Footwear for cold environments. Thermal properties, performance and testing
(1999) In Arbete och hälsa 1999:36 / 1999:23.- Abstract
- Present standard on safety footwear (EN 344) checks the insulation only at one point in the shoes by means of measuring the temperature change. A method that uses thermal foot model allows to measure footwear insulation simultaneously at various locations and for whole footwear as well.
In the present work the method of heated foot model was developed further. It is possible to simulate sweating and evaluate reduction of insulation of footwear due to wetting and evaporative heat loss. The conditions with various sweat rates, wear length and foot motion were tested.
Footwear with various insulation levels (from thin rubber boots to thick winter boots) was evaluated. Some footwear was manufactured both with and without... (More) - Present standard on safety footwear (EN 344) checks the insulation only at one point in the shoes by means of measuring the temperature change. A method that uses thermal foot model allows to measure footwear insulation simultaneously at various locations and for whole footwear as well.
In the present work the method of heated foot model was developed further. It is possible to simulate sweating and evaluate reduction of insulation of footwear due to wetting and evaporative heat loss. The conditions with various sweat rates, wear length and foot motion were tested.
Footwear with various insulation levels (from thin rubber boots to thick winter boots) was evaluated. Some footwear was manufactured both with and without steel toe cap and this allowed to study the thermal effect of steel toe cap in different conditions. Comparative studies between various methods (thermal foot model, humans, EN 344) for evaluating footwear thermal properties/insulation were carried out. Field studies were carried out for evaluation of footwear and feet conditions in real wear situation.
The insulation of footwear can vary depending on region and insulation level of the footwear. Heavy winter boots had lowest insulation in toe zone and thin boots had heel zone as the coldest region. Sweat rates of 3 g/h can reduce footwear insulation considerably (9-19 % depending on initial dry insulation). At higher sweat rates (10 g/h) the reduction could be up to 36 %. Combined effects of sweating, walking and wind could reduce insulation by about 45 %. Reduction was bigger in warm winter boots. Only small amount of moisture evaporates from winter footwear during use. Insulation reduction levelled off over longer periods of use. The reduction can be calculated by simple equations.
The thermal foot model gave similar insulation values as measured on human subjects in thermal comfort. The insulation values were used for validation of a mathematical model for foot skin temperature prediction. The results obtained with a thermal foot model give more useful information on footwear than does the present standard for footwear thermal testing. Thus, the thermal foot method is recommended for use as a standard.
A steel toe cap in a footwear seems to have no influence on insulation, but may modify the heat losses from the foot. The influence could be related to the “after effect” that probably depends on the mass of steel toe cap and its thermal inertia.
Some recommendations for use and choice of footwear are given. (Less) - Abstract (Swedish)
- Abstract in Uncoded languages
Praegune kaitsejalatsite testimise standard (EN 344) kontrollib soojapidavuslikke omadusi vaid jalatsi ühes punktis, mõõtes temperatuuri muutust. Meetod, mis kasutab termilist jala mudelit, võimaldab mõõta jalatsi soojaisolatsiooni üheaegselt erinevates piirkondades ning ühtlasi ka jalatsi kui terviku soojaisolatsiooni.
Selle uurimuse käigus arendati termilise jala meetodit edasi. Meetodiga on võimalik simuleerida higistamist ja hinnata niiskumisest ja aurustumise soojakadudest põhjustatud soojapidavuse vähenemist. Käesoleva töö käigus katsetati erineva higistamiskiiruse ja kestvuse ning liikumise (kõndimine, tuul) mõju saabaste soojatakistusele.
Katsetes kasutati erineva... (More) - Abstract in Uncoded languages
Praegune kaitsejalatsite testimise standard (EN 344) kontrollib soojapidavuslikke omadusi vaid jalatsi ühes punktis, mõõtes temperatuuri muutust. Meetod, mis kasutab termilist jala mudelit, võimaldab mõõta jalatsi soojaisolatsiooni üheaegselt erinevates piirkondades ning ühtlasi ka jalatsi kui terviku soojaisolatsiooni.
Selle uurimuse käigus arendati termilise jala meetodit edasi. Meetodiga on võimalik simuleerida higistamist ja hinnata niiskumisest ja aurustumise soojakadudest põhjustatud soojapidavuse vähenemist. Käesoleva töö käigus katsetati erineva higistamiskiiruse ja kestvuse ning liikumise (kõndimine, tuul) mõju saabaste soojatakistusele.
