| 1. |
- Broede, Peter, et al.
(författare)
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The Universal Thermal Climate Index UTCI Compared to Ergonomics Standards for Assessing the Thermal Environment
- 2013
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Ingår i: Industrial Health. - 1880-8026. ; 51:1, s. 16-24
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Forskningsöversikt (refereegranskat)abstract
- The growing need for valid assessment procedures of the outdoor thermal environment in the fields of public weather services, public health systems, urban planning, tourism & recreation and climate impact research raised the idea to develop the Universal Thermal Climate Index UTCI based on the most recent scientific progress both in thermo-physiology and in heat exchange theory. Following extensive validation of accessible models of human thermoregulation, the advanced multi-node 'Fiala' model was selected to form the basis of UTCI. This model was coupled with an adaptive clothing model which considers clothing habits by the general urban population and behavioral changes in clothing insulation related to actual environmental temperature. UTCI was developed conceptually as an equivalent temperature. Thus, for any combination of air temperature, wind, radiation, and humidity, UTCI is defined as the air temperature in the reference condition which would elicit the same dynamic response of the physiological model. This review analyses the sensitivity of UTCI to humidity and radiation in the heat and to wind in the cold and compares the results with observational studies and internationally standardized assessment procedures. The capabilities, restrictions and potential future extensions of UTCI are discussed.
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| 2. |
- Bröde, Peter, et al.
(författare)
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Deriving the operational procedure for the Universal Thermal Climate Index (UTCI)
- 2012
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Ingår i: International Journal of Biometeorology. - : Springer Science and Business Media LLC. - 1432-1254 .- 0020-7128. ; 56:3, s. 481-494
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Tidskriftsartikel (refereegranskat)abstract
- The Universal Thermal Climate Index (UTCI) aimed for a one-dimensional quantity adequately reflecting the human physiological reaction to the multi-dimensionally defined actual outdoor thermal environment. The human reaction was simulated by the UTCI-Fiala multi-node model of human thermoregulation, which was integrated with an adaptive clothing model. Following the concept of an equivalent temperature, UTCI for a given combination of wind speed, radiation, humidity and air temperature was defined as the air temperature of the reference environment, which according to the model produces an equivalent dynamic physiological response. Operationalising this concept involved (1) the definition of a reference environment with 50% relative humidity (but vapour pressure capped at 20 hPa), with calm air and radiant temperature equalling air temperature and (2) the development of a one-dimensional representation of the multivariate model output at different exposure times. The latter was achieved by principal component analyses showing that the linear combination of 7 parameters of thermophysiological strain (core, mean and facial skin temperatures, sweat production, skin wettedness, skin blood flow, shivering) after 30 and 120 min exposure time accounted for two-thirds of the total variation in the multi-dimensional dynamic physiological response. The operational procedure was completed by a scale categorising UTCI equivalent temperature values in terms of thermal stress, and by providing simplified routines for fast but sufficiently accurate calculation, which included look-up tables of pre-calculated UTCI values for a grid of all relevant combinations of climate parameters and polynomial regression equations predicting UTCI over the same grid. The analyses of the sensitivity of UTCI to humidity, radiation and wind speed showed plausible reactions in the heat as well as in the cold, and indicate that UTCI may in this regard be universally useable in the major areas of research and application in human biometeorology.
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| 3. |
- Bröde, Peter, et al.
(författare)
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Heat gain from thermal radiation through protective clothing with different insulation, reflectivity and vapour permeability
- 2010
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Ingår i: International Journal of Occupational Safety and Ergonomics. - 2376-9130. ; 16:2, s. 231-244
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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.
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| 4. |
- 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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| 5. |
- 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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| 6. |
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| 7. |
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| 8. |
- Gao, Chuansi, et al.
(författare)
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Personal cooling with phase change materials to improve thermal comfort from a heat wave perspective
- 2012
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Ingår i: Indoor Air. - : Hindawi Limited. - 0905-6947. ; 22:6, s. 523-530
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedAbstract The impact of heat waves arising from climate change on human health is predicted to be profound. It is important to be prepared with various preventive measures for such impacts on society. The objective of this study was to investigate whether personal cooling with phase change materials (PCM) could improve thermal comfort in simulated office work at 34°C. Cooling vests with PCM were measured on a thermal manikin before studies on human subjects. Eight male subjects participated in the study in a climatic chamber (T(a) = 34°C, RH = 60%, and ν(a) = 0.4 m/s). Results showed that the cooling effect on the manikin torso was 29.1 W/m(2) in the isothermal condition. The results on the manikin using a constant heating power mode reflect directly the local cooling effect on subjects. The results on the subjects showed that the torso skin temperature decreased by about 2-3°C and remained at 33.3°C. Both whole body and torso thermal sensations were improved. The findings indicate that the personal cooling with PCM can be used as an option to improve thermal comfort for office workers without air conditioning and may be used for vulnerable groups, such as elderly people, when confronted with heat waves. PRACTICAL IMPLICATIONS: Wearable personal cooling integrated with phase change materials has the advantage of cooling human body's micro-environment in contrast to stationary personalized cooling and entire room or building cooling, thus providing greater mobility and helping to save energy. In places where air conditioning is not usually used, this personal cooling method can be used as a preventive measure when confronted with heat waves for office workers, vulnerable populations such as the elderly and disabled people, people with chronic diseases, and for use at home.
