Thermal Management Structures Research Articles

Design and multi-objective optimization of hairpin motor cooling system based on orthogonal design method and composite algorithm

The new thermal management structure of the motor is designed to ensure effective heat dissipation while maintaining low pressure loss, reduce the required power of the cooling pump. The dimensions of the new thermal management structure of the motor are optimized through the establishment of a multi-objective optimization platform. Computational Fluid Dynamics (CFD) simulations were conducted through single-factor analysis to compare and preliminarily determine the number of turns in the spiral channel. The key structural dimensions of the flow channel were adjusted using orthogonal design method for CFD simulations. The obtained complete orthogonal table was used as a dataset for comparing and analyzing the optimization of the Backpropagation (BP) neural network using the Genetic Algorithm (GA) and the Particle Swarm Optimization (PSO) algorithm. Results showed a higher fitting accuracy after optimization with the Particle Swarm Optimization algorithm. The Non-dominated Sorting Genetic Algorithm III (NAGA III) was employed for multi-objective optimization of the key flow channel dimensions. The optimal solution identified from the Pareto optimal solution set graph, which is the lowest point combining the highest stator temperature and maximum pressure in the flow channel, was verified through simulation to have a prediction accuracy of 99% for the comprehensive optimization algorithm. Furthermore, the simulation results of the cooling system obtained from multi-objective optimization were compared with the original cooling system, the comparison results show that the maximum pressure has decreased by 43.13%. Orthogonal design methods and composite algorithms are employed to replace traditional optimization methods for multi-objective optimization of motor cooling system in this study, offers a new perspective for the structural design of motor cooling systems.

A sustainable and robust Janus film Inspired by the bird’s nest structure for efficient year-round outdoor thermal management

Janus structures combining radiative cooling and heating have attracted considerable interest for providing thermal comfort in dynamic environments. However, most of the strategies ignore the weak interfacial bonding due to the differences in material properties of the cooling and heating sides, which ultimately results in a lack of durability. Herein, inspired by the bird’s nest structure, we demonstrated a dual-mode Janus film with bonded interfaces through a simple vacuum-assisted filtration and PDMS modification. The unique structure of the film ensures efficient thermal management including a sub-ambient temperature drop of ∼6.7 °C and a rise of ∼19.8 °C under direct sunlight irradiance. The cooling performance is activated by the synergistic enhancement with BaSO4 and BC porous networks, which exhibits high solar reflectivity (∼95.6 %) and MIR emissivity (∼95.2 %). The heating performance is derived from solar heating (∼71.6 °C at one sun irradiation) and Joule heating (∼88.6 °C at a low voltage of 2.5 V) as a complement, benefiting from the photothermal and electrothermal conversion of MXene. The cooling and heating can be easily obtained by flipping. In addition, the film maintains efficient cooling and heating even after being immersed in water and exposed to sunlight, thereby ensuring outdoor thermal management. Overall, this dual-mode Janus film shows great potential for regulating outdoor thermal comfort and alleviating the energy crisis.

Topology Optimization of Functionally Graded Structure for Thermal Management of Cooling Plate

The fast charge and discharge of a battery will significantly increase the overall temperature and thermal difference of the battery, which will further affect the working performance and safety of the battery. Therefore, a heat–fluid coupling topology optimization pipeline for developing radiation performance of the cooling plate is presented to ensure the thermal homogeneity of the battery in this paper. First, the Brinkman penalty model is utilized to construct the solid and fluid structures. Then, a local volume constraint is introduced to create the lattice structure to reduce the temperature difference of the cooling plate. Furthermore, a functionally graded lattice structure via a variable influence radius is presented to improve the radiation performance of the cooling plate when the thermal load is uneven. Numerical experiments are carried out to evaluate the performance of the presented methods on the optimization of the cooling plate, which indicates that the designed cooling plate by the proposed method improves the radiation performance when compared against a traditional straight channel and a SIMP-based optimal design.

