Maximum Temperature Reduction Research Articles

Level-set topology optimization of heat sinks with phase-change material

Phase-change materials (PCMs) excel in storing significant thermal energy through the latent heat of fusion during phase changes. However, they often suffer from low thermal conductivity, requiring the incorporation of materials with higher thermal conductivity to overcome this limitation. In this study, we employ the level-set method to topologically optimize the distribution of both PCM and high thermal conductivity materials within heat sinks.The heat transfer process is modeled as an unsteady diffusion problem, with PCM integrated using the apparent heat capacity method. The finite element method, implemented using FEniCS, is utilized to compute the temperature distribution at each time step. The optimization problem is solved using ParaLeSTO, a modular topology optimization software written in C++, seamlessly interfacing with FEniCS through its Python interface.To compute boundary point sensitivities for level-set topology optimization, the discrete adjoint method is employed, combining a perturbation scheme with automatic differentiation. The proposed methodology is first applied to a two-dimensional example of temperature oscillation minimization with a heat flux boundary condition, drawn from existing literature. Subsequently, a two-dimensional example with multiple volumetric heat sources is studied, followed by an extension to a three-dimensional design domain.Comparisons with optimized designs without PCM, serving as a reference, highlight the superior thermal performance of heat sink designs with PCM. The results showcase a maximum temperature reduction of up to 42%, a mean temperature reduction of up to 42%, and a temperature variance reduction of up to 94%. This research contributes to heat sink design by offering discrete solutions that significantly improve thermal performance as compared to designs without PCM. Its impact extends to addressing crucial challenges in thermal management across various applications, including automotive cooling systems, aerospace components, and consumer electronics.

Performance analyses on the air cooling battery thermal management based on artificial neural networks

Air cooling thermal management technology is a lightweight and cost-effective approach for managing heat in power battery packs for electric ships. However, it suffers from significant drawbacks such as poor temperature control and excessive noise generation. To address these challenges, this study proposes a method that combines fluid dynamics and artificial neural networks (ANNs) to optimize the thermal management and aeroacoustic performance of the air cooling battery thermal management system (BTMS) for marine power batteries. Initially, a thermal-flow coupled model and an acoustic model for the BTMS were developed to investigate the impact of system structural parameters (battery spacing d, and main channel inclination angle θ) and operating parameter (system inlet velocity v) on the thermal management performance indicators (maximum temperature Tmax, and maximum temperature difference ΔTmax) as well as the aeroacoustic performance indicator (overall sound pressure level, OSPL). Subsequently, a relationship between the system structural and operating parameters and performance indicators was established using the 50-layer Residual Network (ResNet-50) model, enabling accurate and rapid prediction of the system thermal management and aeroacoustic performance. Furthermore, by combining ResNet-50 with the evaluation method of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), this study successfully obtained the optimal system structure and operating parameters. The research indicates that keeping the remaining parameters constant, increasing the battery spacing results in higher maximum temperature and maximum temperature difference, while decreasing the overall system sound pressure level. Conversely, increasing the main channel inclination angle results in lower maximum temperature and maximum temperature difference, but higher overall system sound pressure level. In addition, increasing the inlet velocity will result in higher maximum temperature and maximum temperature difference, as well as higher overall system sound pressure level. The optimal case were found to be a main channel inclination angle θ = 3°, battery spacing d = 2 mm, and inlet velocity v = 10 m⋅s−1. Compared to the base case, the optimal case shows a maximum temperature reduction of 10.63 K, a maximum temperature difference reduction of 9.41 K, and an overall sound pressure level reduction of 4.6 dB. The prediction errors for these values are 0.08 %, 2.64 %, and 1.36 % respectively. This research demonstrates an effective and rapid approach based on fluid dynamics and ANNs in the design and optimization of BTMS.

Experimentally thermal management of low-concentrated photovoltaic via new configurations of dimple/trapezoidal heat spreaders of different sizes

ABSTRACT This study experimentally investigates the influence of dimple (DHS), flat plate (FHS), and trapezoidal heat spreader (THS) cooling systems on thermal regulation of low concentrated solar cell (LCPV). It is performed at 1.5 and 2 HS/PV area ratio and HS thicknesses 1 and 2 cm under 3100 W/m2 solar irradiance. Results reveal that using DHS outperforms other cooling systems in terms of cell temperature and electric performance. Increasing HS area ratio and thickness significantly enhances PV performance. DHS, PHS, and THS achieve maximum PV temperature reduction of 44.4, 43.2, and 41°C and PV efficiency improvement of 16.89%, 14.87%, and 13.9%, respectively.

