Carman Fionn, Ewen James P, Bresme Fernando, Wu Billy, Dini Daniele
Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, U.K.
Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, U.K.
ACS Appl Mater Interfaces. 2024 Oct 30;16(43):59452-59467. doi: 10.1021/acsami.4c09434. Epub 2024 Oct 15.
The rational design of dielectric fluids for immersion cooling of batteries requires a molecular-level understanding of the heat flow across the battery casing/dielectric fluid interface. Here, we use nonequilibrium molecular dynamics (NEMD) simulations to quantify the interfacial thermal resistance (ITR) between hematite and poly-α-olefin (PAO), which are representative of the outer surface of the steel battery casing and a synthetic hydrocarbon dielectric fluid, respectively. After identifying the most suitable force fields to model the thermal properties of the individual components, we then compared different solid-liquid interaction potentials for the calculation of the ITR. These potentials resulted in a wide range of ITR values (4-21 K m GW), with stronger solid-liquid interactions leading to lower ITR. The increase in ITR is correlated with an increase in density of the fluid layer closest to the surface. Since the ITR has not been experimentally measured for the hematite/PAO interface, we validate the solid-liquid interaction potential using the work of adhesion calculated using the dry-surface method. The work of adhesion calculations from the simulations were compared to those derived from experimental contact angle measurements for PAO on steel. We find that all of the solid-liquid potentials overestimate the experimental work of adhesion. The experiments and simulations can only be reconciled by further reducing the strength of the interfacial interactions. This suggests some screening of the solid-liquid interactions, which may be due to the presence of an interfacial water layer between PAO and steel in the contact angle experiments. Using the solid-liquid interaction potential that reproduces the experimental work of adhesion, we obtain a higher ITR (33 K m GW), suggesting inefficient thermal transport. The results of this study demonstrate the potential for NEMD simulations to improve understanding of the nanoscale thermal transport across industrially important interfaces. This study represents an important step toward the rational design of more effective fluids for immersion cooling systems for electric vehicles and other applications where thermal management is of high importance.
用于电池浸没冷却的介电流体的合理设计需要从分子层面理解热量穿过电池外壳/介电流体界面的流动情况。在此，我们使用非平衡分子动力学（NEMD）模拟来量化赤铁矿与聚α-烯烃（PAO）之间的界面热阻（ITR），它们分别代表钢质电池外壳的外表面和合成烃介电流体。在确定了用于模拟各组分热性质的最合适力场后，我们接着比较了不同的固液相互作用势来计算ITR。这些势导致了ITR值的广泛范围（4 - 21 K m² GW⁻¹），固液相互作用越强，ITR越低。ITR的增加与最靠近表面的流体层密度的增加相关。由于尚未对赤铁矿/PAO界面进行ITR的实验测量，我们使用通过干表面法计算的粘附功来验证固液相互作用势。将模拟得到的粘附功计算结果与从PAO在钢上的实验接触角测量得出的结果进行比较。我们发现所有的固液势都高估了实验粘附功。只有进一步降低界面相互作用的强度，实验和模拟结果才能相互吻合。这表明需要对固液相互作用进行某种筛选，这可能是由于在接触角实验中PAO与钢之间存在界面水层。使用能再现实验粘附功的固液相互作用势，我们得到了更高的ITR（33 K m² GW⁻¹），表明热传输效率低下。本研究结果证明了NEMD模拟在增进对工业上重要界面的纳米级热传输理解方面的潜力。这项研究是朝着合理设计用于电动汽车及其他热管理至关重要的应用的浸没冷却系统的更有效流体迈出的重要一步。
