Objective:To support complex aerospace missions including manned spaceflight,Mars exploration and space station construction,it is critical to conduct deep-space exploration research for solar-system planets and even extrasolar space.High-specific-impulse cryogenic fluids such as liquid hydrogen-liquid oxygen(LH2-LOX)and liquid oxygen-liquid methane(LOX-LCH4)are primary propellant for deep-space missions.During flight,cryogenic fluids in propellant tanks undergo gravity changes,leading to interface relocation.Owing to low surface tension and viscosity,their interfaces easily deform and break up,resulting in complicated flow behaviors.Meanwhile,increased interfacial and contact areas enhance heat transfer,triggering intense phase change due to low boiling points and latent heats,making thermal states unpredictable.This study aims to reveal the evolution of interface dynamics and thermal behavior during relocation,which is essential for the design of on-orbit propellant management devices. Methods:In this study,a drop-tower experimental platform for LOX reorientation was constructed.The setup,housed in a stainless-steel vacuum chamber with sapphire windows for optical access,uses multilayer insulation and combined LED lighting to enable high-speed visualization.A liquid nitrogen cooling circuit connected via copper braids provides stable precooling and suppresses boiling.The test cell,made of sapphire with high pressure resistance,is instrumented with multiple temperature sensors.LOX is condensed and stabilized at a height of 18.5 mm until thermal drift is below 0.000 1 K/s.The system is then installed in the drop tower tube,adjusted for center-of-mass,and released from 83 m to generate nearly 3.5 s of microgravity at approximately 0.004 4 g₀.High-speed images are recorded and processed using a MATLAB edge-detection algorithm to analyze interface evolution during the relocation process.Meanwhile,the vapor-phase temperature and pressure were measured.During the drop-tower process,the overload environment transitioned from normal gravity to microgravity. Results and Discussions:The LOX propagated along the inner wall and formed a liquid layer.The motion of this liquid layer was decoupled from that of the bulk liquid,and the interface center oscillated continuously.Owing to the ascend of the contact line,the gas-liquid interface area increased,and LOX evaporated continuously at the contact line.The emergence of the liquid layer resulted in a pressurization rate of 3 227 Pa/s at the first oscillation of the contact line,which is approximately 1.8 times higher than the final stabilized pressurization rate.During the entire 2.5 s reorientation process,the pressure in the gas-phase region increased by 4 217 Pa.The temperature variation at 15.2 mm from the interface was affected by not only heat transfer from the solid wall but also disturbances from the low-temperature gas flow induced by interface oscillations.Additionally,the temperature at this measurement point increased by only 0.351 K during the entire reorientation process. Conclusions:This study concludes that the evolution of the LOX interface,temperature and pressure in the ullage in the interface reorientation process.This experiment provides the cryogenic fluid data for simulation validation and guidance for the configuration and design of cryogenic-propellant management devices.
Human thermal regulation models reflect the physiological response of the human body to the surrounding thermal environment.However,existing thermal regulation models do not account for the non-uniform impact of solar radiation on indoor thermal environments and the human body.Therefore,a new model was established by modifying the thermal regulation model of the human body to include local exposure to direct sunlight in buildings.First,the calculation of mean radiant temperature was revised by distinguishing direct and indirect areas.Second,the calculations of skin and clothing temperatures and heat loss in the model were modified by distinguishing direct and indirect parts.In addition,solar radiation heat gain was added to the heat transfer calculations.After experimental verification,the modified model demonstrated a relative error of less than 5%in predicting mean skin temperature,and approximately 4%in predicting total heat loss.Using the model,the mean skin temperature at different activity levels was predicted,and the thermal comfort zone offset laws of the human body as a whole and in direct parts were explored at different solar radiation intensities.The results show that the acceptable air temperature of the overall body at 400 W/m2 is 2℃lower than that at 200 W/m2.This study provides a theoretical basis for zoning control of indoor environments under direct sunlight.
Linear compressors eliminate the slider-crank mechanism and facilitate oil-free operations. Self-lubricating opposed-piston linear compressors are suitable for integration into attitude-following heat-pump systems while significantly enhancing the system flow rate. In this study， a dual-motor self-lubricating opposed-piston linear compressor prototype was developed， and a comprehensive test bench was established. Using the R1234yf refrigerant， variable-capacity experiments were conducted to analyze the dynamic responses under series and parallel power supply modes. The results indicate that parallel drive requires a lower voltage than series mode， reducing the voltage differential required to achieve synchronized piston strokes in opposing configurations. During 62 Hz operation， when the supply voltage increased from 120 to 160 V， the series mode maintained， on average， a 0.17 higher power factor and 8.1% greater motor efficiency compared with the parallel mode. Thus， the driving mode selection should consider the specific application requirements.
