Human Thermal Responses Research Articles

Differences in human thermal and physiological responses under corridor and greenway in summer in guangzhou

As urbanization and the heat island effect intensify, comfortable and healthy outdoor micro-environments are particularly important for sustainable urban development, encouraging more outdoor activities. Fewer studies have focused on differences in thermal comfort and thermal physiology of users in potential outdoor open spaces. Therefore, this study aims to examine the differences in thermal comfort and thermal stress among users of common outdoor open shady spaces, contributing towards a better thermal experience and mitigating heat stress. In this study, a field investigation of corridors and greenways was conducted on a campus in Guangzhou in the summer based on subjective questionnaires and objective measurements of thermal environment, and thermal physiological parameters. The results found that people were more likely to experience good thermal comfort and weaker intensity of thermal stress in corridors with significant differences in physiological responses. Furthermore, the upper limit comfort temperatures of the corridor and greenway were 34.0 and 33.4 °C, respectively. In addition, it can be concluded that the corridor was a more optimal space for outdoor shade before evening, whereas the greenway was more optimal in the evening in summer. The findings determine the thermal benchmarks for typical outdoor shady spaces in hot and humid regions in summer, which can help designers create comfortable outdoor public spaces that improve thermal comfort and people's health.

Research on ventilation cooling design driven by human thermal response in high geothermal temperature tunnel construction

Constant high temperature conditions in tunnel not only significantly reduced the labor efficiency of workers but also affected their physical and mental health. However, the traditional design of ventilation and cooling for high geothermal tunnel construction only considers the control of environment temperature and ignores the thermal comfort state of the workers, which will increase the potential risk of tunnel safety accidents. Therefore, this paper adopted the methods of scene testing, theoretical analysis and numerical simulation to establish a modified evaluation model applicable to the thermal comfort of workers in high geothermal tunnels. By analyzing the temperature distribution pattern of heat-sensitive parts of workers engaged in different labor intensity under different air supply parameters, the design strategy for ventilation and cooling of high-temperature tunnels was refined on the basis of ensuring that the environment temperature and thermal comfort meet the requirements. The results show that ventilation design parameters that satisfy the environmental temperature control criteria are equally adequate for worker thermal comfort at light-intensity work. However, when the ambient temperature is higher than 40 °C, the thermal comfort of workers engaged in medium-intensity work still does not meet the requirements, even if the ambient temperature already meets the criteria. It is recommended that the wind speed be increased by at least 8.3 %, 15.6%and 28.6 % for ambient temperatures of 40 °C, 45 °C and 50 °C, respectively. More effective cooling techniques should be tried to further enhance thermal comfort for workers engaged in heavy workloads especially in hot environments exceeding 40 °C.

Investigating the impact of a large river and its surrounding contextual conditions on pedestrians’ summer thermal perceptions in a Cfa-climate city

Thermal comfort studies are usually employed to find subjective thermal responses [indicated by neutral temperature (NT), i.e. the temperature with no thermal stress] of residents from a region towards thermal environments. According to the recently published works in the literature, NTs are affected by many factors, such as geographical location and microenvironments. To elucidate the origins of these effects, the impact of microenvironment elements around a water surface on pedestrians’ thermal perceptions was systematically investigated in this work. The Fujiang River (FJR) in Mianyang City was taken as the sample site. The municipal meteorology station is located next to the site by around 2.5 km. By performing meteorology measurements combining questionnaires, it was found that the riverside NT (indicated by physiologically equivalent temperature, PET) of Mianyang in the summer of 2023 was 21.4 °C. The relationship between the distance from the water (DFW) and NT was quadratic linear. The same phenomenon took place by using either PET or Universal Thermal Climate Index (UTCI) indexes. Meanwhile, the meteorological contexts also affected NTs, including relative humidity (RH) and air velocity (Va). Regarding RH, the NPET increased from 15.2 °C (RH = 50%) to 26.9 °C (RH = 90%). In contrast, the NPET dropped from 23.0 to − 50.6 °C when the Va increased from 0.2 to 2.5 m/s, respectively. From our analysis, it was demonstrated that human thermal responses are significantly affected by both the microenvironmental and meteorological backgrounds around the water surface. Our work provides valuable insights for the proper use of water surfaces in urban design for adjusting thermal comfort.

