Study on Flow Characteristics of Working Medium in Microchannel Simulated by Porous Media Model

Abstract

As a phase change evaporator, a microchannel array heat exchanger is of great significance in the field of microscale heat dissipation. The performance of which strongly depends on the flow resistance, capillary force, and other factors. In order to improve the heat dissipation efficiency, it is necessary to perform an in-depth study of the characteristics of microchannel flow using numerical simulation. However, the current simulation model requires high computational cost and long simulation time. To solve this problem, this paper simplifies the numerical simulation of the rectangular parallel array microchannels by building the basic flow model based on the concept of porous media. In addition, we explore the effect of aspect-ratio (AR), hydraulic diameter, inlet velocity, and other parameters of fluid flow behavior inside the microchannels. Meanwhile, a user-defined function (UDF) is formulated to add the capillary force into the model to introduce capillary force into the porous media model. Through the above research, the paper establishes the porous media model for single-phase and gas-liquid two-phase flow, which acts as a simplification of microchannel array simulation without grossly affecting the results obtained. In addition, we designed and manufactured experiments using silicon-based microchannel heat exchangers with different-ratios, and combined with the visualization method to measure the performance of the device and compared them with simulation results. The theoretical model is verified through the suction experiment of array microchannel evaporator capillary core. The simplified model of microchannel array significantly saves the computational cost and time, and provides guidance for the related experimental researches.

Parametrical Study on the Capillary Flowing Characteristics of the Parallel Microchannel Array

“…We developed a two-phase transient microchannel 3D-model by the CFD-FVM software, ANSYS Fluent [26], to explore the microchannel geometric structure for optimal capillary pumping performance. Our model considered the microchannels with the same feature as in the experiments to perform numerical simulations of capillary flow.…”

“…A single momentum equation is solved throughout the domain, and the resulting velocity field is shared among the phases. The momentum equation, shown below, is dependent on the volume fractions of all phases through the properties ρ and µ [26].…”

“…Volume fraction equation of VOF model [26]: If the volume fraction of the k phase fluid is set to α k , then the relationship between the VOF equation of the k phase and each volume fraction α k is:…”

Visualization Experimental Study on Silicon-Based Ultra-Thin Loop Heat Pipe Using Deionized Water as Working Fluid

“…It also clarified the optimal charging rate of the two working fluids, evaluated their thermal resistances, identified their key mechanisms of circulating motion, and observed two different flow modes (oscillatory eruption mode and circulating mode). Our research group performed an in-depth study of the characteristics of microchannel flow using numerical simulation [15]. On the basis of our previous research and the four types of research listed above, we conducted in-depth research focusing on visualization and expanded the literature on the design of microchannels and the performance of heat pipes.…”

Editorial for the Special Issue on Micro-Manufacturing and Applications

“…Nowadays, with the rapid development of the electronic industry, it is becoming increasingly important that the removal of heath from electronic components is fast and effective. For that purpose, micro channels in porous media were investigated [ 3 ], concluding with a more effective, two-phase heath exchanging opportunity. The wire EDM process was employed for machining thin fins [ 4 ], which can be used for many purposes, one being to serve as heath exchanges and/or micro-fluidic systems.…”