Thermal Design Research Articles

Thermal design, analysis and test: Framework for CubeSat in low Earth orbit

Thermal design, analysis and test: Framework for CubeSat in low Earth orbit

Optimization of building thermal environment in industrial heritage landscape regeneration design simulation based on image visual visualization

With the increasing attention paid to the regeneration design of industrial heritage landscape, how to effectively improve the thermal energy environment in these areas has become a research hotspot. The thermal efficiency of buildings not only affects the energy consumption, but also relates to the comfort of users and the sustainable development of the region. This study aims to explore the optimization method of building thermal energy environment based on image visual visualization, so as to achieve efficient regeneration of industrial heritage landscape, and improve the thermal energy performance and environmental adaptability of buildings through scientific design and simulation means. Through the use of computer aided design (CAD) and building information modeling (BIM) techniques, combined with heat flow simulation and visual image analysis, a detailed thermal environment assessment is carried out for selected industrial heritage buildings. Through data collection and analysis, we take into account factors such as sunlight, ventilation and heat loss in the building to develop an optimization plan. The simulation results show that the energy consumption of buildings with optimized thermal environment design is significantly reduced and the indoor thermal comfort is greatly improved. Visual tools effectively help the design team identify problem areas and provide intuitive data support for all parties during the design process. The optimization method of building thermal energy environment based on image visual visualization provides a new idea for the regeneration design of industrial heritage landscape, which helps to realize the dual goals of protecting the historical value and meeting the needs of modern environmental protection.

Thermoreflectance property of gallium nitride

Based on the principle of thermoreflectance (TR) and experimental data, we have determined the TR coefficients of GaN in the visible and near-ultraviolet spectrum range. The results indicate that the TR coefficient of GaN is larger, approximately when the illumination wavelength falls within the near-ultraviolet range. However, within the visible spectrum, the TR coefficient is low, ranging between to . This suggests that GaN is more responsive to temperature changes within the near-ultraviolet spectrum. The paper provides a physics-mechanism-based explanation for this phenomenon. These results have implications for the thermal design and analysis of GaN-based microelectronic devices.

Differential Walk on Spheres

We introduce a Monte Carlo method for computing derivatives of the solution to a partial differential equation (PDE) with respect to problem parameters (such as domain geometry or boundary conditions). Derivatives can be evaluated at arbitrary points, without performing a global solve or constructing a volumetric grid or mesh. The method is hence well suited to inverse problems with complex geometry, such as PDE-constrained shape optimization. Like other walk on spheres (WoS) algorithms, our method is trivial to parallelize, and is agnostic to boundary representation (meshes, splines, implicit surfaces, etc. ), supporting large topological changes. We focus in particular on screened Poisson equations, which model diverse problems from scientific and geometric computing. As in differentiable rendering, we jointly estimate derivatives with respect to all parameters---hence, cost does not grow significantly with parameter count. In practice, even noisy derivative estimates exhibit fast, stable convergence for stochastic gradient-based optimization, as we show through examples from thermal design, shape from diffusion, and computer graphics.

Electrical Tortuosities of Porous Structures Based on Triply Periodic Minimal Surfaces and Honeycombs for Power-to-Heat Systems

Power-to-heat (P2H) systems offer an efficient solution for decarbonization by facilitating the integration of renewable energy into the industrial, heating, and transport sectors. Its key requirements include high thermal efficiency and an appropriate electrical resistivity to meet application-specific electrical needs. When designing P2H systems, materials and electrical boundary conditions are often limited by application-specific requirements, whereas geometric structures offer high degrees of freedom. While thermal design calculations are often straightforward due to a variety of available Nusselt and pressure loss correlations, simplified design pathways, particularly for porous structures, are lacking in electrical design. Given the wide range of geometric degrees of freedom for porous structures and the fact that detailed modeling involves substantial computational effort, this work employed electrical tortuosity to capture and correlate the geometry-dependent impacts on the effective electrical resistance in a compact way. Honeycomb and triply periodic minimal surface (TPMS)-based structures were selected for this purpose, as they are characterized by high specific surfaces, allowing for high total heat transfer coefficients. The results show that the effective electrical resistance of both TPMS and honeycomb structures can be adjusted by the geometric structure. It was found that the electrical tortuosities of the investigated TPMS structures are nearly identical, while honeycomb structures show slightly higher values. Furthermore, the electrical tortuosity is mainly a function of the void fraction and does not change with the specific surface when the void fraction is kept constant. Finally, correlations for electrical tortuosity depending on geometric parameters with a mean error below 5% are derived for the first time, thereby providing a basis for simplified and computationally efficient electrical design calculations for P2H systems.

