings revealed that the potential core length of the pulsating jet is shorter compared to the steady jet. The potential core length initially decreases with an increase in St up to 0.42, then begins to increase. Pulsating jets improve thermal performance in the wall jet region due to greater entrainment and mixing from the surrounding fluid. Results demonstrated that pulsating jets could increase average heat transfer rate by up to 58 % at Re = 2800 compared to the steady jet. Although heat transfer rates are higher in pulsating jets, changes in pulsation frequency or amplitude had a minimal effect. The enhancement in average heat transfer rate diminishes as the Reynolds number increases for the same Strouhal number. Each tested Reynolds number showed at least a 10 % improvement in heat transfer in pulsating jet over steady jet. The improved thermal performance of the acoustically pulsating chamber offers the potential for enhanced thermal management in various applications.

Jet array impingement heat transfer in a rectangular cavity with effusion holes

Various researchers have studied jet array impingement heat transfer in impingement/effusion cooling systems. However, there is a lack of research on impingement/effusion cooling systems installed within rectangular cavities that focus on the impact of the proximity of the jet hole to the cavity sidewalls on cooling performance. The main objective of this study is to investigate the flow and heat transfer characteristics of jet array impingement with effusion holes in a rectangular cavity, considering various spacings between the cavity sidewalls and the outermost jet hole. The design parameters in this study include the ratio of the jet hole pitch to jet hole diameter of 7.1, 10.0, and 16.7, and the ratio of the distance between the jet and impingement plates to jet hole diameter of 2, 6, and 10, with the Reynolds number based on the jet hole diameter ranging from 2500 to 15,000. Heat transfer characteristics in the stagnation region and wall jet region were examined using local Nusselt number distributions on the impingement surface, measured by liquid crystal thermography. The local Nusselt number was high in the stagnation region and decreased radially from the stagnation region as the wall jet region formed. The closer the outermost jet hole is to the sidewall, the higher the Nusselt number on the impingement surface near the sidewall. Moreover, the flow structure in the rectangular cavity was numerically investigated, and the velocity vectors and streamlines showed that primary and secondary vortices were generated in the middle of two neighboring jets and near the sidewall, respectively. This study also assessed previous average Nusselt number correlations. Based on experimentally determined average Nusselt number data with 54 center unit cells and 1296 side unit cells, new correlations to predict the average Nusselt number on the impingement surface in a rectangular cavity with effusion holes were developed.

Theory and Experiment of the Limiting Current in Impinging Jet Electrodes

Recently, flow cells with a confined impinging jet type have emerged as a promising hydrodynamic electrochemical setup for non-conventional square model electrodes that cannot be measured in the commonly used rotating disk electrode (RDE) setup1. Due to the complex hydrodynamic flow profiles, these flow cell types usually rely on computational fluid dynamics (CFD) simulations for the description of the local current density profiles and overall current-potential characteristics2. In this work, we present an advanced analytical model of the limiting current in confined impinging jet electrodes and validate the model with experimental data and corresponding CFD simulations.Around 350 parameter sets of the confined impinging jet electrode arrangement were analyzed by varying the inlet diameter (d), distance between inlet-nozzle and electrode (H), electrode radius (RIII), and volume flow rate (V0). Figure 1 shows the proposed analytical solution which separates the electrode into three different diffusion regions: (i) wall-tube region (blue rectangle), (ii) wall-jet region (green rectangle), and finally (iii) radial channel-flow region (orange rectangle). The approach allows predicting the limiting current characteristics for a broad variety of impinging jet electrodes, including the confined impinging jet electrode type. The flow line profiles obtained by CFD simulations are in excellent agreement with the analytically determined regimes with radii RI and RII and flow regime transitions. Very importantly, for the construction of ideal wall-tube electrodes the transition point RI can now be described by our analytical model in high accuracy and requires no more in-depth numerical or experimental studies3. We determined an average relative error over all parameter points compared to the numerical CFD simulations to be 7.8 %. In contrast, the analytical formula for free wall-jets4 to the entire electrode is in the range of 29 %. Furthermore, using a 3D-printed flow cell geometry (H = 0.7 mm; d = 0.5 mm) with the confined impinging jet type, the obtained experimental data confirm the here developed analytical model. The experimental data for different electrode radii (1 mm < R < 3 mm) using the ferrocyanide/ferricyanide redox pair ([Fe(CN)6]4-/[Fe(CN)6]3-) also show good agreement to the analytical model with an average deviation of 6 %.In summary, we have developed an analytical model that allows an accurate prediction of the limiting current for different geometries of the impinging jet electrode. Based on numerical and experimental approaches, our model shows an accuracy of below 10 %, which is very remarkable compared to the current models reported in the literature. The results of this study help to improve the design and construction of electrochemical flow cells based on this electrode type as an alternative to the classic RDE setup.