Study on personal comfort heating system and human thermal comfort in extremely low-temperature building environments

Exposure to extremely low-temperature building environments around −20 °C causes various hazards to human health. However, few studies have studied human thermal comfort and physiological response in such environments, nor the personal comfort heating system. Thus, this study investigated the heating characteristics of personal comfort heating system and their effects on thermal responses and thermophysiological parameters in extremely low-temperature building environments. We conducted experimental tests and questionnaires in a cryogenic enthalpy difference laboratory with air temperature ranging from −21.2 to −15.6 °C and a relative humidity of 55 %. Eight experimental conditions were designed with several heating measures (heating mat, heating gloves, heating cushion and airwarmer). The heating parameters of the personal comfort heating systems as well as the subjective evaluations and skin temperature of the subjects were recorded and analyzed. The results showed that the airwarmer confinement box condition had a corrective power of up to 38.3 K. The overall thermal sensation vote and overall thermal comfort vote were maintained at 0.25 and −0.25. Further, we found that the face, hands, calves and feet got cold easier with the largest skin temperature difference of −4.9, −8.1, −6.7 and −7.6 °C, respectively. Besides, the relationships between thermal responses and between thermal responses and skin temperature were examined, as well as a thermal comfort assessment methodology was established for extremely low-temperature environments.

Use a smartphone app for predicting human thermal responses in hot environment

The object of this study is to predict of human thermophysiological state in hot environment to prevent heat stress or heat stroke. A key issue is the need to design effective tools for heat stroke risk assessment taking into account environmental conditions, physical activity, characteristics of human clothing and protective equipment. A mobile application has been developed, which, unlike existing analogs, provides users with data on the safe time of human under selected environmental conditions. The mobile application uses the method of mathematical modeling to predict important indicators of human thermophysiological state: body temperature, sweat evaporation, body water loss. The mathematical model takes into account the generation of metabolic heat, the transfer of heat inside the body, and the heat exchange of a human with the environment. This paper reports the results of using a mobile application for predicting human thermal responses under hot environmental conditions. With the help of the application, it was possible to determine the time of a human's safe stay depending on the intensity of his/her activity and the characteristics of his/her clothing. It is shown that walking at a speed of 6 km/h in a military uniform is safe for 1 hour at an air temperature of 36 °C. Running at a speed of 8 km/h under such conditions becomes risky already after 15 minutes due to overheating of the human body. The developed information technology is designed to warn about heat stress or heat stroke of people who are under hot conditions in order to preserve their health and work capacity. The received predicting data should be considered as one of the theoretical measures to prevent human heat stress under hot environmental conditions

High-temperature and thermal radiation affecting human thermal comfort and physiological responses: An experimental study

Hot environments with high temperatures and thermal radiation are to be found in heat treating, glass melting workshops, etc., which impacts worker thermal comfort and physiological responses. The motivation of this study was to explore the changes of thermal comfort in a high-temperature and thermal radiation environment. Four experimental cases were designed to simulate high temperatures and thermal radiation. Physiological parameters such as skin temperature, ear cancel temperature, heart rate, and weight loss were investigated. Evaporative heat losses and skin wettedness were calculated by Gagge's two node model or weight loss. The results showed that local and mean skin temperatures increased by approximately 4 °C during the exposure. Thermal sensation vote was positively correlated with WBGT. The dynamic relationship between human heat gain, evaporative heat loss and potential thermal risk was framed as Stage A, Stage B, and possibly Stage C. This study could provide the basic information and theoretical evidence for the thermal comfort and thermal risk in high-temperatures and thermal radiation environment.

