Computational Investigation of Flow and Heat Transfer Characteristics of Impingement Cooling Channel

Impingement cooling offers very high heat transfer coefficients. Flow field, involved in impingement cooling is dominated by stagnation zone, transition zone and developing zone. Understanding of complex flow phenomenon and its effects on heat transfer characteristics is useful for efficient designing of impingement channels. Computational fluid dynamics (CFD) has emerged as a powerful tool for the analysis of flow and heat transfer systems. Honeywell has been investigating the use of CFD to determine the characteristics of various complex turbine blade cooling heat transfer augmentation methods such as impingement. The objective of this study is to develop CFD methodology which is suitable for computational investigation of flow and heat transfer analysis of impingement cooling through validation. Single row of circular jets impinging on concave (curved) surface has been considered for this study. The validation was accomplished with the test results of Bunker and Metzger [10] and with the correlations of Chupp et al. [7]. The parameters which are varied in this study include jet Reynolds number (Re2B = 6750–10200), target plate distance to jet diameter ratio (Z/d = 3 and 4), and target surface sharpness (i.e. radius ratio, r* = 0.2, 0.4 and 1) the simulations are performed under steady state conditions. Predicted results are compared for local endwall heat transfer results along the curve length of the mid span target wall. Flow field results obtained at different locations are presented to understand the heat transfer behavior.

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

Energies ◽

10.3390/en14144327 ◽

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.

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Effect of Turbulent Intensity and Axial Gap on Turbine Heat Transfer Using Steady and Harmonic Models

Volume 6B: Turbomachinery ◽

10.1115/gt2013-94600 ◽

2013 ◽

Author(s):

Sridhar Murari ◽

Sunnam Sathish ◽

Ramakumar Bommisetty ◽

Jong S. Liu

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Flow Field ◽

Turbulence Intensity ◽

Pressure Coefficient ◽

Heat Transfer Characteristics ◽

Complex Flow ◽

Transfer Characteristics ◽

Flow And Heat Transfer ◽

Heat Loads

The knowledge of heat loads on the turbine is of great interest to turbine designers. Turbulence intensity and stator-rotor axial gap plays a key role in affecting the heat loads. Flow field and associated heat transfer characteristics in turbines are complex and unsteady. Computational fluid dynamics (CFD) has emerged as a powerful tool for analyzing these complex flow systems. Honeywell has been exploring the use of CFD tools for analysis of flow and heat transfer characteristics of various gas turbine components. The current study has two objectives. The first objective aims at development of CFD methodology by validation. The commercially available CFD code Fine/Turbo is used to validate the predicted results against the benchmark experimental data. Predicted results of pressure coefficient and Stanton number distributions are compared with available experimental data of Dring et al. [1]. The second objective is to investigate the influence of turbulence (0.5% and 10% Tu) and axial gaps (15% and 65% of axial chord) on flow and heat transfer characteristics. Simulations are carried out using both steady state and harmonic models. Turbulence intensity has shown a strong influence on turbine blade heat transfer near the stagnation region, transition and when the turbulent boundary layer is presented. Results show that a mixing plane is not able to capture the flow unsteady features for a small axial gap. Relatively close agreement is obtained with the harmonic model in these situations. Contours of pressure and temperature on the blade surface are presented to understand the behavior of the flow field across the interface.

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Influences of Small Jet-to-Wall Spacings on Heat Transfer Characteristics and Flow-Field Entrainment Effects of Microscale Jets

Journal of Electronic Packaging ◽

10.1115/1.4049579 ◽

2021 ◽

Vol 143 (3) ◽

Author(s):

Prabhakar Subrahmanyam ◽

B. K. Gnanavel

Keyword(s):

Heat Transfer ◽

Flow Field ◽

Jet Impingement ◽

Impinging Jets ◽

Heat Transfer Characteristics ◽

Transfer Coefficients ◽

Inlet System ◽

Potential Core ◽

Transfer Characteristics ◽

The Impact

Abstract Detailed heat transfer distributions of multiple microscaled tapered jets orthogonally impinging on the surface of a high-power density silicon wall is presented. The tapered jets issued from two different impingement setup are studied—(a) single circular nozzle and (b) dual circular nozzles. Jets are issued from the inlet(s) at four different Reynolds numbers {Re = 8000, 12,000, 16,000, 20,000}. The spacing between the tapered nozzle jets and the bare die silicon wall (z/d) is adjusted to be 4, 8, 12, and 16 jet nozzle diameters away from impinging influence. The impact of varying the nozzle to the silicon wall (z/d) standoff spacing up to 16 nozzle jet diameters and its effects on flow fields on the surface of the silicon, specifically the entrainment pattern on the silicon surface, is presented. Heat transfer characteristics of impinging jets on the hot silicon wall is investigated by means of large eddy simulations (LES) at a Reynolds of 20,000 on each of the four z/d spacing and compared against its equivalent Reynolds-averaged Navier–Stokes (RANS) cases. Highest heat transfer coefficients are obtained for the dual inlet system. A demarcation boundary region connecting all the microvortices between impinging jets is prominently visible at smaller z/d spacing—the region where the target silicon wall is within the sphere of influence of the potential core of the jet. This research focuses on the underlying physics of multiple tapered nozzles jet impingement issued from single and dual nozzles and its impact on turbulence, heat transfer distributions, entrainment, and other pertinent flow-field characteristics.

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Detailed Studies on the Flow Field and Heat Transfer Characteristics Inside a Realistic Serpentine Cooling Channel With a S-Shaped Inlet

Volume 5B: Heat Transfer ◽

10.1115/gt2018-76225 ◽

2018 ◽

Cited By ~ 2

Author(s):

Ken-ichi Funazaki ◽

Hikaru Odagiri ◽

Takeshi Horiuchi ◽

Masahide Kazari

Keyword(s):

Heat Transfer ◽

Flow Field ◽

Flow Visualization ◽

Gas Turbine ◽

Turbine Blade ◽

Cooling Channel ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Flow And Heat Transfer ◽

Inner Surface

Accurate temperature prediction of turbine blades for gas turbine is very important to assure the life-span of the blade under a hostile hot gas environment and intense centrifugal force. Therefore, there have been a number of studies carried out to clarify the cooling performance of serpentine cooling channel inside a turbine blade for gas turbine, however, it remains to be quite difficult to make an accurate numerical prediction of the performance. Apart from the effects of disk rotation as well as large temperature gradient near the wall, such a poor predictability can be attributed to the complicated vortical motions caused by the rib-roughened cooling channel whose cross-sectional shape varies along the channel and by the existence of u-bends. Furthermore, since the cooling channel inside a real turbine blade usually has a curved or S-shaped inlet, which may induce flow separation as well as swirl developed in the inlet, it can be imagined that the flow and heat transfer inside the cooling channel is likely to become much more complicated than that with a straight inlet. Despite this situation, only few studies are made in order to examine the flow and heat transfer characteristics inside the cooling channel with s-shaped inlet. Accordingly, this study aims at detailed experimental and numerical investigations on the flow and heat transfer characteristics of a realistic serpentine rib-roughened cooling channel with an s-shaped inlet, which is modeled from an actual HP turbine blade for gas turbine. This study employs a transient TLC (Thermochromic Liquid Crystal) technique to measure the heat transfer characteristics, along with the flow visualization on the inner surface of the channel using oil mixed with titanium powder. Note that a special focus in this flow visualization is placed on the area of s-shaped inlet. As for the flow measurement, 2D-PIV (Particle Image Velocimetry) method is used to understand time-dependent vortical structures of the flow field that can have significant impacts on the heat transfer. RANS-based numerical simulation is also executed to predict the heat transfer distribution on the inner surface of the cooling channel.

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Numerical Study on Flow and Heat Transfer Characteristics of Jet Impingement

Volume 5: Heat Transfer, Parts A and B ◽

10.1115/gt2011-45287 ◽

2011 ◽

Cited By ~ 1

Author(s):

Xinjun Wang ◽

Rui Liu ◽

Xiaowei Bai ◽

Jinling Yao

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Nusselt Number ◽

Average Nusselt Number ◽

Jet Impingement ◽

Target Surface ◽

Heat Transfer Characteristics ◽

Impingement Cooling ◽

Transfer Characteristics ◽

Flow And Heat Transfer

A mathematical model used for studying jet impingement cooling characteristics is established, and the rationality of the calculation model and method is confirmed by the experimental data. The CFX software is used to numerically simulate the jet impingement cooling characteristics on a gas turbine blade. The effects of various parameters, such as the arrays of impinging nozzles, the jet Reynolds number, the jet-to-jet distance, the ratio of nozzle-to-surface spacing to jet diameter H/d, and the radius of curvature of the target surface, on the flow and heat transfer characteristics of a impingement cooling process are studied. The results indicate that the impingement jets can make complex vortex in the cooling channel, the flow boundary layer is extremely thin and highly turbulent. Underneath each impingement nozzle, there will appear a low temperature area and a peak of Nusselt number on the impingement target surface, the distribution of temperature and Nusselt number on the target surface are associated with arrangement of impingement nozzles. The average Nusselt number of the in-line arrangement nozzles is higher than that of the staggered arrangement ones. With the increasing of jet Reynolds number, the velocity impinging on the target surface and Nusselt number increase. However, heat transfer of impingement cooling on target surface is not sensitive to the jet nozzles distance; the velocity impinging on the target surface and Nusselt number decrease with the increasing of the H/d value. For the curved target surface cases, the average Nusselt number of the target surface and the effect of heat transfer decreased with the increasing of curvature radius R.

