CFD for Jet Impingement Heat Transfer With Single Jets and Arrays

2005 ◽  
Author(s):  
Mounir B. Ibrahim ◽  
Bejoy J. Kochuparambil ◽  
Srinath V. Ekkad ◽  
Terrence W. Simon
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flat Surface ◽  
Turbulent Transport ◽  
Jet Impingement ◽  
Target Plate ◽  
Plate Spacing ◽  
Multiple Jets ◽  
Single Jet ◽  
Jet Axis

CFD experiments were conducted for heat transfer with jet impingement over solid surfaces. The parameters include: 1) Jet Reynolds number from 3,000 to 23,000, 2) Jet-to-target-plate spacing (z/d), from 2 to 14 (single jet), d is jet diameter, 3) Target plate shape: 3a) flat, 3b) concave, 3c) convex, (single jet), 4) One row of seven jets impinging on a flat surface, the channel has one end closed (at 24d away from the most upstream jet axis), 5) Three rows of seven jets each in-line arrangement impinging on a flat surface, the channel has one end closed (at 24d away from the most upstream jet axis). Four CFD models (utilizing FLUENT commercial code) have been considered: 1) laminar flow (no turbulent transport), and turbulent flow with turbulence modeling by 2) the standard k–ε model, 3) the k–ω model, and 4) the v2–f model. The predictions of Nu number for each case were compared with experimental data available from the literature. It is shown that the v2–f model gives the best overall performance, though the k–ω model gives good predictions for most of the flow, with the exception of near the stagnation zone for some cases. The models are in much better agreement (with the data) as z/d grows and at larger radial locations from the jet axis, as expected. For multiple jets in one row (z/d = 2), again the v2–f showed the best overall agreement with the experimental data. The k–ω model is not as good while k–ε clearly overpredicts the Nusselt numbers. For multiple jets in three inline rows (z/d = 5), all the three models were in overall agreement with the experimental data. However, k–ε and k–ω exhibit an important phenomenon, reported by the experiments: a decrease of the stagnation Nu from the upstream jet to the downstream ones. The v2–f model did not reproduce this feature.

Experimental Investigation of Heat Transfer Augmentation by Different Jet Impingement Hole Shapes Under Maximum Crossflow

2016 ◽  
Author(s):  
Prashant Singh ◽  
Bharath Viswanath Ravi ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Jet Impingement ◽  
High Heat ◽  
Absolute Pressure ◽  
Target Plate ◽  
Heat Transfer Augmentation ◽  
Plate Spacing ◽  
High Heat Transfer ◽  
Heat Loads

To achieve higher overall efficiency in gas turbine engines, hot gas path components are subjected to high heat transfer loads due to higher turbine inlet temperatures. Jet impingement has been extensively used especially as an internal cooling technique in the leading edge and mid-chord region of first stage vanes, which are subjected to highest heat loads. With the advent of additive manufacturing methods such as Direct Metal Laser Sintering (DMLS), designers are not limited to designing round or race track holes for impingement. The present study is focused on exploring new jet hole shapes, in an arrangement, typical of mid-chord region in a double wall cooling configuration. Transient liquid crystal experiments are carried out to study heat transfer augmentation by jet impingement on smooth target where the spent air is allowed to exit in one direction, thus imposing maximum crossflow condition. The averaged Reynolds number (based on jet hydraulic diameter) is varied from 2500 to 10000. The jet plate has a square array of jets with 7 jets in one row (total number of jets = 49), featuring hole shapes — Racetrack and V, where the baseline case is the round hole. The non-dimensional streamwise (x/dj) and spanwise (y/dj) spacing is 6 and the normalized jet-to-target-plate spacing (z/dj) is 4 and the nozzle aspect ratio (L/dj) is also 4. The criteria for the hole shape design was to keep the effective area of different hole shapes to be the same, which resulted in slightly different hydraulic diameters. The jet-to-target plate spacing (z) has been adjusted accordingly so as to maintain a uniform z/dj of 4, across all three configurations studied. Heat transfer coefficients are measured using a transient Liquid Crystal technique employing a one-dimensional semi-infinite model. Flow experiments are carried out to measure static pressures in the plenum chamber, to calculate the discharge coefficient, for a range of plenum absolute pressure-to-ambient pressure ratios. Detailed normalized Nusselt number contours have been presented, to identify the regions of high heat transfer augmentation locally, so as to help the designers in the organization of jet hole shapes and their patterns in an airfoil depending upon the active heat loads.

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 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.

