In-line Array Research Articles

Investigating the Unsteady Dynamics of a Multi-Jet Impingement Cooling Flow Using Large Eddy Simulation

Abstract We investigate the unsteady behavior of an in-line jet impingement array of nine jets at a Reynolds number of 10,000 in a narrow channel subjected to a developing cross flow of up to 25% of the bulk jet velocity. To this end, we present an improved version of a previously published large eddy simulation (LES) now with resolved turbulence at the inflow boundaries. After a careful analysis of the transient behavior and statistical convergence of the LES, we discuss the time-averaged heat transfer characteristics of the configuration compared to numerical references of similar configurations. We then show how the large-scale unsteadiness increases from jet to jet. Both space-only and spectral proper orthogonal decompositions (POD and SPOD) are used to discuss the large-scale organization of single jets and multiple jets in combination. The latter shows a qualitative change in the unsteady behavior of the temperature footprint on the impingement wall with increasing cross flow.

Performance analysis of spherically curbed hydrokinetic turbine arranged in ln-line array in a closed conduit

The present study aims to explore the applicability of hydrokinetic turbine (HKT) in a closed conduit. Spherically curbed Savonius HKT (SSHKT) was designed to calculate turbine performance (CP). Pipe flow velocity (V) is kept as 1.0, 2.0 and 3.0 m/s. Turbine performance declines as velocity increases, due to obstruction created by the turbine in the flow passage, flow instability, and separation. Performance of multiple SSHKTs was investigated installed in inline array. These turbines were arranged at varying distance of 2.5D, 3D, 3.5D, 4D, 4.5D and 5D, where D is the turbine diameter. The SSHKTs performed best at 3.5D irrespective of flow velocity. The number of the turbines increase the power production; however, efficiency of the system doesn't increase in that proportion. The CP of the first SSHKT was always higher compared to the next one along the array. In the pipeline, for single turbine, the high flow velocity causes a more significant pressure drop than the low flow velocity. At V = 1.0 m/s, the pressure drop for a single SSHKT is 8.52 %; whereas, at V = 2.0 m/s, the pressure drop is 28.69 %. Due to more blocked places in the arrayed turbines, the percentage pressure loss is greater.

A top-mounted, chain-driven, bidirectional point absorber type wave energy convertor

The aims of this paper are to introduce the structure of a point absorber type wave energy convertor (WEC) mounted above sea level, to analyze the motion characteristics and power absorptions of such a WEC and to describe the numerous advantages of installing it in the nearshore. The motion equation is solved by representing the excitation force with the dynamic wave pressure and obtaining an approximate system transfer function. The possibility of the buoy becoming airborne or submerged is considered and the power absorption is increased optimally by reshaping the frequency response using a flywheel. The time, phase and spectral averages of power absorptions are presented for offshore waves, nearshore waves and for concentrated nearshore waves using standard wave spectrums and compared. Approximate gains possible with linear and rectangular arrays are also presented. Considering different phase distributions, it is shown that downgrading WECs based on short term power absorptions is not justifiable. With a buoy of radius 2 m, the power absorption of this kind of a WEC is estimated to be about 114 kW in the deep sea and 117 kW in the nearshore, when the energy flux is about 31 kW/m. By concentrating just 13.6 kW/m nearshore waves, it could be increased to 186 kW. If a 3-element longshore in-line array is placed inside the wave concentrator, the total power absorption could be about 556 kW. A 9-element rectangular array would be capable of absorbing about 1 MW by making use of the remaining energy of the down wave.

Multiplexing and passive demodulation of intrinsic low-finesse Fabry-Perot interferometers using free-running DFB diode lasers

This paper presents a novel and simple technique for passive quadrature demodulation of multiplexed low-finesse fiber-optic Fabry-Perot interferometers. The approach proposed here uses two quadrature channels with very close wavelengths generated by two thermostabilized DFB diode lasers operating in continuous-wave mode. A coherent light correlation technique was used to demultiplex the wavelength channels and signals from interferometers at different positions along the fiber. The proposed technique does not require optical filters for spectral channel demultiplexing, making it suitable for demodulating relatively long interferometers with any free spectral range. An in-line array of four identical 13.1 cm long interferometers was used to demonstrate the method's performance. Experimental results demonstrate a phase resolution of 1.38 phase degrees, corresponding to a temperature resolution of 3 × 10−3 °C. Numerical simulations indicate that the main factor limiting the length of the sensing interferometer, and thus the resolution of the system, is the wavelength variation of the temperature-stabilized, independently operating lasers. The number of spectral channels can be easily extended to realize three or four-wavelength demodulation schemes.

