Article
Physics, Applied
Lei Yang, Bing-Yang Cao
Summary: In this study, the thermal conduction in amorphous PCM materials was quantified, showing that coherences contribute over 97% to the total thermal conductivities, while the populations' contribution is negligible. By introducing an extension method in the AF theory, the positive temperature dependence of thermal conductivities in GeTe4 material was successfully predicted.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Xingkun Ning, Yaolong Dong, Weixiong Jian, Jinrong Wang, Wenbo Guo, Shufang Wang
Summary: Quantum well (QW) superlattice is proposed to enhance thermoelectric properties and serve as a platform for the next generation of thermoelectric devices. Previous QW faced challenges of electron tunneling in semiconductor-based multiple QWs (MQW) and high thermal conductivity in oxide-based MQWs. This study demonstrates amorphous based PbTe/amorphous-STO MQWs with ultrahigh power factor and record low thermal conductivity. The high performance is attributed to quantum confine effect and low thermal conductivity of amorphous superlattice structure, providing a new avenue for modulating thermoelectric properties.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Physics, Multidisciplinary
Takafumi Ishibe, Ryo Okuhata, Tatsuya Kaneko, Masato Yoshiya, Seisuke Nakashima, Akihiro Ishida, Yoshiaki Nakamura
Summary: In this study, researchers observed extremely small interface thermal resistance at the interface of the amorphous-germanium sulfide/epitaxial-lead telluride superlattice. Ab initio lattice dynamics calculations indicated that high phonon transmission through this interface can be predicted, suggesting that controlling phonon density-of-states and phonon group velocity similarity can be a comprehensive guideline to manage heat conduction in nanoscale systems.
COMMUNICATIONS PHYSICS
(2021)
Article
Thermodynamics
Shijie Chen, Feihu Zheng, Jiachen Li
Summary: This paper presents a novel method for measuring thermal conductivity of micro-quantity liquid based on the modified thermal pulse method. The factors affecting the measurement range and accuracy of the technique are analyzed through numerical simulations and experiments. The experimental results show that the method has the advantages of low measuring time, low fluid usage, wide measurement range, good sample compatibility, and high accuracy.
APPLIED THERMAL ENGINEERING
(2023)
Article
Thermodynamics
Aichun Ma, Chenghan Cai, Shiyice Peng, Tian Zhou
Summary: A combined method is proposed in this paper to determine the thermal conductivity of phase-change materials (PCMs). The method focuses on mitigating the effect of factors excluded in the measurement model but present in real experiments. A measurement model is established to mathematically relate the thermal conductivity to the liquid fraction during the melting process. An experimental system is developed using two different PCMs, with the obtained thermal conductivity showing an increasing trend during the melting process. A numerical calibration approach is presented to mitigate the influence of enhanced heat transfer rate due to natural convection. The calibrated thermal conductivity deviates from reference data by less than 8%, meeting practical engineering requirements.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2023)
Article
Physics, Multidisciplinary
M. J. Leng, B. H. Wu, A. J. Lu, L. C. Wu, C. R. Wang, Z. T. Song
Summary: The study investigated the off-stoichiometric effect on the thermal and structural properties of Ge1-delta Te using molecular dynamics, showing that Ge1-delta Te still retains its ability of rapid phase transition with slightly reduced thermal conductivity as delta increases. These results are helpful for reliable device design and modeling.
Article
Nanoscience & Nanotechnology
Sanjoy Kumar Nandi, Sujan Kumar Das, Yubo Cui, Assaad El Helou, Shimul Kanti Nath, Thomas Ratcliff, Peter Raad, Robert G. Elliman
Summary: This study investigates the thermal conductivity of amorphous NbOx films using timedomain thermoreflectance. The results show that the thermal conductivity varies with different film compositions and temperatures. Furthermore, the impact of these thermal conductivity variations on MOM devices is studied using a circuit model.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Chemistry, Analytical
Ze Feng, Xin Xiao
Summary: Phase-change materials (PCMs) are widely used in energy storage and thermal management. This study focuses on improving the thermal conductivity and flexibility of PCMs by adding expanded graphite and styrene-butadiene-styrene (SBS). The results show that the addition of SBS reduces the thermal conductivity significantly.
Article
Energy & Fuels
Yihang Jiang, Jian Huang, Peicheng Xu, Peiyong Wang
Summary: A novel method and experimental apparatuses were developed to measure the axial and radial thermal conductivities of the 18,650 LiNiCoAlO2 (NCA) lithium-ion battery. The axial conductivity of the battery generally increases with the increase in open circuit voltage (OCV) and temperature. There is no obvious relationship among the radial conductivity, temperature, and OCV, whether the core and the shell are treated separately or not.
