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A 7-segment and 29-node numerical hand-glove/mitten model was developed to simulate human hand physiological responses in various cold environments. To validate the model, simulated skin temperatures were compared to data from published literature and human trials conducted at -20, -40, and -60 °C. Results demonstrated that the model could reasonably predict cold-induced vasodilation (CIVD) responses at 0 °C temperature. At -20 °C, the model predicted skin temperature with the root mean square deviation (RMSD) falling within the measurement standard deviation (SD) for both the entire and local hand except for the posterior hand. At -40 and -60 °C, the model could predict the trend of the skin temperatures of the whole/local hand, but the RMSD was larger than the SD for the majority of predictions. A parametric analysis revealed that the palm and posterior hand had higher skin temperatures than the fingers, while the thumb had the lowest skin temperature of the fingers in all simulated cases except the case with a 3.5 clo mitten at -60 °C. The proposed numerical hand-glove/mitten model could reasonably predict local hand physiological responses in three extremely cold environments and provides fundamental knowledge for cold stress prediction and protective glove development, thereby improving the safety and health of industrial workers, firefighters, first responders, and troops., Competing Interests: Declaration of competing interest The work described has not been submitted elsewhere for publication, in whole or in part, and all the authors listed have approved the manuscript that is enclosed., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

This paper aims to integrate a human thermoregulatory model with a clothing model to predict core and skin temperatures. The human thermoregulatory model, consisting of an active system and a passive system, was used to determine the thermoregulation and heat exchanges within the body. The clothing model simulated heat and moisture transfer from the human skin to the environment through the microenvironment and fabric. In this clothing model, the air gap between skin and clothing, as well as clothing properties such as thickness, thermal conductivity, density, porosity, and tortuosity were taken into consideration. The simulated core and mean skin temperatures were compared to the published experimental results of subject tests at three levels of ambient temperatures of 20 °C, 30 °C, and 40 °C. Although lower signal-to-noise-ratio was observed, the developed model demonstrated positive performance at predicting core temperatures with a maximum difference between the simulations and measurements of no more than 0.43 °C. Generally, the current model predicted the mean skin temperatures with reasonable accuracy. It could be applied to predict human physiological responses and assess thermal comfort and heat stress., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Five protective garments (light summer clothing L, high visibility clothing HV, military clothing MIL, climber coverall CLM and firefighting clothing FIRE) were assessed on eight unacclimated male subjects at two environments: moderate warm environment with high humidity (MWH, 20.0°C, 86% relative humidity) and warm environment with moderate humidity (WMH, 30.0°C, 47% relative humidity). The thermophysiological responses and subjective sensations were reported. The PHS model (ISO7933) was used for predicting thermophysiological responses for each testing scenario. It was found that there were significant differences between clothing FIRE and other clothing on thermal sensation (p<0.05). Significant differences were found on skin humidity sensation between FIRE and L, HV or MIL (p<0.001). The RPE value in FIRE is significantly different with L and HV (p<0.05). In MWH, the post-exercise mean skin temperatures increased by 0.59 and 1.29°C in MIL and CLM. In contrast, mean skin temperatures in L, HV, MIL, CLM and FIRE in WMH increased by 1.7, 2.1, 2.1, 2.8 and 3.3°C, respectively. The PHS model presented good performance on predicted mean skin temperatures in MIL and CLM at the two studied environments. However, the skin temperature prediction with light clothing in WMH was weak. For thick protective clothing, the prediction on rectal temperature was protective. It is thus concluded that the results generated by the PHS model for high insulating clothing and measurements performed in high humidity environments should be explained with caution.

Clothing evaporative resistance is one of the inherent factors that impede heat exchange by sweating evaporation. It is widely used as a basic input in physiological heat strain models. Previous studies showed a large variability in clothing evaporative resistance both at intra-laboratory and inter-laboratory testing. The errors in evaporative resistance may cause severe problems in the determination of heat stress level of the wearers. In this paper, the effect of temperature difference between the manikin nude surface and wet textile skin surface on clothing evaporative resistance was investigated by both theoretical analysis and thermal manikin measurements. It was found that the temperature difference between the skin surface and the manikin nude surface could lead to an error of up to 35.9% in evaporative resistance of the boundary air layer. Similarly, this temperature difference could also introduce an error of up to 23.7% in the real clothing total evaporative resistance (R ( et&#95;real ) < 0.1287 kPa m(2)/W). Finally, it is evident that one major error in the calculation of evaporative resistance comes from the use of the manikin surface temperature instead of the wet textile fabric skin temperature.

