Body heat balance involving effect of behavioral thermoregulation toward creating sensational and physiological climate design
To create healthy and comfortable living spaces for people, and improve current living environments, it is essential to accurately understand, through their physiological and psychological responses, the effects of thermal environment in the context of thermoregulation - a fundamental life-sustaining mechanism in humans. A series of research has begun with the objective of learning about the effect of these thermal environments on human beings, and applying the results in creating and improving living environments. This research is about living environment evaluation and sensational and physiological climate design conditions, based on human physiological and psychological findings.
Therefore, the main research defines the human factor that constitutes body heat balance, while focusing on the characteristics of the human body and posture, from the point of view of behavioral thermoregulation, which has culture and climate in the background. In addition to this, based on the body heat balance formula, heat conduction conditions and heat transfer area are incorporated, to newly develop ETF, an indoor thermal environmental evaluation index that involves the 5 conditions of air velocity, temperature, thermal radiation, humidity and heat conduction, and ETFe, an outdoor thermal environmental evaluation index that involves the 6 conditions of air temperature, air velocity, long wavelength thermal radiation, heat conduction, humidity and the amount of short wavelength solar radiation. Through experiments on subjects, their effectiveness as sensational and physiological temperature indices that can additionally express their respective effects has been clarified, and a comfortable thermal environment range for living spaces has been proposed. By adding the perspective of posture to thermal environment evaluation, the thermal environments of living spaces can be expressed more realistically. Also, based on this basic research on indoor spaces, research on outdoor spaces is being developed.
The main research in this series is divided into 12 domains. They mainly involve expansion towards the scientific description of the following areas - concepts related to thermal equilibrium formula in the human body, study on body surface area calculation formula, study of metabolic energy, measurement of the thermal factor of the human body in the context of convective heat exchange, measurement of the thermal factor of the human body in the context of radiative heat exchange, measurement of the thermal factor of the human body in the context of conductive heat exchange, study related to the calculation of mean skin temperature, study on the thermal factor of clothing, development of the thermal environment evaluation indicators, consideration of the effect of thermal environment on physiological and psychological responses in humans, application to a comfortable thermal environment for the human body, analysis of human response, and human body and thermal environment.
In the planning and design of thermal environment, sensational and physiological temperature has been used as the basic theory of control of air conditioning equipment. However, conventional sensational and physiological temperature has remained limited to mainly incorporating the thermal environment evaluation method for office spaces. Here the results of research on laboratory spaces targeting light work primarily in a chair-sitting posture have been used as the basis. However, since living spaces offer more freedom for activity compared to laboratory spaces, behavioral thermoregulation has been carried out to adjust the thermal environment by working on the environment. Various postures that have a close relationship with the floor are used in living spaces, and the differences in these postures have a strong influence on human factors contributing to the body heat balance in humans. Moreover, body composition and physique are prone to change due to a variety of factors such as culture and diet, so research targeting the human body needs to be carried out continuously.
Sensational and physiological temperature represents the heat balance between the human body and its surrounding environment, but it is necessary to identify the various factors related to the human body in order to calculate body heat balance. Conventionally, the planning, design, evaluation and control of the thermal environment was based solely on human body factors, in a scope that was limited to the two extreme conditions of the standing position and the chair sitting position. In the main research here, I propose separate human body factors depending on basic postures used in living spaces. I have proposed and are studying the human body surface area formula, convective heat transfer area of the human body, human convective heat transfer coefficient, mean skin temperature calculation formula with the consideration of convective heat transfer area, radiative heat transfer area of the human body, angle factor of the human body, human radiative heat transfer coefficient, convective heat transfer area of the human body, mean skin temperature calculation formula with the consideration of heat conduction, metabolic rate based on the chair-sitting position of humans, effective surface area factor of clothing, and thermal insulation of clothing, according to the aforementioned postures. Until now, minute differences in posture were considered negligible, but now it is clear that it is necessary to calculate heat balance by taking into consideration the differences in posture. Therefore, I have developed a new sensational and physiological temperature index that shows a specific value in the setting for thermal environmental conditions targeting the various postures used in living spaces. This is the world’s first proposal of a mean skin temperature calculation formula that is correct from the heat transfer point of view and focuses on heat transfer area and human convective heat transfer area, and an outdoor thermal environment evaluation index that incorporates the effect of heat conduction and short wavelength solar radiation.