Integration of prolonged phase-change thermal storage material and radiative cooling textile for personal thermal management

Efficient passive thermal regulation clothing is of great importance for personal thermal comfort in extremely hot environments. Phase-change textiles have been made for personal thermal regulation, however, achieving prolonged thermal comfort remains challenging due to their limited latent thermal storage duration. Here, a bilayer polyvinyl butyral (PVB) composite textile, integrating prolonged phase-change thermal storage and radiative cooling, is fabricated for personal thermal regulation. The PVB composite textile has a high reflectivity of 90.1 % in the solar wavelength range and a high emissivity of 95.7 % in the atmospheric window. More importantly, encapsulating 70 wt% of phase change microcapsules (PCMC) into the PVB membrane (denoted by PVB-PCMC70) gives a total enthalpy of fusion 124.3 J g−1, which compensates for the deficiency in radiative cooling power during the day. This results in a maximum additional temperature reduction of 10.4 °C compared with textile without the PCMC. Furthermore, the PVB composite textile demonstrates a capacity for effectively mitigating abrupt temperature fluctuations, ensuring sustained thermal comfort throughout the daytime. Moreover, the PVB composite textile shows practical applicability, including washability, flexibility, thermostability, moisture permeability and breathability.

Multi-Strategical Thermal Management Approach for Lithium-Ion Batteries: Combining Forced Convection, Mist Cooling, Air Flow Improvisers and Additives

Maintaining the peak temperature of a battery within limits is a mandate for the safer operation of electric vehicles. In two-wheeler electric vehicles, the options available for the battery thermal management system are minuscule due to the restrictions imposed by factors like weight, cost, availability, performance, and load. In this study, a multi-strategical cooling approach of forced convection and mist cooling over a single-cell 21,700 lithium-ion battery working under the condition of 4C is proposed. The chosen levels for air velocities (10, 15, 20 and 25 m/s) imitate real-world riding conditions, and for mist cooling implementation, injection pressure with three levels (3, 7 and 14 bar) is considered. The ANSYS fluent simulation is carried out using the volume of fluid in the discrete phase modelling transition using water mist as a working fluid. Initial breakup is considered for more accurate calculations. The battery’s state of health (SOH) is determined using PYTHON by adopting the Newton–Raphson estimation. The maximum temperature reduction potential by employing an airflow improviser (AFI) and additives (Tween 80, 1-heptanol, APG0810, Tween 20 and FS3100) is also explored. The simulation results revealed that an additional reduction of about 11% was possible by incorporating additives and AFI in the multi-strategical approach. The corresponding SOH improvement was about 2%. When the electric two-wheeler operated under 4C, the optimal condition (Max. SOH and Min. peak cell temp.) was achieved at an air velocity of 25 m/s, injection pressure of 7 bar with AFI and 3% (by wt.) Tween 80 and a 0.1% deformer.

Enhancement in thermo-hydraulic performance of ceramic-based disk heat sink with fractal micro-channels via double layering, hybrid nanofluids, and cross-sectional convergence

The focus of this paper is to further improve the thermo-hydraulic performance of a disk heat sink with fractal-like microchannels by introducing four distinct modifications: incorporating convergent cross-sections in microchannels, implementing double layering, utilizing a high-conductivity material (AlN ceramic) for the heat sink, and integrating hybrid nanofluids. Hybrid nanofluids, encompassing Aluminum Oxide-Graphene, Aluminum Oxide-Copper, and Copper-Graphene, each with varying volume fractions and an overall volume fraction of 2 % and 4 %, were systematically evaluated. The cumulative impact of these modifications on the four levels fractal-like microchannel heat sink's thermo-hydraulic performance was rigorously assessed through numerical simulations. The flow rate ranges from 300 to 600 ml/min, corresponding to an inlet Reynolds number in the range of 3014 to 6018.The findings reveal that the increase around 10 % in Nusselt number can be achieved through implementing converging cross-sections at levels 3 and 4. Substituting silicon with AlN ceramic leads to a reduction in maximum temperature from 1.85 to 2.58 ℃, depending on the flow rate. Under a heat flux of 40 W/cm2, double layering can reduce thermal resistance by 0.2. Most effective configuration involves a double-layered fractal microchannel with convergent cross-sections at levels 3 and 4, employing AlN ceramic as the material, and utilizing a hybrid water-based nanofluid with a volume fraction of Cu 3 %-Al2O3 1 %. This configuration achieves a notable reduction in maximum temperature by 11.1 °C and 17.97 °C under heat fluxes of 40 and 80 W/cm2, respectively, at a volumetric flow rate of 300 ml/min.

