Liquid water flow in Pinus radiata during drying

Scheepers, Gerhard; Morén, Tom; Rypstra, T.

doi:10.1007/s00107-007-0171-y

Cited by 16 publications

(4 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For wood the possibility of such basic mechanisms has long been studied, but this material has specificities which may make the process more complex [8][9][10][11]: (i) hardwoods, on which we will focus here, contain long vessels but also a large fraction of voids (fibers) whose connection with the sample free surface is tenuous or inexistent, (ii) bound water (adsorbed) in cell walls can diffuse through the solid structure. In this context, by similarity with knowledge of drying in simpler porous media, it has been considered that in a first stage some water (free water in voids) is withdrawn from the sample by capillary forces, while in a second stage drying essentially occurs by diffusion of vapor and/or bound water through the sample [9,[12][13][14][15]. However, the detailed characteristics of these two phases and the conditions of transition between them are not well identified or experimentally proved by internal observations.…”

Section: Introductionmentioning

confidence: 99%

How Bound Water Regulates Wood Drying

et al. 2020

View full text Add to dashboard Cite

For most wood-based product uses it is essential to remove a large part of the water content from wet or green (fresh-cut) wood, to reduce further dimensional variations under varying humidity conditions, improve its mechanical characteristics and protect it from biological attacks. However, the internal mechanisms of drying are not fully described. Here we observe drying at different scales using macroscopic measurements (weighing), NMR (Nuclear Magnetic Resonance) measurements allowing to distinguish bound and free water contents, and XRCT (X-ray computed tomography) images of air-liquid interfaces at the smallest pore scale (wood lumens). We show that during wood drying, even well above the Fiber Saturation Point, bound water diffusion in cell walls (instead of capillary effects) ensures the extraction of liquid water from pores and its transport towards the surface of evaporation, and thus controls the drying rate. The distribution of bound water content (uniform or heterogeneous) along the main sample axis and the drying rate evolution depend on the competition between the external conditions and a characteristic rate of transport due to bound water diffusion. For sufficiently slow drying this distribution remains homogenous until free water is fully extracted. An original physical phenomenon is thus at work which plays a major role of regulation of water extraction, in that it maintains a constant drying rate and a homogeneous distribution of the (mean) water content throughout the material. These results provide sound concepts for modeling and controlling drying properties of wood materials. They open the way to the understanding or control of the properties of many other materials containing two water types in food or civil engineering applications. Our results complete recent observations that bound water diffusion also controls imbibition in hardwood and finally show that transfers between bound and free water play a major role in the interaction of plant-like systems with water.

show abstract

Section: Introductionmentioning

confidence: 99%

How Bound Water Regulates Wood Drying

et al. 2020

View full text Add to dashboard Cite

show abstract

“…In this case, the surface moisture content also decreased rapidly from about 20% surface moisture content and 40% average moisture content, which was also the point where they estimated the wetline to recede. The nonlinear development of the surface moisture content to about 40% moisture content may be correlated to the nonlinear evolution of the capillary flow rate that can be expected at high moisture contents (Scheepers et al 2007).…”

Section: Resultsmentioning

confidence: 94%

A method to estimate wood surface moisture content during drying

Scheepers

Wiberg²,

Johansson

2017

Maderas, Cienc. tecnol.

View full text Add to dashboard Cite

A method to estimate the surface moisture content below the fibre saturation point that is a function of the surface temperature, wet-and dry bulb temperatures, equilibrium moisture content, and fibre saturation point was evaluated. The method is based on the premise that the surface temperature is solely influenced by the surface moisture content and the climate that the surface is exposed to. The prediction model contends that the surface moisture content is equal to the fibre saturation point when the surface temperature is equal to the wet bulb temperature, and equal to the equilibrium moisture content when the surface temperature is equal to the dry bulb temperature, with a linear interpolation between those two points. The model thus predicts that the average moisture content of a thin piece of veneer can be predicted with fairly good accuracy. Also, when drying boards in a fast changing climate, e.g. fan reversals in industrial kilns, the surface temperature and surface moisture content should change as abruptly as the climate does. Additionally, the surface moisture content should correlate to the known drying phases, with a consistently high surface moisture content during the capillary phase when the wet line is close to the surface, and a quickly decreasing surface moisture content when the wet line moves into the wood during the transition to the diffusion phase. The prediction model was tested in these three scenarios and the results suggest that the basic premise is reasonable, and that the method is useful for surface moisture content estimation.

show abstract

“…Therefore, the luffa can absorb moisture generated by the human body quickly and ensure the dry-touch interface of the mattress. In addition, it can be seen from Figure 7 that after softening treatment, the number of cracks and pores on the surface and middle lamella increased, the cell cavity shrank, and the capillary tension was improved [38]. Furthermore, after softening treatments, the number of hydroxyl bonds in luffa fibers were decreased [13].…”

Section: Resultsmentioning

confidence: 99%

Effect of Chemical Treatments on the Properties of High-Density Luffa Mattress Filling Materials

et al. 2019

View full text Add to dashboard Cite

Luffa is a lightweight porous material with excellent biocompatibility and abundant resources. In this paper, three kinds of softening treatment methods, alkali-hydrogen peroxide (Method 1), alkali-acetic acid (Method 2), and alkali-urea (Method 3), were used to soften high-density (HD) cylindrical luffa (CL) mattress-filling materials (MFM). Microscopic observation, mechanical performance testing and other analyses were performed to evaluate the effects of the three kinds of softening methods on the wettability, compression resilience and support performance of CL MFM. The results showed that: (1) After the treatment by Method 1, Method 2 and Method 3, the peak stress of CL decreased by 73%, 10% and 27%, respectively. In addition, after three kinds of softening treatments, the uniformity of CL increased. (2) When the CL MFM of high density rank treated by Method 1 was compressed by 40%, the firmness values of the surface, core and bottom reduced by 53.49% 40.72%, and 46.17%, respectively, compared to that of untreated CL. In addition, for the CL MFM of high density rank treated by Method 3 and then compressed to 60%, the firmness of the surface layer, core layer and bottom layer reduced by 41.2%, 33.7%, and 36.9%, respectively. (3) The contact angle of luffa treated by Method 3 was the smallest, next came Method 1 and Method 2, and untreated was the largest. (4) After the treatment by Method 3, the fiber bundle of luffa was intact, and the compression resilience of the CL was obviously increased. Therefore, this method can effectively reduce the firmness of MFM and also improve the uniformity and wettability of CL.

show abstract

Liquid water flow in Pinus radiata during drying

Cited by 16 publications

References 7 publications

How Bound Water Regulates Wood Drying

How Bound Water Regulates Wood Drying

A method to estimate wood surface moisture content during drying

Effect of Chemical Treatments on the Properties of High-Density Luffa Mattress Filling Materials

Contact Info

Product

Resources

About