Furthermore, I have conducted a quantitative study of the influence of behavioral thermoregulation and environmental regulation methods on sensational and physiological climate formation, using human data based on factors influencing the climate formation in living spaces, such as the climate of the region, and specific values and calculation formulas proposed in this research; and have proposed the fundamental findings for making a thermal environment plan. By quantitatively evaluating posture and heat conduction, I propose a floor cooling environment with an air-conditioner that actively uses heat conduction. I would also like to indicate that the use of active heat conduction or thermal radiation, which is in line with culture and living conditions, is useful for energy conservation. In addition, by using previous human body data, I develop an evaluation index from heat balance analysis of outdoor environments, and study the effectiveness of the index; I then propose a comfortable range, and I have also touched upon environmental withdrawal behavior.
As given above, the emphasis of this research is on explaining thermal environment in living spaces, and I have taken efforts to adapt the thermal environment evaluation methods that were mainly for office spaces earlier, to make them suitable for living spaces. The proposal for specific values or calculation formulas for the thermal factor in human beings, and the development of sensational and physiological climate indices are large results that are contributing significantly to the creation and improvement of living environments.
Chapter 1 describes research on thermal equilibrium of the human body that technologically clarifies the evolution of the research on thermal equilibrium between the human body and the environment, and the factors related to the human body that are its main causes on the human-body side, and describes its issues and considerations. One can see the necessity of identifying the various factors (numerical values) related to the human body, in order to calculate thermal equilibrium between the human body and the environment. In living environments in indoor spaces, posture and posture changes in the context of behavioral thermoregulation pose significant problems in planning thermal environments. I point out the problem of human body factors, with a focus on calculation formula for the amount of heat exchange (paper No.1). Therefore, based on accumulated posture-wise human factors, I have pointed out significant differences in the human body factor of the standing position or the chair-sitting position generally used in research related to heat balance or thermal environment indices, and other postures such as the floor-sitting position and lying position. Actual spaces are heterogeneous and not homogenous, so significant temperature differences can be observed on comparing surface temperatures or air temperatures near the floor with other surfaces comprising the inside the room. Conduction and radiation from the floor have stronger effects on the floor sitting or lying position compared to the standing position or chair-sitting position, so it is clear that it is necessary to calculate heat balance for Japanese people after taking into consideration differences in posture (paper No.2).
Chapter 2 describes research on body surface area, and deals with the proposal and verification of a formula for the calculation of the body surface area of Japanese people. Research on the body surface area of the human body began in the second half of the 19th century, and a lot of research and surveys have been done to derive a calculation formula for body surface area. DuBois’ calculation formula for human body surface area of the year 1916 is used widely overseas. In Japan, the calculation formula for the body surface area for age 6 and above given by Fujimoto and Watanabe, et al. in 1968 was widely used. However, it is absolutely essential to understand the current state, since the physique and body composition of the Japanese people would have changed significantly owing to changes in lifestyle and eating habits. I actually measured body surface areas in order to understand the current status of body surface areas of Japanese people. I have also proposed a calculation formula for body surface area that is most suitable for Japanese people (paper No.3). I am currently studying whether the proposed calculation formula for human body surface area would still be applicable 10 years later. I am verifying the effectiveness of the proposed calculation formula for human body surface area, by confirming its compatibility with actual measured values (paper No.4).
Chapter 3 describes research on metabolic rate, wherein the reference value of metabolic rate for predicting and evaluating in detail the thermal environment in Japanese living spaces is obtained from actual posture-wise measurements taken in the living space. Although a list of metabolic rates by work status is available, it does not show the metabolic rates in postures such as the floor sitting position that people use when relaxing at home. This shows the metabolic rates of Japanese people in postures such as the standing position, sitting position with legs underneath (seiza sitting position), cross-legged sitting position, sideway sitting position, both-knees-erect sitting position, leg-out sitting position and lateral position. I confirmed the effect of changing over from the chair-sitting posture to other postures, and it was clear that it is necessary to show posture-wise metabolic rates (paper No.5). The metabolic rate ratios of Japanese people in each posture based on the metabolic rate in the chair-sitting position were found, and it was seen that it was possible to calculate the metabolic rate for each posture used by Japanese people in living spaces, by determining the metabolic rate in the chair-sitting position (paper No.6).