With the rapid development of artificial intelligence and high-performance computing， cold-plate liquid cooling technology has gradually become a mainstream solution for satisfying the heat-dissipation demands of high-heat fluxes data centers. This paper describes the triggering mechanisms， impact hazards， and the coupled evolution patterns of typical faults in data center cold-plate liquid cooling systems. The principles and characteristics of direct-detection techniques and inverse-problem fault diagnosis techniques are then summarised based on operational data and outlines the key problems encountered when applying these diagnostic techniques to real-world cold-plate liquid cooling systems. Finally， based on diagnostic experience in the HVAC （heating， ventilation and air conditioning） field， this study concludes the targeted methods for addressing these problems， including semi-supervised learning， few-shot learning， data augmentation， and physics-data fusion. Future research could focus on multi-algorithm fusion， mitigating data imbalance， and enhancing model interpretability and anti-interference capabilities to improve the accuracy， reliability， and engineering applicability of fault identification. The review and synthesis presented in this paper can serve as a reference for both theoretical research and engineering applications in the field of cold-plate liquid-cooling fault diagnosis.
ObjectiveCombined heat and power centralized heating can supply steam to surrounding industrial enterprises by using the steam from turbine， which is an efficient way of steam supply. However， as the supply distance increases， the temperature drop and pressure loss of the steam become severe. This study aims to propose a new absorption-compression coupled high-temperature heat pump cycle system， which uses the existing combined heat and power pipeline network to transport hot water and generates steam at the user site， effectively expanding the coverage of combined heat and power steam supply. In this paper， a thermodynamic simulation model of the heat pump system is established， and the influences of the supply water temperature of the primary network， the temperature of the micro-pressure steam， and the steam supply temperature on the performance of the heat pump are analyzed in detail.MethodsThis study combines the absorption heat exchanger with the vapor compression heat pump， and proposes an absorption-compression coupled high-temperature heat pump cycle system. This paper uses theoretical simulation methods to analyze the influence of key parameters on the performance of the heat pump system. Based on the principles of energy conservation and mass conservation， the thermodynamic steady-state model of the system is established， and the thermodynamic equations are solved using the engineering equation solver （EES） software. Through parameter sensitivity analysis， the effects of the supply water temperature of the primary network， the micro-pressure steam temperature， and the steam supply temperature on the system performance are studied.Results and Discussions The higher the supply temperature of the primary network， the greater the capacity of the absorption heat exchanger to increase the temperature， the larger the COP of the coupled system， and the lower the unit steam consumption. When the supply water temperature is 120 ℃ and the steam generated is 180 ℃， the temperature rise coefficient of the absorption heat exchanger is 0.37. The coupled system COP is 2.56， and the unit steam consumption is 292.5 kW∙h/（t/h）. Compared with the case where the supply water temperature is 95 ℃， the COP increases by 2.7%， and the unit steam consumption decreases by 2.5%. As the temperature of the micro-pressure steam increases from 75 ℃ to 100 ℃， the COP of the coupled system first increases and then decreases， and the unit steam consumption first decreases and then increases. When the temperature of the micro-pressure steam is 80 ℃， the COP of the coupled system is the maximum value of 2.6， and the unit steam consumption is the minimum value of 285.3 kW∙h/（t/h）. As the steam supply temperature increases， the COP of the coupled system monotonically decreases， and the unit steam consumption monotonically increases. When the steam supply temperature increases from 100 ℃ to 200 ℃， the COP of the coupled system decreases from 4.3 to 2.3， and the unit steam consumption increases from 166.2 kW∙h/（t/h） to 316.0 kW∙h/（t/h）.ConclusionsThe absorption-compression coupled high-temperature heat pump system proposed in this paper provides an effective solution for long-distance hot water supply to steam. The supply water temperature of the primary network， the micro-pressure steam temperature， and the steam supply temperature are the key factors affecting the system performance. This system offers a feasible approach for expanding the steam supply range of combined heat and power and improving the comprehensive energy utilization rate.