JOURNAL OF ENERGY STORAGE
(2023)
Article
Chemistry, Physical
Zhongwei Zhang, Yangyu Guo, Marc Bescond, Jie Chen, Masahiro Nomura, Sebastian Volz
Summary: By using a heat conduction theory incorporating coherence, this study reveals that the strong phase correlation between local and non-propagating modes triggers thermal transport in amorphous materials. It further provides insights into the temperature and length dependences of thermal conductivity and uncovers the wave nature of thermal vibrations.
NPJ COMPUTATIONAL MATERIALS
(2022)
Article
Physics, Multidisciplinary
Shivam Mahajan, Massimo Pica Ciamarra
Summary: The vibrational density of states of solids determines their thermal and transport properties, with differences between crystals and amorphous solids. The boson peak and phonon attenuation in amorphous materials are related, suggesting a homogeneous isotropic elastic media with quasilocalized modes. Numerical results resolve conflicts between theoretical approaches attributing vibrational anomalies in amorphous solids to elastic disorder and localized defects.
PHYSICAL REVIEW LETTERS
(2021)
Article
Energy & Fuels
Ka Man Chung, Jian Zeng, Sarath Reddy Adapa, Tianshi Feng, Malavika Bagepalli, Peter G. Loutzenhiser, Kevin J. Albrecht, Clifford K. Ho, Renkun Chen
Summary: A systematic study was conducted to measure the effective thermal conductivity of ceramic particle beds, showing that gas conduction dominates while solid conduction and radiation contribute about 20% to the effective thermal conductivity at high temperatures.
SOLAR ENERGY MATERIALS AND SOLAR CELLS
(2021)
Article
Thermodynamics
Jian Zeng, Ka Man Chung, Qingyang Wang, Xiaoxin Wang, Yu Pei, Peiwen Li, Renkun Chen
Summary: This paper presents the development of instrumentation for measuring the high-temperature thermal conductivity of bulk and coatings using a modulated photothermal radiometry (MPR) method. The study showed that the thermal conductivities of typical solar-absorbing coatings at high temperatures range from 0.4 to 0.8 W m(-1) K-1.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Chemistry, Multidisciplinary
Xiaozhe Wang, Suyang Sun, Jiang-Jing Wang, Shuang Li, Jian Zhou, Oktay Aktas, Ming Xu, Volker L. Deringer, Riccardo Mazzarello, En Ma, Wei Zhang
Summary: The layered crystal structure of Cr2Ge2Te6 exhibits ferromagnetic ordering in the two-dimensional limit, making it a promising candidate for spintronic applications. However, the non-crystalline phase induced by external voltage pulses may lead to changes in the magnetic properties. This study demonstrates that Cr2Ge2Te6 preserves its spin-polarized nature in the amorphous phase but undergoes a magnetic transition to a spin glass state at low temperatures. Quantum-mechanical computations reveal that this transition is due to strong distortions in the Cr-Te-Cr bonds and the overall increase in disorder upon amorphization. The tunable magnetic properties of Cr2Ge2Te6 can be utilized for multifunctional magnetic phase-change devices that can switch between crystalline and amorphous states.
Article
Chemistry, Physical
Luigi Casella, Matteo Baggioli, Tatsuya Mori, Alessio Zaccone
Summary: This study presents experimental observations of phonon-polaritons in glasses and develops a theoretical framework to describe the broadening linewidth of the polariton due to disorder-induced scattering. The analysis reveals that the BP frequency and IR crossover frequency collapse onto the same power-law decay with the diffusivity of the bosonic excitation, dismissing the hypothesis of the BP being caused by a relic of the van Hove singularity. The presented framework establishes a new methodology to analyze bosonic excitations in amorphous media beyond traditional acoustic phonons, highlighting the IR crossover as the fundamental physical mechanism behind the BP.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Kaimiao Zhou, Shanfeng Li, Kang Zhao, Honghan Lin, Ze Zhang, Liang Chen, Yu Hou, Shuangtao Chen
Summary: This study proposes a coupled model to predict the performance and cooling-down process of helium turbo-expanders with brake blower, and validates the model through experiments. The results indicate that brake pressure has a significant influence on the efficiency of the turbo-expander, and a variable pressure control method is proposed to improve the efficiency during the cooling-down process.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Thermodynamics
Yu Yang, Chunchen Sheng, Gaoqiao Luo, Shuangtao Chen, Yu Hou, Liang Chen
Summary: This study evaluates three mean-line methods for the design of high-speed turbo-coolers and establishes a coupling model to predict the off-design performance and system size. The results show that the SS-CR approach has a slightly higher expander efficiency at the design point, but the PR approach performs better at low speeds. In terms of system volume, the SS-CR approach is superior to the other two methods. When the cooling capacity is controlled at 2000 W, the SS-CR approach also has a slightly higher expander efficiency compared to the other two methods.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2023)
Article
Thermodynamics
Liang Chen, Jing Fan, Pingtao Zhang, Runfeng Xiao, Yansong Si, Shuangtao Chen, Yu Hou
Summary: This paper investigates a finned tube heat exchanger with dual-side phase change heat transfer to enhance the thermal management of intermittent high-power output electronics. The use of two-phase heat transfer fluid on the tube side significantly increases the heat-charging power and storage effectiveness of LHTES. The study also reveals that the storage effectiveness decreases with the increase of condensation pressure while the mass flow rate of the tube-side fluid has no obvious effect.
