Characterization of the Heat Transfer Accompanying Electrowetting-Induced Droplet Motion

Electrowetting (EW) involves the actuation of liquid droplets using electric fields and has been demon- strated as a powerful tool for initiating and controlling droplet-based microfluidic operations such as droplet transport, generation, splitting, merging and mixing. The heat transfer resulting from EW- induced droplet actuation has, however, remained largely unexplored owing to several challenges under- lying even simple thermal analyses and experiments. In the present work, the heat dissipation capacity of actuated droplets is quantified through detailed modeling and experimental efforts. The modeling involves three-dimensional transient numerical simulations of a droplet moving under the action of grav- ity or EW on a single heated plate and between two parallel plates. Temperature profiles and heat trans- fer coefficients associated with the droplet motion are determined. The influence of droplet velocity and geometry on the heat transfer coefficients is parametrically analyzed. Convection patterns in the fluid are found to strongly influence thermal transport and the heat dissipation capacity of droplet-based systems. The numerical model is validated against experimental measurements of the heat dissipation capacity of a droplet sliding on an inclined hot surface. Infrared thermography is employed to measure the transient temperature distribution on the surface during droplet motion. The results provide the first in-depth analysis of the heat dissipation capacity of electrowetting-based cooling systems and form the basis for the design of novel microelectronics cooling and other heat transfer applications

Electronics Thermal Management in Information and Communications Technologies: Challenges and Future Directions

This paper reviews thermal management challenges encountered in a wide range of electronics cooling applications from large-scale (data center and telecommunication) to smallscale systems (personal, portable/wearable, and automotive). This paper identifies drivers for progress and immediate and future challenges based on discussions at the 3rd Workshop on Thermal Management in Telecommunication Systems and Data Centers held in Redwood City, CA, USA, on November 4–5, 2015. Participants in this workshop represented industry and academia, with backgrounds ranging from data center thermal management and energy efficiency to high-performance computing and liquid cooling, thermal management in wearable and mobile devices, and acoustic noise management. By considering a wide range of electronics cooling applications with different lengths and time scales, this paper identifies both common themes and diverging views in the thermal management community

Convection heat transfer in electrostatic actuated liquid droplets for electronics cooling

In this paper, the internal flow and heat transfer inside the electrostatic actuated droplets are studied for different droplet velocities by means of detailed flow computations. It is shown that the internal droplet flow exhibits a parabolic characteristic at one hand and that the presence of two convection cells decreases the heat transfer to the lower part of the droplet, thereby limiting the overall heat transfer through the droplet. A typical enhancement of the heat transfer with a factor 2 is achieved with respect to the minimal value that would be obtained assuming heat conduction as the only means of heat transfer in the liquid. Further an analytic lumped model is presented to estimate the transient average droplet temperature with an accuracy of 5% compared to the full transient computational fluid dynamics modelling.status: publishe