Effect of Pore Density on Jet Impingement Onto Thin Metal Foams Under Intermediate Crossflow Scheme

2019 ◽  
Author(s):  
Srivatsan Madhavan ◽  
Vivek Subramaniam Sambamurthy ◽  
Prashant Singh ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Metal Foams ◽  
Thin Metal ◽  
High Porosity ◽  
Pore Density ◽  
Transfer Coefficients ◽  
Plate Spacing

Abstract Array jet impingement heat transfer onto thin metal foams of different pore densities has been experimentally investigated in the current study. Aluminum foams with high porosity (93%) and different pore densities of 5, 20 and 40 ppi are subjected to array jet impingement under an intermediate crossflow exit scheme. The jets are arranged such that the streamwise jet-to-jet spacing is x/dj = 8 and spanwise jet-to-jet spacing is y/dj = 4. Jet to target plate spacing was maintained at z/dj = 6 where ‘z’ is the distance between the jet plate and the target surface on which metal foams were installed. A steady state heat transfer technique has been used to obtain local heat transfer coefficients along the streamwise direction. It is observed that heat transfer enhancement levels increase as pore density increases. An enhancement of 50–100% over the baseline case of impingement onto smooth surface is obtained over the flow range tested (3000 < Redj < 12000). At a constant pumping power of 40 W, an enhancement of 26–33% is obtained for the different pore densities tested.

Jet Impingement Heat Transfer Enhancement by Packing High-Porosity Thin Metal Foams Between Jet Exit Plane and Target Surface

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Srivatsan Madhavan ◽  
Prashant Singh ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Metal Foam ◽  
Jet Impingement ◽  
Target Surface ◽  
Metal Foams ◽  
Thin Metal ◽  
High Porosity ◽  
Pumping Power ◽  
Transfer Enhancement

High-porosity metal foams are known for providing high heat transfer rates, as they provide a significant increase in wetted surface area as well as highly tortuous flow paths resulting in enhanced mixing. Further, jet impingement offers high convective cooling, particularly at the jet footprint areas on the target surface due to flow stagnation. In this study, high-porosity thin metal foams were subjected to array jet impingement, for a special crossflow scheme. High porosity (92.65%), high pore density (40 pores per inch (ppi)), and thin foams (3 mm) have been used. In order to reduce the pumping power requirements imposed by full metal foam design, two striped metal foam configurations were also investigated. For that, the jets were arranged in 3 × 6 array (x/dj = 3.42, y/dj = 2), such that the crossflow is dominantly sideways. Steady-state heat transfer experiments have been conducted for varying jet-to-target plate distance z/dj = 0.75, 2, and 4 for Reynolds numbers ranging from 3000 to 12,000. The baseline case was jet impingement onto a smooth target surface. Enhancement in heat transfer due to impingement onto thin metal foams has been evaluated against the pumping power penalty. For the case of z/dj = 0.75 with the base surface fully covered with metal foam, an average heat transfer enhancement of 2.42 times was observed for a concomitant pressure drop penalty of 1.67 times over the flow range tested.

scholarly journals Array Jet Impingement On High Porosity Thin Metal Foams: Effect of Foam Height, Pore-Density and Spent Air Crossflow Scheme On Flow Distribution and Heat Transfer

2020 ◽  
Author(s):  
Vivek Subramaniam Sambamurthy ◽  
Srivatsan Madhavan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Flow Distribution ◽  
Jet Impingement ◽  
Metal Foams ◽  
Thin Metal ◽  
High Porosity ◽  
Pore Density ◽  
Pumping Power ◽  
Local Flow ◽  
Target Spacing

