A novel software-based tool to verify and predict heat treatment

times for packaging wood in compliance with ISPM 15

Hugh Evans and Christine Tilbury

Forest ResearchEmily Ho, Jenni Ferrans and Sajid Rafique

BHR Group Limited

ObjectiveTo develop a software tool to optimise the operation of industrial heating chambers to comply with ISPM 15

Wood packaging material should be heated in accordance with a specific time-temperature schedule that achieves a minimum wood core temperature of 56oC for a minimum of 30 minutes

with►confidence ►minimum energy cost►minimum operational time

Heating Chamber Calibration

►specific to timber species, loading and seasonal ambient temperatures:

► Significant air temperature variations within the chamber

► Significant timber temperature variations within the chamber

Current Methods of Verifying Compliance with ISPM 15

►use of thermocouple probes in one or more pieces of wood

►Probe(s) require accurate drilling to place the tip precisely in the core of a piece of wood

►Probe(s) tend to be on the exposed sides of edge pieces; these receive more heat than pieces in the centre of stacked wood

►precise duplication of conditions ►vary with time of year, wood moisture, etc.

Limitations of Current Methods of Verifying Compliance with ISPM 15

► Due to uncertainty, the operators tend to be over-cautious and to use longer heat treatment times as a safety margin

The Role of the Software►Software predicts heating time from basic chamber

parameters including wet bulb temperatures

►Can be used to verify, complement or replace probe measurements

►Useable by chamber operators to:

►verify or predict heat-treatment times

►optimise heat-treatment times to save energy

►optimise chamber throughput to save time

Future Potential Developments►Use in real time control of heating chamber operation

►Installation of CFR 21 part 11capability allowing:

►Secure time stamped encrypted and inviolable data storage

►Electronic storage and transmission of individual chamber performance

►Remote interrogation by authorities of production rates

►Assignment of unique batch bar code allowing traceability of timber during transit

Thermal Diffusion Model into WoodThe core ELASTEQ model uses verified complex algorithms derived during 12 year’s development and use in other industries

► 2-dimensional time-dependent model, based primarily on Fick’s 2nd law of diffusion

► Novel six-noded quadratic triangular elements

► Predicts 1-dimensional or 2 dimensional heat penetration from the outside to the centre of the wood

The Model in Practice► Software uses surface temperature and diffusivity of the wood

as the driving parameters for modelling core temperature

► Wet bulb temperature:► Good indicator of surface temp of wet wood ► Mildly conservative indicator of surface temp of dry wood

► The wet bulb temperature is used as a measure of wood surface temp (with corrections for wood with low moisture content)

► Diffusivity depends on wood density and moisture content

Core Temperature - Wet PineComputed temperature is a good average estimate of wet pine (39 -90% moisture content) based on wet bulb temperature

0

8

16

24

32

40

48

56

64

72

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

time, hr

tem

pera

ture

, C

fastest

slowest

LWetBulb

RWetBulb

computed

Core Temperature - Dry PineComputed temperature is a conservative estimate of dry pine (12 -17% moisture content) based on wet bulb temperature

0

8

16

24

32

40

48

56

64

72

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

time, hr

tem

pera

ture

, C slowest fastestLWetBulbRWetBulbcomputed

Core Temperature - Wet OakComputed temperature is a good estimate of wet oak (54 -65% moisture content) based on wet bulb temperature

0

8

16

24

32

40

48

56

64

72

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5

time, hr

tem

pera

ture

, C fastestslowestLWetBulbRWetBlubcomputed

Data Input

Certification

Certification

Development and Practical Implementation

►Initial use by►chamber operators to check and predict heating times►quarantine staff to check and verify heating times

►First commercial version will be launched after:►Beta testing of the software by potential end users►Final verification in commercial situations

►Register now for a beta version►Contact: enquiries @ timbertherm.com

www.timbertherm.com

The Future► A stand-alone certification tool, employing data from each

HT run► Network integration and encryption for remote

interrogation and international traceability.This requires endorsement/approval by RPPOs and/or IPPC

► Next steps to address this goal:► discussion with RPPOs and IPPC► customise to individual RPPO requirements and local tree

species

Thank you for your attention

Hugh Evans and Christine TilburyForest Research: hugh.evans @ forestry.gsi.gov.uk

Emily Ho, Jenni Ferrans and Sajid RafiqueBHR Group Limited: eho @ bhrgroup.co.uk