To enhance capillary and thermal performance in flat grooved heat pipes (FGHP) for electronics cooling, a composite wick combining electrodeposited copper forest with rectangular grooves (CF-FGHP) is proposed. Capillary rise and heat transfer experiments verified its superiority. Visualization experiments revealed the copper forest enhances nucleation and accelerates internal circulation during heating. Effects of electrodeposition area and time on temperature uniformity and heat transfer limit were studied. Results show CF-FGHP achieved a capillary performance parameter K/reff of 1.96 mu m. During startup, it stabilized 66 s faster with a 5.9 degrees C lower evaporator temperature than FGHP. CF-FGHP#2 (electrodeposited area:25.0 x 37.5 mm2) achieved a total thermal resistance of 0.12 degrees C/W at 50 W, which is 63 % lower than the minimum total thermal resistance of FGHP. Optimizing electrodeposition time for CF-FGHP#2 produced CF-FGHP#2-250 (electrodeposited time:250 s), achieved a 70 W heat transfer limit and a total thermal resistance of 0.11 degrees C/W at 65 W, representing a 66 % reduction in the minimum thermal resistance compared to FGHP, along with a 27.3 degrees C decrease in the evaporator temperature at 40W. This work provides new insights for dynamic thermal management of electronic devices.

Existing descriptions of positive temperature coefficient (PTC) systems are largely case-specific and offer limited guidance for understanding system-level dynamic thermal behavior. To address this limitation, a unified, dimensionless, frequency-domain framework is established to characterize the dynamic thermal response of PTC systems. Within this framework, a gated interpretation is introduced to represent the nonlinear coupling among system temperature fluctuations, material properties, structural parameters, and environmental conditions, and is validated against multiple experimental cases, showing deviations within +/- 8%. Quantitative guidelines for material development are then derived. Specifically, increasing the resistance temperature coefficient reduces the static gain in a nonlinear manner with diminishing returns; reducing thermal conductivity narrows the midfrequency response window and shifts it toward lower frequencies, thereby enhancing suppression of low- and mid-frequency disturbances; and increasing the latent heat of embedded PCM, if present, further suppresses temperature fluctuations within an effective frequency bandwidth exhibiting a Gaussian-shaped profile, governed by the latent heat magnitude and phase-change temperature span. These findings provide a theoretical basis for scenario-specific material development and structural design, emphasizing tailoring material properties to operating conditions.

Pressure-swirl nozzles are critical components in industrial processes such as chemical reactions, humidification, and cooling. The overlap regions formed by multiple nozzles considerably affect droplet size and spatial distribution, thereby influencing heat and mass transfer performance. However, these interaction mechanisms remain insufficiently elucidated. This study presents a systematic experimental investigation comparing the spray characteristics of a single and paired adjacent pressure-swirl nozzles, focusing on the effects of the overlap region on droplet dynamics. The results show that within the overlapping spray region of double nozzles, the turbulent kinetic energy (TKE) varies gently with its peak shifting outward, yielding a more uniform turbulence distribution with attenuated velocity fluctuations in the overlap region. The higher droplet density in the overlap region promotes collisions between droplets with large size differences. The Weber number of these collisions exceeds the critical threshold, causing droplet breakup and generating fine droplets (5–10 μm). Consequently, under the same pressure differential, the integral Sauter mean diameter (ID32) is reduced by 19.5%, peak droplet size in the overlap region by 20.9%, and the whole-plane ID32 by 17.7%. The collision contribution analysis reveals that the dominant breakup pathway shifts from large-droplet collisions (>20 μm) to medium-droplet interactions (5–20 μm) under double-nozzle conditions. Increasing the pressure differential further enhances atomization quality; the decrease in the ID32 value of the double-nozzle spray relative to the single‑nozzle case increases from 9.5% at 0.35 MPa to 20.0% at 1.05 MPa. These findings provide crucial insights and theoretical guidance for designing efficient multi-nozzle spray systems.