Multi-step thermal design of microwave vacuum heating to basaltic regolith simulant towards lunar base construction

Humanned exploration and extended stay on the Moon are the hottest challenges today. We report highly robust materials by microwave heating under high-vacuum conditions (10− 3 Pa) from a basaltic regolith simulant (FJS-1) to ensure the feasibility of lunar infrastructure construction. The violent degassing dynamics were revealed by monitoring vacuum pressure during heating and analyzing the compounds evolved from basaltic silicate compounds: thermal pyrolysis of silicate compounds became more pronounced above 1000 oC, leading to a catastrophic deformation accompanied by forming countless pores of several hundred µm sizes. The preferential formation of the magnetite phase in vacuum heating dominantly caused the radical change in microwave absorption capacity compared with conventional heating routes using an electrical furnace in atmospheric conditions. Besides, the in-situ measurement of dielectric properties during microwave vacuum heating clarified the increase in one order of magnitude from 100 to 1000 oC. Based on the presumed phenomena during microwave-vacuum heating for basaltic regolith, we propose a new thermal design concept to overcome the practical limitations of microwave technology. The multi-step temperature profile successfully fabricated a highly robust product that demonstrated world-class mechanical performance, equivalent to the compressive strength of 65 MPa without any vigorous hydrostatic cold press as a pre-treatment.

Modeling Thermal Impedance of IGBT Devices Based on Fractional Calculus Techniques

The thermal impedance characteristics of insulated gate bipolar transistor (IGBT) modules are critical for the thermal management and design of electronic devices. This paper proposes a fractional-order equivalent thermal impedance model, which is inspired by the correlation between multi-time-scale dissipation characteristics of heat conduction processes and fractional calculus. The fractional-order equivalent thermal impedance model is derived based on the connection between fractional-order calculus and the Foster thermal network model in mathematical operations, with only two parameters to be identified: heat capacity C and fractional order α. Moreover, this paper provides a parameter identification method for the proposed fractional-order equivalent thermal impedance model based on the multi-objective particle swarm optimization (MOPSO) algorithm. In order to validate the effectiveness and superiority of this work, experiments and comparative works are provided in this paper. The results indicate that the fractional-order equivalent thermal impedance model can accurately describe the frequency domain characteristic curves of the thermal impedance of the Foster thermal network model for IGBT modules, with the difference between the amplitude frequency characteristics not exceeding 1 dB and the difference between the phase frequency characteristics not exceeding 1° within the operating frequency range of (1 kHz, 1 MHz).

Unobstructive and safe-to-wear watt-level wireless charger

A wearable microgrid that centralizes and distributes harvested energy across different body regions can optimize power utilization and reduce overall battery weight. This setup underscores the importance of developing cable-free wireless power transfer (WPT) systems for mobile and portable devices to eliminate the risks posed by wired connections, especially in dynamic and hazardous environments. We introduce a thin, stretchable, and safe hand band capable of watt-level wireless charging through the widely adopted Qi protocol operating at 130 kHz. The implementation of non-adhesive fabric encapsulation serves to protect the 50-μm-thin spiral copper antenna from mechanical strain, ensuring an overall hand band stretchability of 50%. We also create a stretchable “Ferrofabric”, characterized by a magnetic permeability of 11.3 and a tensile modulus of 75.3 kPa, that provides magnetic shielding for the antenna without compromising wearability. The “Ferrofabric” improves the coil inductance but induces core loss in AC application. By fully understanding and managing loss mechanisms such as the skin effect, proximity effect, core loss, and joule heating, we achieve a wireless charging efficiency of 71% and power delivery of 3.81 W in the kHz frequency range. Our WPT hand band is unobstructive to hand motion and can charge a handheld smartphone as fast as a desktop charger or power a battery-free chest-laminated e-tattoo sensor, with well-managed thermal and electromagnetic safety. Through a holistic electromagnetic, structural, and thermal design, our device culminates in a safe, rugged, and versatile solution for wearable WPT systems.