The climate backgrounds of urban migrants affect thermal response

Human thermal responses can vary based on individuals' thermal histories. Although comparative studies on thermal comfort have been conducted in different regions, research is still limited regarding the differences in thermal responses among people living in the same city but having emigrated from diverse climates. Addressing this gap, this study, conducted in Beijing between 2021 and 2022, involved on-site meteorological measurements and questionnaire surveys, collecting a total of 1,370 questionnaires. The objective was to examine the differences in thermal response among individuals from different climatic backgrounds post-migration and assess the implications for urban design improvements. The study findings revealed the following: 1) Southern migrants exhibited a higher neutral Universal Thermal Climate Index (UTCI) compared to northern migrants (20.2 °C vs. 18.7 °C). 2) In terms of the acceptable temperature range (TAR) for 1 h, southern migrants showed a greater tolerance for hot conditions compared to northern migrants (4.4–30.8 °C vs. 0.6–28.6 °C), but less tolerant for cold conditions. 3) The transient acceptable range was considerably wider than the 1-h TAR. 4) Residents feeling thermally neutral at present had lower demands for urban design improvements. Our results highlight the importance of considering diversity of thermal response and implementing targeted management and planning interventions. The study is expected to provide practical recommendations for creating more livable and sustainable urban environments.

Biophysical Characterization and Predicted Human Thermal Responses to U.S. Army Body Armor Protection Levels (BAPL) <br>

Biophysical Characterization and Predicted Human Thermal Responses to U.S. Army Body Armor Protection Levels (BAPL) <br>

Comparison of indoor thermal environments and human thermal responses in Northern and Southern China during winter

Human thermal adaptability has a significant impact on energy savings and emission reduction in buildings. To investigate the effect of long-term thermal history on thermal adaptability, this study explored the characteristics of indoor thermal environments and the differences in human thermal responses during winter in northern and southern China. Furthermore, the effects of the region (heating patterns), building types and payment patterns on the thermal responses were clarified. Finally, the thermal neutral temperatures and 80 % thermal acceptable ranges were determined. The results indicate that there are significant differences in the indoor thermal environments and human thermal responses in different types of buildings during winter (P < 0.00). However, the effect size of the thermal responses (d ≥ 0.3) is lower than that of the environmental parameters (d ≥ 0.7). This demonstrates that individuals have strong thermal adaptability. Due to the higher indoor air temperature of district heating in northern China, the northerners have a higher thermal neutral temperature and lower clothing insulation. They are stricter in the requirements for room temperature and weaker in thermal adaptability. Nevertheless, the southerners can actively adapt to lower indoor temperatures by clothing adjustments, with a wider acceptable range of indoor temperatures and lower thermal neutral temperatures. Charging for the actual heating usage can lower the thermal neutral temperature and boost the thermal satisfaction rate, which is conducive to saving energy and reducing emissions. Thus, these findings can contribute to the promotion of the comfortable and sustainable development of built environments.

Dual effect of activity levels and temperature step-change on human comfort and recovery time: Simulated short-term commute in winter

Individuals living in a location with access to public transport and a short distance from the workplace tend to walk for short commuting. Human activity levels are affected by the rate of walking while commuting, which affects thermal comfort and response. To investigate the human thermal response in commuting, a climate chamber experiment was conducted to simulate outdoor commuting (13 °C) and indoor rest recovery (24 °C) in winter. Standing and walking at 4 and 6 km/h were used to simulate temporary rest, walking, and running, respectively. Twenty healthy participants were asked to simulate commuting (13 °C) with standing/low, 4 km/h/medium, and 6 km/h/high activity levels for 8 min and sitting (24 °C) for 32 min. The physiological parameters and subjective perceptions of the subjects were recorded. The results showed that there were differences in the sensitivity of the parameters to changes in activity levels and temperature steps. Thermal sensation and mean skin temperature responded considerably to the dual effect of activity levels and temperature up-step; however, blood pressure was exclusively sensitive to temperature step-change. The elevated activity level of 1 met may increase the recovery time by 5–10 min. Functional paradigms for psychological and physiological recovery times in a neutral environment were developed, which could provide a potential solution for improving thermal satisfaction and the assessment of recovery times. The results of this study will guide improvement strategies for physiological recovery and thermal comfort after commuting.

