Tohru Mochida

Development of thermal-photovoltaic hybrid exterior wallboards incorporating PV cells in and their winter performances

The authors have developed experimental thermal-photovoltaic (PV) hybrid exterior wallboards that incorporate of PV cells. The clapboard-shaped hybrid wallboards permit modular assembly that can be more easily adapted for building applications than previous PV systems. Solar heat is collected in the form of heated air circulating in the air gap between the hybrid wallboard and the thermal insulation of the exterior walls. This paper presents an evaluation of both the electrical power generating ability and the solar heat collection capacity during winter of six variations of the experimental thermal-PV hybrid wallboard. In addition, exergy analyses were conducted.

Influence of natural convection on forced horizontal flow in saturated porous media for aquifer thermal energy storage

Abstract Estimation of the heat recovery rate in high-temperature underground storage (>50 °C) is required before such a system can be built. However, if high-temperature water is injected into and stored in the aquifer, large-scale natural convection could occur that might reduce the heat recovery rate. This study aims to clarify the universal quantitative condition under which natural convection appears and exerts an observable influence for a system with forced horizontal flow in the saturated porous medium. The authors investigated this using both experiments and computer simulations. A test section simulating an aquifer was made. Warm water was injected into the test section, which was filled with glass beads. The temperature distribution and the flow rate profile at the outlet were measured. The authors found that the limit condition at which natural convection influences the forced horizontal flow can be determined from the velocity profile and modified Rayleigh number Ra*. In addition, the heat transfer coefficients of the upper and the lower side of walls were estimated. A computer simulation was made for calculation of the temperature field and the velocity vector in the porous medium under natural convection and under forced convection. As calculated temperature fields and flow rate distributions at the outlet were similar to the experimental results, it is thought that this program can be applied to evaluation of the temperature and the velocity of aquifer thermal energy storage. In addition, an index expressing the degree of influence of natural convection on forced convection was proposed.

Experimental study on convective heat transfer coefficient of the human body

Abstract 1. 1. The convective heat transfer coefficient of the human body is essential to predict convective heat loss from the body. 2. 2. The object of this paper is to calculate the convective heat transfer coefficient of the human body using heat flow meters and to estimate the thermally equivalent sphere and cylinder to the human body. 3. 3. The experimental formulae of the convective heat transfer coefficient for the whole body were obtained by regression analysis for natural, forced and mixed convection. 4. 4. Diameters of the thermally equivalent sphere and cylinder of the human body were calculated as 12.9 and 12.2 cm, respectively.

Experiments to determine the convective heat transfer coefficient of a thermal manikin

Abstract In order to determine an equation for calculating the convective heat transfer coefficient in humans, that can be used in an outdoor environment, experiments using a thermal manikin were carried out at an air velocity in the range of 0.7–4.7 m/s. The convective heat transfer coefficient of the naked human body almost agreed with that of the clothed human body with two clothing ensembles. Empirical formulae of the convective heat transfer coefficient for the whole and 10 parts of the body were calculated using experimental data at an air velocity in the range of 0.1–1.0 m/s, which are applicable formulae at an air velocity in the range of 0.1–4.7 m/s. The thermal insulation of the two clothing ensembles decreased with increasing air velocity.

Effective radiant temperature including solar radiation

An evaluation method for thermal sensations of the human body in an outdoor thermal environment was developed. Effective radiant temperature was proposed as the mean radiant temperature in an outdoor environment. The operative temperature and standard new effective temperature, SET*, in outdoor environments could be calculated using the effective radiant temperature. In order to examine the operative temperature and SET* based on the effective radiant temperature, experiments using subjects were carried out in an outdoor environment at Sapporo city. The SET* calculated from experimental data correlated well with the thermal sensation votes of the subjects. It was shown that a SET* based on the effective radiant temperature can evaluate the thermal sensation of the human body in an outdoor environment.

