Characteristics of radio-frequency/vacuum combined with mechanical press drying of heavy softwood timbers with longitudinal kerf

Holzforschung ◽  
2021 ◽  
Vol 75 (1) ◽  
pp. 48-55
Author(s):  
Xuefeng Zhao ◽  
Changjin Lee
Keyword(s):  
Dielectric Permittivity ◽  
Temperature Gradient ◽  
Moisture Content ◽  
Radio Frequency ◽  
Radiata Pine ◽  
Douglas Fir ◽  
Fixed Frequency ◽  
Mechanical Press

AbstractThe aim of this study was to evaluate the characteristics of radio-frequency/vacuum combined with mechanical press (RF/VP) drying on three softwood timbers (Douglas fir, Hemlock, and Radiata pine) with longitudinal kerfs. The results were as follows: Due to the dielectric permittivity of wood, RF/VP drying at a fixed frequency of 13.56 MHz significantly influenced the moisture content (MC) distribution, the number of surface checks, shrinkage, and warp. These observations were attributed to the formation of a temperature gradient along the charge plate during the drying. The presence or absence of pith, more affected an occurrence of surface checks than that of the stresses within the wood during drying. The longitudinal kerf reduced the number of surface checks, but did not affect the MC distribution or the twist after drying.

Stresses Induced in Fiber-Reinforced Tubes Due to Changes in Temperature and Moisture

1995 ◽  
Vol 117 (2) ◽  
pp. 228-234 ◽  
Author(s):  
Byung S. Kim ◽  
Terry F. Lehnhoff
Keyword(s):  
Temperature Gradient ◽  
Moisture Content ◽  
Boundary Conditions ◽  
Arbitrary Orientation ◽  
Fiber Reinforced ◽  
Stress Solution ◽  
Hygrothermal Stress

An orthotropic hygrothermal stress solution has been formulated for an infinitely long fiber-reinforced tube of any number of plies of any material, with arbitrary orientation of each of the plies. The solution allows the determination of stresses when the tube is subjected to changes in temperature and moisture content. In the formulation, a temperature gradient through the thickness has been taken into account such that the formulation can be applied when the temperature inside the tube is not the same as that outside. This set of equations, together with the prescribed boundary conditions, has been solved numerically. It is shown that the stresses induced due to moisture absorbed from the environment are significant.

scholarly journals Rapid determination of meat moisture content using radio-frequency dielectric measurement

IEEE Access ◽  
2018 ◽  
pp. 1-1 ◽  
Author(s):  
Jianxu Wang ◽  
Lifeng Fan ◽  
Qiao Zhou ◽  
Jinhai Li ◽  
Pengfei Zhao ◽  
...  
Keyword(s):  
Moisture Content ◽  
Radio Frequency ◽  
Rapid Determination ◽  
Dielectric Measurement

scholarly journals Dielektrické vlastnosti zemědělských produktů a některé jejich aplikace

2008 ◽  
Vol 54 (No. 2) ◽  
pp. 104-112 ◽  
Author(s):  
S.O Nelson
Keyword(s):  
Dielectric Properties ◽  
Moisture Content ◽  
Radio Frequency ◽  
Fruits And Vegetables ◽  
Agricultural Products ◽  
Dielectric Heating ◽  
Quality Factors ◽  
Poultry Products ◽  
Microwave Dielectric ◽  
Microwave Dielectric Heating

The use of dielectric properties of agricultural products for sensing moisture in grain and seed and their application in radio-frequency and microwave dielectric heating is discussed briefly. Values for the dielectric properties of a number of products, including grain and seed, fruits and vegetables, and poultry products, are presented graphically to show the dependence of these properties on frequency, moisture content, and temperature. The potential for using the dielectric properties to sense quality factors other than moisture content is also considered.