Numerical investigation of bubble dynamics and flow boiling heat transfer in cylindrical micro-pin-fin heat exchangers

Micro-pin-fin evaporators are a promising alternative to multi-microchannel heat sinks for two-phase cooling of high power-density devices. Within pin-fin evaporators, the refrigerant flows through arrays of obstacles in cross-flow and is not restricted by the walls of a channel. The dynamics of bubbles generated upon flow boiling and the associated heat transfer mechanisms are expected to be substantially different from those pertinent to microchannels; however, the fundamental aspects of two-phase flows evolving through micro-pin-fin arrays are still little understood. This article presents a systematic analysis of flow boiling within a micro-pin-fin evaporator, encompassing bubble, thin-film dynamics and heat transfer. The flow is studied by means of numerical simulations, performed using a customised boiling solver in OpenFOAM v2106, which adopts the built-in geometric Volume of Fluid method to capture the liquid–vapour interface dynamics. The numerical model of the evaporator includes in-line arrays of pin-fins of diameter of 50μm and height of 100μm, streamwise pitch of 91.7μm and cross-stream pitch of 150μm. The fluid utilised is refrigerant R236fa at a saturation temperature of 30 °C. The range of operating conditions simulated includes values of mass flux G=500–2000kg/(m2s), heat flux q=200kW/m2, and inlet subcooling ΔTsub=0–5K. This study shows that bubbles nucleated in a pin-fin evaporator tend to travel along the channels formed in between the pin-fin lines. Bubbles grow due to liquid evaporation and elongate in the direction of the flow, leaving thin liquid films that partially cover the pin-fins surface. The main contributions to heat transfer arise from the evaporation of this thin liquid film and from a cross-stream convective motion induced by the bubbles in the gap between the cylinders, which displace the hot fluid otherwise stagnant in the cylinders wakes. When the mass flow rate is increased, bubbles depart earlier from the nucleation sites and grow more slowly, which results in a reduction of the two-phase heat transfer. Higher inlet subcooling yields lower two-phase heat transfer coefficients because condensation becomes important when bubbles depart from the hot pin-fin surfaces and reach highly subcooled regions, thus reducing the two-phase heat transfer.

Numerical Simulation of the Influencing Factors of Array Jet Shock Cooling

Array jet impingement cooling is a significant technology of enhanced heat dissipation which is fit for high heat flux flow with large area. It is gradually applied to the cooling of electronic devices. However, The researches on the nozzle array mode and the uniformity of cooling surface still have deficiencies. Therefore, the influence of heat flux, inlet temperature, jet height, array mode and diversion structure on jet impingement cooling performance and temperature distribution uniformity is analyzed by means of numerical calculation. The results show that the heat transfer coefficient of jet impingement cooling increases linearly with the increment of heat flux and inlet temperature. With the increment of the ratio of jet height to nozzle diameter (H/d), the heat transfer coefficient increases first and then decreases, that is, there is an optimal H/d, which makes the heat transfer performance of the array jet impact cooling best. The temperature uniformity of array jet impact cooling is greatly affected by array mode. The improvement effect of nozzle array mode on temperature uniformity is ranked as sequential > staggered > shield > elliptical array. The overall temperature uniformity and heat transfer coefficient are increased by 5.88% and 7.29% compared with elliptical array. The heat transfer performance can be further improved by adding a flow channel to the in-line array layout, in which the heat transfer coefficient is increased by 6.53% and the overall temperature uniformity is increased by 1.45%.

