Effect of hygroscopic fabrics on wear comfort in the fluctuating microclimate of clothing

1. 1. A new type of simulator for clothing microclimate was designed and constructed.

2. 2. The simulator was designed to simulate the humidity fluctuation of clothing microclimate as observed under light working conditions and to measure the surface temperature of sample fabrics against the skin by means of a radiation thermometer.

3. 3. Knitted fabrics of cotton and polyester, and polyethylene films were used as specimens with different hygroscopicities.

4. 4. The quick rise and fall in the surface temperature of cotton fabric was observed under rapid fluctuations of the microclimate humidity.

5. 5. Under the same humidity fluctuations, the temperature of polyester fabric rose and fell more moderately than that of cotton fabrics, and the temperature of the polyethylene film did not change. When the rate of change in stimulus temperature is higher, the threshold temperature of warm sensation of the skin comes closer to a given adaption temperature.

6. 6. Therefore, the rapid and large changes in the fabric temperature against the skin, which were observed especially for hygroscopic cotton fabric, must affect the thermal comfort of clothing.

Assessment of body mapping sportswear using a manikin operated in constant temperature mode and thermoregulatory model control mode

Regional sweating patterns and body surface temperature differences exist between genders. Traditional sportswear made from one material and/or one fabric structure has a limited ability to provide athletes sufficient local wear comfort. Body mapping sportswear consists of one piece of multiple knit structure fabric or of different fabric pieces that may provide athletes better wear comfort. In this study, the ‘modular’ body mapping sportswear was designed and subsequently assessed on a ‘Newton’ type sweating manikin that operated in both constant temperature mode and thermophysiological model control mode. The performance of the modular body mapping sportswear kit and commercial products were also compared. The results demonstrated that such a modular body mapping sportswear kit can meet multiple wear/thermal comfort requirements in various environmental conditions. All body mapping clothing (BMC) presented limited global thermophysiological benefits for the wearers. Nevertheless, BMC showed evident improvements in adjusting local body heat exchanges and local thermal sensations.     

The Response of Human Thermal Sensation and Its Prediction to Temperature Step-Change (Cool-Neutral-Cool)

This paper reports on studies of the effect of temperature step-change (between a cool and a neutral environment) on human thermal sensation and skin temperature. Experiments with three temperature conditions were carried out in a climate chamber during the period in winter. Twelve subjects participated in the experiments simulating moving inside and outside of rooms or cabins with air conditioning. Skin temperatures and thermal sensation were recorded. Results showed overshoot and asymmetry of TSV due to the step-change. Skin temperature changed immediately when subjects entered a new environment. When moving into a neutral environment from cool, dynamic thermal sensation was in the thermal comfort zone and overshoot was not obvious. Air-conditioning in a transitional area should be considered to limit temperature difference to not more than 5°C to decrease the unacceptability of temperature step-change. The linear relationship between thermal sensation and skin temperature or gradient of skin temperature does not apply in a step-change environment. There is a significant linear correlation between TSV and Q_loss in the transient environment. Heat loss from the human skin surface can be used to predict dynamic thermal sensation instead of the heat transfer of the whole human body.     

Relationship between thermophysiological responses and psychological thermal perception during exercise wearing aerobic wear

This paper studies the relationships among human physiological and psychological thermal and moisture responses in tight-fit aerobic wear. Results showed that both physiological and psychological responses were significantly influenced by time, garment, body location and some of their interactions. Objectively measured skin humidity and moisture sensation at individual locations were highly correlated and significant at p levels of 0.01. Overall clothing comfort may be best described with thermal sensation at outer thigh, humidity at inner thigh. The correlation coefficient of predicted with experimental clothing comfort score was 0.76, and a t-test showed that there was no significant difference between the two data sets.     

Thermal parameters for assessing thermal properties of clothing

1. The thermal parameters for describing clothing were summarized first (i.e., clo and tog unit, permeability index, evaporative transmissibility, permeation efficiency factor, index of water permeability). Their applications were then outlined for the calculation of heat exchange between human body and its environment, and for the prediction of the physiological variables under heat stress conditions.2. Nevertheless, the human body is not frequently exposed under steady-state condition, instead it is subjected to changes in environmental variables, clothing and activity. The transient thermal response of the human-clothing system plays a major role during transients. The heat exchange between the body and the environment may be affected significantly by the dynamic response of the clothing. The thermal comfort property of a clothing system during dynamic conditions should be assessed based on moisture vapor pressure alteration within the clothing, surface temperature of the clothing and heat loss from the body.3. There is a trend to develop overall thermal parameter to describe the transient thermal and moisture transfer properties of clothing system.     

