This article surveys the mathematical principles essential for understanding the thermal management of Li-ion batteries, the current technological state of the art, and the solution. Since the ...thermal management of electric drive vehicles has environmental, economic, and safety impacts, this review focuses on the efficient methods of battery thermal management (BTM) that were proposed to overcome the major challenges in the electric vehicle industry. The first section examines the perspective of battery-driven vehicles, the principles of Li-ion batteries with a thermal runaway, and their implication for battery safety. The second section discusses mathematical approaches for effective BTM modeling, including the thermal-fluidic network model, lumped capacitance model, spatial resolution lumped capacitance model, equivalent circuit model, impedance-based model, and data-driven model. The third section presents the current state-of-the-art technologies, including air-based, liquid-based, PCM-based, in situ BTM methods, and heat pipe and thermoelectric module-based methods. The conclusion section summarizes the findings from existing research and the possible future directions to achieve and employ better thermal management techniques.
Surface tension of pure fluids, inherently decreasing with regard to temperature, creates a thermo-capillary-driven (Marangoni) flow moving away from a hot surface. It has been known that few ...high-carbon alcohol-aqueous solutions exhibit an opposite behavior of the surface tension increasing with regard to temperature, such that the Marangoni flow moves towards the hot surface (self-rewetting effect). We report the surface tensions of three dilute aqueous solutions of n-Butanol, n-Pentanol and n-Hexanol as self-rewetting fluids measured for ranges of alcohol concentration (within solubility limits) and fluid temperatures (25–85 °C). A maximum bubble pressure method using a leak-tight setup was used to measure the surface tension without evaporation losses of volatile components. It was found from this study that the aqueous solutions with higher-carbon alcohols exhibit a weak self-rewetting behavior, such that the surface tensions remain constant or slightly increases above about 60 °C. These results greatly differ from the previously reported results showing a strong self-rewetting behavior, which is attributed to the measurement errors associated with the evaporation losses of test fluids during open-system experiments.
► A reciprocating air flow was used for Li-ion battery thermal management. ► 2-D CFD and lumped-capacitance thermal models were used for numerical analysis. ► The reciprocating flow cases were ...compared with the unidirectional flow case. ► The reciprocating flow greatly improves temperature uniformity between cells. ► The reciprocating flow also reduces the maximum cell temperature.
The thermal management of traction battery systems for electrical-drive vehicles directly affects vehicle dynamic performance, long-term durability and cost of the battery systems. In this paper, a new battery thermal management method using a reciprocating air flow for cylindrical Li-ion (LiMn
2O
4/C) cells was numerically analyzed using (i) a two-dimensional computational fluid dynamics (CFD) model and (ii) a lumped-capacitance thermal model for battery cells and a flow network model. The battery heat generation was approximated by uniform volumetric joule and reversible (entropic) losses. The results of the CFD model were validated with the experimental results of in-line tube-bank systems which approximates the battery cell arrangement considered for this study. The numerical results showed that the reciprocating flow can reduce the cell temperature difference of the battery system by about 4
°C (72% reduction) and the maximum cell temperature by 1.5
°C for a reciprocation period of
τ
=
120
s as compared with the uni-directional flow case (
τ
=
∞). Such temperature improvement attributes to the heat redistribution and disturbance of the boundary layers on the formed on the cells due to the periodic flow reversal.
By using hard X‐ray photoelectron spectroscopy experimentally, proof is provided that resistive switching in Ti/Pr0.48Ca0.52MnO3 (PCMO) devices is based on a redox‐process that mainly occurs on the ...Ti‐side. The different resistance states are determined by the amount of fully oxidized Ti‐ions in the stack, implying a reversible redox‐reaction at the interface, which governs the formation and shortening of an insulating tunnel barrier.
