Energies

Research

Jump to: Review

27 pages, 5105 KB

Open AccessArticle

Performance of Double Pipe Heat Exchanger—Partially Occupied by Metal Foam—Is Better Enhanced Using Robust Adaptive Barrier Function-Based Sliding Mode Control

by Luma F. Ali, Shibly A. AL-Samarraie and Amjad J. Humaidi

Energies 2025, 18(17), 4671; https://doi.org/10.3390/en18174671 - 3 Sep 2025

Abstract

Numerous thermal practical applications utilize shell and tube heat exchanger appliances to transfer heat energy between hot and cold working fluids. Incorporating metal foam to the outer periphery of inner tube improves the heat transfer process from hot water in the tube side [...] Read more.

Numerous thermal practical applications utilize shell and tube heat exchanger appliances to transfer heat energy between hot and cold working fluids. Incorporating metal foam to the outer periphery of inner tube improves the heat transfer process from hot water in the tube side to cold water in the shell side and consequently improves heat exchanger performance. In this study, the integration of use of a porous material together with designing a robust adaptive controller could efficiently regulate the outlet cold water temperature to the desired value. This is achieved with respect to the time required for cold water to reach the desired temperature (settling time) and the amount of hot water volume flow during a certain time span. A barrier function-based adaptive sliding mode controller (BF-based adaptive SMC) is proposed, which requires only the information of temperature measurement of cold water. The stability of BF-based adaptive SMC is proved utilizing Lyapunov function analysis. The effectiveness of proposed controller is verified via numerical results, which showed that the proposed controller could achieve considerable accuracy of cold water temperature using suitable design parameters. In addition, the robustness of controller against variation in inlet temperature is also verified. Another improvement to performance of heat exchanger system is achieved by adding the metal foam of aluminum material on inner pipe perimeter with wide range of metal foam to outer inner pipe diameters ratio (

1 \leq s \leq 1.8

). The results showed that the settling time is significantly reduced which enables outlet cold water to reach the required temperature faster. With respect of the case of non-adding metal foam on inner pipe outer circumference, when

s = 1.2

, the settling time and hot water temperature are reduced by

1 / 2

and

17.3 %

, respectively, while for

s = 1.8

, they are decreased by

\leq 1 / 20

and

35.3 %

correspondingly. Accordingly, the required volume flow for hot water is reduced considerably. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

20 pages, 2809 KB

Open AccessArticle

In Situ Winter Performance and Annual Energy Assessment of an Ultra-Lightweight, Soil-Free Green Roof in Mediterranean Climate: Comparison with Traditional Roof Insulation

by Luca Evangelisti, Edoardo De Cristo and Roberto De Lieto Vollaro

Energies 2025, 18(17), 4581; https://doi.org/10.3390/en18174581 - 29 Aug 2025

Viewed by 175

Abstract

Green roofs are effective passive strategies for enhancing building energy efficiency and indoor thermal comfort, particularly in response to climate change. This study presents an experimental and numerical assessment of an ultra-lightweight, soil-free green roof system for Mediterranean climates. In situ thermal monitoring [...] Read more.

Green roofs are effective passive strategies for enhancing building energy efficiency and indoor thermal comfort, particularly in response to climate change. This study presents an experimental and numerical assessment of an ultra-lightweight, soil-free green roof system for Mediterranean climates. In situ thermal monitoring was carried out on two identical test rooms in Rome (Italy), comparing the green roof to a traditional tiled roof under winter conditions. Results revealed a 45% reduction in thermal transmittance. These data were used to calibrate a dynamic TRNSYS 18 model and then applied to annual simulations of energy demand and indoor comfort across different roof configurations, including expanded polystyrene-insulated reference roofs. The model was calibrated in accordance with ASHRAE Guideline 14, achieving an MBE within ±10% and a CV(RMSE) within ±30% for hourly data, ensuring the simulation’s reliability. The green roof reduced cooling energy demand by up to 58.5% and heating demand by 11.6% relative to the uninsulated reference case. Compared to insulated roofs, it maintained similar winter performance while achieving summer operative temperature reductions up to 0.99 °C and PPD decreases up to 2.94%. By combining field measurements with calibrated simulations, this work provides evidence of the green roof’s effectiveness as a passive retrofit solution for Mediterranean buildings. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

