SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Holmér Ingvar) ;pers:(den Hartog Emiel)"

Sökning: WFRF:(Holmér Ingvar) > Den Hartog Emiel

  • Resultat 1-10 av 12
  • [1]2Nästa
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Bröde, Peter, et al. (författare)
  • Heat gain from thermal radiation through protective clothing with different insulation, reflectivity and vapour permeability
  • 2010
  • Ingår i: International Journal of Occupational Safety and Ergonomics. ; 16:2, s. 231-244
  • Tidskriftsartikel (refereegranskat)abstract
    • The heat transferred through protective clothing under long wave radiation compared to a reference condition without radiant stress was determined in thermal manikin experiments. The influence of clothing insulation and reflectivity, and the interaction with wind and wet underclothing were considered. Garments with different outer materials and colours and additionally an aluminised reflective suit were combined with different number and types of dry and pre-wetted underwear layers. Under radiant stress, whole body heat loss decreased, i.e., heat gain occurred compared to the reference. This heat gain increased with radiation intensity, and decreased with air velocity and clothing insulation. Except for the reflective outer layer that showed only minimal heat gain over the whole range of radiation intensities, the influence of the outer garments’ material and colour was small with dry clothing. Wetting the underclothing for simulating sweat accumulation, however, caused differing effects with higher heat gain in less permeable garments.
  •  
2.
  • Bröde, Peter, et al. (författare)
  • Heat transfer through protective clothing under symmetric and asymmetric long wave thermal radiation
  • 2008
  • Ingår i: Zeitschrift für Arbeitswissenschaft. ; 62:4, s. 267-276
  • Tidskriftsartikel (refereegranskat)abstract
    • Arbeitskleidung, die zum Schutz vor chemischen, biologischen, mechanischen oder thermischen Gefahrdungen getragen wird, stellt für den Nutzer eine zusatzliche thermische Belastung dar. Zum einen steigern ihr Gewicht und ihre Steifigkeit die metabolische Warmeproduktion wlihrend der Arbeit, gleichzeitig behindern ihre erhöhte Wärmeisolation und ihr Wasserdampfwiderstand die für die Abkühlung des Korpers essentielle Schweissverdunstung. Die Generierung von Daten und Modellen zur adliquaten Beriicksichtigung dieser thermischen Eigenschaften von Schutzkleidung bei der Bewertung von Klimabelastungen war Gegenstand des von der EU geforderten Projektes THERMPROTECT (G6RD-CT-2002-00846). Heizbare anthropometrische Dummys, sog. Thermopuppen zur standardisierten Messung von Bekleidungsisolation und Wasserdampfwiderstand, wurden zur validen und reliablen Registrierung der Wlirmeabgabe mit Schutzbekleidung unter dem Einfluss von Feuchte und Wärmestrahlung eingesetzt. Dieser Beitrag vergleicht die Korpererwarmung durch symmetrische und asymmetrische langwellige Wärmestrahlung gleicher Strahlungsintensität (279 W/m2) in Relation zu einer Referenzbedingung, in der die mittlere Strahlungstemperatur der Lufttemperatur entsprach, für prototypische Arbeitsbekleidungen mit unterschiedlichen Reflexionsgraden und Wärmeisolationen. Mit einer Thermopuppe, bei der die unbekleideten Hände, Füsse und der Kopf durch Aluminiumfolie gegen die Strahlung abgeschirmt waren, wurde die Wärmeabgabe für Oberbekleidungen aus Baumwolle und schwer entflamrnbarer Aramidfaser (Nomex®) in verschiedenen Farben sowie für einen mit Aluminium beschichteten reflektierenden Anzug ermittelt. Die Messungen erfolgten mit einer Polypropylen- sowie einer Woll-Unterwasche, wodurch eine Variation der intrinsischen Wärmeisolation der Gesamtbekleidung zwischen 1.1 und 1.6 clo erzielt wurde. Um neben dem trockenen, d. h. dem kombinierten konvektiven, konduktiven und radiativen Wärmefluss auch die Evaporation zu beriicksichtigen, wurden zusatzliche Versuche mit befeuchteter Woll-Unterwlische durchgefiihrt. Die Erwarmung der Thermopuppe durch Wärmestrahlung wurde als Differenz der unter der Referenz- und Wärmestrahlungsbedingung gemessenen Wärmeabgabe für die gesamte bekleidete Oberflache sowie einzelne Korperareale berechnet. Die auf die Gesamtflache bezogene Erwärmung durch Wärmestrahlung fiel mit der stlirker isolierenden Unterwäsche geringer aus und war sowohl für den rein trockenen als auch für den mit Evaporation gekoppelten Wärmeaustausch von der Strahlungsasymrnetrie unbeeinflusst. Jedoch wurden bei vorwiegend frontal oder lateral applizierter Strahlung an den hauptsachlich exponierten Korperstellen grossere Erwärmungen und Oberflachentemperaturen registriert. Praktische Relevanz Den Ergebnissen zufolge kann in Situationen, in denen die physiologische Beanspruchung beim Tragen von Schutzkleidung unter Wärmestrahlungsbelastung mit Wärmebilanzmodellen bewertet werden soll, die horizontale Verteilung der Strahlungsintensitat vernachlassigt werden. Dagegen sollten Strahlungsasymrnetrien und die Hauptwärmequelle bei möglichen Beeintrachtigungen des thermischen Komforts sowie zur Beurteilung des Risikos für Schrnerzempfindungen oder Verbrennungen auf der Haut beriicksichtigt werden.