An experimental study was conducted to investigate the effects of solution subcooling and wall superheat on both sensible and evaporative heat transfer in a falling-film heat exchanger using both ...plain and porous-layer coated tubes. By varying the subcooling and wall superheat, it was seen that the portions of sensible and evaporative heat transfers could be controlled. Since the falling-film heat exchanger is limited by the coupled relationship between flooding of the upstream tubes and partial dry-out of the bottommost tubes, the ability to control this evaporation-to-sensible heat transfer ratio is important in system optimization. It was shown that sensible heat transfer can be promoted for the upstream tubes while evaporation heat transfer can be promoted for the downstream tubes. Since sensible heat transfer is enhanced by higher solution Reynolds number and therefore larger film thickness, flooding of the upstream tube rows is no longer detrimental.
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•Binder-free flexible carbon nanofibers are decorated with dodecahedral ZIF-67 of various morphologies.•The ZIF-67 morphology is varied by varying the polyvinylpyrrolidone (PVP) ...concentration.•The optimal sample yields a capacitance of 444 mF⋅cm−2 at a current rate of 5 mA⋅cm−2.•A specific capacitance retention of 94% after 30,000 cycles is recorded for the optimal sample.
Binder-free, highly flexible carbon nanofibers decorated with ZIF-67 dodecahedral structures are synthesized via electrospinning and impregnation for use in supercapacitor applications. Because cobalt ions from ZIF-67 are highly attracted to carbon rings and the oxygen functional groups of polyvinylpyrrolidone (PVP), the concentration of PVP is varied to tune the morphology of ZIF-67. Accordingly, morphology tuning via PVP inclusion enhances the electron transfer within the ZIF-67-derived CoOx dodecahedral structure. Parametric studies are conducted to investigate the effect of PVP concentration on the electrochemical performance of carbon nanofibers decorated with ZIF-67. The optimal sample yields a capacitance of 444 mF⋅cm−2 at a current rate of 5 mA⋅cm−2. The corresponding capacitance retention is 94 % after 30,000 cycles with a potential window of 1 V. Furthermore, the energy density increases by 262.7 % when the potential window is increased from 1 to 1.5 V. These results confirm the long-term stability and outstanding energy-storage capabilities of the fabricated supercapacitor electrodes.
The miniaturization of electronic devices with ever-increasing functionalities inevitably results in greater thermal load on the devices. Hence, pool boiling, which utilizes the powerful latent heat ...of vaporization, is introduced as an effective method to manage severe thermal loads on miniaturized electronics. Hydrophobic surfaces tend to augment sufficient nucleation sites via roughening or low surface energy, while hydrophilic surfaces are prone to ample liquid supply, thus facilitating rapid bubble release and preventing surface dry-out. Herein, we compared the heat removal performance of TiO2-coated superhydrophilic and Teflon-coated superhydrophobic surfaces fabricated by aerosol deposition and supersonic spraying, respectively. TiO2 and Teflon particles were deposited on evenly patterned frustums. The resolution of the frustum is categorized as no-frustum, coarse, medium, or fine. We found that the surface wettability had little effect on the critical heat flux (CHF) for the no-frustum and fine cases. However, the CHF and effective heat transfer coefficient (heff) of the superhydrophilic surface increased considerably in the medium case. For the superhydrophobic surface, the presence of frustum deteriorated the pool boiling performance. Frustum texturing enhanced the pool boiling performance by increasing the number of nucleation sites and pathways of fresh liquid supply for the bare and superhydrophilic surfaces, but not for the superhydrophobic surface.
Many deformations occur in old RC structures, and the method of reinforcing them using PC members standardized and manufactured in the same mold has difficulty in coping with all deformations ...(construction error); as a solution to this, overlapping anchor shear connections consisting of three concrete segments have been proposed. This study proposes a special connection for strengthening existing reinforced concrete (RC) framed structures that are more than 30 years old with precast concrete (PC) members. The proposed overlapped anchor connection consists of two anchor groups installed in three concrete segments, which can accommodate deformation by adjusting the height of the concrete connection segment. In this study, the unique shear behavior of the overlapped anchor connection was investigated by analyzing the shear resistance of the single-anchor connection with one post-installed anchor and one cast-in anchor. Eleven specimens of anchored connection models were constructed and push-out tested, and the experimental parameters were analyzed. The shear strength of the single-anchor connection was calculated using a proposed design formula based on the American anchor design code, and the shear strength ratios of the experimental shear strengths to the calculated values were 0.93 on average. The proposed design formula can predict the shear behavior and expected effects of the proposed connection even in differing designs.
