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The Process of doing Hygrothermal simulation of a Crawl Space
Posted Apr 27, 2012, 6:54 a.m. EDT Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.2a 1 Reply
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My name is Morten and I have a line of questions regarding COMSOL.
First, a small introduction of the project and myself.
For COMSOL related questions se next post.
I am doing my Master thesis at the Technical University of Denmark together with at fellow student. We are both studying Civil engineering with the following areas of expertise: Building physics, energy calculations for saving and optimization, practically application of theory.
Our Master thesis is a study of hygrothermal behavior in crawl spaces and a part of this will be to build a simulation model. Earlier we did our own code (in MATLAB) on a simplified semi 2D model which we calculated the temperature, vapour pressure and hence relative humidity in the crawl space with respect to both, outdoor temperatures, relative air humidity, wind direction and speed, initial soil humidity. We think that COMSOL is the tool we need to make a more detailed model.
COMSOL was recommended to us be our supervision but his knowledge of the program is rater limited. We have only heard of the program before the project but have spent a lot of time reading manuals and doing tutorials on varies problems.
We seek help here on the COMSOL forum to get going. The main goal is to make a strategy from beginning to end which include taking above which physics to apply at what problems. Once this is establish we will use this post to ask how-to-do-help.
/Morten
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1) The crawl space (CS) which face the construction and the soil.
2) The interior which face the construction. This will be defined with a constant temperature.
3) The exterior which face the soil and construction. It is directly connected to CS by ventilation opening. Here will the climate data be defined (temperatures, relative humidity, wind data)
4) The soil which face the exterior, construction and CS.
5) Construction consisting of the floor separating the crawl space (CS) from indoor environment, an above-ground-wall separating the CS from exterior and a in-ground-wall/foundation separating the CS from ground.
The input data for the model: step wise data with hourly intervals of the exterior temperature, relative humidity, wind direction, metrology wind speed. Constant indoor temperature.
Physics:
The construction: Conduction
The soil: coupled heat and vapour transport by conduction and diffusion
Ventilation: Advection
Questions
For starters I do some simplified simulations and therefor ask for suggestions for;
1) physics I should use for a capillary suction transport study in porous materials (in this case vapour transport in soil).
2) I need to make a simulation for the ventilation flow. At the end the inflow (at duct opening) need to be defined by the wind speed and direction at exterior environment. Then there is a pressure loss in the duct (at openings and friction). Is the simulation best done by the CFD-branch or can you recommend another way of doing this?
3) how the coupled heat and vapour transport in the soil domain can be done.
/Morten