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9 pages, 1447 KiB

Open AccessArticle

Development of Solutions for Increasing the Combustion Efficiency of Hydrogen in Water Vapor in a Hydrogen-Oxygen Steam Superheater

by Andrey Rogalev, Nikolay Rogalev, Daria Kharlamova, Ivan Shcherbatov and Timofey Karev

Inventions 2023, 8(1), 6; https://doi.org/10.3390/inventions8010006 - 27 Dec 2022

Cited by 3 | Viewed by 2312

Abstract

The study is aimed at revealing the specific features of the burning of hydrogen with oxygen in a water-vapor atmosphere. The purpose of the study is to define the optimal values for diluting the burning mixture with water vapor in the active burnout [...] Read more.

The study is aimed at revealing the specific features of the burning of hydrogen with oxygen in a water-vapor atmosphere. The purpose of the study is to define the optimal values for diluting the burning mixture with water vapor in the active burnout zone, providing the minimal values of incomplete combustion. Modeling of burning processes was carried out with the use of kinetic mechanisms in the Ansys Chemkin-Pro software. The result of the study was the definition of critical water vapor content in a burning mixture as 60% fraction of total mass with, obtaining dependencies of key parameters of the burning process within a wide range. The mechanism of chemical kinetics was selected for further modeling in a three-dimensional setting, and tasks for the formulation of requirements and methods for the design of efficient hydrogen combustion chambers were set up for 500 MW gas turbine plants at a supercritical pressure of 20 MPa or higher. Full article

(This article belongs to the Special Issue Heat transfer and Thermal Managements of Innovative Systems)

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14 pages, 4653 KiB

Open AccessArticle

Asymmetric Method of Heat Transfer Intensification in Radial Channels of Gas Turbine Blades

by Sergey Osipov, Andrey Rogalev, Nikolay Rogalev, Igor Shevchenko and Andrey Vegera

Inventions 2022, 7(4), 117; https://doi.org/10.3390/inventions7040117 - 7 Dec 2022

Cited by 1 | Viewed by 1470

Abstract

Loop and semi-loop cooling schemes are widely used for the high-temperature gas turbine blades. In such schemes, the mid-chord airfoil parts are traditionally cooled by radial channels with ribbed walls. The blades with a small specific span, or “short” blades, have different heat [...] Read more.

Loop and semi-loop cooling schemes are widely used for the high-temperature gas turbine blades. In such schemes, the mid-chord airfoil parts are traditionally cooled by radial channels with ribbed walls. The blades with a small specific span, or “short” blades, have different heat flux amounts on pressure and suction sides, which results in a temperature difference in these sides of 100–150 °K. This difference causes thermal stresses and reduces the long-term strength margins. This paper presents a new method of heat transfer intensification in the ribbed radial cooling channels. The method is based on air streams’ injection through holes in the ribs that split channels. The streams are directed along the walls into the stagnation zones behind the ribs. The results of a 3D coolant flow simulation with ANSYS CFX code show the influence of the geometry parameters upon the channel heat transfer asymmetry. In the Reynolds number within a range of 6000–20,000, the method provides the heat transfer augmentation difference by up to 40% on the opposite channel walls. Test results presented in the criteria relations form allow for the calculation of mean the heat transfer coefficient along the channel length. Full article

(This article belongs to the Special Issue Heat transfer and Thermal Managements of Innovative Systems)

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15 pages, 1146 KiB

Open AccessArticle

Improved General Correlation for Condensation in Channels

by Mirza M. Shah

Inventions 2022, 7(4), 114; https://doi.org/10.3390/inventions7040114 - 2 Dec 2022

Cited by 6 | Viewed by 2081

Abstract

The present author’s general correlation for condensation in mini and macro channels which has been verified with an extreme range of data was further evaluated at quality x close to 1. Large deviations were found at quality x ≥ 0.99. The correlation was [...] Read more.

The present author’s general correlation for condensation in mini and macro channels which has been verified with an extreme range of data was further evaluated at quality x close to 1. Large deviations were found at quality x ≥ 0.99. The correlation was modified to improve the accuracy in this range of quality. The improved correlation has a MAD (mean absolute deviation) of 22.1% in this range of quality compared to 95% in the published correlation. This improvement is important for the calculation of heat transfer in the condensation of superheated vapor as it requires the value of the heat transfer coefficient at quality x = 1. The new correlation is presented together with a comparison of data. Various aspects of the correlation are discussed. Results of the comparison of all data with the new correlation as well as other correlations are given. Full article

(This article belongs to the Special Issue Heat transfer and Thermal Managements of Innovative Systems)

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19 pages, 5887 KiB

Open AccessArticle

Development of a Double Skin Facade System Applied in a Virtual Occupied Chamber

by Eusébio Conceição, João Gomes, Maria Manuela Lúcio and Hazim Awbi

Inventions 2021, 6(1), 17; https://doi.org/10.3390/inventions6010017 - 4 Mar 2021

Cited by 1 | Viewed by 3258

Abstract

In this study a system constituted by seven double skin facades (DSF), three equipped with venetian blinds and four not equipped with venetian blinds, applied in a virtual chamber, is developed. The project will be carried out in winter conditions, using a numerical [...] Read more.