•System-level analysis of flow boiling in a pumped two-phase loop.•Transient responses explained dryout propagation mechanism in microchannels.•More heat is dissipated as the mass flux increases for ...the same wall temperature.•Increase in charge ratio increased the degree of subcooling.•An early transition to an annular flow regime was observed for high mass fluxes.
High-power electronics exceed the heat dissipation capability of conventional air or liquid-based forced convection cooling systems. A pumped two-phase loop (P2PL) utilizing phase change heat transfer can effectively transport and dissipate high heat fluxes generated from the electronics at very small thermal resistance while consuming negligible pumping power. Existing research primarily focuses on standalone evaporators with fixed boundary conditions, neglecting the interactions between the evaporator and other components within the P2PL. This knowledge gap hinders the comprehensive understanding of system performance. To address this need, an experimental study was conducted to examine subcooled flow boiling in a microchannel evaporator of P2PL using R-134a. The parameters used for the investigation are evaporator heat input, mass flux, chiller loop inlet temperature, and fluid charge ratio. Additionally, flow visualization through a sight glass tube at the evaporator outlet was used to identify the two-phase flow regimes, namely – the onset of nucleate boiling, bubbly, slug, stratified, annular, and mist flow. The dominant flow boiling mechanisms and its transitions in the microchannel were identified based on the varying slopes of the boiling curves. The dynamic responses were additionally utilized to differentiate between single-phase and two-phase flows as well as to identify the propagation of dryout in the microchannel evaporator. The study further revealed that for a constant wall superheat, within the convective boiling dominant regime, the heat transfer rate in the evaporator exhibits an increase with the mass flow rate. In contrast, in the nucleate boiling dominant regime, the heat transfer rate remains unaffected by the mass flow rate. Furthermore, it was found that as the fluid charge ratio increases, the heat transfer coefficient and pressure drop in the evaporator decreases.
Background Oligomeric amyloid beta (oAβ) is a toxic factor that acts in the early stage of Alzheimer’s disease (AD) and may initiate the pathologic cascade. Therefore, detecting oAβ has a crucial ...role in the early diagnosis, monitoring, and treatment of AD. Purpose The purpose of this study was to evaluate MRI signal changes in different mouse models and the time-dependent signal changes using our novel gadolinium (Gd)-dodecane tetraacetic acid (DOTA)- ob5 aptamer contrast agent. Methods We developed an MRI contrast agent by conjugating Gd-DOTA-DNA aptamer called ob5 to evaluate its ability to detect oAβ deposits in the brain using MRI. A total of 10 control mice, 9 3xTg AD mice, and 11 APP/PS/Tau AD mice were included in this study, with the age of each model being 16 or 36 weeks. A T1-weighted image was acquired at the time points before (0 min) and after injection of the contrast agent at 5, 10, 15, 20, and 25 min. The analyses were performed to compare MRI signal differences among the three groups and the time-dependent signal differences in different mouse models. Results Both 3xTg AD and APP/PS/Tau AD mouse models had higher signal enhancement than control mice at all scan-time points after injection of our contrast media, especially in bilateral hippocampal areas. In particular, all Tg AD mouse models aged 16 weeks showed a higher contrast enhancement than those aged 36 weeks. For 3xTg AD and APP/PS/Tau AD groups, the signal enhancement was significantly different among the five time points (0 min, 5 min, 10 min, 15 min, 20 min, and 25 min) in multiple ROI areas, typically in the bilateral hippocampus, left thalamus, and left amygdala. Conclusion The findings of this study suggest that the expression of the contrast agent in different AD models demonstrates its translational flexibility across different species. The signal enhancement peaked around 15–20 min after injection of the contrast agent. Therefore, our novel contrast agent targeting oAβ has the potential ability to diagnose early AD and monitor the progression of AD.