Blood flow fluctuation underneath human forearm skin caused by local thermal stimuli of different fabrics

The aim of this study was to investigate physiological interactions between fabric and the human body via skin and the resultant disturbance to blood flow, which in turn influences the skin temperature and the sensation of warmth and chilliness, thus the feeling of comfort. We focussed on the effects on the forearm skin blood flow by different local physical stimuli from fabrics. The blood flows were examined under three protocols: (1) using fabrics of different fiber types and fiber blending, (2) different surface characteristics of the same fabric and fiber type, and (3) different moisture levels of the same fabric type. A total of five different fabrics were wrapped over the forearm of a female subject at a good health state for test. The fabric samples were preconditioned for 24 h, and the subject sat for 30 min, in both cold and dry ambient conditions (20.5±0.5 °C, 45±5 p.100 RH) to reach equilibrium before testing. The forearm skin blood flow and temperature were recorded by a laser-Doppler flowmeter (DP1T/7-V2) with two probes mounted on both forearms to eliminate any systematic common mode fluctuations. Several conclusions were drawn from our test data. First, the fabric impact on both skin temperature and blood flow can be significant. Also fabric surface characteristics play important role, especially during the transient heat exchange at the beginning of contact. Finally, moisture level in the samples exhibits considerable influences on skin temperature and blood flow, and the higher the moisture level, the longer the duration of the impact.     

Thermal bioclimatic conditions and patterns of behaviour in an urban park in Göteborg,Sweden

People in urban areas frequently use parks for recreation and outdoor activities. Owing to the complexity of the outdoor environment, there have only been a few attempts to understand the effect of the thermal environment on people's use of outdoor spaces. This paper therefore seeks to determine the relationship between the thermal environment, park use and behavioural patterns in an urban area of Sweden. The methods used include structured interviews, unobtrusive observations of the naturally occurring behaviour and simultaneous measurements of thermal comfort variables, i.e., air temperature, air humidity, wind speed and global radiation. The thermal environment is investigated through the mean radiant temperature (T_mrt) and the predicted mean vote (PMV) index. The outcome is compared to the subjective behaviour and thermal sensation of the interviewees. It is found that the thermal environment, access and design are important factors in the use of the park. In order to continue to use the park when the thermal conditions become too cold or too hot for comfort, people improve their comfort conditions by modifying their clothing and by choosing the most supportive thermal opportunities available within the place. The study also shows that psychological aspects such as time of exposure, expectations, experience and perceived control may influence the subjective assessment. Comparison between the thermal sensation of the interviewees and the thermal sensation assessed by the PMV index indicates that steady-state models such as the PMV index may not be appropriate for the assessment of short-term outdoor thermal comfort, mainly because they are unable to analyse transient exposure.     

Climatic controls of the cool human thermal sensation in a summertime onshore wind

 Afternoon observations in summer comparing shoreline with inland atmospheric conditions were made during onshore winds at Victoria, British Columbia, Canada. The onshore wind came from a cool water surface. Mean monthly water temperatures near to shore were between 11 and 11.5° C. The onshore wind brought lower air, ground surface radiant and sky radiant temperatures; lower humidity and greater wind speed. All of these combine to produce a cooler human environment at the shoreline than inland. The relative importance of climatic elements in producing the cooler environment was assessed using sensitivity analyses with eight different human thermal exchange models/indices. Air temperature and wind speed had the greatest effect, followed by ground surface radiant temperature, sky radiant temperature and humidity. Wind speed is the most practical element to consider when trying to maximize human comfort along the shoreline. Received: 9 July 1996 / Revised: 31 March 1997 / Accepted: 14 April 1997     

An experimental study on the effect of humidity on thermal sensations of people in summer

1. 1. The authors propose humidity reduction instead of lowering room temperature in order to reduce cooling syndrome.

2. 2. They conducted experiments with subjects in the rooms, one with controlling humidity to about 40% r.h. and another without humidity control. Air-conditioning system with humidity control has a greater promise in making a comfortable environment, even at the temperature as high as 30°C, in comparison with conventional means using temperature control alone.

3. 3. Relationship of actual mean votes on temperature sensation and comfort sensation with PMV and SET, respectively, suggests that Japanese people might be more sensitive to humidity than Westerners and so different methods from those used in the western countries should be required for human thermal environmental studies with respect to the hot humid summer in Japan.

Climatic breadth of calling behaviour in two widespread Neotropical frogs: Insights from humidity extremes

Climate change is severely altering precipitation regimes at local and global scales, yet the capacity of species to cope with these changes has been insufficiently examined. Amphibians are globally endangered and particularly sensitive to moisture conditions. For mating, most amphibian species rely on calling behaviour, which is a key weather‐dependent trait. Using passive acoustics, we monitored the calling behaviour of two widespread Neotropical frogs in 12 populations located at the humidity extremes but thermal mean of the species distribution. Based on 2,554 hr of recordings over a breeding season, we found that both the aquatic species Pseudis paradoxa and the arboreal species Boana raniceps exhibited calling behaviour at a wide range of relative humidity. Calling humidity was significantly lower in conspecific populations subjected to drier conditions, while calling temperature did not differ between populations or species. Overall, no variation in climatic breadth was observed between large and small choruses, and calling behaviour was scarcely detected during the driest, hottest and coldest potential periods of breeding. Our results showed that calling humidity of the studied species varies according to the precipitation regime, suggesting that widespread Neotropical anurans may have the capacity to exhibit sexual displays in different climatic environments. Regardless of the underlying mechanism (plasticity or local adaptation), which should be determined by common garden experiments, a wide and population‐specific climatic breadth of calling behaviour may assist species to deal with changing humidity conditions. To our knowledge, this is the first study to explore the response capacity of anurans to perform calling behaviour under contrasting precipitation regimes.     

On the effect of soil wetness on thermal stress

A coupled atmosphere-soil model was applied in order to evaluate the impact of soil wetness on human stress in the absence of horizontal gradients in moisture. The results are illustrated and discussed with consideration to various combinations of wind speed and lower level atmospheric moisture during daylight hours with summer weather conditions. A thermal index composed of the air temperature and wet-bulb temperature does not show major changes as a function of variation of soil mosture. When wind speed and solar radiation are also considered, in a more detailed thermal index, relatively wet soil is associated with the optimal thermal comfort.     

Bioengineering of a cellulosic fabric for insecticide delivery via grafted cyclodextrin

beta-Cyclodextrin (beta-CD) can be easily grafted onto cellulosic textiles through covalent bonds. In such a way beta-CD empty cavities provide an efficient tool for entrapping different kinds of hydrophobic molecules on the surface of the fabric and releasing them slowly in time. The capability of cyclodextrins to include hydrophobic molecules such as fragrances, antimicrobial agents, and other chemicals can be then exploited to produce new grafted textiles with peculiar and useful performances. In this work we report the inclusion of two different products, the pyrethroid insecticide permethrin (PERM) and the insect repellent N,N-diethyl-m-toluamide (DEET), into beta-CD molecules grafted on cotton fabric. UV-vis spectrophotometry and thermal analysis confirmed the presence of the guest molecules on the fabric surface. Bioassays were carried out on two mosquito species of medical importance, Aedes aegypti and Anopheles stephensi; knock down effect and mortality were measured using standard World Health Organization (WHO) cone tests. Repellency and irritancy (blood feeding inhibition) were also measured using cage tests and a baited tunnel device. PERM-treated fabrics kept the insecticidal/irritant efficacy even for a long time after the treatment, whereas DEET activity lasted more shortly.     

Thermal comfort of various building layouts with a proposed discomfort index range for tropical climate

Recent years have seen issues related to thermal comfort gaining more momentum in tropical countries. The thermal adaptation and thermal comfort index play a significant role in evaluating the outdoor thermal comfort. In this study, the aim is to capture the thermal sensation of respondents at outdoor environment through questionnaire survey and to determine the discomfort index (DI) to measure the thermal discomfort level. The results indicated that most respondents had thermally accepted the existing environment conditions although they felt slightly warm and hot. A strong correlation between thermal sensation and measured DI was also identified. As a result, a new discomfort index range had been proposed in association with local climate and thermal sensation of occupants to evaluate thermal comfort. The results had proved that the respondents can adapt to a wider range of thermal conditions.Validation of the questionnaire data at Putrajaya was done to prove that the thermal sensation in both Putrajaya and UTM was almost similar since they are located in the same tropical climate region. Hence, a quantitative field study on building layouts was done to facilitate the outdoor human discomfort level based on newly proposed discomfort index range. The results showed that slightly shaded building layouts of type- A and B exhibited higher temperature and discomfort index. The resultant adaptive thermal comfort theory was incorporated into the field studies as well. Finally, the study also showed that the DI values were highly dependent on ambient temperature and relative humidity but had fewer effects for solar radiation intensity.     

基于地面遥感信息与气温的夏玉米土壤水分估算方法

土壤水分是土壤-植被-大气连续体的一个重要组分,是决定陆地生态系统水分状况的关键因子,也是作物的水分供应库.为了估算站点尺度不同深度的土壤水分,基于下垫面能量平衡方程和水分亏缺指数,提出了基于地面遥感信息(归一化植被指数和下垫面温度)和气温估算土壤相对湿度方法.利用2014年中国气象局固城生态与农业气象试验站夏玉米水分控制试验资料验证的结果表明: 该方法可以有效估算不同深度的土壤相对湿度,陆地生态系统的潜在干旱程度即实际蒸散与潜在蒸散之比与不同深度土壤湿度呈显著的线性关系.其中,0～10 cm土层的土壤水分估算精度最高,决定系数达0.90;0～20 cm到0～50 cm土层土壤水分估算的平均相对误差均在15%以内,相对均方根误差均在20%以内.研究结果可为作物的干旱监测与灌溉管理提供参考.     

Confort térmico y el riesgo de infecciones respiratorias en los adultos mayores en la sierra rural del Perú

The objective is to evaluate thermal comfort in the rural highlands of Peru and determine if thermal conditions influence the risk of respiratory infections. The probit regression model is used for this, with the unit of analysis being adults over 60 years of age. The information source is the data from the National Household Survey and the National Service of Meteorology and Hydrology of Peru. In addition, it was possible to monitor the temperature and the interior relative humidity of 4 types of bedrooms with a thermo-hygrometer and compared it with the desired thermal comfort index criterion. The results show that if the air temperature drops on average by one degree (1° C) in the area of residence, the probability of risk of respiratory infections in older adults increases by 0.18, although the relative humidity and the wind speed were not statistically significant at 1% significance level. Finally, the 4 types of bedrooms evaluated lacked the desired thermal comfort and increased the risk of acquiring respiratory infections.     

Production of biologically active non-woven textiles from recycled polyethylene terephthalate

Recently, various studies have focused on the development of multifunctional non-woven polyethylene terephthalate (PT; polyester) textiles. Herein, we introduce multifunctional non-woven polyester fabrics by pad dry curing silver nitrate (AgNO₃) and aniline monomer into plasma-pretreated non-woven PT textile. This creates a nanocomposite layer of silver nanoparticles (AgNPs) and polyaniline (PANi) on the fabric surface. In order to prepare a non-woven fibrous mat, we applied the melt-spinning technique on previously shredded recycled PT plastic waste. On the surface of the cloth, PANi was synthesized by REDOX polymerization of aniline. Due to the oxidative polymerization, the silver ions (Ag⁺) were converted to Ag⁰NPs. PANi acted as a conductor while AgNPs inhibited the growth of microorganisms. Microwave-assisted curing with trimethoxyhexadecylsilane (TMHDS) gave PT textiles with superhydrophobic properties. The morphological studies were performed using Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The stiffness and breathability of finished non-woven PT textile materials were analyzed to establish their comfort levels. Both of Escherichia coli and Staphylococcus aureus were used to test the efficacy of the AgNPs-treated textiles as antimicrobial materials. Moreover, the processed polyester textiles showed excellent electrical conductivity and great ultraviolet-ray blocking.     

