As seen from better performance of the recent solar collectors, their technical improvement owes deeply to their increasing usage. Nevertheless, to promote further use of these elements, there are still many technical problems to be solved, such as reduction of the unavoidable heat loss and element corrosion and durability. Radiative heat loss can be attributed to the selective surface treatment, but losses by conduction and convection are really a heat transfer problem itself. Free-convection in an enclosed space, as observed in a solar collector for example, is very familiar. Due to very complex phenomena, however, adequate information is not always available for designing a solar collector having suitable dimensions from viewpoint of less heat loss by conduction and convection despite of the many papers concerning the subject. The purpose of this reseach is to supply further information on free-convection heat transfer across enclosed and inclined air layers, including horizontal and vertical attitudes. Experiments were carried out using appratus resembling a plate-type solar collector whose absorber plate is heated by an electric heater. The experimental results were compared to the theoretical values obtained concurrently by numerical analysis and were found to be satisfactory in the experimental accuracy. Several photographs showing the air flow pattern affected considerably by Rayleigh number Ra and angles of the inclination φ[degree] are also presented in this paper to assist in visual understanding the change of value of the Nusselt number Nu. In addition, the following experimental equations are revealed: Nu=0.038Ra^<n_1> for the range of small Rayleigh number, and Nu=0.176Ra^<n_2> for the range of large Rayleigh number, where n_1=0.443-0.93(φ/90°) n_2=0.28-0.066(φ/90°) These expressions are in good agreement with the experimental results obtained for φ&gsim;30°

View full abstract

This report describes measurements made in a real factory building and comparisons with the scale model tests presented in the previous report. The ventilation system of the factory building is a mechanical one with the necessary rate of ventilation designed to be less than that calculated by the conventional method. The parameters studied included air velocities measured with hotwire anemometers at the inlet openings and the temperatures in the work hall itself measured from a crane. The masses and heat flows of air entering and leaving the hall through openings were determined and their balances were examined. In practice some fluctuations are unavoidable and there are some limitations on the simulation of the full details of buildings. Nevertheless, measurements in a real building are in reasonable agreement with the model. It is believed that in most cases models provide the only way of investigating temperature distributions, and a new method of designing ventilation has been made available.

View full abstract

The characteristics and design principles of water storage tanks have been established by various experimental and theoretical studies. However, the performance of the storage thank deteriorates drastically when the temperature difference between the inlet side and outlet side of the tank is reduces. The thermally-balanced storage tank is proposed and designed as a countermeasure against this. This tank has two additional sub header pipes connected to the main tank by several connecting pipes. Thermally stratified heat storage is achieved by selective input corresponding to the temperature profile in the main tank and the input water temperature. This paper first introduces the principle and objective of the thermally-balanced storage tank. Experiments were conducted under various conditions to estimate the performance and characteristics of the tank, and they were proved by visual tests. The results of these experiments indicate that the thermally-balanced storage tank is effective in maintaining stratification for variable water temperature systems, and that three connecting pipes between the header and main tank seems neccesary and sufficient. Thermosyphon system for solar collection, however, does not require balanced storage because of its self regulating effect. Visual tests clearly proved the principle and selective operation of the water input due to pressure difference.

