| 11. |
- Bröde, Peter, et al.
(författare)
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Infrared radiation effects on heat loss measured by a thermal manikin wearing protective clothing
- 2005
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Ingår i: Environmental ergonomics XI : proceedings of the 11th International Conference, 22-26 May, 2005, Ystad, Sweden - proceedings of the 11th International Conference, 22-26 May, 2005, Ystad, Sweden. - 1650-9773. - 9163170620 ; , s. 74-77
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Konferensbidrag (refereegranskat)
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| 12. |
- Bröde, Peter, et al.
(författare)
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Non-evaporative effects of a wet mid layer on heat transfer through protective clothing
- 2008
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 104:2, s. 341-349
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Tidskriftsartikel (refereegranskat)abstract
- In order to assess the non-evaporative components of the reduced thermal insulation of wet clothing, experiments were performed with a manikin and with human subjects in which two layers of underwear separated by an impermeable barrier were worn under an impermeable overgarment at 20 °C, 80% RH and 0.5 ms-1 air velocity. By comparing manikin measurements with dry and wetted mid underwear layer, the increase in heat loss caused by a wet layer kept away from the skin was determined, which turned out to be small (5-6 Wm-2), irrespective of the inner underwear layer being dry or wetted, and was only one third of the evaporative heat loss calculated from weight change, i.e. evaporative cooling efficiency was far below unity. In the experiments with 8 males, each subject participated in two sessions with the mid underwear layer either dry or wetted, where they stood still for the first 30 minutes and then performed treadmill work for 60 minutes. Reduced heat strain due to lower insulation with the wetted mid layer was observed with decreased microclimate and skin temperatures, lowered sweat loss and cardiac strain. Accordingly, total clothing insulation calculated over the walking period from heat balance equations was reduced by 0.02 m2 °C W-1 (16%), while for the standing period the same decrease in insulation, representing 9% reduction only showed up after allowing for the lower evaporative cooling efficiency in the calculations. As evaporation to the environment and inside the clothing was restricted, the observed small alterations may be attributed to the wet mid layer’s increased conductivity, which, however, appears to be of minor importance compared to the evaporative effects in the assessment of the thermal properties of wet clothing.
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Gao, Chuansi, et al.
(författare)
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Cooling vests with phase change material packs: the effects of temperature gradient, mass, and covering area
- 2010
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Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 53:5, s. 716-723
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Tidskriftsartikel (refereegranskat)abstract
- Phase change material (PCM) absorbs or releases latent heat when it changes phases, making thermal-regulated clothing possible. The objective of this study was to quantify the relationships between PCM cooling rate and temperature gradient, mass, and covering area on a thermal manikin in a climatic chamber. Three melting temperatures (24, 28, 32 °C) of the PCMs, different mass, covering areas, and two manikin temperatures (34 and 38 °C) were used. The results showed that the cooling rate of the PCM vests tested is positively correlated with the temperature gradient between the thermal manikin and the melting temperature of the PCMs. The required temperature gradient is suggested to be greater than 6 °C when PCM vests are used in hot climates. With the same temperature gradient, the cooling rate is mainly determined by the covering area. The duration of the cooling effect is dependent on PCM mass and the latent heat
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| 17. |
- Gao, Chuansi, et al.
(författare)
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Cooling vests with phase change materials: the effects of melting temperature on heat strain alleviation in an extremely hot environment
- 2011
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 111:6, s. 1207-1216
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Tidskriftsartikel (refereegranskat)abstract
- A previous study by the authors using a heated thermal manikin showed that the cooling rates of phase change material (PCM) are dependent on temperature gradient, mass, and covering area. The objective of this study was to investigate if the cooling effects of the temperature gradient observed on a thermal manikin could be validated on human subjects in extreme heat. The subjects wore cooling vests with PCMs at two melting temperatures (24 and 28°C) and fire-fighting clothing and equipment, thus forming three test groups (vest24, vest28 and control group without the vest). They walked on a treadmill at a speed of 5 km/h in a climatic chamber (air temperature = 55°C, relative humidity = 30%, vapour pressure = 4,725 Pa, and air velocity = 0.4 m/s). The results showed that the PCM vest with a lower melting temperature (24°C) has a stronger cooling effect on the torso and mean skin temperatures than that with a higher melting temperature (28°C). Both PCM vests mitigate peak core temperature increase during the resting recovery period. The two PCM vests tested, however, had no significant effect on the alleviation of core temperature increase during exercise in the heat. To study the possibility of effective cooling of core temperature, cooling garments with PCMs at even lower melting temperatures (e.g. 15°C) and a larger covering area should be investigated.
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| 18. |
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| 19. |
- Gao, Chuansi, et al.
(författare)
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Gait muscle activity during walking on an inclined icy surface
- 2008
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Ingår i: Industrial Health. - : National Institute of Industrial Health. - 1880-8026 .- 0019-8366. ; 46:1, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to explain the contribution of lower extremity muscle activity to gait kinetic and kinematic adaptations for maintaining gait dynamic balance when walking on an inclined icy surface and the biomechanical mechanisms used to counteract slip risk. A two-way factorial experimental design was applied. The two independent variables were the walkway surface (ice and treadmill) and the walkway inclination (0º, 6º, 8º). The dependent variable was the amplitude of the surface EMG of four right lower extremity muscles (tibialis anterior TA, gastrocnemius lateralis GL, rectus femoris RF, and biceps femoris BF). Twelve healthy subjects (7 males and 5 females) participated in the walking trials. A two-way ANOVA analysis showed that on the icy surface in the heel contact phase, EMG amplitudes significantly decreased in TA and RF compared to those for the treadmill surface. In the mid-stance phase, the GL muscle activity significantly decreased on ice compared to treadmill and all four muscle activities increased significantly with the inclination. During the toe off phase, GL and RF activities increased with the inclination. The mechanisms identified may be applied to develop intervention, rehabilitation and training techniques, and to improve performance in human locomotion, such as for winter sports.
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| 20. |
- Gao, Chuansi, et al.
(författare)
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Initial, transient and steady state evaporative resistance of impermeable protective clothing
- 2006
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Ingår i: [Host publication title missing]. - 9623675348 ; , s. 253-261
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Konferensbidrag (refereegranskat)abstract
- The measured water vapour resistances of clothing ensembles differ among laboratories particularly for impermeable clothing. Due to the moisture transfer in the clothing ensemble, evaporative heat losses in initial, transient and steady state phases are different. The purpose of this study was to investigate moisture absorption inside underwear and outer layer as a function of time, to quantify the difference of water vapour resistance of protective clothing (impermeable outer layer and cotton underwear) in initial, transient and steady state. Manikin Tore was used by wearing wet ‘skin’ to simulate sweating. The evaporative resistance is found to be more than two times higher in the initial phase than that in the saturation phase. The moisture content is gained exponentially in the clothing ensemble. On the contrary, mass loss directly from the wet skin decreases exponentially. These may partly explain the poor reproducibility while measuring the evaporative resistance of impermeable clothing for a short period.
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