Three-dimensional Heat Transfer Research Articles

Modelling of cracking during beam oscillation laser welding of a creep-resistant nickel alloy

During high power laser welding of Inconel 740H, horizontal solidification cracks form at locations between approximately 70–80% of the weld depth. With the integration of circular beam oscillation, the laser energy density distribution and underlying thermo-mechanical conditions were altered. By coupling three-dimensional heat transfer, fluid flow, and stress modelling tools, the role that circular beam oscillation plays in the formation of the strain rates and stresses driving this cracking phenomenon was identified. While the addition of a circular oscillation pattern appeared to lower the stress levels along the solidification front, it did not eliminate the appearance of horizontal cracking. Only when the beam amplitudes reached 1.6 mm did solidification cracking disappear, but the weld depths were also significantly reduced.

The effect of non-uniform skelp temperature on X70 steel coil cooling

This study explored the effect of varying steel skelp temperature (500 °C–600 °C) on the subsequent temperature-time ( T- t) profile during and after coiling of low C (0.05 wt. %) X70 microalloyed steels. Three industrially produced steel coils with similar rough rolling temperatures (∼1050 °C) and finish rolling temperatures (∼850 °C) but different coiling temperatures (500 °C–600 °C) and different skelp thicknesses (19 mm and 25 mm) were studied. The surface temperature of each coil was measured using an infrared video camera. A three-dimensional heat transfer model was developed to predict the T- t profiles. A lower (∼60 °C) initial skelp temperature near the head and tail of the skelp led to a reduced coil temperature. A higher (∼50 °C) temperature near the head and tail region of the skelp resulted in a more uniform coil temperature (a difference of ∼10 °C instead of ∼50 °C).

Open-loop temperature rise history control method with scanning electron beam as a programmable heat source

Temperature-rise history control technology is widely applied in rapid thermal process and material thermal assessment. We present an open-loop temperature rise history control method. The fundamental concept involves loading a heat flux history onto the sample’s surface, inversed from the target temperature rise history, to regulate the sample’s temperature through programming the energy flux history of the scanning electron beam. We reconstructed the temperature-rise history of the leading edge of an aircraft during the HIFIRE-5b flight test with a relative deviation of 1%. Additionally, we reconstructed a typical temperature rise curve of a silicon wafer during rapid thermal processing with a relative deviation of 1%. In theory, this temperature control method can be extended to two-dimensional and three-dimensional heat transfer processes to achieve transient control of sample surface/cross-section temperature field with one- or two-dimensional distribution characteristics. This research can provide a high-performance temperature control technology for a wide range of industrial fields, and lay a theoretical foundation for the development of related technologies based on temperature history analysis.

THE IMPACT OF SOLAR RADIATION ON THE TEMPERATURE REGIME OF A ROOM IN WINTER

The article is devoted to the computational studies of the air-thermal state of office premises taking into account the effect of solar radiation coming through window openings. The study was conducted for a room with two windows using two heating devices installed under them. The air-temperature regime of premises in winter, characterized by the highest thermal energy consumption for heat supply, is considered. The study is based on the solution of a three-dimensional nonlinear heat transfer problem described by a system of equations of turbulent momentum and energy transfer. The k-e turbulence model is used to close this system. The results of numarical modeling of the physical situation under study are presented. The research data on the features of the air-thermal state of the premises under solar radiation conditions are given. The results of a comparative analysis of the air-temperature conditions of office premises corresponding to the solution of the specified heat exchange problems in the presence and absence of solar radiation are presented and the effects of solar radiation on the structure of the air flow and the thermal state of the premises are established. It is shown that in the presence of solar radiation, the air flow picture and the character of the temperature fields in the premises change significantly. In particular, in these conditions, the increase in the average temperature of the premises for the studied period is 2.5 °С. The possibility of a certain reduction of the load on the heating system in the presence of solar radiation is noted. Bibl. 17, Fig. 5.