Optical Temperature Field Measurements With Two-Color Laser Induced Fluorescence In A Stratified Thermal Energy Storage

Thermal energy storage systems (TES) are an important part for storing surplus electric energy from renewable, volatile energy sources. TES using liquid storage materials operate most efficiently by stratifying the storage fluid based on its thermal density gradient into a hot and cold layer, separated by a thermocline region. Previous studies of such stratified TES have shown that heat conduction from the hot, upper layer to the cold, lower layer through the storage tank wall induces counter-directed convective flows (wall jets) along the inner walls. These wall jets carry hot fluid from the upper layer and cold fluid from the lower layer towards the thermocline region, which leads to mixing of the layers and therefore to a decreased thermal efficiency. To quantify the influence of the wall jets on the mixing process, optical temperature field measurements in the thermocline region of a 105 L stratified TES model experiment are performed with two-color planar laser induced fluorescence (2C-PLIF). The results show that the method is feasible for evaluating the thermocline temperature distribution over time in such a system with an accuracy of 1.5 °C. Further measurements in the hot wall jet region show that the temperature resolution of the measurement system limits the evaluation of the thermal boundary layers. However, the 2C-PLIF system provides sufficient temperature field information to determine the local heat fluxes in future studies in combination with simultaneous PIV measurements.

Experimental investigation of metal foam embedded surface thermal characteristics using air-jet impingement with different orifice geometry

Experimental investigation of metal foam embedded surface thermal characteristics using air-jet impingement with different orifice geometry

Turbulent mean flow prediction in impinging jets using data assimilation methods

In this paper, a data-driven turbulence model is devised based on data assimilation (DA) for predicting impinging jet characteristics for various Reynolds numbers and nozzle-to-plate distances. The shear stress transport (SST) model with Tam–Thies correction is applied. The SST model with the X term makes accurate predictions in the region of wall jet near the overlying stationary fluid but fails to predict the velocity distribution near the wall. The DA-optimized SST model with the X term is used for predicting the impinging jet to minimize the deviation between the model prediction and experimental data. Only the model constants corresponding to the region near the wall are optimized through DA. The model constants at H/D = 2, 3, and 6 are fitted using logarithmic curves with respect to the nozzle-to-plate distance to obtain a universal formulation for predicting the impinging jet under various flow conditions. The model using the fitted model constants, referred to as the SST-H/D model, accurately predicts the mean flow for different nozzle-to-plate distances, nozzle types, and Reynolds numbers.

Flow characteristics in a semi-confined circular-pipe impinging jet

The impinging jet is a complex heat and mass transfer technique that involves several process variables, such as the jet Reynolds number, impingement distance, and jet configuration. In this study, the flow characteristics of a semi-confined circular-pipe impinging jet over different Reynolds numbers and impingement distances were experimentally investigated using a two-dimensional particle image velocimetry technique. The confinement was achieved by positioning a plate parallel to the impinging plate at the nozzle exit. The time-averaged velocity field exhibited a recirculation structure that gradually shifted downstream with increasing Reynolds numbers or impingement distances. Notably, at H/d = 2, this downstream shift of the structure was accompanied by an increase in the vortex intensity. Moreover, the confined plate induced alterations in the overall flow pattern within the confined region, significantly reducing the wall jet decay rate compared with both unconfined and confined radial wall jets for H/d ≥ 3. Conversely, the confinement did not affect the expansion of the wall jet. Unlike the free (unconfined) impinging jets, the semi-confined circular-pipe impinging jet did not exhibit self-similar behavior in the conventional outer-scaled coordinates, particularly concerning the turbulence intensity and Reynolds shear stress. Finally, self-similarity in the time-averaged velocity and various turbulence parameters was achieved using the parameter scale proposed in this study, thereby obtaining the corresponding scaling laws in the wall jet region. Our study results can deepen the current understanding of the flow characteristics of semi-confined circular-pipe impinging jets and are significant for optimizing the performance and efficiency of compact electronic packaging equipment.