Chapter 4 describes research on convective heat exchange, regarding the convective heat transfer area ratio and convective heat transfer coefficient. In the research on convective heat transfer area ratio, I clarified heat transfer area ratios related to human convection heat exchange, according to postures, by measuring the whole surface area (paper No.7). It was believed that the whole of the human body is open to air velocity, but it can be seen that the convective heat transfer area ratio is a value larger than the radiation heat transfer area ratio. I have proved that the convective heat transfer area ratio is an essential factor in the thermal equilibrium formula (paper No.8). It is the first time in the world that investigation by actual measurement of human convective heat transfer area ratio is being carried out. Next, in the research on convective heat transfer coefficient, I obtained the convective heat transfer coefficient of the whole human body through experiments, by focusing on human convective heat transfer area and wind direction, and proposed an experimental formula for convective heat transfer coefficient that incorporates the convection heat transfer area of the human body (paper No.9, 10). Then, in order to determine the heat transfer coefficient in case of forced convection of the human body that focuses on wind direction, site-wise heat transfer coefficients on the human body were clarified through actual measurements using the human body. I found it necessary to handle the data for each wind direction and each posture, and hence I propose experimental formula for convective heat transfer coefficient of the whole body including the heat transfer area of the human body and the radiant heat transfer coefficient, for each posture and each wind direction (paper No.11). Next, in office spaces, I focus on air-conditioning from the ceiling, and propose an experimental formula for convective heat transfer coefficient for the entire body, in the case of forced convection when the wind direction is downward from the top and the person is in the chair-sitting posture, through actual measurements using a thermal mannequin (paper No.12). To explain convective heat transfer coefficient of the human body in air-conditioning from the ceiling, I conducted experiments using a thermal mannequin. In the low wind speed range where the air velocity was 0.3m/s or less, it was clear that a difference was seen in the convective heat transfer coefficient of the human body, depending on air-conditioning temperature due to the effect of the buoyancy of natural convection, and I propose an experimental formula for heating and cooling that covers the whole scope from natural convection area to forced convection area (paper No.13).
Chapter 5 describes research on radiant heat exchange, regarding the treatment of thermal radiation, angle factor, radiant heat transfer coefficient and radiant heat transfer area ratio. In the research on radiant heat transfer area ratio, the focus is on the heat transfer area of the human body, which forms the basis of the amount of heat exchange between the human body and its surrounding environment. A significant influence of posture is clearly seen in the fact that the effective radiation area ratio of a posture in which the body bends and body surfaces come in contact, is smaller compared to that of a relatively open posture such as the standing position (paper No.14). In research related to radiant heat transfer coefficient, by throwing light on the differences in the heat transfer coefficient with differences in posture, it has been clarified that in addition to the mutual distance from or contact with the site surface, the influence of contact with the floor is prominently seen (paper No.15). In the research on the angle factor, experiments are being conducted from the point of view of quantitatively understanding thermal conduction from the floor. It is clear that the angle factor on a floor that is in close proximity with or makes contact with the human body largely differs depending on posture. It is also clear that the angle factor of the human body is largely influenced by the length along the wall opposite to the axis of the human body, or facing the size facing the wall opposite to the frontal coronal plane of the human body (paper No.16). Further, in the research on the handling of the amount of thermal radiation, the handling procedure of short wavelength solar radiation and long wavelength solar radiation has been shown, and the method of conversion to mean radiant temperature has been explained. The outdoor short wavelength effective thermal radiation field ERFhtaS, which shows the influence of the amount of solar radiation, and the effective humid field EHFETFe, which shows the influence of humidity, have been explained theoretically (paper No.17).