Outdoor thermal perception and heatwave adaptation effects in summer – A case study of a humid subtropical city in China

Heatwaves occur more frequently during the summer owing to global warming, which causes excessive heat stress and thermal discomfort. Heat stress increases overheating risk and impacts people's health and outdoor activities. Assessing outdoor thermal risk and clarifying human thermal responses under outdoor high-temperature conditions are of particular importance. However, the effect of thermal adaptation on people's thermal perception during heatwave conditions requires exploration. This paper aims to provide a comprehensive analysis of human outdoor thermal perception under non-heatwave and heatwave conditions to obtain adaptation-based outdoor thermal benchmarks to estimate the threshold for thermal discomfort and heat stress. Longitudinal and cross-sectional questionnaire surveys are carried out during the summer in public squares in Chongqing. The results showed that thermal perceptions undergo a dynamic change process in summer, which is closely related to an individual's past thermal experience. In comparison with thermal benchmarks under non-heatwave conditions, the neutral, comfortable, and 80% acceptable range of UTCI under heatwave conditions shifted to a higher temperature. For the heatwave period, the neutral UTCI range was from 21.5 °C to 27.9 °C. The modified UTCI ranges for heat stress classifications were obtained, including the 80% acceptable temperature range from 21.4 °C to 30.1 °C. The contributions of this study are in the method of determining outdoor thermal benchmarks in heatwave conditions and clarifying local people's thermal demands. These findings can provide more refined guidance for heat stress assessment and enrich the possibilities for urban design and urban resilience responses to heatwave conditions.

An individualized and multi-segmental bioheat model for predicting local conditions of the human body under various thermal environments

Thermoregulatory bioheat models have attracted the attention of researchers due to their conformity with the basis of human thermal perception. For this reason, various models have been presented, such as simplified thermoregulatory bioheat (STB), individualized thermoregulatory bioheat (ITB), and multi-segmental thermoregulatory bioheat (MSTB). In the present study and based upon previous models, an individual multi-segment thermoregulatory bioheat (IMTB) model has been introduced. In this model, the body is subdivided into 17 segments and 3 layers, with the blood circulatory system consisting of arteries, veins, and superficial veins. Also, IMTB can evaluate the individual parameters effects (such as height, weight, gender, and age) on physiological parameters and active/passive systems. Finally, this new model was evaluated in human thermal response predictions over a wide range of transient and steady-state environmental conditions (5.0<Tair(°C) <50.0, 31.0 < RH (%)<70.0) and various individual characteristics (male and female, 20 < age (years) < 69, 50<weight (kg) < 92, and 1.5<height(m) < 1.9). The results indicated that the new model agreed well with empirical data and the average mean absolute error (MAE) was 0.1, 0.5, and 0.3 °C for core, local, and mean skin temperature, respectively.

Effect of change rates and directions of air temperature ramps on thermal responses of occupants under warm summer conditions

Understanding thermal comfort in dynamic environments is vital for developing various air temperature control strategies that consider energy flexibility. However, studies on the quantitative effects of air-temperature change rates and directions on human thermal responses in thermal environments with temperature ramps (TRs) are limited. In this study, 22 sex-balanced young adults were recruited to investigate the thermal perceptions and physiological responses to room air TRs at rates of 0.10–0.30 °C/min in a climate chamber. The results revealed that the air temperature change direction had no effect on the mean skin temperature (Tskin) but significantly affected the thermal sensation vote (TSV), that is, the TSV was approximately 0.5 scales lower when the temperature was decreasing than when it was increasing (P < 0.05). Moreover, the slow change rates of Tskin within the range of ±0.07 °C/min had no significant effect on dynamic TSV, unlike that in step-change environments with higher change rates. The head was the most thermally sensitive body part with the highest TSV/Tskin values and change rates of Tskin (up to ±0.08 °C/min) in warm TR environments. In most cases, the thermal response of limbs was delayed. The thermal experience and adaptation levels of occupants may play essential roles in thermal perceptions within TR environments. Preliminary thermal comfort models suitable for hot summer climates were proposed in this study, which could be used in TR control strategies, such as intermittent cooling or demand response control.