In this paper, the prediction accuracy of the PHS (predicted heat strain) model on human physiological responses while wearing protective clothing ensembles was examined. Six human subjects (aged 29 ± 3 years) underwent three experimental trials in three different protective garments (clothing thermal insulation I(cl) ranges from 0.63 to 2.01 clo) in two hot environments (40 °C, relative humidities: 30% and 45%). The observed and predicted mean skin temperature, core body temperature and sweat rate were presented and statistically compared. A significant difference was found in the metabolic rate between FIRE (firefighting clothing) and HV (high visibility clothing) or MIL (military clothing) (p < 0.001). Also, the development of heart rate demonstrated the significant effects of the exposure time and clothing ensembles. In addition, the predicted evaporation rate during HV, MIL and FIRE was much lower than the experimental values. Hence, the current PHS model is not applicable for protective clothing with intrinsic thermal insulations above 1.0 clo. The results showed that the PHS model generated unreliable predictions on body core temperature when human subjects wore thick protective clothing such as firefighting clothing (I(cl) > 1.0 clo). The predicted mean skin temperatures in three clothing ensembles HV, MIL and FIRE were also outside the expected limits. Thus, there is a need for further extension for the clothing insulation validation range of the PHS model. It is recommended that the PHS model should be amended and validated by individual algorithms, physical or physiological parameters, and further subject studies.

In order to explore the effects of constant and altered workload sequences on mental fatigue in a thermoneutral environment, experiments and surveys were carried out in this study. n‐back tasks were used to design different workload sequences. Fifteen healthy right‐handed males were required to experience three different workload sequences for 30 min, respectively, including a constant workload (2‐back task) and 2 altered workload sequences that contained an elevating workload sequence (1‐2‐3‐back tasks) and a reducing workload sequence (3‐2‐1‐back tasks). The PANAS, VAS‐F, and NASA‐TLX scales were selected to investigate changes in the mood, the perceived fatigue, and the perceived workload. Meanwhile, the skin temperature during these three workload sequences was continuously collected. Results from the NASA‐TLX scale indicated that no significant difference in total workload was observed among all three workload sequences. Meanwhile, results from the VAS‐F scale showed that no significant changes in self‐reported mental fatigue were observed among these three workload sequences, which meant that mental fatigue was only related to the total workload. However, self‐reported "energy" from the VAS‐F scale did not reduce significantly during the reducing workload sequence, which meant that the reducing workload sequence could conserve more "energy" than that of the elevating and constant workload sequences. Furthermore, both positive and negative moods changed significantly under the constant workload sequence (2‐back task), but they did not show much changes under altered workloads, which meant that the altered workload sequence could attenuate the mood deterioration. What is more, the mental demand, physical demand, temporal demand, effort, and the total workload increased significantly after both the constant workload and elevating workload sequence, but no significant changes in all these six items of the NASA‐TLX scale were observed under the reducing workload sequence. Finally, the mean skin temperature under the constant workload sequence was lower than that under the altered workload sequences (p > 0.05), but significant changes in skin temperature at the left hand and neck were only observed between the constant and reducing workload sequences. In conclusion, constant and altered workload sequences contributed equally to the mental fatigue in a thermoneutral environment, but the differences in workload sequence produced some differences in mood, energy, and mental demand, which would affect the working performance. Findings of this study provided implications for the proper planning, assignment, and management of tasks in real working settings. [ABSTRACT FROM AUTHOR]

Heat stress is a common danger for people who work or exercise in hot environments. A Newton manikin was used to evaluate the cooling performance of five forced air ventilation garments (AVGs) with newly designed eyelet sizes and positions, including no eyelets (control), small eyelets at the mid-back, large eyelets at the mid-back, small eyelets at both the mid-back and upper front, large eyelets at both the mid-back and upper front (abbr. CON, B1, B2, FB1, FB2, respectively). The AVGs in fans turned on (Fan-On) and turned off (Fan-Off) were measured in a constant temperature mode (CT, 34 °C, 69% RH, and 0.20 m/s) and a thermoregulatory control mode (TMC, 30 °C, 69% RH, and 0.2 m/s) to simulate human exercising and resting. Air volume between the skin and clothing was also measured using a 3 D laser scanner. FB1 resulted the highest heat loss both in the chest zone (109.2 W/m2) and the stomach zone (77.1 W/m2) in the Fan-On conditions, and it also resulted the lowest torso skin temperature, mean skin temperature and core temperature. The air volume of the eyelet designs in Fan-On was all reduced when compared to that of CON, with FB2 having the greatest reduction by 14.5%. The eyelet designs significantly reduced clothing bulkiness (p < 0.05), but had no significant effect on the torso heat loss (p > 0.05). [ABSTRACT FROM AUTHOR]

