Boundary layer stagnation-point flow and heat transfer over an exponentially stretching/shrinking sheet in a nanofluid

Multiphase flow in porous media is relevant to amount of engineering processes, such as hydrocarbon extraction from reservoir rock, water contamination, CO2 geological storage and sequestration. Pore scale modeling, as an alternative approach to lab measurement, firstly serves as an effective bridge to link the pore scale properties (pore geometry and wettability) and displacement mechanisms to continuous scale multiphase flow in porous media; and secondly allows us to determine essential flow functions, such as capillary pressure and relative permeability curves, which are required for continuous scale modeling. In the literature, three methodologies, Bundle of Capillary Tube Modeling (BCTM), Direct Pore Scale Modeling (DPSM) and Pore Network Modeling (PNM), have appeared to be mostly widely adopted in the investigation of the pore-scale mechanics of fluid-fluid and fluid-solid interactions in porous media by numerical simulation. In this review article, a comprehensive review is provided to show their strengths and weaknesses and to highlight challenges that are faced in modelling of multiphase flow, key challenges include: are contact angle characterization, validation and upscale pore scale findings to core, or even field scale.

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A comprehensive review of pore scale modeling methodologies for multiphase flow in porous media

Fractal model provides an alternative and useful means for studying the transport phenomenon in porous media and analyzing the macroscopic transport properties of porous media, as fractal geometry can successfully characterize disordered and heterogeneous geometrical microstructures of porous media on multi scales. Recently, fractal models on porous media have attracted increasing interests from many different disciplines. In this mini-review paper, a review on fractal models for number-size distribution in porous media is made, and a unified fractal model to characterize pore and particle size distributions is proposed according to the statistical fractal property of the complex microstructure in porous media. Using the fractal scaling laws for pore and fracture size distributions, a fractal capillary bundle model and a fractal tree-like network model are presented and summarized for homogenous and fractured porous media, respectively. And the applications of the fractal capillary bundle model and fractal tree-like network model for analysis of transport physics in porous media are also reviewed.

A discussion on fractal models for transport physics of porous media

An improved model for permeability estimation in low permeable porous media based on fractal geometry and modified Hagen-Poiseuille flow

Longitudinal and radial permeability analysis of additively manufactured porous scaffolds: Effect of pore shape and porosity

Radial permeability of fractured porous media by Monte Carlo simulations

A study on the heat and mass transfer properties of multiple pulsating impinging jets

A numerical study is performed on a two-dimensional confined opposed-jet configuration to gain basic understanding of the flow and mixing characteristics of pulsed turbulent opposed-jet streams. The sinusoidal pulsating flows with different temperature are imposed at opposed-jet inlets, which are mixed with each other in a confined flow channel. The current mathematical model taking the effect of temperature-dependent thermo-physical properties of fluid into account can present a good prediction for opposed-jet streams compared with experimental data. The numerical results indicate that introduction of temperature difference between opposed jet flows can lead to an asymmetric flow field immediately after jet impact, and the sinusoidal flow pulsations can effectively enhance mixing rate of opposed jets. Parameter studies are conducted for optimization of pulsed opposed jets. The effect of Reynolds number and flow pulsation as well as the configuration geometry on the mixing performance are discussed in detail. Examination of the flow and thermal field shows that the mixing rate is highly dependent on the vortex-induced mixing and residence time of jet fluid in the exit channel.

Flow and mixing characteristics of pulsed confined opposed jets in turbulent flow regime

The invention relates to a cooling device of an electron device, in particular to a pulse jet flow finned cooling device which is a high-efficiency cooling device with a pulse jet flow cooling technology and a finned radiator combined. The pulse jet flow finned cooling device mainly comprises a pulsating flow generating device, a jet flow matrix and the finned radiator. The pulse jet flow finned cooling device is characterized in that an electronic signal drives an acoustic excitation device to generate an unsteady pulsating flow which is jetted onto the finned radiator through the pulse jet flow matrix. Due to the fact that cooling media directly impact the finned surface, and a heat transfer process is strengthened through the unsteady pulsating flow, cooling efficiency is improved, energy consumption is reduced, the electronic device with high heat flux density can be effectively and fast cooled, and jet flow parameters can be set according to requirements to adapt working condition changes.

Pulse jet flow finned cooling device

The utility model relates to a cooling apparatus, in particular to a fractal fin radiator, which is used for a square electronic equipment cooling system and is high in efficiency and uniform in temperature. In the process of use, the fin radiator is designed to be H-shaped to form a fractal furcation network structure, the fractal fin radiator, an insulating pad and an electronic chip are entirely packaged, and fins with a rectangular cross section are easy in processing and mounting and are suitable for batch production. The fractal fin radiator can fully utilize the surface space of the electronic chip, enables the heat exchange surface area of the fins to be increased, and reduces airflow by-pass capacity among the fins, thereby increasing the heat radiation efficiency; the fractal fin radiator is especially suitable for the design of a square chip heat radiation system; and simultaneously, the fractal fins have excellent space distribution uniform characteristics, thereby effectively reducing the temperature distribution nonuniformity of the chip, eliminating the local heat spots of the surface of the chip, preventing the chip from being damaged, and effectively prolonging the service life of the chip.

Qiao Xianwu

Papers

Radial permeability of fractured porous media by Monte Carlo simulations

A study on the heat and mass transfer properties of multiple pulsating impinging jets

Flow and mixing characteristics of pulsed confined opposed jets in turbulent flow regime

Pulse jet flow finned cooling device

Fractal fin radiator