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Experimental Investigation of the Flow and Heat Transfer Characteristics in Microchannel Heat Exchangers with Reentrant Cavities

Micromachines ◽

10.3390/mi11040403 ◽

2020 ◽

Vol 11 (4) ◽

pp. 403 ◽

Cited By ~ 1

Author(s):

Binghuan Huang ◽

Haiwang Li ◽

Tiantong Xu

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Heat Exchangers ◽

Volume Ratio ◽

High Heat ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Flow And Heat Transfer ◽

High Heat Transfer ◽

The Impact

The application of microchannel heat exchangers is of great significance in industrial fields due to their advantages of miniaturized scale, large surface-area-to-volume ratio, and high heat transfer rate. In this study, microchannel heat exchangers with and without fan-shaped reentrant cavities were designed and manufactured, and experiments were conducted to investigate the flow and heat-transfer characteristics. The impact rising from the radius of reentrant cavities, as well as the Reynolds number on the heat transfer and the pressure drop, is also analyzed. The results indicate that, compared with straight microchannels, microchannels with reentrant cavities could enhance the heat transfer and, more importantly, reduce the pressure drop at the same time. For the ranges of parameters studied, increasing the radius of reentrant cavities could augment the effect of pressure-drop reduction, while the corresponding variation of heat transfer is complicated. It is considered that adding reentrant cavities in microchannel heat exchangers is an ideal approach to improve performance.

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Research on External Flow and Heat Transfer Characteristics of H-Type Fin Tube Based on Longitudinal Vortex

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.614.133 ◽

2014 ◽

Vol 614 ◽

pp. 133-137 ◽

Cited By ~ 1

Author(s):

Bo Jiang ◽

Wei Dong Hao ◽

Zhi Hong Hu ◽

Fu Guo Liu

Keyword(s):

Heat Transfer ◽

Flow Field ◽

Heat Transfer Performance ◽

External Flow ◽

Longitudinal Vortex ◽

Transfer Performance ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Flow And Heat Transfer ◽

Fin Tube

An H-type fin tube based on longitudinal vortex for boiler economizer is put forward in this paper, in order to solve the problem of too high temperature for denitration catalyst reaction for flue gas leaving the econonmizer. CFD method is adopted to study the external flow and heat transfer characteristics of the H-type fin tube based on longitudinal vortex, obtaining the flow field and temperature field distribution in the near wall region outside the fin tube. The results show that vortex flow in different degrees occurs in the rear flow field of the H-type fin tube based on longitudinal vortex, which introduces velocity component normal to main stream direction to the fluid of main flow zone, improves the synergy of temperature gradient field with velocity field and significantly enhances heat transfer performance of the fin tube. Within the parameter range studied in this paper, the 30° attack angle makes the best PEC value and correspondingly best comprehensive heat transfer performance.

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Flow and Heat Transfer Characteristics of a Swirling Impinging Jet Issuing from a Threaded Nozzle of 45 Degrees

Energies ◽

10.3390/en14248412 ◽

2021 ◽

Vol 14 (24) ◽

pp. 8412

Author(s):

Liang Xu ◽

Tao Yang ◽

Yanhua Sun ◽

Lei Xi ◽

Jianmin Gao ◽

...

Keyword(s):

Heat Transfer ◽

Flow Field ◽

Heat Transfer Rate ◽

Transfer Rate ◽

Impinging Jet ◽

Heat Transfer Characteristics ◽

Complex Flow ◽

Effective Measure ◽

Transfer Characteristics ◽

High Heat Transfer

In order to achieve uniform and effective impingement cooling, a swirling jet with a swirling angle of 45° (SIJ 45°) is put forward in this paper. Namely, there are four 45° spiral grooves equipped on the inner wall of the circular hole. The difference in the flow field and heat transfer characteristics between the conventional impinging jet (CIJ) and SIJ 45° is compared and analyzed. The spiral channels can increase the heat transfer rate and cooling uniformity because of the action of superimposed airflow. In addition, the thread nozzle brings lower pressure loss, which can reduce the airflow friction while effectively ensuring high heat transfer in the center area of the jet. An experimental system is built to investigate the heat transfer and flow characteristics of the impingement surface. Smoke flow visualization technology is used to explore the complex flow field of the CIJ and SIJ 45°, and the heat transfer rate of the target surface is analyzed based on thermocouple data. When 6000≤Re≤30,000, and 1≤h/dj≤8, the averaged Nusselt number (Nu) correlation for SIJ 45° is established, which is in good agreement with the experimental results. SIJ 45° is an effective measure to replace the CIJ, and the research herein provides some reference for designing the structure of new jets.

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