Abstract An experimental investigation was carried out to study heat transfer and fluid flow in high porosity (93%) thin metal foams subjected to array jet impingement, under maximum and intermediate crossflow exit schemes. Separate effects of pore-density and jet-to-target spacing (z/d) have been studied. To this end, for a fixed pore-density of 40PPI foams, three different jet-to-target spacing (z/d=1, 2, 6) were investigated, and for a fixed z/d of 6, three different pore-density of 5, 20 and 40PPI were investigated. The jet diameter-based Reynolds number was varied between 3,000-12,000. Experiments were carried out to characterize local flow distribution and Nusselt numbers for different jet impingement configurations. The heat transfer results were obtained through steady-state experiments. Local flow measurements show that, as z/d decreases, the mass flux distributions are increasingly skewed with higher mass flow rates near the exits. Heat transfer enhancement has been calculated and the optimum foam configuration has been deduced from the pumping power. It was observed that Nusselt number increases with increasing pore density at a fixed z/d and reduces with increase in z/d at constant pore density. Intermediate crossflow had higher heat transfer than maximum crossflow with significantly lower pumping power. Under a constant pumping power condition, z/d = 2, 40ppi foam provided an average enhancement of 35% over the corresponding baseline configuration for intermediate crossflow scheme and was found to be the most optimum configuration.

Effect of Film Extraction on Impingement Heat Transfer Characteristics of Jet Arrays on Spherical-Dimpled Surfaces

2015 ◽  
Author(s):  
Xing Yang ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Coupling Effect ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Local Heat ◽  
Separation Distance ◽  
Plate Spacing

Detailed heat transfer distributions are numerically investigated on a multiple jet impingement target surface with staggered arrays of spherical dimples where coolant can be extracted through film holes for external film cooling. The three dimensional Reynolds-averaged Navier-Stokes analysis with SST k-ω turbulence model is conducted at jet Reynolds number from 15,000 to 35,000. The separation distance between the jet plate and the target surface varies from 3 to 5 jet diameters and two jet-induced crossflow schemes are included to be referred as large and small crossflow at one and two opposite exit openings correspondingly. Flow and heat transfer results for the dimpled target plate with three suction ratios of 2.5%, 5.0% and 12.0% are compared with those on dimpled surfaces without film holes. The results indicate the presence of film holes could alter the local heat transfer distributions, especially near the channel outlets where the crossflow level is the highest. The heat transfer enhancements by applying film holes to the dimpled surfaces is improved to different degrees at various suction ratios, and the enhancements depend on the coupling effect of impingement and channel flow, which is relevant to jet Reynolds number, jet-to-plate spacing and crossflow scheme.

Heat Transfer of Confined Circular Jet Impingement

2001 ◽  
Vol 17 (1) ◽  
pp. 29-38
Author(s):  
Shou-Shing Hsieh ◽  
Jung-Tai Huang ◽  
Huang-Hsiu Tsai
Keyword(s):  
Heat Transfer ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Local Heat ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Plate Spacing ◽  
Single Jet

ABSTRACTExperiments for heat transfer characteristics of confined circular single jet impingement were conducted. The effect of jet Reynolds number, jet hole-to-plate spacing and heat flux levels on heat transfer characteristics of the heated target surface was examined and presented. The local heat transfer coefficient along the surface is measured and correlations of the stagnation point, local and average Nusselt number are developed and discussed. Finally, comparisons of the present data with existing results were also made.

scholarly journals Opportunities in Jet-Impingement Cooling for Gas-Turbine Engines

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6587
Author(s):  
Sandip Dutta ◽  
Prashant Singh
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Target Surface ◽  
Turbine Engines ◽  
High Porosity ◽  
Transfer Coefficients ◽  
Impingement Cooling ◽  
Heat Transfer Coefficients ◽  
Impingement Heat Transfer ◽  
Convective Heat Transfer Coefficients

Impingement heat transfer is considered one of the most effective cooling technologies that yield high localized convective heat transfer coefficients. This paper studies different configurable parameters involved in jet impingement cooling such as, exit orifice shape, crossflow regulation, target surface modification, spent air reuse, impingement channel modification, jet pulsation, and other techniques to understand which of them are critical and how these heat-transfer-enhancement concepts work. The aim of this paper is to excite the thermal sciences community of this efficient cooling technique and instill some thoughts for future innovations. New orifice shapes are becoming feasible due to innovative 3D printing technologies. However, the orifice shape variations show that it is hard to beat a sharp-edged round orifice in heat transfer coefficient, but it comes with a higher pressure drop across the orifice. Any attempt to streamline the hole shape indicated a drop in the Nusselt number, thus giving the designer some control over thermal budgeting of a component. Reduction in crossflow has been attempted with channel modifications. The use of high-porosity conductive foam in the impingement space has shown marked improvement in heat transfer performance. A list of possible research topics based on this discussion is provided in the conclusion.