Thermal conductivity of 3D-printed block-copolymer-inspired structures

This study primarily focuses on examining the impact that geometric structure has on thermal conductivity of multi-phase constructs in different 3D-printed poly(lactic acid), PLA, samples. The investigated structures are inspired by morphologies formed by diblock copolymers: lamellae, hexagonally packed cylinders, and gyroid. This research also investigates how volume percentage and material combination influence the thermal conductivity of these structures. The samples can be tailored to simulate various thermal management structures observed in practical applications, such as thermal interface materials in electronic devices. Thermal conductivity ratio is controlled using air, the least conductive material at 0.026 W/(m K), PLA at 0.136 W/(m K), and thermal paste at 5.11 W/(m K). Different models were tested against thermal conductivity measurements in order to capture the effect of material type (PLA-Air versus PLA-Thermal Paste), volume percentage, structure, and orientation. Simple, effective medium models were good predictions of thermal conductivity in lamellar structures, but it was necessary to develop models for conduction through cylindrical and gyroid structures. Finally, all results were normalized to find a universal model that is independent of structure and material. This approach provides a simple method to predict how to reduce or enhance transport properties and heat management capabilities of 3D printed objects.

PVA-assisted graphene aerogels composite phase change materials with anisotropic porous structure for thermal management

The rapid development of spacecraft thermal control systems necessitates high-performance phase change materials (PCMs) with low density, high thermal conductivity and high enthalpy. Graphene aerogels (GAs) prepared by unidirectional freezing are ideal candidates as thermal conductive networks for PCMs due to the anisotropic porous structures. However, constructing anisotropic thermal conductive composite PCMs with low graphene aerogel loading while employing environmentally friendly cross-linking agents remains challenging. To fulfill the research gap, this study explores the synthesis of poly(vinyl alcohol) (PVA)/graphene aerogels (PGAs) by hydrothermal reaction and conventional freeze-drying. Anisotropic PGAs with oriented porous structures were fabricated by unidirectional freezing. After annealing and impregnation with paraffin wax, composite PCMs with excellent shape stability were obtained. The prepared composite exhibits low density (0.82 g cm−3) and high enthalpy (165 J g−1). The combination of PVA and graphene enables the composite to achieve an ultralow graphene aerogel loading (0.85 wt%) while maintaining high thermal conductivity (1.37 W m−1 K−1), leading to a high specific thermal conductivity enhancement up to 477. This work sheds light on the potential of combing PVA and graphene to construct thermal conductive aerogels, intending to provide feasible means to develop high-performance PCMs for spacecraft thermal management.

Intercalation of V2O5 and Polypyrrole into a Graphene Oxide Layer: A Hybrid Multifunctional Photothermal Structure for Efficient Solar Evaporation, Water Purification, Disinfection, and Power Production.

Development of a hybrid multifunctional photothermal structure with multifunctional capabilities is deliberated as an effective approach for harvesting abundant solar energy for sustainable environmental applications. Achieving enhanced solar to thermal conversion efficiency utilizing a suitably designed, environmentally compatible thermal management structure however remains a significant challenge. Herein, we report the intercalation of V2O5 and polypyrrole into a graphene oxide layer to design a hybrid photothermal assembly (PPy-V2O5-GO) and its multifunctional proficiencies. The hybrid photothermal structure demonstrated synergistic photothermal conversion, buoyant porous structure sustaining water transmission, and efficient steam release. V2O5 and polypyrrole-intercalated optimized graphene oxide structure attained an evaporation rate of 1.9 kg m-2 h-1 with a conversion efficiency of 92% under 1 sun solar radiation. At maximum, the assembly's surface temperature hit 64 ± 2 °C, suggesting its suitability as a solar water purifier. Outdoor experiments suggest the evaporator assembly's capability to accumulate a total output of 15 kg m-2 over a single day. Cell viability investigations revealed strong antimicrobial properties of PPy-V2O5-GO against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria, eliminating nearly all under 1 sun, making it a potential candidate for photothermal therapy. Furthermore, when combined with a commercial thermoelectric module, the framework displayed exceptional photothermal conversion efficiency, hinting at its potential for electrical power generation. The integration of PPy-V2O5-GO with a Bi2Te3-based thermoelectric module significantly boosted the thermoelectric generator's performance, offering an enhanced power output of 2.8 mW and a high power density of 1.24 mW/cm2, making them suitable for off-grid or remote-area application. Overall, the PPy-V2O5-GO photothermal assembly's stability, lack of leaching, effectiveness in producing pure water from seawater, antimicrobial efficacies, and recyclability make it an excellent choice for sustainable water treatment and power generation.