In-Plane Moisture Content and Specific Gravity Evaluation of Oriented Strandboard Using a Radio Frequency Technique

2010 ◽  
Vol 60 (7) ◽  
pp. 622-628 ◽  
Author(s):  
Xiaojian Liu ◽  
Jilei Zhang ◽  
J. Patrick Donohoe ◽  
Philip H. Steele
Keyword(s):  
Specific Gravity ◽  
Moisture Content ◽  
Radio Frequency ◽  
Oriented Strandboard

Relationships Between Sapwood Amount, Latewood Percentage, Moisture Content and Crown Vitality of Douglas Fir, Pseudotsuga Menziesii

IAWA Journal ◽  
1993 ◽  
Vol 14 (4) ◽  
pp. 413-427 ◽  
Author(s):  
Ingrid de Kort
Keyword(s):  
The Netherlands ◽  
Moisture Content ◽  
Pseudotsuga Menziesii ◽  
Douglas Fir

Relationships between sapwood amount, latewood percentage, moisture content and crown vitality were studied in 171 Douglas firs [Pseudotsuga menziesii (Mirb.) Franco] belonging to different vitality classes. The trees originated from 10 stands in the Netherlands varying in age from 25-70 years.

Analysis on Heat Transfer Intensity of Bamboo Structure Wall in Warm and Humid Environment

2013 ◽  
Vol 639-640 ◽  
pp. 721-726
Author(s):  
Ji Bo Long ◽  
Ping Wang ◽  
Yu Lou Li ◽  
Si Yi Huang
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Moisture Content ◽  
Heat Storage ◽  
Temperature Wave ◽  
Storage Coefficient ◽  
Humid Environment ◽  
Heat Transfer Capacity ◽  
Bamboo Structure ◽  
Total Moisture Content

Based on the fundamentals of heat and moisture transfer in porous media, characteristics of heat transfer intensity of a bamboo structure wall are analyzed when the moisture content changes under the action of natural warm and humid environment. The results show that: when the moisture content changes, the effective coefficient of heat conductivity and specific heat capacity of bamboo both change, and physical parameters (e.g., heat transfer capacity, heat storage capacity, temperature distribution, attenuation coefficient of temperature wave, delay coefficient of temperature wave) all change accordingly. When the total moisture content of the wall increases, the temperature difference between inside and outside surfaces of the wall is reduced, and attenuation and delay coefficient of temperature wave both increase. All of these improve the thermal comfort of indoor environment, but the heat transfer capacity through the wall increases. If the total moisture content of the wall is constant and the moisture distribution along the thickness direction of the wall changes, the temperature gradient decreases and the heat storage coefficient increases in bamboo layer of high moisture content, and the temperature gradient increases and the heat storage coefficient decreases in bamboo layer of low moisture content.

scholarly journals Quality of Milled Rice from Large-Scale Dried Paddy Rice by Hot Air Combined with Radio Frequency Heating

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2277
Author(s):  
Karn Chitsuthipakorn ◽  
Sa-nguansak Thanapornpoonpong
Keyword(s):  
Moisture Content ◽  
Radio Frequency ◽  
Block Design ◽  
Specific Energy Consumption ◽  
Brown Rice ◽  
Convective Drying ◽  
Control Treatment ◽  
Rf Heating ◽  
Drying Time ◽  
Hot Air

A scaled-up process for paddy drying was developed using hot air (HA) combined with radio frequency (RF) heating. The study was conducted using hot air (control treatment) arranged in descending order in four temperature levels, namely 80 °C at moisture content of 25–26%, 70 °C at moisture content of 20–25%, 60 °C at moisture content of 17–20%, and 50 °C at moisture content of 13–17%, as well as with hot air combined with radio frequency (HA/RF) at different paddy temperatures (45–60 °C) by adjusting the appropriate RF energy when passing through RF heating chamber, namely HA/RF45, HA/RF50, HA/RF55, and HA/RF60. Each treatment was performed in three replicates and data were statistically analyzed in a randomized complete block design. The quality attributes of paddies affected by the drying process were assessed: fissure percentage, color, milling quality, and sensory evaluation. The drying efficiency showed that the drying time and the specific energy consumption could be decreased by up to 54.44% and 23.17% at HA/RF60 and HA/RF45, respectively. As the RF heating temperature increased, the fissure percentage of brown rice kernels at HA/RF45 and HA was not significantly impacted. Regarding color evaluation, combining RF heating and convective drying at all given conditions could be statistically applied in terms of the b*, WI, and ΔE* value. Considering the milling yield of HA as the baseline, head rice yield was maximized at HA/RF45, while bran yield reached the maximum at HA/RF60. The liking score of cooked rice after it was dried using the HA method was the highest. This study concludes that the HA/RF45 was the most appropriate drying condition, and this may provide preliminary exposure to the industrial drying of paddies.

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