This study addresses the inherent structural redundancy and wiring complexity of conventional temperature control systems by proposing an integrated temperature control and measurement scheme based on polymer positive temperature coefficient (PTC) materials. The key contribution is the pioneering development of a quantitative model for assessing the temperature measurement accuracy of PTC materials for the first time, which enables systematic error tracing and quantitative evaluation of measurement performance. By constructing a comprehensive accuracy model incorporating temperature resolution and calibration error, we clarify the temperature dependence of accuracy and identify dominant error sources. Experimental results demonstrate that within the strong PTC effect region, this method can achieve a high-precision temperature measurement error within ±0.1 ℃. Model analysis further reveals that a temperature coefficient of resistance (TCR) of at least 10% ℃⁻¹ within this region is essential for such high precision. In addition, the system demonstrates excellent stability and robustness under varying temperature and operating voltages. This study provides important exploration and methodological support for advancing PTC materials from single-function temperature control components to integrated "measurement–control" intelligent units, promoting the development of highly integrated and lightweight thermal management systems for specific temperature-sensitive applications.

Low-frequency temperature noise disturbs the detection accuracy of space-borne gravitational wave detectors. The phase compensation scheme can effectively suppress low-frequency temperature noise but requires improvement in its suppression performance for even lower frequency bands. Accordingly, this paper proposes a feedback correction method based on the existing phase compensation method, which adjusts the amplitude and phase of the compensating heat flux. A phase compensation and feedback correction model is established. Multiple sets of periodic heat fluxes are input to investigate the temperature noise suppression effect. The results indicate that within the frequency range of 0.1 mHz to 2 mHz, the temperature noise suppression effect can be further enhanced by the feedback correction method. At 0.1 mHz, temperature noise is reduced by 99.33 % compared to phase compensation without feedback correction after five feedback corrections, and by 99.63 % compared to no phase compensation. For other frequencies, more than 90 % and 99.5 % reduction is achieved relative to the same two cases, respectively, often in five or fewer correction steps. Further feedback iterations allow minor suppression improvements, with the extent being negligible. Feedback correction acts independently on each frequency component of the compensating heat flux when input heat flux consists multiple frequencies.

To address the issues that composite phase change materials (CPCMs) are confined to intermittent heat dissipation scenarios and suffer from reduced heat transfer efficiency (even acting as an additional thermal resistance) after complete phase change, this study proposes a heat dissipation enhancement strategy based on shape memory CPCMs (CPCM-SMs). Triggered by the phase-transition temperature, CPCM-SMs autonomously transform from a covered state to a finned state, dynamically expanding the heat-transfer area to enhance heat dissipation and shorten cooling time. Furthermore, driving alternating cycles between the fin body and fin root sections enables long-term efficient and stable temperature control. Experimental results show that the CPCM-SM heat dissipation structure outperforms both the no-CPCM and conventional CPCM structures in temperature regulation, though its efficacy depends on operating conditions, thermal conductivity, and layout. Higher airflow and heating power increase its advantage over the conventional CPCM structure, but reduce it versus the noCPCM structure. Improved thermal conductivity leads to better temperature regulation with the CPCM-SM structure. During the cooling phase after the heat source is turned off, the CPCM-SM structure significantly reduces cooling time compared to the conventional CPCM structure. Furthermore, the alternating-cycle strategy further enhances temperature regulation across wider conditions, notably under natural cooling, where it reduces the dynamic equilibrium temperature by 18 degrees C and thermal resistance by 22% at a heating power of 3.09 W. This approach combines enhanced dissipation with faster cooldown, providing a viable continuous thermalmanagement solution for electronics.

The emergence of wafer scale chips with tens of kilowatts power consumption creates a critical thermal management challenge where conventional single phase liquid cooling faces inherent energy efficiency limitations due to its reliance on sensible heat transfer. While spray cooling can leverage latent heat, existing studies have been confined to small area, low power conditions, leaving the fundamental understanding of scaling effects on two phase heat transfer largely unexplored. Based on deionized water, single nozzle type, and short-term tests, this study investigates the coupled mechanisms of pressure and flow rate on spray cooling heat transfer across a 500 cm2 heated area under negative pressure conditions. Experimental results demonstrate that evaporator pressure governs the wall temperature primarily through the saturation temperature, while the flow rate influences the onset of critical heat flux mainly by replenishing the liquid film. Quantifying the interaction between pressure and flow rate requires additional experimental data and further dimensionless analysis. At 16 kW total heat load, the system achieves a steady state average chip temperature of 65.7 °C. The vapor fraction reaches 47.2% at a flow rate of 0.82 L/min, demonstrating that high vaporization efficiency can be sustained at ten kilowatt power scales. The system attains a power usage effectiveness of 1.03, demonstrating a low cooling energy overhead for phase change thermal management. These findings establish negative pressure spray cooling as a scalable two phase heat transfer paradigm, providing fundamental insights into energy efficiency in large area thermal management systems for next generation high performance computing applications.