Katsetes kasutati erineva soojapidavusastmega jalatseid (alates õhukestest kummisaabastest kuni paksude talvesaabasteni). Mõned jalatsid toodeti nii terasvarbakaitsega kui ka ilma selleta ja see võimaldas uurida terasninamiku termilist mõju erinevates tingimustes. Võrreldi erinevaid katsemeetodeid (termiline jala mudel, katseisikud, EN 344), millega on võimalik hinnata/mõõta jalatsite soojuslikke omadusi/soojaisolatsiooni. Jalatseid testiti ka katseisikutega erinevatel keskkonna temperatuuridel. Saadud andmeid kasutati matemaatilises analüüsis jala naha temperatuuride prognoosimiseks. Jalanõude ja jalgade olukorra hindamiseks tegelikes kasutusoludes teostati mõned väliuurimused.
Kaitsejalatsite soojaisolatsioon võib kõikuda sõltuvalt jalatsi piirkonnast ja saapa soojaisolatsiooni astmest. Soojade talvesaabaste kõige nõrgemini soojustatud piirkonnaks olid varbad ja ilma sooja hoidva kihita saabastel oli selleks piirkonnaks kand. Isegi madalad higistamiskiirused (3 g/h) vähendasid tunduvalt jalatsite soojatakistust (9-19 % sõltuvalt algselt kuivalt jalatsilt mõõdetud isolatsioonist). Kõrgemad higistamiskiirused (10 g/h) tõid kaasa kuni 36 % soojatakistuse vähenemise. Soojaisolatsioon võis väheneda umbes 45 %, kui higistamist kombineeriti liikumisega. Kahanemine oli suurem talvesaabaste puhul. Ainult väike kogus niiskust aurustub talvesaabastest kasutamise käigus. Pikema kasutuse käigus isolatsiooni vähenemine tasakaalustub. Isolatsiooniväärtuse kahanemist on võimalik hinnata lihtsate valemite abil.
Termiline jala mudel andis sarnased isolatsiooniväärtused, nagu on mõõdetud soojuslikus tasakaalus olevatel katseisikutel. Neid väärtusi on võimalik kasutada matemaatilistes mudelites. Katsed termilise jala mudeliga annavad rohkem kasulikku teavet kui praegune jõus olev jalatsite termilise katsetamise standard. Seega võib termilise jala meetodit soovitada kasutuseks standardina.
Näib, et terasvarbakaitse mõjutab jala nahatemperatuuri ja muudab soojakadusid jalast. See mõju võib olla seotud “järelmõjuga”, mis tõenäoliselt sõltub teraskaitse massist ja soojainertsist.
Antud on ka soovitusi jalatsite kasutamiseks ja valikuks.
Popular Abstract in Swedish
Nuvarande europeiska standard för test av skyddsskor (EN 344) mäter den termiska isolationen bara i en punkt i skon genom att mäta en temperaturändring. En termisk fotmodell möjliggör mätning av isolationen hos skor både i olika zoner och i hela skon.
I detta forskningsprojektet har metoden med rörlig uppvärmd fotmodell vidare-utvecklas. Metoden kan simulera svettning och bestämma ändring i isolation av skor beroende på fukt och värmeförlust genom avdunstning. Betingelser med olika svettningsgrad, mättid och simulerad gång testades.
I projektet undersöktes stövlar med olika isoleringsnivåer (från tunna gummistövlar till tjocka vinterstövlar). Några av stövlarna var tillverkade båda med och utan stålhätta och den termiska påverkan av stålhättan under olika betingelser studerades. Jämförande studier mellan olika metoder genomfördes (termisk fotmodell, EN 344, mätningar på människor). För att bedöma termiska egenskaper hos stövlar användes data från försökspersoner och fotmodell tillsammans. En matematisk modell provades för att förutsäga hud temperaturen på foten. Fältstudier genomfördes för att värdera stövlarnas klimatskydd under verkliga förhållanden.
Skodelarna hade olika isolation beroende främst på tjocklek och material. Varma vinterstövlar hade den lägsta isolation vid tårna medan den kallaste delen av gummistövlar var hälen. Även en låg svettningshastighet (3 g/h) minskade isolationen hos alla stövlar (9-19 % jämfört med den ursprungliga torra isolationen). Vid högre svettningshastighet (10 g/h) minskade isolationen med upp till 36 %. I kombination med svettning, rörelse och vind kunde isolationen hos stövlar minska ca 45 %. Minskningen var störst i vinterstövlar. Isolationsförändringen var stor under de första 2 timmarna av 8-timmars mätning, men blev betydligt mindre efter hand. Avdunstningen var generellt mycket liten från vinterstövlar. Enkla samband för att beräkna isolationsminskningen har utarbetats.