Chapter 6 describes research on conductive heat exchange, regarding the conduction heat transfer area ratio. In this research on conduction heat transfer area ratio, I have proposed a weighting factor that helps to calculate conduction heat transfer amount for each posture, and I are studying its effectiveness. Conventionally, the contact area between the floor and the human body was small, like in offices, and was considered negligible in the context of the whole surface area, and heat exchange to the contact surface was also believed to happen through radiation based on the law of solid angle projection. Therefore, I decided to take actual measurements of the contact site and the contact surface between the floor and the human body for each of the postures used in living spaces, for each of the sections of surface anatomy (paper No.18). Therefore, although it was difficult to quantitatively understand the heat transfer amount in postures excluding the standing position and the chair-sitting position, I have defined a weighting factor for calculating the conduction heat transfer amount, and it is now possible to quantify the conduction heat transfer amount with this weighting factor for calculating the conduction heat transfer amount (paper No.19). Also when evaluating thermal environment in research targeting office spaces, the effect of heat conduction on contact was ignored; but it is clear that when evaluating thermal environment in a posture where the contact surface area ratio between the human body and the floor exceeds approximately 2.5%, it is essential that the research includes the effect of heat conduction due to contact (paper No.20).
Chapter 7 describes research on mean skin temperature, wherein I have proposed a formula for calculating mean skin temperature for each accurate posture from the heat transfer point of view, and have explained the facts of this mean skin temperature. The conventional method for calculating mean skin temperature included non-heat-transfer surfaces as well, and hence the calculation of the heat transfer amount of the human body was not accurate. Differences were seen in site-wise heat transfer areas due to posture, and it was clear that in living environments where a variety of different postures are used, it is necessary to distinguish the calculation methods for mean skin temperature by posture. Hence, I have proposed a weighting factor for calculating the mean skin temperature for each posture, while taking heat transfer areas into consideration (paper No.21, 22). Unlike the conventional physiological ones, this is a theoretically correct factor that enables the determination of an accurate mean skin temperature from the point of view of heat transfer, and it is the first to be introduced to the world. Then, using these research results, it can be seen that it is possible to take environment regulation behavior such as posture also as an evaluation target (paper No.23). When compared with the whole surface area, it shows the characteristic that the smaller the convective heat transfer area, the bigger is its difference from the commonly used Hardy-DuBois mean skin temperature. By taking convection heat transfer area into consideration, it is clear that the influence of extreme skin temperatures can be expressed as mean skin temperature, even in the standing or chair-sitting positions (paper No.24). Also, the response of the human body was clear from actual measurements and experiments, but it is not possible to measure skin temperature by environment evaluation or prediction. Therefore, in order to predict the skin temperature of the human body in indoor spaces such as living rooms with plenty of sunshine or the perimeter zone of the office building, I have developed a thermoregulation model that incorporates thermal effects of heat conduction, short wavelength solar radiation and long wavelength radiation (paper No.25).
Chapter 8 describes research on clothing, regarding the thermal insulation of clothing and effective surface area factor of clothing. In the research on thermal insulation of clothing, the influence of posture on the thermal insulation of clothing has been explained. It is clear that thermal insulation of clothing differs due to posture, and it can be seen that conventional calculation methods and measurement methods for thermal insulation of clothing could not express the effects of posture. It is clear that it is essential to determine thermal insulation of clothing when designing and evaluating thermal environments, after investigating the clothing conditions taking into consideration posture differences (paper No.26). In research related to effective surface area factor of clothing, the influence of posture on effective surface area factor of clothing has been explained. It can be seen that changes in surface properties of clothing due to folding or overlapping, or change in the air layer of the space inside clothing show an influence, and differences in posture strongly appear in the effective surface area factor of clothing; it has been explained that the effect of posture on the calculation values could not be expressed in the conventional formula for effective surface area factor of clothing. It can be seen that in the conventional method of actual measurement of effective surface area factor of clothing, it was not possible to express the effects of posture on actual measurement values (paper No.26).
