Clothing Thermal Insulation Research Articles

Research on The local clothing thermal insulation prediction model with different dress state of indoor occupants

In a dynamic and non-uniform thermal environment, adjusting personal dress states is an effective method for achieving thermal comfort. During this process, clothing thermal insulation, as a key parameter in human thermoregulation models, is not uniformly distributed across the body. However, current thermal comfort standards do not provide a direct method for obtaining local clothing thermal insulation. Based on field surveys, this study summarized typical year-round clothing ensembles and common dress states, and tested the local thermal insulation of 40 clothing ensembles and 60 individual garments using a thermal manikin. Subsequently, a prediction model for the local thermal insulation of clothing ensembles was developed based on the overall thermal insulation of individual garments. Meanwhile, it was found that changes in dress state significantly alter the thermal insulation of body parts such as the arms and chest. Simulations conducted using the JOS-3 and UCB models revealed that the lower the ambient temperature, the greater the impact of changes in local clothing thermal insulation on human skin temperature and thermal sensation. Finally, a correction model for different dress states was developed, and comparison with existing models showed the lower root mean square error (RMSE) between the predicted and measured values. This study provides a more accurate and convenient method for determining local thermal insulation, offering a data foundation for improving indoor environmental control and enhancing energy efficiency.

Self-assessed threshold for cold temperatures and thermal insulation of clothing among poultry workers

The association between self-assessed cold threshold (CT) and thermal insulation of clothing (Icl) was analysed in 283 poultry workers in Thailand. The mean CT was 13.5 °C (range − 28–29) and the mean Icl was 1.23 clo (range 0.35–2.21). The adjusted CT remained unchanged at low Icls (0.35 through 1.25 clo) but was estimated to increase by 14.8 °C at high Icls (1.25 through 2.21 clo). Overall, CT was higher by 2.4 °C (95% confidence interval [CI] 0.3–3.8) at high (≥ 1.25 clo) than that at low (< 1.25 clo) Icl, but this difference was modified by personal and work-related factors. The difference was 2.6 °C (CI 0.5–4.6) for older (30–57 y) compared to younger (18–29 y) participants, with an excess of 7.3 °C (CI 5.6–9.0) for low vs high educated participants, 2.6 °C (CI 0.5–4.8) for those doing heavy vs light work, 7.4 °C (CI 3.7–11.0) for alcohol consumers vs others, and 3.4 °C (CI 0.6–6.3) for smokers vs non-smokers. The differences were independent of personal characteristics and worksite physical conditions and were interpreted as increased cold sensitivity among subgroups with lesser stamina and poorer health. Sensitive worker subgroups should be identified, and their need for cold protection should be reviewed.

Validity of ten analytical heat stress indices in predicting the physiological parameters of people under various occupational and meteorological conditions.

Until now, only a few comprehensive studies have validated analytical heat stress indices in different conditions. The present study aims to investigate the validity of these indicators in predicting the physiological parameters of workers. This cross-sectional study was conducted with 194 male employees working in warm environments. First, demographic information was collected. After participants rested for 30 min, their heart rate and tympanic temperature were measured. The subjects then performed their routine tasks. At the end of 90 min, their heart rate and tympanic temperature were again measured. Additionally, their metabolism rate and clothing thermal insulation were estimated. Environmental parameters were also measured at 30-, 60-, and 90-min time points. Additional information required to compute the indices was recorded. Then, the values of each of the indices were computed. Finally, the validity of the indices was assessed under different conditions. The results indicated that the highest regression coefficients with tympanic temperature were assigned to modified physiologically equivalent temperature (mPET) (0.7515), predicted heat strain (PHS) (0.7201), and predicted mean vote (PMV) (0.7082), index, respectively. Also, the greatest regression coefficients with heart rate belonged to mPET (0.7773), PMV (0.7624), and PHS (0.6479) index, respectively. Based on the results, the highest diagnostic accuracies of receiver operating characteristic (ROC) curves for tympanic temperature were related to indices of mPET, PHS, and PMV with the area under the ROC curve (AUC) of 0.945, 0.931, and 0.930, respectively. Of the studied indices, it was observed that mPET, PHS, PMV, and PPD showed more validity compared to others.