The influence of using MWCNT/ZnO-Water hybrid nanofluid on the thermal and electrical performance of a Photovoltaic/Thermal system

Rising photovoltaic panel temperatures significantly compromise their performance and lifespan, leading to lower power output and conversion efficiency. Consequently, research on PV panel cooling strategies has gained momentum to address these challenges. This study presents an experimental investigation of a photovoltaic/thermal system's performance using a cooling fluid – a multi-walled carbon nanotube/zinc oxide nanofluid. A comparative analysis is conducted on three PV panels: uncooled, water-cooled, and nanofluid-cooled. Notably, our experiment employed a low mass flow rate (0.156 kg/min), significantly lower than typical values reported in prior literature, and a 0.1 wt% nanofluid concentration. Our primary objective was to evaluate the efficacy of MWCNT/ZnO nanofluid in enhancing the thermal management and overall efficiency of a PVT system. This study focused on the impact of nanofluid on electrical efficiency, thermal efficiency, and exergy performance of the system. The results demonstrate significant improvements. The key findings of this investigation reveal that MWCNT/ZnO nanofluid effectively improves the base fluid's thermal properties, leading to substantial enhancements in both electrical and thermal efficiencies of the PVT system. Compared to the uncooled panel, the nanofluid achieved a maximum temperature reduction of 14.9 °C on the panel surface, a 16.8 % increase in average electrical efficiency, and a maximum thermal efficiency of 51.3 % compared to 45.5 % for water cooling. Moreover, the average overall efficiency of the system with nanofluid cooling reached 58.7 %. Furthermore, the implementation of MWCNT/ZnO nanofluid cooling resulted in a significant boost in maximum overall exergy efficiency, surpassing water cooling and conventional systems by 7 % and 27 %, respectively. Additionally, a 3.5 % reduction in entropy generation and exergy destruction was observed compared to the conventional system.

Exploring BTI aging effects on spatial power density and temperature profiles of VLSI chips

The Long-term reliability of a chip, encompassing factors like bias temperature instability (BTI), plays a substantial role in the chip's operational efficiency and overall lifespan. Most studies primarily center around performance-related aspects like delay and timing impacts, and fewer studies are performed on reliability impacts on the spatial power density and thermal profiles of the chips. In this study, we propose to investigate the BTI impacts on the spatial power density and temperature profiles of VLSI chips for the first time. We assessed the BTI aging impact on the on-chip spatial power density and temperature for two widely used circuit functional blocks (dual port RAM, Discrete Cosine Transform (DCT) block) at T = 130◦C and T = 25◦C to account for the worst-case BTI degradation, using degradation-aware cell libraries for a 10-year aging scenario. Furthermore, we showcased the essential role of BTI aging-aware timing analysis in evaluating the impact of BTI aging on total power, on-chip spatial power density, and thermal maps. Neglecting this aspect can result in a substantial underestimation of the results related to the parameters mentioned above. We developed a power map generation method from the circuit layout and power analysis from EDA tools. We demonstrate that both circuits’ maximum power density reduction is approximately 12 % and 20 %, respectively. Furthermore, to analyze the BTI impact on spatial temperature, we built the heat transfer model using a multiphysics tool to imitate a real chip (Intel i7-8650U) and performed thermal simulations to evaluate the spatial thermal map. The resulting maximum temperature reduction for both these circuits is approximately 10 % and 12 %, respectively, which is quite significant.Our analysis has further unveiled that, in the context of a specific circuit, the position of maximum power density and the occurrence of a hot spot remains consistent over time, unaffected by aging. However, it's important to note that these positions can vary between different circuits, primarily influenced by the workload the circuit is currently handling. Furthermore, our findings demonstrate that the effects of Bias Temperature Instability (BTI) aging are significantly more pronounced when the circuit operates at higher temperatures (T = 130◦C) compared to lower operating temperatures (T = 25◦C).