CYLINDRICAL CROSS-BARS FOR THERMAL PERFORMANCE AUGMENTATION IN AIR CHANNEL

Experiments of the heat transfer and pressure drop are performed in a rectangular channel employing eight different arrays of cylindrical cross-bars as inserts. Numerical simulations are also performed to examine the secondary flow caused by the cylinders. The objectives are to investigate the enhancement of the channel-wall heat transfer and pressure drop caused by the local flow, cylinder array geometry, and flow Reynolds number. Two different cylinder diameters of 1.0 mm and 2.0 mm are employed. The diameter of 2.0 mm is used to create four in-line arrays while the diameter of 1.0 mm is used to create four staggered arrays of the cylinders. The cylinder arrays employ different diameter-to-pitch ratios (0.025 to 0.2) and cylinder orientations (45°, 90°) relative to the main flow direction. The flow Reynolds number is varied between 600 and 13,000. Only two array geometries, one in-line and one staggered, with the cylinders oriented at 90° to the flow are modeled for the numerical study. The numerical results show that the local flow accelerates in the gap between the cylinder and channel wall. The vortex shedding downstream of the cylinders interacts with the channel wall. The Nusselt number on the channel wall and the friction factor are measured with and without the cylinders. The ratios of Nusselt numbers and friction factors increase with the Reynolds number when the Reynolds number is less than 3000. The ratios always increase with the diameter-to-pitch ratio.

Neural network-based regression for heat transfer and fluid flow over in-line cylinder arrays with random pitch distances at low Reynolds number

Finding an arrangement, leading to a higher heat transfer and lower pressure drop, is crucial in the design of heat exchangers. Previous studies have primarily focused on regular arrangements with uniform pitch distances, which lack applicability to general configurations. In this study, we proposed a new procedure of a flow-learned building block (FLBB) to predict heat transfer in an in-line cylinder array with random pitch distances using a neural network-based regression analysis with a systematic data generation process. As a first step, we demonstrated the FLBB’s capability to predict the heat transfer and pressure drop in in-line cylinder arrays with random pitch distances at low Reynolds numbers from 1 to 100 for air ( ). Subsequently, a high-order FLBB approach was proposed to address the spatial interdependency between neighbouring cylinders, particularly in scenarios where vortex shedding occurs in the wake of cylinders at increased Reynolds numbers. The high-order FLBB approach was then shown to successfully describe various flow and temperature patterns using cylinder arrays with random pitch distances. The proposed procedure exhibited remarkable efficiency, requiring only about 1 s. Furthermore, the FLBB was successfully extended to various flow regimes, even encompassing unseen Reynolds numbers from 1 to 100.

Wind-tunnel analysis of turbulent flow in cross-ventilated buildings with windcatchers: Impact of surrounding buildings

This paper presents a detailed experimental analysis of ventilation flows in a building with a windcatcher surrounded by building arrays. The surrounding building arrangements were in two forms: inline and staggered, representing an abstract variety of suburban morphology. Ventilation measurements were performed for five approaching wind directions: two normal to the building opening(s) at 0° and 180° orientations, two oblique at 40° and 140° orientations, and one parallel to the building opening(s) at 90° orientation. Time-averaged and instantaneous data analyses were carried out. The time-averaged approach showed the overall ventilation flow interaction with the building. Meanwhile, the instantaneous data analysis helped investigate the unsteady airflow characteristics. Hence, the room pressure fluctuations were considered in the frequency domain. Additionally, the coefficient of variance and probability density functions were obtained to identify the nature of ventilation flow fluctuations.The results showed that the maximum reductions in ventilation rate were 30% and 42% for the inline and staggered arrays, respectively, compared to an isolated building case. The highest obstructions of the onset flow to the openings occurred at direct wind incidences for the inline array and oblique wind incidences for the staggered array. The nearby buildings enhanced the fluctuating ventilation flows at 0° and 180° incidences. However, the isolated building case showed the highest fluctuations at 90° incidence since the turbulent flow was mostly dissipated along the surrounding street canyons for the arrayed cases. The room interior pressure fluctuations and spectra showed prominent peaks associated with the Helmholtz frequency in all case studies.

Performance assessment of multi-tube inline and staggered array based latent heat storage system

In this article, the charging and discharging characteristics of a shell and multi-tube latent heat storage system are investigated numerically to select a suitable array type for the multiple heat transfer tubes. This study considers nine tubes in eight different arrangements. Numerical simulations on simplified two-dimensional paraffin wax domain were performed using ANSYS Fluent. The results are depicted as contours and streamlines to visualize the progress of melting and solidification. The transient performance is evaluated based on the variation of liquid fraction, heat transfer rate at tube surfaces, melting time, and amount of energy stored with time. The results show that the rate of melting and energy storage performance depend greatly on the configuration of tubes. The staggered array with high tube pitch to tube diameter ratio (PR) cases reported better performance. By changing the arrangement of tubes, a 74.2 % reduction in melting time is observed for the staggered array with PR = 3.5, i.e. S3.5 case, as compared to the inline array with PR = 2, i.e. I2 case. By changing the arrangement of tubes, a 9 % improvement in the amount of energy stored is achieved for the S3.5 array compared to the I2 array for 300 min of charging. Unlike melting, solidification is governed by conduction thus for the same value of PR, the solidification time was almost the same for the both inline and staggered arrays. Higher PR cases performed faster solidification, and about 56 % reduction in solidification time is observed for PR = 3.5 as compared to PR = 2 cases.

