Journal of Thermal Biology 49-50 (2015) 1–8

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Journal of Thermal Biology journal homepage: www.elsevier.com/locate/jtherbio

Thermal responses and perceptions under distinct ambient temperature and wind conditions Yasuhiro Shimazaki a,n, Atsumasa Yoshida b, Takanori Yamamoto c a

Department of Systems Engineering for Sports, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197, Japan Department of Mechanical Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan c Product Reliability and Human Life Science Section, Technology Research Institute of Osaka Prefecture, 2-7-1 Ayumino, Izumi, Osaka 594-1157, Japan b

art ic l e i nf o

a b s t r a c t

Article history: Received 23 July 2014 Received in revised form 24 January 2015 Accepted 26 January 2015 Available online 28 January 2015

Wind conditions are widely recognized to influence the thermal states of humans. In this study, we investigated the relationship between wind conditions and thermal perception and energy balance in humans. The study participants were exposed for 20 min to 3 distinct ambient temperatures, wind speeds, and wind angles. During the exposure, the skin temperatures as a physiological reaction and mental reactions of the human body were measured and the energy balance was calculated based on the human thermal-load method. The results indicate that the human thermal load is an accurate indicator of human thermal states under all wind conditions. Furthermore, wind speed and direction by themselves do not account for the human thermal experience. Because of the thermoregulation that occurs to prevent heat loss and protect the core of the body, a low skin temperature was maintained and regional differences in skin temperature were detected under cool ambient conditions. Thus, the human thermal load, which represents physiological parameters such as skin-temperature change, adequately describes the mixed sensation of the human thermal experience. & 2015 Elsevier Ltd. All rights reserved.

Keywords: Thermal sensation Thermal comfort Human energy balance Air current Regional skin temperature Ambient temperature

1. Introduction The use of wind in environmental design has attracted increasing interest recently. Urban ventilation corridors are considered to function as one of the countermeasures against urban heat pollution (Wong et al., 2010). Conversely, urban shapes such as buildings and trees occasionally create strong local winds (Eliasson, 2000), and such winds can cause pedestrian discomfort (Reiter, 2010). Tuller (1997) reported that cool onshore winds strongly affect the creation of cool thermal sensations. In this regard, when planning environmental designs, it is critical to consider not only physical weather variables but also the human thermal experience of environment factors such as the wind. Studies on human thermal perception have been performed for several years, and human thermal states have been determined to be influenced by wind speeds and also by physical environmental variables and additional human variables such as temperature, humidity, radiation, and human metabolism and clothing. Nikolopoulou and Steemers (2003) investigated the perception of thermal comfort by using a questionnaire on wind and sunshine perception. Givoni et al. (2003) performed studies on human n

Corresponding author. E-mail address: [email protected] (Y. Shimazaki).

http://dx.doi.org/10.1016/j.jtherbio.2015.01.005 0306-4565/& 2015 Elsevier Ltd. All rights reserved.

participants and showed that in terms of outdoor climate assessment, a change of 1 °C in air temperature was equivalent to a change of 0.35 m/s in wind speed. Most thermal indices were developed based on steady-state human energy-balance models, and one of the most widely recognized models that contains the major variables mentioned in the preceding paragraph was developed by Gagge et al. (1970), which is known as the 2-Node Model. “Physiologically Equivalent Temperature” (Matzarakis et al., 1999), “Universal Thermal Climate Index” (Jendritzky et al., 2012), and other indices were subsequently proposed to extend the application range of the models to outdoor environments. Researchers have also attempted to extend the energy-balance model named the “human thermal load” model to the outdoor environment (Shimazaki et al., 2011). Because various meteorological variables have different levels of importance depending on the weather situation (Höppe, 1999), these energy-balance models might be inadequate for use in evaluating human thermal perception under extreme weather conditions. Moreover, because of the risk for cold stress and cold injuries, air movement could strongly influence the human thermal state in cold environments: people typically consider the temperature to be lower than it truly is when cool winds are blowing, and people might be sensitive to the wind in cold environments. In cool or cold environments, even a light breeze might be perceived as a draft, which can be a source of discomfort.