Heat Transfer and Pressure Investigation of Dimple Impingement

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
K. Kanokjaruvijit ◽  
R. F. Martinez-Botas
Keyword(s):  
Heat Transfer ◽  
Total Pressure ◽  
Static Pressure ◽  
Flat Surface ◽  
Target Plate ◽  
Round Jets ◽  
Plate Spacing ◽  
Parametric Effects ◽  
Wetted Area ◽  
Plate Geometry

Heat transfer and pressure results of an inline array of round jets impinging on a staggered array of dimples are reported with the consideration of various geometric and parametric effects; results are normalized against flat plate data. The heat transfer was measured by using transient wideband liquid crystal method. The geometrical configurations considered were crossflow (or spent-air exit) scheme, dimple geometries, and impinging positions. Three crossflow schemes were tested such as one-way, two-way, and free exits. These led to the idea of the coupling effects of impingement and channel flow depending on which one dominated. Hemispherical and cusped elliptical dimple shapes with the same wetted area were considered and found that both dimples showed the similarity in heat transfer results. Impinging positions on dimples and on flat portions adjacent to dimples were examined. Throughout the study, the pitch of the nozzle holes was kept constant at four jet diameters. The investigated parameters were Reynolds number (ReDj) ranged from 5000 to 11,500, jet-to-plate spacing (H∕Dj) varied from 1 to 12 jet diameters, dimple depths (d∕Dd) of 0.15, 0.25, and 0.29, and dimple curvature (Dj∕Dd) of 0.25, 0.50, and 1.15. The shallow dimples (d∕Dd=0.15) improved heat transfer significantly by 70% at H∕Dj=2 compared to that of the flat surface, while this value was 30% for the deep ones (d∕Dd=0.25). The improvement also occurred to the moderate and high Dj∕Dd. The total pressure was a function of ReDj and H∕Dj when H∕Dj<2, but it was independent of the target plate geometry. The levels of the total pressure loss of the dimpled plates werenot different from those of the flat surface under the same setup conditions. Wall static pressure was measured by using static taps located across each plate. ReDj and H∕Dj affected the level of the static pressure while the dimple depth influenced the stagnation peaks, and the crossflow scheme affected the shape of the peaks.

An experimental investigation of the heat transfer due to multiple jets impinging normally on a dimpled surface

2004 ◽  
Vol 218 (11) ◽  
pp. 1337-1347 ◽  
Author(s):  
K Kanokjaruvijit ◽  
R F Martinez-Botas
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Wide Band ◽  
Transfer Enhancement ◽  
Enhancement Of Heat Transfer ◽  
Flow Scheme ◽  
Plate Spacing ◽  
Multiple Jets ◽  
Dimple Surface ◽  
The Heat Transfer Coefficient

A dimpled surface, used as a turbulence promoter, was combined with jet impingement to investigate the potential for heat transfer enhancement. An eight-by-eight jet array was used to impinge a staggered dimple surface, both on the dimples themselves and on the flat portions adjacent to the dimples. The heat transfer coefficient was measured using the transient wide-band liquid crystal method. The jet-to-plate spacing (H/D) studied was 2, 4 and 8. Two dimple geometries were tested: hemispherical concavities and cusped elliptical shapes. All the results were normalized by those from a flat plate. The results varied depending on the H/D spacing and the flow scheme for the exit (one-way, two-way and four-way exits); the effect of geometry variation (hemispherical or cusp shapes) was secondary. The maximum exit flow scheme (four-way exit) achieved the highest enhancement of heat transfer. The combination of dimples and impingement can lead to significant enhancement, but careful optimization of the location of impingement would be required.

scholarly journals Local Heat Transfer Distributions in Confined Multiple Air Jet Impingement

2000 ◽  
Vol 123 (3) ◽  
pp. 165-172 ◽  
Author(s):  
Suresh V. Garimella ◽  
Vincent P. Schroeder
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Air Jets ◽  
Air Jet ◽  
Multiple Jets ◽  
Single Jet ◽  
Radial Outflow ◽  
Target Spacing

Heat transfer from a discrete heat source to multiple, normally impinging, confined air jets was experimentally investigated. The jets issued from short, square-edged orifices with still-developing velocity profiles on to a foil heat source which produced a constant heat flux. The orifice plate and the surface containing the heat source were mounted opposite each other in a parallel-plates arrangement to effect radial outflow of the spent fluid. The local surface temperature was measured in fine increments over the entire heat source. Experiments were conducted for different jet Reynolds numbers (5000<Re<20,000), orifice-to-target spacing 0.5<H/d<4, and multiple-orifice arrangements. The results are compared to those previously obtained for single air jets. A reduction in orifice-to-target spacing was found to increase the heat transfer coefficient in multiple jets, with this effect being stronger at the higher Reynolds numbers. With a nine-jet arrangement, the heat transfer to the central jet was higher than for a corresponding single jet. For a four-jet arrangement, however, each jet was found to have stagnation-region heat transfer coefficients that were comparable to the single-jet values. The effectiveness of single and multiple jets in removing heat from a given heat source is compared at a fixed total flow rate. Predictive correlations are proposed for single and multiple jet impingement heat transfer.