scholarly journals Heat Transfer and Flow Characteristics of Circular Jets Impinging on a Horizontal Flat Wall

1997 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Jung-Tai Huang
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Local Heat ◽  
Plate Spacing ◽  
Fundamental Understanding ◽  
Circular Jets ◽  
Single Jet

An experimental study was performed in a confined circular single jet impingement. The effect of jet Reynolds number, nozzle-to-plate spacing and heat flux levels on heat transfer characteristics of the heated target surface was examined and presented. Flow visualization was made to broaden our fundamental understanding of the physical process of the type of flow. Transition and turbulent regimes are identified. The local heat transfer coefficient along the surface is measured and correlation of the stagnation point Nusselt number are presented and discussed.

Array Jet Impingement Onto High Porosity Thin Metal Foams at Zero Jet-to-Foam Spacing

2018 ◽  
Author(s):  
Prashant Singh ◽  
Mingyang Zhang ◽  
Jaideep Pandit ◽  
Roop L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Performance Enhancement ◽  
Jet Impingement ◽  
Metal Foams ◽  
Thin Metal ◽  
High Porosity ◽  
Transfer Rates

Metal foams enhance heat transfer rates by providing significant increase in wetted surface area and by thermal dispersion caused by flow mixing induced by the tortuous flow paths. Further, jet impingement is also an effective method of enhancing local convective heat transfer rates. In the present study, we have carried out an experimental investigation to study the combined effect of the two thermal performance-enhancement mechanisms. To this end, we conducted a set of experiments to determine convective heat transfer rates by impinging an array of jets onto thin metal foams attached on a uniformly heated smooth aluminum plate simulating a high heat-dissipating chip. The metal foams used were high porosity aluminum foams (ε∼0.94–0.96) with pore densities of 5 ppi, 10 ppi and 20 ppi (ppi: pores per inch) with thicknesses of 19 mm, 12.7 mm and 6.35 mm, respectively. With the jet-to-foam distance (z/d) set to zero, we conducted experiments with values of jet-to-jet spacing (x/d = y/d) of 2, 3 and 5. The jet plate featured an array of 5 × 5 cylindrical jet-issuing nozzles. The normalized jet-to-jet distance was varied by changing the jet diameter and keeping the jet center-to-center distance constant. Steady state heat transfer and pressure drop experiments were carried out for Reynolds number (based on jet diameter) ranging from 2500 to 10000. We have found that array impingement on thin foams leads to a significant enhancement in heat transfer compared to normal impingement over smooth surfaces. The gain in heat transfer was greatest for the 20 ppi foam (∼2.3 to 2.8 times that for the plain surface smooth target). However, this enhancement came at a significant increase of about 2.85 times in the plenum static pressure. With the pressure drop penalty taken into consideration, the x/d = 3 jet plate for the 20 ppi foam and x/d = 2 jet plate for the 10 ppi foam were found to be the most efficient cooling designs amongst the 18 cooling designs investigated in the present study.

Experimental Investigation of Heat Transfer Enhancement Through Array Jet Impingement on Various Configurations of High Porosity Thin Metal Foams

2018 ◽  
Author(s):  
Srivatsan Madhavan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Stresses ◽  
Metal Foam ◽  
Jet Impingement ◽  
Metal Foams ◽  
Thin Metal ◽  
High Porosity ◽  
Pumping Power ◽  
Transfer Enhancement