Experimental study of the Reynolds stress distribution and its self-similarity in a semi-confined impinging jet

This paper investigates the Reynolds stress distribution and its self-similarity of a semi-confined impinging jet using the two-dimensional particle image velocimetry (2D-PIV) technology. The confinement is achieved by placing a plate parallel to the impinging plate at the nozzle exit. Nine sets of measurements are conducted at three impingement distances (4, 5, and 6 times the nozzle diameter) and three Reynolds numbers (5084, 8179, and 13,926). The spatial distribution and the self-similarity of Reynolds stresses are obtained. The results indicate that high turbulence occurs mainly in the free jet shear layer and the wall jet shear layer. The variation of Reynolds stresses with impingement distances and Reynolds numbers are determined. The Reynolds stresses in the radial wall jet region do not exhibit self-similarity in the outer-scaled coordinates. Scaling parameters based on Reynolds stresses are proposed, and the Reynolds stress velocity scales decay by a power-law function in the self-similar region, while the Reynolds stress length scales increase linearly. The Reynolds stresses in the radial wall jet region show extremely strong self-similarity using the Reynolds stress scaling parameters normalization. Finally, the corresponding scaling laws for Reynolds stresses are obtained.

Flow and acoustics in a model rocket flame deflector and deflector cover

The design of a rocket launch environment is a complex process with many different aspects that are highly interconnected. Acoustics, which is one of these, should be investigated in detail due to possible devastating effects on the launch vehicle, crew, and launch environment. This study uses a numerical method to consider a passive noise reduction method applied to a supersonic jet impinging on an inclined flame deflector to decrease the acoustic loads on the launch vehicle and noise levels in the far-field. In a supersonic jet impinging on an inclined flat plate configuration, acoustic waves that travel upstream originate from the impingement and wall jet regions. These upstream traveling waves are a combination of the acoustic waves that are produced by the high speed jet flows in the wall jet region and acoustic waves that reflect from the impingement wall. Due to the inclination of the impingement plate, these waves either travel to the far-field in the upstream direction or travel towards the free-jet region interacting with the high speed flow near the nozzle lip. This interaction can create a self sustaining feedback loop, which can cause acoustic tones to appear in the near- and far-field spectra. It is the aim of the present study to block the upstream traveling waves by introducing a second inclined wall with a circular cut-out between the nozzle exit and the impingement plate. Different configurations with different wall locations and cut-out sizes are investigated using a Detached Eddy Simulation CFD solver and an acoustic solver that is based on the Ffowcs Williams and Hawkings analogy. The mechanisms for the establishment of the feedback loops are examined.

Analysis of the quenching behavior in impinging flame: Flow and thermal characteristics

Considering the complex phenomenon of in-cylinder flame impingement occurring in internal combustion engines, flame-wall interaction in different impinging distance cases is presented for the non-premixed impinging flames. In this article, the quenching mechanism of impinging flame is focused on using experiments and numerical simulations. The quenching information on the flow and thermal field is obtained in the experiment. Large Eddy simulation is used to provide the details in the flow characteristics. In the wall jet region, multiple vortexes are formed accompanied by strong turbulence and large wall shear stress, which becomes more significant with the increase of the impinging distance. The low-temperature region corresponds to a large wall heat flux and Nusselt number, and this non-positive correspondence between temperature and heat transfer leads to excessive heat loss and weakens the flame stability. The quenching behavior in the impinging flame is analyzed in terms of the flow field and thermal characteristics.

