A supercooled liquid droplet that freezes on a cold substrate interacts with the local surroundings through heat and mass exchange. Heat loss occurs to the substrate via conduction and at the droplet interface via evaporative cooling, diffusion, and convection. In a group of many droplets, these interactions are believed to be responsible for inter-droplet frost propagation and the evaporation of supercooled neighboring droplets. Furthermore, interactions between a standalone freezing droplet and its surroundings can lead to the formation of condensation halos and asymmetric solidification induced by external flows. This paper investigates droplet-to-droplet interactions via heat and mass exchange between a freezing droplet and a neighboring droplet, for which asymmetries are observed in the final shape of the frozen droplet. Side-view infrared (IR) thermography measurements of the surface temperature for a pair of freezing droplets, along with three-dimensional numerical simulations of the solidification process, are used to quantify the intensity and nature of these interactions. Two droplet-to-droplet interaction mechanisms causing asymmetric freezing are identified: (1) non-uniform evaporative cooling on the surface of the freezing droplet caused by vapor starvation in the air between the droplets; and (2) a non-uniform thermal resistance at the contact area of the freezing droplet caused by the heat conduction within the neighboring droplet. The combined experimental and numerical results show that the size of the freezing droplet relative to its neighbor can significantly impact the intensity of the interaction between the droplets and, therefore, the degree of asymmetry. A small droplet freezing in the presence of a large droplet, which blocks vapor from freely diffusing to the surface of the small droplet, causes substantial asymmetry in the solidification process. The droplet-to-droplet interactions investigated in this paper provide insights into the role of latent heat dissipation during condensation frosting.

冻结在冷基板上的过冷液滴通过热量和质量交换与局部环境相互作用。热损失通过传导作用发生在基板上，而通过蒸发冷却，扩散和对流发生在液滴界面处。在许多小滴的组中，这些相互作用被认为是小滴间霜冻传播和过冷相邻小滴蒸发的原因。此外，独立的冷冻液滴与其周围环境之间的相互作用可能导致凝结光晕的形成以及外部流动引起的不对称凝固。本文研究了冷冻液滴与相邻液滴之间通过热量和质量交换进行的液滴间相互作用，在冷冻液滴的最终形状中观察到了不对称性。一对冷冻液滴的表面温度的侧面红外（IR）热像仪测量以及凝固过程的三维数值模拟，用于量化这些相互作用的强度和性质。确定了导致不对称冻结的两种液滴间相互作用的机制：（1）由于液滴之间空气中的蒸汽不足而导致的冻结液滴表面上的蒸发蒸发不均匀；（2）由相邻液滴内的热传导引起的在冻结液滴的接触区域处的不均匀的热阻。组合的实验和数值结果表明，冷冻液滴相对于其相邻液滴的大小会显着影响液滴之间相互作用的强度，因此，不对称程度。在大液滴的存在下冻结的小液滴会阻止蒸汽自由扩散到小液滴的表面，这会导致凝固过程中的不对称性。本文研究的液滴之间的相互作用为凝结结霜期间潜热耗散的作用提供了见解。