HEAT TRANSFER AND PRESSURE DROP MEASUREMENTS IN COOLING CHANNELS WITH HELIUM AT A PRESSURE OF 20 BAR AND WITH WALL TEMPERATURES UP TO 1000 °C

1974 ◽  
Author(s):  
Helge Petersen ◽  
N. E. Kaiser
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cooling Channels

Topology Optimization of Serpentine Channels for Minimization of Pressure Loss and Maximization of Heat Transfer Performance As Applied for Additive Manufacturing

2019 ◽  
Author(s):  
Shinjan Ghosh ◽  
Jayanta S. Kapat
Keyword(s):  
Heat Transfer ◽  
Topology Optimization ◽  
Additive Manufacturing ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Blade Cooling

Abstract Gas Turbine blade cooling is an important topic of research, as a high turbine inlet temperature (TIT) essentially means an increase in efficiency of gas turbine cycles. Internal cooling channels in gas turbine blades are key to the cooling and prevention of thermal failure of the material. Serpentine channels are a common feature in internal blade cooling. Optimization methods are often employed in the design of blade internal cooling channels to improve heat-transfer and reduce pressure drop. Topology optimization uses a variable porosity approach to manipulate flow geometries by adding or removing material. Such a method has been employed in the current work to modify the geometric configuration of a serpentine channel to improve total heat transferred and reduce the pressure drop. An in-house OpenFOAM solver has been used to create non-traditional geometries from two generic designs. Geometry-1 is a 2-D serpentine passage with an inlet and 4 bleeding holes as outlets for ejection into the trailing edge. Geometry-2 is a 3-D serpentine passage with an aspect ratio of 3:1 and consists of two 180-degree bends. The inlet velocity for both the geometries was used as 20 m/s. The governing equations employ a “Brinkman porosity parameter” to account for the porous cells in the flow domain. Results have shown a change in shape of the channel walls to enhance heat-transfer in the passage. Additive manufacturing can be employed to make such unconventional shapes.

Numerical Investigation on Flow and Heat Transfer in Matrix Cooling Channels for Turbine Blades

2016 ◽  
Author(s):  
Yigang Luan ◽  
Shi Bu ◽  
Haiou Sun ◽  
Tao Sun
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Pressure Drop ◽  
Heat Transfer Performance ◽  
Structural Parameters ◽  
Turbine Blades ◽  
Channel Width ◽  
Transfer Performance ◽  
Cooling Channel ◽  
Cooling Channels

Matrix cooling is one kind of internal cooling structures applied to protect turbine blades. This paper investigated the flow field and heat transfer performance in matrix cooling channels experimentally and numerically. A testing section (rib angle of 45-deg, rib thickness of 30mm, rib height of 30mm and sub-channel width of 30mm) made of Plexiglas was build and connected to a wind tunnel sysytem. And Transient Liquid Crystal (TLC) technique was applied to obtain the detailed heat transfer distribution on the primary surface inside the matrix cooling channel. The experiment was performed under different Reynolds numbers varying from 18428 to 28327, based on the channel inlet hydraulic diameter; also the overall pressure drop across the channel was measured. Experimental results were used to calibrate the numerical solution obtained by computational fluid dynamics (CFD) method. During the numerical simulation process, structured grids and k-w turbulence model was employed. And a good agreement is obtained between experimental and CFD results for both pressure drop and heat transfer performance. Channels of various structural parameters (rib angle, rib thickness and sub-channel width) were then studied by numerical simulation, three rib angles (30-deg, 45-deg and 60-deg), three rib thicknesses (1.8mm, 3mm and 5mm) and three sub-channel widths (3mm, 5mm and 9mm) were considered, with the rib height 3mm for all the cases. Numerical results showed that the sidewall turnings made the greatest contribution to heat transfer enhancement but caused very large pressure drop meanwhile. The overall heat transfer and pressure drop increase with rib angle and rib width but decrease with sub-channel width. The thermal performance factor decreases with rib angle and rib width, while it showed a non-monotonic dependency on sub-channel width. Among the three structural parameters, rib angle has the most significant effect on the performance of matrix cooling channel.