View full abstract

Ground surface temperature is a major element of the thermal environment, that is, atmospheric temperature and radiation to building or human body, and its characteristics should be predicted. While most former studies on this problem have focused on the thermal characteristics of surface materials, the amount of absorbed solar radiation which is converted to ground surface temperature also varies with the surrounding buildings which cut off the insolation. This study investigates the calculation method and characteristics of actual incident solar radiation and ground surface temperature in built up areas. First, after considering the sky factor, incident solar radiation and interreflection between walls and ground surface, the thermal characteristics of the ground surface in a two dimensional urban canyon are clarified. (1) The smaller the ratio of wall height to floor (ground surface) width, the larger the change of sky factor and incident solar radiation. (2) Floors in a east-to-west canyon are exposed to the largest amount of solar radiation in the summer and the smallest in the winter. This is opposite for north-to-south canyon. (3) The influence of interreflection between walls and floor on the rise of floor temperature is small compared to the influence of road orientation and the ratio of wall height to floor width. (4) The highest floor surface temperature in an east-to-west canyon may appear not in midday but after sunrise or before sunset. Subsequently, after the methods of calculating the distribution of the sky factor, incident solar radiation and ground surface temperature in three dimensional urban space are mentioned, the incident solar radiation and ground surface temperature in the Shinjuku area with many high rise buildings are investigated as a case study. Especially, the calculated distribution of ground surface temperature is compared with the thermal infrared image obtained by aircraft remote sensing. (5) The sky factor on the ground surrounded by high rise buildings in the Shinjuku area is 0.2〜0.6. (6) The ratio of incident solar radiation per day to total horizontal radiation is 0.2〜0.7. (7) Calculated distribution of ground surface temperature roughly agrees with the thermal infrared image. Consideration of incident solar radiation is as indispensable as that of materials for estimating the thermal environment.

View full abstract

The efficiency of various types of ventilation systems is examined by numerical calculation for two-dimensional, isothermal, and turbulent flow models. It is found that the ventilation is effective when the main pass length of the supplied air flow in a room is long. Since the slope of the concentration decay seems to become virtually constant and independent of the position in the room, this slope is proposed as a criterion for the ventilation efficiency. Further, a new convenient ventilation model is presented with the introduction of two parameters showing the ventilation efficiency and the effect of the pollutant generation site.

View full abstract

The Double Skin, which is a glass-covered space similar to a greenhouse is provided on the south side of an office building, Ohbayashi-gumi Super Energy Conservation Building. The Double Skin reflects she sun and releases heated air by natural ventilation in summer, and works as a solar collector in winter. This paper describes the evaluation of the performance of the Double Skin in the summer and the winter mode. In the summer mode, the air temperature in the Double Skin is only 3〜4℃ higher than the outside ambient air temperature. The air in the Double Skin is changed about 50〜100 times an hour by natural ventilation on a fine and calm day. The thermal structure in the Double Skin is that of 50% of incident solar energy reflected, 33% released by ventilation, and the remainder penetrating inro the room as cooling load. In the winter mode, the fresh air taken into the air handling units is heated by solar energy passing through the Double Skin. Efficiency of solar collection to the insolation is about 16% and the outlet air temperature is between 27 and 32℃. The Double Skin collects solar energy of 500kcal/m^2・d on a fine day in the winter. Energy saving performance concerning heating and cooling load by the Double Skin is 22% in the summer mode and 24% in the winter mode. The Double Skin is verified to be an effective energy saving system against the cooling and heating load through a year.

View full abstract

Water hammer is attracting the attention of engineers for its importance in the appropriate design of water supply piping system. This report attempts to present the experimental method and study on it by using check valves. The study consists of experiment, survey, and numerical procedure. The results of the study on the water hammer by using several check valves through experimental comparison are described as follows, 1) The maximum pressure rising rate increases as the weight of the check valve decreases. 2) The maximum pressure rising rate increases as the time from the point of electricity shut-off to that of the onset of pressure rising (Pt.C) is getting long or the time from Pt.C to the point of the first peak after Pt.C is getting short. 3) The column separetion occures when the pipe length from the reflection point of pressure wave to the check valve is short. 4) The water level of the pressure tank is to be kept higher to avoid surging during experiments. The survey and numerical studies on water hammer by using check valves are to be described in Part 2.

View full abstract

The first paper reported the characteristics of the discharge flow which occurred when an S trap was attached to a sanitary fixture. These flow characteristics were researched from the standpoint of the relation between water supply and drainage systems. This report is the second of a series on experimental studies on the influences of water seal loss in traps attached to sanitary fixtures and analysis of the mutual relation of multiple fixtures set in certain positions. The water seal loss in a trap is influenced by the inlet angle of the discharge branch pipe and the position of some fixtures. The results of experiments conducted to observe the flow characteristics, water seal loss, pressure in fixtures pipe and so on make it clear that delayed flow at the joints is a major cause of water seal loss in a trap. Based on these results, the generation of pressure in a discharge pipe which influences traps was considered.

View full abstract