Showing papers on "Clothing insulation published in 2021"

The use of Monte Carlo method to assess the uncertainty of thermal comfort indices PMV and PPD: Benefits of using a measuring set with an operative temperature probe

Abstract: The Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) are the most used indices for the assessment of thermal conditions in indoor environments. However, many times, the uncertainties associated with the calculation of both indices are not reported, may be because direct methods are not easily applicable to calculate it. The present study applies Monte Carlo method to assess the uncertainties on the calculation of PMV and PPD, as a function of values and the uncertainties of four environmental (air temperature, mean radiant temperature, air velocity, and partial vapour pressure) and two individual related input parameters (metabolic rate and clothing insulation), used in Fanger's model, to calculate it. The metrological quality of the measuring probes was assumed through the scenarios established by ISO 7726 (1998) (required and desirable conditions). The use of uncertainties values for metabolic rate, clothing insulation and operative temperature were also considered. The main findings of this research are: (i) condition defined as required is not suitable for implementation of the classification scheme of thermal environments proposed by ISO 7730 (2005); (ii) in desirable condition, it is unrealistic obtaining an uncertainty of 0.2 °C for mean radiant temperature, if a 0.2 °C uncertainty temperature probe is used; (iii) the use of an operative temperature probe is a good strategy to decrease the overall level of uncertainty in the indices.

A digital tool for prevention and management of cold weather injuries—Cold Weather Ensemble Decision Aid (CoWEDA)

Abstract: This paper describes a Cold Weather Ensemble Decision Aid (CoWEDA) that provides guidance for cold weather injury prevention, mission planning, and clothing selection. CoWEDA incorporates current science from the disciplines of physiology, meteorology, clothing, and computer modeling. The thermal performance of a cold weather ensemble is defined by endurance times, which are the time intervals from initial exposure until the safety limits are reached. These safety limits correspond to conservative temperature thresholds that provide a warning of the approaching onset of frostbite and/or hypothermia. A validated six-cylinder thermoregulatory model is used to predict human thermal responses to cold while wearing different ensembles. The performance metrics, model, and a database of clothing properties were integrated into a user-friendly software application. CoWEDA is the first tool that allows users to build their own ensembles from the clothing menu (i.e., jackets, footwear, and accessories) for each body region (i.e., head, torso, lower body, hands, feet) and view their selections in the context of physiological strain and the operational consequences. Comparison of predicted values to skin and core temperatures, measured during 17 cold exposures ranging from 0 to -40°C, indicated that the accuracy of CoWEDA prediction is acceptable, and most predictions are within measured mean ± SD. CoWEDA predicts the risk of frostbite and hypothermia and ensures that a selected clothing ensemble is appropriate for expected weather conditions and activities. CoWEDA represents a significant enhancement of required clothing insulation (IREQ, ISO 11079) and wind chill index-based guidance for cold weather safety and survival.

Study of thermal comfort in the residents of different climatic regions of India-Effect of the COVID-19 lockdown.

Abstract: Thermal comfort standards are essential to ensure comfortable and enjoyable indoor conditions, and they also help in optimizing energy use. Thermal comfort studies, either climate chamber-based or field investigation, are conducted across the globe in order to ascertain the comfort limits as per the climatic and other adaptive features. However, very few studies are conducted when the occupants are subjected to a stressed condition, like the COVID-19 lockdown, which may not only have the health impacts but also have psychological impacts on the adaptation. In this paper, we present the results of the online study conducted regarding the status of thermal comfort during the COVID-19 lockdown in India. A total of 406 complete responses were collected from subjects located across 3 different climatic regions of India, that is, cold climate, composite climate, and hot and humid climate. Variations in clothing insulation, thermal sensation, and preference were noted across the different climatic regions. We also present the variation in opening of windows and running of fans with the variation in outdoor mean air temperature. The self-judged productivity, comfort, desire to go outdoors, and effectiveness of working from home were seen to vary with the increase in the days of lockdown.