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The widely recognized wind-chill index is calculated using air temperatures and the facing wind speeds (Siple and Passel, 1945). In previous studies, the human thermal-load index was validated under environmental conditions in which temperature, humidity, and radiation levels were changing; however, wind condition is a factor whose effect remains to be validated. Most people agree that air movements positively affect sensible heat loss and even latent heat loss. However, few studies have addressed the extent to which air movement can affect human thermal perception. Thus, in this study, our goal was to determine how wind influences human energy balance and thermal perception under various conditions. Our second goal was to develop a fundamental database that can be used for optimizing thermal perception when designing living environments.

2. Materials and methods Almost all commonly used thermal-comfort indices are developed based on studies conducted on human participants. Thus, we conducted experiments in which we measured the physiological and mental reactions of the human body to environmental conditions. In these experiments, study participants spent 20 min inside an artificial climate chamber (dimensions: 7.1  5.0  4.0 m3; Fig. 1) at the Research Institute of Osaka Prefecture. In this study, we enrolled 36 healthy males, aged 22–24 years; the participants' mean age was 22.7 years (SD 0.5 year), their mean height was 173.3 cm (SD 2.5 cm), and their mean weight was 64.7 kg (SD 1.9 kg). All participants provided informed consent and agreed to be a part of the study, and the research was conducted with the approval of the Research Ethics Committee of Okayama Prefectural University. We tested the effects of 3 distinct ambient temperatures, wind speeds, and wind directions. First, the neutral ambient temperature was determined to be 26 °C based on the preliminary declaration of the participants before the experiments. Next, 16 and 36 °C were set as the cool and warm ambient temperatures, respectively. The pretest room temperature was maintained constant at approximately 20 °C. In the test environment, we set calm, moderate, and high wind speeds as approximately 0, 2, and 5 m/s, respectively. The wind directions were set as 0°, 45°, and 90° under the cool ambient temperature and high-wind condition. The wind direction was set as 0° when the wind faced the front of the participant and the direction was defined in degrees of clockwise rotation. Participants were positioned facing upwind at the center of the chamber (Fig. 1). The relative humidity was set as 50% for the entire experiment. The surfaces of the chamber were controlled and equivalent to the air temperature, and thus the mean radiant temperature was always equivalent to air temperature. Before experiments, the wind profile was measured. The wind

Fig. 1. Experimental chamber.

fan placed in front of the participants was 2.0  2.0 m2 in size, and this was adequately larger than the participants. The wind velocity was measured in 1.0-min intervals in 4 horizontal directions and in 0.4-min intervals in the vertical (height) direction. Next, the turbulence intensity was calculated in terms of airflow characteristics; this intensity provides information on the average magnitude of the velocity fluctuation over a period in relation to the mean velocity. The maximal turbulence intensity of the chamber was 0.57 at the maximal wind speed of 5.0 m/s. A previous field measurement showed that the turbulence intensity in the street is approximately in this range (Longley et al., 2004). The surrounding weather factors and the physiological response of the human body were measured in order to evaluate human thermal states. Global solar radiation, reflected solar radiation from the ground, infrared radiation from the atmosphere and the ground (EKO MR-60), air temperature (Pt-100 resistance), wind speed (ultrasonic anemometer), humidity (capacitance hygrometer), ground temperature (thermocouple), and wall temperatures (thermocouple) were measured in 20-s intervals. Once every 2 min, the study participants were asked whether they experienced any thermal sensation, and if they did, whether the experience was comfortable or if it caused discomfort; the participants recorded their answers on a fixed report in which an ASHRAE 7-point scale was used (Schiller et al., 1988). The ASHRAE 7-point scale is the psychophysical scale of warmth (ASHRAE, 2010). The subjects' lined declarations were scored from 3 (cold) to 3 (hot) for thermal sensation with linear interpolation. Similarly, thermal comfort is 5-point scale from 2 (uncomfortable) to 2 (comfortable). The subjective questionnaires are shown in Fig. 2. Sensors (thermistors) were installed sublingually at 7 points on the skin (forehead, upper arm, hand, pelvis, thigh, leg, and foot) 15 min before the measurements began, by which point the participants were acclimated to the initial environmental state in the chamber. All measurements were performed during a single session, and only one subject took part in the experiment at each time. The clothing insulation was 0.30 clo throughout the experiment for the prevention of clothing effects.