In this study a system constituted by seven double skin facades (DSF), three equipped with venetian blinds and four not equipped with venetian blinds, applied in a virtual chamber, is developed. The project will be carried out in winter conditions, using a numerical model, in transient conditions, and based on energy and mass balance linear integral equations. The energy balance linear integral equations are used to calculate the air temperature inside the DSF and the virtual chamber, the temperature on the venetian blind, the temperature on the inner and outer glass, and the temperature distribution in the surrounding structure of the DSF and virtual chamber. These equations consider the convection, conduction, and radiation phenomena. The heat transfer by convection is calculated by natural, forced, and mixed convection, with dimensionless coefficients. In the radiative exchanges, the incident solar radiation, the absorbed solar radiation, and the transmitted solar radiation are considered. The mass balance linear integral equations are used to calculate the water mass concentration and the contaminants mass concentration. These equations consider the convection and the diffusion phenomena. In this numerical work seven cases studies and three occupation levels are simulated. In each case the influence of the ventilation airflow and the occupation level is analyzed. The total number of thermal and indoor air quality uncomfortable hours are used to evaluate the DSF performance. In accordance with the obtained results, in general, the indoor air quality is acceptable; however, when the number of occupants in the virtual chamber increases, the Predicted Mean Vote index value increases. When the airflow rate increases the total of Uncomfortable Hours decreases and, after a certain value of the airflow rate, it increases. The airflow rate associated with the minimum value of total Uncomfortable Hours increases when the number of occupants increases. The energy production decreases when the airflow increases and the production of energy is higher in DSF with venetian blinds system than in DSF without venetian blinds system. Full article

(This article belongs to the Special Issue Heat transfer and Thermal Managements of Innovative Systems)

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26 pages, 12588 KiB

Open AccessArticle

Near-Field Simulations of Film Cooling with a Modified DES Model

by Feiyan Yu and Savas Yavuzkurt

Inventions 2020, 5(1), 13; https://doi.org/10.3390/inventions5010013 - 10 Mar 2020

Cited by 6 | Viewed by 4021

Abstract

Modeling the heat transfer characteristics of highly turbulent flow in gas turbine film cooling is important for providing better insights and engineering solutions to the film cooling problem. This study proposes a modified detached eddy simulation (DES) model for better film cooling simulations. [...] Read more.

Modeling the heat transfer characteristics of highly turbulent flow in gas turbine film cooling is important for providing better insights and engineering solutions to the film cooling problem. This study proposes a modified detached eddy simulation (DES) model for better film cooling simulations. First, spatially varying anisotropic eddy viscosity is found from the results of the large eddy simulation (LES) of film cooling. Then the correlation for eddy viscosity anisotropy ratio has been established based on the LES results and is proposed as the modification approach for the DES model. The modified DES model has been tested for the near-field film cooling simulations under different blowing ratios. Detailed comparisons of the centerline and 2D film cooling effectiveness indicate that the modified DES model enhances the spanwise spreading of the temperature field. The DES model leads to deviations of 62.4%, 39.8%, and 33.5% from the experimental centerline effectiveness under blowing ratios of 0.5, 1.0, and 1.5, respectively, while the modified DES reduces the deviations to 51.5%, 26.7%, and 28.9%. The modified DES model provides a promising approach for film cooling numerical simulations. It embraces the advantage of LES in resolving detailed vortical structure dynamics with a moderate computational cost. It also significantly improves the original DES model on the spanwise counter rotating vortex pair (CRVP) spreading, mixing, and effectiveness prediction. Full article

(This article belongs to the Special Issue Heat transfer and Thermal Managements of Innovative Systems)

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25 pages, 10249 KiB

Open AccessArticle

Heat Transfer and Thermal Management of Interior Permanent Magnet Synchronous Electric Motor

by Pey-Shey Wu, Min-Fu Hsieh, Wei Ling Cai, Jen-Hsiang Liu, Yun-Ting Huang, Jose Fernando Caceres and Shyy Woei Chang

Inventions 2019, 4(4), 69; https://doi.org/10.3390/inventions4040069 - 28 Nov 2019

Cited by 21 | Viewed by 10050

Abstract

Geometric complexities and multi-physical phenomena add difficulties for predicting the thermal field and hence thermal management of an electric motor. A numerical design model that combined electromagnetic and thermal-fluid analysis was proposed for disclosing the detailed temperature distributions of each component in an [...] Read more.

