C039 — Modeling Water Absorption in Wood with an Improved Approximation Method
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- ASHRAE
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Combined heat and moisture transfer modeling is used in building envelope analysis to identify potential moisture durability risks. Moisture transfer in porous materials is typically partitioned into liquid transport and vapor diffusion. Although modeling approaches differ in complexity, coefficients for liquid transport are often derived from laboratory measurements of water absorption by partial immersion. Models generally include the assumption that capillary transport is dominant during the measurement, while vapor diffusion is negligible. This is reasonable for mineral-based materials, but recent work indicates that it may be incorrect for wood. This paper builds on earlier work and develops an improved approximation method for liquid diffusivity in wood from water absorption measurements. The approach does not require additional data beyond ordinary hygrothermal property measurements, and it partitions vapor and liquid transport in a practical way that is guided by current understanding of wood–water interactions. The improved liquid diffusivity approach is calibrated using one-dimensional simulations compared with measured water uptake in a range of wood species from the literature.
Product Details
- Published:
- 2022
- Number of Pages:
- 10
- Units of Measure:
- Dual
- Product Code(s):
- DBldgsXV-C039