Chapter 9 describes research on the thermal environment evaluation index, wherein I have developed ETF, an indoor thermal environment evaluation index, and ETFe, an outdoor thermal environment evaluation index, with both indices taking into consideration behavioral thermoregulation. In order to evaluate living environments of postures such as the floor sitting position and lying position in Japanese living spaces from a sensational and physiological climate viewpoint, I have developed ETF, a new indoor thermal environment evaluation index wherein the effect of each of the 5 conditions of air temperature, air velocity, thermal radiation, humidity and heat conduction is independently converted to temperature, and added to be expressed as a formula (paper No.27). And I have developed ETFe, an outdoor thermal environment evaluation index to quantitatively explain the climate mitigation effect that improves the thermal environment in cities. ETFe involves the 6 conditions of air temperature, air velocity, long-wave thermal radiation, heat conduction and humidity. ETFe has been newly introduced, and is capable of evaluating outdoor thermal environments while taking into consideration differences in posture (paper No.28). I also conducted a study of the effectiveness of ETF as a thermal environment evaluation index, and that of the indices of elements that compose it, and its practical utility was clear from the results of the study (paper No.29). The total impact on the senses and the influence of individual meteorological elements were quantified on the same evaluation axis, and it was verified that it can be expressed, and its practical utility was also clear (paper No.30). Then, in order to study the applicability of the outdoor environment evaluation index ETFe that enables evaluation of behavioral thermoregulation, experiments were conducted on human subjects to clarify the effect of thermal environmental stimuli on the human body in outdoor spaces in summer. It was clear that the change factors imposed onto the thermal sensation vote of the human body by outdoor environmental factors during summer are heat conduction, humidity and short wavelength solar radiation (paper No.31). It was also seen that the tolerance limit of the human body is higher for thermal environmental stimuli in outdoor spaces compared to thermal environmental stimuli in indoor spaces in summer. It was clear that it was possible to use ETFe as a thermal environmental evaluation index for outdoor spaces in summer (paper No.32). Also, experiments on subjects were carried out to explain the change factors imposed onto the thermal sensation vote of the human body by outdoor environmental factors during winter. It was clearly explained that it was essential to incorporate humidity, short wavelength solar radiation, long wavelength thermal radiation, and heat conductivity as evaluation elements for outdoor thermal environment evaluation (paper No.33).
Chapter 10 describes research on the influence of thermal environment on human physiological and psychological responses, wherein the effect of thermal environment on humans is explained with the help of experiments on subjects, and a study of whether the conventional sensational and physiological temperature indices are effective is being conducted. Experiments to find out the effect of thermal environments on humans through their physiological and psychological responses are being conducted, with the help of a combination of symmetric and asymmetric scenarios for the left and right wall temperatures. In a scenario of asymmetric thermal radiation conditions, changes in the vote such as reciprocating a certain range for the comfortable side and the uncomfortable side, or the hot side and the cold side have been explained, and it clarifies that an unconscious choice of either of the thermal radiation on the left and right was made and the thermal sensation vote was given (paper No.34). Further, in the thermal environment representation by means of sensational and physiological temperature targeting the conventional homogeneous environment, it was clear that asymmetric and heterogeneous thermal environments could not be sufficiently represented, and hence this shows the necessity for taking into consideration the types of thermal radiation, such as hot and cold or the directivity of thermal radiation (paper No.35). With a focus on differences in posture, experiments on subjects are being conducted to clarify the effects of differences in floor heating conditions on humans. In living spaces in Japan, the necessity for thermal environment evaluation of each posture has been explained (paper No.36). Also, improvement in behavioral thermal environment due to changes in posture has been quantitatively clarified, by estimating the sensational and physiological temperature for each posture (paper No.37). Experiments on subjects have also been conducted, to determine the influence of 5 factors of the thermal environment: air temperature, air velocity, thermal radiation, humidity and heat conduction. After verifying that ETF is a thermal environment index that comprehensively represents the influence of temperature and air velocity, thermal radiation, humidity and heat conduction, it has been clarified that it is possible to evaluate the effect of posture and the effect of heat conduction between the human body and the environment in living environments (paper No.38). Then, experiments on subjects have been conducted to clarify the human influence of outdoor thermal environmental factors. Natural scenery observation points are compared with other scenery observation points, and it was clear that even though the mean skin temperature, which is a physiological value, increased, the decrease in the sense of comfort was very small (paper No.39). It was seen that natural spaces comprising greenery and trees were more effective in improving the sense of comfort, compared to man-made spaces made up of concrete or metal (paper No.40). Neutral mean skin temperature that produces a thermally neutral thermal sensation vote and a neither comfortable nor uncomfortable thermal comfort vote has been explained (paper No.41).