3. Results 3.1. Skin temperatures Skin temperatures strongly affect heat transfer between humans and their surroundings. Thus, to evaluate human energy balance, we analyzed the effect of wind on skin temperatures under 3 ambient temperatures. The data were obtained with the use of statistical analysis. The data are normally presented as the mean response, and standard deviations are also presented in figures to show individual differences. The multiple comparisons among conditions were based on the Tukey–Kramer method. First, we measured the time-dependent change in mean skin temperatures under distinct ambient temperatures with calm wind at an angle of 0° (Fig. 3). The mean skin temperatures, which were calculated according to the formula presented by Hardy and DuBois (1937), were almost constant throughout the experiment and a thermal steady state was reached. However, these

Fig. 2. Subjective questionnaires.

Y. Shimazaki et al. / Journal of Thermal Biology 49-50 (2015) 1–8

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a

Fig. 3. Temporal changes in mean skin temperature under various ambient temperatures.

temperatures were substantially different under the distinct conditions tested. Because the mean skin temperature was stable, we calculated their time-averaged values, which were 28.5 °C in cool ambient temperature, 31.1 °C in neutral ambient temperature, and 35.4 °C in warm ambient temperature. Thus, the mean skin temperature increased when the ambient temperature was raised. The time-averaged skin-temperature distributions obtained at distinct wind speeds are shown in Fig. 4(a)–(c). The results of multiple comparisons are shown in Table 1. The results showed that temperature differences among conditions were statistically significant. In warm ambient temperature, the regional skin temperature differences were small across the entire body. Regional skin-temperature differences tended to increase when the ambient temperature was lowered. In cool ambient temperature, the distal regional temperatures, such as those of the hand and foot, decreased clearly, and the pelvis temperature was the highest. The variations in distal regional temperatures are relatively larger, and this might occur according to individual variation of body temperature regulation. The maximal difference in temperature was between the pelvis and the foot, and this was 7.3 °C under conditions of calm wind and cool ambient temperature. In cool ambient temperature, the maximal skin-temperature difference was 8.3 °C under medium wind and 6.1 °C under high wind conditions. The maximal skin-temperature difference ranged from 3.8 to 5.0 °C in neutral ambient temperature and from 1.5 to 3.3 °C in warm ambient temperature. When the wind speed was increased, the skin temperatures decreased over the entire whole body. Next, the time-averaged skin-temperature distributions were measured under cool ambient conditions in which distinct wind directions and the high wind speed were used (Fig. 5). The results of multiple comparisons are shown in Table 2, which showed the temperature differences among conditions to be statistically significant. The skin-temperature distributions showed the same tendency when the 3 wind directions were tested. Hand and foot temperatures were low, whereas upper-arm, pelvis, and leg temperatures were high. By contrast, each wind direction affected the skin temperature to distinct extents. For example, the minimal mean skin temperature was obtained with 0° wind. The timeaveraged mean skin temperature was 26.1 °C in 0° wind, 28.8 °C in 45° wind, and 28.5 °C in 90° wind. The maximal skin-temperature difference was 6.7 °C in 45° wind and 7.9 °C in 90° wind. 3.2. Thermal perceptions Because the subjective thermal perceptions of humans are critical for adaptation and for developing human-centered design concepts, the effect of wind on thermal sensation and thermal comfort were analyzed under 3 ambient temperatures. The time-dependent thermal-sensation vote and thermalcomfort vote obtained under conditions of high wind and cool

b

c

Fig. 4. Skin-temperature distributions under distinct wind speeds and (a) cool, (b) neutral, and (c) warm ambient temperatures.