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| 9. |
- Gao, Chuansi, et al.
(författare)
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Thermoregulatory manikins are desirable for evaluations of intelligent clothing and smart textiles
- 2010
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Ingår i: 8I3M : Eighth International Meeting for Manikins and Modeling : Victoria, BC, Canada, August 22-26, 2010 - Eighth International Meeting for Manikins and Modeling : Victoria, BC, Canada, August 22-26, 2010.
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Konferensbidrag (refereegranskat)abstract
- Thermal manikins have been used to measure thermal properties of clothing. The use of thermal manikins has made a step forward in terms of quantifying thermal properties of clothing in a 3-D manner compared with the use of hotplates for material testing. The effects of clothing properties measured on the thermal manikins under steady state (constant manikin surface temperature and constant environmental condition) have usually to be validated by human subject tests. The thermal insulation and evaporative resistance values measured in the constant conditions are also used in modeling to calculate heat balance, predict human thermal physiological responses, and thermal comfort. However, in many real life situations, clothing properties (e.g. moisture transfer), in particular the clothing properties with smart materials, e.g. phase change materials (PCMs), environmental conditions, sweating rate, skin temperatures are neither constant nor uniform. These make mathematical modeling complicated to take into account various transient, non-uniform conditions, and changeable properties of smart clothing which is becoming increasingly popular (Tang and Stylios 2006). Moreover, skin and core temperatures rather than heat loss or storage are commonly used to evaluate thermal comfort, define hypothermia and hyperthermia and evaluate heat strain. Therefore, the direct prediction of thermophysiological responses (skin and core temperatures) based on manikin measurements are valid (Psikuta and Rossi 2009), and could be considered another step forward towards direct evaluation of human-clothing-thermal environment interactions. In the case of measuring a personal cooling system, current standard specifies the measurement of the average heat removal rate from a sweating heated manikin (ASTM F2371-10). This heat removal rate is not constant for the PCMs. The objective of this study was to investigate the gap between the measured heat removal rate of smart clothing with PCMs obtained on a thermal manikin in a stable state, and clothing effects on local human skin and on core temperature, to compare the difference of the results obtained from both methods, and to highlight the need for developing intelligent thermoregulatory manikins.
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| 10. |
- Ghaddar, Nesreen, et al.
(författare)
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Experimental and Theoretical Study of Ventilation and Heat Loss From Isothermally Heated Clothed Vertical Cylinder in Uniform Flow Field
- 2010
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Ingår i: Journal of Applied Mechanics. - : ASME International. - 0021-8936 .- 1528-9036. ; 77:3
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Tidskriftsartikel (refereegranskat)abstract
- The flow characteristics and heat transfer are studied in a vertical annulus of a heated cylinder surrounded by a permeable cylinder, subject to cross uniform wind with open end to the environment and in the presence of natural convection. The objective here is to develop a computationally efficient model capable of capturing the physics of the flow and heat transport to predict air renewal rates in the vertical annulus. The small quantities of air infiltrating/exfiltrating through the porous cylinder over its upstream/downstream regions do not substantially affect the external flow pattern around the clothed cylinder. The air annulus flow and heat transport model predicted the radial and vertical mass fluxes and the mass flow rate at the opening as a function of environment conditions, porous cylinder thermal properties, wind speed, and annulus geometry. Experiments were performed in a low speed wind tunnel (0.5-5 m/s), in which an isothermally heated vertical cylinder surrounded by a clothed outer cylinder was placed in uniform cross wind. The tracer gas method is used to predict total ventilation flow rates through the fabric and the opening. Good agreement was found between the model and experimental measurements of air renewal rate and predicted heat loss from the inner cylinder at steady conditions. A parametric study is performed to study the effect of wind speed and temperature difference between the wind and skin temperature on induced ventilation through the clothing and the opening. It is found that natural convection enhances ventilation of the annulus air at wind speed, less than 3 m/s, while at higher speeds, natural convection effect is negligible. As the temperature difference between external wind and inner cylinder surface increases, the vertical air temperature gradient and total upward airflow through the opening increase.
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