18 pages, 2263 KB

Open AccessArticle

Analysis of the Accuracy of the Inverse Marching Method Used to Determine Thermal Stresses in Cylindrical Pressure Components with Holes

by Magdalena Jaremkiewicz

Energies 2025, 18(17), 4546; https://doi.org/10.3390/en18174546 - 27 Aug 2025

Viewed by 230

Abstract

In the paper, the inverse solution of the heat conduction problem is analysed, which is applied to calculate transient thermal stresses on the internal surface of a thick-walled pipe weakened by a hole. The analysis considered a one-dimensional heat transfer problem when heat [...] Read more.

In the paper, the inverse solution of the heat conduction problem is analysed, which is applied to calculate transient thermal stresses on the internal surface of a thick-walled pipe weakened by a hole. The analysis considered a one-dimensional heat transfer problem when heat is transferred in a radial direction. In the inverse marching method, the measurement of the wall temperature at one point of a thermally insulated pipeline is used. The technique was verified regarding the distance between the point where the wall temperature is measured and the internal surface, the number of finite volumes in the inverse region, and the time step size are selected. The influence of these parameters on the accuracy of the calculated temperature, thermal stresses, heat transfer coefficient on the internal surface of the pipeline and thermal stresses at the hole edge was assessed. The reference values used to verify the technique were those calculated using the analytical method and the direct solution of the heat conduction problem, and the generated ‘measurement data’ were disturbed by random errors. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

18 pages, 13864 KB

Open AccessArticle

Thermomechanical Analysis of the GTM 400 MOD Turbojet Engine Nozzle During Kerosene and Hydrogen Co-Combustion

by Łukasz Brodzik, Bartosz Ciupek, Andrzej Frąckowiak and Dominik Schroeder

Energies 2025, 18(16), 4382; https://doi.org/10.3390/en18164382 - 17 Aug 2025

Viewed by 434

Abstract

This study investigated the thermomechanical behaviour of the nozzle of a GTM 400MOD miniature turbojet engine during combustion of aviation kerosene and co-combustion of kerosene with hydrogen. Numerical analysis was based on experiments conducted on a dedicated test rig at engine speeds ranging [...] Read more.

This study investigated the thermomechanical behaviour of the nozzle of a GTM 400MOD miniature turbojet engine during combustion of aviation kerosene and co-combustion of kerosene with hydrogen. Numerical analysis was based on experiments conducted on a dedicated test rig at engine speeds ranging from 31,630 rpm to 65,830 rpm, providing data on the temperature and dynamic pressure at the nozzle outlet. These data served as input to numerical analyses using the ANSYS Fluent, Steady-State Thermal, and Static Structural modules to evaluate exhaust gas flow, temperature distribution, and stress and strain states. The paper performed a basic analysis with additional simplifications, and an extended analysis that took into account, among other things, thermal radiation in the flow. The results of the basic analysis show that, at comparable thrust levels, co-firing and pure kerosene combustion yield similar nozzle temperature distributions, with maximum wall temperatures ranging from 978 K to 1090 K, which remain below the allowable limit of 1193 K (920 °C). Maximum stresses reached approximately 261 MPa, close to but not exceeding the yield strength of 316 stainless steel. Maximum nozzle deformation did not exceed 0.8 mm. Small dynamic pressure fluctuations were observed; For example, at 31,630 rpm, co-firing increased the maximum dynamic pressure from 1.56 × 104 Pa to 1.63 × 104 Pa, while at 47,110 rpm, it decreased from 4.05 × 104 Pa to 3.89 × 104 Pa. The extended analysis yielded similar values for the nozzle temperature and pressure distributions. Stress and strain increased by more than 76% and 78%, respectively, compared to the baseline analysis. The results confirm that hydrogen co-firing does not significantly alter the nozzle thermomechanical loads, suggesting that this emission-free fuel can be used without negatively impacting the nozzle’s structural integrity under the tested conditions. The methodology, combining targeted experimental measurements with coupled CFD and FEM simulations, provides a reliable framework for assessing material safety margins in alternative fuel applications in small turbojet engines. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