Investigation of Heat Transfer and Pressure Field of Jet Impingement on the Side of a Dimpled Surface

2017 ◽  
Author(s):  
Li-Jian Cheng ◽  
Wei-Jiang Xu ◽  
Hui-Ren Zhu ◽  
Ru Jiang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Loss ◽  
Flat Surface ◽  
Jet Impingement ◽  
Target Surface ◽  
Turbine Cooling ◽  
Pressure Loss Coefficient ◽  
Round Jets ◽  
Plate Spacing

An efficient way to improve the efficiency of the aero engine is to increase the temperature of the turbine inlet, which requires more advanced turbine cooling techniques. The dimple heat transfer enhancement is a technique that can enhance the convective heat transfer of the surfaces by processing a certain arrangement of jet holes and dimples on the surfaces. The objective of this paper is to investigate the characteristics of heat transfer and pressure loss for an inline array of round jets impinging on the side of dimpled surface. Meanwhile, the results are compared to those of the impingement directly over the dimples and the flat surface. The investigated parameters are Reynolds number (Re) of 5000, 8000 and 11500, the ratio of jet-to-plate spacing to jet diameter (H/Dj) of 2, 4, 6 and 8, the ratio of dimple depth to dimple diameter (d/Dd) of 0.15, 0.25 and 0.29. Results show that increasing the Reynolds number can improve the heat transfer. The shallower dimples enhance higher heat transfer than the deeper ones. For the target surface, the side impingement conducts the highest improvement at H/Dj = 8, d/Dd = 0.15 and Re = 11500. The improvement is about 16% higher than that of the frontal impingement while this value is 7% when compared to the flat surface. However, for the jet surface at the same operating condition, the side impingement leads to the worst heat transfer performance by 25% and 15% lower than that of the frontal impingement and the flat surface, respectively. The higher Reynolds number causes higher total pressure loss. But the pressure loss coefficient of the side impingement is not significantly different from that of the frontal impingement and the flat surface.

scholarly journals Jet Impingement Heat Transfer Characteristics with Variable Extended Jet Holes under Strong Crossflow Conditions

Aerospace ◽  
2022 ◽  
Vol 9 (1) ◽  
pp. 44
Author(s):  
Xing Yang ◽  
Hang Wu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Thermochromic Liquid Crystal ◽  
Pumping Power ◽  
Heat Transfer Characteristics ◽  
Target Plate ◽  
Transfer Characteristics

In this paper, detailed flow patterns and heat transfer characteristics of a jet impingement system with extended jet holes are experimentally and numerically studied. The jet holes in the jet plate present an inline array of 16 × 5 rows in the streamwise (i.e., the crossflow direction) and spanwise directions, where the streamwise and spanwise distances between adjacent holes, which are normalized by the jet hole diameter (xn/d and yn/d), are 8 and 5, respectively. The jets impinge onto a smooth target plate with a normalized distance (zn/d) of 3.5 apart from the jet plate. The jet holes are extended by inserting stainless tubes throughout the jet holes and the extended lengths are varied in a range of 1.0d–2.5d, depending on the jet position in the streamwise direction. The experimental data is obtained by using the transient thermochromic liquid crystal (TLC) technique for wide operating jet Reynolds numbers of (1.0 × 104)–(3.0 × 104). The numerical simulations are well-validated using the experimental data and provide further insight into the flow physics within the jet impingement system. Comparisons with a traditional baseline jet impingement scheme show that the extended jet holes generate much higher local heat transfer levels and provide more uniform heat transfer distributions over the target plate, resulting in the highest improvement of approximately 36% in the Nusselt number. Although the extended jet hole configuration requires a higher pumping power to drive the flow through the impingement system, the gain of heat transfer prevails over the penalty of flow losses. At the same pumping power consumption, the extended jet hole design also has more than 10% higher heat transfer than the baseline scheme.

Simulation of Single and Multiple Impinging Jet Cooling and Comparison With Experimental Data

2006 ◽  
Author(s):  
S. Gordeev ◽  
V. Heinzel ◽  
V. Slobodchuk
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Jet Cooling ◽  
Numerical Predictions ◽  
Impingement Heat Transfer ◽  
Commercial Code ◽  
Single Jet

A number of turbulence models offered by the commercial code STAR-CD have been tested on the measurements published in the literature with the objective to compare their capabilities for the simulation of a flow and heat transfer in multiple impinging jets. Numerical predictions of the single jet and jet array air impinging heat transfer have been compared with experimental data. The comparison shows that only turbulence models with additional limiters for turbulence production in the stagnation zone are able to correctly predict the jet impingement heat transfer. Suga’s k-ε turbulence model with Yap-correction, k-ε RNG, V2F and SST turbulence models with different near wall modifications are in acceptable agreement with experiments. The deviations from the experimental data, which provide all the turbulence models, are analyzed.

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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