Heat Transfer in Rotating, Trailing Edge, Converging Channels With Full and Partial Height Strip-Fins

2021 ◽  
Author(s):  
Izzet Sahin ◽  
I-Lun Chen ◽  
Lesley M. Wright ◽  
Je-Chin Han ◽  
Hongzhou Xu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Direction ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cooling Channels ◽  
Heat Transfer Coefficients ◽  
Pin Fins ◽  
Full Height

Abstract A wide variety of pin-fins have been used to enhance heat transfer in internal cooling channels. However, due to their large blockage in the flow direction, they result in an undesirable high pressure drop. This experimental study aims to reduce pressure drop while increasing the heat transfer surface area by utilizing strip-fins in converging internal cooling channels. The channel is designed with a trapezoidal cross-section, converges in both transverse and longitudinal directions, and is also skewed β = 120° with respect to the direction of rotation in order to model a trailing edge cooling channel. Only the leading and trailing surfaces of the channel are instrumented, and each surface is divided into eighteen isolated copper plates to measure the regionally averaged heat transfer coefficient. Utilizing pressure taps at the inlet and outlet of the channel, the pressure drop is obtained. Three staggered arrays of strip-fins are investigated: one full height configuration and two partial fin height arrangements (Sz = 2mm and 1mm). In all cases, the strip fins are 2mm wide (W) and 10mm long (Lf) in the flow direction. The fins are spaced such that Sy/Lf = 1 in the streamwise direction. However, due to the convergence the spanwise spacing Sx/W, was varied from 8 to 6.2 along the channel. The rotation number of the channel varied up to 0.21 by ranging the inlet Reynolds number from 10,000 to 40,000 and rotation speed from 0 to 300rpm. It is found that the full height strip-fin channel results in a more non-uniform spanwise heat transfer distribution than the partial height strip-fin channel. Both trailing and leading surface heat transfer coefficients are enhanced under rotation conditions. The 2mm height partial strip-fin channel provided the best thermal performance, and it is comparable to the performance of the converging channels with partial length circular pins. The strip-fin channel can be a design option when the pressure drop penalty is a major concern.

Bend Geometries in Internal Cooling Channels for Improved Thermal Performance

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Krishnendu Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Thermal Performance ◽  
Local Heat Transfer ◽  
Outer Wall ◽  
Local Heat ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Baseline Case ◽  
Sharp Turn

The pressure drop and heat transfer in a two pass internal cooling channel with two different bend geometries is experimentally studied with the goal of improving the thermal performance factor (TPF) in the coolant channel. The geometries studied are (1) a baseline U-bend geometry with a rectangular divider wall, (2) a symmetrical bulb at the end of the divider wall, and (3) a combination of the symmetrical bulb and a bow on the opposite outer wall leading to a shaped flow contraction and expansion in the bend. Tests are conducted for four Reynolds number ranging from 10,000 to 55,000. The symmetrical bulb eliminates the separation due to the sharp turn and makes the heat transfer distribution in the bend portion more uniform. This modification reduces the bend pressure drop by 37% and augments the TPF by nearly 29% compared to the baseline case. The combination of bulb and bow case increases the local heat transfer in the bend region significantly, and reduces the bend pressure drop by nearly 27% leading to an augmentation of the TPF of 32% compared to the baseline case. These improvements in TPF point to the benefits of using the improved bend designs in internal cooling channels.

Numerical Comparison of Heat Transfer and Pressure Drop in Gas Turbine Blade Cooling Channels With Dimples and Rib-Turbulators

2011 ◽  
Author(s):  
R. S. Amano ◽  
Krishna S. Guntur ◽  
Sourabh Kumar ◽  
Jose Martinez Lucci
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Pressure Loss ◽  
Reynolds Numbers ◽  
Reynolds Stress Model ◽  
Numerical Comparison ◽  
Turbine Blade Cooling ◽  
Cooling Channels ◽  
Rib Turbulators

In order to enhance the performance of a gas turbine and to maintain the blade material within operating temperature range, cooling channels are made within the blade materials that extract the heat. The walls of these cooling channels are usually enhanced with some sort of turbulence generators — ribs and dimples being the most common. While both the geometries provide improvement in enhancing the heat transfer, dimples usually have a lower pressure drop. It is essential to improve the heat transfer rate with a minimal pressure loss. In this study, the heat transfer and pressure loss are determined numerically and combined to show the effect of both in channels with ribs and dimples on one wall of the channel. Similar geometric and boundary conditions are used for both the turbulators. Reynolds numbers of 12,500 and 28,500, based on the hydraulic diameter are used for the study. The Reynolds-Stress Model was used for all the computations as a turbulence model by employing Fluent.

