Tag Archives: moisture content.

1094–1100 Č. Mizera,, D. Herák and P. Hrabě
Mathematical model describing the drying curves of false banana´s fibre (Ensete ventricosum)
Abstract |
Full text PDF (294 kB)

Mathematical model describing the drying curves of false banana´s fibre (Ensete ventricosum)

Č. Mizera¹,*, D. Herák² and P. Hrabě³

¹,² Czech University of Life Sciences Prague, Faculty of Engineering, Department of Mechanical Engineering, Kamýcká 129, CZ165 21 Praha 6 Suchdol, Czech Republic
³ Czech University of Life Sciences Prague, Faculty of Engineering, Department of Material Science and Manufacturing Technology, Kamýcká 129, CZ165 21 Praha 6 Suchdol, Czech Republic
*Correspondence: mizera@tf.czu.cz

Abstract:

Drying processes play an important role in the preservation of agricultural products. They are defined as a process of moisture removal due to simultaneous heat and mass transfer. This study was focused on the analysis of drying curves of fibres of false banana (Ensete ventricosum). The fibres of Ensete ventricosum, originally from Ethiopian region Hawasa, were used in this experiment. Moisture content of freshly harvested fibres Mc =78.4 ± 1.4 % (w.b.) were determined. The fibres were dried at different air temperatures Td =40, 60, 80 and 100 ± 1 °C. To determine the drying curves the drying moisture balance (Radwag, MA 50.R, Poland) was used. Measured data were analysed by computer software Mathcad 14. Experimental drying curves at different temperatures and drying rate were determined. Basic mathematical model describing the loss of mass by drying of the Ensete fibres was represented. The model coefficients were statistically significant suggesting that the determined model could be used as a background for further research focused on Ensete fibre application.

Key words:

, ,




124-129 J. Lev
Sensitivity of capacitive throughput sensor to the change of material relative permittivity
Abstract |
Full text PDF (487 kB)

Sensitivity of capacitive throughput sensor to the change of material relative permittivity

J. Lev

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Physics, Kamýcká 129, 165 21 Prague 6 Suchdol, Czech Republic; e-mail: jlev@tf.czu.cz

Abstract:

The capacitive throughput sensors have been tested in many applications (e.g. the throughput measurement of potatoes, sugar beet, chopped maize and hops). The results showed that the capacitive throughput sensors can be very perspective in some cases. The capacitive sensor for the throughput measurement can be described as a parallel plate capacitor where the dielectric is a mixture of air and the measured material. The equivalent dielectric constant increases with the increasing thickness of the material layer between the plates and the electric capacitance of the capacitor is increasing as well. The thickness of the material layer between the plates can be then determined via the electrical capacitance measurement. The main goal of this work is to describe the relationship between the relative permittivity of the material and the sensor output. The sensor values output directly depend on the sensor impedance and it is influenced by the electric field between the electrodes. The electric field is most influenced by the dielectric properties of the material and the distribution of the material. It was found that the influence of the relative permittivity change is significant only for less values (approximately 10 and less). These results mean that the material with the higher relative permittivity is useful for the capacitive throughput sensor. Also this behaviour can explain why the influence of the moisture is less significant for the moister material, because moister materials have higher relative permittivity.

Key words:

, ,




505-512 J. Papez and P. Kic
Wood moisture of rural timber constructions
Abstract |
Full text PDF (191 kB)

Wood moisture of rural timber constructions

J. Papez and P. Kic*

Czech University of Life Sciences Prague, Faculty of Engineering,Kamycka 129, 16521, Prague 6, Czech Republic;
*Correspondence: kic@tf.czu.cz

Abstract:

The aim of this paper is to present the methodology of measurement of moisturecontent of wood and show some results of this measurement in application on constructions ofagricultural buildings. Wood moisture can affect the durability of buildings. Measurements arein two different animal houses, which varied in design and implementation of the constructionmaterial (steel-wood and steel with wooden rafters). Both these buildings are relatively new(built in 2001 and 2009). There was measured also an older shed attached to the barn, which hasa storage and protective function. All these buildings are from spruce wood. The measurementwas based on the use of resistive sensor and capacitive sensor. Also determined was thetemperature and humidity of the air.From the results of measurements of tested buildings it is obvious that the moisture of the woodis in direct proportion with the relative humidity of the air. There are different results measuredby capacitive and resistive sensors. The suitability of the sensors for determination of woodmoisture was verified by gravimetric method, that is direct method and the results are veryaccurate. In the case of coniferous wood (especially spruce wood), there can be used withsufficient accuracy a capacitive sensor, which was used in all examined buildings. Key word: animal houses, wood, measurement, moisture content.

Key words:

, , ,




529-532 A. Pasila
Changes, challenges and opportunities in the wood energy supply chain
Abstract |
Full text PDF (136 kB)

Changes, challenges and opportunities in the wood energy supply chain

A. Pasila

Seinäjoki University of Applied Sciences, School of Agriculture and Forestry,Ilmajoentie ⁵²⁵, ⁶0⁸00 Ilmajoki, Finland;
e-mail: antti.pasila@seamk.fi

Abstract:

One of the biggest challenges in using bioenergy has been the problem of logistics;that is how, in many cases, to process and transport these low density and bulky raw materials.Finnish  forestry  technology  is  advanced  and  the  same  machinery  which  is  used  in  timberharvesting is often used in energy wood harvesting.A  change  in  the  forest  industry  has  however  caused  some  new  expectations  concerning  thewood  energy  supply  chain.  One  of  the  basic  requirements  for  woodchips  is  low  moisturecontent. In the transportation of wood chips high moisture content, and therefore a high weight,may limit the carrying capacity of vehicles and roads. Also in syngas and charcoal productiondry raw material is needed to be able to control the combustion process.The reduction of moisture content under natural drying conditions means an extended storagetime. With Finnish climate conditions this normally means a storage period of at least one year.The  various  types  of  energy  wood:  stems,  whole  tree  harvested  stems,  logging  residues  orstumps are piled in storage sites and covered. The raw material is chipped or crushed at theseintermediate storage sites and after that transported to bio-refineries.In  the  measurement  of  the  energy  wood’s  quality  and  quantity  there  are  some  differencescompared  to  timber  measurements.  Normally  the  timber  measurements  are  based  on  solidvolume in cubic metres. The forest harvesters are equipped with on-line measurement systems.This  on-line  measurement  is  more  complicated  to  carry  out  in  the  case  of  energy  wood.Especially difficult are the volume measurements in whole tree and stump harvesting. A newmethod used in the measurement of energy wood is weight.

Key words:

, , , , ,