28 pages, 1918 KB

Open AccessArticle

Environmental and Economic Optimisation of Single-Family Buildings Thermomodernisation

by Anna Sowiżdżał, Michał Kaczmarczyk, Leszek Pająk, Barbara Tomaszewska, Wojciech Luboń and Grzegorz Pełka

Energies 2025, 18(16), 4372; https://doi.org/10.3390/en18164372 - 16 Aug 2025

Viewed by 562

Abstract

This study offers a detailed environmental, energy, and economic evaluation of thermal modernisation options for an existing single-family home in southern Poland. A total of 24 variants, combining different heat sources (solid fuel, biomass, natural gas, and heat pumps) with various levels of [...] Read more.

This study offers a detailed environmental, energy, and economic evaluation of thermal modernisation options for an existing single-family home in southern Poland. A total of 24 variants, combining different heat sources (solid fuel, biomass, natural gas, and heat pumps) with various levels of building insulation, were analysed using energy performance certification methods. Results show that, from an energy perspective, the most advantageous scenarios are those utilising brine-to-water or air-to-water heat pumps supported by photovoltaic systems, reaching final energy demands as low as 43.5 kWh/m²year and primary energy demands of 41.1 kWh/m²year. Biomass boilers coupled with solar collectors delivered the highest renewable energy share (up to 99.2%); however, they resulted in less notable reductions in primary energy. Environmentally, all heat pump options removed local particulate emissions, with CO₂ reductions of up to 87.5% compared to the baseline; biomass systems attained 100% CO₂ reduction owing to renewable fuels. Economically, biomass boilers had the lowest unit energy production costs, while PV-assisted heat pumps faced the highest overall costs despite their superior environmental benefits. The findings highlight the trade-offs between ecological advantages, energy efficiency, and investment costs, offering a decision-making framework for the modernisation of sustainable residential heating systems. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

20 pages, 4093 KB

Open AccessArticle

A Reduced Order Model of the Thermal Profile of the Rolls for the Real-Time Control System

by Dmytro Svyetlichnyy

Energies 2025, 18(15), 4005; https://doi.org/10.3390/en18154005 - 28 Jul 2025

Viewed by 362

Abstract

Effective real-time control systems require fast and accurate models. The thermal profile models of the rolls presented in this paper are proposed for a real-time control system for the design of the rolling schedule. The thermal profile of the roll defines the shape [...] Read more.

Effective real-time control systems require fast and accurate models. The thermal profile models of the rolls presented in this paper are proposed for a real-time control system for the design of the rolling schedule. The thermal profile of the roll defines the shape of the roll surface, its convexity, and, finally, the shape of the final product of the flat rolling, its convexity, and flatness. This paper presents accurate semi-analytical and finite element (FE) models, which serve to obtain an accurate solution of the joint thermal and mechanical problem, that is, heat transfer and thermal expansion. The results of the FE simulation are used for training the developed thermal model based on the neural network (NN) and for the creation of a dynamic reduced order model (ROM) of the roll surface profile. The pre-trained NN model gives accurate results and is faster than the FE model, but the model is not very useful for fast calculations in a real-time control system, mainly because the temperature distribution inside the rolls is not explicitly used in further calculations. In contrast, the ROM is fast and accurate and provides surface-shaped results that can be immediately used by other models of the real-time control system. The results of the simulation of the real process are also shown. Calculations of the roll campaign (more than 9 h) by the FEM model last several hours, while by the ROM less than 20 s. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

25 pages, 4424 KB

Open AccessArticle

Pool Boiling Heat Transfer of Ethanol on Surfaces with Minichannels

by Robert Pastuszko

Energies 2025, 18(15), 3938; https://doi.org/10.3390/en18153938 - 23 Jul 2025

Viewed by 365

Abstract

In this paper, the pool boiling of ethanol was analyzed. The experiments were carried out at atmospheric pressure. Heat transfer surfaces in the form of deep minichannels were made of copper. The channels with a depth of 0.2 to 0.5 mm were milled [...] Read more.

