Forced Flow Heat and Mass Transfer to a Cylinder Surrounded by a Porous Material With Applications to NBC Protective Clothing

2002 ◽  
Author(s):  
Michael P. Sobera ◽  
Chris R. Kleijn ◽  
Paul Brasser ◽  
Harry E. A. Van den Akker
Keyword(s):  
Mass Transfer ◽  
Flow Field ◽  
Heat And Mass Transfer ◽  
Protective Clothing ◽  
Numerical Study ◽  
Air Flow ◽  
Forced Flow ◽  
Dimensionless Numbers ◽  
Flow Heat ◽  
Human Limb

Increased permeability of clothing material can reduce the heat load caused by Nuclear-Biological-Chemical (NBC) protective clothing, but implies reduced protection. The goal of the present work is to study the influence of the air permeability on human comfort and safety. A numerical study is presented of the air flow with heat and mass transfer around a cylinder, mimicking a human limb, placed in a turbulent external air flow and surrounded by protective clothing. The problem is described in terms of the relevant dimensionless numbers. The dependence of the flow field underneath the clothing and the heat and mass transfer to the limb are studied as a function of the Reynolds, Darcy and Damko¨hler numbers, which are a measure for the wind speed, clothing permeability and adsorptivity of the poisonous gas, respectively. The air flow simulations are validated with experiments, in which the flow field around a bare cylinder and in the space between a cylinder and its porous cover, is measured with LDA. Scaling rules for heat and mass transfer are presented.

scholarly journals Numerical study on heat and mass transfer characteristics of the counter-flow heat-source tower (CFHST)

2017 ◽  
Vol 145 ◽  
pp. 318-330 ◽  
Author(s):  
Jun Lu ◽  
Wuyan Li ◽  
Yongcai Li ◽  
Liyue Zeng ◽  
Lulu Yang ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat Source ◽  
Heat And Mass Transfer ◽  
Numerical Study ◽  
Counter Flow ◽  
Transfer Characteristics ◽  
Flow Heat

Numerical Study on Slag Flow in an Entrained-Flow Gasifier

2007 ◽  
Author(s):  
Sheng Liu ◽  
Yingli Hao
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Numerical Study ◽  
Equations Of Motion ◽  
Slag Layer ◽  
Entrained Flow ◽  
Vof Model ◽  
Entrained Flow Gasifier ◽  
Flow Heat ◽  
Critical Viscosity

A 2-D model for the slag flow, heat and mass transfer and solidification was developed to simulate the slag motion in the entrained-flow gasifier. Some assumptions were adopted to make the simulation practical and reduce the calculating time. The slag is treated as Newtonian fluid at the temperature above the temperature of critical viscosity, and solid below the temperature of critical viscosity. VOF model is used to capture the free surface between the syngas and slag layer. Numerical simulation of the slag flow in the gasifier is conducted by solving the equations of motion. The thickness of the slag layer, temperature distribution in the gasifier can be obtained. A series of simulations have been carried out to test the model. The effects of main variables on the flow, heat and mass transfer of slag on the refractory wall in the gasifier are analyzed numerically.

scholarly journals Modelling Droplet Heat and Mass Transfer in Aero-Engine Bearing Chambers

2019 ◽  
Author(s):  
Dafne Gaviria Arcila ◽  
Hervé Morvan ◽  
Kathy Simmons ◽  
Stephen Ambrose ◽  
Michael Walsh ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Evaporation Rate ◽  
Numerical Study ◽  
Droplet Diameter ◽  
Air Flow ◽  
Core Region ◽  
Evaporation Process ◽  
Data Set ◽  
The Core

Abstract The oil inside aeroengine bearing chambers can be found in many forms, including droplets which interact with the core airflow. The ability to model such bearing chambers computationally is desirable and thus a better understanding of the evaporation process of oil droplets is of great interest. Previous studies have analyzed the flow of isothermal droplets in bearing chambers. However, further investigation is needed into the heating of droplets in the highly rotating core region. This will enable designers to evaluate the behavior of droplets in a chamber and the likelihood that they will evaporate. The aim of this research is to analyze the oil droplet evaporation process under aeroengine bearing chamber representative conditions. An ultimate goal is the ability to predict the oil-air heat and mass transfer in the core flow region, as well as to develop an understanding of the flow inside a droplet, and how this affects evaporation. This latter is important as it has not been studied before. This paper presents the results of a numerical study of the evaporation process of a single droplet under bearing chamber temperature and air flow conditions. The two-phase flow is simulated using ANSYS Fluent with the volume of fluid approach and the evaporation process with the “D−square law”. First, the modelling approach is validated against previous experimental and numerical analysis of fuel droplets in an air flow with heat transfer. The simulation results were in excellent agreement with a benchmarking data set. The validated approach is then applied for investigation to smaller, bearing chamber representative droplets of an oil base stock used in jet engines. The oil evaporation rate was quantified as well as the evolution of droplet diameter, which revealed the effect of different air velocities and temperatures on the droplet. The extent to which evaporation rate increased with air velocity and temperature is quantified. It is concluded that droplets of initial diameters less than 200μm that remain in the chamber core region for more than 0.3s are likely to evaporate completely. This study allows us to estimate droplet heat and mass transfer and the associated phase change in a bearing chamber. It also provides best practice to predict the performance of small droplets under the effects of high temperature and velocity convective air flows. In future work this methodology will be applied in simulations in a representative bearing chamber to predict how the cooling process is affected by oil evaporation.

Numerical Study of the Combined Free-Forced Convection and Mass Transfer Flow Past a Vertical Porous Plate in a Porous Medium with Heat Generation and Thermal Diffusion

2006 ◽  
Vol 11 (4) ◽  
pp. 331-343 ◽  
Author(s):  
M. S. Alam ◽  
M. M. Rahman ◽  
M. A. Samad
Keyword(s):  
Mass Transfer ◽  
Flow Field ◽  
Differential Equations ◽  
Forced Convection ◽  
Heat Generation ◽  
Numerical Study ◽  
Porous Plate ◽  
Integration Scheme ◽  
Suction Parameter ◽  
Transfer Flow

The problem of combined free-forced convection and mass transfer flow over a vertical porous flat plate, in presence of heat generation and thermaldiffusion, is studied numerically. The non-linear partial differential equations and their boundary conditions, describing the problem under consideration, are transformed into a system of ordinary differential equations by using usual similarity transformations. This system is solved numerically by applying Nachtsheim-Swigert shooting iteration technique together with Runge-Kutta sixth order integration scheme. The effects of suction parameter, heat generation parameter and Soret number are examined on the flow field of a hydrogen-air mixture as a non-chemical reacting fluid pair. The analysis of the obtained results showed that the flow field is significantly influenced by these parameters.

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