Geometric complexities and multi-physical phenomena add difficulties for predicting the thermal field and hence thermal management of an electric motor. A numerical design model that combined electromagnetic and thermal-fluid analysis was proposed for disclosing the detailed temperature distributions of each component in an electric motor. The thermal fluid analysis implemented ANSYS-Fluent code to unravel the thermal field of the interior permanent magnet synchronous electric motor fitted with a smooth or novel spirally twisted channel in the cooling water jacket of a stator with and without shaft cooling. In accordance with the thermal powers converted from the various electromagnetic losses of the electric motor, the complex heat conduction model with realistic thermal boundary conditions was formulated. Initially, the turbulent flow structures and channel averaged Nusselt numbers of the spiral channels without and with the sectional twist were comparatively examined for acquiring the convective thermal boundary conditions in the water jacket. With the high thermal conductivity of the aluminum water jacket, the heat-transfer improvements from the smooth-spiral-channel conditions by using the twisted spiral channel were effective for reducing the average temperatures by about 10% but less effective for altering the characteristic thermal field in the water jacket. At 1290 < Dn < 6455 or 5000 < Re < 25,000 for the spiral channel flows, the channel average Nusselt numbers ratios between the smooth and twisted spiral channels were elevated to 1.18–1.09 but decreased with the increase of Dn or Re. A set of heat-transfer correlations for estimating the Nusselt numbers of Taylor flow in the rotor-to-stator air gap was newly devised from the data available in the literature. While the cooling effectiveness of the water jacket and shaft was boosted by the sectional twists along the spiral channel of the water jacket, the presence of Taylor flow in the annual air gap prohibited the effective rotor-to-stator heat transmission, leading to hot spots in the rotor. By way of airflow cooling through the rotating hollow shaft, the high temperatures in the rotor were considerably moderated. As the development of Taylor flow between the rotor and stator was inevitable, the development of active or passive rotor cooling schemes was necessary for extending the power density of an electric motor. Unlike the previous thermal circuit or lumped-parameter thermal model that predicted the overall temperatures of motor components, the present coupled electromagnetic and thermal-fluid model can reveal the detailed temperature distributions in an electric motor to probe the local hot spots of each component in order to avoid overheating at the early design stage. Full article

(This article belongs to the Special Issue Heat transfer and Thermal Managements of Innovative Systems)

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22 pages, 1246 KiB

Open AccessArticle

Prediction of Heat Transfer during Condensation in Non-Circular Channels

by Mirza M. Shah

Inventions 2019, 4(2), 31; https://doi.org/10.3390/inventions4020031 - 19 Jun 2019

Cited by 2 | Viewed by 5236

Abstract

It is desirable to know whether correlations for condensation in round tubes can be used for non-circular channels. To investigate this matter, a number of well-known correlations for mini and macro channels as well as some for flattened channels were compared to a [...] Read more.

It is desirable to know whether correlations for condensation in round tubes can be used for non-circular channels. To investigate this matter, a number of well-known correlations for mini and macro channels as well as some for flattened channels were compared to a database for condensation in non-circular channels. Data included square, rectangular, triangular, semi-circular, drum, N, and W shaped channels as well as flattened tubes. The data included 15 fluids, hydraulic diameter 0.067 to 1.46 mm, aspect ratio 0.14 to 7, reduced pressure 0.045 to 0.77, and mass flux from 48 to 1000 kgm⁻²s⁻¹. None of the correlations worked well for flattened tubes. Data for all other shapes were best predicted by the Shah correlation with mean absolute deviation of 20.1% with 1120 data points from 22 sources. None of the other correlations was found satisfactory over the entire range. Full article

(This article belongs to the Special Issue Heat transfer and Thermal Managements of Innovative Systems)

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Review

Jump to: Research

39 pages, 22724 KiB

Open AccessReview

A Review of Cooling Studies on Gas Turbine Rotor Blades with Rotation

by Shyy Woei Chang, Pey-Shey Wu, Ting-Yu Wan and Wei-Ling Cai

Inventions 2023, 8(1), 21; https://doi.org/10.3390/inventions8010021 - 12 Jan 2023

Cited by 3 | Viewed by 4040

Abstract

Increases in power density and thermal efficiency of a highly efficient gas turbine engine motivate an ever-mounting turbine entry temperature. The combined metallurgical and cooling advancements ensure the structural integrity of a gas turbine rotor blade that spins at high rotor speeds in [...] Read more.

Increases in power density and thermal efficiency of a highly efficient gas turbine engine motivate an ever-mounting turbine entry temperature. The combined metallurgical and cooling advancements ensure the structural integrity of a gas turbine rotor blade that spins at high rotor speeds in a gas stream with temperatures above the melting point of the blade material. The cooling performances promoted by a variety of heat transfer enhancement methods typical of the coolant channels of the leading edge, the mid-chord region, and the trailing edge of a gas turbine rotor blade are reviewed. The manifested rotational effects on the aerothermal performances of impinging jets and swirl chambers for leading-edge cooling, multi-pass ribbed, dimpled, and/or wavy channels over the mid-chord region, as well as pin fin and latticework narrow ducts in the trailing edge of a gas turbine rotor blade, are summarized and cross-examined. Research orientations for future cooling studies aimed at preventing the development of hot spots in a gas turbine rotor blade are recommended. Full article

(This article belongs to the Special Issue Heat transfer and Thermal Managements of Innovative Systems)

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