Modelling drying processes of fuelbeds of Scots pine needles with initial moisture content above the fibre saturation point by two-phase models

2012 ◽  
Vol 21 (4) ◽  
pp. 418 ◽  
Author(s):  
Sen Jin ◽  
Pengyu Chen
Keyword(s):  
Moisture Content ◽  
Scots Pine ◽  
Initial Moisture Content ◽  
Fibre Saturation Point ◽  
Phase Model ◽  
Fuel Moisture ◽  
Drying Process ◽  
Rating Systems ◽  
Saturation Point ◽  
Two Phase

Modelling the drying process of fuel moisture with initial moisture content above the fibre saturation point can be used to determine when fuel will become sufficiently dry (after precipitation) to burn and provide a more accurate prediction of fire potential. Based on analysis of the mechanism by which the drying process occurs, we propose a model comprising two phases distinguished by a moisture threshold of 0.35 g g–1, the fibre saturation point; one phase is controlled by evaporation and the other by diffusion. Each phase has a distinct equation with a different timelag. We compared our two-phase model with a one-phase model (one-timelag model) and another two-phase model by estimating drying of 15 Scots pine (Pinus sylvestris var. mongolica) needle fuelbeds. The results indicate that the two-timelag model improves moisture modelling, thereby reducing mean absolute error by more than 30%, i.e. from 0.0047 g g–1 (one-phase model) to 0.0030 g g–1. The model yields consistent results, further suggesting its potential for improving fuel moisture prediction of fire danger rating systems. The first timelag of the model is affected by fuelbed properties. Equations based on variables that represent fuelbed properties were established, thus saving time when estimating parameters for stand-specific fuel moisture models.

Initial moisture content and the exponential drying process

1982 ◽  
Vol 12 (1) ◽  
pp. 90-92 ◽  
Author(s):  
C. E. Van Wagner
Keyword(s):  
Moisture Content ◽  
Forest Fire ◽  
Initial Moisture Content ◽  
Necessary Condition ◽  
Fuel Moisture ◽  
Drying Process ◽  
Exponential Equation ◽  
Starting Point ◽  
Forest Fire Danger ◽  
Negative Exponential

Estimation of fuel moisture in Canadian forest fire danger rating during a drying period is accomplished through a negative exponential equation. Data are presented to show that for pine litter the slope of this equation is independent of the starting point, a necessary condition for its validity.

scholarly journals Wood Chip Drying through the Using of a Mobile Rotary Dryer

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1590 ◽  
Author(s):  
Angelo Del Giudice ◽  
Andrea Acampora ◽  
Enrico Santangelo ◽  
Luigi Pari ◽  
Simone Bergonzoli ◽  
...  
Keyword(s):  
Moisture Content ◽  
Power Plants ◽  
Black Locust ◽  
Thermal Power ◽  
Initial Moisture Content ◽  
Wood Chip ◽  
Wood Chips ◽  
Cocurrent Flow ◽  
Drying Process ◽  
Rotary Dryer

Drying is a critical point for the exploitation of biomass for energy production. High moisture content negatively affects the efficiency of power generation in combustion and gasification systems. Different types of dryers are available however; it is known that rotary dryers have low cost of maintenance and consume 15% and 30% less in terms of specific energy. The study analyzed the drying process of woody residues using a new prototype of mobile rotary dryer cocurrent flow. Woodchip of poplar (Populus spp.), black locust (Robinia pseudoacacia L.), and grapevine (Vitis vinifera L.) pruning were dried in a rotary drier. The drying cycle lasted 8 h for poplar, 6 h for black locust, and 6 h for pruning of grapevine. The initial biomass had a moisture content of around 50% for the poplar and around 30% for grapevine and black locust. The study showed that some characteristics of the biomass (e.g., initial moisture content, particle size distribution, bulk density) influence the technical parameters (i.e., airflow temperature, rate, and speed) of the drying process and, hence, the energy demand. At the end of the drying process, 17% of water was removed for poplar wood chips and 31% for grapevine and black locust wood chips. To achieve this, result the three-biomass required 1.61 (poplar), 0.86 (grapevine), and 1.12 MJ kgdry solids−1 (black locust), with an efficiency of thermal drying (η) respectively of 37%, 12%, and 27%. In the future, the results obtained suggest an increase in the efficiency of the thermal insulation of the mobile dryer, and the application of the mobile dryer in a small farm, for the recovery of exhaust gases from thermal power plants.

scholarly journals Cherry Tomato Drying: Sun versus Convective Oven

Horticulturae ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 40
Author(s):  
Vincenzo Alfeo ◽  
Diego Planeta ◽  
Salvatore Velotto ◽  
Rosa Palmeri ◽  
Aldo Todaro
Keyword(s):  
Moisture Content ◽  
Initial Moisture Content ◽  
Drying Process ◽  
Drying Time ◽  
Oven Drying ◽  
Sun Drying ◽  
Different Temperatures ◽  
Final Water Content ◽  
Drying Curves ◽  
Drying Conditions

