Localised boundary air layer and clothing evaporative resistances for individual body segments

Wang, Faming; Ferraro, Simona Del; Lin, Li Yen; Mayor, Tiago Sotto; Molinaro, Vincenzo; Ribeiro, Miguel; Gao, Chuansi; Kuklane, Kalev; Holmér, Ingvar

doi:10.1080/00140139.2012.668948

Cited by 46 publications

(21 citation statements)

References 29 publications

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“…All measurements were carried out according to ISO 9920 () and ASTM F2370 (). To simulate sweat‐saturated human skin, a widely accepted approach in sweating thermal manikin research is used (Havenith et al., ; Wang et al., ): the torso manikin was dressed in a pre‐wetted stretchable thin knitted fabric “skin” (fabric material: a blend of polyester and wool, fabric area weight: 152 g/m). Two criteria were used to select the fabric “skin”: the “skin” must be highly wicking [the wicking characteristic is quantified by the top and bottom spreading speeds of the fabric using a moisture management tester, a grade of 5 denotes “highly wicking,” i.e., the spreading speed should be >4.0 mm/s; AATCC 195 ()], and it should also be able to contain a certain amount of moisture to ensure a 20‐min steady‐state testing period.…”

Section: Methodsmentioning

confidence: 99%

Real evaporative cooling efficiency of one‐layer tight‐fitting sportswear in a hot environment

Wang

Annaheim

Morrissey

et al. 2013

Scandinavian Med Sci Sports

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Real evaporative cooling efficiency, the ratio of real evaporative heat loss to evaporative cooling potential, is an important parameter to characterize the real cooling benefit for the human body. Previous studies on protective clothing showed that the cooling efficiency decreases with increasing distance between the evaporation locations and the human skin. However, it is still unclear how evaporative cooling efficiency decreases as the moisture is transported from the skin to the clothing layer. In this study, we performed experiments with a sweating torso manikin to mimic three different phases of moisture absorption in one-layer tight-fitting sportswear. Clothing materials Coolmax(®) (CM; INVISTA, Wichita, Kansas, USA; 100%, profiled cross-section polyester fiber), merino wool (MW; 100%), sports wool (SW; 50% wool, 50% polyester), and cotton (CO; 100%) were selected for the study. The results demonstrated that, for the sportswear materials tested, the real evaporative cooling efficiency linearly decreases with the increasing ratio of moisture being transported away from skin surface to clothing layer (adjusted R(2) >0.97). In addition, clothing fabric thickness has a negative effect on the real evaporative cooling efficiency. Clothing CM and SW showed a good ability in maintaining evaporative cooling efficiency. In contrast, clothing MW made from thicker fabric had the worst performance in maintaining evaporative cooling efficiency. It is thus suggested that thin fabric materials such as CM and SW should be used to manufacture one-layer tight-fitting sportswear.

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Section: Methodsmentioning

confidence: 99%

Real evaporative cooling efficiency of one‐layer tight‐fitting sportswear in a hot environment

Wang

Annaheim

Morrissey

et al. 2013

Scandinavian Med Sci Sports

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“…However, in activities implying motion (e.g. walking, running and jumping), the pumping effect caused by the moving body parts (Wang et al 2011(Wang et al , 2012 and by the changing distance between these relative to the clothing originates complex transport processes within and around clothing, which advise further investigation. As the computational power increases over time, it would be interesting to use numerical (CFD-based) approaches like that of the present work to study the influence of the body movement and the pumping effect on the heat and mass that are transported to/from the body.…”

Section: Limitations and Suggestions Of Further Workmentioning

confidence: 99%

Advanced modelling of the transport phenomena across horizontal clothing microclimates with natural convection