Effects of clothing's thermal insulation on outdoor thermal comfort and thermal sensation: A case study in Tehran, Iran

The objective of this research is to examine how clothing insulation value (Icl) impacts outdoor thermal comfort and sensation (TSV), suggest changes to the physiologically equivalent temperature (PET) and universal thermal climate index (UTCI) measures to account for these effects, and reconsider Icl benchmarks. Research included on-site measurements in Tehran, Iran, and 838 interviews. The analysis found a significant difference in thermal comfort levels between TSV and PET, with 77.3 % of cases indicating comfort temperature. However, when comparing TSV with UTCI, this percentage slightly decreased to 75.5 %. In equations involving PET and Icl, the coefficient for males was 0.74 for Icl and 0.12 for PET, while for females, it was -0.32 for Icl and 0.1 for PET. Similarly, in equations involving UTCI and Icl, the coefficient for males was 0.92 for Icl and 0.13 for UTCI, while for females, it was -0.06 for Icl and 0.1 for UTCI. These results highlight the effects of Icl and thermal conditions on thermal sensation for genders, with females experiencing lower PET and UTCI values than males. Additionally, the outcomes of the study, which involved adjusting the indices (PETIcl / UTCI Icl) to consider Icl, will aid in creating outdoor spaces that are more pleasant and comfortable.

Validity of eighteen empirical heat stress indices in predicting the physiological parameters of workers under various occupational and climatic conditions

IntroductionThermal strain indices have been developed to assess the risk level of heat strain on workers in occupational settings. To date, no comprehensive study has validated these indicators. The present study aims to investigate the validity of eighteen empirical heat stress indices in predicting the physiological parameters of workers under various occupational and environmental conditions. MethodsThis cross-sectional study was conducted with 201 male employees working in warm environments. First, Individual and background information was collected. After participants had rested for 30 min, their heart rate and tympanic temperature were measured. People then returned to their workplace and started their routine work. At the end of 90 min, workers' heart rate and tympanic temperature were measured again. Additionally, researchers estimated their metabolic rate and clothing thermal insulation. Environmental parameters were also collected including dry temperature, wet temperature, globe temperature, relative humidity and air flow speed at 30, 60 and 90 min time points. Additional information was recorded to calculate environmental indicators. Then, the values of each of the environmental indicators were calculated. Finally, the validity of each index was evaluated under these different conditions. ResultsResults showed that highest regression coefficients with tympanic temperature were CET (0.6822), TSI (0.6697), WBGT (0.6692), and ESI (0.6415) indices, respectively. The greatest regression coefficients with heart rate belonged to TSI (0.4687), OT (0.4545), CET (0.4449), and Teq (0.4449) indices, respectively. Based on these results, the highest diagnostic accuracies of ROC curves for tympanic temperature were related to indices of WBGT, CET, and HI with AUC of 0.913, 0.912, and 0.910, respectively. ConclusionIn total, the results showed that the two indices of WBGT and CET have the strongest validity among the empirical indices. However, each of these empirical indices has the best accuracy under specific conditions. Therefore, the development of new indices is required for the precise assessment of heat strain under various conditions.

Modification and verification of the PMV model to improve thermal comfort prediction at low pressure

The human body's thermal physiology changes due to atmospheric pressure, which significantly impacts the perception of thermal comfort. To quantify this effect, an improved version of the Predicted Mean Vote model (PMVp), was developed in this study to predict human thermal sensation under low atmospheric pressure conditions. The study employed environmental conditions of 0km/26°C, 3km/26°C, 4km/26°C, and 4km/21°C. Thirteen subjects were continuously monitored for exhaled CO2, inhaled O2, ambient temperature (ta), relative humidity (RH), air velocity (V), black globe temperature (tg), and altitude (H). The predictive performance of PMVp was evaluated by comparing the experimental results from this study with previous experiments. The findings demonstrate that PMVp exhibits lower root-mean-square errors (RMSE) than the original PMV model. Under the four experimental conditions, the RMSE values for PMVp were 0.311, 0.408, 0.123, and 0.375, while those for PMV were 1.251, 1.367, 1.106, and 1.716, respectively. Specifically, at a temperature range of 21∼27°C (altitude: 941m), the RMSE of PMVp (0.354) was smaller than PMV's. Furthermore, the study analyzed the sensitivity of PMVp to input parameters at an altitude of 4 km. PMVp exhibited considerable sensitivity to the metabolic rate (M) and thermal insulation of clothing (ICL). Consequently, a simple sensitivity scale was established: M>ICL>Ta≈V>Tr>H≈RH, indicating the relative importance of these parameters in influencing PMVp's response. The research findings provide comprehensive knowledge and a useful reference for developing a standard to design and evaluate indoor thermal environments in the plateau region.

