Insulation reduction of footwear: 1-day sweating test on a thermal foot model
Författare
Summary, in English
The present paper is discussing some results of the bigger experiment that was conducted in order to study the effect of different sweat rates (3, 5 and 10 g/h) on footwear insulation. During the study series some tests with 8-hour sweating were carried out. A thermal foot model was used for testing. The model is divided into 8 zones and had 5 “sweat glands”. A thin sock was donned on foot model for better water distribution. The flow rate to the five “sweat glands” corresponded to 5 g/h, i.e. 40 g per day in total. The test lasted for 12 hours: 1 hour to stabilise the heat losses in the beginning of the test, 8 hours for wet tests and 3 hours for dry test in the end. The last 3 hours were added to see what happens when water distribution is stopped.
The footwear was chosen to cover a wide range of insulation levels from thin rubber boot to winter boot for extreme cold. Each boot had its own sock of the same type. Footwear was weighed before the test, after 8 hours of wet measurements and at the end. Data from the last 10 minutes of each half hour was used for the insulation calculation.
It appeared that the insulation change within the first 1.5 hours corresponded to most of the total reduction during the 8-hour sweating in warm winter boots. The next 6.5 hours reduced the insulation only 4-5 % more in WS and 8-9 % in SM. The insulation reduction levelled off in the long test. This indicates that a balance was reached between the water supply and the evaporation and water transport. In the rubber boot BS this balance was not reached. BS had not much capacity to absorb and transport the water further from the foot. The sock became more wet and favoured further cooling. Even when sweating was stopped the insulation did not improve much. From this point of view the leather boot functioned much better. The winter footwear and the leather boot gained back a considerable amount of insulation within the 3 hours of dry measurements. The water was absorbed and transported further away from the foot. The sock became relatively dry. This demonstrates the importance of keeping the layers near body dry. Although, the amount of water in the boot was still relatively high, for example, 36.6 g in WS, the total insulation at 11th hour was only 7.5 % lower than dry insulation. This suggests that changing socks after heavy activity can be an effective way to keep feet warm over the day.
The morning after the long test, the footwear was weighed again. The most moisture was left in a winter boot WS. Considering the slow drying of WS, it could be recommended to use special shoe dryers. Otherwise, the water collection by the end of the work week could become quite high. That would in worst case make the socks wet already when donning the footwear.
The footwear was chosen to cover a wide range of insulation levels from thin rubber boot to winter boot for extreme cold. Each boot had its own sock of the same type. Footwear was weighed before the test, after 8 hours of wet measurements and at the end. Data from the last 10 minutes of each half hour was used for the insulation calculation.
It appeared that the insulation change within the first 1.5 hours corresponded to most of the total reduction during the 8-hour sweating in warm winter boots. The next 6.5 hours reduced the insulation only 4-5 % more in WS and 8-9 % in SM. The insulation reduction levelled off in the long test. This indicates that a balance was reached between the water supply and the evaporation and water transport. In the rubber boot BS this balance was not reached. BS had not much capacity to absorb and transport the water further from the foot. The sock became more wet and favoured further cooling. Even when sweating was stopped the insulation did not improve much. From this point of view the leather boot functioned much better. The winter footwear and the leather boot gained back a considerable amount of insulation within the 3 hours of dry measurements. The water was absorbed and transported further away from the foot. The sock became relatively dry. This demonstrates the importance of keeping the layers near body dry. Although, the amount of water in the boot was still relatively high, for example, 36.6 g in WS, the total insulation at 11th hour was only 7.5 % lower than dry insulation. This suggests that changing socks after heavy activity can be an effective way to keep feet warm over the day.
The morning after the long test, the footwear was weighed again. The most moisture was left in a winter boot WS. Considering the slow drying of WS, it could be recommended to use special shoe dryers. Otherwise, the water collection by the end of the work week could become quite high. That would in worst case make the socks wet already when donning the footwear.
Publiceringsår
1999
Språk
Engelska
Publikation/Tidskrift/Serie
Kastelli Symposium Living and Working in the North, 24-25 November 1999, Oulo, Finland
Dokumenttyp
Konferensbidrag
Förlag
ORIOH, Finland
Ämne
- Production Engineering, Human Work Science and Ergonomics
Conference name
Kastelli Symposium Living and Working in the North
Conference date
1999-11-24 - 1999-11-25
Conference place
Oulo, Finland
Status
Published
Forskningsgrupp
- Thermal Environment Laboratory