Heat Transfer to Suspensions of Microencapsulated Phase Change Material Flowing Through Minichannels

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Frank Dammel ◽  
Peter Stephan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Phase Change ◽  
Melting Temperature ◽  
Phase Change Material ◽  
Latent Heat ◽  
Particle Mass ◽  
Cooling Channels ◽  
Microencapsulated Phase Change Material ◽  
Change Material

The heat transfer to water-based suspensions of microencapsulated phase change material (MEPCM) flowing laminarly through rectangular copper minichannels was investigated both experimentally and numerically. The MEPCM-particles had an average size of 5 μm and contained as phase change material n-eicosane, which has a theoretical melting temperature of 36.4 °C. Water and suspensions with particle mass fractions of 10% and 20% were considered. While the experiments result in rather global values such as wall temperatures at certain points, suspension in- and outlet temperatures, and the pressure drop, the numerical simulations allow additionally a more detailed insight, for example, into the temperature distribution in the flowing suspension. The results show that MEPCM suspensions are only advantageous in comparison to water in a certain range of parameter combinations, where the latent heat is exploited to a high degree. The available latent heat storage potential, which depends on the particle fraction in the suspension and on the mass flow rate, has to be in the same order of magnitude as the supplied heat. Moreover, the mean residence time of the particles in the cooling channels must not be considerably shorter than the characteristic time for heat conduction perpendicular to the flow direction. Otherwise, the particles in the center region of the flow leave the cooling channels with still solid cores, and their latent heat is not exploited. Furthermore, the benefit of the added MEPCM particles depends on the inlet temperature, which has to be slightly below the theoretical melting temperature, and on the subcooling temperature after the heat supply, which has to be sufficiently low to guarantee that the entire phase change material solidifies again before it re-enters the cooling channels. The suspensions showed Newtonian behavior in the viscosity measurement. The actual pressure drop determined in the experiments is smaller than the pressure drop estimation based on the measured viscosities. The difference between the two values increases with increasing particle mass fraction. This shows that the particles are not evenly distributed in the flowing suspension, but that there is a particle-depleted layer close to the channel walls. This reduces the required pumping power, but makes it even more important to provide conditions, in which a sufficiently large amount of the supplied heat is conducted to the center region of the channels.

Optimization of Hybrid-Linked Jet Impingement Cooling Channels Based on Response Surface Methodology and Genetic Algorithm

2017 ◽  
Author(s):  
Li Yang ◽  
Zheng Min ◽  
Sarwesh Narayan Parbat ◽  
Minking K. Chyu
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Response Surface Methodology ◽  
Pressure Drop ◽  
Response Surface ◽  
Flow Rate ◽  
Jet Impingement ◽  
Optimization Strategy ◽  
Impingement Cooling ◽  
Cooling Channels

In recent years, development of new manufacturing technologies like additive manufacturing has made it possible to make complex cooling structures to improve the efficiency of jet impingement. Present paper considers hybrid-linked jet impingement cooling channels which involve both parallel linked jets and serial linked jets. Systematic analysis was conducted with the aid of Computational Fluid Dynamics and Response Surface Methodology, focusing on the influence of topology on performance. An optimization platform was established with aid of the regressed database and the Genetic Algorithm. Of particular interest is the influence of optimization strategies on results. Results obtained indicates that the topology number developed in this study works well with the Response Surface Methodology. Topology can be considered to be a new degree of freedom of jet impingement design. Among the tested topologies, serial linked jet impingement has significantly higher heat transfer and pressure drop than the traditional parallel linked jet impingement. In the first optimization strategy, mass flow rate was used as the objective function while heat transfer and pressure drop were constrained. Optimized results under this strategy show consistent parameters and purely serial linked topology for all cases, due to the high cooling efficiency of serial linked jets. In the second optimization strategy, pressure drop was minimized while heat transfer and mass flow rate were constrained. Contrast with the first strategy, optimal results of this strategy have different topologies under different constraint conditions, which is caused by the complex influence of geometric parameters on pressure drop. Such results indicate the capability of hybrid-linked jet impingement to fit a wide various requirement by changing topology.

Heat Transfer to Suspensions of Microencapsulated Phase Change Material (MEPCM) Flowing Through Minichannels

2010 ◽  
Author(s):  
Frank Dammel ◽  
Peter Stephan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Phase Change ◽  
Melting Temperature ◽  
Phase Change Material ◽  
Latent Heat ◽  
Particle Mass ◽  
Cooling Channels ◽  
Microencapsulated Phase Change Material ◽  
Change Material