Development of Infrared Reflective Textiles and Simulation of Their Effect in Cold-Protection Garments

Two ways of to enhance the heat insulation of cold-protecting garments are studied using the mathematical model, which describes the coupled transport of temperature, humidity, and bound and condensed water. The model is developed in a one-dimensional formulation. The thermal radiation transport is explicitly considered by the subdivision of the heat flux into radiative and conduction parts. The model is utilized to study the improvement of heat-insulating properties of cold protective garments using aerogel materials and thin infrared reflective textile layers. Special attention is paid to the technological aspects of manufacturing such reflective textiles. The numerical investigations show that the use of infrared reflective textiles is the most effective of the two studied methods. Due to the reflection of the radiant heat flow coming from the human body, the skin temperature rises and the thermal insulation of clothing is significantly improved.

Self-Assessed Threshold Temperature for Cold among Poultry Industry Workers in Thailand.

The self-assessed threshold temperature for cold in the workplace is not well known. We asked 392 chicken industry workers in Thailand what they regard as the cold threshold (CT) and compared subgroups of workers using linear and quantile regressions by CT sextiles (percentiles P17, P33, P50, P67, and P83, from warmest to coldest). The variables of interest were sex, office work, and sedentary work, with age, clothing thermal insulation, and alcohol consumption as adjustment factors. The mean CT was 14.6 °C. Office workers had a 6.8 °C higher mean CT than other workers, but the difference ranged from 3.8 °C to 10.0 °C from P17 to P83. Sedentary workers had a 2.0 °C higher mean CT than others, but the difference increased from 0.5 °C to 3.0 °C through P17-P83. The mean CT did not differ between sexes, but men had a 1.6-5.0 °C higher CT at P17-P50 (>20 °C) and a 5.0 °C lower CT at P83 (<10 °C). The CT was relatively high at warm (≥10 °C), dry (relative humidity <41%), and drafty (air velocity > 0.35 m/s) worksites. We conclude that office, sedentary, and female workers and those working at warm, dry, and draughty sites are sensitive to the coldest temperatures, whereas male workers are sensitive even to moderate temperatures.

Clothing thermal insulation of infant in stroller relating to evaluation of thermal environment of infant

The clothing thermal insulation for individual clothing ensembles of infant and strollers has been clarified. However, the clothing thermal insulation for the combination of them has not been measured at all. The purpose of this study is to examine the typical values of human factors such as the clothing area factor and clothing thermal insulation of an infant in a stroller. As typical clothing ensembles, seasonal combinations of infant clothing with a stroller were selected. The stroller was treated as part of the infant’s clothing. The clothing area factors were measured by using the photographic method. The clothing thermal insulations were measured by using an infant’s thermal manikin. The typical clothing area factor of an infant in a stroller is 3.67 for summer clothing, 3.75 for mid-season clothing, and 4.19 for winter clothing. The typical clothing thermal insulation of an infant in a stroller is 1.23 clo for summer, 1.39 clo for mid-season, and 1.97 clo for winter. The stroller was shown to significantly affect the body heat balance between the infant and the thermal environment.

Heat Strain Evaluation of Power Grid Outdoor Workers Based on a Human Bioheat Model

Power grid outdoor workers are usually exposed to hot environments and could suffer the threats to occupational health and safety like heat strain and injury. In order to predict and assess the thermophysiological responses of grid workers in the heat, the clothing thermal insulation of grid worker ensembles was measured by a thermal manikin and a multi-segment human bioheat model was employed to evaluate the thermophysiological response parameters of grid workers such as core temperature, skin temperature and sweat loss. The results show that working in a hot environment can cause a obvious increase in core temperature and skin temperature of grid workers, and the acceptable maximum working time of grid workers varies greatly in different hot environments. A reasonable work organization strategy can effectively decrease the core temperature and sweat loss, increasing the duration of acceptable maximum working time for grid workers. This study is helpful to assess heat-related risks of grid workers and support power grid companies to rationalize work organization strategies and personal protection guidelines.