Experimental investigation on time-averaged heat transfer characteristics of a row of pulsating jets

The heat transfer characteristics of a row of pulsating jets feeding by a cooling tube have been investigated for an active clearance control system. Experimental tests were performed to explore the effects of the frequency (rectangular signal, 5–30 Hz), Reynolds number (6000–20,000), jet-to-surface spacing ratio (6–10), and jet-to-jet spacing ratio (3–9) on the Nusselt number of the pulsating jets and the relative enhancement coefficient compared with the steady jets. Results show that the streamwise-averaged Nusselt number of the pulsating jets increases with the increase of frequency (5–25 Hz) and Re. Its distribution along the X/d is gentler with the increase of H/d and S/d. Heat transfer correlations are developed and two associated parameters SrRe0.911(H/S)0.348 and SrRe(H/d)0.540(S/d)-0.248 are obtained to effectively scale the enhancements. Maximum enhancements for the stagnation region and wall jet region are 29.3% and 26.8%, respectively. The heat transfer on the overall surface can be strengthened in a wider range of conditions compared with the stagnation region, which contributes to the heat transfer uniformity in certain conditions.

An experimental investigation on the isoenergetic supersonic cooling films subjected to different ratios of static pressure

Ratio of static pressure (RSP) is a critical factor affecting the development of supersonic cooling film flow field. To give a good account of flow characteristics and physical mechanisms on the influences of RSPs, experiments are conducted employing the nanoparticle planar laser scattering (NPLS) and particle-image velocimetry (PIV) techniques. A supersonic cooling film is tangentially injected at a Mach number of Maj=2 into a laminar boundary layer at a mainstream Mach number of Ma∞=3 with different RSP cases. The flow field is divided into four sections: the wake region, the potential core region, the wall-jet region, and the fully developed turbulent boundary layer region. The velocity profile extracted at the fully developed turbulent boundary layer region is proved to be consistent with the theoretical composite profile. Moreover, a new criterion that distinguishes the specific position of the impingement point where the mixing layer approaches the bottom boundary layer is proposed based on the distribution of principal strain rate of the mean velocity field. The analysis of turbulent structures finds that the K–H vortex structures are sensitive to RSPs, and more broken vortices generated when the two fluids mix. The intensity of wave structures is depicted in the synthetic schlieren images when subjected to different RSPs. In addition, the turbulent characteristics show a weaker mixing process with increased RSP, indicating a prolonging in the effective cooling length. Furthermore, the disturbance at the slot and variations of velocity gradient downstream are addressed and analyzed to reveal the physical mechanisms for the mixing process on RSP differences.

Heat transfer investigation on under-expanded supersonic impinging jets

In this study, wall-resolved large-eddy simulations are performed to investigate the underpinning physics of impingement heat transfer in under-expanded supersonic impinging jets. The jet is generated with an infinite-lipped nozzle of diameter D, has a nozzle-to-wall distance of 5D, a nozzle pressure ratio (NPR) of 3.4 and a Reynolds number of 6×104 based on the ideally-expanded jet velocity. Two thermal boundary conditions of a heated isothermal wall and an adiabatic wall for the impingement plate are considered.Both impinging jets in the current study feature a strong stand-off shock, which oscillates periodically in front of the impingement plate at two dominant frequencies. These oscillations result in two local peaks of the mean heat transfer coefficients with the first peak located in the stagnation region but shifted away from the stagnation point (i.e. jet axis), whilst the second peak is located in the wall jet region. The instantaneous fields of pressure, vorticity and Nusselt number are first discussed to study qualitatively the connection between these two peaks of the mean heat transfer coefficient and the near-wall flow structures. The characteristics of these two peaks are then analysed using the near-wall statistics and spectra of the pressure, axial velocity and Nusselt number distribution.It is found that the first peak of the Nusselt number forms as a consequence of the jet impingement of the non-periodic turbulent structures, whilst the second peak is linked to the reattachment of the recirculation bubble in the wall jet. It is shown that the unsteady separation and reattachment processes are strongly related to the oscillatory motion of the stand-off shock at the dominant frequencies. Last but not the least, the first local minimum close to the stagnation point is also found to be associated with the strong oscillatory behaviour of the stand-off shock.