ambient temperature are shown in Fig. 6. The preceding skintemperature results suggested that wind has a strong effect when cool ambient temperature and high wind conditions are used. However, thermal sensation and thermal comfort remained almost constant and a thermal perceptual steady state was reached. The time-averaged thermal-sensation vote and thermal-comfort vote were approximately 1.7 and 1.1, respectively. The time-averaged thermal-sensation vote and thermal-comfort vote obtained under distinct ambient temperatures at the 3 wind speeds are shown in Fig. 7(a). Thermal-sensation and -comfort levels depend on the ambient temperature. Thermal sensation and thermal comfort were almost equal when measured at the same ambient temperature. The thermal-sensation vote was around 1.7, 0.1, and 0.9 in cool, neutral, and ambient temperatures, respectively, and the thermal-comfort vote was approximately 1.0, 0.8, and 0.2 in cool, neutral, and ambient temperatures, respectively. The relationship between thermal sensation and thermal comfort is shown in Fig. 7(b). Humans are

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Table 1 Multiple significant-difference chart under distinct wind speeds. Cool

Forehead Upper arm Hand Pelvis Thigh Leg Foot

Calm Neutral Calm Neutral Calm Neutral Calm Neutral Calm Neutral Calm Neutral Calm Neutral

Neutral

Warm

Neutral

High

Neutral

High

Neutral

High

nn

nn

nn

nn

nn

nn



nn

nn

nn

nn

nn



nn

n



nn

nn



nn



nn

– NS –

nn

nn

nn

nn

nn



nn



nn

nn

nn

– NS –

nn nn nn

nn

nn nn



nn

nn nn



nn



nn



nn nn nn

nn

nn

nn

nn

– NS –

NS

nn nn



nn

nn

nn

nn

nn

nn

nn

nn

nn

nn



nn



nn



nn

Fig. 6. Time-dependent changes of thermal-sensation vote and thermal-comfort vote.

NS: not significant.

high wind conditions are shown in Fig. 7(c). All thermal-sensation votes were approximately 2.2, and all thermal-comfort votes were approximately 1.4. All of these values are almost equal and thus a clear-cut effect of wind direction on thermal sensation and thermal comfort was not detected.

nn n

1% probability. 5% probability.

3.3. Energy balance

Fig. 5. Skin temperature distributions measured at distinct wind angles.

Table 2 Multiple significant-difference chart under distinct wind angles. Cool 45° Forehead Upper arm Hand Pelvis Thigh Leg Foot

0° 45° 0° 45° 0° 45° 0° 45° 0° 45° 0° 45° 0° 45°

90°

nn

nn



nn

nn

nn



NS

nn

nn



nn

nn

nn



nn

nn

nn



nn

nn

nn



nn

nn

nn



nn

NS: not significant. n 5% probability. nn

1% probability.

thermally comfortable when thermal sensations are nearly neutral, whereas they feel discomfort when the sensations are too warm or too cool. The effects of wind direction on time-averaged thermal sensation and thermal comfort under cool ambient temperature and

Human energy balance is considered to be closely associated with human thermal states; thus, we assessed the “human thermal load”, as proposed previously for outdoor environments (Shimazaki et al., 2011), under all experimental conditions as an objective measurement of thermal states. Human thermal-load measurements were obtained in order to examine the details of the effect of heat transfer near the human body, and these were analyzed by dividing them into measurements of metabolism, latent heat, sensible heat, and net radiation. Sensible heat and latent heat were estimated based on ASHRAE's method and on the convective heat-transfer coefficient value proposed by Yang et al. (2004). The convective heat-transfer coefficient was constant regardless of wind direction. The workload was neglected because participants only had to stand in place during the experiments, and the metabolism was set at a constant value of 80 W/m2 on the basis of the physical-activity level determined for standing (Ainsworth et al., 2011). Net radiation is the difference between the incoming and outgoing radiation. The amount of net radiation, net radiation, was computed for a simulated human body model in a rectangular parallelepiped (0.4 m  0.2 m  1.2 m). The amount of net radiation is the summation of the solar radiation and infrared radiation. The human thermal load is in itself the heat flux in a given condition and is calculated from Eq. (1) as the remaining amount of each item of energy balance

Q = M –W + R net –E –C

(1)

where M quantifies the metabolism, W is the workload, Rnet is the net radiation, E is the latent heat loss, and C is the sensible heat loss. All units are in W/m2. The time-averaged total thermal load is shown in Fig. 8; the wind direction was 0°. The total thermal loads, which depended on the ambient temperature, were nearly equal when measured under the same ambient temperatures; they were approximately 110, 30, and 40 W/m2 in cool, neutral, and warm ambient temperatures, respectively. The clearest difference in the human thermal load was in sensible heat: the amount of sensible heat ranged from 80 to 110 W/m2 in cool ambient temperature and from 40 to 55 W/m2 in neutral ambient temperature, but it

Y. Shimazaki et al. / Journal of Thermal Biology 49-50 (2015) 1–8

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a

Fig. 8. Total thermal loads under various conditions.

a b

b

c

Fig. 9. Relationships among wind speed, thermal sensation, and human thermal load. (a) Wind speed and thermal sensation. (b) Wind speed and human thermal load.

Fig. 7. Thermal sensation and thermal comfort. (a) Values measured under distinct ambient temperatures and wind speeds. (b) The overall relationship between thermal sensation and comfort. (c) Values measured at distinct wind angles.

exhibited almost no difference in warm ambient temperature. Net radiation difference had the second largest impact on human thermal load. The net radiation values were approximately 60, 40, and 10 W/m2 in cool, neutral, and warm ambient temperatures, respectively. Moreover, in cool and neutral ambient temperatures, the total thermal load was slightly larger under the calm wind condition than under the moderate and high wind conditions.

The relationships among the total thermal load, wind speed, and thermal sensation under distinct ambient temperatures are shown in Fig. 9(a) and (b). Thermal sensations varied even when the same wind speed or ambient temperature was used, and thus a relationship between thermal sensation and wind speed could not be readily detected. By contrast, the total thermal load was correlated with wind speed under each ambient temperature. In the regression lines shown in this figure, the slope of the line for cool ambient temperature is negative, and the slope increased when the ambient temperature was raised; the regression line for the warm ambient temperature has almost no slope. The human thermal load tended to decrease when the wind speed was increased, and wind speed had the largest impact on the thermal load under the cool ambient temperature. Next, we measured the effect of wind direction on human thermal load under the cool ambient temperature; the time-averaged

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Fig. 10. Human thermal loads obtained at distinct wind angles.

values of the thermal load are shown in Fig. 10. The total thermal loads measured in 45° and 90° wind were smaller than that in 0° wind, with the value being the smallest in 45° wind. The difference in total thermal loads appeared in sensible heat and net radiation. Sensible heat was approximately 120 W/m2 and net radiation was approximately 70 W/m2 in 45° and 90° wind. By contrast, sensible heat was around 100 W/m2 and net radiation was around 50 W/m2 in 0° wind. 3.4. Human thermal load and thermal sensation Because objectively measured thermal conditions and subjective thermal states are interconnected, we analyzed the relationship between human thermal load and thermal sensation, and our results revealed a linear relationship between them (Fig. 11). The coefficient of the correlation between human thermal load and thermal sensation was as high as 0.93. This result indicates that the participants unconsciously judged their thermal sensation based on the degree of heat that they experienced. Moreover, the aforementioned total thermal load values could be used to effectively predict human thermal states: whereas human thermal perception was not affected solely by wind, it was affected by human thermal load. Thus, our results demonstrate that human thermal load can be used as an accurate index for assessing human thermal environments.

