Journal of Environmental Engineering (Transactions of AIJ)
Online ISSN : 1881-817X
Print ISSN : 1348-0685
ISSN-L : 1348-0685
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  • Yukie NAKAJIMA, Toshiharu IKAGA, Mari ONO, Tanji HOSHI, Shintaro ANDO
    2019 Volume 84 Issue 763 Pages 795-803
    Published: 2019
    Released: September 30, 2019

     Given the rapid ageing of the Japanese population, it is important to identify strategies to minimise the gap between healthy life expectancy and average life span. Cold-related injuries and symptoms have recently attracted attention, and studies on the relationship between blood pressure, falls, physical performance, and the thermal environment of housing have been reported. Based on previous studies, we hypothesised that people living in cold homes will receive certification for long-term care insurance earlier in life, indicating a shorter healthy life expectancy.

     This retrospective study involved 205 community-dwelling older adults living in Japan. Participants completed a self-report questionnaire about personal characteristics, housing, and perceived indoor temperature in their home during winter. Participants were divided into a Cold group and a Warm group based on perceived indoor temperature. Mean and minimum living room and bedroom temperatures differed between the Cold group and Warm group. On the other hand, mean, maximum, and minimum temperatures in the dressing room all differed significantly between the Cold group and the Warm group. Air conditioners were the only heating system that contributed to warmer indoor temperature. Maximum temperature was higher but minimum temperature was lower in houses with fan heaters, which may run intermittently and with short running time. Houses in which kotatsu systems or electric blankets were used tended to have colder indoor temperatures in the living room and bedroom.

     The Kaplan-Meier method was used to analyse the relationship between age at certification for needing long-term care insurance and perceived indoor temperature. Mean age at certification was 77.8 years in the Cold group and 80.6 years in the Warm group (p<0.01, generalised Wilcoxon test). Multivariate analysis by ANCOVA revealed a significant main effect of perceived indoor temperature, with the Cold group having a younger age at certification for needing long-term care (F(1, 197)=9.27, p<0.01). Estimated marginal means indicated that healthy life expectancy was 2.9 years shorter in the Cold group than in the Warm group even after adjusting for participant characteristics. When the relationship between measured indoor temperature and age at certification was tested, people living in houses with low indoor temperature (<14 °C) or high indoor temperature (≥18 °C) had a higher age at long-term care certification. People with low indoor temperature might spend longer time outside and use heating systems for shorter time. Since we could not grasp or control times going-out or using heating system, we conclude that relationship between measured indoor temperature and age at certification can support the previous result though, close investigations of indoor thermal environment in where older people lives are still needed.

     Our findings suggest that maintaining an appropriate indoor thermal environment could help prevent the need for long-term care.

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  • Yang HU, Daisaku NISHINA, Takahiro TANAKA, Wataru YAMASAKI
    2019 Volume 84 Issue 763 Pages 805-815
    Published: 2019
    Released: September 30, 2019

     Research on course selection is usually analyzed from the personal feature and external condition. About personal feature such as character, preference, etc.. Different personal features are deemed to have a great impact on the course selection behavior. In order to create a good street space, it is necessary to consider the personal feature. However, studies from the perspective of personal feature have not been sufficiently accumulated. When we choose the course, we will change direction or position and speculate that the characteristics of different people will be different.

     On the other hand, about external condition such as street shape, street pattern, facilities, etc., and the impact of street patterns on course selection is also considered important.

     Therefore, the purpose of this study is to clarify the relationship between the personal feature and course selection, by analyzing direction and position change of course in different street pattern.

     In order to avoid the influence of other external conditions besides street pattern, the experiments were carried out by the method of drawing courses on blank maps. We chose 12 maps with various street patterns. These were blank maps that consisted of only lines showing streets and blocks without buildings and urban facilities. About the experiment, the subjects were asked to draw courses on those maps, and answer face sheets at the end of experiments. We analyzed the results of coures selected, the subjects’ personal feature respectively and course selection strategies, then grasped the relationship among them. We show the knowledge provided from the experiment result below.