Temperature field spatiotemporal modeling of lithium-ion battery pack configured sparse temperature sensors

Quickly predicting the temperature distribution of a battery pack equipped with sparse temperature sensors is vital in evaluating performance and designing structure. However, limitations of sparse temperature signals, large-scale stack, and complex spatiotemporal characteristics make existing models fail to accurately predict each cell's temperature in the ESS. This paper introduces a spatial-temporal model that quickly predicts the temperature field of the 40-string battery pack with a cell-level computational consumption using the collected sparse signals, where the prior knowledge of battery mechanisms and complex physical modeling are no longer required. The summarized sensor location selection principles ensure the model stays optimal. The predictive performances of the proposed model are discussed in relation to different operating conditions, temperature sensor numbers, and locations. The results show that the sensor-to-cell ratio can be reduced from 1/10 to 1/40 with different training-testing datasets by adhering to the proven principles of optimal sensor position selection. Given the special package structure, the proposed model remains highly effective and accurate in predicting the temperature field of battery packs with one temperature sensor, while the other three benchmarks have a terrible prediction. The proposed engineering-affinity model and ideas are of high practical significance in designing thermal management structures and developing health management strategies for battery systems.

Magnetically assembled flexible phase change composites with vertically aligned structures for thermal management and electromagnetic interference shielding

Phase change material (PCM) is promising in achieving zero-energy thermal management because of its prominent thermal storage capacity and steady phase-change temperature. However, low intrinsic thermal conductivity (TC), liquid leak, and solid rigidity are long-standing bottlenecks for heat-related applications. Here, we report an innovative dual-encapsulation strategy to develop multifunctional phase change composite (FMP) with vertically aligned NdFeB@Ag arrays and styrene-ethylene-propylene-styrene (SEPS) crosslinked network in paraffin (PA). The NdFeB@Ag arrays induced by magnetic-field driven procedure can offer the consecutive/oriented highways for efficient heat-transfer, and an electric/magnetic heterostructure for electromagnetic interference shielding efficiency (EMI SE). The flexible SEPS block copolymer not only ensures the high flexibility of PCM, but also combines with oriented NdFeB@Ag arrays for dual encapsulating PA. This multifunctional FMP can achieve high TC of 2.59 W m−1 K−1, attractive EMI SE of 35.42 dB, prominent enthalpy density of 120 J g−1, and impressive Joule heating performance, together with leakage-proof, dynamic assembly, and salient charging/discharging durability. Furthermore, the FMP-supported device is demonstrated for thermal energy harvesting and utilization. This dual-encapsulation design opens a new avenue for exploiting multifunctional PCMs for thermal management, anti-EM radiation, and low-grade exhaust heat utilization.

Advanced Design and Manufacturing Approaches for Structures with Enhanced Thermal Management Performance: A Review

AbstractAdvanced design methods and manufacturing techniques are crucial for developing thermal management structures, essential for the efficient operation of complex equipment. This study provides a thorough review of design methodologies and advanced manufacturing technologies for thermal management materials and structures. It identifies key challenges and critically evaluates the integration of innovative design principles, such as biomimicry and topology optimization, into thermal management solutions. The analysis delves into the evolution of design theories and preparation techniques, with a specific focus on modern needs and research directions, particularly highlighting components fabricated using additive manufacturing and their effectiveness in meeting advanced thermal management requirements. Current research focuses on designing structures tailored to various cooling methods, including air‐cooling, liquid‐cooling, heat exchanger cooling, and heat pipe cooling. These designs utilize phase change materials, electrocaloric cooling, and thermoelectric cooling materials to achieve optimal thermal management performance. Additionally, emerging innovations like solid‐liquid mixed heat transfer and the elastocaloric effect are garnering increased interest. Enhancing the design of thermal management structures through rigorous numerical simulations is critical for improving engineering applicability. However, overcoming challenges related to the commercialization and practical utilization of these advanced structures remains a pressing need.