Against the backdrop of global climate change mitigation and the accelerating transition toward low-GWP refrigerants, research on alternative refrigerants for variable refrigerant flow (VRF) systems has emerged as a critical focus in refrigeration and air conditioning. This paper presents a comprehensive review of recent advances in low-GWP refrigerant replacement technologies for VRF systems. A three-dimensional analytical framework encompassing "policy-performance-technology" was developed to systematically evaluate the influence of regulatory policies in major global economies on technological pathways and to assess the thermophysical properties of alternative refrigerants such as R32 and R454B. The findings indicated that R32 offered a 2.1%-10.2% improvement in energy efficiency compared with R410A although stricter control measures were required because of its A2L flammability classification. In contrast, low-GWP refrigerants, such as R454C, met environmental requirements but resulted in a 5.9%-7.6% decline in energy efficiency. Key technological breakthroughs were reviewed, including compressor optimization, lubricant management, and long-distance refrigerant distribution. Special emphasis was placed on safety-enhancing solutions such as intelligent refrigerant charge diagnostics based on deep learning and the application of secondary loop systems to reduce the charge of flammable refrigerants. To address the challenges related to material compatibility and system integration, a phased implementation roadmap was proposed. This review provided a systematic theoretical foundation for the low-carbon transition of the VRF industry and offered valuable insights for future policymaking and technology development.
To improve heat dissipation in the thermal management of batteries for electric vehicles,this study proposes a bionic structure based on shark scales.The design optimizes a phase-change material(PCM)heat sink in conjunction with axial air cooling to regulate battery temperature.Based on performance tests of the battery,a three-dimensional model was built to investigate and compare the heat dissipation of the battery under different conditions,including natural convection,forced convection,forced convection coupled with PCM,and forced convection coupled with bionics-optimized PCM.The results indicate that the temperature rise of the battery with the forced convection coupled with bionics-optimized PCM is only 33.6%of that with natural convection at a 2 C discharge rate,and the average temperature of the battery is 41.8 ° C,which keeps the battery within a suitable temperature range.In addition,the bionic structure can reduce the pressure drop at the inlet and outlet by 4%compared with the traditional method.
Silica gel desiccant wheel is the main dehumidification technology to realize humidity control of ambient air. Optimizing the wheel size and reducing the operating energy consumption are necessary trends in technology development. In this study, based on computational fluid dynamics (CFD), we first established and verified a three-dimensional dynamic simulation model of the dehumidification and regeneration process of the desiccant wheel. We conducted a dynamic simulation for the silica gel desiccant wheel used for the protection of bridge cables. We then analyzed and discussed the influence of wheel thickness, wind speed, and regeneration wind volumetric flow rate and temperature on the moisture removal capacity (MRC) and specific energy consumption (SEC) to optimize the design of the desiccant wheel. The results showed that the optimal thickness increased with the increase in wind speed. Compared with the original design, the optimized wheel improved the average MRC by approximately 10% while reducing the SEC by approximately 15%, demonstrating the effectiveness of geometry optimization. Notably, the SEC decreased with increasing regeneration temperature. Therefore, in practical design, the regeneration temperature should be selected in accordance with the dehumidification requirements and maintained as low as feasible to enhance the overall economic performance.
To solve the problems of the slow growth rate and low cold thermal energy storage density of refrigerant hydrates,the addition of surfactants is an effective way to promote hydrate formation.Three polyoxyethylene castor oil(EL)surfactants with different hydrophilic-lipophilic balance(HLB)values(EL-20,EL-30,and EL-60)were selected as promoters to study their effects on HCFC-141b hydrate formation.The experimental results showed that the EL series of surfactants significantly reduce the hydrate nucleation induction time.The system with a mass fraction of 1.5%EL-20 exhibited the shortest hydrate induction time of 73 min,and the stability of hydrate formation was good.The micelles formed by the EL surfactants provide more nucleation sites,which accelerate hydrate formation.The hydrate cold thermal energy storage density is related to the HLB value of the surfactants.The system with a mass fraction of 1.5%EL-20 had the maximum cold thermal energy storage density of 246.48 kJ/kg and the fastest hydrate growth rate of 5.06 kJ/(kg·min),as EL-20 had a suitable HLB value.There is a"memory"effect during hydrate formation and dissociation cycle.The system with a mass fraction of 1.5%EL-20 surfactant exhibited the most favorable performance during the hydrate formation and dissociation cycles.After seven hydrate formation and dissociation cycles,the increase in temperature remained stable during hydrate formation.
Appropriate addition of the surfactant cetyltrimethylammonium bromide(CTAB)can significantly reduce solution surface tension and promote boiling heat transfer.In this study,it was applied to a pulsating heat pipe(PHP),and the experimental study was guided using response surface methodology(RSM).The influence of heating power(Q=10-105 W),filling ratio(α=25%-75%),and CTAB concentration(ω=0-0.29%)on the heat transfer performance of PHP was studied.The results show that the proper addition of CTAB(e.g.,ω=0.145%)at a moderate filling ratio(α=50%)can effectively improve the operation of PHP,reduce thermal resistance,and transform temperature fluctuation characteristics at lower powers.In terms of influencing factors,the heating power had the greatest influence,followed by the filling ratio,whereas concentration had the least influence.The interaction between heating power and filling ratio was the most significant,whereas that between the filling ratio and concentration was not significant.The minimum thermal resistance was predicted as approximately 0.32℃/W,and a relatively wide optimal operating condition area existed,which makes the overall thermal resistance of PHP relatively small.This is beneficial for the practical application and performance optimization of PHP in engineering.
A front-jet-assisted cooling scheme is proposed for single-phase immersion oil-cooled servers to address severe bypass flows， insufficient effective flows inside heat sink channels， and local hotspots. Numerical simulations were performed to investigate the associated flow redistribution and mechanisms for heat-transfer enhancement. The results show that introducing front jets enhanced the coolant momentum and renewal at the heat sink channel entrance through local impingement， stagnation pressurization， and entrainment. In addition， the jet flow ratio primarily governed the enhancement intensity， whereas the number of jet holes assigned to each GPU heat sink primarily affected the coverage range and temperature uniformity. Comprehensive comparison indicates that the case with five jet holes and a jet ratio of 0.8 demonstrated the best overall performance， reducing the maximum GPU temperature from 99.12 ℃ to 82.10 ℃ and the temperature standard deviation from 2.54 ℃ to 0.26 ℃.
Microchannel heat sinks （MCHS） offer broad application prospects in battery thermal management systems （BTMS） due to their high heat-transfer coefficient （HTC） and compact structures. In response to the stringent requirements for temperature uniformity in power batteries， this study reviews the recent research progress in optimizing temperature uniformity across single-phase and two-phase liquid-cooled microchannel heat exchangers， analyzing the mechanisms of temperature non-uniformity， structural optimization methods， and manufacturing feasibility. The results indicate that the temperature non-uniformity in single-phase liquid-cooled microchannels is caused by the uneven flow distribution among the parallel channels and the gradual heating of the coolant along the flow path. Optimization measures， such as improving inlet and outlet arrangements， enhancing manifold structures， employing biomimetic or topological flow paths， and implementing variable-density disturbance structures， can effectively improve the temperature distribution. For two-phase liquid-cooled microchannels， temperature uniformity is influenced by the flow distribution and bubble behavior， requiring surface modification and special structures to regulate the gas-liquid phase distribution. Comparative analysis reveals that the optimization of single-phase flow focuses on improving the liquid flow distribution and enhancing the downstream heat transfer， whereas the key to two-phase flow optimization lies in controlling the bubble behavior. Moreover， the engineering applications of complex microchannel structures are limited by manufacturing costs， processing precision， and long-term reliability. These findings offer practical guidance for designing temperature-uniform structures in MCHS for BTMS.
This study provides a systematic review of the emerging twistocaloric cooling technology， which shows significant potential for the applications in high-efficiency solid-state refrigeration by driving reversible microstructural changes via twisting and untwisting. Firstly， the mechanism and mathematical models for refrigeration by the twistocaloric effect are elucidated， revealing the principles for realizing a high entropy change and thermodynamic efficiency. Subsequently， the influences of key factors， including the twist degree and rate， ambient temperature， and geometric parameters of the material， are analyzed， and a comprehensive evaluation system focused on the hysteresis effects， coefficient of performance （COP）， and fatigue life is established. Based on the analyses， the research progress of materials like natural rubber， polymers， and NiTi shape memory alloys are reviewed in detail， verifying that twistocaloric cooling yields significant temperature changes while offering the integrated advantages， e.g.， a high COP and low hysteresis and an excellent cyclic stability. Finally， the application potentials of twistocaloric cooling in fields such as the microelectronic cooling and green refrigeration are discussed， indicating the critical value of the "twist-instead-of-stretch" technical pathway in advancing the development of solid-state refrigeration.
In response to the urgent demand for large-scale transoceanic transportation of liquid hydrogen， this study focuses on an 8 000 m³ Molten Salts Storage （MOSS）-type marine liquid hydrogen spherical tank for a thermal-structural multiphysics coupling analysis and structural integrity assessment in liquid hydrogen temperature zone. A three-dimensional finite element model is developed， incorporating a composite insulation layer of hollow glass microspheres （HGM） and a resilient blanket integrated with composite support components. In accordance with International Maritime Organization （IMO） regulations， three typical navigation conditions—namely， the Equator， International Gas Carrier code， and United States Coast Guard standards—are simulated. Thermodynamic calculations demonstrate excellent insulation performance， yielding boil-off rates between 0.123% and 0.158% across all operating conditions， thereby satisfying the design target （0.2%）. Mechanical analysis reveals that the thermal strain induced by the extreme cryogenic temperature （-253 ℃） dominates coupled deformation and leads to significant stress concentration at support joints. Using stress linearization in accordance with ASME VIII-2 design-by-analysis standard， the local peak stress is effectively separated. The results show that the maximum combined primary and secondary stress is 493.6 MPa， which is below the allowable stress limit of 600 MPa. This study elucidates the multiphysics coupled mechanical response characterisitcs of large-scale MOSS-type liquid-hydrogen spherical tanks under extreme operating conditions， providing practical engineering references and technical insights for the structural design， insulation optimization， and safety assessment of seaborne liquid-hydrogen storage and transportation equipment.
ObjectiveAir-cooled， parallel-plate channels used in battery packs， electronic chips， and compact heat exchangers are commonly limited by the trade-off between heat transfer and pressure drop. Although dimpled surfaces can intensify near-wall mixing at a relatively low manufacturing cost， their overall thermal-hydraulic performance is highly sensitive to the geometric configuration. To address this issue， this study investigates a novel parallel-plate channel equipped with a dimpled plate featuring reverse-side protrusions. This study aims to clarify the effects of major geometric parameters on the coupled flow and heat transfer characteristics， and to identify an optimal compromise design that enhances heat transfer while suppressing the pressure drop.MethodsA three-dimensional， periodic unit of a plate channel was established and solved using steady-state computational fluid dynamics. Air was treated as an incompressible fluid with constant thermophysical properties. Periodic boundary conditions were adopted for the inlet and outlet of the computational domain. Grid independence was achieved at approximately 5.68 million cells. The numerical method was validated against published pillow plate experimental data. Three geometric parameters were selected as decision variables， namely the depth of the large dimple （R1=2.5-4.0 mm）， the depth of the small dimple （R2=0.5-2.0 mm）， and the dimple inclination angle （α=30°-60°）. A total of 64 design cases were used to construct the sample database. Based on these CFD data， Extreme Gradient Boosting （XGBoost） surrogate models were trained for Nu and Δp. The trained models were then coupled with the Non-dominated Sorting Genetic Algorithm II （NSGAII） to perform multi-objective optimization， and the entropy-weighted technique for order preference by similarity to ideal solution （TOPSIS） was employed to determine the best compromise solution.Results and DiscussionsUnivariate analysis reveals that R1， R2， and α all have significant influences on the thermal-hydraulic performance. Increasing R1 intensifies the flow separation and reattachment and enlarges the recirculation zone. Consequently， the heat transfer performance （h） increases rapidly. However， once R1 exceeds a certain level， the increase in h becomes much smaller than the increase in frictional resistance （f）， resulting in a turning point in the comprehensive performance. Both h and f increase rapidly with an increase in R2； beyond a certain threshold， further increases in R2， cause the trends of h and the performance evaluation criteria （PEC） gradually flatten out. Additionally， h and f show a tendency to increase and then decreasing with the increase of α. The XGBoost surrogate model reproduces the CFD results with high accuracy. The maximum deviations are only 0.44% for Nu and 3.31% for Δp， while the coefficients of determination （R²） reach 0.999 6 and0.998 2， with root mean square errors of 2.94 and 6.42， respectively. Fourteen nondominated solutions were obtained on the Pareto front. The highest ranked compromise solution selected by entropy-weighted TOPSIS corresponds to R1=2.8 mm， R2=0.6 mm， and α=47°. Further CFD simulations over Re=5 000-10 000 confirm that the optimized structure had superior overall heat transfer performance.ConclusionsThe dimpled plate with reverse-side protrusions provides an effective passive strategy for enhancing air-side heat transfer in parallel-plate channels. However， maximizing thermal-hydraulic performance requires a rational combination of large dimple depth， small dimple depth， and inclination angle， rather than merely increasing geometric disturbances. The XGBoost， NSGAII， and TOPSIS frameworks provides a reliable and efficient approach for the multi-objective design of enhanced heat transfer surfaces. For the present channel， the optimized geometry achieves a PEC of approximately 1.55 under equal pumping power over the entire investigated Re range， indicating substantial comprehensive performance improvements， promising application potential in battery thermal management， chip cooling， and other compact forced-air cooling devices.
To meet the demands of lightweight design and real-time control in short-duration， high-heat-load thermal management systems， this study investigated the transient discharge performance of a fin-and-tube phase-change cold storage unit to address the limitations of conventional numerical simulations in simultaneously providing physical insight and online prediction efficiency. First， a three-dimensional transient model for the external phase change material based on the enthalpy-porosity method and a one-dimensional transient flow model for the internal refrigerant were established. A coupled three-dimensional/one-dimensional bidirectional thermal framework was developed to reveal the transient response of the cold storage unit under the combined effects of phase-change heat transfer and along-tube pressure drop. The results show that， under typical operating conditions， the average heat transfer rate reaches 88.29 kW over an 80 s operating period. As the phase change proceeds， the thickened liquid layer increases thermal resistance and continuously weakens the heat transfer capacity of the unit. At 80 s， the along-tube pressure drop approaches 0.3 MPa， and the pressure-drop-induced decrease in saturation temperature is identified as the primary cause of the non-monotonic inflection in the outlet temperature. To enable rapid performance prediction， a particle swarm optimization Extreme Gradient Boosting surrogate model embedded with a transport delay criterion and thermodynamic consistency constraints was developed. The prediction results show that the coefficients of determination for the outlet pressure， outlet enthalpy， and average phase change material temperature of the independent test set exceed 0.98. Crucially， the transport delay criterion reduces the root mean square error of the refrigerant outlet temperature prediction from 1.214 ℃ to 0.580 ℃， providing technical support for the rapid performance evaluation of phase-change cold storage systems and system-level model predictive control.
ObjectiveSmall-intestinal organoids are highly valuable for intestinal physiological research and drug screening. However， their cryopreservation is often limited by low recovery rates as well as structural and functional damage. This study aimed to establish an efficient and stable slow-freezing protocol for small intestinal organoids by introducing controlled ice nucleation （seeding） and optimizing the key cooling parameters.MethodsFocusing on slow-freezing， a seeding step was incorporated into the conventional protocol to investigate the effects of seeding temperature， terminal temperature for ice crystal growth， and cooling rate on cryopreservation outcomes. Evaluations included assessing survival rates， H&E staining for morphology， and immunofluorescence for proliferation markers and junction proteins. RT-qPCR was used to measure the expression of stemness and multilineage markers.Results and DiscussionsSeeding significantly enhanced post-thaw recovery， increasing viability from （85.05±3.06）% to （88.84±1.78）%， with H&E staining revealing better organoid architectural preservation. Parameter optimization identified an optimal protocol consisting of ice nucleation at -8 ℃ followed by cooling at 0.5 ℃/min to -60 ℃. This optimized regimen achieved a significantly higher survival rate （89.02%±2.06%） than the conventional passive cooling box method （83.11%±2.45%）. Morphological and immunostaining analyses demonstrated that recovered organoids exhibited compact structures and enhanced proliferation. Additionally， upregulated expression of stemness， epithelial junction integrity， and multilineage genes confirmed the effective preservation of their full-spectrum differentiation potential.ConclusionsSeeding actively induces ordered ice nucleation， thereby reducing the mechanical damage caused by excessive supercooling. The optimized protocol outperforms traditional methods in survival， structural integrity， and biological function， thus providing technical support for organoid biobanking and standardized applications.
In indoor environments， people are often exposed to the non-uniform thermal radiation. Most existing research focuses on changes in human thermal physiological responses and subjective thermal sensations under a single type of thermal radiation， such as solar radiation or infrared radiation. To examine the differences in human thermal responses under solar radiation and infrared radiation conditions， this study conducted separate local thermal exposure experiments involving solar and infrared radiation. Under both testing conditions， skin temperature was measured and thermal sensation votes were collected. Differences in thermal sensitivity across body parts under two radiation conditions were then calculated and analyzed. The results showed that， under the effect of solar radiation， a unit increase in radiation intensity caused skin temperatures at various body parts to increase by 0.01-0.02 ℃， whereas infrared radiation produced a relatively greater increase in skin temperature at the exposed area， with reaches up to 1.0 ℃. The greatest changes in the overall thermal sensation occurred when the chest was stimulated by solar or infrared radiation， exceeding 2.0 scale units. Upon stimulus application to limbs， such as the upper arm， forearm， thigh， and calf， overall thermal sensation changed most under the condition of 400 W/m2 solar radiation， whereas differences in overall thermal sensation were not significant under 200 W/m² solar radiation and 4 W/m² infrared radiation. Under local exposure to solar radiation， thermal sensitivity ranged from high to low in the order of chest， upper arm， forearm， thigh， and calf， whereas under local radiant heat exposure to infrared radiation， thermal sensitivity ranged from high to low in the order of chest， upper arm， calf， thigh， and forearm. These findings provide a reference for more accurate prediction of human thermal responses in radiant heat environments， and for optimizing indoor thermal environments.
The formation mechanism of high-temperature zones in counterflow microchannel heat sinks was investigated through computational fluid dynamics numerical simulations. The following two novel structures were proposed： an outlet top-rib structure and a channel center top-rib structure. The results showed that the inlet effect of edge channels and transverse heat transfer between adjacent channels were the identified as fundamental causes of the parallelogram-shaped high-temperature zones. The uniform bottom rib structure enhanced overall heat transfer； however， the parallelogram-shaped high-temperature zones still persisted. For edge channels， the outlet top rib structure weakened heat transfer at the inlet region and strengthened heat transfer at the outlet region， thereby modifying the morphology of the parallelogram-shaped high-temperature zones and decreasing the maximum wall temperature difference by 33.3%. The channel center top rib structure enhanced heat transfer in the high-temperature zones at the channel center， further reducing the maximum wall temperature difference by 58.3%. Furthermore， it achieved the same average wall temperature as the uniform bottom-rib structure at a low flow rate （1.64 g/s） and outlet top-rib structure at a large flow rate （2 g/s）， while reducingwall temperature difference by 64.8% and 47.2%， and pressure drop by 9.1% and 12.0%， respectively.
This study prepared composite phase-change cold storage materials using carbonized melamine sponge （CMS） and NaCl aqueous solution to address the problems of low energy storage density and large supercooling degree of traditional sodium chloride （NaCl） aqueous solution， and broaden their application in cold thermal energy storage. Fifteen CMS samples were prepared by sintering melamine sponge （MS） at different temperatures and durations in air. The microstructures， thermal conductivities， mechanical properties， and surface wettability of the CMS were systematically characterized. The phase-change characteristics of NaCl aqueous solutions with different concentrations were further explored， and the CMS prepared by the optimal process was compounded with an NaCl aqueous solution to analyze the variation rules of the energy storage density and supercooling degree of the composite materials. The experimental results showed that the CMS sintered at 400 ℃ for 150 minutes exhibited a uniform porous structure and a thermal conductivity of 0.039 41 W/（m·K）， which was 36.7% higher than that of the original MS. Additionally， the CMS exhibited good hydrophilicity， which enabled effective adsorption of the NaCl aqueous solution. Although the high porosity resulted in a slight decrease in its mechanical properties， the material could still satisfy the application requirements of composite cold storage materials. The phase change characteristics test showed that the latent heat of phase change of the NaCl aqueous solution decreased with increasing concentration， while the degree of supercooling initially increased and subsequently stabilized. Compared with pure NaCl aqueous solution， the composite material prepared by CMS sintered at 400 oC for 150 minutes， and NaCl aqueous solution exhibited an energy storage density increase of 6.3%~15.3%， and a significant reduction in supercooling degree of 8.2%~70.1%. The results indicate that CMS can effectively enhance the phase-change energy-storage performance of NaCl aqueous solutions and inhibit supercooling. The prepared composite phase-change cold-storage material demonstrates good application potential， which provides a theoretical basis as well as technical reference for the design and preparation of high-efficiency cold-storage materials.