Application of CNTs/H2O nanofluid and the wavy fin with dimples in thermal management of CPU: A numerical modeling of hybrid passive cooling

A study was conducted utilizing computational fluid dynamics (CFD) to explore a novel cooling technique for the central processing unit (CPU), involving the use of carbon nanotubes (CNTs)/H2O nanofluid-fin heat sinks with dimples. Different fin heat sink designs with varying dimple arrangements were created using AutoCAD software. The three-dimensional flow, heat transfer, and mass transfer of the nanofluid within the liquid block were simulated using a finite volume-based CFD code. The study investigated the influence of different nanoparticle concentrations and dimple arrangements on cooling performance, heat transfer coefficient, pumping power, and thermal efficiency. The results revealed that the maximum temperature reduction on the CPU's top surface was approximately 13.1 K for multi-walled carbon nanotube/H2O nanofluids and 14.34 K for single-walled carbon nanotube (SWCNT)/H2O nanofluids. The best thermal efficiencies were achieved using SWCNT (2%)/H2O with three rows of dimples on each fin, resulting in an 8.5% improvement in heat sink performance at Re = 1,500 and an 8.8% improvement at Re = 2,000 compared to fins without dimples. However, it was observed that increasing the number of dimples on the fins led to an increase in pressure drop within the liquid block, necessitating additional pumping power. The simulation results aligned well with earlier experimental data and numerical studies in terms of cooling and heat transfer.

Design and Numerical Study of Microchannel Liquid Cooling Structures for Lithium Batteries

To investigate the microchannel liquid cooling system of 18650 cylindrical lithium battery packs, cooling systems with varying numbers of microchannels are developed and they are analyzed through numerical simulations using COMSOL software. The findings reveal that lower coolant inlet temperatures correspond to lower maximum temperatures during discharge, with temperatures decreasing closer to the inlet. When the coolant passes through a 3.6 mm diameter or at an inlet flow rate of 0.1 m s−1, an increase in Reynolds number results in a decrease in the highest temperature of the cells. However, this temperature reduction slows down when Re exceeds 400. The annular channel cooling structure demonstrates superior cooling effects and temperature uniformity. Optimization opportunities exist to reduce the number of inlets. The dual‐inlet and dual‐outlet cooling structure has been enhanced by adjusting the number of channels in the annular channel design. This modification has resulted in a maximum temperature reduction of 4.62 K and a temperature difference of less than 5 K compared to the initial reference group, demonstrating effective cooling performance.

The Assessment of Thermal Comfort Performance in Bamboo Ecotourism Infrastructure in the Tropical Climate of Malaysia

Ecotourism has become a growing trend, offering a platform for raising awareness of environmental issues in the tourism industry. One of the principles of ecotourism is relying on environmentally friendly infrastructure to prevent environmental degradation. The shift towards ecotourism has highlighted the significance of sustainable practice and infrastructure design in tourism. Bamboo is gradually renowned due to its role in carbon sequestration, bringing hope to the natural environment despite the slow acceptance by society. Assessing the thermal comfort performance takes on added value in the context of encouraging bamboo utilization for sustainable practice. As bamboo gains recognition for its potential in environmental protection, its thermal comfort attributes could encourage its adoption in future infrastructure. Hence, this study examines the thermal comfort performance in bamboo buildings in Malaysia using various design approaches in the same microclimate. Fieldwork was conducted to analyze the indoor and outdoor temperatures in three different chalets in Tadom Hill Resort, Banting, namely Gendui Chalet, Semantan Chalet, and Hakka Village. Generally, findings concluded that the indoor temperatures are higher than the indoor thermal conditions indicated in Malaysia Standard, MS1525:2007. Findings also indicate that the maximum temperature reduction is 2.4°C, 4.1°C, and 4.6°C for Gendui Chalet, Semantan Chalet, and Hakka Village, respectively. Ultimately, this study seeks to emphasize the feasibility of bamboo as a likely option for building construction, developing, and improving the ecotourism destinations in Malaysia.