Nano-engineered versatile Janus natural-skin with sandwich structure for wearable all-season personal thermal management

Thermal management wearables hold significant promise for various applications, such as bio-integrated electronics, multifunctional fabrics, thermoelectric devices, etc. Given the complex and volatile external environmental conditions they may encounter, thermal management wearables should possess versatile and comprehensive auxiliary functions to enable cutting-edge advanced applications. Herein, we present a multifunctional nano-engineered Janus-type natural-skin (SHRC-skin) offering dual-modes of solar heating and radiative cooling. Additionally, the SHRC-skin integrated functionalities like flammability resistance, electromagnetic interference (EMI) shielding, and physiological signal monitoring achieved through the integration of traditional spray techniques and a phase-conversion pathway on natural-skin as a substrate, SHRC-skin enabled all-season thermal management. The radiative cooling side of the SHRC-skin incorporates a CA/Mg11(HPO3)8(OH)6 composite coating with an irregular porous structure, while the solar heating side consists of multi-walled carbon nanotubes (MWCNT) with a rough structure. The radiative cooling layer exhibited a solar reflectance of ∼90.13 % and a mid-infrared emittance of ∼87.6 %, whereas the heating layer demonstrated a solar absorptance of ∼89 %. These attributes translated to excellent thermal management performance in outdoor-tests. Furthermore, SHRC-skin offered extensive additional functionalities, including exceptional asymmetric wetting, flame retardancy, electrical conductivity, Joule heating, electromagnetic shielding, and physiological signal monitoring. This versatility significantly enhances SHRC-skin's adaptability to complex and diverse environments. In summary, the multifunctional SHRC-skin seamlessly transitions between cooling and heating modes without additional energy input. This innovation holds great promise for all-season wearable thermal management, environmentally friendly travel, and energy-efficient building furnishings, and opens new possibilities for the development of wearable materials across various scenarios.

Eco-friendly wearable textiles: Asymmetric structures for EMI shielding, thermal management, and fire safety

This work focuses on developing multifunctional wearable fabrics, specifically targeting the challenge of flammability in this context. An eco-friendly, asymmetrically structured nylon/cotton blend fabric is prepared through the surface modification of phytic acid-induced polyaniline, the application of silver nanowires (AgNWs) and MXene on both sides and encapsulated by polydimethylsiloxane (PDMS). The AgNWs coating suppresses thermal radiation from the human body to achieve radiative heating, while the MXene coating enhances solar heating, ensuring thermal comfort in cold conditions. The treated fabric also exhibits electrical heating for heat compensation in the absence of sunlight, remarkable EMI shielding performance (55.6 dB) is also achieved. Enhanced fire safety is demonstrated as the treated fabric extinguishes when exposed to flame, reducing heat release by 45.9 % relative to the control nylon/cotton blend fabric (CO/NY). Additionally, the treated fabric exhibits significant antibacterial properties against Gram-negative E. coli and Gram-positive S. aureus, along with a notable water contact angle (WCA) of 130.2°. This work provides a promising method for the development of eco-friendly wearable smart fabrics with well-balanced desirable properties.

Radiative cooling cellulose-based fabric with hierarchical structure for outdoor personal thermal management

Personal thermal management is significant in alleviating the heat stress of pedestrians and outdoor workers. There is a need to develop a wearable fabric to further improve the comfort and cooling efficiency of outdoor personnel. Herein, we report an eco-friendly hierarchical cellulose-based fabric with excellent passive daytime radiative cooling (PDRC) performance. The obtained radiative cooling cellulose-based fabric (RCCF) possesses high solar reflectivity of 90.2 % in the solar spectrum (0.3–2.5 μm) and high emissivity of 98.1 % in the atmospheric window (8.0–13.0 μm). Under a solar radiation of 728 W·m−2, the simulated skin temperature covered with RCCF was 6.5 °C lower than that of original cotton. Moreover, the RCCF provides desirable wearability performance, and can be further applied in large-scale production due to simple and low-cost coating processes. The excellent cooling performance of this hierarchical cellulose-based fabric is promising to bring new insights into the design of next-generation functional textiles.