Chapter 11 describes research on comfortable thermal environment areas for humans, wherein a comfortable range of outdoor environment and a comfortable range for floor cooling has been proposed. In spaces where radiant floor heating and cooling are provided, the heat transfer area of the radiation source and the heat transfer area of the human body become significantly large, and the influence on thermal sensation and thermal comfort is stronger compared to spaces where only regular temperature is to be controlled. Subject experiments were done that throw light on the effect of the differences in floor cooling conditions on humans. Due to the effect of the cooling in floor cooling, a tendency of preference for the warmer side over the neutral thermal sensation as the value for the thermal sensation vote for the whole body was seen. For optimum thermal environment conditions of floor cooling in the leg-out sitting position, the range from 25.3 to 30.5 °C has been proposed for conduction correction action temperature (paper No.42). Then, it has been explained that there is a possibility of being able to set the floor cooling equipment to a higher indoor air temperature compared to air-cooling equipment, due to the cooling effect of the human body from heat conduction and thermal radiation that it receives from the floor surface (paper No.43). Subject experiments have been conducted to determine physiological and psychological responses of human beings in outdoor thermal environments in summer and winter, in order to propose the optimum thermal environment range in outdoor environments, where the influence of short wavelength solar radiation and heat conduction is significant. It has been proposed that the comfortable thermal environment range outdoors is from 31.6 to 38.5 °C in ETFe (paper No.44).
Chapter 12 describes research on analysis of human responses and the scientific description of the thermal environment. The goal is explaining the influence of thermal environment on humans, and utilizing the results for the creation or improvement of living environments. Research has been done on the development of a behavioral thermoregulation model and development of a three-dimensional numerical human model in the shape of a human body, for incorporating the data related to basic heat flow into the control system. There is also research on energy efficiency, focusing on posture as behavioral thermoregulation through sensational and physiological temperature expression.
A human-shaped model in the chair-sitting position is being developed with a focus on the heat transfer area of the human body, which forms the basis of the calculation of heat balance between the environment and the human body. Human body surface area, conduction heat transfer area, convective heat transfer area and radiant heat transfer area are essential factors for calculating the amount of heat exchanged between the human body and its surrounding environment; these have been explained with actual measurements using subjects, and its applicability has been quantitatively verified (paper No.45). Then, in order to verify the energy conservation effect of air conditioning equipment using thermal radiation and heat conduction, an experiment on subjects has been conducted in conditions where air temperature and floor surface temperature were combined. In the floor-sitting position where the conduction heat transfer area between the floor surface and the human body is large, it can be seen that it is possible to create a thermal environment where thermal comfort can be obtained by setting the floor surface temperature in floor cooling 1 to 2 °C lower than the air temperature (paper No.46). Next, environmental regulation behavior is replaced with physical and physiological coefficients such as air velocity and radiant temperature, amount of clothing, metabolic rate, heat transfer area, etc., and its relationship with human physiological and psychological effect has been studied. It has been indicated that environmental regulatory behavior can be incorporated into environmental household accounts (paper No.47). The thermal performance of detached houses is clear from the actual measurement results for thermal environment. The energy-saving effect of insulation retrofit in consideration of cost-effectiveness has been clarified through crude oil primary energy conversions (paper No.48). Next, to explain the energy saving effect of viewing greenery, experiments on subjects were carried out in the environment range of a rather uncomfortable temperature area. Landscapes including greenery demonstrated their effect on sensational and physiological temperature, thereby clarifying the significance of actively incorporating visual stimuli in indoor spaces (paper No.49). In order to estimate the thermoregulatory responses of humans who demonstrate behavioral thermoregulation in outdoor spaces, a thermoregulatory model has been developed by incorporating the model formula with the weight ratio of the skin layer of thermal conductance between human tissues through thermal conduction. Short wave length solar radiation, long wavelength solar radiation, and thermal effects from heat conduction have been incorporated as environmental factors. It can be seen that it is possible to express the effect of thermal environmental conditions such as short wavelength solar radiation or thermal conduction by means of the relationship with the outdoor thermal environment evaluation index ETFe (paper No.50).