     First, as the results of course selection strategies, subjects recognize streets on maps as streets, and realize that they choose the course on the map.

     Second, different subjects showed different tendencies when they choosing course. For example, as the results of the change in the direction of the course, the subjects of Group 1 who most interested in strolling and they also have good spatial cognitive abilities, changed their direction frequently. In the subjects of Group 3, they lack preference of strolling and spatial cognition ability, they don't like to change direction.

     Third, on position distribution of course, the subjects of Group 1 tended to draw a long course and spread throughout the map, also they tended to draw a complex course. The subjects of Group 3 showed greater attention to the main streets or streets of special shapes and had a simple course near the starting point.

     Finally, from the complexity of the course, no matter which group of subjects, they do not always choose the streets have the same characteristics. Especially in the subjects of Group 1, their course varies frequently between complex streets and simple streets.

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  • Naoya HARA, Ryuji SATOH
    2019 Volume 84 Issue 763 Pages 817-823
    Published: 2019
    Released: September 30, 2019

     When designing the environment used by an unspecified number of people based on the evaluation of users, it is necessary to plan reflecting the variation of the evaluation criteria of a large number of people and the attributes of the people assumed at designing. In the visual environment design of the room targeting a large number of people, it is necessary to give flexibility to the design by introducing various design levels such as an rating level and an evaluation probability. The rating level is the degree of visibility of the visual target and the evaluation probability is the probability that the rating level is achieved.

     In this paper, in order to construct a design method that can reflect the rating level and the evaluation probability as the design level, the method of predicting the readability rating based on the regression coefficient by logistic regression that regress the relationship between the three visual factors and the readability of documents is presented.

     Based on the result of the subjective evaluation experiment of readability in the previous report, the relationship between three visual factors and readability is regressed by logistic regression, which is the linear regression model with setting the logarithmic odds of the probability being less than the neighboring boundary of readability category as the objective variable and three visual factors as the explanatory variable. With introducing a method of constructing a readability scale from the probability that can be predicted by the regression, it is proposed to formulate the relationship between three visual factors and readability.

     Consistency is examined on readability of the experimental data in the previous report and that obtained by manual regression of that data and that predictted by the three kind of regression models. For the formulation of the relationship between three visual factors and the design level, the regression model is chosen as a most suitable one in which the regression coefficient is determined for each different adjacent category boundary and for each different range of adaptation luminance. The good relationship between three visual factors and readability predicted by this chosen model is shown and a useful readability prediction method for visual environment design is presented in this paper. The prediction method shown in this paper is useful for facilitating examination of visibility while introducing various design levels in visual environment design.

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  • Mao SERIKAWA, Masayuki MAE
    2019 Volume 84 Issue 763 Pages 825-834
    Published: 2019
    Released: September 30, 2019

     This study investigates an appropriate representative temperature in an apparent specific heat measurement of Phase Change Materials (PCM) through a thermal conductivity analysis. The representative temperature is used when apparent specific heat is calculated from the temperature and heat flux time series data, which affects the apparent specific heat result.

     PCM contributes to the temperature stability in houses. However, previous studies lack established experimental methods of PCM installation in buildings. The present study aims to investigate and propose experimental and calculation methods for a PCM.

     Chapter 1 introduces the purpose of this research, which is to propose a decision procedure of the representative temperature for PCM specimens through a thermal conductivity analysis. The representative temperature is used when apparent specific heat is calculated from the temperature and heat flux time series data. Consequently, this has a significant influence on the measurement result of the apparent specific heat. In specific heat measurements, one or both of the surface and central temperatures of the PCM are usually measured. This study aims to confirm whether surface or central temperature is appropriate as the representative temperature. Furthermore, this work aims to search for a better method of calculating the representative temperature from the surface and central temperatures of the PCM.