Solar drying and convective oven drying of cherry tomatoes (Solanum lycopersicum) were compared. The changes in the chemical parameters of tomatoes and principal drying parameters were recorded during the drying process. Drying curves were fitted to several mathematical models, and the effects of air temperature during drying were evaluated by multiple regression analyses, comparing to previously reported models. Models for drying conditions indicated a final water content of 30% (semidry products) and 15% (dry products) was achieved, comparing sun-drying and convective oven drying at three different temperatures. After 26–28 h of sun drying, the tomato tissue had reached a moisture content of 15%. However, less drying time, about 10–11 h, was needed when starting with an initial moisture content of 92%. The tomato tissue had high ORAC and polyphenol content values after convective oven drying at 60 °C. The dried tomato samples had a satisfactory taste, color and antioxidant values.

scholarly journals Impact of Initial Moisture Content on the Drying Process of Wood Exposed to Infrared Radiation

BioResources ◽  
2013 ◽  
Vol 8 (3) ◽  
Author(s):  
Erzsébet Cserta ◽  
Gergely Hegedűs ◽  
Gergely Agócs ◽  
Róbert Németh
Keyword(s):  
Moisture Content ◽  
Infrared Radiation ◽  
Initial Moisture Content ◽  
Drying Process

scholarly journals Moisture state variety in poplar lumber with moisture content above fibre saturation point during hot-press drying

2018 ◽  
Vol 64 (6) ◽  
pp. 730-737
Author(s):  
Junfeng Hou ◽  
Songlin Yi ◽  
Yongdong Zhou ◽  
Bin Pan
Keyword(s):  
Moisture Content ◽  
Fibre Saturation Point ◽  
Hot Press ◽  
Saturation Point ◽  
Moisture State

Heat and Mass Transfer during Contact Drying in a Laundry Calender

1973 ◽  
Vol 187 (1) ◽  
pp. 591-599
Author(s):  
J. F. T. MacLaren ◽  
A. A. Nicol ◽  
R. Wallace
Keyword(s):  
Mass Transfer ◽  
Moisture Content ◽  
Heat And Mass Transfer ◽  
Initial Moisture Content ◽  
Temperature Profiles ◽  
Drying Process ◽  
Steam Temperature ◽  
Empirical Expression ◽  
Contact Drying ◽  
Physical Variables

Contact drying of fabric was studied using a two-roll steam-heated laundry calender. The effects on heat and mass transfer of steam temperature, fabric initial moisture content, fabric velocity, contact pressure and steam-side heat transfer coefficient were observed experimentally. Bed and roller surface temperature profiles were measured to assist in interpreting and subsequently analysing the drying process. The experimental results were correlated using dimensionless parameters derived from a dimensional analysis of a drying equation. An empirical expression was obtained that related the final moisture content of the fabric to the initial moisture content and the other pertinent physical variables.

Physical properties of earlywood and latewood of Pinus radiata D. Don: Anisotropic shrinkage, equilibrium moisture content and fibre saturation point

Holzforschung ◽  
2005 ◽  
Vol 59 (6) ◽  
pp. 654-661 ◽  
Author(s):  
Shusheng Pang ◽  
Alfred Herritsch
Keyword(s):  
Moisture Content ◽  
Equilibrium Moisture Content ◽  
Pinus Radiata ◽  
Growth Ring ◽  
Fibre Saturation Point ◽  
Longitudinal Shrinkage ◽  
Saturation Point ◽  
Breast Height ◽  
Second Growth ◽  
Tangential Shrinkage

Abstract Anisotropic shrinkage (tangential and longitudinal), equilibrium moisture content (EMC) and fibre saturation point (FSP) were measured for separated earlywood (EW) and latewood (LW) of a 0.75-m-long log of 20-year old Pinus radiata that was cut at breast height from a selected tree in the forest of Central North Island, New Zealand. The experimental results have shown that at 12% moisture content (MC), tangential shrinkage was 3.23% for EW and 3.90% for LW, with an overall average of 3.56%. Longitudinal shrinkage was 0.23% for EW and 0.21% for LW with an overall average of 0.22%. Shrinkage for the oven dry (OD) state showed similar trends to those at 12% MC in terms of the differences between EW and LW. The tangential and longitudinal shrinkage varied significantly along the radius from pith to bark. The EW tangential shrinkage increased from pith to the seventh growth ring and then remained relatively constant until the last ring adjacent to the bark. The LW tangential shrinkage also increased from the pith outwards until the seventh growth ring, but beyond that was more variable than the EW shrinkage. Both EW and LW showed similar longitudinal shrinkage, with the highest values in the second growth ring, from which the shrinkage decreased exponentially towards the bark. LW had a slightly higher EMC than EW at a relative humidity (RH) below 80%, but the trend was reversed for RH above 80%. The EMC differences between EW and LW were less than 0.6%. The overall average FSP for Pinus radiata was 29.1%, with actual values varying from 25% to 32.8%. The earlywood FSP (28.9%) was slightly lower than that of the latewood (29.4%).