In this paper, the pool boiling of ethanol was analyzed. The experiments were carried out at atmospheric pressure. Heat transfer surfaces in the form of deep minichannels were made of copper. The channels with a depth of 0.2 to 0.5 mm were milled in parallel. The width of the minichannels was 0.6–1.2 mm, and the depth was 5.5, 6, and 10 mm. The highest heat transfer coefficient, 52 kW/m²K, was achieved for the minichannels with a depth of 6 mm and a width of 0.8 mm. The maximum heat flux of 953 kW/m² was produced using minichannels 5.5 mm deep and 0.5 mm wide. An over threefold increase in the heat transfer coefficient and over a twofold increase in the maximum heat flux in relation to the plain surface were obtained. In the heat flux range 21.2–1035 kW/m², the influence of channel width and depth on the heat exchange process was determined. The diameters of the detaching vapor bubbles were determined on the experimental setup using a high-speed camera. An analytical model was developed to determine the diameter of the departing bubble for the analyzed enhanced surfaces. The model correctly represented the changes in bubble diameter with increasing heat flux. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

16 pages, 6056 KB

Open AccessArticle

Heat Transfer Enhancement in Turbine Blade Internal Cooling Channels with Hybrid Pin-Fins and Micro V-Ribs Turbulators

by Longbing Hu, Qiuru Zuo and Yu Rao

Energies 2025, 18(13), 3296; https://doi.org/10.3390/en18133296 - 24 Jun 2025

Viewed by 748

Abstract

To improve the convective heat transfer in internal cooling channels of heavy-duty gas turbine blades, this study experimentally and numerically investigates the thermal performance of rectangular channels with hybrid pin-fins and micro V-ribs turbulators. The transient thermochromic liquid crystal (TLC) technique and ANSYS [...] Read more.

To improve the convective heat transfer in internal cooling channels of heavy-duty gas turbine blades, this study experimentally and numerically investigates the thermal performance of rectangular channels with hybrid pin-fins and micro V-ribs turbulators. The transient thermochromic liquid crystal (TLC) technique and ANSYS 2019 R3 (ICEM CFD 2019 R3, Fluent 2019 R3, CFD-Post 2019 R3) were employed under Reynolds numbers ranging from 10,000 to 50,000, with the numerical model rigorously validated against experimental data (the maximum RMSE is 2.5%). It is found that hybrid pin-fins and continuous V-ribs configuration exhibits the maximum heat transfer enhancement of 27.6%, with an average friction factor increase of 13.3% and 21.9% improvement in thermal performance factor (TPF) compared to the baseline pin-fin channel. In addition, compared to the baseline pin-fin channel, hybrid pin-fins and broken V-ribs configuration exhibits average heat transfer enhancement (Nu/Nu0) of 24.4%, an average friction factor increase of 7.2% and 22.5% improvement across the investigated Reynolds number range (10,000~50,000) based on computational results. The synergistic effects of hybrid pin-fin and micro V-rib structures demonstrate superior coolant flow control, offering a promising solution for next-generation turbine blade cooling designs. This work provides actionable insights for high-efficiency gas turbine thermal management. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

15 pages, 1297 KB

Open AccessFeature PaperArticle

Thermal and Emission Performance Evaluation of Hydrogen-Enriched Natural Gas-Fired Domestic Condensing Boilers

by Radosław Jankowski, Rafał Ślefarski, Ireneusz Bauma and Giennadii Varlamov

Energies 2025, 18(13), 3240; https://doi.org/10.3390/en18133240 - 20 Jun 2025

Viewed by 494

Abstract

The combustion of gaseous fuels in condensing boilers contributes to the greenhouse gas and toxic compound emissions in exhaust gases. Hydrogen, as a clean energy carrier, could play a key role in decarbonizing the residential heating sector. However, its significantly different combustion behavior [...] Read more.