     Chapter 2 presents the method of investigation. A thermal conductivity analysis that reproduces specific heat measurement is used. A total of 27 types of PCM with several levels of thermal conductivity, latent heat, and temperature range of phase change are examined. An index of the ratio of the central temperature (i.e., temperature between two flat PCM specimens) is defined for the examination. This index is used to calculate a weighted average temperature of the PCM from the surface and central temperatures. Further, the apparent specific heats are calculated from the surface and central temperatures and the ratio of the central temperature for each PCM to verify the measurement accuracy. The calculated apparent specific heats are compared with the accurate apparent specific heats input into the calculation.

     Then, Chapter 3 shows the calculation results. Consequently, using the weighted average temperature of the surface temperature of the PCM specimens and the temperature between the two specimens as the representative temperature appears appropriate. The appropriate rate of the temperature between the specimens is affected by thermal conductivity, latent heat, temperature change rate, and, in particular, the temperature range of the phase change (i.e., 0.7–1.0 depending on the conditions).

     Some issues must be considered when correcting the measurement error caused by the temperature distribution within the PCM specimens. These issues are presented in Chapter 4.

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  • Isamu GOMI, Sachiko NISHIKAWA, Shun KATSUMATA, Hiroya KAMATA, Taito KI ...
    2019 Volume 84 Issue 763 Pages 835-843
    Published: 2019
    Released: September 30, 2019

     The heat transfer from window affects indoor environment. It is important to evaluate the characteristics. In the case of window with shading devices such as screens, curtains, and Venetian blinds, thermal properties are affected by ventilation between the cavity, which is formed between the glazing surface and the shading device, and the room.

     There are many studies about the heat transfer from the window with internal blinds. In some previous studies the calculation model is presented based on the assumption that the ventilation was occurred by the stack effect depending on thermally-driven pressure. However, the model could not describe well our previous experiment results probably because the shape of blinds effects the airflow and thermal properties. There are also the studies on predicting the convective heat transfer coefficient from the viewpoint of temperature difference between the glazing surface or the blinds surface and air by experimental and numerical study. However, these research has focused mainly on the window which has a relatively narrow cavity.

     To reveal the airflow and thermal properties of the window which has a relatively wide cavity, we conducted Particle Image Velocimetry (PIV) and Computational Fluid Dynamics (CFD) analysis. The analyses were made with the window with internal blinds of which cavity was 130mm width and in a total of 24 cases (3 slat angle of Venetian blinds and 8 patterns of temperature condition). The experimental apparatus consists of a glass pane, a Venetian blinds and an aluminum panel. The glass and blinds were heated by energization to simulate absorption of solar radiation and the aluminum panel was heated or cooled by a chilling unit. CFD modelling was made to reproduce the experimental setup. Results are given in the form of airflow velocity, airflow rate, and convective heat transfer. Comparison of PIV and CFD results shows the following:

     1) The airflow vector map from CFD results were in almost good agreement with PIV. The CFD model described here could be used for predicting the airflow properties of the window with relatively wide cavity. In CFD, the airflow snaking through the blinds slats was observed.

     2) The larger the temperature difference between the glass or the blinds and the cavity, the larger the airflow velocity, airflow rate, and convective heat transfer. For the maximum vertical airflow velocity of the cavity, CFD results were slightly larger than those of experiment. However, the thickness of velocity boundary layer in experiment is larger than CFD, which indicates that diffusivity is higher in the experiments. Consequently, the airflow rate in CFD was slightly smaller than those in experiment.

     3) Blinds slat angle does not significantly affect the velocity, airflow rate and convective heat transfer both in experiment and CFD.

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  • Yumiko ARAKI, Yosuke WATANABE, Koya WAKABAYASHI, Shin-ichi TANABE, Shi ...
    2019 Volume 84 Issue 763 Pages 845-854
    Published: 2019
    Released: September 30, 2019

     In Japan, there are many residential houses built before 1980 and many houses with low thermal insulation performance do not meet current energy-saving standards. Low insulation performance results in lower temperatures during winter, which may adversely affect health. In fact, health damage caused by cold houses is a continuing issue, with heat shock responses, sleeping disorders, etc. becoming a social problem. In order to improve this situation, it is desirable to present information on the improvement effect of the winter thermal environment accompanying the improvement of heat insulation / airtight performance to residents. In addition, to improve the living environment that supports the health of residents, it is necessary to encourage renovation of houses to include insulation and laying of heating devices in non-living rooms.