Application of Taguchi method and response surface methodology (RSM) for parametric optimization of natural convection heat transfer inside a triangular porous enclosure with in-line rectangular finned array

ABSTRACT Taguchi method is an experimental design methodology that uses a statistical technique to optimize process parameters while minimizing variability and improving output quality. In this article, Taguchi methodology has been utilized for parametric optimization of the design of a porous triangular enclosure, with an in-line rectangular finned array, to achieve maximum natural convection heat transfer. Three influencing parameters viz. fin spacing (S), percentage volume occupied (Vo) (measure of enclosure porosity), and fin tip to cooling plate distance (d), are optimized with consideration of maximizing the heat transfer (i.e. Nusselt number). The experimental design has been created using Taguchi’s L9 (3^3) orthogonal array. An analysis of variance (ANOVA) table, regression equation, response surfaces, and contour plots have also been generated using Response surface methodology, and the optimum values of influencing parameters have been suggested.

High-speed, multi-zone ultrasonic inspection of bar and wire stocks with an in-line phased array inspection system

Typical standards in aerospace applications require the ultrasonic testing (UT) of bar and wire stock with a highly reliable detection of small defects over a wide depth range in the material. Characteristic reference reflectors are flat bottom holes (FBH) with diameters smaller than 1 mm. Typically, such inspections are done with immersion tanks using a set of probes optimized for each depth. However, for industrial applications there are disadvantages such as slow scan speed, the time-consuming inlet and outlet process, complicated mechanics and significant costs of the specialized probes. This contribution demonstrates an in-line phased array inspection system with integrated multi-zone inspection, which is based on the Krautkrämer ROWA™ Ux machine. After a short description of the setup special focus is given on the implemented testing concept which is optimized with respect to a multi-zone inspection and includes a dedicated automated adjustment of the system. Furthermore, the powerful electronics allows a flexible setting of focus point, aperture size and filtering. This significantly reduces the need for special probes and by means of digital depth focusing (DDF) also the number of test shots. At the end, the flaw detectability in different depths is illustrated and achievable test speeds are presented. Moreover, external boundary conditions are discussed.

Numerical Simulation of Flow and Heat Transfer Characteristics in Non-Closed Ring-Shaped Micro-Pin-Fin Arrays

In this study, flow and heat transfer characteristics in novel non-closed 3/4 ring-shaped micro-pin-fin arrays with in-line and staggered layouts were investigated numerically. The flow distribution, wake structure, vorticity field and pressure drop were examined in detail, and convective heat transfer features were explored. Results show that vortex pairs appeared earlier in the ring-shaped micro-pin-fin array compared with the traditional circular devices. Pressure drop across the microchannel varied with layout of the fins, while little difference in pressure drop was observed between ring-shaped and circular fins of the same layouts, with the maximum difference being 1.43%. The staggered ring-shaped array was found to outperform the in-line array and the circular arrays in convective heat transfer. A maximum increase of 21.34% in heat transfer coefficient was observed in the ring-shaped micro-pin-fin array in comparison with the circular micro-pin-fin array. The overall thermal-hydraulic performance of the microstructure was evaluated, and the staggered ring-shaped array with a fin height of 0.5 mm exhibited the best performance among the configurations studied.