Expansion of effective wet bulb globe temperature for vapor impermeable protective clothing

The wet bulb globe temperature (WBGT) is an effective measure for risk screening to prevent heat dISOrders. However, a heat risk evaluation by WBGT requires adjustments depending on the clothing. In this study, we proposed a new effective WBGT (WBGTeff*) for general vapor permeable clothing ensembles and vapor impermeable protective clothing that is applicable to occupants engaged in moderate intensity work with a metabolic heat production value of around 174W/m2. WBGTeff* enables the conversion of heat stress into the scale experienced by the occupant dressed in the basic clothing ensemble (work clothes) based on the heat balances for a human body. We confirmed that WBGTeff* was effective for expressing the critical thermal environments for the prescriptive zones for occupants wearing vapor impermeable protective clothing. Based on WBGTeff*, we succeeded in clarifying how the weights for natural wet bulb, globe, and air temperatures and the intercept changed depending on clothing properties and the surrounding environmental factors when heat stress is expressed by the weighted sum of natural wet bulb, globe, and air temperatures and the intercept. The weight of environmental temperatures (globe and air temperatures) for WBGTeff* for vapor impermeable protective clothing increased compared with that for general vapor permeable clothing, whereas that of the natural wet bulb temperature decreased. For WBGTeff* in outdoor conditions with a solar load, the weighting ratio of globe temperature increased and that of air temperature decreased with air velocity. Approximation equations of WBGTeff* were proposed for both general vapor permeable clothing ensembles and for vapor impermeable protective clothing.

Heat balance model for a human body in the form of wet bulb globe temperature indices

The purpose of this study is to expand the empirically derived wet bulb globe temperature (WBGT) index to a rational thermal index based on the heat balance for a human body. We derive the heat balance model in the same form as the WBGT for a human engaged in moderate intensity work with a metabolic heat production of 174W/m2 while wearing typical vapor-permeable clothing under shady and sunny conditions. Two important relationships are revealed based on this derivation: (1) the natural wet bulb and black globe temperature coefficients in the WBGT coincide with the heat balance equation for a human body with a fixed skin wettedness of approximately 0.45 at a fixed skin temperature; and (2) the WBGT can be interpreted as the environmental potential to increase skin temperature rather than the heat storage rate of a human body. We propose an adjustment factor calculation method that supports the application of WBGT for humans dressed in various clothing types and working under various air velocity conditions. Concurrently, we note difficulties in adjusting the WBGT by using a single factor for humans wearing vapor-impermeable protective clothing. The WBGT for shady conditions does not need adjustment depending on the positive radiant field (i.e., when a radiant heat source exists), whereas that for the sunny condition requires adjustments because it underestimates heat stress, which may result in insufficient human protection measures.

Invitation to Japanese Society of Human-Environment System

The Industrial Revolution, which began in England at the end of the eighteenth century, resulted in “affluent society,” characterized today by mass production and enormous consumption. On the other hand, accelerated by population increases and its accompanying enlargement in energy consumption, the environment started to deteriorate, calling to the minds of people the problems concerning the global environment. One such cause is peoples desire to seek convenience and comfort in the broad sense. Today, having realized the limitation of what the global environment can endure, the very basics to sustain the continuation of life of all species, inclusive of mankind, is to grasp accurately the condition under which we live and to look into the future with a firm decision to divert ourselves from the lifestyles and habits that we have been accustomed to In other words, such diversion extends to matters pertaining to the lives of individuals, their awareness of others and surrounding conditions, their criteria for values and quality of life. Once having taken note of these, in order to clarify the various problems concerning people and their environments and to provide solutions for them, one must be able to maintain a system to accumulate and analyze data, open them to the public, and to forecast the future, to propose, to guide and to direct to the solution, which will be widely and easily accepted by society. By doing so, we hope to create a society where people can enrich a sense of humanity and share the responsibility of mankind.

Characteristics of wettedness under constant average skin temperature

Abstract 1. 1. Experiments were carried out concerning the characteristics of wettedness revealed under constant average skin temperature using sitting-resting nude subjects. From the basic measurements of both environmental parameters and human physiological responses, the conclusions detailed below were proposed regarding the changes of wettedness under constant average skin temperature. 2. 2. There is positive correlation between the wettedness and environmental humidity, and negative correlation between the wettedness and air temperature. 3. 3. There is positive correlation between the evaporative heat loss from the skin surface and air temperature, and negative correlation between the evaporative heat loss and environmental humidity. 4. 4. There is negative correlation between the wettedness and evaporative heat loss. 5. 5. Wettedness is not constant but takes varying values, that is, corresponding to each average skin temperature both the maximum and the minimum wettedness values occur. 6. 6. Deriving from the items mentioned above, the theoretical locus of equal average skin temperature is not a straight line, but is a curved line plotted on the psychrometric chart.