Den termiska fotmodellen gav lika isolationsvärdena som de som uppmättes på människor vid termisk komfort. Värdena kan användas i matematiska modeller för att förutsäga hud temperaturer, exponeringstider och välja fotbeklädnad. Resultat från försök med termisk fotmodell ger mer användbar information än nuvarande standardmetod för termisk provning av skor. Därför kan termiska fot metoden rekommenderas att användas som standard.
Det förefaller som om stålhättan har en påverkan, om än liten, på fotens hudtemperatur och modifierar värmeförlusterna från foten. Påverkan kan relateras till den s.k. “efter effekten”, vilken troligen beror på ståltåhättans relativt stora massa och termisk tröghet.
Rekommendationer för användning och val av skor gavs slutligen. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/598083
- author
- Kuklane, Kalev LU
- supervisor
- opponent
-
- Docent Anttonen, Hannu, University of Oulu / Oulu Regional Institute of Occupational Health, Finland
- organization
- publishing date
- 1999
- type
- Thesis
- publication status
- published
- subject
- keywords
- thermal insulation, sweating, skin temperature, thermal foot model, thermal responses, pain sensation, boots, footwear, cold, foot
- in
- Arbete och hälsa
- volume
- 1999:36 / 1999:23
- pages
- 89 pages
- publisher
- Luleå University of Technology
- defense location
- Luleå University of Technology
- defense date
- 2000-02-24 13:00:00
- external identifiers
-
- other:ISRN LTU-DT--99/36--SE
- ISSN
- 0346-7821
- ISBN
- 91-7045-540-6
- language
- English
- LU publication?
- no
- id
- 2df9b366-c46c-4adc-b89d-4e67995ba150 (old id 598083)
- alternative location
- http://pure.ltu.se/portal/sv/publications/footwear-for-cold-environments(735277e0-9213-11db-8975-000ea68e967b).html
- http://hdl.handle.net/2077/4207
- date added to LUP
- 2016-04-01 12:12:31
- date last changed
- 2020-05-28 11:48:48
@phdthesis{2df9b366-c46c-4adc-b89d-4e67995ba150,
abstract = {{Present standard on safety footwear (EN 344) checks the insulation only at one point in the shoes by means of measuring the temperature change. A method that uses thermal foot model allows to measure footwear insulation simultaneously at various locations and for whole footwear as well.<br/><br>
In the present work the method of heated foot model was developed further. It is possible to simulate sweating and evaluate reduction of insulation of footwear due to wetting and evaporative heat loss. The conditions with various sweat rates, wear length and foot motion were tested.<br/><br>
Footwear with various insulation levels (from thin rubber boots to thick winter boots) was evaluated. Some footwear was manufactured both with and without steel toe cap and this allowed to study the thermal effect of steel toe cap in different conditions. Comparative studies between various methods (thermal foot model, humans, EN 344) for evaluating footwear thermal properties/insulation were carried out. Field studies were carried out for evaluation of footwear and feet conditions in real wear situation. <br/><br>
The insulation of footwear can vary depending on region and insulation level of the footwear. Heavy winter boots had lowest insulation in toe zone and thin boots had heel zone as the coldest region. Sweat rates of 3 g/h can reduce footwear insulation considerably (9-19 % depending on initial dry insulation). At higher sweat rates (10 g/h) the reduction could be up to 36 %. Combined effects of sweating, walking and wind could reduce insulation by about 45 %. Reduction was bigger in warm winter boots. Only small amount of moisture evaporates from winter footwear during use. Insulation reduction levelled off over longer periods of use. The reduction can be calculated by simple equations.<br/><br>
The thermal foot model gave similar insulation values as measured on human subjects in thermal comfort. The insulation values were used for validation of a mathematical model for foot skin temperature prediction. The results obtained with a thermal foot model give more useful information on footwear than does the present standard for footwear thermal testing. Thus, the thermal foot method is recommended for use as a standard.<br/><br>
A steel toe cap in a footwear seems to have no influence on insulation, but may modify the heat losses from the foot. The influence could be related to the “after effect” that probably depends on the mass of steel toe cap and its thermal inertia.<br/><br>
Some recommendations for use and choice of footwear are given.}},
author = {{Kuklane, Kalev}},
isbn = {{91-7045-540-6}},
issn = {{0346-7821}},
keywords = {{thermal insulation; sweating; skin temperature; thermal foot model; thermal responses; pain sensation; boots; footwear; cold; foot}},
language = {{eng}},
publisher = {{Luleå University of Technology}},
series = {{Arbete och hälsa}},
title = {{Footwear for cold environments. Thermal properties, performance and testing}},
url = {{http://pure.ltu.se/portal/sv/publications/footwear-for-cold-environments(735277e0-9213-11db-8975-000ea68e967b).html}},
volume = {{1999:36 / 1999:23}},
year = {{1999}},
}