EFFECTS OF THE VELOCITY DISTRIBUTION BEHIND GRIDS ON THE LOCAL HEAT AND MASS TRANSFER IN STAGNATION FLOWS

1990 ◽  
Author(s):  
Volker Kottke ◽  
Gerhard Schuz
Keyword(s):  
Mass Transfer ◽  
Velocity Distribution ◽  
Heat And Mass Transfer ◽  
Local Heat

Numerical Simulation of Heat and Mass Transfer of Limestone Decomposition in Normal Shaft Kiln

2011 ◽  
Author(s):  
Duc Hai Do ◽  
Eckehard Specht
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Large Scale ◽  
Solid Material ◽  
Local Heat ◽  
Operational Parameters ◽  
Calcination Process ◽  
One Dimensional ◽  
Shrinking Core ◽  
Particle Bed

A mathematical model of lime calcination process in normal shafts kiln has been developed to determine the heat and mass transfer between the gas and the solid. The model is one-dimensional and steady state. The transport of mass and energy of the gas and the solid is modeled by a system of ordinary differential equations. A shrinking core approach is employed for the mechanics and chemical reactions of the solid material. The model can be used to predict the temperature profiles of the particle bed, the gas phase along the length of kiln axis. The calcination behavior of the particle bed can be also investigated. The influences of operational parameters such as: energy input, the origin of feed limestone and the lime throughput on the kiln performance including pressure drop are considered. Additionally, the local heat loss through the kiln wall is studied. The results of this study are direct utility for optimization and design of large-scale technical shaft kilns.

scholarly journals Mathematical Modeling of Heat and Mass Transfer Processes with Chemical Reaction at Polymeric Material Ignition by Several Small-Size Hot Particles

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Dmitrii O. Glushkov ◽  
Pavel A. Strizhak
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Polymeric Material ◽  
Local Heat ◽  
Material Surface ◽  
Heat Sources ◽  
Hot Particles ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
Air System

Numerical research of interconnected heat and mass transfer processes in the “two hot particles—polymeric material—air” system was executed. The joint effect of several local heat sources on the main integrated characteristic of ignition process (ignition delay time) was established. Two ignition models characterized by the relative positioning of hot particles on a polymeric material surface were revealed. Besides, there were established characteristics of local heat sources and the distance between them (700  K<Tp<1150 K andL>1.5orTp>1150 K and0.25<L<1.5)when regularities of heat and mass transfer processes in the “two hot particles—polymeric material—air” system are similar to regularities of heat and mass transfer processes in the “single hot particle—polymeric material—air” system.

Evaporation Rate Model for a Natural Convection Glazed Collector/Regenerator

1990 ◽  
Vol 112 (1) ◽  
pp. 51-57 ◽  
Author(s):  
D. J. Nelson ◽  
B. D. Wood
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Evaporation Rate ◽  
Local Heat ◽  
Conjugate Problem ◽  
Water Evaporation ◽  
Transfer Coefficients ◽  
Humid Climate ◽  
Mass Transfer Coefficients ◽  
Local Conditions

In the present work, a numerical method has been applied to model the water evaporation rate of a glazed collector/regenerator component of an open-cycle absorption refrigeration system. This two-dimensional model calculates local heat and mass-transfer coefficients as part of the solution. The air flow in the glazed channel is driven by the combined buoyancy of both heat and mass transfer (water evaporation). Since the heat and mass-transfer coefficients each depend on both of the driving potentials determined by local conditions in the falling film, a solution of the conjugate problem is required. The resulting nonuniform air-film interface conditions cause the local heat and mass transfer to differ significantly from the uniform boundary condition case. The glazed collector/regenerator is much less sensitive to the ambient temperature and humidity than the unglazed collector. The addition of a glazing over the collector/regenerator provides a significant performance improvement and enhances solution regeneration in a windy humid climate. The glazed collector/regenerator water evaporation rate is higher relative to the unglazed case because the reduction in convective and radiative heat losses increases the absorbent temperature and vapor pressure sufficiently to overcome the concomitant reduction in the mass-transfer coefficient.

Heat and Mass Transfer Associated With Condensation on a Moving Drop: Solutions for Intermediate Reynolds Numbers by a Boundary Layer Formulation

1985 ◽  
Vol 107 (2) ◽  
pp. 409-416 ◽  
Author(s):  
T. Sundararajan ◽  
P. S. Ayyaswamy
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Saturated Vapor ◽  
Time History ◽  
Local Heat ◽  
Surface Shear Stress ◽  
Contact Heat ◽  
Surface Shear ◽  
Wide Range

Condensation heat and mass transfer to a liquid drop moving in a mixture of saturated vapor and a noncondensable have been evaluated. The Reynolds number of the drop motion is 0(100). The quasi-steady, coupled, boundary layer equations for the flow field and the transport in the gaseous phase are simultaneously solved. The heat transport inside the drop is treated as a transient process. Results are presented for the heat and mass transport rates to the drop, the surface shear stress, the velocity profiles across the boundary layer, and the temperature-time history of the drop. The comparisons of results with experimental data, where available, show excellent agreement. Tables summarizing results appropriate to a wide range of condensation rates have been included. Local heat and mass transfer rates have also been presented. These features will make the paper useful to the designer of direct contact heat transfer equipment.

scholarly journals Mathematical model of compact type evaporator

2018 ◽  
Vol 180 ◽  
pp. 02012
Author(s):  
Martin Borovička ◽  
Tomáš Hyhlík
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Ad Hoc ◽  
Data Transfer ◽  
Local Heat ◽  
Geometrical Parameters ◽  
Transfer Coefficients ◽  
Inlet Conditions ◽  
Transfer Problems

In this paper, development of the mathematical model for evaporator used in heat pump circuits is covered, with focus on air dehumidification application. Main target of this ad-hoc numerical model is to simulate heat and mass transfer in evaporator for prescribed inlet conditions and different geometrical parameters. Simplified 2D mathematical model is developed in MATLAB SW. Solvers for multiple heat and mass transfer problems - plate surface temperature, condensate film temperature, local heat and mass transfer coefficients, refrigerant temperature distribution, humid air enthalpy change are included as subprocedures of this model. An automatic procedure of data transfer is developed in order to use results of MATLAB model in more complex simulation within commercial CFD code. In the end, Proper Orthogonal Decomposition (POD) method is introduced and implemented into MATLAB model.

Digital Computation Methods for Evaluating Heat Flux in Condensers

1965 ◽  
Vol 7 (2) ◽  
pp. 177-184 ◽  
Author(s):  
D. Chisholm ◽  
T. F. Provan ◽  
D. Mitchell
Keyword(s):  
Mass Transfer ◽  
Heat Flux ◽  
Numerical Methods ◽  
Heat And Mass Transfer ◽  
Digital Computer ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Digital Computation

Numerical methods of evaluating heat- and mass-transfer coefficients and local heat fluxes in surface condensers are outlined using the correlations for the vapour-side coefficients of Berman and Fuks, Chilton and Colburn, and Akers, Davis and Crawford. The procedures are particularly appropriate where a digital computer is used in solving the equations.

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