This study proposed an extended multi–layer heat transfer model to simulate skin burns of firefighters during firefighting. The proposed model takes into account the effect of fabric movement frequencies, fabric movement amplitudes and human body movement speeds on the heat transfer between the skin and the heat source under low–level radiative exposure. The simulation performance was validated against the simulations in the published literature in terms of the heat transfer in the multi–layer fabric system, skin temperature and skin burns. The results indicated that the fabric periodic movement caused by human body movement decreased the time to skin burns and the skin temperature increased with increasing fabric movement amplitude. During firefighting, the time to 2nd degree burn was 33.3–35.2% shorter at medium human body movement speed than at low and high movement speeds. Furthermore, at low movement speeds, the time to 2nd degree burn was negatively associated with fabric movement amplitude, whereas it was delayed by 12.9–29.8% at the fabric movement amplitude of 2.5 mm at medium and high human body movement speeds. This research provides foundational knowledge for the development of a new generation of firefighters' protective clothing (FPC) and the assessment of skin burns in firefighters. [ABSTRACT FROM AUTHOR]

Manual performance and body temperature responses were assessed in a 1-h trial at an ambient temperature (TAMB) of −40°C for 7 male participants (32 ± 14 (mean ± SD) years) wearing a typical military extreme cold protection clothing ensemble. The purpose was to establish duration limited exposure (DLIM) for these conditions, and it was hypothesized that (i) core temperature (TCORE) would remain normothermic, whereas extremity skin temperature (TSK) would decrease; (ii) decrements of manual performance would be in proportion to decreases of hand TSK; and (iii) DLIM would be determined by the hand or foot TSK responses. Linear regression was employed to assess associations of manual performance scores and body temperatures with DLIM assessed using the Required Clothing Insulation (IREQ) model and extremity temperatures in ISO 11079–2007. Results showed TCORE remained at ~37.3°C, whereas there were significant (0.0001 < p < 0.05) decreases in extremity TSK. Associations between manual performance and hand TSK showed coefficients of determination (R2) ranging from 0.48 < R2 < 0.98; 0.00005 ≤ p ≤ 0.08. The DLIM for the whole-body ensemble ranged from 2.2 h to > 8 h, whereas the DLIM for the extremities was 0.56 ± 0.20 h for TSK decreasing 15°C. In conclusion, the hypotheses of a stable core temperature and decreases of extremity skin temperature giving decrements in manual performance were accepted as was the hypothesis that duration limits for exposure would be determined by extremity skin temperatures of the hand and foot. [ABSTRACT FROM AUTHOR]

The design of workwear has significant effects on worker performance. However, the current workwear for coal miners in Northern China is poor in fitness and thermal comfort. In this study, new workwear (NEW) for coal miners was developed with the design features providing better cold protection and movement comfort performance, as compared with a commonly worn workwear (CON). To evaluate the effectiveness of NEW, we conducted human trials which were performed using simulated work movements (i.e., sitting, shoveling, squatting, and crawling) in a climate chamber (10°C, 75% RH). Physiological measurements and perceptual responses were obtained. The results demonstrated that the local skin temperatures at chest, scapula, thigh, and calf; mean skin temperatures,; and thermal comfort in NEW were significantly higher than those in CON. NEW also exerted an improvement in enhancing movement comfort. We conclude that NEW could meet well with the cold protective and mobility requirements. [ABSTRACT FROM AUTHOR]

Effects of clothing size and air ventilation rate on the cooling performance of three air ventilation jackets (size small, medium and large) were investigated. Two ventilation rates were chosen: low ventilation (12 L/s) and high ventilation (20 L/s). A significant difference in the dry heat loss at the upper body excluding the head and hands (UBody) was noted among the three sizes (p < 0.05). The ventilation rate significantly increased the total UBody heat loss and thereby reduced UBody's apparent evaporative resistance (p < 0.05). Clothing size showed varied impact on the UBody heat loss and the impact varied with air ventilation rates. Air ventilation could greatly reduce predicted core temperatures, mean skin and UBody temperatures in both sizes small and large. In contrast, clothing size had almost no impact on predicted thermophysiological responses in high ventilation. This work may be useful for designing and improving high-performance air ventilation clothing. [ABSTRACT FROM AUTHOR]