scholarly journals Ultrasound Drying of Rose Hips: a Process Study

2020 ◽  
Vol 50 (1) ◽  
pp. 79-86
Author(s):  
Elena Verboloz ◽  
Marina Ivanova ◽  
Vera Demchenko ◽  
Sergey Fartukov ◽  
Nikita Evona
Keyword(s):  
Vitamin C ◽  
Moisture Content ◽  
Quality Indicators ◽  
State Standard ◽  
Raw Materials ◽  
Initial Moisture Content ◽  
Raw Material ◽  
Drying Process ◽  
Resource Saving ◽  
Drying Time

Introduction. Rose hips are rich in macro- and micronutrients. Unfortunately, heat treatment destroys most nutrients. Ultrasonic technologies make it possible to reduce the drying time and lower the temperature regime. The research objective was to adjust ultrasound technology to rose hip production in order to reduce the loss of vitamins and improve the quality indicators of the dried product. Study objects and methods. The research featured rose hips of the Rosa canina species collected in the south of Kazakhstan. This subspecies of wild rose is poor in vitamin C. Nevertheless, this shrub is extremely common in Russia and other countries of the Commonwealth of Independent States. The raw material was dried according to standard methods. One group of samples was treated with ultrasound, while the other served as control. Both groups underwent a sensory evaluation and were tested for moisture and vitamin C. Results and discussion. The rose hips were dried in a combination steam oven with a built-in ultrasonic wave generator. The research revealed the following optimal parameters of the ultrasound drying process: frequency of ultrasonic vibrations – 22 kHz, processing time – 2.5 h, temperature in the combination steam oven – +56°C, initial moisture content – 30%. The resulting product met the requirements of State Standard. The loss of moisture was 57%. According to State Standard 1994-93, the initial moisture content should be 15% or less. Time decreased from 360 min to 160 min, and the initial moisture was 13%. The experiment confirmed the initial hypothesis that ultrasonic treatment improves the drying process by improving quality indicators and preserving vitamin C in raw materials using. Conclusion. Ultrasound treatment during moisture removal from rose hips provides a resource-saving technology that fulfills an economically and socially important function.

scholarly journals Modelling of biomass temperature in the drying process

2020 ◽  
Vol 154 ◽  
pp. 01004
Author(s):  
Ewa Golisz ◽  
Małgorzata Jaros ◽  
Szymon Głowacki
Keyword(s):  
Moisture Content ◽  
Initial Moisture Content ◽  
Direct Calculation ◽  
Logistic Function ◽  
Temperature Model ◽  
Drying Process ◽  
Drying Time ◽  
Temperature Changes ◽  
Higher Temperature ◽  
Temperature Rate

The goal of the work was to propose and verify the model of temperature changes of the convective dried biomass depending on the drying time. The algebraic temperature model of the convective dried solid, giving the possibility of its direct calculation, was based on the logistic function of growth. Temperature model was verified for convective dried biomass: vegetable and wood (poplar and willow wood chips) significantly differing in initial moisture content. Parameter W in the temperature model, defined as the coefficient of temperature rate changes reaches greater values in higher temperature of drying air and for wood biomass which has lower initial moisture content. Empirically selected parameter W allows to verify the temperature model with the relative error less than 5%.

Testing of the fatigue strength along wood fibres at different moisture contents

2021 ◽  
Vol 115 ◽  
pp. 45-54
Author(s):  
Ewa Dobrowolska ◽  
Mateusz Niedbała ◽  
Daniel Tabaczyński
Keyword(s):  
Fatigue Strength ◽  
Moisture Content ◽  
Maximum Stress ◽  
Fibre Saturation Point ◽  
Pedunculate Oak ◽  
Saturation Point ◽  
Moisture Contents ◽  
Wood Fibres ◽  
Short Term Strength ◽  
Limited Usefulness

Testing of the fatigue strength along wood fibres at different moisture contents. The paper determines the effect of wood moisture content on the fatigue strength in compression along fibres. The method of determining the maximum stress at the proportional limit was used for the measurements. Fatigue strength was investigated for three wood species: pedunculate oak (Quercus robur L.), bearded birch (Betula pendula Roth.) and Norway spruce (Picea abies L.), with two moisture contents: close to the absolutely dry state and above the fibre saturation point. The ratio of fatigue strength to short term strength depends on moisture content and is similar for birch (70.3% in the dry state and 72.1% in the wet state), for oak (67.4% and 69.5% in both states) and for spruce (66.6% in the dry state and 68.1% in the wet state). The moisture content of the wood clearly influences the fatigue strength of the wood. On average, the fatigue strength of wood with moisture contents above the fibre saturation point constitutes about 0.20 of the fatigue strength of wood with moisture contents close to 0%. This tendency was found regardless of the tested species. The simplified method for testing fatigue strength at the limit of proportionality has shown its limited usefulness, requiring further analysis and comparison with other methods in order to be thoroughly tested and possibly improved.

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