Workplace Cold and Perceived Work Ability: Paradoxically Greater Disadvantage for More vs. Less-Educated Poultry Industry Workers in Thailand.

The association between worksite temperature and perceived work ability (WA) in various educational classes remains unknown. Therefore, we interviewed 286 poultry industry workers in Thailand about their WA and linked their responses to worksite temperature. WA was based on the self-assessment of current work ability compared with their lifetime best ability (scores 0–10). Education was classified as high (university or vocational school) or low (less education). Temperature was classified as cold (−22–10°C) or warm (10–23°C). WA and the occurrence of a low WA were regressed on worksite temperature, education, and their interaction with the adjustment for sex, age, job category, physical work strain, moving between cold and warm sites, thermal insulation of clothing, relative humidity, and air velocity. The average worksite temperature was 10°C for high- and 1°C for low-educated workers. The average WA score was 8.32 (SD, 1.33; range, 4–10) and classified as low (<8) in 23% of the workers. In highly-educated workers, the adjusted mean WA decreased from 9.11 in the warm areas to 8.02 in the cold areas and the prevalence of a low WA increased from 11 to 30%, while no significant change was observed in less-educated workers. The WA score was estimated to decline by 10% more (95% CI, 4–16%) in the cold areas for the more vs. less-educated workers and the prevalence of a poor WA was estimated to increase 3.09 times (95% CI, 1.43–5.45) more. Highly-educated workers in this industry are a risk group that should be given customized advice.

3D numerical investigation of the heat and flow transfer through cold protective clothing based on CFD

A three-dimensional (3D) model solving the heat and flow transfer through cold protective clothing under various ambient conditions was developed based on the torso thermal manikin in the present work. The conjugate problem of conduction, convection and radiation was simultaneously solved by the proposed model. The air in the computation domain was treated as a uniform turbulent flow, but it was considered as a slow air movement when the air was in the clothing modeled as a homogenous porous structure. Ideal contact between skin and clothing ensemble was assumed to eliminate the effect caused by the air layer enclosed at the gap. Validation study was performed by comparing the numerical results with experimental results obtained from the torso thermal manikin in a climate chamber. A good agreement was found with the maximum difference in heat flux and thermal resistance below 7.4% and 7.8%, respectively. The dependence of various parameters such as ambient temperature, air velocity and clothing thickness on clothing thermal insulation was further clarified by extensive parametric study. The local variations in temperature distribution, radiative and convective heat flux along the clothing outer surface were found to be significant, indicating that a space-average method would withhold the variation between different local positions. The global relative contribution of conduction, convection and radiation under different temperature and windy conditions were also evaluated. Besides, the lowest comfort temperature at activity level 2 met and 4 met was investigated for clothing with different thickness, and the effect exerted from wind was pronounced.

Investigation on the thermal insulation regulating performance of a newly developed air inflatable garment

It is important to keep body thermal comfort experiencing transient thermal environments, and adjusting clothing thermal insulation is expected to be a feasible strategy. In this study, to realize the thermal insulation regulating performance, a novel air inflatable garment (AirIG) using natural air as the thermal insulator was developed, and the thickness of the air layer entrapped in AirIG was determined through computer simulation. The thermal insulation regulating performance of AirIG was investigated using ‘Newton’ thermal manikin. Thermal insulation values of the AirIG were measured under four air inflation volumes [i.e., CON (no air inflation), 1/3FULL, 2/3FULL and FULL (the maximum air inflation)]. Besides, the effects of garment pattern and air velocity (i.e., 0.15 m/s, 1.55 m/s and 3.04 m/s) on the thermal insulation regulating performance of the AirIG were also studied. Results showed that with the increasing air inflation volumes, thermal insulation in the upper of the AirIG firstly significantly increased and then remained stable (i.e., CON<1/3FULL<2/3FULL, FULL, p < 0.01). Adding sleeves remarkably increased the thermal insulation when the air inflation volume increased from CON to FULL (p = 0.056). Increasing air velocity significantly decreased the thermal insulation in the upper and local body regions of the AirIG. The thermal insulation regulating performance of the AirIG disappeared when the air velocity increased to 1.55 m/s, evidenced by the insignificant thermal insulation difference among the four air inflation volumes (p > 0.1). Therefore, the AirIG can be recommended as an effective thermal insulation regulating strategy for human body in low air velocities.