Due to the unique high thermal resistance bottom structure of dual-chamber cartridges, the heat input during primary drying shifts from the bottom conduction-dominated mode in traditional vials to a lateral heat transfer-dominated mode. Current research in this area remains predominantly experimental, highlighting the need for in-depth mechanistic analysis of heat and mass transfer to inform process optimization. To address this, this study develops a heat and mass transfer model for dual-chamber cartridge by modifying the boundary conditions that describe the external heat transfer pathways. This model is employed to systematically investigate the influence of key process parameters—shelf temperature, drying chamber pressure, solution fill height, and the gap distance between the shell and cartridge—on the primary drying time, maximum product bottom temperature, and the contribution proportion of different heat transfer pathways. Results demonstrate that: drying chamber pressure exhibits a counter-intuitive influence: moderately increasing the pressure shortens the drying time by enhancing lateral rarefied gas conduction, which contrary to the conventional guideline. Furthermore, the shell-cartridge gap, a unique structural parameter of this system, plays a critical role—reducing it greatly decreases lateral thermal resistance and serves as a key means to optimize drying efficiency. The model and findings provide an important theoretical foundation for understanding and optimizing the freeze-drying process for dual-chamber cartridges.

Personal wearable heating devices are energy-efficient and cost-effective for thermal comfort in cold stress but face challenges in balancing flexibility, safety, and energy efficiency. Flexible positive temperature coefficient (PTC) materials exhibit self-adaptive heating capacity, enabling safe, energy-efficient and lightweight solutions. Thus, this paper proposed a human body temperature prediction model integrating self-adaptive PTC heating model with human bioheat model, to analyze localized PTC heating effects on transient thermal response in cold stress. Experiment validation showed good accuracy with only 0.7 % deviation for PTC model and maximal 0.6 degrees C deviation for human bioheat model. Self-adaptive PTC heating outperforms constant-power heating in faster thermal response, superior environmental adaptability, enhanced temperature stability, and extended thermal comfort duration, since the nonlinear PTC effect enables rapid heating at low temperature and overheat prevention above Curie temperature. PTC heating extended thermal comfort duration by 1.5-6 hours in different northern Chinese cities. For severe cold stress, optimal placement of PTC heating combined with high clothing insulation is recommended to balance thermal protection and work mobility. Flexible PTC material based selfadaptive heating offers a potential solution for wearable personal thermal management with low energy consumption.

The improvement of electronic integration increases the heat flux and limits the heat dissipation space,so the compact and power-free heat dissipation mode is very important for the efficient thermal management of miniaturized electronic equipment. In this paper, a micro self-driven manifold microchannel heat sink with dual liquid lines is proposed to enhance the flow and heat transfer performance. Combining the strong capillary force of the microchannel, the passive heat dissipation of the heat pipe and the principle of the manifold configuration, a self-driven manifold microchannel heat sink with an overall size of 24 mm & times; 48 mm & times; 0.8 mm is fabricated. A 5 mm & times; 5 mm heater is adopted as the heat source. Using deionized water as the working fluid, in order to investigate the influence of filling ratio, the start-up operation ability and flow and heat transfer performance of self-driven manifold microchannel heat sink with different filling ratios are analyzed by adjusting the input power and combining visualization. The experimental results show that the self-driven manifold microchannel heat sink achieves rapid start-up at 4 W input power at 60% optimal filling ratio, ensuring timely supply of working fluid and efficient phase change heat transfer to maintain stable operation of the system. At the filling ratio of 60%, the temperature rise of the self-driven manifold microchannel heat sink can be reduced by 57.43 degrees C when the input power is 8 W compared with the unfilled working medium. The heat flux of 32 W/cm2 can be achieved within 120 degrees C, and the highest thermal conductivity of 932.92 W/(m & sdot;K) is achieved, showing the excellent heat dissipation performance of the structure in a small space.