Recovery of engine waste heat in low temperature environment of plug-in hybrid electric vehicle

The performance and life of electric vehicle power batteries will be reduced at low temperatures, and the lower temperature in the electric vehicle will also affect the comfort of drivers and passengers. Taking into account the winter temperatures and the unique drive structure of the plug-in hybrid electric vehicle, a specially designed driving mode for low-temperature environment is implemented. Based on this drive mode, a plug-in hybrid electric vehicle (PHEV) integrated thermal management structure is proposed to heat the battery and the passenger compartment, thereby improving energy efficiency. A mathematical model is used to establish the entire vehicle thermal management system, which is then experimentally validated. Under the NEDC (New European Driving Cycle) at ambient temperatures of −5°C, −10°C, −15°C, and −20°C, the calculation results of engine waste heat utilization and PTC (Positive Temperature Coefficient) heating are compared and analyzed. The results show that the average heating rate of the thermal management system proposed in this study is 23% faster than that of PTC heating at low temperature. The SOC decreases to 63.43% when engine waste heat utilization is adopted. When PTC heating is used, the SOC decreases to 49.18%. However, the advantage of the faster rate of engine waste heat compared to PTC heating becomes less pronounced as the ambient temperature decreases.

Triply Periodic Minimal Surface Structures: Design, Fabrication, 3D Printing Techniques, State‐of‐the‐Art Studies, and Prospective Thermal Applications for Efficient Energy Utilization

This review highlights the latest developments of triply periodic minimal surface (TPMS) structures with the aim of the system's energy utilization. TPMS structures have gained widespread recognition due to their significant heat transfer (e.g., enhanced surface area) and diverse mechanical properties (e.g., structural stability), making them highly valuable in numerous thermal applications. A comprehensive survey of the design approaches, software tools, commercial materials, and 3D printing techniques of TPMS‐based structures is provided. Research gaps and future perspectives for the commercialization of TMPS structures are identified. Moreover, the potential applications of TPMS‐based structures for heat transfer augmentation and thermal management are discussed. TPMS‐based structures are promising topologies for heat exchangers on account of their intrinsically outstanding specific surface area. In this context, TPMS‐based structures have received considerable attention for various applications, including heat exchangers, latent heat storage, hydrogen storage, battery cooling/thermal management, and membrane distillation. Besides, distinct potential applications of TPMS‐based structures are proposed for heat transfer intensification and thermal management of photovoltaic/thermal collectors and fuel cells. Meanwhile, new proposals for using TPMS‐based structures for different sorption‐based applications, notably adsorption cooling/desalination systems, adsorption atmospheric water harvesting, thermochemical energy storage, and desiccant air conditioning, are nominated for forward‐looking perspectives.

Research on performance test and evaluation of thermal management system of power battery module under harsh conditions

Under harsh conditions, the battery module (BM) used for Ev’s power system has issues of local overheating, continuous high temperature, and spontaneous combustion causing thermal accidents. This problem is directly related to the safety of life and property of drivers and passengers. What’s more, it also seriously restricts the high-quality development and promotion of Evs. To solve the limitations and drawbacks of the BM. this paper designs the thermal management structure with TiO2 nanofluids closed loop pulsating heat pipe (TiO2-CLPHP) as the key component and constructs the thermal management system with TiO2-CLPHP (TiO2-CLPHP TMS). On the basis, the temperature optimal thermal management strategy (TOS) and energy consumption optimal thermal management strategy (ECOS) is proposed. To investigate the performance response of TiO2-CLPHP TMS, the performance test of TiO2-CLPHP TMS is carried out. The results show that in terms of thermal management performance, the TiO2-CLPHP TMS with TOS and ECOS (TOS-TiO2-CLPHP TMS, ECOS-TiO2-CLPHP TMS) can effectively suppress the highest temperature, temperature rise and improve temperature uniformity of the PM. Of these, the minimum improvement rates of TOS-TiO2-CLPHP TMS can reach 29.41%, 78.37%, 65.88%, 58.82%, and 64.95%. The minimum improvement rates of ECOS-TiO2-CLPHP TMS can reach 27.24%, 72.65%, 64.71%, 55.88%, and 68.04%, respectively. In terms of the thermal management economy, compared with TOS-TiO2-CLPHP TMS, ECOS-TiO2-CLPHP TMS has lower energy consumption. The efficiency values of the ECOS-TiO2-CLPHP TMS are not less than 87.72%. It can be concluded that the proposed TiO2-CLPHP TMS has excellent thermal management performance. The ECOS-TiO2-CLPHP TMS can maximize the dual requirements of the thermal management performance and thermal management economy. This study innovatively proposed a thermal management method for nanofluids PHP used in BM. Compared with previous studies, the proposed TiO2-CLPHP TMS reduced the temperature difference from the traditional 5.00 °C to less than 3.40 °C, greatly improving the temperature uniformity of the BM. The completion of this research provides a new idea of battery thermal management based on metal oxide nanofluids PHP, and the constructed performance evaluation method provides a referral scheme for the performance test and evaluation of thermal management technology.