4. Discussion Wind is characterized in terms of wind speed and direction. However, wind speed and direction by themselves do not explain the human thermal experience. The combination of four physical environmental variables and additional human variables—such as

Thermal sensation

3

Cold Neutral Hot

2 1 0 -1 -2 -3

-200 -100 0 100 200 Human thermal load (W/m2)

Fig. 11. Relationship between human thermal load and thermal sensation.

wind speed, temperature, humidity, and radiation, and metabolism and clothing—can account for the human thermal experiences. This study has shown that human energy balance or human thermal load is an accurate indicator of human thermal states regardless of the prevailing wind condition. This is because human thermal load totally includes influential environment and human variables that affect the human thermal state. Furthermore, the human thermal load is quantitatively expressed by dividing the energy flow around the human and thermal components. Because calculating the human thermal load is not very complicated and the detailed energy flow values can be obtained without special computational skills, this is useful for improvement and future planning. Metabolism and latent heat loss were almost the same under all experimental conditions, and the difference in total thermal load was apparent in sensible heat and net radiation. Heat-transfer amounts depend on temperature differences, and sensible heat is proportional to the difference between skin and ambient temperatures. The basic physical process that relates wind to human thermal states or sensible heat is convective heat transfer, which depends on the difference between human and ambient temperatures. Moreover, because fluid flow induces convective heat transfer, wind speed is a key variable, and high wind speeds induce convective heat transfer. Wind direction can also strongly influence the convective heat-transfer coefficient (de Dear et al., 1997). In this study, radiative heat transfer mainly occurred through long-wavelength radiation because the experiment was conducted indoors. According to the Stefan-Boltzmann Law, longwavelength radiative transfer is proportional—in the fourth power —to the difference between skin and ambient temperatures. Thus, heat release tends to depend on ambient temperatures, and this explains why ambient temperatures create the baselines of the human thermal state. Total thermal loads were roughly equal when the ambient temperatures were the same (the loads were approximately 110, 30, and 40 W/m2 in cool, neutral, and warm ambient temperatures, respectively). Because the amount of sensible heat loss was larger than the amount of net radiation heat loss under cool and neutral ambient temperatures (Fig. 8), the impact of sensible heat on human thermal load was greater than that of net radiation. The amounts of sensible heat and net radiation were approximately 100 and 60 W/m2 in the cool ambient temperature, respectively, whereas the amount of sensible heat was roughly 50 W/m2 and the amount of net radiation was around 40 W/m2 in the neutral ambient temperature. Under the warm ambient temperature, the difference between skin and ambient temperatures was small, and thus sensible heat and net radiation exerted a limited effect on the thermal state of the whole body. The convective heat-transfer coefficient tends to become smaller when the angle of the wind direction in increased within the experimental wind angles used in this study (Clark and Toy, 1975). If this occurs, then when the ambient temperature is the same, the lowest values of both human thermal load and thermal sensation might be measured under a condition of high wind or 0° wind. However, these values were not always the lowest in our study, which indicates that human thermal states were not affected by wind conditions alone. This is because skin temperatures typically change to maintain a constant human thermal state and core temperature. The skin temperature provides an afferent input to the thermoregulation system in order to adjust to various environmental conditions, and concurrently, the skin temperature is a key output that continually influences heat transfer near the human body. High-speed wind or 0° wind might affect humans most strongly. The effect of wind was detected in skin temperatures: the mean skin temperatures decreased when the ambient temperature was lowered, and when the wind strength was