High porosity metal foams are known for providing high heat transfer rates, as they provide significant increase in wetted surface area as well as highly tortuous flow paths to coolant flowing over fibers. Further, jet impingement is also known to offer high convective cooling, particularly on the footprints of the jets on the target to be cooled. Jet impingement, however, leads to large special gradients in heat transfer coefficient, leading to increased thermal stresses. In this study, we have tried to use high porosity thin metal foams subjected to array jet impingement, for a special crossflow scheme. One aim of using metal foams is to achieve cooling uniformity also, which is tough to achieve for impingement cooling. High porosity (92.65%) and high pore density (40 pores per inch, 3 mm thick) foams have been used as heat transfer enhancement agents. In order to reduce the pumping power requirements imposed by full metal foam design, we developed two striped metal foam configurations. For that, the jets were arranged in 3 × 6 array (x/d = 3.42, y/d = 2), such that the crossflow is dominantly sideways. This crossflow scheme allowed usage of thin stripes, where in one configuration we studied direct impingement onto stripes of metal foam and in the other, we studied impingement onto metal and crossflow interacted with metal foams. Steady state heat transfer experiments have been conducted for a jet plate configuration with varying jet-to-target plate distance z/d = 0.75, 2 and 4. The baseline case was jet impingement onto a smooth target surface. Jet diameter-based Reynolds number was varied between 3000 to 11000. Enhancement in heat transfer due to impingement onto thin metal foams has been evaluated against the enhancement in pumping power requirements. For a specific case of z/d = 0.75 with the base surface fully covered with metal foam, metal foams have enhanced heat transfer by 2.42 times for a concomitant pressure drop penalty of 1.67 times over the flow range tested.

scholarly journals Investigations of Flow and Heat Transfer Characteristics in a Channel Impingement Cooling Configuration with a Single Row of Water Jets

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4327
Author(s):  
Min-Seob Shin ◽  
Santhosh Senguttuvan ◽  
Sung-Min Kim
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Channel Height ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Impingement Cooling ◽  
Average Heat ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

The present study experimentally and numerically investigates the effect of channel height on the flow and heat transfer characteristics of a channel impingement cooling configuration for various jet Reynolds numbers in the range of 2000–8600. A single array consisting of eleven jets with 0.8 mm diameter injects water into the channel with 2 mm width at four different channel heights (3, 4, 5, and 6 mm). The average heat transfer coefficients at the target surface are measured by maintaining a temperature difference between the jet exit and the target surface in the range of 15–17 °C for each channel height. The experimental results show the average heat transfer coefficient at the target surface increases with the jet Reynolds number and decreases with the channel height. An average Nusselt number correlation is developed based on 85 experimentally measured data points with a mean absolute error of less than 4.31%. The numerical simulation accurately predicts the overall heat transfer rate within 10% error. The numerical results are analyzed to investigate the flow structure and its effect on the local heat transfer characteristics. The present study advances the primary understanding of the flow and heat transfer characteristics of the channel impingement cooling configuration with liquid jets.

Nanoliquid jet impingement heat transfer for a phase change material (PCM) embedded radial heating system

2021 ◽  
pp. 1-10
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Material ◽  
Jet Impingement ◽  
Target Surface ◽  
Spatial Average ◽  
Average Heat ◽  
Plate Spacing ◽  
Impingement Heat Transfer ◽  
Change Material

Abstract Nanoliquid impingement heat transfer with phase change material (PCM) installed radial system is considered. Study is performed by using finite element method for various values of Reynolds numbers (100 ≤ Re ≤ 300), height of PCM (0.25H ≤ hpcm = 0.7H ≤ 0.75H) and plate spacing (0.15H ≤ hpcm = 0.7H ≤ 0.40H). Different configurations with using water, nanoliquid and nanoliquid+PCM are compared in terms of heat transfer improvement. Thermal performance is improved by using PCM while best performance is achieved with nanoliquid and PCM installed configuration. At Re=100 and Re=300, heat transfer improvements of 26% and 25.5% are achieved with nanoliquid+PCM system as compared to water without PCM. Height of the PCM layer also influences the heat transfer dynamic behavior while there is 12.6% variation in the spatial average heat transfer of the target surface with the lowest and highest PCM height while discharging time increases by about 76.5%. As the spacing between the plates decreases, average heat transfer rises and there is 38% variation.

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