Numerical investigation of conjugated heat transfer in a channel with a moving depositing front

This article presents numerical simulations of conjugated heat transfer in a fouled channel with a moving depositing front. The depositing front separating the fluid and the deposit layer is captured using the level-set method. Fluid flow is modeled by the incompressible Navier–Stokes equations. Numerical solution is performed on a fixed mesh using the finite volume method. The effects of Reynolds number and thermal conductivity ratio between the deposit layer and the fluid on local Nusselt number as well as length-averaged Nusselt number are investigated. It is found that heat transfer performance, represented by the local and length-averaged Nusselt number reduces significantly in a fouled channel compared with that in a clean channel. Heat transfer performance decreases with the growth of the deposit layer. Increases in Reynolds, Prandtl numbers both enhance heat transfer. Besides, heat transfer is enhanced when the thermal conductivity ratio between the deposit layer and the fluid is lower than 20 but it decreases when the thermal conductivity ratio is larger than 2

Experimental investigation of Asphaltene deposition in a transparent mini-channel

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.One of the most recurring flow assurance problems in oil and gas industry is associated to the formation of organic and inorganic deposits in the wellbores and the near-wellbore regions. In particular, the depositions of asphaltene in wellbores represent both a major obstacle for petroleum engineers and a challenging topic for scientists. This paper focuses on experimental investigation of asphaltene deposition in transparent mini-channel. The working fluid is a mixture of heptane and crude oil. Induced by the addition of n-heptane, the dissolved asphaltene in crude oil precipitates to form asphaltene particles which deposit on the walls of the transparent mini-channel at ambient temperature. The thickness of asphaltene deposition is estimated using a visualization technique based on 3D microscopy. The thickness of the deposition layer is quantified and the two-dimensional profile of the deposition at selected axial section is measured. The obtained experimental results provide new insights into the deposition process in micro-scale and will be used to validate a developed numerical model.dc201

Modeling anisotropic diffusion using a departure from isotropy approach

There are a large number of finite volume solvers available for solution of isotropic diffusion equation. This article presents an approach of adapting these solvers to solve anisotropic diffusion equations. The formulation works by decomposing the diffusive flux into a component associated with isotropic diffusion and another component associated with departure from isotropic diffusion. This results in an isotropic diffusion equation with additional terms to account for the anisotropic effect. These additional terms are treated using a deferred correction approach and coupled via an iterative procedure. The presented approach is validated against various diffusion problems in anisotropic media with known analytical or numerical solutions. Although demonstrated for two-dimensional problems, extension of the present approach to three-dimensional problems is straight forward. Other than the finite volume method, this approach can be applied to any discretization method

The trans-ancestral genomic architecture of glycemic traits

Glycemic traits are used to diagnose and monitor type 2 diabetes and cardiometabolic health. To date, most genetic studies of glycemic traits have focused on individuals of European ancestry. Here we aggregated genome-wide association studies comprising up to 281,416 individuals without diabetes (30% non-European ancestry) for whom fasting glucose, 2-h glucose after an oral glucose challenge, glycated hemoglobin and fasting insulin data were available. Trans-ancestry and single-ancestry meta-analyses identified 242 loci (99 novel; P < 5 x 10(-8)), 80% of which had no significant evidence of between-ancestry heterogeneity. Analyses restricted to individuals of European ancestry with equivalent sample size would have led to 24 fewer new loci. Compared with single-ancestry analyses, equivalent-sized trans-ancestry fine-mapping reduced the number of estimated variants in 99% credible sets by a median of 37.5%. Genomic-feature, gene-expression and gene-set analyses revealed distinct biological signatures for each trait, highlighting different underlying biological pathways. Our results increase our understanding of diabetes pathophysiology by using trans-ancestry studies for improved power and resolution.A trans-ancestry meta-analysis of GWAS of glycemic traits in up to 281,416 individuals identifies 99 novel loci, of which one quarter was found due to the multi-ancestry approach, which also improves fine-mapping of credible variant sets.Diabetes mellitus: pathophysiological changes and therap

A distance-function-based Cartesian (DIFCA) grid method for irregular geometries

A distance-function-based Cartesian grid (DIFCA) method is presented for conduction heat transfer in irregular geometries. The irregular geometries are identified by distance functions. The finite-volume method is used to discretize the heat conduction equation. Non-zero departure from regular geometries terms are added to the discretization equations for the control volumes bisected by irregular boundaries. With these additional departure terms, the existing Cartesian finite-volume solver can be modified easily to model heat conduction in irregular geometries. Given boundary temperatures, given boundary fluxes and convective heat transfer at irregular boundaries are considered. Non-zero heat generation is also modeled. The proposed procedure is validated against eight test cases where good agreements are achieve

Analysis of effects of active sources on observed phase velocity based on the thin layer method

10.1016/j.jappgeo.2010.11.005Journal of Applied Geophysics73149-5