THERMAL COMFORT ASSESSMENT FOR ADOPTING CONTROL STRATEGIES IN ATRIUM BUILDINGS

The atrium was seen in origin about two hundred years ago. Glazed areas and atrium structures have been considered a symbol of advanced technology in recent years, yet they can differ in terms of arrangement and functionality. Because of the complexity of their operation and air movement, atriums are difficult to diagnose and analyze in terms of thermal comfort. The present paper has a study on the thermal environment of atrium spaces. Thermal comfort is one of the foremost important aspects of indoor environmental quality thanks to its effects on well-being, people's performance, and building energy requirements. Since our responses to our thermal environment have a considerable effect on our performance and behavior, not least in the realm of work, there has been a considerable scientific investigation of those responses and formal methods are developed for environmental evaluation and style. Thermal sensations of the occupants occupying the interior space of the building were evaluated with various approaches to understanding indoor thermal comfort. Several metrics for assessing human thermal response to interior environment conditions have been assessed describing the human thermal perception of the thermal environment to which an individual or a group of people is exposed. The article study was to gain insight into the subject’s perspectives on variables of comfort levels and determine the factors responsible for the varying human thermal comfort summer. This paper is a study on the thermal environment of atrium spaces focusing on identifying the factors of thermal comfort and promoting Control measures that may be adopted in atrium buildings to reduce the energy potential.

Numerical simulation of cooling effect of human-PCM-clothing model in hot environments

Workers exposed to hot environment experiences physiological changes, implicating human health and occupational safety. Phase change material (PCM) cooling vest is effective for personal cooling and thermal comfort. In this paper, the human-PCM-clothing model was constructed by combining the bioheat model and the PCM-clothing model to predict the cooling effect of PCM on thermal response in hot environments. The multi-segmented human bioheat model considered the effects of high temperature on metabolic rate, blood flow rate, and dehydration on the sweating rate. The PCM-clothing model analyzed heat and mass transfer between the PCM and its thermal environment. The model was tested with published data and the relative errors between the simulated and measured results were below 2.2% for mean skin and 0.33% for core temperature. The numerical parametric study was investigated to study the effects of the melting temperature and latent heat of the PCM packages on heat transfer. PCM with high latent heat and appropriate melting temperatures benefits body cooling performance. The equation for the optimum solution corresponding to the latent heat of PCM at different melting temperatures was derived. This study can guide the choice of PCM packages and the human thermal response analysis in a hot environment.

Effects of constant and fluctuating temperature modes of foot heating on human thermal responses in cold environments

Heating demand has increased dramatically in winter in southern China. Foot heating pad, as a personal comfort system device enables to improve occupants’ thermal comfort in winter while consuming less energy. However, the research on the heating modes of these devices remains insufficient. The effects of fluctuating foot heating on thermal responses were compared to those of traditional constant heating in this study. A climate chamber experiment involving 16 subjects was conducted to assess physiological and psychological thermal responses under constant and fluctuating foot heating modes with equal total heating energy. Skin temperatures and thermal perception votes at three indoor temperature conditions of 8, 11, and 14 °C were collected and analyzed. The results indicate that the investigated parameters were significantly improved by foot heating, with foot skin temperature rose by 7 °C, foot thermal sensation rose by 2.7 levels, and overall thermal comfort rose by 0.4 level at least. Constant heating can improve skin temperature and thermal sensation to a higher extent than fluctuating heating in cold environments, especially when ambient temperature was lower than 12 °C. However, heating the foot alone cannot effectively improve overall thermal comfort in a cold environment below 12 °C. With ambient temperature between 13 and 17 °C, fluctuating heating can better avoid local overheating and ensure thermal acceptance rate larger than 90%, and fluctuating heating with high frequency and small amplitude is better than that with low frequency and large amplitude. Thus, the optimal fluctuating foot heating mode was recommended to be applied in cold environments higher than 13 °C.