  •  
3.
4.
  • Bröde, Peter, et al. (författare)
  • Non-evaporative effects of a wet mid layer on heat transfer through protective clothing
  • 2008
  • Ingår i: European Journal of Applied Physiology. - Springer Berlin / Heidelberg. - 1439-6327 .- 1439-6319. ; 104:2, s. 341-349
  • 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.
5.
6.
  • Havenith, George, et al. (författare)
  • Apparent latent heat of evaporation from clothing: attenuation and “heat pipe” effects
  • 2008
  • Ingår i: Journal of Applied Physiology. - The American Physiological Society. - 8750-7587. ; 104:1, s. 142-149
  • Tidskriftsartikel (refereegranskat)abstract
    • Investigating claims that a clothed person’s mass loss does not always represent their evaporative heat loss (EVAP), a thermal manikin study was performed measuring heat balance components in more detail than human studies would permit. Using clothing with different levels of vapor permeability and measuring heat losses from skin controlled at 34°C in ambient temperatures of 10, 20, and 34°C with constant vapor pressure (1 kPa), additional heat losses from wet skin compared with dry skin were analyzed. EVAP based on mass loss (Emass) measurement and direct measurement of the extra heat loss by the manikin due to wet skin (Eapp) were compared. A clear discrepancy was observed. Emass overestimated Eapp in warm environments, and both under and overestimations were observed in cool environments, depending on the clothing vapor permeability. At 34°C, apparent latent heat ((lambda)app) of pure evaporative cooling was lower than the physical value ((lambda); 2,430 J/g) and reduced with increasing vapor resistance up to 45%. At lower temperatures, (lambda)app increases due to additional skin heat loss via evaporation of moisture that condenses inside the clothing, analogous to a heat pipe. For impermeable clothing, (lambda)app even exceeds (lambda) by four times that value at 10°C. These findings demonstrate that the traditional way of calculating evaporative heat loss of a clothed person can lead to substantial errors, especially for clothing with low permeability, which can be positive or negative, depending on the climate and clothing type. The model presented explains human subject data on EVAP that previously seemed contradictive.
7.
  • Havenith, George, et al. (författare)
  • Evaporative Cooling: effective latent heat of evaporation in relation to evaporation distance from the skin
  • 2013
  • Ingår i: Journal of Applied Physiology. - American Physiological Society. - 8750-7587. ; 114:6, s. 778-785
  • Tidskriftsartikel (refereegranskat)abstract
    • Calculation of evaporative heat loss is essential to heat balance calculations. Despite recognition that the value for latent heat of evaporation, used in these calculations, may not always reflect the real cooling benefit to the body, only limited quantitative data on this is available which has found little use in recent literature. In this experiment a thermal manikin (MTNW, Seattle) was used to determine the effective cooling power of moisture evaporation. The manikin measures both heat loss and mass loss independently allowing a direct calculation of an effective latent heat of evaporation (λeff). The location of the evaporation was varied: from the skin or from the underwear or from the outerwear. Outerwear of different permeabilities was used and different numbers of layers were used. Tests took place in 20ºC, 0.5 m.s-1 at different humidities and were performed both dry and with a wet layer allowing the breakdown of heat loss in dry and evaporative components. For evaporation from the skin λeff is close to the theoretical value (2430J.g-1), but starts to drop when more clothing is worn, e.g. by 11% for underwear and permeable coverall. When evaporation is from the underwear, λeff reduction is 28% wearing a permeable outer. When evaporation is from the outermost layer only, the reduction exceeds 62% (no base-layer) increasing towards 80% with more layers between skin and wet outerwear. In semi- and impermeable outerwear the added effect of condensation in the clothing opposes this effect. A general formula for the calculation of λeff was developed.
8.
9.
  • Kuklane, Kalev, et al. (författare)
  • Calculation of Clothing Insulation by Serial and Parallel Methods: Effects on Clothing Choice by IREQ and Thermal Responses in the Cold
  • 2007
  • Ingår i: International Journal of Occupational Safety and Ergonomics. - Central Institute for Labour Protection, Warszawa, Poland. - 1080-3548. ; 13:2, s. 103-116
  • Tidskriftsartikel (refereegranskat)abstract
    • Cold protective clothing was studied in 2 European Union projects. The objectives were (a) to examine different insulation calculation methods as measured on a manikin (serial or parallel), for the prediction of cold stress (IREQ); (b) to consider the effects of cold protective clothing on metabolic rate; (c) to evaluate the movement and wind correction of clothing insulation values. Tests were carried out on 8 subjects. The results showed the possibility of incorporating the effect of increases in metabolic rate values due to thick cold protective clothing into the IREQ model. Using the higher thermal insulation value from the serial method in the IREQ prediction, would lead to unacceptable cooling of the users. Thus, only the parallel insulation calculation method in EN 342:2004 should be used. The wind and motion correction equation (No. 2) gave realistic values for total resultant insulation; dynamic testing according to EN 342:2004 may be omitted.
  •  
10.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-10 av 12
  • [1]2Nästa
 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy