Interfacial temperature measurements,high-speed visualization and finite-element simulations of droplet impact and evaporation on a solid surface |
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Authors: | Rajneesh Bhardwaj Jon P. Longtin Daniel Attinger |
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Affiliation: | 1. Université de Bordeaux, I2M-Département TREFLE UMR CNRS 5295, 16 avenue Pey-Berland, F-33607 Pessac, France;2. CEA DAM, Le Ripault, F-37260 Monts, France;1. School of Energy and Power Engineering, Chongqing University, Chongqing 400044, China;2. Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing 400044, China;1. Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University, Chongqing 400044, China;2. School of Energy and Power Engineering, Chongqing University, Chongqing 400044, China;3. College of Environmental Science and Engineering, Guilin University of Technology, Guilin 541006, Guangxi, China |
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Abstract: | The objective of this work is to investigate the coupling of fluid dynamics, heat transfer and mass transfer during the impact and evaporation of droplets on a heated solid substrate. A laser-based thermoreflectance method is used to measure the temperature at the solid–liquid interface, with a time and space resolution of 100 μs and 20 μm, respectively. Isopropanol droplets with micro- and nanoliter volumes are considered. A finite-element model is used to simulate the transient fluid dynamics and heat transfer during the droplet deposition process, considering the dynamics of wetting as well as Laplace and Marangoni stresses on the liquid–gas boundary. For cases involving evaporation, the diffusion of vapor in the atmosphere is solved numerically, providing an exact boundary condition for the evaporative flux at the droplet–air interface. High-speed visualizations are performed to provide matching parameters for the wetting model used in the simulations. Numerical and experimental results are compared for the transient heat transfer and the fluid dynamics involved during the droplet deposition. Our results describe and explain temperature oscillations at the drop–substrate interface during the early stages of impact. For the first time, a full simulation of the impact and subsequent evaporation of a drop on a heated surface is performed, and excellent agreement is found with the experimental results. Our results also shed light on the influence of wetting on the heat transfer during evaporation. |
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