Impact of body fat and fitness on human thermal responses under transient neutral-cool indoor conditions

Impact of body fat and fitness on human thermal responses under transient neutral-cool indoor conditions

Human thermal physiological response of wearing personal protective equipment: An educational building semi-open space experimental investigation

With the outbreak and spread of the COVID-19 epidemic, HCWs are frequently required to wear personal protective equipment (PPE) for nucleic acid sample collection in semi-open transition spaces. Wearing PPE causes significant psychological and physical stress in HCWs. In this study, operative temperature (Top) and wet-bulb globe temperature (WBGT) were used to assess thermal conditions through field experiments, while multiple physiological parameters were measured in the subjects. The results indicated that the subjects showed statistically significant differences in thermal perception and physiological parameters with and without PPE. Using observed increases in heart rate (HR), auditory canal temperature (Tac), mean skin temperature (MST), and end-tidal CO2 pressure, subjects were shown to have an increased metabolic rate and heat storage while wearing PPE. Additionally, a decrease in oxygen concentration was also observed, and this decrease may be linked to fatigue and cognitive impairment. Moreover, HR, MST, and Tac showed a significant linear relationship, which increased with temperature and operative temperature, and the HR response was stronger with PPE than without PPE. The neutral, preferred, and acceptable temperatures were significantly lower with PPE than without PPE, and the deviations for neutral Top/WBGT were 9.5/7.1 °C and preferred Top/WBGT was 2.2/4.0 °C, respectively. Moreover, the upper limits of acceptable WBGT, 29.4 °C with PPE and 20.4 °C without PPE, differed significantly between the two phases. Furthermore, the recorded physiological parameter responses and thermal perception responses of the subjects while wearing PPE indicated that they were at risk of thermal stress. Overall, these results suggest that people who wear PPE should focus on their health and thermal stress. This study provides a reference for the development of strategies to counteract heat stress and improve thermal comfort.

Effect of time-of-day on human dynamic thermal perception

Implementing heating and cooling set-point temperature modulations in buildings can promote energy savings and boost energy flexibility. However, time and time-of-day requirements in current indoor climate regulations are either overly simplified or ignored completely. A better understanding of how human thermal responses vary throughout the day is useful to effectively design and operate energy-flexible buildings. To date, only a handful of studies have looked at diurnal changes in thermal perception and mostly near steady-state neutrality without controlling for light exposure. This is the first experimental investigation aimed at understanding how the time of the day influences physiological and subjective human sensory responses to a localized dynamic thermal stimulus under constant light rich in long wavelengths (red). Results indicated that humans responded physiologically differently depending on the time of the day with a higher rate of change in the skin temperature in the evening compared with the afternoon. Furthermore, the increase of thermal sensation during the warming skin temperature transients was found to be greater in the evening. No differences were observed under steady-state thermal conditions. This evidence suggests that accounting for the time of the day is important when dynamically operating buildings, such as during demand-response programs.

Design Of virtual binaural manikins and auditorium acoustic system

In this work a numerical model is applied in the development of the design of virtual binaural manikins and auditorium acoustic system. The binaural acoustic manikins is based in human body methodology and is developed using empirical and geometrical equation numerical model also coupled with the CAD system. The auditorium geometry is based in a conic methodology and is developed using a geometric numerical model coupled with a CAD system. The binaural manikin geometry, using the Human Thermal Response and the Sound Propagation numerical models, is used in the human acoustic evaluation. The virtual binaural manikin evaluates the direct and indirect sound and calculates the reverberation time. In this preliminary study an auditorium with a group of rows and columns, occupied with 140 virtual manikins, is developed. Three virtual binaural manikins was selected to be evaluate the reverberation time. The acoustic level, in the left and right ears, that the virtual manikins are subjected are evaluated. In accordance the obtained results, the manikins acoustic level evolution, with the reverberation time in accordance with the international standards, presents slight differences between left and right ear and differences between the different binaural manikins.