Numerical Approach of the First Instability Appearance in Inclined Taylor–Couette System

The present study numerically investigates the three-dimensional forced and mixed convection heat transfer in an inclined Taylor–Couette system (η=0.5 and Γ=20) submitted to a radial temperature gradient. The main objective of this study is to determine the effect of the angle inclination duct on the thermal and dynamic fields. Several cases have been dealt with depending on the inclination angle to detect the critical Reynolds number in each case. The model of the conservation equations with their boundary conditions is numerically solved by the finite volume method with a second-order spatiotemporal discretization. The results show that, in forced convection, the effect of the inclination angle is inexistent on the velocity field. However, with the presence of buoyancy effects, which impact flow stability and the transition to turbulence, the inclination influences both velocity and temperature fields. It also shows that selecting the vertical position of the annulus is preferable to obtain hydrodynamic stability in mixed convection. At the same time, from the thermal point of view, it is preferable to select the horizontal position to get dynamic and thermal stability.

An analytical heat transfer model for transient Raman thermometry analysis.

Transient Raman thermometry improves on its steady-state counterpart by eliminating the error-prone steps of temperature calibration and laser absorption measurement. However, the accompanying complex heat transfer process often requires numerical analysis, such as the finite element method, to decipher the measured data. This step can be time-consuming, inconvenient, and difficult to derive a physical understanding of the heat transfer process involved. In this work, the finite element method is replaced by fitting the measured data to an analytical three-dimensional heat transfer model. This process can be completed in a few seconds. Using this approach, the in-plane thermal conductivity of two bulk layered materials and the interfacial thermal conductance between two-dimensional materials and quartz have been successfully measured. Based on our model, we performed an analytical quantitative sensitivity analysis for transient Raman thermometry to discover new physical insights. The sensitivity of the in-plane thermal conductivity of bulk layered materials is dictated by the ratio between the spot radius and heat spreading distance. The sensitivity of the interfacial thermal conductance between two-dimensional materials and quartz is determined by its conductance value. In addition, the uncertainty of the measured value contributed by the uncertainty of the input parameters can be efficiently estimated using our model. Our model provides an efficient data and sensitivity analysis method for the transient Raman thermometry technique to enable high throughput measurements, facilitate designing experiments, and derive physical interpretations of the heat transfer process.

Three-dimensional numerical investigation on flow and heat transfer characteristics and multi-objective optimization of interconnected microchannels

The interconnected microchannel demonstrates excellent performance in enhancing flow heat transfer. However, the optimal width of the interconnecting slot has not been thoroughly investigated. To address this gap, this paper numerically simulates the three-dimensional flow and heat transfer of interconnected microchannels featuring varied slot widths and channel depths. The investigated slot widths range from 50 to 1000 μm and depths of 100, 200, and 300 μm. Evaluation of overall performance encompasses heat transfer and flow characteristics such as average wall temperature, heat transfer coefficient, thermal resistance as well as pressure drop. It is the interconnected slots that interrupt the velocity and thermal boundary layers, contributing to enhanced heat transfer. Furthermore, the back propagation neural network and non-dominated sorting genetic algorithm-II are utilized for multi-objective optimization of thermal resistance and pressure drop. The technique for order preference by similarity to an ideal solution (TOPSIS) method combined with the entropy weight method is employed to select the compromise optimal solution from the Pareto optimal solutions. The optimized slot widths are 369, 424, and 167 μm for channel depths of 100, 200, and 300 μm, respectively. This research provides data support for the optimization design and engineering manufacturing of interconnected microchannels.

Study on three-dimensional natural convection heat transfer in a house with two heating surfaces

Study on three-dimensional natural convection heat transfer in a house with two heating surfaces

Heat transfer performance of energy pile and borehole heat exchanger: A comparative study