Clothing Thermal Insulation for Typical Seasonal Clothing of Infant with Infant Thermal Manikin

Infants are less thermally adapted to their environment and can be considered as needing protective measures against thermal environments. It is not ethical to conduct subject experiments on infants. Thermal insulation in clothing is an essential control coefficient for the evaluation of the thermal environment of an infant. A thermal manikin can be used as an alternative method for carrying out experiments and to control the thermal manikin based on heat balance. The purpose of this study was to clarify the thermal insulation of infants’ clothing. An infant thermal manikin was used to clarify the thermal insulation (Icl) of typical summer, mid-season, and winter clothing combinations for infants. The thermal insulation of typical seasonal clothing combinations was 0.30 clo for summer clothing, 0.57 clo for mid-season clothing and 1.02 clo for winter clothing. It was clarified that it is essential to consider clothing conditions by taking into account differences in posture and to define the clothing thermal insulation (Icl) when designing and evaluating thermal environments. When designing and evaluating an infant’s thermal environment, it is essential to investigate using data from infants.

Influence of Stroller upon Thermal Insulation of Infant

In outdoor spaces, infants in strollers are significantly affected by thermal radiation from the ground surface due to their proximity to it. Infants are at increased risk of heat stroke while riding in a stroller. Infants are less thermally adapted to their environment and can consequently be considered to need protective measures against thermal environments. In order to treat strollers as clothing, in the present study, experiments were conducted to clarify the thermal environment of an infant riding in a stroller. Using an infant thermal manikin, the clothing area factor fcl and the clothing thermal insulation Icl of the stroller were determined. The stroller clothing area factor fcl was 3.21 and the stroller clothing thermal insulation Icl was 0.47 clo. Therefore, it can be inferred that strollers have a pronounced effect on the body heat balance between an infant and their environment.

Development and validation of an environmental heat strain risk assessment (EHSRA) index using structural equation modeling based on empirical relations

BackgroundNeed to a simple, available, accurate, comprehensive, and valid indicator is felt to assess thermal effects. Therefore, the present study was aimed to develop and validate the environmental heat strain risk assessment (EHSRA) index using structural equation modeling (SEM) based on empirical relations.MethodsThis cross-sectional study was performed on 201 male workers in environments with various climatic conditions. The heart rate and tympanic temperature of the individuals were monitored at times of 30, 60, and 90 min after beginning the work. At these times, values of dry temperature, wet temperature, globe temperature, and air velocity were also measured and metabolism rate and clothing thermal insulation value were estimated. At the end, a theoretical model was depicted in AMOS software and obtained coefficients were applied to develop a novel index. The scores of this indicator were categorized into four risk levels via ROC curves and validate using linear regression analysis.ResultsIndirect effect coefficients of the globe temperature, dry temperature, wet temperature, air velocity, metabolism, and clothing thermal insulation variables on the tympanic temperature were computed by 0.77, 0.75, 0.69, 0.24, 0.49, and 0.39, respectively. These coefficients were applied to develop the index. Optimal cut-off points of boundaries between risk levels included 12.02, 15.88, and 17.56. The results showed that the EHSRA index justified 75% of the variations of the tympanic temperature (R2 = 0.75).ConclusionsThe novel index possesses appropriate validity. It was suggested that this indicator is applied and validated in various environments in the next studies.

Development of a personal heat strain risk assessment (PHSRA) index in workplaces and its validation