Emerging Materials and Strategies for Personal Thermal Management

In this decade, the demands of energy saving and diverse personal thermoregulation requirements along with the emergence of wearable electronics and smart textiles give rise to the resurgence of personal thermal management (PTM) technologies. PTM, including personal cooling, heating, insulation, and thermoregulation, are far more flexible and extensive than the traditional air/liquid cooling garments for the human body. Concomitantly, many new advanced materials and strategies have emerged in this decade, promoting the thermoregulation performance and the wearing comfort of PTM simultaneously. In this review, an overview is presented of the state‐of‐the‐art and the prospects in this burgeoning field. The emerging materials and strategies of PTM are introduced, and classed by their thermal functions. The concept of infrared‐transparent visible‐opaque fabric (ITVOF) is first highlighted, as it triggers the work on advanced PTM by combining it with radiative cooling, and the corresponding implementations and realizations are subsequently introduced, followed by wearable heaters, flexible thermoelectric devices, and sweat‐management Janus textiles. Finally, critical considerations on the challenges and opportunities of PTM are presented and future directions are identified, including thermally conductive polymers and fibers, physiological/psychological statistical analysis, and smart PTM strategies.     

Outdoor thermal comfort study in a sub-tropical climate: a longitudinal study based in Hong Kong

This paper presents the findings of an outdoor thermal comfort study conducted in Hong Kong using longitudinal experiments—an alternative approach to conventional transverse surveys. In a longitudinal experiment, the thermal sensations of a relatively small number of subjects over different environmental conditions are followed and evaluated. This allows an exploration of the effects of changing climatic conditions on thermal sensation, and thus can provide information that is not possible to acquire through the conventional transverse survey. The paper addresses the effects of changing wind and solar radiation conditions on thermal sensation. It examines the use of predicted mean vote (PMV) in the outdoor context and illustrates the use of an alternative thermal index—physiological equivalent temperature (PET). The paper supports the conventional assumption that thermal neutrality corresponds to thermal comfort. Finally, predictive formulas for estimating outdoor thermal sensation are presented as functions of air temperature, wind speed, solar radiation intensity and absolute humidity. According to the formulas, for a person in light clothing sitting under shade on a typical summer day in Hong Kong where the air temperature is about 28°C and relative humidity about 80%, a wind speed of about 1.6 m/s is needed to achieve neutral thermal sensation.     

Effect of fiber type and fabric moisture content on the hydration state of human stratum corneum

1. 1. The purpose of this study was to determine the effect of fiber type and fabric moisture content on SC hydration.

2. 2. Using three similarly constructed fabrics, six fabric type/moisture content combinations were selected.

3. 3. Fabric swatches were placed on both “normal” and “hydrated” volar forearm skin of five subjects for a specified period, then removed.

4. 4. Two minutes after removal, evaporative water loss (EWL) and skin temperature were measured.

5. 5. Data were analyzed using analyses of variance and Bonferroni t-tests.

6. 6. For normal skin, SC hydration generally increased as fabric moisture content increased. SC was significantly drier after being in contact with cotton swatches at regain than at the two moisture content levels above regain, and also under polyester swatches.

7. 7. For hydrated skin, hydration state was significantly lower under the cotton swatch at regain than at 38.6% moisture content or at saturation, but was not significantly different under the polyester swatch at regain or at saturation.

The influence of urban design on outdoor thermal comfort in the hot, humid city of Colombo, Sri Lanka

The outdoor environment is deteriorating in many tropical cities due to rapid urbanization. This leads to a number of problems related to health and well-being of humans and also negatively affects social and commercial outdoor activities. The creation of thermally comfortable microclimates in urban environments is therefore very important. This paper discusses the influence of street-canyon geometry on outdoor thermal comfort in Colombo, Sri Lanka. Five sites with different urban geometry, ground cover, and distance from the sea were studied during the warmest season. The environmental parameters affecting thermal comfort, viz. air temperature, humidity, wind speed, and solar radiation, were measured, and the thermal comfort was estimated by calculating the physiologically equivalent temperature (PET). The thermal comfort is far above the assumed comfort zone due to the combination of intense solar radiation, high temperatures, and low wind speeds, especially on clear days. The worst conditions were found in wide streets with low-rise buildings and no shade trees. The most comfortable conditions were found in narrow streets with tall buildings, especially if shade trees were present, as well as in areas near the coast where the sea breeze had a positive effect. In order to improve the outdoor comfort in Colombo, it is suggested to allow a more compact urban form with deeper street canyons and to provide additional shade through the use of trees, covered walkways, pedestrian arcades, etc. The opening up of the city's coastal strip would allow the sea breeze to penetrate further into the city.