APPLIED THERMAL ENGINEERING
(2023)
Article
Thermodynamics
Yu Zhang, Pingtao Zhang, Liang Chen, Shuangtao Chen, Yu Hou
Summary: This paper introduces a stacked-plate jet impingement microchannel (SP-JIMC) heat sink with highly-dense micro-fins and numerically investigates its thermal and hydraulic performance using single-phase water as coolant. Comparative analysis with other types of heat sinks demonstrates that the SP-JIMC offers better cooling performance and temperature uniformity. The study also explores the influence of structural parameters on heat transfer characteristics and proposes improvements such as dual-side micro-fins and convex/concave impinged surfaces to further enhance the thermal performance.
APPLIED THERMAL ENGINEERING
(2023)
Article
Thermodynamics
Xiaoling Yang, Liang Chen, Zhefeng Wang, Shuangtao Chen, Yu Hou
Summary: Spontaneous condensation process of moist air in a high-speed turbo-expander was investigated experimentally and numerically. A liquid fraction of 0.8% was achieved at the turbo-expander outlet corresponding to a relative humidity of 76.9% at 303.2 K. The nucleation process and droplet distribution in the turbo-expander were studied, and the wetness loss due to condensation mainly occurred in the impeller.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2023)
Article
Thermodynamics
Yang Meng, Liang Chen, Xiaoling Yang, Huaide Yang, Zhiqiang Mao, Shuangtao Chen, Yu Hou
Summary: This paper investigates the desublimation process of CO2 in a cryogenic turbo-expander and identifies the impact of inlet temperature, pressure ratio, and inlet CO2 concentration on wetness loss. The study concludes that the maximum subcooling degree for a cryogenic carbon capture system turbo-expander should be less than 15 K to avoid desublimation and wetness loss.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2023)
Article
Thermodynamics
Xiaoling Yang, Liang Chen, Zhefeng Wang, Shuangtao Chen, Yu Hou
Summary: This paper investigates the characteristics of an open-loop air cycle for room temperature applications and studies the effects of the first stage compression ratio and the expander inlet temperature on the refrigerator performance. A system model is established based on numerical simulation and verified by experiments.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2023)
Article
Thermodynamics
Runfeng Xiao, Yicheng Zhang, Liang Chen, Junxin Wang, Shuangtao Chen, Yu Hou
Summary: This paper conducts simulations of supercritical heat transfer of R134a in horizontal tubes to study the effects of circumferential heat conduction on heat transfer deterioration and explain the abnormal phenomena of higher temperature distribution in non-gravity supercritical flow. The results indicate that heat transfer deterioration is caused by impaired specific heat and heat conduction in the boundary layer, and the subsequent heat transfer recovery is due to enhanced thermal conduction and turbulent convection. A dimensionless parameter called the Biot number is defined to characterize the thermal resistance ratio of circumferential conduction to convective heat transfer. The redistribution of wall temperature caused by circumferential conduction affects supercritical convection in horizontal tubes, and non-gravity supercritical flow may have higher wall temperature when the Biot number is small. The deterioration of the top surface can be significantly alleviated by using a tube with larger wall thickness or thermal conductivity.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2023)
Article
Nanoscience & Nanotechnology
Aditya Sood, Jonah B. Haber, Johan Carlstrom, Elizabeth A. Peterson, Elyse Barre, Johnathan D. Georgaras, Alexander H. M. Reid, Xiaozhe Shen, Marc E. Zajac, Emma C. Regan, Jie Yang, Takashi Taniguchi, Kenji Watanabe, Feng Wang, Xijie Wang, Jeffrey B. Neaton, Tony F. Heinz, Aaron M. Lindenberg, Felipe H. da Jornada, Archana Raja
Summary: In this study, lattice dynamics in photoexcited WSe2/WS2 heterostructures were directly visualized using femtosecond electron diffraction. It was found that both WSe2 and WS2 were heated simultaneously on a picosecond timescale, which cannot be explained by phonon transport across the interface. First-principles calculations revealed a fast channel involving layer-hybridized electronic states, enabling phonon-assisted interlayer transfer of photoexcited electrons. Phonons were emitted in both layers on the femtosecond timescale via this channel, consistent with the simultaneous lattice heating observed experimentally. Strong electron-phonon coupling via layer-hybridized electronic states was identified as a novel route for controlling energy transport across atomic junctions.