It is well known that uncompensable heat stress greatly impairs endurance and team sport-related performance because an increase in the core temperature directly induces a greater magnitude of the central fatigue in the heat than in thermal neutral environments. Numerous studies have been conducted in an attempt to discover reliable cooling strategies for improving endurance performance and repeated sprint ability while exercising in the heat. Whole-body pre-cooling has been shown to improve endurance performance in both dry and humid heat. Despite this, the reduction in thermal perceptions associated with pre-cooling gradually narrows during intense exercise. Hence, effective per-cooling strategies to improve athletic performance in the heat are required. Unfortunately, due to practical issues, adopting pre-cooling approaches as a per-cooling (cooling during exercise) modality to improve athletic performance is impractical. Thus, we sought to examine the impact of head, neck and face cooling on athletic performance in heat. According to current evidence, cooling the head, neck and face reduced local skin temperature in the areas where cooling was applied, resulting in improved local perceptual sensations. In the heat, neck cooling during exercise improves athletic performance in both endurance and team sports athletes. Furthermore, from a practical standpoint, neck cooling is preferred over head, face and combined head/face and neck cooling for both endurance and team sport athletes in the heat. Nonetheless, for all athletes who have access to water, face cooling is a recommended cooling strategy. There is a lack of research on the systematic selection of per-cooling modalities to improve athletic performance based on environmental conditions and the nature of sports. In addition, powerful but portable head, neck and face cooling systems are urgently needed to assist athletes in improving their performance in hot conditions. [ABSTRACT FROM AUTHOR]

An advanced three-dimensional (3D) human thermoregulation model was developed to depict the temperature distribution throughout the skin surface and inside the body. In this model, the human body was divided into 15 segments and the geometries of limbs were modeled as truncated circular cones to mimic physical geometries of upper arms, forearms, thighs, and lower legs. In the present model, heat conduction through the interfaces between the adjacent segments was considered, and the thermal conductivity of each segment was considered as a function of segmental temperature. Moreover, the boundary condition all over the human skin surface varied with respect to the local position, and the heat exchange between skin and its surrounding environment depended on the local skin temperature and the corresponding segment temperature. This 3D model was later validated against the documented experimental data where a good agreement was found. Therefore, the present 3D thermoregulatory model could be used to predict skin and core temperatures in various settings (different environments, clothing & activities) with a good accuracy. This 3D model could visualize the detailed temperature distributions over the whole skin and inside the human body, which could contribute to the study of local thermal comfort and smart clothing design. [ABSTRACT FROM AUTHOR]

Footbath has been a common form of activity in China, Egypt and India for several hundred years. The beneficial effect of footbaths on sleep has been already known. However, the optimal footbath conditions for improving sleep quality have received little attention. To investigate the effect of water temperature and footbath duration on body temperature responses during and after footbath using a thermoregulatory modelling approach. A classical multi-node human thermoregulation model was modified to account for human exposure to warm water locally while seated during a footbath. The model was then used to systematically examine the effects of water temperature and footbath duration on body temperature responses during footbaths as well as to estimate the most optimal footbath duration in different water temperatures to improve sleep. This thermoregulatory modelling study revealed that the mean skin temperature after a footbath was higher than before, whereas the core temperature after footbath was lower. The higher the water temperature and duration of the footbath, the longer time that the core temperature was maintained with a decreasing trend while the core temperature was higher. The mean skin temperature would no longer rise if there was sweating during the footbath. The onset of sweating was roughly inversely proportional to the temperature of the water. The discrete thresholds thermoregulation model was able to predict body temperature responses during a footbath. A relationship curve between sweating onset time and water temperature has been established to determine the optimal conditions of footbath, which may provide reference to facilitate sleep onset. [Display omitted] • A classical thermoregulatory model was extended to predict body temperature during footbath. • Footbath increased mean T skin , DPG and decreased T core thus improved sleep. • Optimal duration of footbath at 42 °C was 24 min when sweating just occurs. • Heat can be transferred from the feet to the whole body effectively during footbaths. • The optimal footbath duration is determined by the sweating onset time. [ABSTRACT FROM AUTHOR]