Numerical model of a top-blown rotary converter preheating and charge heating with an oxy-fuel burner

Background The present work is conducted in the framework of the SisAl Pilot EU project, which aims to optimize silicon production in Europe by recycling materials and using carbon-emission-friendly technology. Silicon production experiments were conducted on laboratory and pilot scales in different types of furnaces, including top-blown rotary converters (TBRC) used as chemical reactors for molten slag-metal mixtures. In addition to experimental work, process optimization also relies on numerical modelling. Methods In this study, COMSOL Multiphysics® was used for the numerical testing of a new thermal design of TBRC by simulating its preheating and charge heating owing to an external heat source provided by an oxy-fuel burner. Results and conclusions The risk of slag solidification in TBRC during the aluminothermic reduction of silica was assessed. The model predicts that, with a useful burner power of 600 kW, the empty TBRC can be preheated to 1650°C in less than 30 min. Based on this model, the optimum burner power for maintaining the TBRC charge in a liquid state was determined. The influence of the TBRC inclination angle and its rotation frequency was studied numerically.

Thermal Performance Analysis and Design Evolution of Ventilated Stone Facades: A Case Study of the Praski Student House (Akademik Praski) in Warsaw

The rationale for this work arose from the urgency of improving the energy efficiency of buildings at the design stage, given the changing requirements of energy efficiency standards such as the Polish Technical Conditions (WT 2014 and WT 2020). This research is novel as there is currently limited information available on the improvement of the thermal performance of ventilated stone facade systems, although they are now widely used due to their practical and aesthetic advantages. The first objective of this work is to evaluate the thermal performance of the ventilated facades of the Praski Student House (Akademik Praski) and to assess how certain design variations can help achieve a lower level of energy consumption. Using a comprehensive case study approach, this study provides accurate thermal calculations of the facade to assess its global thermal insulation coefficient (Rt) and thermal transmittance (Uc). The improvement in the actual U-value from the original design is as follows: the U-value is reduced from 0.33 originally to 0.228 for WT 2014 and to 0.198 for WT 2020, showing a reduction of about 30.9% and 13.2%, respectively. These results indicate the energy efficiency of increased insulation thickness and optimally oriented air gap dimensions. The practical contributions of this research are valuable for architects, engineers, and contractors involved in the design and construction process of buildings aiming to achieve near-zero energy buildings (nZEBs), including concrete suggestions on how to improve current construction practices as well as material recommendations. There is a need for durability studies, for example to assess the performance of such facades under different climatic conditions, as part of future work to support these findings.

Design and application of graphite film with high thermal conductivity in SAR antenna

Abstract The rapid development of SAR antenna in the remote sensing field has put forward the test of antenna thermal design. In this paper, according to the load of a certain type of extravehicular SAR antenna, a reasonable thermal design is carried out for its high heat consumption and external heat flux. A high thermal conductivity graphite film is used for heat expansion. The test shows that the mounting plate heat expansion capacity difference is 28°C with and without graphene film, with 40W heat consumption applied in 180mm transmission distance. The simulation analysis and thermal balance test are carried out. The results show that the high thermal conductivity graphite film can rapidly extend the heat of the single unit of the SAR antenna to the whole antenna, and make the antenna meet the temperature requirement in orbit, which proves the rationality of thermal design. This paper is useful for the thermal control design of a satellite-borne SAR antenna.

The research of thermal environment test methodology for the Mars probe product

Abstract In order to ensure the success of the Mars exploration mission, it is necessary to accurately simulate the unique environment on the surface of Mars in a ground test and verify the effectiveness of the thermal control measures of the Mars rover. This paper proposes a thermal balance test method that can simultaneously simulate environmental factors such as Martian surface gas atmosphere, wind speed, pressure, solar radiation, and atmospheric temperature. This proposed test method meets the thermal design verification requirements of component-level products. Compared with similar large-scale facilities, the test cost is low, and the implementation efficiency is high. Furthermore, the influence of the Martian wind field on the surface temperature distribution of the product under both the Martian day and night environment was investigated using the proposed test method. The research results show that although the atmospheric pressure on the surface of Mars is much lower than the surface of the Earth, the Martian wind will still form forced convection heat transfer on the surface of the probe and its auxiliary products, which will affect the heat distribution of the products. In the thermal control design of the products, it is necessary to consider the impact of all the above environmental factors and carry out corresponding comprehensive environmental test verification.