     Given this background, Serikawa et al. proposed a thermal environment evaluation method utilizing the CASBEE Housing Health Checklist. Using this method, the operative temperature, floor temperature, and room operative temperature difference calculated by a thermal environmental simulation tool are converted into “Score on the Warmth” of houses in winter.

     However, this method of evaluation has not been verified to be consistent by other subjective experiments. The purpose of this research is to confirm whether the "Score on the Warmth" matches the actual human physiological and psychological response.

     Subjective experiments were carried out under five conditions with a combination of air temperature controlled by floor heating / air conditioner and floor temperature. Further, considering the movement between rooms, a series of procedures of moving from room A controlled at an air temperature of 23 Degree Celsius or 25 Degree Celsius, to room B at 10 Degree Celsius or 17 Degree Celsius, simulating a cold room and returning to room A Stepping. A total of 32 subjects, 8 males and 24 females, reported thermal sensation and satisfaction in each condition and scored the thermal environment over a score of 100 points. Also, in order to see the physiological response, skin temperature, blood flow rate, and blood pressure of each person were measured. The results of the experiment are as follows.

     It is shown that the living environment is accurately evaluated as compared with the PMV which assumes a uniform environment. “Score on the Warmth” is considered useful as an index to evaluate the comfort and satisfaction of residents against living environment in Japan. It was shown that the coldness of a non-living room reduces the average skin temperature of occupants. The reduced average skin temperature does not return to its original state even if a person returns to a comfortable room. Therefore, it can be said that adjusting the temperature for a non-living room, such as a toilet and a dressing room, to a warm environment is important for maintaining and improving the health of residents.

     When the comfort declaration exceeds 80%, the warmth of the room is 2.8 points, and the score of warmth when it exceeds 90% was 3.0 points. In conclusion, it is possible to predict the risk of developing colds in winter houses by using “Score on the Warmth”. In this study, the usefulness of the evaluation method for 5 items, excluding the coldness of the bedroom and the drying of the bedroom was verified. It is expected that it will be a more useful evaluation method each time the question on the warmth of the CASBEE Housing health checklist and the relationship between various diseases become clear.

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  • Hikaru IMAGAWA, H. B. RIJAL, Masanori SHUKUYA
    2019 Volume 84 Issue 763 Pages 855-864
    Published: 2019
    Released: September 30, 2019

     In daily life, we conduct the various occupants’ behaviours for thermal comfort and health. The stochastic models of occupants’ behaviours were analysed by some previous studies. Especially, the models of window open in previous studies were analysed by Gaussian function, polynomial logit and logistic regression linked to linear function in FR mode (Free Running: without heating & cooling being used mode). However, Gaussian function has the symmetrical curve, and the regression coefficient of polynomial logit need many number of digits. And, the model of window open in FR mode was not compared with air conditioner use. Moreover, it is important to understand the relation between the opportunities of each behaviours because these affect each behaviours. From these, we need to analyse the relative proportions of each behaviour in the integrated single stochastic model with the concept of figure 1. In order to integrate the models of the window open/closed, cooling (CL) and heating (HT) use, we analysed the occupants’ behaviour model using the logistic regression method with the data collected in Japanese dwellings. We have measured the air temperature, relative humidity and globe temperature in 120 dwellings, and conducted occupants’ behaviour survey during 4 years. From this series of survey, we have collected 36,154 responces all together. The integrated model was calculated by the following equation.

    PW = PFR×PWFR ={1 – (PHT + PCL)}×PWFR

     where PW is proportion of window open in mixed mode (considering FR, CL and HT), PFR is proportion of FR mode, PHT is proportion of heating use, PCL is proportion of cooling use and PWFR is proportion of window open in FR mode. This integrated model showed the relative proportion of each behaviours can be expressed as follow.