The combustion of gaseous fuels in condensing boilers contributes to the greenhouse gas and toxic compound emissions in exhaust gases. Hydrogen, as a clean energy carrier, could play a key role in decarbonizing the residential heating sector. However, its significantly different combustion behavior compared to hydrocarbon fuels requires thorough investigation prior to implementation in heating systems. This study presents experimental and theoretical analyses of the co-combustion of natural gas with hydrogen in low-power-output condensing boilers (second and third generation), with hydrogen content of up to 50% by volume. The results show that mixtures of hydrogen and natural gas contribute to increasing heat transfer in boilers through convection and flue gas radiation. They also highlight the benefits of using the heat from the condensation of vapors in the flue gases. Other studies have observed an increase in efficiency of up to 1.6 percentage points compared to natural gas at 50% hydrogen content. Up to a 6% increase in the amount of energy recovered by water vapor condensation was also recorded, while exhaust gas losses did not change significantly. Notably, the addition of hydrogen resulted in a substantial decrease in the emission of nitrogen oxides (NOx) and carbon monoxide (CO). At 50% hydrogen content, NO_x emissions decreased several-fold to 2.7 mg/m³, while CO emissions were reduced by a factor of six, reaching 9.9 mg/m³. All measured NO_x values remained well below the current regulatory limit for condensing gas boilers, which is 33.5 mg/m³. These results highlight the potential of hydrogen blending as a transitional solution on the path toward cleaner residential heating systems. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

24 pages, 9236 KB

Open AccessArticle

Evaluating the Thermohydraulic Performance of Microchannel Gas Coolers: A Machine Learning Approach

by Shehryar Ishaque, Naveed Ullah, Sanghun Choi and Man-Hoe Kim

Energies 2025, 18(12), 3007; https://doi.org/10.3390/en18123007 - 6 Jun 2025

Viewed by 439

Abstract

In this study, a numerical model of a microchannel gas cooler was developed using a segment-by-segment approach for thermohydraulic performance evaluation. State-of-the-art heat transfer and pressure drop correlations were used to determine the air and refrigerant side heat transfer coefficients and friction factors. [...] Read more.

In this study, a numerical model of a microchannel gas cooler was developed using a segment-by-segment approach for thermohydraulic performance evaluation. State-of-the-art heat transfer and pressure drop correlations were used to determine the air and refrigerant side heat transfer coefficients and friction factors. The developed model was validated against a wide range of experimental data and was found to accurately predict the gas cooler capacity (Q) and pressure drop (ΔP) within an acceptable margin of error. Furthermore, advanced machine learning algorithms such as extreme gradient boosting (XGB), random forest (RF), support vector regression (SVR), k-nearest neighbors (KNNs), and artificial neural networks (ANNs) were employed to analyze their predictive capability. Over 11,000 data points from the numerical model were used, with 80% of the data for training and 20% for testing. The evaluation metrics, such as the coefficient of determination (R², 0.99841–0.99836) and mean squared error values (0.09918–0.10639), demonstrated high predictive efficacy and accuracy, with only slight variations among the models. All models accurately predict the Q, with the XGB and ANN models showing superior performance in ΔP prediction. Notably, the ANN model emerges as the most accurate method for refrigerant and air outlet temperatures predictions. These findings highlight the potential of machine learning as a robust tool for optimizing thermal system performance and guiding the design of energy-efficient heat exchange technologies. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

15 pages, 6330 KB

Open AccessArticle

Application of Neural Network Models for Analyzing the Impact of Flight Speed and Angle of Attack on Flow Parameter Non-Uniformity in a Turbofan Engine Inlet Duct

by Adam Kozakiewicz, Maciej Adamczyk and Rafał Kieszek

Energies 2025, 18(8), 2064; https://doi.org/10.3390/en18082064 - 17 Apr 2025

Viewed by 450

Abstract

This study investigates the aerodynamic performance of a fourth-generation normal shockwave inlet system, with a primary focus on minimizing pressure losses and ensuring uniform airflow distribution. A computational model was developed, incorporating a section of the fuselage along with the complete inlet duct. [...] Read more.

This study investigates the aerodynamic performance of a fourth-generation normal shockwave inlet system, with a primary focus on minimizing pressure losses and ensuring uniform airflow distribution. A computational model was developed, incorporating a section of the fuselage along with the complete inlet duct. The model was discretized using a hybrid mesh approach to enhance numerical accuracy. The analysis was conducted at a flight altitude of 8000 m, encompassing 370 distinct cases defined by varying angles of attack and Mach numbers. This comprehensive parametric study yielded a dataset of 10,800 total pressure measurements across predefined sampling locations. Based on the obtained results, flow distortion coefficients in both circumferential (CDI) and radial directions (RDI) were systematically determined for each test case. The interdependencies between CDI, RDI, Mach number, and angle of attack (α) were analyzed and presented in a consolidated manner. In the second phase of the study, an artificial neural network (ANN) utilizing a Feed-Forward architecture was implemented to predict pressure distributions for intermediate flight conditions. The ANN was trained using the CFG algorithm, and the predictive accuracy was assessed through the determination coefficients computed by comparing ANN-based estimates with numerical simulation results. The findings demonstrate the efficacy of ANN-based modeling in enhancing the predictive capabilities of inlet flow dynamics, offering valuable insights for optimizing next-generation supersonic air intake systems. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