Field study of pedestrians’ comfort temperatures under outdoor and semi-outdoor conditions in Malaysian university campuses

Abstract: Difficulties in controlling the effects of outdoor thermal environment on the human body are attracting considerable research attention. This study investigated the outdoor thermal comfort of urban pedestrians by assessing their perceptions of the tropical, micrometeorological, and physical conditions via a questionnaire survey. Evaluation of the outdoor thermal comfort involved pedestrians performing various physical activities (sitting, walking, and standing) in outdoor and semi-outdoor spaces where the data collection of air temperature, globe temperature, relative humidity, wind speed, solar radiation, metabolic activity, and clothing insulation data was done simultaneously. A total of 1011 participants were interviewed, and the micrometeorological data were recorded under outdoor and semi-outdoor conditions at two Malaysian university campuses. The neutral temperatures obtained which were 28.1 °C and 30.8 °C were within the biothermal acceptable ranges of 24–34 °C and 26–33 °C of the PET thermal sensation ranges for the outdoor and semi-outdoor conditions, respectively. Additionally, the participants’ thermal sensation and preference votes were highly correlated with the PET and strongly related to air and mean radiant temperatures. The findings demonstrated the influence of individuals’ thermal adaptation on the outdoor thermal comfort levels. This knowledge could be useful in the planning and designing of outdoor environments in hot and humid regions to create better thermal environments.

A Field Investigation on Adaptive Thermal Comfort in an Urban Environment Considering Individuals’ Psychological and Physiological Behaviors in a Cold-Winter of Wuhan

Abstract: To date, studies of outdoor thermal comfort (OTC) have focused primarily on physical factors, tending to overlook the relevance of individual adaptation to microclimate parameters through psychological and physiological behaviors. These adaptations can significantly affect the use of urban and outdoor spaces. The study presented here investigated these issues, with a view to aiding sustainable urban development. Measurements of OTC were taken at a university campus and in urban spaces. Simultaneously, a large-scale survey of thermal adaptability was conducted. Two groups were selected for investigation in a cold-winter-and-hot-summer (CWHS) region; respondents came from humid subtropical (Cfa) and hot desert (BWh) climates, according to the Koppen Climate Classification (KCC). Results showed that: (1) neutral physiological equivalent temperature (NPET) and preferred PET for people from the Cfa (PCfa) and BWh (PBWh) groups could be obtained with KCC; (2) PCfa adaptability behaviors were, subjectively, more adjustable than PBWh; (3) Clothing affected neutral temperature (NT), where NT reduced by approximately 0.5 °C when clothing insulation rose 0.1 Clo; and (4) Gender barely affected thermal acceptance vote (TAV) or thermal comfort vote (TCV) and there was a substantial relationship between thermal sensation, NT, and PET. These findings suggest ‘feels like’ temperature and comfort may be adjusted via relationships between microclimate parameters.

Seasonal comfort temperature and occupant's adaptive behaviour in a naturally ventilated university workshop building under the composite climate of India

Abstract: In the present research work, the authors investigated the seasonal thermal environment and thermal perception of university subjects in a naturally ventilated workshop building under the composite climate of India. Total 1460 subjective responses were collected during the field study in the year, 2019. Standard Effective Temperature (SET*) has been used as a rationally derived thermal comfort index to study the combined effects of air temperature, relative humidity and airspeed on perceived thermal sensation and occupant's preference under high metabolic rates. Probit analysis showed more than 80% of subjects were voting comfortable (±1 Thermal sensation votes) when SET* ranged between 25°C-33 °C. Seasonal mean comfort temperature varied more than 4.8 °C, while, preferred temperature was noted about 3 °C lower than their mean Griffiths comfort temperature. The adaptive relation developed from the collected database under high metabolic activities was compared with existing national and international comfort standards. The slope coefficient for adaptive relation was observed close to the adaptive model of ASHRAE Standard 55–2017 but lower than the National Building Code of India, 2016. Further, adaptive use of fans and windows were analyzed using logistic regression models and predicted about 80% of fans and windows were in operation at 30 °C. To confirm the adaptive mechanism, the interrelation of other contextual factors like gender, clothing insulation, airspeed, metabolic activities, etc. to thermal comfort expectations of subjects were also studied.

The Effects of a Passive Exoskeleton on Human Thermal Responses in Temperate and Cold Environments.

Abstract: The exoskeleton as functional wearable equipment has been increasingly used in working environments However, the effects of wearing an exoskeleton on human thermal responses are still unknown In this study, 10 male package handlers were exposed to 10 °C (COLD) and 25 °C (TEMP) ambient temperatures while performing a 10 kg lifting task (LIFTING) and sedentary (REST) both with (EXO) and without the exoskeleton (WEXO) Thermal responses, including the metabolic rate and mean skin temperature (MST), were continuously measured Thermal comfort, thermal sensation and sweat feeling were also recorded For LIFTING, metabolic heat production is significant decrease with the exoskeleton support The MST and thermal sensation significantly increase when wearing the exoskeleton, but thermal discomfort and sweating are only aggravated in TEMP For REST, MST and thermal sensation are also increased by the exoskeleton, and there is no significant difference in the metabolic rate between EXO and WEXO The thermal comfort is significantly improved by wearing the exoskeleton only in COLD The results suggest that the passive exoskeleton increases the local clothing insulation, and the way of wearing reduces the "pumping effect", which makes a difference in the thermal response between COLD and TEMP Designers need to develop appropriate usage strategies according to the operative temperature

Automatic estimation of clothing insulation rate and metabolic rate for dynamic thermal comfort assessment

Abstract: Existing heating, ventilation, and air-conditioning systems have difficulties in considering occupants’ dynamic thermal needs, thus resulting in overheating or overcooling with huge energy waste. This situation emphasizes the importance of occupant-oriented microclimate control where dynamic individual thermal comfort assessment is the key. Therefore, in this paper, a vision-based approach to estimate individual clothing insulation rate ( $$I_{\rm{cl}}$$ ) and metabolic rate (M), the two critical factors to assess personal thermal comfort level, is proposed. Specifically, with a thermal camera as the input source, a convolutional neural network (CNN) is implemented to recognize an occupant’s clothes type and activity type simultaneously. The clothes type then helps to differentiate the skin region from the clothing-covered region, allowing to calculate the skin temperature and the clothes temperature. With the two recognized types and the two computed temperatures, $$I_{\rm{cl}}$$ and M can be estimated effectively. In the experimental phase, a novel thermal dataset is introduced, which allows evaluations of the CNN-based recognizer module, the skin and clothes temperatures acquisition module, as well as the $$I_{\rm{cl}}$$ and M estimation module, proving the effectiveness and automation of the proposed approach.

Hourly occupant clothing decisions in residential HVAC energy management

Abstract: The state-of-the-art energy management for the heating, ventilation and air conditioning (HVAC) system uses a static clothing model that calculates the occupant's clothing insulation as a fixed value based on outdoor air temperature measured at a particular time of the day. However, the static clothing model can hardly capture the occupant's intra-day clothing behaviors, leading to inaccurate thermal comfort assessment and unrealistic HVAC energy management. This paper proposes a novel HVAC energy management scheme to optimally schedule the thermostat setpoints of HVAC and to provide recommendations on occupants' optimal hourly clothing decisions through a predicted mean vote model, while considering uncertainties in the outside temperature. The proposed HVAC energy management scheme is solved by applying an approximate dynamic programming approach. Further, a model predictive control framework with a long short-term memory based forecaster is developed for more realistic simulations. We study the HVAC schedules in a residential home with summer and winter time of use electricity tariffs for both male and female occupants. Compared with non-optimized cases, proof-of-concept simulation results demonstrate that the proposed scheme can achieve a 53.8% and a 29.8% cost saving in a summer-male scenario and a winter-female scenario, respectively.

Validation of iso 9920 clothing item insulation summation method based on an ambulance personnel clothing system

Abstract: This study aimed to validate the summation methods suggested by ISO 9920. Twenty seven items from an ambulance personnel clothing system were selected for testing. The basic insulation of each garment item (Iclu) was calculated based on the thermal manikin tests. More than 100 realistic clothing combinations were compiled and basic insulation (Icl) of these ensembles was calculated according to ISO 9920. These were ranked after the calculated insulation, and 14 sets covering insulation from 0.63 to 3.33 clo were measured on the thermal manikin for acquiring the basic clothing insulation (Icl). Regression analysis was used to compare the summed and measured Icl values. The difference between values varied from -18 to 12%. The highest percentual difference was for the lightest clothing sets, while the absolute differences were similar over the whole insulation range ranging between -0.17 to 0.18 clo with an average difference of 0.02 clo (-0.16%). All basic insulation values stayed very close to the line of identity (R2=0.98). The summation equation gave, in the case of this ambulance clothing system, very close results to the measured values. This encourages evaluating and selecting protective clothing combinations for thermal comfort based on individual item measurements.

Bioheat Transfer Equation with Protective Layer

Abstract: The human thermal comfort is the state of mind, which is affected not only by the physical and body’s internal physiological phenomena but also by the clothing properties such as thermal resistance of clothing, clothing insulation, clothing area factor, air insulation, and relative humidity. In this work, we extend the one-dimensional Pennes’ bioheat transfer equation by adding the protective clothing layer. The transient temperature profile with the clothing layer at the different time steps has been carried out using a fully implicit Finite Difference (FD) Scheme with interface condition between body and clothes. Numerically computed results are bound to agree that the clothing insulation and air insulation provide better comfort and keep the body at the thermal equilibrium position. The graphical representation of the results also verifies the effectiveness and utility of the proposed model.