ABSTRACT Conventional temperature‐control systems generally rely on separate heaters, temperature sensors, and controllers, resulting in complex wiring and structural redundancy. This study proposes a proof‐of‐concept strategy in which a single polymer positive temperature coefficient (PTC) composite simultaneously performs self‐regulating heating and resistance‐based temperature measurement. The composite consists of an olefin block copolymer/stearic acid matrix filled with carbon black and expanded graphite, forming a three‐dimensional point–plane hybrid conductive morphology. The material exhibits a PTC transition temperature of approximately 60°C, a maximum temperature coefficient of resistance of 103% °C −1 , and an overall PTC intensity of 6.2. Under an applied voltage of 10 V, increasing the ambient temperature from 15°C to 30°C resulted in a peak‐to‐peak steady‐state temperature variation of only 2.2°C. At an ambient temperature of 25°C, the composite reached steady‐state temperatures of approximately 62°C–64°C over an operating voltage range of 6–12 V, with a peak‐to‐peak variation of 2.3°C. An error‐propagation model was further established to quantify the temperature‐estimation performance and identify the temperature coefficient of resistance as the dominant factor governing temperature resolution. Within the tested strong‐PTC window of 60°C–65°C, the temperature inferred from the calibrated resistance–temperature relationship showed a maximum deviation of approximately ±0.1°C relative to the PT100 reference under the investigated conditions. These results demonstrate the feasibility of integrating self‐regulating heating and temperature sensing into a single lightweight PTC composite and provide a methodological basis for highly integrated thermal‐management devices.

Thermoelectric p- and n-type legs are commonly paired by matching their Seebeck magnitudes, although a cooler responds to heat transported through its complete electrical and thermal network. We decompose the leg coefficients into differential thermopower α=S_p-S_n and common thermopower M=(S_p+S_n)/2. In a connected steady-state scalar thermoelectric network, a temperature-independent co-shift applied to every electrically active segment is an exact terminal null. A temperature-dependent perturbation of the legs relative to fixed leads is instead physical. At fixed current and shared isothermal endpoints, its first-order cold-port response is the action of Γ_m=T dm/dT on the difference between the p- and n-branch oriented collection measures. We prove that every continuous Γ_m cancels if and only if these measures are equal. In the constant-property, linear-common-mode limit, matching R_i/K_i^ leg is sufficient and does not require identical legs. One- and two-dimensional calculations confirm the analytic reductions within their stated domains. For split thermal pads, the analysis gives the exact array law ΔQ_c,Σ=∑_j C_jI_jΔT_c,j and, for series elements with isothermal hot pairs, IΔV_Σ=-ΔQ_c,Σ. A representative seven-pair model gives corresponding increments of 7.87 mW and -2.80 mV. Branch transfer and endpoint topology therefore provide distinct material-pairing and device-test criteria for common-mode Thomson heat.

Thermal management constraints have emerged as a critical challenge that impedes the sustained advancement of high-power electronic devices. This study pioneers the adoption of an induction heating platform, successfully overcoming the extreme heat flux testing bottleneck encountered with traditional Joule heating methods due to limitations in contact thermal resistance and heater rod power density. By integrating a self-developed high-flow-rate low-pressure atomizing nozzle, SDS surfactant, and a bionic leaf vein structure-reinforced surface with the induction heating platform, a significant leap in spray cooling heat flux density has been achieved. Experimental results indicate that this integrated innovative approach attains a spray cooling heat flux density of 1385 W/cm2 under high subcooling conditions (15 degrees C), while maintaining 881 W/cm2 even under low subcooling conditions (85 degrees C) where sensible heat contribution is minimal. This represents the highest value reported to date in open literature for spray cooling experiments and demonstrates the synergistic enhancement effect of the integrated system across a wide range of operating conditions. This research not only verifies the disruptive potential of induction heating technology in extreme heat flux thermal management studies but also provides novel academic insights and technical pathways for surpassing existing heat dissipation limits.