15 pages, 3033 KB

Open AccessArticle

Particle Image Velocimetry Flow Characterisation of High-Convection Slot Nozzle Systems for Impingement Heat Transfer

by Eileen Trampe, Ida Daube, Dominik Büschgens, Herbert Pfeifer and Christian Wuppermann

Energies 2025, 18(6), 1363; https://doi.org/10.3390/en18061363 - 10 Mar 2025

Viewed by 803

Abstract

Impingement jets are used in many applications for high convective heat transfer. In order to optimise specialised nozzle systems, a comprehensive understanding of the gas flow is essential. The aim of this work is to investigate high-convective flows at Re = 10,000 to [...] Read more.

Impingement jets are used in many applications for high convective heat transfer. In order to optimise specialised nozzle systems, a comprehensive understanding of the gas flow is essential. The aim of this work is to investigate high-convective flows at Re = 10,000 to Re = 50,000 for a single slot nozzle (slot width W = 5 mm) and a slot nozzle array (distance between nozzle slots s = 70 mm) consisting of five nozzles. Particle image velocimetry measurements are taken for a distance between strip and nozzle exit of H = 50 mm and are compared to verify if the results from a single slot nozzle are transferable to a nozzle array. The presence of an array of nozzles not only creates a distinct zone where the individual jets interact but also changes the flow characteristics of the respective free jets. The potential core length in the nozzle field is significantly reduced compared to the single nozzle. It is therefore not possible to make a direct transfer of the results. Direct transferability of the results is therefore not possible. This means that further studies on whole arrays are needed to optimise nozzle arrays. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

Review

Jump to: Research

13 pages, 3081 KB

Open AccessReview

Surface Air-Cooled Oil Coolers (SACOCs) in Turbofan Engines: A Comprehensive Review of Design, Performance, and Optimization

by Wiktor Hoffmann and Magda Joachimiak

Energies 2025, 18(15), 4052; https://doi.org/10.3390/en18154052 - 30 Jul 2025

Viewed by 414

Abstract

Surface Air-Cooled Oil Coolers (SACOCs) can become a critical component in managing the increasing thermal loads of modern turbofan engines. Installed within the bypass duct, SACOCs utilize high-mass flow bypass air for convective heat rejection, reducing reliance on traditional Fuel-Oil Heat Exchangers. This [...] Read more.

Surface Air-Cooled Oil Coolers (SACOCs) can become a critical component in managing the increasing thermal loads of modern turbofan engines. Installed within the bypass duct, SACOCs utilize high-mass flow bypass air for convective heat rejection, reducing reliance on traditional Fuel-Oil Heat Exchangers. This review explores SACOC design principles, integration challenges, aerodynamic impacts, and performance trade-offs. Emphasis is placed on the balance between thermal efficiency and aerodynamic penalties such as pressure drop and flow distortion. Experimental techniques, including wind tunnel testing, are discussed alongside numerical methods, and Conjugate Heat Transfer modeling. Presented studies mostly demonstrate the impact of fin geometry and placement on both heat transfer and drag. Optimization strategies and Additive Manufacturing techniques are also covered. SACOCs are positioned to play a central role in future propulsion systems, especially in ultra-high bypass ratio and hybrid-electric architectures, where traditional cooling strategies are insufficient. This review highlights current advancements, identifies limitations, and outlines research directions to enhance SACOC efficiency in aerospace applications. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

42 pages, 23380 KB

Open AccessReview

A Review of Recent Research on Flow and Heat Transfer Analysis in Additively Manufactured Transpiration Cooling for Gas Turbines

by Kirttayoth Yeranee and Yu Rao

Energies 2025, 18(13), 3282; https://doi.org/10.3390/en18133282 - 23 Jun 2025

Viewed by 1603

Abstract

Advanced gas turbine cooling technologies are required to bridge the gap between turbine inlet temperatures and component thermal limits. Transpiration cooling has emerged as a promising method, leveraging porous structures to enhance cooling effectiveness. Recent advancements in additive manufacturing (AM) enable precise fabrication [...] Read more.