The heat transfer to water-based suspensions of microencapsulated phase change material (MEPCM) flowing laminarly through rectangular copper minichannels was investigated both experimentally and numerically. The MEPCM-particles had an averags size of 5μm and contained as phase change material neicosane, which has a theoretical melting temperature of 36.4°C. Water and suspensions with particle mass fractions of 10% and 20% were considered. While the experiments result in rather global values such as wall temperatures at certain points, suspension in- and outlet temperatures and the pressure drop, the numerical simulations allow additionally a more detailed insight for example into the temperature distribution in the flowing suspension. The results show that MEPCM suspensions are only advantageous in comparison to water in a certain range of parameter combinations, where the latent heat is exploited to a high degree. The available latent heat storage potential, which depends on the particle fraction in the suspension and on the mass flow rate, has to be in the same order of magnitude as the supplied heat. Moreover, the mean residence time of the particles in the cooling channels must not be considerably shorter than the characteristic time for heat conduction perpendicular to the flow direction. Otherwise the particles in the center region of the flow leave the cooling channels with still solid cores and their latent heat is not exploited. Furthermore, the benefit of the added MEPCM particles depends on the inlet temperature, which has to be slightly below the theoretical melting temperature, and on the subcooling temperature after the heat supply, which has to be sufficiently low to guarantee that the entire phase change material solidifies again before it reenters the cooling channels. The suspensions showed Newtonian behavior in the viscosity measurement. The actual pressure drop determined in the experiments is smaller than the pressure drop estimation based on the measured viscosities. The difference between the two values increases with increasing particle mass fraction. This shows that the particles are not evenly distributed in the flowing suspension, but that there is a particle depleted layer close to the channel walls. This reduces the required pumping power, but makes it even more important to provide conditions, in which a sufficiently large amount of the supplied heat is conducted to the center region of the channels.

Computational Study of Flow and Heat Transfer in Matrix Cooling Channels

2014 ◽  
Author(s):  
Sivasankara Reddy Ramireddy ◽  
Siddappa Pallavagere Gurusiddappa ◽  
V. Kesavan ◽  
S. Kishore Kumar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Numerical Study ◽  
Computational Study ◽  
Side Wall ◽  
Transfer Enhancement ◽  
Cooling Channels ◽  
Aspect Ratios ◽  
The Matrix

A Numerical study of fluid flow, heat transfer and pressure drop in a stationary matrix cooling channel having an angle of 45 degrees for the three Reynolds numbers (24000<Re<60000) and four sub-channel aspect ratios (0.5<W/H<1.2) have been performed. This includes different shaped sub-channels such as Rectangular, U, and then two, three layered matrix combined with open and closed matrix channels. The simulation shows the development of vortices along the channel. The flow turning and impingement after hitting the side wall have significant contribution to the heat transfer enhancement. The Nusselt number and friction factor have been evaluated and compared with limited experimental results. The highest heat transfer enhancement is found at impingement region as the flow takes turn and impinges on to the wall. But slight enhancement in heat transfer is observed at turning region. The sub-channel aspect ratio has less impact on heat transfer enhancement, but more effect on pressure drop. The performance of closed matrix is relatively better than the open matrix one. The overall thermal performance (η) of the matrix having U sub-channel is nearly 10% higher than the rectangular sub-channel.

HEAT TRANSFER IN ROTATING, TRAILING EDGE, CONVERGING CHANNELS WITH FULL AND PARTIAL HEIGHT STRIP-FINS

2022 ◽  
pp. 1-32
Author(s):  
Izzet Sahin ◽  
I-Lun Chen ◽  
Lesley Wright ◽  
Je-Chin Han ◽  
Hongzhou Xu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Rotation Speed ◽  
Flow Direction ◽  
Internal Cooling ◽  
Enhance Heat Transfer ◽  
Trailing Edge ◽  
Cooling Channels ◽  
Pin Fins ◽  
Full Height

Abstract A wide variety of pin-fins have been used to enhance heat transfer in internal cooling channels. However, due to their large blockage in the flow direction, they result in an undesirable high pressure drop. This experimental study aims to reduce pressure drop while increasing the heat transfer surface area by utilizing strip-fins in converging internal cooling channels. The channel is designed with a trapezoidal cross-section, converges in both transverse and longitudinal directions, and is also skewed β=120° with respect to the direction of rotation in order to model a trailing edge cooling channel. Only the leading and trailing surfaces of the channel are instrumented, and each surface is divided into eighteen isolated copper plates to measure the regionally averaged heat transfer coefficient. Utilizing pressure taps at the inlet and outlet of the channel, the pressure drop is obtained. Three staggered arrays of strip-fins are investigated: one full height configuration and two partial fin height arrangements (Sz=2mm and 1mm). In all cases, the strip fins are 2mm wide (W) and 10mm long (Lf ) in the flow direction. The fins are spaced such that Sy/Lf = 1 in the streamwise direction. However, due to the convergence, the spanwise spacing, Sx/W, was varied from 8 to 6.2 along the channel. The rotation number of the channel varied up to 0.21 by ranging the inlet Reynolds number from 10,000 to 40,000 and rotation speed from 0 to 300rpm. It is found that

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