A survey of clothing insulation for university students in Japan: Effect of clothing insulation distribution between the upper and lower body in the winter

Abstract: The clothing insulation is an important factor in the adaptation to thermal environment for occupants. With the exception of certain types of clothing, occupants' clothing is divided into upper and lower body, and it is important to focus the analysis on clothing of upper and lower body. The objective of this study was to determine the effect of the clothing insulation distribution between the upper and lower body in a cold environment. In this study, the analysis was carried out using field surveys and simulations. In the simulation, the sensible heat loss from the human body was analyzed using the JOS-2 model. A thermal environment survey and a subjective vote survey were conducted from October 2019 to January 2020 at a university in Nagano City, Nagano Prefecture, Japan. Nagano City is characterized by a humid subtropical climate (Cfa) according to the Koppen climate classification. During the survey period, the mean outdoor air temperature was 9.6 °C and the mean indoor operative temperature was 20.8 °C. The survey revealed that the occupants adjusted the clothing insulation for the total body by adjusting the clothing insulation for the upper body to the thermal environment. The simulation demonstrated that the sensible heat loss and mean skin temperature of the upper and lower body differed between the conditions in which the total body clothing insulation was uniformly distributed and those in which it was not.

Updated Database of Clothing Thermal Insulation and Vapor Permeability Values of Western Ensembles for Use in ASHRAE Standard 55, ISO 7730 and ISO 9920; Results of ASHRAE RP-1760

Abstract: ASHRAE RP-1760 aimed to update the database of western clothing as used in ANSI/ASHRAE Standard 55-2013, Thermal Environmental Conditions for Human Occupancy (ASHRAE 2013a), ISO Standard 7730-2005, Ergonomics of the Thermal Environment—Analytical Determination and Interpretation of Thermal Comfort Using Calculation of the PMV and PPD Indices and Local Thermal Comfort Criteria (ISO 2005), and ISO Standard 9920-2009, Ergonomics of the Thermal Environment— Estimation of Thermal Insulation and Water Vapor Resistance of a Clothing Ensemble (ISO 2009). The previous database, established in the 1970’s and 1980’s, relied mostly on single zone manikins and did not provide detail on air and body movement effects on insulation. Insulation values of up to 70 clothing ensembles (31 male, 39 female) were measured in a static standing posture at 0.2, 0.4 and 1 m.s-1 (0.66, 1.31, 3.28 ft.s-1) air speed, walking in 0.2 and 1.0 m.s-1 air speed , and in a sitting posture in 0.2 m.s-1 air speed. Measurements were conducted in three laboratories on three manikins with up to 34 individually controlled zones. In addition, vapor resistance was determined in 31 ensembles. This new database provides total, intrinsic and air insulation values, vapor resistance and clothing area factors as well as correction factors to estimate the wind and movement effect on clothing insulation. Furthermore, the model to estimate the clothing area factor from insulation values of the ensembles was updated reflecting changes in commonly worn clothing styles.

Thermal discomfort in healthcare workers during the COVID-19 pandemic.

Abstract: INTRODUCTION: Due to the COVID-19 pandemic, healthcare workers are now required to use additional personal protective equipment (PPEs) to protect themselves against the virus. That led to an increased clothing insulation which is negatively affecting the perceived healthcare workers' thermal sensation. OBJECTIVES: While demonstrating through software simulations the potential level of thermal discomfort healthcare workers involved in the COVID-19 emergency can be subjected to, this work aims at identifying measures to improve thermal sensation perception and acceptable thermal conditions for medical personnel. METHODS: After having obtained the insulation values of individual clothing used by staff during COVID-19 emergency through the use of a thermal well-being evaluation software, the Fanger indexes (PMV - Predicted Mean Vote and PPD - Predicted Percentage of Dissatisfied) were calculated in order to estimate staff satisfaction to microclimatic conditions. RESULTS: The use of COVID-19 additional PPEs with an air temperature equal to 22 °C (normally considered optimal) brings the PMV index equal to 0.6, which corresponds to 11.8 % being unsatisfied (PPD) due to perceived heat. DISCUSSION: The use of additional protective devices significantly increases the clothing insulation level, facilitating the onset of conditions of thermal discomfort in the health workers. Workers engaged in the execution of nasopharyngeal swabs were most affected by the summer weather conditions and certainly represent the most critical category, for which it would be recommended to implement a higher turnover of service to reduce individual exposure time and consequent discomfort.

The correction of clothing insulation and ergonomic design through 3D CAD reverse engineering.

Abstract: Three-dimensional (3D) scanning and computer-aided design (CAD) technology has been used in engineering and ergonomics practice for several years, due to their admissibility in producing accurate 3...