Geothermal structures are widely utilized to satisfy the heating and cooling demands of buildings, providing a promising alternative to the escalating scarcity of energy. As two types of geothermal heat exchangers, energy piles and borehole heat exchangers exhibit different efficiencies in extracting geothermal energy. This paper examines the thermal performance of an energy pile and a borehole heat exchanger under heating and cooling conditions through field tests, introducing the heat exchange rate per unit pipe length (q0) as a metric. Furthermore, a three-dimensional heat transfer numerical model was developed and validated. The parametric analysis was subsequently conducted to investigate the sensitivity of heat exchange efficiency to five parameters, including flow rate, inlet temperature, pipe diameter, soil thermal conductivity, and soil temperature. The results showed that the heat transfer efficiency of the borehole heat exchanger was 42.2 % and 48.7 % lower than that of the energy pile under the heating and cooling conditions, respectively. Moreover, the heat transfer efficiency of the energy pile and borehole heat exchanger is most sensitive to inlet temperature, with the latter showing greater sensitivity to pipe diameter. This study provides valuable insights into optimizing the design and operation of energy piles and borehole heat exchangers to meet the growing energy demands of buildings.

Thermal behavior of coated powder during directed energy deposition (DED)

In powder-based additive manufacturing (AM), the quality of the feedstock material is critical for obtaining enhanced mechanical properties. Recently, the application of coated powders during directed energy deposition (DED) has been prompted by the goal of fabricating composite and functional materials in-situ. The complex temperature and momentum fields established during DED render direct experimental characterization of coated powder behavior challenging. To address this challenge, this study reports on the thermal behavior of coated powders during interactions with the molten pool by constructing three-dimensional heat transfer and phase distribution models using the finite elements method (FEM). Transient temperature and phase distributions were calculated for coated and uncoated stainless steel 316L and ZnAl powders under various particle size, coating thickness, molten pool temperature, and coating material conditions. Particle residence time values were extracted from the calculations, defined as time spent by the particle before a phase change. The results show large variations in particle residence time (85 μs to 2670 μs for stainless steel 316L particles, and 48 μs to infinity for ZnAl particles) as a function of the variables considered, especially the thermal diffusivity of the coating materials, thereby highlighting the potential value of coatings as an additional design parameter in DED. Significant increases in particle residence time for both stainless steel 316L and ZnAl particles were found when contact angle increases from 0° (submergence regime) to 180° (floating regime).

Steady Heat Transfer Analysis of the Refrigerator Seal Considering Rigid and Flexible Contact

The rigid and flexible contact of the refrigerator seal has a significant impact on its heat transfer characteristics, but existing research has ignored this important factor. In this paper, the assembly physical model at the seal region is established by static structural analysis. Then a three-dimensional heat transfer numerical simulation is carried out. The assembly distance affects the contact state of the seal by changing the contact position between the seal and the door or the cabinet. The calculation results show that the calculated temperature at the seal region considering the actual assembly deformation is closer to the measured temperatures. In the case study, the heat leakage load decreases by 18.57% and 19.99% at the compressed state, while it increases by 4.45% under the stretching state. The proportion of heat transfer load in the path of rubber strip-cold air and rubber strip-outer shell of the cabinet is the largest, reaching over 30.0%. The heat transfer load of the cold bridge also accounts for over 20.0%. When optimizing the seal structure, reducing the contact interface length of rubber strip-cold air, reducing thermal conductivity, and increasing the contact thermal resistance of cold bridge should be focused on.

Effect of oscillation parameters on weld surface morphology during laser beam oscillation welding of stainless steel

During laser beam oscillation welding (LBOW), the weld surface morphology is important because it influences the appearance of the workpiece and reflects the welding quality, and the oscillation parameters have an important effect on the weld surface morphology. Therefore, a combination of experimental research and numerical simulation is conducted to investigate the influence of oscillation parameters, including oscillation mode, oscillation frequency, and oscillation amplitude, on the weld surface morphology during LBOW. The calculation encompasses the oscillation trajectory, combined velocity, and energy distribution on the weld surface, varying with different oscillation parameters. A three-dimensional heat transfer and fluid flow model with the oscillation heat source is established to simulate the temperature and fluid flow behavior inside the weld pool. When the heat input is constant, an increase in oscillation frequency results in a decrease in weld width and a smoother surface. As the oscillation frequency increases, the weld width decreases, the surface becomes smooth, and the energy distribution on the weld surface becomes more uniform. The fact that the period of the surface pattern is almost equal to the oscillation period indicates a direct correlation between the formation of weld surface pattern and the oscillation trajectory in LBOW. Among all the oscillation modes, the minimum combined velocity which is equal to the welding velocity occurs at the inflection point in the linear oscillation mode, and the variation in combined velocity of the laser beam is the smallest for circular oscillation mode. The surface pattern is primarily influenced by the oscillation trajectory and fluid flow within the weld pool. Under conditions of lower oscillation frequencies or larger oscillation amplitudes, the fluid flow is weaker, and the surface pattern is primarily influenced by the oscillation trajectory. Conversely, when the fluid flow is stronger, the surface pattern is mainly determined by the fluid flow within the weld pool under conditions of higher oscillation frequencies or smaller oscillation amplitudes. This study explains the formation mechanisms of weld surface patterns and provides insights and guidance for selecting optimal oscillation parameters in LBOW.

