Moisture transfer in porous materials exposed to combined humidity and temperature gradients

Moisture migration is responsible for much damage in modern buildings. Air infiltrations were almost eliminated because of the use of various qualities of materials and insulation. Water is mainly transferred through building materials by diffusion, under three different phases (vapor, liquid and bound). Most of the time, indoor and outdoor conditions are different and strong gradients of humidity and temperature exist within the building walls. Many models describing moisture diffusion through capillary-porous materials exist, but none of them is universally accepted. The proposed work includes a presentation of these theoretical models which will be implemented and evaluated by a series of experiments. Data is obtained for Oriented Strand Board (OSB). The existing apparatus, developed by Crimm (1992) and Mosier (1994) consists of a wood-based sample, sealed between two environmental chambers. Each chamber has its own humidity and temperature control system. This apparatus is an alternative to the standard “cup” method to determine moisture permeability of wood samples. The relative humidity is not controlled by salt solutions. Forced air circulation at the surface of the specimen results in uniform conditions in the chamber and faster results. The experimental apparatus is upgraded for better control. The relative humidity is controlled in a range of 5- 75 percent, within 0.2 percent of the setpoint, and the temperature can be maintained within 0.05°C, in a range of 15-50°C. The apparatus operation is validated by comparing a series of isothermal data with published results. Good agreement is found between these data and those reported by two different authors. Several nonisothermal experiments are conducted to implement and evaluate the moisture diffusion theory.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Mechanical Engineering

Department dc:contributor.department

Mechanical Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1996

Author dc:creator

• Chevrier, Vincent François

Chair dc:contributor.committeechair

• Thomas, William C.

Committee members dc:contributor.committeemember

• Mahan, James Robert
• Diller, Thomas E.

• moisture migration

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-03042009-041324

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/41432