The study aimed to examine the effect of a hybrid personal cooling garment (PCG) on improvement of thermal comfort of office workers in a hot indoor environment. Eleven male subjects underwent two 90-min trials with one in PCG (i.e., with the hybrid personal cooling garment) and another with no cooling (i.e., CON). The trials were performed in a climate chamber with an air temperature of 34.0 ± 0.5 °C, relative humidity of 65 ± 5% and an air velocity of 0.15 ± 0.05 m/s. It was found that the hybrid PCG could remarkably improve the whole-body thermal sensations (TSs), skin wetness sensations (WSs) and comfort sensations (CSs) during most of time of the trials compared with CON (i.e., from the 10th min to the 40th min and from the 70th min to the 80th min for TSs, from the 10th min and the 20th min to the end of the test for WSs and CSs, respectively) ( p < 0.05). The upper-body and lower-body TSs, WSs and CSs were all significantly improved in PCG from the 10th min to the end of the test ( p < 0.05). In addition, mean skin temperatures and the total sweat production were also significantly reduced in PCG ( p < 0.05). In summary, the hybrid PCG was highly anticipated to improve thermal comfort of office workers while doing office work in the studied hot and moderate humid indoor environment. [ABSTRACT FROM AUTHOR]

Machine learning-based human thermal comfort prediction is becoming increasingly popular as artificial intelligence (AI) technologies advance. Human skin temperature is a critical physiological factor in thermal comfort research. In winter, we developed a thermal comfort prediction model based on skin temperature and environmental factors. During the experimental phase, the superior performance of the proposed method is demonstrated through a comparative study that includes four different state-of-the-art models, including Support Vector Machine, Decision Tree, Ensemble Algorithms, and K-Nearest Neighbor. With all variables as inputs, the actual accuracy of the proposed thermal sensation vote (TSV) model prediction is 95.8%. In addition, the hyperparameters of machine learning algorithms were tuned using a personal classification model based on the Bayesian Optimization technique. This study demonstrates the model's capability of predicting individual thermal comfort. • The impact of four algorithms on the performance of thermal comfort models. • The models using environmental and biological data as input reached the highest accuracy. • The maximum accuracy of optimization models using BO technology is 13.3%. [ABSTRACT FROM AUTHOR]

With the development of urbanization, the development of deep underground spaces has become increasingly important. The purpose of this research is to study how the combined effects of thermal and acoustic environments affect psychological and physiological stress of workers in deep undergrounds spaces. A randomized crossover chamber study with 16 subjects was carried out in this study. Participants were exposed to two different temperatures (30 and 34 °C), two different relative humidity levels (65 and 85%), and three different noise levels (55, 70 and 85 dBA). The experimental protocol included subjective thermal sensation, emotion, heart rate variability, skin temperature and cognitive performance tests. Results showed that temperature and relative humidity affected the change of emotion via their influence on thermal responses. In deep underground spaces, participants were always in a state of tension. The effect of temperature on low to high frequency ratio (LF/HF) was more pronounced at high noise levels. Low relative humidity could compensate for the discomfort caused by high temperatures. In general, temperature had the greatest influence, and the combined effect was significantly greater than the individual effect on workers' psychological and physiological stresses. • Combined effects of thermal and acoustic environments in deep underground spaces. • Using emotion and heart rate variability to explore to subjects' psychological and physiological stress. • Temperature and relative humidity will indirectly affect emotion changes. • The combined effects of temperature, relative humidity and noise are greater than the individual effect. [ABSTRACT FROM AUTHOR]

Abstract: Clothing evaporative resistance is an important input in thermal comfort models. Thermal manikin tests give the most accurate and reliable evaporative resistance values for clothing. The calculation methods of clothing evaporative resistance require the sweating skin surface temperature (i.e., options 1 and 2). However, prevailing calculation methods of clothing evaporative resistance (i.e., options 3 and 4) are based on the controlled nude manikin surface temperature due to the sensory measurement difficulty. In order to overcome the difficulty of attaching temperature sensors to the wet skin surface and to enhance the calculation accuracy on evaporative resistance, we conducted an intensive skin study on a thermal manikin ‘Tore’. The relationship among the nude manikin surface temperature, the total heat loss and the wet skin surface temperature in three ambient conditions was investigated. A universal empirical equation to predict the wet skin surface temperature of a sweating thermal manikin was developed and validated on the manikin dressed in six different clothing ensembles. The skin surface temperature prediction equation in an ambient temperature range between 25.0 and 34.0°C is T sk =34.0–0.0132HL. It is demonstrated that the universal empirical equation is a good alternative to predicting the wet skin surface temperature and facilitates calculating the evaporative resistance of permeable clothing ensembles. Further studies on the validation of the empirical equation on different thermal manikins are needed however. [Copyright &y& Elsevier]

Although the phenomena of temporal alliesthesia and spatial alliesthesia have been widely examined over the past few decades, the synergy effect of them on thermal comfort was seldom explored. In this work, human subjective responses were obtained from 16 acclimatized subjects (8 males & 8 females) to examine the synergy effect of temporal and spatial alliesthesia on thermal comfort. By regressing local skin temperatures and thermal sensation votes (TSVs), the goodness of fit R2 between skin temperatures to TSVs was determined. Quantitative analysis of the synergy effect of temporal alliesthesia and spatial alliesthesia in an air-conditioned temporarily occupied space (TOS) chamber was performed. Results showed that TSV (p <.05) and thermal comfort votes (TCVs) (p <.05) are better able to explain the temporal and spatial alliesthesia as compared to thermal preference votes (TPVs). The R2 between local skin temperature and TSVs at forehead (0.76), hand (0.74), thigh (0.80) and calf (0.83) were greater than that between local TSVs and mean radiant temperature (MRT) (0.63). The heating temperature setpoint might be reduced to 16 °C by the use of a non-adjustable heated chair in air-conditioned TOS to maintain the thermal comfort of guests (insulation: around 1.5 clo, metabolic rate: around 1.0 met, stay for less than 40 min). Meanwhile, occupants in the air-conditioned TOS chamber could maintain thermal comfort at 14 °C for half the time (25 min) that it does at 16 °C. The findings in this work might help achieve energy efficient thermal comfort and develop design guidelines for air-conditioned TOS equipped with heated chairs. • Synergy effects of temporal and spatial alliesthesia in TOS were studied. • Goodness of fit between skin temperature and TSVs was calculated. • Heating temperature setpoint in TOS chamber could be adjusted to 16 °C. • Occupants' thermal comfort could last 25 min at 14 °C in the TOS chamber. [ABSTRACT FROM AUTHOR]

This study presents a complete virtual three-dimensional (3D) model of human thermophysiological responses by integrating detailed heat dissipation model from human skin to environment through spatially heterogeneous (realistic) clothing into human thermoregulation model by two-way coupling. The model considered various heat and mass transfer mechanisms in air and clothing layers such as conduction, natural convection, forced convection, radiation, and evaporation. The numerical setup of the model was presented and simulated using ANSYS Fluent. The developed model is systematically validated against experimental data obtained from authors of published literatures. To demonstrate the robustness and accuracy of the model, it has been validated for a wide range of ambient temperatures (−10.0 to 45 °C), relative humidity (25–86%), activity levels (0.8–3.5 mets), clothing thermal resistances (0.10–2.95 clo), and evaporative resistances (11.5–800 Pa m2/W) including steady-state and transient exposures. This complete 3D model predicted human thermophysiological responses for a wide range of ambient condition with good accuracy. The average RMSD (root mean square deviation) of predicted core and mean skin temperatures was 0.21 °C (maximum RMSD = 0.33 °C) and 0.56 °C (maximum RMSD = 1.03 °C), compared to average standard deviation in measured data 0.26 °C and 0.58 °C, respectively. The model is also able to predict the local skin temperature with an average RMSD of 0.64 °C. Therefore, this newly developed model can be served as a useful tool in analysing human thermophysiological responses and heat stress for any given thermal environment and clothing setting. • A complete virtual 3D thermoregulation model was developed using CFD. • Average RMSD of predicted core and mean skin temperatures was 0.21 °C and 0.56 °C. • The established model is a useful tool for analysing human thermal comfort. • Model is validated against data obtained from authors of published literatures. [ABSTRACT FROM AUTHOR]