A Multivariable Numerical Investigation of Wavy-Based Microchannel Heat Sink Geometry Towards Optimal Thermal Performance

Abstract This research provides a comprehensive multivariable comparative investigation of the effect of various microchannel configurations on their thermal performance. Three-dimensional fluid flow and heat transfer simulations are performed with different arrangements of the channel's width tapering and cross-sectional aspect ratio with an emphasis on the synergistic proven effects of geometrical parameters in innovatory combinations. Results confirm that wavy channels are significantly superior to straight channels in terms of thermal performance due to the creation of secondary flow (Dean Vortices), which improves the processes of advective mixing and, therefore, overall heat transfer characteristics with minimal pumping power penalty. Width-tapering of wavy channels also shows better thermal resistance than untapered wavy channels producing almost 10 percent thermal resistance improvement. The study indicates a significant dependency of thermal performance on the cross-sectional aspect ratio of the channel which suggests that there are ideal tapering and aspect ratio conditions. An innovative wavy-tapered microchannel heat sink has been introduced, featuring an optimal parametric configuration and directionally alternating coolant flow. This design results in additional thermal resistance improvement by 15% and significantly improves substrate temperature distribution uniformity. Overall, the results demonstrate the superior potential of the configuration for high-end electronics cooling tasks. These results provide interpretive insight into microchannel heat sink design and optimization.

Analysis of Longitudinal Cracking and Mold Flux Optimization in High-Speed Continuous Casting of Hyper-Peritectic Steel Thin Slabs

Longitudinal crack defects are a frequent occurrence on the surface of thin slabs during the high-speed continuous casting process. Therefore, this study undertakes a detailed analysis of the solidification characteristics of hyper-peritectic steel thin slabs. By establishing a three-dimensional heat transfer numerical model of the thin slab, the formation mechanism of longitudinal cracks caused by uneven growth of the initial shell is determined. Based on the mechanism of longitudinal crack formation, by adjusting the performance parameters of the mold flux, the contradiction between the heat transfer control and lubrication improvement of the mold flux is fully coordinated, further reducing the incidence of longitudinal cracks on the surface of the casting thin slab. The results show that, using the optimized mold flux, the basicity increases from 1.60 to 1.68, the F- mass fraction increases from 10.67% to 11.22%, the Na2O mass fraction increases from 4.35% to 5.28%, the Li2O mass fraction increases from 0.68% to 0.75%, and the carbon mass fraction reduces from 10.86% to 10.47%. The crystallization performance and rheological properties of the mold flux significantly improve, reducing the heat transfer performance while ensuring the lubrication ability of the molten slag. After optimizing the mold flux, a surface detection system was used to statistically analyze the longitudinal cracks on the surface of the casting thin slab. The proportion of longitudinal cracks (crack length/steel coil length, where each coil produced is about 32 m long) on the surface of the thin slab decreases from 0.056% to 0.031%, and the surface quality of the thin slab significantly improves.