The Queqiao-2 satellite is a crucial part of the fourth Lunar Exploration Program mission.Compared to the Chang'e 4 Queqiao satellite,the Queqiao-2 satellite orbit changes from a Halo orbit at the Earth-Moon Lagrange L2 point to a circumlunar large elliptical orbit,with large changes in both relay communication and science load equipment.In this paper,the variation of solar heat flow and lunar infrared in a circumlunar large elliptical orbit with orbit is analyzed,which provides a basis for the design of the thermal control system of the Queqiao-2 satellite.In order to meet the temperature control requirements of the Queqiao-2 satellite in multi-mission mode and orbital attitude constraints,the thermal control system adopts a design scheme with adjustable heat dissipation capability based on loop heat pipe technology,while the design carries a positive temperature coefficient(PTC)self-controlled temperature heater,which is successfully applied in orbit.After Queqiao-2 was launched into orbit,the level of equipment temperature control during each flight phase was good.The first human lunar dorsal sample relay communications mission was substantially ensured by controlling the temperature of high-power relay loads,such as the Queqiao-2 X-band solid state amplifier,between 22 ℃ and 28 ℃ during the Chang'e 6 mission.The design method in this paper can provide a reference for the design of the highly adaptable thermal control system of a deep space exploration mission.

The embedded manifold Tesla-pattern microchannel heat sink is the key technology for AI chip cooling, requiring high thermal performance with lower power consumption. In this study, multi-objective optimization was employed to enhance the heat transfer and flow performance of the complex Tesla-pattern microchannel structure. The elliptical basis function neural network was utilized to predict the relationship between design parameters and response parameters. The Pareto front was obtained by using non-dominated sorting genetic algorithm-II. K-means clustering was introduced to divide the Pareto front into four partitions, and four cluster centers were obtained for the variable flow analysis. The analysis demonstrates that the longitudinal space and bending diameter have significant influence on the flow and heat transfer performance, and increasing them can effectively reduce the pump power but increase the thermal resistance. Under the same mass flux and a larger longitudinal space, regulating the transverse length and bending diameter can reduce the temperature difference on the chip surface. Cluster center B and C can better coordinate the relationship between pump power and heat dissipation capacity under variable mass flux conditions. The results indicate that the thermal resistance can be controlled within the range of 0.21 K/W to 0.44 K/W, while the pump power ranges from 0.032 W to 0.57 W at a heat flux of 250 W/cm2. After optimization, for the same pump power or equivalent thermal resistance, thermal resistance and pump power can be reduced by 5.2 % and 23 %, respectively. This work provides data support for the design parameters of the microchannel heat sink for the stable operation of AI chips under different demands.

Evaporative cooling is a widely applied cooling and humidification method. This study designed and constructed a direct spray tower based on pressure swirl nozzles, which generate sprays with a particle size range of 36-44 mu m to enhance water evaporation. The experimental parameters included water flow rate, inlet air temperature, inlet air humidity and air velocity. The effect of the operating conditions on spray tower performance parameters, including outlet air temperature, humidity, humidification capacity, humidification efficiency, saturation efficiency and energy efficiency ratios was comprehensively investigated experimentally. The results show that the humidification efficiency depends on both the spray pattern and the water flow rate, reaching a maximum value of 55 %. Reducing inlet humidity from 47 % to 12 % enhances humidification capacity by 53.2 %. Cooling energy efficiency ratio and humidification energy efficiency ratio increase in inlet air temperature and decrease in air velocity and inlet air humidity. Finally, Correlation equations proposed based on experimental data predict outlet temperature and saturation efficiency within +10 % and +15 % errors for 98.9 % and 96.7 % of data, respectively. It provides a reference for the design of spray towers.

Grooved bending heat pipe may operate at small inclination angle caused by practical installation errors. Previous researches mainly focused on large inclination angles of straight heat pipes, but fewer experiments were conducted at small inclination angle of bending heat pipe where liquid accumulation and gravity effect on liquid-vapor transport varies along the pipe. This paper experimentally studied the effect of small inclination angle (f3 degrees) on heat transfer of aluminum-ammonia Omega- grooved bending heat pipe with total length of 650 mm, vapor chamber diameter of 4 mm and grooved wick diameter of 1.24 mm. The results showed that small inclination angle significantly affect the heat transfer performance of bending heat pipe with heat transfer limit changed by 9 times from 20 W to 180 W and thermal resistance changed by 8 times from 0.04 K/W to 0.32 K/W. Effect of negative and positive angles in bending heat pipe is complex than that in straight heat pipe. Positive condensation end inclination enhances heat transfer due to gravity-driven liquid reflux. Negative condensation end inclination inhibits heat transfer due to anti-gravity reflux and liquid accumulation suppressing gas condensation. Positive evaporation end inclination weakens heat transfer due to anti-gravity reflux. Negative evaporation end inclination also weakens heat transfer due to thick liquid film, increasing thermal resistance and potentially blocking vapor channels. Attributed to coupling effect of liquid accumulation at bending section and capillary force dominant at tiny incline, maximum heat transfer limit of 180 W is achieved at both end inclination of-0.5 degrees.