Face and neck cooling has been found effective in improving thermal comfort during exercise in the heat despite the fact that the surface area of human face and neck regions accounts for only 5.5% of the entire body. Presently very little documented research has been conducted to investigate cooling the face and neck only to improve indoor thermal comfort. In this study, two highly energy efficient wearable face and neck cooling fans were used to improve occupant thermal comfort in two warm indoor conditions (30 and 32 °C). Local skin temperatures and perceptual responses while using the two wearable cooling fans were examined and compared. Results showed that both cooling fans could significantly reduce local skin temperatures at the forehead, face and neck regions by up to 2.1 °C. Local thermal sensation votes at the face and neck were decreased by 0.82–1.21 scale unit at the two studied temperatures. Overall TSVs decreased by 1.03–1.14 and 1.34–1.66 scale units at 30 and 32 °C temperatures, respectively. Both cooling fans could raise the acceptable HVAC temperature setpoint to 32.0 °C, resulting in a 45.7% energy saving over the baseline HVAC setpoint of 24.5 °C. Furthermore, occupants are advised to use the free-control cooling mode when using those two types of wearable cooling fans to improve thermal comfort. Finally, despite some issues on dry eyes and dry lips associated with those wearable cooling fans, it is concluded that those two highly energy-efficient wearable cooling fans could greatly improve thermal comfort and save HVAC energy. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) multi-segment hand-specific thermoregulation model was developed as a fundamental tool for spatial and temporal skin temperature prediction. Cold-induced vasodilation in fingers was simulated by superimposing symmetrical triangular waveforms onto the basal blood flow. The model used realistic anatomical, physiological, and thermo-physical information of a standard human hand and forearm. The inhomogeneity of hand thermal and physiological properties was considered by dividing it into 17 segments: palm, dorsal, forearm, and five fingers, with each finger subdivided into fingertip, middle segment, and finger root except for the thumb, which has no middle segment. Each segment contained a bone core and an outer soft tissue layer. 3D scanning technology was employed to develop the geometrically realistic model of the hand and the bone. The thermo-physical and physiological properties of each segment and layer were obtained from a photogrammetric analysis of anatomic atlases and from literature. Heat transfer throughout the hand by metabolism, blood perfusion, and conduction between the tissue was considered. Heat loss by convection and radiation from the skin and the protective effects of gloves were also included in the model. The model showed good agreement with experimental data from the literature. The developed 3D hand model fills the knowledge gap and builds a bridge between existing knowledge of the hand's physiology and its application, providing a science-based tool for decision making. The understanding from model studies may also help enhance the wearer's working efficiency, safety, health, and wellbeing while working in indoor and outdoor cold environments. • A 3D multi-segment hand-specific thermoregulation model is developed. • The model is a more realistic representation of the hand's anatomy and physiology. • The model accounts for the hand's inhomogeneity by dividing it into 17 segments. • Cold-induced vasodilation (CIVD) in fingers was simulated. • The model predicts the spatial and temporal skin temperature accurately. [ABSTRACT FROM AUTHOR]

The effect of four cooling strategies on cooling performance of a hybrid personal cooling system (HPCS) incorporated with phase change materials (PCMs) and electric fans in a hot environment (i.e., T air = 36 ± 0.5 °C, RH = 59 ± 5%) was investigated. Twelve healthy young male participants underwent four 90-min trials comprising 70 min walking and 20 min resting periods. Cooling strategies adopted in this work were CON (control), PCM-control (PCMs were removed at the end of exercise), Fan-control (fans were switched OFF during the initial 20 min) and PCM&Fan-control (fans were turned ON after 20 min exercising and PCMs were removed after the 70-min exercise). Results demonstrated that the control of electric fans could suppress the mean skin temperature rise to 34.0 °C by over 15 min and also cut down the energy consumption of the HPCS from 15.6 W h to 12.1 W h over the entire 90-min trials. Thus, it is recommended that fans should be turned off at the beginning of hot exposure and switched on once participants felt warm. Our findings also showed that the removal of fully melted PCM packs from the HPCS could enhance the evaporative cooling effect brought about by air circulation. The removal of melted PCMs significantly reduced the physical load by 37.3% and ratings of perceived exertion (RPE) were decreased by 3.5–4.2 RPE units. This could also help quickly restore the PCM energy for future usage. In summary, cooling strategies demonstrated in this work could improve HPCS's overall cooling performance on workers while working in the studied hot environment. • Effect of cooling strategies on HPCS's performance was examined. • Fan control could suppress skin temperature rise to 34 °C by > 15 min. • Fan control could also cut down energy consumption by 3.5 W h. • PCM control reduced 37.3% physical load and RPE ratings by 3.5–4.2 units. • Cooling strategies chosen for this work could improve HPCS's overall performance. [ABSTRACT FROM AUTHOR]