Hydrodynamic and thermal performance of in-line strip-fin manifold microchannel heat sink

In this work, an in-line strip-fin manifold microchannel heat sink is proposed to improve the hydrodynamic and thermal performance of the conventional manifold microchannel. The hydrodynamic and thermal performance of varying strip-fin arrangements with approximately the same heat transfer area are numerically investigated. The results show that the in-line strip-fin manifold microchannel has lower pressure drop and better thermal performance than that of the conventional manifold microchannel at the same inlet mass flux. For varying strip-fin arrangements studied in this work, the pressure drop decreases by 15% to 25.5% at the inlet mass fluxes between 600kg/(m2s) and 1800kg/(m2s), compared with the conventional manifold microchannel. The effective overall thermal resistance of the in-line strip-fin manifold microchannel heat sink reaches the minimum value at one specific strip-fin arrangement, which is characterized by the optimal longitudinal number of strip-fins NL,opt. A minimum effective overall thermal resistance of 5.7×10−6m2K/W at an inlet mass flux of 1800kg/(m2s) is achieved. The average temperature of the optimal strip-fin arrangement is about 6.8K lower than that of the conventional manifold microchannel, when the heat flux is 300W/cm2. Heat transfer correlation considering microchannel geometrical parameters is proposed, which can be used to predict the thermal performance of the in-line strip-fin manifold microchannel. Based on the correlation, the effect of the in-line strip-fin array on the thermal performance is qualitatively revealed by thermal resistance analysis.

Feasibility of integrating a very large floating structure with multiple wave energy converters combining oscillating water columns and oscillating flaps

The installation of wave energy converters (WECs) along the facing-wave side of in-development or pre-existing offshore structures provides an effective cost-sharing solution. In this study, a time-domain numerical model based on the modal expansion theory and the nonlinear potential flow theory, is applied to optimize the size and layout of an in-line array of oscillating water column (OWCs) and oscillating flaps (OFs) deployed along the facing-wave side of a very large floating structure (VLFS). The front/back-wall end of each OWC chamber is hinged by an OF device, and thus the number of OWCs is identical with that of OFs. Comparison with a typical OWC-VLFS integration shows that the addition of OFs can significantly reduce the vertical hydroelastic response of the VLFS. Additionally, wave energy extraction from the design of OFs hinged at the back-wall end of OWCs is enhanced due to more wave energy gathered in the chamber. Under the premise of the same space, the array layout demonstrates both higher conervsion efficiency and hydroelastic reduction. The energy conversion is generally enhanced by increasing the gap, the OWC width, the OF height. The maximum efficiency increases firstly with wave height for weak wave nonlinearity and then decreases for strong wave nonliearity.

EXPERIMENTAL DETERMINATION OF THE EFFECT OF FINS OF DIFFERENT CYLINDRICAL GEOMETRIES ON ELECTRICAL AND THERMAL EFFICIENCY IN AN AIR-COOLED PVT SYSTEM

When the temperature of the photovoltaic cell operating under high radiation intensities increases, there is a decrease in its efficiency, in other words, when it is cooled with a liquid or gas, there is an increase in its electrical efficiency. The thermal energy added to this fluid can be used for different needs. In order to prevent this temperature rise, an experimental setup has been designed and manufactured. For the recycling of solar radiation as thermal energy, cylindrical aluminum fins with different surface areas and different geometries subjected to forced convection have been arranged in the channel. The effects of these fins on the total efficiency were evaluated by making different array configurations within the designed control volume. As a result of the evaluations, it has been observed that a better performance has been achieved in the staggered arrangement, although the surface area is less. In the experimental system, fins with different geometries (3-mm, 6-mm axial channel and helically shaped fins) and array positions (inline array and staggered array) have been used. With these fins, electrical efficiency depends on the Reynolds numbers (5400, 6400, and 7400) entering the control volume and the radiation intensity (700 W/m2, 950 W/m2, and 1200 W/m2) is about 13.8-9.7%. This value decreases to 7.9-6.9% in the ordinary PV systems. Thus, it has been concluded that these fins with different surface areas absorb the heat from the photovoltaic cells and play a major role in increasing the efficiency with the decrease in the temperature of the photovoltaic panel. As a result of the measurements, the electrical efficiency of the photovoltaic cells was prevented from falling to 7% under steady-state conditions. In addition to prevention of this energy loss, the thermal energy gained from the control volume is between 630-304 W, depending on the air speed.