Investigation of thermal performance at forced convection in plate-fin heat sink

Interest in studies on more effective and faster heat dissipation in microelectronic equipment has increased in recent years due to the cooling area and equipment size limitations. This study attempts to focus on the effect of different fin geometry parameters on pure forced convection heat transfer. Total surface areas of plate-fin heat sinks were kept constant and were carried out for ten different heat sinks in these analyses. The Ansys-Fluent 2023 R1 commercial package program was used to perform the thermal and hydrodynamic performance analyses. Three-dimensional turbulent forced convection heat transfer analyses at heat sinks were subjected to fluid flow (500≤Re≤3000). The effects of gap between fins, fin thickness, fin height, fin number, and air velocity on the heat transfer and the friction factor were obtained and discussed for heat sinks. It was observed that there was a maximum difference of 0.27 % between the maximum temperatures obtained as a result of this analysis and the experimental study results in the literature. Among the ten cases examined (from Case 1 to Case 10), the highest heat transfer coefficient was obtained in Case 2 (number of fins 6, gap between fins 4 mm, fin height 17 mm and fin thickness 2 mm) at Re = 3000. The heat transfer coefficient of Case 2 was 41.29 % higher than the heat transfer coefficient of Case 4 at Re = 3000; though, the friction factor of Case 2 is 55.93 % higher than Case 4. Also, a useful correlation for the heat transfer coefficient was generated for the fin geometric parameters and Reynolds number.

Numerical assessment of hydrothermal and entropy generation characteristics of graphene quantum dots nanofluid in a microchannel heat sink incorporating secondary channels and ribs

Efficient heat dissipation from electronic chips is essential for enhancing their performance and longevity. Significant progress has been achieved through the introduction of nanofluids and microchannel heat sinks. However, there is still a need for nanofluids that demonstrate exceptional thermal properties and stability. Graphene quantum dots nanofluid, an innovative carbon-based coolant with zero-dimensional nanostructures, presents promising features such as excellent chemical stability, surfactant-free preparation, superior thermal properties, and minimal impact on rheological characteristics. This study explores, for the first time, the hydrothermal behavior and entropy generation of graphene quantum dots nanofluid in a microchannel heat sink comprising secondary flow channels and ribs. To this end, a three-dimensional conjugate heat transfer model is built using ANSYS Fluent software, and the governing equations are solved using the finite volume method. The simulations are carried out considering temperature-dependent thermophysical properties under different concentrations ranging from 0 to 0.5 % and Reynolds numbers ranging from 100 to 500. The results reveal that the maximum bottom wall surface temperature decreases by 5.88 K, while the heat transfer coefficient improves by 24.9 % compared to the base fluid. Moreover, the total entropy generation reduces by 14.7 %. On the other hand, the pressure drop increases by 43 %. Overall, the highest increment in Performance Evaluation Criteria is 10.8 % at a Reynolds number of 100 and a concentration of 0.5 %, making this particular condition suitable for practical applications.

Enhancing PEMEC Efficiency: A synergistic approach using CFD analysis and Machine learning for performance optimization

The proton exchange membrane electrolytic cell (PEMEC) is a clean, pollution-free, and promising device for producing hydrogen from water electrolysis. This paper enhances the electrochemical performance of the PEMEC by developing a comprehensive three-dimensional two-phase non-isothermal heat and mass transfer cell model. An analysis was conducted to study the influence of various operating parameters on the temperature safety and efficiency of the cell. The performance of the latter was optimized by adopting the machine learning technology, which aimed at identifying optimal conditions for improved performance. The obtained results showed that, when the inlet water flow rate and membrane thickness were increased, the average temperature of the anode catalyst layer (A-CL) was decreased by 1.4 K and 2.31 K, respectively. This allowed to improve the safety of the electrolytic cell. However, it would reduce the hydrogen and oxygen mole fraction in the electrolyzer. On the contrary, enhancing the porosity or thickness of the anode gas diffusion layer can increase the average A-CL temperature and decrease the oxygen and hydrogen mole fraction. Therefore, the backpropagation neural network and non-dominated sorting genetic algorithm were used to predict and optimize the performance of the electrolyzer, in order to maximize its temperature safety, electrochemical reaction rate, and hydrogen evolution efficiency as much as possible. The results of this study provide a theoretical foundation for the selection of suitable cell models according to different conditions in engineering applications. It also has an application value in energy saving and sustainable development.