Impingement heat transfer characteristics of nozzles with inclined exits

ABSTRACT The present study reports experimental investigations on jet impingement parameters such as nozzle shape, nozzle-plate spacing, Reynolds number, and effect of angle of cut for inclined nozzles on heat transfer. It is observed that the stagnation Nusselt number decreases with an increase in the angle of cut for inclined nozzles. Inclined nozzles produced a higher Nusselt number in the transition and wall jet region than reference nozzles. The radial velocity at the exit of the nozzle is higher for inclined nozzles toward the long lip. The turbulence intensity increases with an increase in nozzle exit angle.

The Wall-Jet Region of a Turbulent Jet Impinging on Smooth and Rough Plates

The study reports direct numerical simulations of a turbulent jet impinging onto smooth and rough surfaces at Reynolds number Re = 10,000 (based on the jet mean bulk velocity and diameter). Surface roughness is included in the simulations using an immersed boundary method. The deflection of the flow after jet impingement generates a radial wall-jet that develops parallel to the mean plate surface. The wall-jet is structured into an inner and an outer layer that, in the limit of infinite local Reynolds number, resemble a turbulent boundary layer and a free-shear flow. The investigation assesses the self-similar character of the mean radial velocity and Reynolds stresses profiles scaled by inner and outer layer units for varying size of the roughness topography. Namely the usual viscous units u_tau and delta _nu are used as inner layer scales, while the maximum radial velocity u_m and its wall-normal location z_m are used as outer layer scales. It is shown that the self-similarity of the mean radial velocity profiles scaled by outer layer units is marginally affected by the span of roughness topographies investigated, as outer layer velocity and length reference scales do not show a significantly modified behavior when surface roughness is considered. On the other hand, the mean radial velocity profiles scaled by inner layer units show a considerable scatter, as the roughness sub-layer determined by the considered roughness topographies extends up to the outer layer of the wall-jet. Nevertheless, the similar character of the velocity profiles appears to be conserved despite the profound impact of surface roughness.

Structure optimization and cooling performance of a heat sink with discontinuous arc protrusions impacted by nanofluid confined slot jet impingement

PurposeThe purpose of this paper is to improve the overall heat transfer performance and the temperature uniformity of the heat sink and to explore the effects of the jet Reynolds number and the nanoparticle volume fraction of the nanofluids on the flow and heat transfer performance.Design/methodology/approachA heat sink with discontinuous arc protrusions in the wall jet region is proposed for confined slot jet impingement. A sloping upper cover plate is added to improve the heat transfer effect in this area. An Al2O3–water nanofluid is selected as the working fluid of the jet for better heat transfer. The Standard k-e turbulence model is used for numerical calculation. The key structural parameters of the heat sink are optimized by the response surface method and a genetic algorithm. The effects of the jet Reynolds number (Re) and the nanofluid concentration (ϕ) on the flow and heat transfer performance of the optimized heat sink are investigated.FindingsThe average Nusselt number of the optimal heat sink is 8.2% higher and the friction resistance is 5.9% lower than that of the initial flat plate heat sink when ϕ = 0.02 and Re = 8,000. The discontinuous arc protrusions and the sloping upper cover plate substantially enhance the heat transfer in the later stage of jet development, improving the temperature uniformity of the heat sink. The maximum temperature difference of the optimal heat sink is 28.1% lower than that of the flat plate heat sink at the same nozzle height. As the jet Reynolds number and the nanofluid particle concentration increase, the Nusselt number of the optimized heat sink and the friction coefficients increase, resulting in a decrease in the evaluation coefficient. However, the overall temperature uniformity of the heat sink is improved under all conditions.Originality/valueThe novel heat sink structure provides a new way to enhance the heat transfer and temperature uniformity of confined slot jet impingement. The flow and heat transfer performance of the heat sink impinged by confined slot jet of nanofluids are obtained. The combination of response surface method and genetic algorithm can be applied to the multi-objective optimization of heat resistance and flow resistance of heat sink.