Design and initial test results of a space-bound flux pump to energize the Hēki mission’s superconducting magnet

Despite repeated proposals to utilize superconducting magnets in space since at least the 1970s, examples of their use remain scant. One of the technical challenges is to maintain suitable cryogenic temperatures on a spacecraft. This challenge can be alleviated by the use of flux pumps to reduce the required cryogenic cooling power needed to energize the superconducting magnet. This paper describes the design and initial test results of the flux pump to fulfill the requirements of the Hēki mission that will operate a high-temperature superconducting magnet on an external platform of the International Space Station. A transformer-based, self-rectifier architecture was chosen for the flux pump. An effective circuit model used to design its electromagnetic properties and finite-element modelling used in its mechanical and thermal design. Liquid nitrogen tests were used to demonstrate that the electrical performance of the flux pump meets requirements. Higher-fidelity tests using flight-like copies of the hardware and software were undertaken and validated the thermal modelling. These tests also featured the continuous operation of the flux pump in a conduction-cooled setting for over 100 hours, reflecting an inherent reliability of this technology. Whilst further testing and flight qualification remains to be completed, we anticipate an on-orbit demonstration of this flux pump technology in February 2025. Such a demonstration will signal a maturing of this emerging superconducting technology for both in-space and terrestrial applications.

Thermal design of a solid-state power amplifier at Q-band

Abstract It is very difficult to cool a new solid-state power amplifier at Q-band, which is composed of some high-power monolithic millimeter-wave integrated circuit chips. Cu/Diamond carriers are used as the heat sinks of the chips, and two layers of heat pipes are sealed in the chassis to reduce the thermal resistance of the amplifier. The thermal design scheme is proved useful by simulating Flotherm and the temperature data from the infrared imager. The study provides an available way for the thermal design of a solid-state power amplifier.

Unit-Based Optimization Approaches for the Thermal Design of Residential Buildings

Building regulations, scarcity of energy, and climate change have forced designers to find energy-efficient design alternatives for the buildings. Current regulations focus solely on the total energy requirement of the building without considering the fact that the energy performance varies greatly across different units of the building, which, in turn, causes discomfort among the occupants. Conventional optimization approaches created based on these regulations, therefore, miss the capability to cope with this issue. Resolving the problem of varying thermal performance within the units requires the introduction of unit-based optimization approaches. This study elaborates on revealing the inadequacy of the conventional optimization approach and proposes two alternative approaches that take the issue into account. Within this context, the thermal design a typical five-story residential building with six apartment units on each floor was optimized according to the conventional optimization approach. A simulation-based optimization system consisting of a Distributed Evolutionary Algorithms in Python (DEAP) optimization tool and Energy Plus was employed. The differences in the energy performances of different units were observed for three different climate conditions. Afterwards, two different approaches having the objectives of optimizing the overall building performance and balancing the variance within units were proposed: (i) single-phase multi-objective optimization and (ii) multi-phase single-objective optimization. The outcomes of the study demonstrated that the multi-phase single-objective optimization provided better results.

Thermal design of a frequency hopping processor

Abstract To solve the difficult problems in the thermal design of a new frequency-hopping processor, such as high heat consumption, concentrated local heat flux of the device, and large thermal resistance, a thermal design scheme was proposed to optimize the structure design and enhance the thermal conductivity of PCB board. At the same time, a combined scheme of copper water heat pipe-thermal expansion plate was used. Flotherm was used for thermal simulation and a thermal balance experiment under vacuum conditions was designed. Then the temperature of the frequency-hopping processor was measured experimentally to further verify the rationality of the design scheme. The combined scheme of copper water heat pipe-thermal expansion plate will guide the thermal design of this type of frequency hopping processor.

Unlocking Heat Transfer Potential in Multi-Sided Porous Geometries: A Study on Magnetothermal Effects and Entropy Generation

This study investigates heat transfer efficiency and irreversibility generation in multi-sided porous thermal systems filled with a Cu-Al2O3-water hybrid nanofluid. The research examines convective heat transfer across various polygonal geometries, ranging from four-sided to infinitely-sided (circular) structures, aiming to maximize thermal system performance intended for scientific and industrial applications. For a standardized comparison, the fluid volume and active heating and cooling lengths are kept constant for all the geometries considered. The analysis includes varying flow-controlling variables like the modified Rayleigh number (Ram), Hartmann number (Ha), and Darcy number (Da) to evaluate how they affect heat transfer efficiency and entropy generation, including total, magnetic, and viscous entropy. The numerical simulations, conducted using the finite element approach, explore Ram values ranging from 10 to 104, Ha from 0 to 70, and Da from 10-4 to 10-2. Streamline and isothermal contours analyze flow behavior, while heatline tools reveal thermal energy transport dynamics. Results show up to a 20% improvement in heat transfer efficiency in optimized configurations. Key findings indicate that hexagonal structures can be viable alternatives to circular tubes in space-constrained applications, offering comparable thermal performance. Interestingly, pentagonal cavities exhibit the highest irreversibility due to symmetry loss. The study offers insightful information for enhancing thermal system design in various industrial settings, particularly for applications requiring efficient heat transfer in limited spaces.

