A Transient Heat and Mass Transfer Model of Residential Attics Used to Simulate Radiant Barrier Retrofits, Part I: Development

1998 ◽  
Vol 120 (1) ◽  
pp. 32-38 ◽  
Author(s):  
M. A. Medina ◽  
D. L. O’Neal ◽  
W. D. Turner
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Fluxes ◽  
Dew Point ◽  
Weather Data ◽  
Transfer Model ◽  
Mass Transfer Model ◽  
Air Temperatures ◽  
Gain Loss ◽  
Heating Loads

This paper describes a transient heat and mass transfer model of residential attics. The model is used to predict hourly ceiling heat gain/loss in residences with the purpose of estimating reductions in cooling and heating loads produced by radiant barriers. The model accounts for transient conduction, convection, and radiation and incorporates moisture and air transport across the attic. Environmental variables, such as solar loads on outer attic surfaces and sky temperatures, are also estimated. The model is driven by hourly weather data which include: outdoor dry bulb air temperature, horizontal solar and sky radiation, wind speed and direction, relative humidity (or dew point), and cloud cover data. The output of the model includes ceiling heat fluxes, inner and outer heat fluxes from all surfaces, inner and outer surface temperatures, and attic dry bulb air temperatures. The calculated fluxes have been compared to experimental data of side-by-side testing of attics retrofit with radiant barriers. The model predicts ceiling heat flows with an error of less than ten percent for most cases.

Simulation of Drying Behavior of Cotton Bobbins by a Simultaneous Heat and Mass Transfer Model

2011 ◽  
Vol 312-315 ◽  
pp. 854-859
Author(s):  
Ugur Akyol ◽  
Kamil Kahveci ◽  
Ahmet Cihan ◽  
Dinçer Akal
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Heat And Mass Transfer ◽  
Textile Industry ◽  
Moisture Ratio ◽  
Transfer Model ◽  
Mass Transfer Model ◽  
Air Temperatures ◽  
Drying Behavior ◽  
Simultaneous Heat

In this study, the drying process of cotton bobbins for different drying air temperatures has been simulated by a simultaneous heat and mass transfer model. In the model, the mass transfer is assumed to be controlled by diffusion. In order to make the simulation, firstly, drying behavior of cotton bobbins for different drying air temperatures has been determined on an experimental bobbin dryer setup which was designed and manufactured based on hot-air bobbin dryers used in textile industry. In the experimental setup, temperatures of different points in cotton bobbins were measured by thermocouples placed inside the bobbins, and weights of the bobbins during the drying period were determined by means of a load cell. Then, moisture ratio and temperature values of the model have been fitted to the experimental ones. The fit was performed by selecting the values for the diffusion coefficient and the thermal diffusivity in the model in such a way that these values make the sum of the squared differences between the experimental and the model results for moisture ratio and temperature minimum. Results show that there is a good agreement between the model results and the experimental measurements. The results also show that temperature has a significant effect on mass transfer and the temperature dependence of the diffusion coefficient may be expressed by an Arrhenius type relation.

A Study of GOTHIC 8.0 Code Application to AP1000 Containment Response

2013 ◽  
Author(s):  
Guodong Wang ◽  
Zhe Wang
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Mass Transfer Process ◽  
Transfer Model ◽  
Mass Transfer Model ◽  
Containment Model ◽  
Evaporation Heat ◽  
Containment Shell ◽  
Film Heat Transfer ◽  
Inside Wall

The AP1000 containment model has been developed by using WGOTHIC version 4.2 code. Condensation heat and mass transfer from the volumes to the containment shell, conduction through the shell, and evaporation from the shell to the riser were all calculated by using the special CLIMEs model. In this paper, the latest GOTHIC version 8.0 code is used to model both condensation and evaporation heat and mass transfer process. An improved heat and mass transfer model, the diffusion layer model (DLM), is adopted to model the condensation on the inside wall of containment. The Film heat transfer coefficient option is used to model the evaporation on the outside wall of containment. As a preliminary code consolidation effort, it is possible to use GOTHIC 8.0 code as a tool to analysis the AP1000 containment response.

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