Investigation on Circular Array of Turbulent Impinging Round Jets at Confined Case: A CFD Study

Jet impingement has immense applications in industrial cooling, such as glass tempering, turbine blades, electrical equipment, etc. The interplay in-between several jet arrangements and the effect of swirl intensity require enormous study to achieve steady heat transfer. This paper numerically investigates an inline array of 25 circular confined swirling air jets impinging vertically on a flat surface. In this regard, three-dimensional simulations are executed using the finite volume method for a number of control parameters, such as Reynolds number (Re = 11600, 24600, and 35000), impinging distance (H/D = 0.25, 0.5, 1), swirl number (S = 0.3 and 0.75) and jet-to-jet separation distance (Z/D = 2.5), where, D is the nozzle diameter. Impinging pressure distribution, flow velocity, surface Nusselt number, and Reynolds stresses are investigated for different operating conditions. The results reveal that both the wall pressure and surface Nusselt number are comparatively uniform in the case of high swirl flow. Moreover, distinct heat transfer behavior is observed from the unconfined condition for high swirl flow in which the heat transfer is constant after a certain radial distance. The Reynolds normal stress adjacent to the nozzle exit is more rigorous than the downstream regions while Reynolds shear stress varies unpredictably along the radial direction. In addition, an estimated 102 % enhancement in average Nusselt number is observed for high swirl flow, at a Reynolds number increment from 11600 to 35000. This enhancement is evident by 23 % in terms of thermal performance factor. Besides, the average Nusselt number and thermal performance factor augmented by 19 % and 8 %, respectively, for an increased swirl intensity at low a Reynolds number (Re =11600).

Numerical study of the effect of potato cuboids separation in a convective drying

A numerical study (conjugate modeling) of potato cuboid separation in convective drying is performed with the Large Eddy Simulation approach. Any in-line potato array is represented by a single interacted zone through periodic boundary conditions. Numerical code is validated with four experimental studies focused on hydrodynamics (two cases), heat transfer (one case), and mass transfer (one case). Twelve case studies have been proposed to study the effect of streamwise and spanwise distances on heat and mass transfer. Results show that low streamwise separations (0.25) strongly affect the potato drying by the presence of a quasi-stationary wake that causes a blocking effect. The potato cuboid’s best thermal uniformity and mass transfer are presented at a spanwise distance (0.75) and streamwise separations (1.0). Results can be applied to get uniform heat and mass transfer in drying chambers.

Passive quadrature demodulation of multiplexed interferometric sensors using a CW correlation reflectometer with a single DFB diode laser.

In this Letter, we report a novel, to the best of our knowledge, and simple approach for passive quadrature-phase demodulation of relatively long multiplexed interferometers based on two-channel coherence correlation reflectometry. Two-wavelength channels are generated using a single unmodulated CW-DFB diode laser and an acousto-optic frequency shifter. The introduced frequency shift determines the optical lengths of the interferometers. In our experiments, all interferometers have the same optical length of 32 cm corresponding to the π/2 phase difference between channel signals. An additional fiber delay line was introduced between channels to destroy coherence between initial and frequency-shifted channels. Demultiplexing of channels and sensors was performed using correlation-based signal processing. Amplitudes of cross correlation peaks obtained for both channels were used to extract the interferometric phase for each interferometer. Phase demodulation of relatively long multiplexed interferometers is experimentally demonstrated. Experimental results prove that the proposed technique is suitable for interrogating a serial array of relatively long interferometers dynamically modulated with phase excursions exceeding 2π. Simultaneous interrogation and phase demodulation were experimentally demonstrated using an in-line array of low-finesse Fabry-Perot interferometric sensors.

Heat Transfer of a Metal Foamed Flat Plate Impinged by Multiple Jets

The present study focuses on the measurement of the local heat transfer distribution of a smooth flat plate, a flat plate with attached metal foam, and detached metal foam under an inline array of multiple jets using thermal imaging and the thin metal foil technique. After impingement, jet flow exits from all directions. The range of the Reynolds numbers covered in the study is 2500 to 15,000. The impinging distance of to is studied. A 4-mm-thick aluminum metal foam having 92% porosity and 20-pore-per-inch pore density is used. The contribution of the convection and conduction heat for a flat plate with metal foam is studied using a flat plate with a detached foam configuration. The effect of the impinging distance and Reynolds number on the local, spanwise-averaged, and overall averaged Nusselt numbers is studied. The presence of the 4 mm metal foam enhances the local heat transfer in comparison with a smooth flat plate due to conduction heat transfer without the addition of extra hydraulic resistance to the jet flow. The enhancement of the heat transfer due to the presence of the metal foam is quantified by the enhancement factor , and it is found to be around 1.6.