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Title: Microwave moisture measurement for wood drying

Abstract

The goal of this project was to develop a prototype moisture sensor system suitable for a hardwood dry kiln based on the microwave transmission measurements of the complex dielectric constant of the wood. In this project, prototypes of two designs of microwave-based moisture sensor probes (launchers) working in the frequency range from 4.5 GHz to 6 GHz were developed and tested. A prototype set of battery powered electronics that both provides the microwave excitation and records the amplitude and phase of the returned signal after passing through the wood was built and tested. The sensors and electronics built in this project allow a swept frequency microwave transmission measurement through a small area of a board. Using the prototype electronics and launchers, measurements of moisture content (MC) over a range of 6 percent to 70 percent MC for red oak and 6 percent to 100 percent for yellow-poplar with standard deviations of less than 1.5 percent MC have been obtained.

Authors:
 [1];  [2];  [2];  [2];  [2]
  1. University of Tennessee, Knoxville (UTK)
  2. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
932167
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Forest Products Journal; Journal Volume: 57; Journal Issue: 10
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; AMPLITUDES; DRYING; EXCITATION; FREQUENCY RANGE; KILNS; MOISTURE; OAKS; PROBES; WOOD

Citation Formats

Moschler, William W, Hanson, Gregory R, Gee, Timothy Felix, Killough, Stephen M, and Wilgen, John B. Microwave moisture measurement for wood drying. United States: N. p., 2007. Web.
Moschler, William W, Hanson, Gregory R, Gee, Timothy Felix, Killough, Stephen M, & Wilgen, John B. Microwave moisture measurement for wood drying. United States.
Moschler, William W, Hanson, Gregory R, Gee, Timothy Felix, Killough, Stephen M, and Wilgen, John B. Mon . "Microwave moisture measurement for wood drying". United States. doi:.
@article{osti_932167,
title = {Microwave moisture measurement for wood drying},
author = {Moschler, William W and Hanson, Gregory R and Gee, Timothy Felix and Killough, Stephen M and Wilgen, John B},
abstractNote = {The goal of this project was to develop a prototype moisture sensor system suitable for a hardwood dry kiln based on the microwave transmission measurements of the complex dielectric constant of the wood. In this project, prototypes of two designs of microwave-based moisture sensor probes (launchers) working in the frequency range from 4.5 GHz to 6 GHz were developed and tested. A prototype set of battery powered electronics that both provides the microwave excitation and records the amplitude and phase of the returned signal after passing through the wood was built and tested. The sensors and electronics built in this project allow a swept frequency microwave transmission measurement through a small area of a board. Using the prototype electronics and launchers, measurements of moisture content (MC) over a range of 6 percent to 70 percent MC for red oak and 6 percent to 100 percent for yellow-poplar with standard deviations of less than 1.5 percent MC have been obtained.},
doi = {},
journal = {Forest Products Journal},
number = 10,
volume = 57,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • A method of determining moisture content (MC) of wood fuel using a microwave oven for drying the wood was evaluated by drying paired samples of five different wood fuel types in a microwave oven and a conventional oven. When compared to the conventional oven drying method, the microwave technique produces consistently lower MC determinations, although the differences are less than 1 percent. The advantage of the microwave technique is the speed at which MC determinations can be determined (less than 15 minutes). Schedules for drying five wood fuel types are presented. (Refs. 7).
  • The goal of this project was to develop a prototype microwave-based moisture sensor system suitable for the kiln drying of hardwood lumber. The moisture sensors developed are battery powered and are capable of communicating with a host kiln control system via spread spectrum wireless communications. We have developed two designs of the sensors working at 4.5 to 6 GHz with linear response to moisture content (MC) over a range of 6-100%. These sensors allow us to make a swept frequency microwave transmission measurement through a small area of a board. Using the prototype electronics and sensors, we have obtained measurementsmore » of MC over the above MC range for red oak and yellow poplar with standard deviations of less than 1.5% MC. We have developed data for board thickness corrections and for temperature corrections for the MC measurement system.« less
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  • A properly designed microwave oven can be a useful instrument for rapid determination of moisture in eight-mesh coal. Accuracy may be limited due to the wide variability of coals and their different behavior when subjected to microwave energy. However, as a technique for screening coal for total moisture content the small sacrifice in accuracy may be more than compensated for by the speed and ease of the test. Test data is recorded for comparison.