Electrical and Computer Engineering Seminar Series

Joule heating of Pinus radiate logs in the high voltage lab

Speaker

Ryan Van Herel

Institute

Research Engineer, Electric Power Engineering Centre, University of Canterbury

Time & Place

Fri, 15 Sep 2017 14:00:00 NZST in E14, Engineering Core Block

Abstract

New Zealand is particularly affected by the diminished concentration of ozone in the ozone layer above the southern hemisphere. Methyl bromide being an ozone depleting gas is
subject to a moratorium on its release to atmosphere in 2020. The main use of methyl bromide is in fumigation as a phytosanitary treatment of logs for export to other countries. One proposed
replacement technology for fumigation is heat treatment of the logs by direct application of an electric current to the freshly sawn timber. This technique is called Joule heating, and in the
latter half of 2016, Dr. Bill Heffernan, Nurzhan Nursultanov and I were frequently to be seen in the High Voltage lab performing full scale Joule log-heating tests on a batch of 32 export-grade
Pinus radiata logs.

Hazards were successfully managed with a thorough safety plan, which will be intimated briefly in the talk. The raw results of the testing will be presented, explaining the mean temperatures that were achieved. Each temperature point monitored at 32 mm depth exceeded the minimum required temperature at 30 minutes after test, which is 56 degrees Celsius for 30 minutes, according to the International Standard of Phytosanitary Measures No 15 (ISPM 15).

The team collected quite a lot of data, while at the same time refining the models and subsystems that contribute to the control of the Joule-heating technique. The most valuable result to date has been the development and experimental verification of a computational fluid dynamic model of a log undergoing Joule heating, the subject of Nurzhan’s thesis.