Influence of ratio of nozzle length to diameter on local heat transfer study of an unconfined circular air jet impingement

The influence of ratio of nozzle length to diameter on local heat transfer characteristics of an unconfined circular air jet impingement on flat plate is studied experimentally. The ratio of nozzle length to diameter (L/D = 0.5 to 83), nozzle to plate surface (z/D = 0.2 to 2) and Reynolds number (Re = 12,000 to 28,000) is investigated. The local heat transfer characteristics are reported at stagnation and wall jet region by using IR thermal imager and thin foil technique. Peak Nu occurs at wall jet area for z/D = 0.2 rather than at stagnation point for all L/D ratios and is substantially dependent on z/D and Re. It is caused by flow acceleration due to venacontraction effect between the nozzle and target surfaces which results in higher Nu in wall jet area than in stagnation area. For all Reynolds number, long pipe nozzle gives higher stagnation Nu value at z/D < 0.75 due to fully developed flow at nozzle outlet and L/D = 0.5 gives higher stagnation Nu value at z/D > 0.75 due to higher turbulence motion at nozzle outlet. At z/D < 0.4, L/D = 0.5 has a lower Nu at all L/D ratios in wall jet area (R/D > 2) and it decreases as Re increases. The influence of L/D ratio in wall jet zone (R/D > 1.8) is nearly comparable at all Re for z/D > 0.75. The L/D ratios are least influenced at lower Re and higher z/D value. The correlation of stagnation Nu was obtained with maximum deviation of ±16% to the maximum heat transfer rate for optimum conditions.

Large-Eddy Simulation of two secondary air supply strategies in kraft recovery boilers

Kraft recovery boilers are large scale combustion applications operating on black liquor, a common side-product of the pulp industry. Here, a simplified boiler model utilizing Computational Fluid Dynamics (CFD) with Large-Eddy Simulation (LES) and Lagrangian Particle Tracking (LPT) is explored to better understand the secondary air supply system and the dispersion of sprayed droplets. The unsteady nature of the air jets and droplet dispersion in such context advocates the usage of scale-resolving simulations such as LES. In the present exploratory study, the usage of LES in recovery boiler air jet simulations is piloted for the first time. The air supply system is modeled as high-momentum-flux jets injected to a uniform cross-flow. First, the set-up was verified by performing a mesh sensitivity study. The main observed global flow features included the mixing zones, wall jet and jet impact regions, jet bending in cross-flow, and reverse flow downstream of the jets. Two different engineering relevant air supply systems, a staggered and an in-line configuration, were studied and compared in terms of mixing and droplet dispersion. The main findings of the present study are as follows. First, out of the two studied configurations, the staggered one was observed to provide a more uniform downstream temperature field. Second, the in-line configuration was noted to outperform the staggered configuration in droplet dispersion by having 22% less spray-wall impingement and 15% more droplets landing at the bottom of the furnace. Third, different modes for droplet trajectories were identified based on the global flow structures.

Experimental and LES study of unconfined jet impingement on a smooth flat heated plate with slots of different widths

ABSTRACT The present work focuses on the experimental and large-eddy simulation (LES) investigation of fluid flow and heat transfer due to the impingement of an unconfined turbulent slot jet on a smooth flat plate. Three LES sub-grid scale models are validated with the experimental observations for first time in terms effect of slot widths. A detailed parametric study is conducted considering nozzle to plate spacing ratio from 4 to 12, non-dimensional slot width from 0.015 to 0.035, and Reynolds number range from 4000 to 12000. The results show an appreciable change in the stagnation point and along the wall jet Nusselt numbers with the change in Reynolds number, nozzle-to-plate spacing and non-dimensional slot width. No significant effect of nozzle to plate spacing is observed along the wall jet Nusselt number beyond the streamwise location at 0.2. The local Nusselt number increases with an increase in Reynolds number while it decreases with an increase in nondimensional slot width. Comparison of various LES sub-grid models with RANS (k-ω SST) turbulence model is performed. The results show that turbulent kinetic energy plays a major role in enhancing the heat transfer rate. Dissipation of the turbulent kinetic energy increases with an increase in nozzle to plate spacing and non-dimensional slot width. Further, a correlation is proposed for the stagnation point and wall jet region Nusselt numbers in terms of effect of slots width, Reynolds number and non-dimensional nozzle to plate spacing.