A Tesla-patterned microchannel is proposed to enhance the heat transfer capacity of the embedded manifold microchannel by enhancing turbulence and suppressing vapor-liquid reflux. Experiments were conducted to compare and analyze the heat transfer and flow features of Tesla-patterned microchannel,pin-fin microchannel and rectangular microchannel heat sink under varying operating conditions. The results indicate that the convective heat transfer coefficient increased by 55.3 % to 88.3 %, and thermal resistance decreased by 22 % to 32.3 %, and temperature rise of chip surface decreased by about 20 degrees C compared with the other two microchannels. At a flow rate of 5 mL/s and using HFE7100 as the working fluid, the Tesla-patterned microchannel heat sink can achieve a heat flux of up to 1000 W/cm2, with an average temperature around 100 degrees C. In comparison to the other two microchannel heat sinks, Tesla-patterned microchannel heat sink can dissipate an additional 150 W/cm2 of heat flux and reach the two-phase stage, which indicates that it can operate stably with single-phase heat transfer at the higher heat flux, and the relationship between heat flux and temperature exhibits distinct linearity even in the two-phase stage. The enhanced heat transfer of the embedded manifold Teslapatterned microchannel is attributed to its curved structure, which induces the working liquid to impact the wall surface multiple times, thereby disrupting the boundary layer and suppressing the reflux of the working liquid.

Phase change materials (PCM) offer significant advantages in battery thermal management (BTM) due to high energy storage, chemical stability, and zero-energy consumption. However, conventional PCM struggles to meet demands as power batteries increase in capacity, structural complexity, and integration. This paper analyzes BTM's functional requirements for PCM to enhance power battery performance under complex conditions, focusing on exploring the application potential of flexible multifunctional composite PCM (FMCPCM). By reviewing the implementation strategies and mechanisms for PCM flexibility and multifunctionality, and integrating the latest application cases of FMCPCM in BTM, this study proposes innovative material designs to optimize thermal management in advanced energy storage. Polymer-based and porous scaffold-based FMCPCMs show superior BTM applicability due to superior encapsulation, thermal stability, and flexibility. Through functional filler addition, chemical modification, and surface coating, FMCPCMs can achieve multifunctionality, effectively alleviating heat accumulation in batteries, prolonging temperature reduction time, preheating batteries, mitigating vibration hazards, and enhancing operational safety. In current BTM applications, FMCPCM has primarily demonstrated efficacy in flame-retardant, photothermal, and electrothermal conversion functions, while other potential applications remain underexplored. However, driven by the exponential growth of the global electric vehicle industry and the escalating demand for advanced thermal management solutions, FMCPCM exhibits substantial commercial potential.

Mechanical motion is unavoidably accompanied by vibration, which has an effect on fluid heat transfer. However, few investigations have been conducted on the effects of vibration on heat transfer characteristics of supercritical CO2 (SCO2). In this paper, effects of transverse vibration on heat transfer characteristics of SCO2 during upward flow in a vertical tube (d = 4.57 mm, 20379 <= Re <= 88285) are studied experimentally. The results show that vibration achieves heat transfer enhancement. Specifically, with the increase of vibration amplitude and vibration frequency, the wall temperature decreases, the heat transfer coefficient increases, and the heat transfer enhancement efficiency (HTE) shows an upward trend. HTE of amplitude outweighs that of frequency over the test range, with an HTE of up to 32.70%. Heat transfer enhancement of vibration mainly acts in the region before mainstream enthalpy reaches pseudo-critical enthalpy. Based on pseudo-boiling theory, the reason for vibration-enhanced heat transfer is analyzed. Vibration weakens the thickness of gas-like film near the wall, thus accelerating heat transfer between the cold mainstream and the wall. A heat transfer correlation for vertical tubes under vibration is proposed based on 3822 experimental data points, which captures 94.2 % of the experimental data within +/- 30 % error.