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increased, skin temperatures again decreased. The regional temperature differences tended to increase when the ambient temperature was decreased. The maximal difference in regional temperature was 8.3 °C under the conditions of cool ambient temperature and high wind. Because of thermoregulation, the skin temperature was maintained low and this prevented heat loss, and regional skin temperature differences occurred in the cool environment. Thus, high-speed wind by itself does not increase heat loss. In the warm environment, in which the temperature was approximately the skin temperature, the convective heat transfer was limited (Fig. 8) and whole body thermoregulation had the advantage. Each skin temperature may be regulated by considering the whole body energy balance in this case. Wind conditions such as wind speed and direction are key thermal environmental variables. The physical environment strongly affects outdoor thermal comfort, but the human physiological response is also a crucial factor. Humans exhibit the inherent ability to maintain thermal constancy, and humans use diverse means to fully adjust the variables related to their state of being even under severe environmental conditions, such as when strong cold winds are blowing. Distal region such as the hand and foot, in particular, were affected by not only the wind condition but also thermoregulation. For example, skin temperatures in distal regions decrease to maintain the temperature in the core and trunk region in cool ambient temperature. Our results revealed that the temperatures on hand and foot were lower than in other regions, as shown in Fig. 4(a). Given the effect of human aspects on human thermal states, measuring skin temperatures is essential for understanding the heat transfer on human surface; furthermore, assessing the metabolism is critical for determining inner heat generation. Consequently, human thermal load, which represents physiological parameters such as skin-temperature change, can accurately describe the mixed sensation of human thermal experiences.

5. Conclusions In order to determine how wind affects human energy balance and thermal perception under various conditions, the participants of this study were exposed for 20 min to 3 distinct ambient temperatures, wind speeds, and wind angles. During the exposure, we measured skin temperatures as a physiological reaction and mental reactions of the human body and then calculated the energy balance. Our results indicated that a clear relationship does not exist between wind speed and human thermal perception. By contrast, human thermal load and thermal sensation were closely correlated. Therefore, human energy balance or human thermal load can serve as an accurate indicator of human thermal states regardless of the wind condition. The physical process through which wind affects human thermal states is convective heat transfer, and thus the difference between human and ambient temperatures and wind speeds are key variables: ambient temperatures create the baselines of the human thermal state, whereas wind conditions incrementally affect humans. However, wind by itself is not the cause of human thermal perception. Both ambient temperatures and wind conditions must be considered, and, consequently, the synthesizing index of human thermal load containing four physical environmental variables and additional human variables such as wind speeds, temperature, humidity, radiation, and metabolism and clothing is an optimal index for describing human thermal states. Moreover, human thermal loads can represent physiological parameters such as skin-temperature change and accurately describe the human thermal experience.

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Dr. Yasuhiro Shimazaki is an assistant professor who is researching and teaching human thermal environmental systems at Okayama Prefectural University Japan. His principal research interests lie in the field of the human living environment. He is currently investigating human thermal comfort or human-biometeorology under transient and non-uniform complex conditions and the effect of the thermal properties of urban components such as surface materials and even clothing on heat transfer between humans and the environment by performing field measurements and numerical simulations.

Dr. Atsumasa Yoshida is a professor who is researching and teaching mechanical engineering at Osaka Prefecture University Japan. His principal research interests lie in the field of environmental heat transfer. He is currently investigating heat and mass transfer problems particularly heat island phenomena, from viewpoints of environmental, thermal, and hydraulic engineering. The effect of outdoor environment on human thermal sensation, including physiological topics such as sweat, has been evaluated. The measurement technique and the diagnosis technology have been developed on the radiative properties of various materials and the thermal properties of the human body and practical use apparatus.

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Dr. Takanori Yamamoto is a senior researcher at Technology Research Institute of Osaka Prefecture Japan. He belongs to the Product Reliability & Human Life Science Section. His research field is textile engineering and sensory measurement engineering. He is working on the performance evaluation test for the reliability of human life product.

Thermal responses and perceptions under distinct ambient temperature and wind conditions.

Wind conditions are widely recognized to influence the thermal states of humans. In this study, we investigated the relationship between wind conditio...
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