BackgroundThere is not a comprehensive heat stress index to screen the people susceptible to heat disorders and illnesses in hot workplaces. The present study was aimed to develop a personal heat strain risk assessment (PHSRA) index in workplaces and validate it.MethodsThis cross-sectional study was carried out on 201 Iranian male employees under various thermal conditions. At first, the demographical data of participants were gathered. After that, the heart rate and tympanic temperature of the subjects were carefully measured at times of 30, 60, and 90 min of starting the work. Environmental factors were measured simultaneously. The metabolism rate and insulation value of clothes were also estimated. At the end, a novel index of the heat strain was developed using structural equation modeling in AMOS and validated using linear regression analysis in SPSS.ResultsIndirect effect coefficients of personal factors including age, body mass index, maximum aerobic capacity, and body surface area were equal to 0.031, 0.145, − 0.064, and 0.106, respectively. The coefficients of main factors including dry temperature, wet temperature, globe temperature, wind speed, metabolism, and clothing thermal insulation were obtained as 0.739, 0.688, 0.765, 0.245, 0.482, and 0.383, respectively. These coefficients and normalized values of the factors were used to develop a novel index. The total score of the index was categorized into four levels by optimal cut-off points of 12.93, 16.48, and 18.87. Based on the results of regression analysis, this index justifies 77% of the tympanic temperature as a dependent variable (R2 = 0.77).ConclusionsIn general, the results indicated that the novel index developed by the personal and main factors had proper validity in the prediction of thermal strain.

고령 남녀의 겨울철 품목별 착의실태와 한 벌 의복의 보온력

This study was conducted to investigate the elderly’s actual wearing condition by clothing item and clothing thermal insulation in winter. Elderly males (N=111) and females (N=138) participated in this study. Based on actual wearing condition by clothing item, the representative winter ensembles of males and females outside and at home, respectively, were derived and then thermal insulation of those ensembles were measured by using a thermal manikin. Among the upper items outside, the wearing rates of the padded coats were the highest in both males and females. The wearing rates of singlet were higher in males compared to females both outside and at home, respectively (P<0.01). The wearing rates of long-sleeved T-shirts and a vest were higher in females than those in males (P<0.01). The 82.6% and 57.2% of females wore brassieres outside and at home, respectively. As for the lower items, males and females wore boxer shorts and panties, respectively. More than 65% and 46% of males and females wore long-length underpants outside and at home, respectively, and there were no significant differences between gender. The wearing rate of hat was higher in males than that in females, while the wearing rate of muffler and gloves were higher in females (all, P<0.01). Thermal insulation of clothing ensembles in winter were 1.84 clo for male and 1.50 clo for female outside and 0.56 clo and 0.59 clo at home, respectively. These results showed that elderly males and females have different wearing behavior in winter.

Insulation and Evaporative Resistance of Clothing for Sugarcane Harvesters and Chemical Sprayers, and Their Application in PHS Model-Based Exposure Predictions.

Many workers are exposed to heat stress that can be exacerbated by the type of clothing they wear. The resulted heat strain can lead to short or long-term heat-related disorders. This study aimed to measure clothing properties of sugarcane field workers and evaluate the heat strain by an international standard, predicted heat strain model (PHS). The clothing thermal insulation and evaporative resistance values of sugarcane cutter and chemical sprayer outfits were acquired for the whole body, body regions and specific body parts via thermal manikin measurements. The detailed clothing insulation values of body parts can be utilized in advanced thermo-physiological models, while in this study, the values for the whole body together with weather data were used in PHS. Estimated duration limited exposure times (DLE) for an hour-by-hour prediction over a workday and for a range of high humidity scenarios were calculated. Such evaluation tools can be used for risk assessment and management to support organizational measures and prepare equipment and materials in the case of hot weather events in order to avoid dehydration and other heat-related disorders.

Assessment of a Real-Time Prediction Method for High Clothing Thermal Insulation Using a Thermoregulation Model and an Infrared Camera

For evaluating the thermal comfort of occupants, human factors such as clothing thermal insulation (clo level) and metabolic rate (Met) are one of the important parameters as well as environmental factors such as air temperature (Ta) and humidity. In general, a fixed clo level is commonly used for controlling heating, ventilation, and air conditioning using the thermal comfort index. However, a fixed clo level can lead to errors for estimating the thermal comfort of occupants, because clo levels of occupants can vary with time and by season. The present study assesses a method for predicting the clo level of occupants using a thermoregulation model and an infrared (IR) camera. The Tanabe model and the Fanger model were used as the thermoregulation models, and the predicted performance for high clo level (winter clothing) was compared. The skin and clothing temperatures of eight subjects using a non-contact IR camera were measured in a climate chamber. In addition, the measured values were used for the thermoregulation models to predict the clo levels. As a result, the Tanabe model showed a better performance than the Fanger model for predicting clo levels. In addition, all models tended to predict a clo level higher than the traditional method.