et al. 2015

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The ability of clothing to provide protection against external environments is critical for wearer's safety and thermal comfort. It is a function of several factors, such as external environmental conditions, clothing properties and activity level. These factors determine the characteristics of the different microclimates existing inside the clothing which, ultimately, have a key role in the transport processes occurring across clothing. As an effort to understand the effect of transport phenomena in clothing microclimates on the overall heat transport across clothing structures, a numerical approach was used to study the buoyancy-driven heat transfer across horizontal air layers trapped inside air impermeable clothing. The study included both the internal flow occurring inside the microclimate and the external flow occurring outside the clothing layer, in order to analyze the interdependency of these flows in the way heat is transported to/from the body. Two-dimensional simulations were conducted considering different values of microclimate thickness (8, 25 and 52 mm), external air temperature (10, 20 and 30 °C), external air velocity (0.5, 1 and 3 m s(-1)) and emissivity of the clothing inner surface (0.05 and 0.95), which implied Rayleigh numbers in the microclimate spanning 4 orders of magnitude (9 × 10(2)-3 × 10(5)). The convective heat transfer coefficients obtained along the clothing were found to strongly depend on the transport phenomena in the microclimate, in particular when natural convection is the most important transport mechanism. In such scenario, convective coefficients were found to vary in wavy-like manner, depending on the position of the flow vortices in the microclimate. These observations clearly differ from data in the literature for the case of air flow over flat-heated surfaces with constant temperature (which shows monotonic variations of the convective heat transfer coefficients, along the length of the surface). The flow patterns and temperature fields in the microclimates were found to strongly depend on the characteristics of the external boundary layer forming along the clothing and on the distribution of temperature in the clothing. The local heat transfer rates obtained in the microclimate are in marked contrast with those found in the literature for enclosures with constant-temperature active walls. These results stress the importance of coupling the calculation of the internal and the external flows and of the heat transfer convective and radiative components, when analyzing the way heat is transported to/from the body.

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“…Even with sex-and age-free PESs, there is considerable individual variation with the performance of critical job tasks (Tipton et al 2013). Certainly the impact of anthropometric factors on the fit of the clothing would seem relevant to consider as size and fit of clothing can have substantial effects on heat transfer through the PCE (Chen et al 2004;Ueda et al 2006;Wang et al 2012). observed for different work wear that tight clothing fit showed a 6%-31% lower insulation than loose fit.…”

Section: Protective Clothing and Metabolic Ratementioning

confidence: 99%

Protective clothing ensembles and physical employment standards

McLellan¹,

Havenith

2016

Appl. Physiol. Nutr. Metab.

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Physical employment standards (PESs) exist for certain occupational groups that also require the use of protective clothing ensembles (PCEs) during their normal work. This review addresses whether these current PESs appropriately incorporate the physiological burden associated with wearing PCEs during respective tasks. Metabolic heat production increases because of wearing PCE; this increase is greater than that because of simply the weight of the clothing and can vary 2-fold among individuals. This variation negates a simple adjustment to the PES for the effect of the clothing on metabolic rate. As a result, PES testing that only simulates the weight of the clothing and protective equipment does not adequately accommodate this effect. The physiological heat strain associated with the use of PCEs is also not addressed with current PESs. Typically the selection tests of a PES lasts less than 20 min, whereas the requirement for use of PCE in the workplace may approach 1 h before cooling strategies can be employed. One option that might be considered is to construct a heat stress test that requires new recruits and incumbents to work for a predetermined duration while exposed to a warm environmental temperature while wearing the PCE.Key words: uncompensable heat stress, metabolic rate, aerobic fitness, body size, self-contained breathing apparatus, heat tolerance.Résumé : Des normes physiques relatives à l'emploi (« PESs ») s'appliquent pour certains groupes professionnels qui doivent aussi porter un équipement de protection (« PCEs ») durant leur travail normal. Cette analyse documentaire vérifie si les PES prennent bien en compte le fardeau physiologique associé au port du PCE au cours des diverses tâches. La production de chaleur métabolique augmente à cause du port du PCE; cette augmentation est plus grande que celle attribuable au poids seul des vêtements et peut varier du double entre les individus. Cette variation annule la simple conformité aux PES en ce qui concerne les effets des vêtements sur l'activité métabolique. Par conséquent, l'évaluation des PES qui ne simulent que le poids des vêtements et de l'équipement de protection ne prend pas bien en compte cet effet. La contrainte physiologique associée au port des PCE n'est également pas prise en compte dans les PES actuelles. Typiquement, les tests de sélection en fonction des PES durent moins de 20 minutes alors que l'obligation du port du PCE dans le milieu de travail peut durer jusqu'à une heure avant qu'on utilise les stratégies de refroidissement. Une solution serait de développer un test de stress thermique durant lequel les recrues et les employés réguliers devraient travailler durant une période donnée tout en étant exposés à des conditions ambiantes chaudes et en portant le PCE. [Traduit par la Rédaction] Mots-clés : stress thermique négligé, activité métabolique, capacité aérobie, gabarit, appareil respiratoire autonome, tolérance à la chaleur.

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Localised boundary air layer and clothing evaporative resistances for individual body segments

Cited by 46 publications

References 29 publications

Real evaporative cooling efficiency of one‐layer tight‐fitting sportswear in a hot environment

Real evaporative cooling efficiency of one‐layer tight‐fitting sportswear in a hot environment

Advanced modelling of the transport phenomena across horizontal clothing microclimates with natural convection

Protective clothing ensembles and physical employment standards

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