Thermal Bed Design for Temperature-Controlled DNA Amplification Using Optoelectronic Sensors.

Loop-Mediated Isothermal Loop-Mediated Isothermal Amplification (LAMP) is a widely used technique for nucleic acid amplification due to its high specificity, sensitivity, and rapid results. Advances in microfluidic lab-on-chip (LOC) technology have enabled the integration of LAMP into miniaturized devices, known as μ-LAMP, which require precise thermal control for optimal DNA amplification. This paper introduces a novel thermal bed design using PCB copper traces and FR-4 dielectric materials, providing a reliable, modular, and repairable heating platform. The system achieves accurate and stable temperature control, which is critical for μ-LAMP applications, with temperature deviations within ±1.0 °C. The thermal bed's performance is validated through finite element method (FEM) simulations, showing uniform temperature distribution and a rapid thermal response of 2.5 s to reach the target temperature. These results highlight the system's potential for applications such as disease diagnostics, biological safety, and forensic analysis, where precision and reliability are paramount.

Research on assessing and enhancing indoor thermal and air conditions within typical elementary school classrooms in southern China

The thermal design of buildings in hot summer and cold winter regions must meet the requirements of thermal insulation in summer and heat preservation in winter. As a vital component of national compulsory education, primary schools must create a good indoor thermal environment for classrooms, which is particularly important for students. Due to the lack of construction standards and limited research on Chinese regions with hot summers and cold winters, policymakers have no comprehensive and efficient approach to creating optimal indoor thermal conditions in primary school classrooms. Therefore, based on the climate conditions of hot summer and cold winter areas, this study conducted field surveys in primary and secondary schools in hot summer and cold winter areas, summarized and analyzed the current situation of the surveyed classrooms and users' subjective evaluation of the indoor thermal environment of classrooms, and summarized the current hot summer and cold winter conditions. Problems in classrooms in primary and secondary schools in the region are clarified, and the research direction of construction strategies is clarified. The study found that most of the school hours in summer and winter were in a poor indoor thermal environment without refrigeration equipment. This study adjusted the school leaving time to 17:20 in summer and 17:00 in winter by adjusting the school leaving time to reduce the time of adverse thermal environment.

Experimental investigation of an additively manufactured cold plate for multi-chip module cooling generated using the homogenization approach to topology optimization

The homogenization approach to topology optimization is promising for generating high-performance, liquid-cooled cold plates due to its ability to create sub-resolution features by optimizing the spatial distribution and porosities of physical microstructures. This optimization capability has been demonstrated for the design of compact microchannel heat sinks under uniform heating conditions. However, there is a need to understand its applicability for practical applications involving complex boundary conditions posed by modern electronics packaging requirements. This work performs the topology optimization, design for manufacturing, fabrication, and experimental testing of a liquid-cooled cold plate for an application-representative multi-chip module with eight devices. The cold plate design requirements and boundary conditions involve eight equally spaced heat generating sources and liquid inlet/outlet ports that are off-center, introducing flow distribution challenges to the thermal design. A topology optimization algorithm is developed using the homogenization approach with circular pin fins chosen as the microstructure. An empirical permeability correlation for pin fins is developed which is implemented in the porous media flow model of the topology optimization algorithm to simulate pressure drop across additively manufactured pin fins. In addition to the topology optimized designs, a benchmark cold plate design with uniformly distributed 1.2 mm diameter pin fins, representative of the feature dimensions currently adopted in applications for the investigated boundary conditions, is also evaluated. Comparison of the topology optimized cold plate generated using the design freedom brought by additive manufacturing to the benchmark design highlights the optimizer’s ability to uniformly distribute the coolant amongst the heated regions. The maximum base temperature rise is 35.5 °C for the benchmark design versus 6.6 °C for the topology optimized design. Flow uniformity combined with the high convective heat transfer of the sub-resolution fins and channels in the vicinity of the heated regions keep the device temperatures low. The topology optimized cold plate is additively manufactured and experimentally tested at various flow rates. The experimental results match well with the model predictions, with a mean absolute percentage error of 5.5 % and 9.7 % for pressure drop and thermal resistance respectively, indicating that the optimal performance promised by the algorithm can be realized using additively manufactured parts. The work presented here demonstrates the overall process flow for the homogenization approach in leveraging the capabilities of additive manufacturing to generate high-performance liquid cold plates for practical applications.