Personal heating clothing systems (PHCS) incorporated with electrical heating elements have shown its great potential to help occupants attain thermal comfort in cold built environments. Presently there is a lack of a comprehensive study to optimize the PHCS's performance. In this work, a newly developed complete 3D model was used to systematically examine the factors affecting the PHCS's heating performance in various cold unheated built environments. Effects of ambient temperature, clothing insulation, heating power, heating mode and metabolic rate on the PHCS's performance were investigated by performing a numerical parametric study. Validation data have demonstrated that the 3D model could precisely predict human thermophysiological responses while wearing PHCS in the built environment. At 15.0 °C indoor temperature and metabolic rate of 1.6 met, wearing a PHCS with thermal insulation of 1.0 clo and heating power of 20 W could help occupants attain thermal comfort. It was also found that compared with continuous heating, intermittent heating at a high heating frequency could contribute to saving energy without compromise of body temperature reduction. Furthermore, metabolic rate has a significant impact on thermophysiological responses and the mean heaters' temperature. Hence, the selection and operation of a PHCS should be based on the nature of occupant activities. Occupants are advised to adjust the heating power to a lower level when performing more demanding activities because the need for auxiliary heating is not as high as that in the case when occupants are resting or performing seated office activities. • A 3D model was used to study effects of temperature, insulation, heating power & mode, metabolic rate on PHCS's performance. • At 15.0 °C, wearing 1.0 Clo PHCS with 20 W heating power could help occupants attain thermal comfort (M =1.6 met met). • Intermittent heating operated at higher frequency could contribute to saving energy without compromise of skin temperatures. • Metabolic rate has a significant impact on thermophysiological responses and heaters' temperature. • Occupants are advised to adjust the heating power to a lower level when performing slightly more demanding indoor activities. [ABSTRACT FROM AUTHOR]

Thermal comfort dictates our alliesthesia and behavioural responses in indoor environments with the primary aim of maintaining the thermal homeostasis of our human body. The recent advances in neurophysiology research have suggested that thermal comfort is a physiological response that is regulated by the deviations of both skin and core temperatures. Therefore, when conducting thermal comfort using indoor occupants in an indoor environment, proper experimental design and standardisation should be followed. However, there is no published source that provides an educational guideline on how to properly implement the thermal comfort experiment in an indoor environment using indoor occupants (normal occupational activities and during sleep in a home-based setting). Therefore, the primary purpose of this work is to illustrate how to conduct indoor thermal comfort related experiments using human trials in both normal occupational activities and during sleep in a home-based setting. Furthermore, we hope that the information presented in this article will result in better experimental design when conducting the experiment on thermal comfort using indoor occupants (occupational and home-based environments). Due to this reason, special emphasis will be focused on the experimental design, selection of participants and experimental standardisation. The key summary of this article is that thermal comfort related to indoor occupants in an indoor environment should perform priori sample analysis and follow the proper experimental design and standardisation as outlined in this article. [Display omitted] • Guidelines on how to conduct indoor thermal comfort tests using human trials are presented. • Fundamental rules of experimental design and standardisation are outlined. • Researchers should conduct a priori analysis of sample size when designing experiments. • A check list of the experimental planning stage and pre-trial standardisation is provided. [ABSTRACT FROM AUTHOR]

• Measuring methods from contact manner to non-contact manner were reviewed. • The development of Euler video magnification technology was retrospected. • Skeleton keypoints model was retrospected. • Non-contact measurements for personalized thermal comfort were discussed. • Non-contact measurements for demand oriented HVAC systems were discussed. Heating, ventilation and air-conditioning (HVAC) systems have been adopted to create comfortable, healthy and safe indoor environments. In the control loop, the technical feature of the human demand-oriented supply can help operate HVAC effectively. Among many technical options, real time monitoring based on feedback signals from end users has been frequently reported as a critical technology to confirm optimizing building performance. Recent studies have incorporated human thermal physiology signals and thermal comfort/discomfort status as real-time feedback signals. A series of human subject experiments used to be conducted by primarily adopting subjective questionnaire surveys in a lab-setting study, which is limited in the application for reality. With the help of advanced technologies, physiological signals have been detected, measured and processed by using multiple technical formats, such as wearable sensors. Nevertheless, they mostly require physical contacts with the skin surface in spite of the small physical dimension and compatibility with other wearable accessories, such as goggles, and intelligent bracelets. Most recently, a low cost small infrared camera has been adopted for monitoring human facial images, which could detect the facial skin temperature and blood perfusion in a contactless way. Also, according to latest pilot studies, a conventional digital camera can generate infrared images with the help of new methods, such as the Euler video magnification technology. Human thermal comfort/discomfort poses can also be detected by video methods without contacting human bodies and be analyzed by the skeleton keypoints model. In this review, new sensing technologies were summarized, their cons and pros were discussed, and extended applications for the demand-oriented ventilation were also reviewed as potential development and applications. [ABSTRACT FROM AUTHOR]