Thermoregulatory elasticity braided fibers designed with core–sheath structure for wearable personal thermal management

The thermoregulatory elasticity fiber was designed and fabricated using coaxial wet spinning, which combines solar-thermal and phase-change energy. This exploration presents a strategy to develop smart fabrics for personal thermal management.

Chemical Resistant Yarn with Hierarchical Core–Shell Structure for Safety Monitoring and Tunable Thermal Management in High-Risk Environments

Chemical resistant textiles are vital for safeguarding humans against chemical hazards in various settings, such as industrial production, chemical accidents, laboratory activities, and road transportation. However, the ideal integration of chemical resistance, thermal and moisture management, and wearer condition monitoring in conventional chemically protective textiles remains challenging. Herein, the design, manufacturing, and use of stretchable hierarchical core–shell yarns (HCSYs) for integrated chemical resistance, moisture regulation, and smart sensing textiles are demonstrated. These yarns contain helically elastic spandex, wrapped silver-plated nylon, and surface-structured polytetrafluoroethylene (PTFE) yarns and are designed and manufactured based on a scalable fabrication process. In addition to their ideal chemical resistance performance, HCSYs can function as multifunctional stretchable electronics for real-time human motion monitoring and as the basic element of intelligent textiles. Furthermore, a desirable dynamic thermoregulation function is achieved by exploiting the fabric structure with stretching modulation. Our HCSYs may provide prospective opportunities for the future development of smart protective textiles with high durability, flexibility, and scalability.

Thermal performance analysis and optimization of heat pipe-assisted hybrid fin structure for lithium battery thermal management for extreme thermal conditions

The current study proposed a heat pipe (HP)-assisted hybrid fin (HF) for inter-cell cooling in a battery thermal management system (BTMS). Its thermal performance was comprehensively investigated under extreme thermal conditions of up to 50 W along with critical variables. A numerical model for the proposed HF-BTMS was developed using the finite difference method and integrated with a performance prediction model based on an artificial neural network. After successfully validating with experimental results, the developed numerical model was intensely used for module-level thermal analysis and multivariate optimization. The proposed HF-BTMS exhibited a better thermal performance, which was experimentally verified by the reduction in the maximum temperature and deviation by 5.4 and 3.8 °C, respectively, than the BTMS with conventional plain fin (PF). The multivariate optimization indicated that the optimized performances of the HF-BTMS were all within the desired temperature ranges. The condensation lengths are known to be most influential rather than other variables related to coolant operating conditions. Finally, under the most thermally harsh condition, compared to PF-BTMS, the HF-BTMS was found out to dramatically reduce the maximum temperature and temperature deviation of the BTMS by over 17.95 °C and 16.37 °C, successfully maintaining within the safety range.

Flexible and Form-Stable Phase Change Composites Enabled by Pinecone-like Structure for Efficient Thermal Management

Flexible and Form-Stable Phase Change Composites Enabled by Pinecone-like Structure for Efficient Thermal Management

Efficient purification of metal-organic framework and its trigger strategy in battery thermal management system

Metal-organic framework (MOF) MIL-101(Cr) is a sorbent that can adsorb large amounts of water, but its performance is compromised by low thermal conductivity and unstable desorption temperature. In addition, the high cost restricts its application in thermal management. We propose a novel purification method, which reduces the cost of MIL-101(Cr) by 91%. Then, based on MIL-101(Cr) and micro heat pipe array (MHPA), we design an innovative thermal management structure with great performance, MHPA@MIL-101(Cr). To cope with extreme conditions, a trigger strategy based on active dehumidification and air-cooling technologies is used to improve the temperature and temperature uniformity of cells, and the effect of their trigger time on the desorption temperature of MIL-101(Cr) is studied. In a normal condition (25 °C), the zero-energy-consumption structure controls the maximum temperature (Tmax) of the battery module below 35.99 °C at 2C rate (112A). What is more, the trigger strategy improves the temperature characteristics in an extreme condition (35 °C). As a result, the Tmax is controlled at 38.8 °C when the battery module is 2C (112A) discharged, a temperature rise of only 3.8 °C.