    PHT + PCL + PW + PWCFR = 1

     where PWCFR is the proportion of window closed for neither heating nor cooling use in mixed mode. The major findings are as follows: 1) the logistic regression equations of window open/closed, cooling and heating use were integrated into a single occupants’ behaviour model as a function of outdoor air temperature. This model represents the relative proportion of each behaivours: window open/closed, heating on/off and cooling on/off. 2) In this model, the maximum proportion of window open was 0.47 at 26.0 °C of outdoor air temperature. The proportion of window open decreases when outdoor air temperature is either lower or higher than 26.0 °C. The proportion is calculated by the increasing the cooling use. 3) The regression coefficient of this model was simpler than the polynomial logit. The regression curve of window open model is asymmetric. 4) When the outdoor air temperature was 28.3 °C, the proportions of either window open or cooling use are 0.44. If the outdoor air temperature is lower than 28.3 °C, the proportion of window open become higher than cooling use, and vice-versa. From these results, it can be said that this integrated model is effective to know the combined effect of occupants’ behaviours on the using of window, mechanical heating and cooling. Moreover, this integrated model is useful to implement in the building thermal simulation for predicting the energy use in buildings.

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  • Yuki OGAWA, Kiyotaka DEGUCHI, Shun KAWAKUBO, Tsubasa OKAZE
    2019 Volume 84 Issue 763 Pages 865-872
    Published: 2019
    Released: September 30, 2019

     The Gassho-style houses in the historic villages of Shirakawa-go and Gokayama are among the most famous examples of Japanese vernacular architecture. The houses have thatched roofs that are notable not only for their design but also for their passive performance. In particular, the houses of Shirakawa Village are been well adapted to the local terrain, climate, and culture. However, no studies have considered the terrain around Shirakawa Village, particularly the topographic features of the Shohgawa River Valley, though they are likely has an effect on the houses.

     In surveys conducted to date, there are many issues to address. For example, no simulations or measurements have considered the effect of topography on the wind environment, and details about heating are not yet clear. Here, the advantageous characteristics of the houses are investigated from the perspective of environmental engineering through actual measurements and computational fluid dynamics (CFD) simulations.

     First, the wind environment of Shirakawa Village was evaluated by CFD analysis using a complex topography model. Visualization of the results showed that the wind flows from the north and follows the contours of the land. The wind speed increases around the center of basin and decreases in curved and narrow area. The wind speed is also decreased by dense houses. In sum, the simulation shows that Ogimachi is a low wind environment.

     Second, the thermal environment in the houses in summer was investigated. The thick thatched roof prevented sharp increases in temperature and maintained a comfortable environment. The daily temperature range in the attic surrounded by the thatched roof was narrower than that on the first floor, which is framed by board walls. Within the context of sericulture, the room air temperature and wind speed in the attic represented an appropriate environment for silkworm breeding.

     Third, the thermal environment of the house in winter was investigated. The effect of radiant heat from the heater was able to reach only a limited area, and the room temperature inside the houses was low. Also, snow guard fence improved the heat insulation capacity of the house, diminishing heat loss. Warm air diffused upward by convection, and the temperature tended to rise over a wide area on the second floor. Thermal sensation near the heater was improved by the increase in radiation temperature although it did not reach a comfortable level. The environment in much of the house was cold but tolerable, as the Gassho-style houses were adapted for the climate in Shirakawa Village to suit both summer and winter.

     About a quarter of Shirakawa Village, covering an area larger than a city block, was targeted as the analysis region for validation. Analysis results for the wind environment of the uneven terrain were used as the boundary conditions in the analysis of the houses. In this study, the Reynolds-averaged Navier–Stokes equations were used as a turbulence model and the simulation was run using structured grid, but the use of large-eddy simulation and an unstructured grid is being considered for future research. The accuracy of the analysis remains an issue, though this method can be used to assess the influence of geography and climate in the surrounding area. The results of this research are expected to be useful for introducing passive technology into architectural design.

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