NATURE NANOTECHNOLOGY
(2023)
Article
Chemistry, Multidisciplinary
Liang Chen, Qi Wang, Yansong Si, Yu Hou
Summary: In this work, a heat sink combining the confined jet impingement with metallic phase change material (PCM) is proposed for the thermal management of millisecond-pulsed heat sources. The heat transfer characteristics of the heat sink and the temperature responses under millisecond heat pulses are analyzed. Results show that the jet impingement with specific parameters can achieve effective cooling, and an appropriate PCM thickness is required for stable phase change cycling.
APPLIED SCIENCES-BASEL
(2023)
Article
Thermodynamics
Kaimiao Zhou, Liang Chen, Shanfeng Li, Kang Zhao, Ze Zhang, Shuangtao Chen, Yu Hou
Summary: Liquid hydrogen is crucial for large-scale hydrogen energy development, and the Claude cycle is commonly used for hydrogen liquefaction. The hydrogen turbo-expander plays an important role in determining the efficiency and reliability of the system. This study uses mean-line design and loss models to develop a hydrogen turbo-expander, and CFD simulations are used to analyze the flow field and loss mechanisms. The results show that the hydrogen turbo-expander has higher passage efficiency compared to the helium expander due to its lower viscosity and smaller losses.
APPLIED THERMAL ENGINEERING
(2023)
Article
Thermodynamics
Runfeng Xiao, Pingtao Zhang, Liang Chen, Yu Hou
Summary: The heat transfer deterioration (HTD) of supercritical fluids is crucial for the safe operation of power systems. Current criteria for HTD face difficulties in identifying the working conditions of supercritical fluids. This paper proposes a new definition of HTD and a machine learning-based method to predict HTD in upward vertical tubes with supercritical water and CO2. Eight criteria for HTD were compared and analyzed based on two traditional definitions and the proposed new one. Results showed that the discontinuity of experimental data leads to missing HTD points. Traditional methods achieved accuracy ranging from 55% to 82%. The machine learning-based method demonstrated high prediction accuracy of up to 95% for all three definitions of HTD. The proposed definition and the machine learning method can improve the identification and prediction of HTD in supercritical fluids.
APPLIED THERMAL ENGINEERING
(2023)
Review
Thermodynamics
Xiaoling Yang, Rong Xue, Ning Wang, Zhilong Huang, Haiyang Zhang, Xiufang Liu, Liang Chen, Yu Hou
Summary: Spray cooling with liquid nitrogen has advantages for achieving cryogenic temperature, and the process can be divided into three stages: cavitating flow, spray breakup, and cooling process. This paper summarizes published literatures on these stages. A brief review shows that the correlation between thermodynamic parameters and spray cooling characteristics is not fully understood. Future research should focus on gaining a deeper insight into heat transfer mechanisms and enhancing the application of cryogenic spray.
Article
Thermodynamics
Yang Meng, Yicheng Zhang, Junxin Wang, Shuangtao Chen, Yu Hou, Liang Chen
Summary: This paper proposes a reverse-bootstrap turboexpander-compressor (TEC) scheme for the direct recovery of expansion work into the cooling capacity of small air-separation plants. A mathematical model is established for the codesign and off-design analysis of TEC, which is validated by experimental data. The use of a reverse-bootstrap compressor in the original turboexpander can increase the isentropic coefficient by 12%. The codesign of the turboexpander and the coaxial compressor can further increase the isentropic coefficient by 7.1% under design condition, resulting in an 8.1% improvement in cooling power and a 1.7% reduction in required heating power. The results demonstrate that the proposed reverse-bootstrap TEC with the codesign method is an effective way for energy recovery in small refrigeration systems.
Article
Thermodynamics
Shujian Song, Shuangtao Chen, Xiaocong Zhou, Yihang Zhu, Xihan Zhang, Liang Chen, Yu Hou
Summary: This paper investigates the operating characteristics of a closed-cycle single-stage turbo-refrigerator with a motor-driven turboexpander compressor (MTEC). Test results show that variable-speed operation allows for independent control of the refrigeration temperature and cooling capacity. Advanced exergy analysis suggests that with future component improvement, a higher total exergy efficiency can be expected.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2023)