Advanced gas turbine cooling technologies are required to bridge the gap between turbine inlet temperatures and component thermal limits. Transpiration cooling has emerged as a promising method, leveraging porous structures to enhance cooling effectiveness. Recent advancements in additive manufacturing (AM) enable precise fabrication of complex transpiration cooling architectures, such as triply periodic minimal surface (TPMS) and biomimetic designs. This review analyzes AM-enabled transpiration cooling for gas turbines, elucidating key parameters, heat transfer mechanisms, and flow characteristics of AM-fabricated designs through experimental and numerical studies. Previous research has concluded that well-designed transpiration cooling achieves cooling effectiveness up to five times higher than the traditional film cooling methods, minimizes jet lift-off, improves temperature uniformity, and reduces coolant requirements. Optimized coolant controls, graded porosity designs, complex topologies, and hybrid cooling architectures further enhance the flow uniformity and cooling effectiveness in AM transpiration cooling. However, challenges remain, including 4–77% porosity shrinkage in perforated transpiration cooling for 0.5–0.06 mm holes, 15% permeability loss from defects, and 10% strength reduction in AM models. Emerging solutions include experimental validations using advanced diagnostics, high-fidelity multiphysics simulations, AI-driven and topology optimizations, and novel AM techniques, which aim at revolutionizing transpiration cooling for next-generation gas turbines operating under extreme conditions. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

► Show Figures

Figure 1

15 pages, 304 KB

Open AccessFeature PaperReview

Review of Thermal Calculation Methods for Boilers—Perspectives on Thermal Optimization for Improving Ecological Parameters

by Bartosz Ciupek and Andrzej Frąckowiak

Energies 2024, 17(24), 6380; https://doi.org/10.3390/en17246380 - 18 Dec 2024

Cited by 1 | Viewed by 1439

Abstract

This article presents an overview of thermal calculation methods used in boilers powered by fossil fuels (solid, liquid or gas). The analysis was carried out mainly in terms of combustion chamber calculation methods. Changing standards and legal regulations regarding the use of fossil [...] Read more.

This article presents an overview of thermal calculation methods used in boilers powered by fossil fuels (solid, liquid or gas). The analysis was carried out mainly in terms of combustion chamber calculation methods. Changing standards and legal regulations regarding the use of fossil fuels in Europe and the world make it necessary to adapt calculation methods and boiler design to current requirements, and many of them are related to outdated boiler models or for fuels that are no longer so heavily used in industrial solutions. Current research and development trends implemented in the EU and in the world related to the issues of the European Green Deal, the Fit for 55 directive and other ecological trends in the energy sector make it necessary to verify and remodel the calculation methods used so far in terms of the thermal efficiency of the device, fuel consumption or the use of fuels not previously used in their wide range in a wider application. Hence, the knowledge and updating of the state of knowledge in the field of the thermal calculation of boilers in terms of their environmental performance is necessary and strongly sought after by researchers. It is undoubted that in the next few years, boilers will continue to be the main source of thermal energy, especially in the power industry or industry. A reasonable energy transition should be based on the direction of the thermal optimization of already functioning structures and adaptation of their operating parameters to the planned new ecological fuels in the sense of the intensification of energy converted from primary form to thermal energy, and in the last step, it should reorganize the energy and industrial sectors, leaving only these groups of devices treated as a stable and necessary source of energy. Therefore, it should be recognized that activities aimed at improving the thermal parameters of boilers should directly improve the thermal efficiency of the device, and this will translate into fuel savings and reduce their negative impact on the environment. Full article

(This article belongs to the Special Issue Heat Transfer Analysis: Recent Challenges and Applications)

Journal Menu

Journal Browser

Heat Transfer Analysis: Recent Challenges and Applications

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (15 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI