Energy-efficient intermittent liquid heating of lithium-ion batteries in extreme cold using phase change materials

The electrochemical performance of lithium-ion batteries significantly deteriorates in extreme cold.Thus,to ensure battery safety under various conditions,various heating and insulation strategies are implemented.The present study proposes a hybrid heating approach combining active heating with passive insulation.Conceptual experiments were conducted to investigate the effects of phase change materials(PCMs),inlet water temperature,and intermittent pump startup strategies on battery performance.The obtained experimental results demonstrate that low temperatures lead to increased electrochemical impedance and reduced charge–discharge capacity in batteries.Notably,charge transfer resistance of 162 mΩwas observed at-30℃.Herein,the developed PCM-based battery heating system effectively extended the operational capacity of batteries in cold driving conditions and maintained battery warmth by leveraging the superior heat storage capability of the PCM.Additionally,after the switch off of the heating system,the charge capacity of the battery exceeded 80%owing to latent heat.The use of an intermittent heating strategy not only allowed to conserve energy but also maintained adequate heat storage within the battery module.At-30℃,this strategy enhanced the power efficiency of the cooling system by 35.94%with a reduction in capacity of only 0.8%compared to the continuous strategy.

Heating of Nanosized Liquid Water in High-Intensity Terahertz Pulses

Non-equilibrium molecular dynamics simulations of liquid water in picosecond high-power terahertz pulses are performed by using a non-polarizable potential model. Numerical results show that the energy absorption of water molecules exhibits a pronounced resonance with THz pulses in the frequency range of 14-17 THz. With the THz pulse at resonant frequencies, the maximum temperature is about 562 K by heating the water at room temperature. Further investigation indicates that the results are independent of the size of the nanoscale water box. The efficiency of energy transfer by resonant absorption is more than seven times of microwave heating. These studies show promising applications of ultrashort THz pulses.

Investigation of the Laser Powder Bed Fusion Process of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy

Laser powder bed fusion(LPBF)is an advanced manufacturing technology;however,inappropriate LPBF process parameters may cause printing defects in materials.In the present work,the LPBF process of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy was investigated by a two-step optimization approach.Subsequently,heat transfer and liquid flow behaviors during LPBF were simulated by a well-tested phenomenological model,and the defect formation mechanisms in the as-fabricated alloy were discussed.The optimized process parameters for LPBF were detected as laser power changed from 195 W to 210 W,with scanning speed of 1250 mm/s.The LPBF process was divided into a laser irradiation stage,a spreading flow stage,and a solidification stage.The morphologies and defects of deposited tracks were affected by liquid flow behavior caused by rapid cooling rates.The findings of this research can provide valuable support for printing defect-free metal components.

Fluctuating specific heat in two-band superconductors

Theory of thermal fluctuations in two-band superconductors under an essentially homogeneous magnetic field is developed within the framework of the two-band Ginzburg-Landau theory. The fluctuating specific heat is calculated by using the optimized self-consistent perturbation approach and the results are applied to analyze the thermodynamic data of the iron-based superconductors Ba（1-x）KxFe2As2 with x -0.4, which have been suggested to have a two-band structure by recent experiments. We estimate the fluctuation strength in this material and find that the specific heat is described well with the Ginzburg number Gi = 4 · 10^-4. The influence of interband coupling strength is investigated and the result of the two-band Gaussian approximation approach is compared.

An introduction to the novel vacuum plume effects experimental system

This paper introduces a newly developed vacuum Plume effects Experimental System(PES) used for plume effect tests of rocket engines and vacuum heat tests of satellites. The design level, manufacturing technique, and testing capabilities of the PES have reached a highly advanced level at home and abroad. The PES mainly consists of a vacuum chamber, vacuum acquisition system, nitrogen system, helium system, and parameter measurement system. A breakthrough was obtained on the Large Scale Cryo-Pumping System, which was based on a combined liquid nitrogen and liquid helium heat sink. An internal cryopump with a limiting temperature of 4.2 K and an efficient absorption area of 305 m2 was developed. The absorption capability of the cryopump was above 7×107 L/s. Vacuum plume tests were performed in the temperature ranges of ambient temperature, liquid nitrogen, and liquid helium. The experimental results showed that the plume test capability of PES is higher than that of similar foreign equipment STG and CHAFF-4. For 2 g/s and 117 N rocket engines, the dynamic vacuum degree of environment was 8.0×10?4 Pa(approximately 137 km height) and 1.1×10?2 Pa(approximately 106 km height), respectively.

Local heat transfer properties in co- and counter-current G-L-S magnetically stabilized fluidized beds

Heat transfer coefficients were measured by immersed probes in co- and counter-current G-L-S magnetically stabilized fluidized beds （MSFBs） using air, water and nickel-alloy particles as the gas, liquid and solid phases. Influences of major factors, including magnetic field intensity, superficial gas and liquid velocities, liquid viscosity and surface tension, on heat-transfer properties were studied experimentally, indicating that both co- and counter-current G-L-S MSFB can provide relatively uniform radial distribution of heat transfer coefficients under appropriate operation conditions, thus controlling operation temperature for highly exothermic multi-phase reaction systems. Two correlations were provided to estimate accurately heat transfer properties in both co- and counter-current G-L-S MSFB systems, with an average error of less than 10%.

Flow Structure and Heat Exchange Analysis in Internal Cooling Channel of Gas Turbine Blade

This paper presents the study of the flow structure and heat transfer,and also their correlations on the four walls of a radial cooling passage model of a gas turbine blade.The investigations focus on heat transfer and aerodynamic measurements in the channel,which is an accurate representation of the configuration used in aeroengines.Correlations for the heat transfer coefficient and the pressure drop used in the design of radial cooling passages are often developed from simplified models.It is important to note that real engine passages do not have perfect rectangular cross sections,but include coiner fillet,ribs with fillet radii and special orientation.Therefore,this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which possesses very realistic features.