Present day and future urban cooling enabled by integrated water management

The process of urbanisation has increased public health risks due to urban heat, risks that will be further exacerbated in future decades by climate change. However, the growing adoption of integrated water management (IWM) practices (coordinated stormwater management of water, land, and resources) provides an opportunity to support urban heat amelioration through water supply provision and irrigated and vegetated infrastructure that can provide cooling benefits. This study examines the thermal impacts of future implementations of IWM for nine Australian cities based on a review of Government policy documents in the present and over two future time frames (2030 and 2050) under different greenhouse gas emission scenarios (SSPs 1.2-6, 3.7-0 and 5.8-5). Statistical analysis of the future climate data using historical data shows that future warming is nuanced, with changes variable in both time and place, and with extremes becoming more pronounced in future. We have developed a unique approach to morph the future climate projections onto historical data (derived from the ERA5 Reanalysis product) for the 2010-2020 period. Additionally, we use locally appropriate Local Climate Zones (LCZs) for Australian cities, resulting from a holistic and global approach that is widely adopted by the urban climate modelling community. We developed scenarios for business-as-usual as well as implementation of moderate and high levels of IWM across each of the Australian LCZs and modelled them using TARGET (The Air temperature Response to Green infrastructure Evaluation Tool). Results generated at the LCZ level are aggregated to Australian statistical areas (SA4, the largest sub-city area) and city-wide levels. The thermal impacts associated with the various degrees of IWM were marked and geographically differentiated, depending on the climatic characteristics of the various cities. For the current climate, high IWM intervention provided reductions in annual mean daily maximum temperature ranging from -0.77°C in Darwin, up to -1.86°C in Perth. Generally, the drier southern cities of Sydney, Canberra, Albury, Melbourne, Adelaide, and Perth produced the greatest thermal response to implementation of IWM and the more tropical cities with higher rainfalls the least response. For some southern cities cooling was > -3.0°C at the time of maximum summer temperatures. Interestingly high levels of IWM in winter produced modest warming of minimum overnight temperatures, especially for the cooler southern cities. The cooling benefits of IWM were seen across all future climate scenarios and are a real opportunity to offset-projected temperature increases resulting from climate change.

Research on the influence and optimization of sunshade effect on radiative cooling performance

Intense solar radiation is the main reason why radiative cooling is difficult to achieve during the daytime, as the radiative heat flux from the sun will offset the heat emitted by the cooler. Most previous studies have focused on providing coolers with high solar reflectance and high mid-infrared spectral emissivity by designing photonic structures. In this study, a macroscopic sunshade device based on the solar visual motion trajectory is proposed to reduces the direct solar radiation received by the cooler surface through setting a blocking on the solar path, while hardly affecting the radiative capacity of the cooler. Here, we built a three-dimensional sunshade device simulation model based on the surface-to-surface radiative heat transfer module in COMSOL Multiphysics® software, which can effectively improve the cooling performance of the cooler. Then, using polished aluminum plates, black paint-coated cooler, and reflective radi-cool film to test the impact of macroscopic sunshade device based on the solar apparent motion trajectory on improving the cooling performance of difference coolers. The results verified the effectiveness of the proposed sunshade devices in improving radiative cooling performance, and the results showed that the maximum temperature reduction could reach 3.35 °C, 26.96 °C, and 3.42 °C, respectively.

Role of periodic irradiation and incident beam radius for plasmonic photothermal therapy of subsurface tumors

Plasmonic photothermal therapy (PPTT) is a potential technique to treat tumors selectively. However, during PPTT, issue of high temperature region and damage to the surrounding healthy is still need to be resolved. Also, treatment of deeper tumors non-invasively is a challenge for PPTT. In this paper, the effect of periodic irradiation and incident beam radius (relative to tumor size) for various gold nanorods (GNRs) concentrations is investigated to avoid much higher temperatures region with limiting thermal damage to the surrounding healthy tissue during PPTT of subsurface breast tumors located at various depths. Lattice Boltzmann method is used to solve Pennes’ bioheat model to compute the resulting photothermal temperatures for the subsurface tumor embedded with GNRs subjected to broadband near infrared radiation of intensity 1 W/cm2. Computation revealed that low GNRs concentration leads to uniform internal heat generation than higher GNRs concentrations. The results show that deeper tumors, due to attenuation of incident radiation, show low temperature rise than shallower tumors. For shallower tumors situated 3 mm deep, 70% irradiation period resulted in around 20 °C reduction (110 °C–90 °C) of maximum temperature than that with the continuous irradiation. Moreover, 70% beam radius (i.e., beam radius as 70% of the tumor radius) causes less thermal damage to the nearby healthy tissue than 100% beam radius (i.e., beam radius equal to the tumor radius). The thermal damage within the healthy tissue is minimized to the 1 mm in radial direction and 3 mm in axial direction for 70% beam radius with 70% irradiation period. Overall, periodic heating and changing beam radius of the incident irradiation lead to reduce high temperature and limit healthy tissue damage. Hence, discussed results are useful for selection of the irradiation parameters for PPTT of sub-surface tumors.

Experimental and numerical analysis of PV-PCM integrated with novel shaped corrugated fins

In this paper, performance of a PV-PCM system with novel internal corrugated fins is analysed by dynamic simulation and experiments for the inclinations of 0°, 15°, and 30° against a flux of 750 W/m2 using a solar simulator. The impact of fins (n) is investigated numerically, and the optimal number of fins is found. Performance parameters such as temperature, power output, and efficiency are compared for PV, PV-PCM, and finned PV-PCM systems. The validity of the numerical model is established by comparing the simulated and experimental PV temperatures, which reduces cost and time and allows the numerical models to optimise the design and performance of the system. Results showed that an increase in inclination leads to improved performance of the PV due to an increased convection heat transfer rate. The effect of the fins is pronounced at lower inclinations. Corrugated fins enhance the heat transfer rate compared to traditional flat fins, and the heat transfer enhancement characteristics of corrugated fins within the finned PV-PCM system can provide valuable insights for optimised performance. Compared to the PV-only system, the maximum PV temperature reductions for PV-PCM and finned PV-PCM systems are 30.1 °C and 38.6 °C for θ=0° and 25.23 °C and 34.1 °C for θ=30°. The optimal number of fins is 4 for all inclinations. The maximum efficiency enhancement for optimal systems decreased from 28.15 % at θ = 0° to 22.27 % at θ = 30°. Finally, the experimental performance of finned PV-PCM at a latitude corresponding to Calicut, India, is also conducted.

Development of red mud-modified geopolymer coating with radiative cooling effect for footway application

Radiative cooling coating technology is gaining increasing attention in the context of mitigating urban heat island and tackling global climate change. This paper is concerned with the development of an inorganic geopolymer-based radiative cooling coating using red mud, incorporating varying sizes of TiO2 and hollow glass beads. The developed colored coating demonstrates its radiative cooling capability in reducing the surface temperature by harnessing the potential of red mud. The physico-chemical properties, surface morphology, and element distribution of the coating were characterized by XRD, FTIR, TG-DAT, SEM and EDS. The coating exhibited lower UV (0.0844) and visible reflectance (0.5275) but high NIR reflectance (0.7536), as well as high infrared emissivity of 0.9455, enabling a red color with a CIE value of L* = 74.56, a* = 9.55, and b* = 11.98, and a maximum temperature reduction of 7.3 °C under the climate of Hong Kong. Additionally, the skid resistance, abrasive resistance and adhesion strength of the proposed coating could meet the requirements of standards, indicating a great potential for footway applications.

Study on the characteristics of a novel wrap-around cooled diaphragm compressor for hydrogen refueling station

This study introduces a novel wrap-around cooled diaphragm compressor, designed for employment in hydrogen refilling station. The performance of this innovative compressor is evaluated using a specially developed experimental platform. The analysis focused on the impact of pressure ratio and suction gas temperature on the compressor's performance, and the cooling effect is assessed under varying temperatures of the cooling medium. The findings indicate that both the isentropic and volumetric efficiencies of the diaphragm compressor decrease with an increase in pressure ratio, with maximum values reaching 70% and 65% respectively. Under constant pressure ratio conditions, the exhaust temperature is found to increase with the rise in suction temperature. For a given suction temperature, a higher-pressure ratio resulted in a higher exhaust temperature. Furthermore, the cooling effect of the wrap-around cooling pipeline is found to be more pronounced under high pressure ratio conditions, with a maximum temperature reduction of 189.5 °C.

Thermo-structural analysis and design for multi-functional membrane roofs of airport terminals

The utilization of large-span membrane structures in airport terminals has attracted considerable attention due to their excellent building aesthetics, reasonable structural behavior and multi-functional applications. Integrating structure and function is useful to improve thermal performance of such buildings. This study focuses on a scaled two-layer membrane roof in accordance with a newly-built aerogel-membrane airport roof and investigates the dynamic building thermal performance. The two-layer membrane roof is composed of an outer membrane layer as structural element, an air gap for ventilation and an inner membrane layer integrating aerogel mats. The effects of aerogel thickness, ventilation velocity and gap height are analyzed with multi-physics numerical tools. The structural behavior of the aerogel-membrane roof structure is examined in agreement with the building standards. The comparison between numerical and experimental results on solar irradiance is performed to demonstrate the reliability of numerical results under the typical environmental conditions. The thickness of the aerogel layer and the ventilation velocity are shown to have a significant effect while the air-gap height plays a minor role. A maximum temperature reduction of 4.7 °C demonstrates that using the proposed approach can improve building thermal performance. Moreover, temperature curves with small fluctuations indicate an efficient control of the indoor temperature. Therefore, the thermo-structural analysis method of the multi-functional membrane roofs can guarantee structural safety and facilitate building thermal performance control.

Flexible phase change materials based on hexagonal boron nitride (hBN) surface modification and styrene-butadiene-styrene (SBS)/low-density polyethylene (LDPE) crosslinking for battery thermal management applications

In battery thermal management (BTM), flexible phase change materials (FPCMs) emerge as highly promising substances, owing to their simple installment and low contact thermal resistance. However, FPCMs based on high thermal conductivity fillers and polymers always suffer from the enduring challenges of poor high-temperature resistance and poor filler-matrix compatibility. To solve these problems, a novel strategy is reported in this work, wherein FPCMs with excellent filler-matrix compatibility and satisfactory high-temperature resistance are synthesized by two steps: functionalizing the hexagonal boron nitride (hBN) surface and inducing the inter crosslinking between Styrene-Butadiene-Styrene(SBS) and Low-density polyethylene(LDPE). Vinyltrimethoxysilane (VTMS) molecules were introduced on the surface of raw hBN by hydroxylation and silanization surface modification to improve the compatibility of hBN with the matrix. Concluding from the results, the addition of 6.7 wt% LDPE doubled the high-temperature resistance of FPCMs, enabling them to maintain their structural integrity even at 200 °C for 1 h. The prepared FPCMs also exhibited higher thermal conductivity (increased by 20.5 %), low leakage rate (<0.6 wt% after 70 heating–cooling cycles), high enthalpy (122 J g−1), and strong adhesion (>0.1 MPa), etc. In terms of BTM performance, the FPCMs-based passive cooling BTM presents remarkable temperature control capabilities (maximum temperature reduction by 16.3 ℃) and uniform temperature performance (maximum temperature difference < 2.5 ℃). Collectively, this work will provide a promising approach for the fabrication of high-performance FPCMs in BTM and other thermal management applications for electronic devices.

Heat storage and release in binary paraffin-hexadecyl amine composites for solar greenhouses in cold climates

Traditional solar greenhouses in cold regions of China often suffer from poor thermal insulation and storage capacity, resulting in inefficient use of solar energy resources and reduced crop production efficiency. Therefore, it is crucial to explore methods to enhance the thermal conditions within these greenhouses. This paper proposes incorporating a “binary paraffin hexadecyl amine” phase change material into concrete, creating a novel composite material for use in a phase change thermal storage concrete slab. This approach can effectively address the previously mentioned issues. Two solar greenhouses were constructed to directly observe the material's impact on the thermal environment within a greenhouse. One greenhouse was equipped with the phase-change thermal storage slab, while the other served as a control greenhouse without the slab. Temperature field test was conducted on both greenhouses, and the obtained test data demonstrated the temperature regulation advantages of the phase-change greenhouses. Tomatoes were concurrently cultivated in both structures, and a temperature test was conducted to assess the phase-change heat-storage slab's influence on temperature regulation. The results indicate that, compared to similar studies, the phase-change heat-storage slab employed in this study demonstrates superior temperature regulation capabilities. It raises the average greenhouse temperature by 4.2 °C during winter, storing 8.85 × 104 kJ/m3 of heat per unit volume, which is 1.5 to 2.8 times higher than existing materials in the same category. In sunny conditions, the phase-change greenhouse exhibited a 4.9 °C reduction in maximum indoor temperature during the day and a 3.5 °C increase in minimum indoor temperature at night compared to the control greenhouse. This indicated that the phase-change heat storage slab acted as a heat buffer, effectively regulating the temperature inside the solar greenhouse. Tomatoes experienced a 26.6 % increase in effective accumulated temperature, resulting in maturation period occurring 13.04 % earlier compared to the control greenhouse.