Capillary-driven flow in complex microfluidic devices is increasingly encountered in life science applications, and powerful modeling tools are necessary to assist the design of these devices. In this work, we present a modeling framework for capillary-driven flow in closed complex microfluidic networks using electric circuit analogy. The model handles two immiscible fluid phases, including the capillary pressure jump across the interface(s) between the phases, in a large variety of fluidic structures. As outputs, the position and velocity of each interface in the analyzed microfluidic network are provided as a function of time. Single channels, successive channels of different dimensions, tapered channels, micropillar arrays, flow splitters, mixing of two liquids, and the presence of vents can be modeled and combined in different complex structures. Static and dynamic contact angles can be employed. Advancing and receding interfaces can both be modeled. The model was validated against both experimental and analytical results for specific microfluidic structures. Furthermore, the capabilities of the model are demonstrated using a complex microfluidic network.
7 Abstract The objective of this work is to achieve a 8 rigorous resolution of the coupled hydraulic and thermal 9 problems (including the solid) within a single triangular 10 axial groove of a heat pipe in microgravity conditions. 11 This is done by modeling the phenomena of transport of 12 matter, momentum and heat, starting from the equations 13 of continuity, Navier-Stokes and energy conservation. By 14 combining the lubrication approximation and the one-15 sided approach, our approach leads to a 2nd-order dif-16 ferential equation for the scaled height of liquid. Through 17 solving numerically this equation for a given heat flux 18 input distribution, we can establish the profiles along the 19 heat pipe for the scaled height of liquid and for the scaled 20 averaged axial velocity of the flow. The equation of 21 energy conservation can then also be solved, for the scaled 22 liquid height distribution just determined. It leads to the 23 scaled temperature field in each section of the heat pipe, 24 and hence to the 3D temperature field, both in the solid 25 and in the liquid. The proposed approach also enables 26 determining the maximum heat flux that can be applied in 27 the evaporator section without reaching dryout. Finally, 28 the parametric sensitivity of this maximum heat flux to 29 both geometrical and thermodynamical parameters is also 30 analyzed. 31
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