Experimental and Numerical Study of Newly Assembled Lightweight Radiant Floor Heating System

In this study, the heating capacity of a new prefabricated assembled hot water radiant modular heating system made from a recycled waste building masonry structure is investigated through experimental and numerical simulation methods. The heating capacity of the system in different working conditions (a water supply temperature of 48 °C, 51 °C, 56 °C, and 61 °C; a flow rate of 0.49 m3/h, 0.35 m3/h, and 0.21 m3/h) is analyzed and verified. A three-dimensional steady-state heat transfer numerical model of the floor heat transfer of the module is established, and the accuracy of the model is verified through the measured results to investigate the heating capacity of this system under different water supply temperatures, flow rates and coil spacings. The results show that the new prefabricated hot water radiant module heating system has a 0.9 °C higher air temperature and 2.1 °C higher average floor surface temperature than the traditional wet floor radiant heating system under the same experimental conditions, and the response time is 44% shorter. The water supply temperature can significantly change the heating capacity of the system, while the water supply flow rate has little effect on the system. The established three-dimensional steady-state numerical model can be in good agreement with the measured results. This study can provide an experimental and theoretical basis for the design and application of such systems.

Solid Oxide Cell Reactor Model for Transient and Stationary Electrochemical H2O and CO2 Conversion Process Studies

The ability of high-temperature solid oxide cell (SOC) electrochemical reactors to efficiently convert atmospheric carbon to high value chemicals for industrial and energy storage applications via CO2 and co-electrolysis makes them a key technology for active carbon utilisation. However, due to additional operational risks from thermochemical reactions on thermal management, limited experimental capacity, and relative novelty, CO2 and co-electrolysis lag behind steam electrolysis in large-scale adoption. Here, a 1D+1D SOC model based on fundamental first principles considering three-dimensional heat transfer was improved via a unique method for representing co-electrolysis electrochemistry, solving with low computational effort. Validation against experimental data for two compositions and pressures, showed high levels of accuracy with respect to characteristic cell voltages, temperatures, and outlet compositions. The model also showed CO2 reduction during co-electrolysis mainly occurred via reverse water gas shift, while CO2 electrolysis still accounted for up to 35% of the total share. Pressurised co-electrolysis operation promotes exothermic methanation, causing pronounced heating of the reactor, consequently reducing the isothermal current density. Therefore, low to moderate pressurisation is likely most suited for coupling with downstream synthesis processes to avoid the installation of unnecessarily large systems and associated high costs.

Fire resistance analysis and protection measures for cable components of suspension bridges

The growing number of vehicle fire incidents on suspension bridges poses a significant threat to the safety of the cable body components of these structures. This study focuses on the Longtan Bridge and employs a coupled Computational Fluid Dynamics-Finite Element Method (CFD-FEM) approach to recreate the environment of a tanker truck fire. A three-dimensional heat transfer model of the cable components and a structural fire resistance analysis model of the entire bridge are established. The study reveals the heat transfer patterns of cable components under a tanker truck fire and the evolution of the bridge structure's performance. Additionally, fire protection measures for cable components are proposed. The results indicate that during a tanker truck fire, the bridge deck exhibits a spatial transient temperature field, with temperatures around the cable components reaching 1170 °C, causing the highest temperature experienced by the steel wires on the cable surface to reach 736 °C. Under fire conditions, there is a redistribution of internal forces between the cables, with the fire-affected cable experiencing a decrease in internal forces and significant increases in adjacent cables' internal forces. The fire leads to plastic deformation in the fire-affected cable, resulting in permanent damage to the cables. When the number of cables broken due to fire at the midspan of the Longtan Bridge reaches six, the stress in the adjacent cables reaches 1861 MPa, exceeding the cables' ultimate tensile strength, leading to a progressive collapse of the entire bridge structure. The proposed heat-expansion fireproof coating and combination fire protection measures meet the regulatory requirements for fire resistance. It is recommended to apply a 3.5 mm thick heat-expansion fireproof coating on the main cable and cable components of the Longtan Bridge for fire protection. The research findings can serve as a reliable basis for establishing a fire protection system for the cable components of the Longtan Bridge.