The flat plate collector is aplicable for not only hot water supply & space heating but also cooling systems. In this paper, we have established the theoretical heat balance formula of collector surface and have operated the system simulation of medium scale office building with solar energy systems as application sample in order to study the possibility and economy. As the result of simulation, in office building, even if the solar collector is not large enough owing to its space conditions, the solar energy system can be applied as an auxiliary for the ordinary heating and cooling systems. Further more, regarding to the amount of energy of solar collector per unit space, it has much more posibility in utilization as auxiliary system.

View full abstract

The auther mentions to the calculation method of the multi-room temparature fluctuation. Using the Weighting Factor relating to the fluctuation of mono-room, the iterative calculation makes it possible to calculate each non air conditioned room. By using computers, we can gain the temparatures easily. The auther explains the calculation examples of the three model building. They are light weight office building and middle weight one and the apartment house. In conclusion, non air conditioned room temparatures are moderately close to air conditioned temparature.

View full abstract

The purpose of this paper is to propose how to estimate the heat load through a floor and a basement wall. First, the temperature distribution in the earth, floor and walls is computed making use of the computer program for the two-dimentional finite difference method of explicit form derived from a heat conduction differential equation. Then, the heat loss through a floor and a basement wall is calculated using the surface temperature distribution on them. Heat loss at steady state can be obtained when the deviation between inside and outside temperature is given as a constant value for a boundary condition, and storage heat load in the case of intermittent heating can be calculated when the periodically changing room temperature is given for it. These computed results are arranged into formulae and data for a heating load estimation.

View full abstract

The purpose of this study is to investigate the feasibility of solar (domestic) hot water supply for apartment houses. Although it is well known that the solar water heaters for rural houses are common in moderate climate districts of Japan, but the applications of the solar hot water supply systems (SHWS) for apartments are few yet. But because of the rapid increase of the cost of energy after the "energy crisis" and the steady growth of the energy consumption for hot water supply, due to the level-up of the standard of life, the importance of introducing the solar heat to conserve that energy is recognized, not only by the goverment but also the inhabitants. In this paper, first, many solar systems, which can be applied to the apartments are evaluated and a basic SHWS is selected to evaluate the solar-percent, and net energy savings per year per flat, etc. for given collector area, storage capacity by the computer simulation. The demand of the energy of hot water is fixed to ca. 3.1 Gcal/a. flat. Standard year-round weather data for Tokyo, developed by SHASE for estimating the heating and cooling loads are used to this purpose. The collectors are of flat-plate type, and the solair temperature method is used to caluculate the collector efficiency. The hot water storage tank is assumed to be fully mixed, when the collection pump is in operation, and piston flow, when not in operation. The results of the computer simulation are shown in Table 3, Fig.4, Fig.5. Simulation and experiment are compared in Fig.7. Fig.8 shows the two SHWS applied to 5 storied apartment house. Each system covers 10 flats. The annual net profits of these systems are shown in Table 8, Fig.9. Pay-off periods are shown in Table 9.

View full abstract

The dividing flow mechanisms in pipe junctions are studied in a systematic way. The dividing flows with arbitrary branching angles and areal ratios were analyzed by using the free-streamline methods, and the analyzed results were evaluated. Experiments on flow patterns in laminar flow were made in pipe junctions with different branching angles and areal ratios. Surface pressure distributions along the pipe wall of the pipe junctions were measured in turbulent flow. The computed results based on analysis were compared with the experimental results in circular conduits, and it is shown that both results coincide fairly well.

View full abstract

This paper reports a heat-wake method for measuring extremely low velocity. The advantage of this method is that the measurement is not affected by the variation of air temperature. The probe consists of three wires. The upstream wire is heated periodically by an electric current. A temperature fluctuation is produced behind the wire, convected downstream and used as a tracer of the velocity. The two downstream wires are sensor-wires which are operated at a constant temperature. The fluctuation is detected by the second and the third wire with a time delay corresponding to the time of flight from the second wire to the third wire. The two signals from the wires are fed into the circuit, amplified and converted to square-waves. After subtracting and integrating, the final output is obtained as d.c. voltage proportional to the time delay. The velocity of the flow is inversely proportional to the output voltage. The performance of the instrument is as follows. Velocities from 0.1m/s to 1m/s can be measured with good resolution. The relation between the velocity and the output does not vary when the temperature of air varies from 15℃ to 50℃. The quick response of the instrument enables continuous measurement of velocity by traversing a probe. This method is useful at extremely low velocities of the flow, such as natural convection, which includes temperature fluctuations.

View full abstract

It is fundamentally important to analyse the air flow excited by natural convection in a room with several openings for making clear such the phenomena as natural ventilation in a room, spreading of air and smoke with high temperature in fire situation and propagation of combustible gases in leakage accident. In this report, we tried to compute numerically one of these phenomena, natural ventilation. Although many numerical studies have been published to date for the purpose of calculating the natural convection flow in a closed enclosure, reports on this type of study in a room with openings have apparently been scanty, and there are some difficult problems in numerical calculation of natural convection in a room with openings differing from that in closed enclosure such as boundary conditions of velocity at the openings, because the velocities at openings are not decided in advance. Main aspects of numerical method used in this report are as follows, 1) Calculated room are two dimensional and have openings with various dimensions and positions, and the flow is assumed to be laminar and buoyancy effect by temperature difference is simplified with Boussinesq approximation. 2) Because it is not possible to set the velocity boundary conditions beforehand in present calculations, we use velocities and pressure as dependent variables in place of vorticity-stream function method which we have used up to this time for two dimensional problems. 3) Both of steady approach which solves directly steady Navier-Stokes equations and unsteady approach which gets the steady state by the method of time evolution of the flow are used and characteristics of these two methods are tried to compare. ADI method is used for time derivative in unsteady approach. 4) Relatively coarse mesh spacing of 16×16 is used in order to saving the computing time, therefore quantitative accuracy of calculation is regarded to be rather poor, but qualitative accuracy can be claimed. Calculations are performed for eight types of rooms with various positions of opening and various dimensions and positions of heat source, and one of these types has three kinds of opening dimensions. Calculations are moreover performed about natural ventilation caused by winds and by the combination of temperature difference and winds. As a results of these investigation, it becomes clear that predictions such as patterns of stream lines and temperature distributions and ventilating air change are considered to be reasonable. It seems to be necessary in future to compare these results with experimental values for verification of quantitative computational accuracy and to improve the method of calculation by these tasks.

View full abstract

Magnetic filters, consisting of fine ferromagnetic wires to provide sharp local field gradients in a uniform magnetic field, can separate fine, even weakly magnetic particles from fluid streams. This technique is called high gradient magnetic separation (HGMS) and has been applied to operations; mineral beneficiation, magnetic desulfurization of coal and water pollution control. If economically feasible, this technique appears useful for the separation of steel, magnetite or like air-borne magnetic particles from exhaust gases in steel, bearing and various other industries. In this paper, we make clear the performance of the magnetic filter in which the wire axis and the fluid flow are mutually parallel and the magnetic field perpendicular to them (Parallel stream type magnetic filter). The parallel stream type magnetic filter has been investigated by Uchiyama et al. and the collecting efficiency of the filter was calculated based on the particle trajectory model. In their model the fluid stream was uniform and had no velocity gradient. The laminar flow, however, in a narrow slit of the parallel stream type filter has the parabolic velocity distribution. Then we derive the equations for the magnetic, drag and inertia forces acting on a particle in the parabolic fluid stream. By solving these equations numerically, we can obtain the single-wire efficiency rather different from Uchiyama's. For practical estimation of the collecting efficiency of air-borne particles by weight, it is required to consider the effect of neighbouring wires and the particle size distribution on the single-wire efficiency. Nukiyama's formula is applied to represent the particle size distribution and we can obtain the equation of the collecting performance. The experimental results for ferromagnetic or paramagnetic air-borne particles show the good agreement with our theoretical solutions. With the theoretical and experimental analysis on the parallel stream type magnetic filter, it is found that high collecting efficiencies for fine magnetic particles can be achieved. Let us consider a concrete example. Suppose the stainless-steel wire is of 100μ diameter, and has a saturation magnetization 2000G. The background field is 3kOe and the air flows in the filter at a velocity of 2m/s. Let us suppose that the particles, say Fe_3O_4, have a diameter 0.8μ. The saturation magnetization of the particles is then 470G. We make clear that with the parallel stream type filter of 5% in packing density, 10cm in thickness and 1mm in width of the slits, the collecting efficiency is higher than 99% and the pressure drop is lower than 20mmAq. Throughout of the preceding experiment, the efficiency and the pressure drop are determined for clean filters. For practical purpose, however, the effect of particles build-up onto the wire, in other words, the performance after the filter has been operated for a certain length of time, is one of the most important properties to be examined. The authors are making an examination of the magnetic filter in which the wire axis, the fluid flow and the magnetic field are mutually perpendicular. A report on the details will follow.

View full abstract

The author reported the results examined about the effects of the shape on the performance of the multiple nozzle supersonic air ejectors in the previous paper. In the present paper, the experimental investigations of the effects of the expansion ratios of nozzles on the performances of the ejectors for small flow ratio and for medium flow ratio are described. The main conclusions are as follows. (1) The best performance can be gained in case that the driving jet through nozzle expands normally (or nearly normally). The values of the expansion ratios of nozzles for the multiple nozzle ejectors are same for the single nozzle ejectors, and they are as follows; for ejectors of type A with throat area ratio m=11.8: α=1.44 when P_0'=3atg, α=2.01 when P_0'=5atg, α=3.18 when P_0'=7atg, where α is the expansion ratio of nozzle, i.e. the area ratio of nozzle outlet to its throat and P_0' is the pressure of driving air before nozzle; for ejectors of type B with throat area ratio m=47.3: α=1.25 when P_0'=3atg, α=1.56 when P_0'=5atg, α=1.84 when P_0'=7atg. (2) In the range of large flow ratios, the multiple nozzle ejectors have better performances than the single nozzle ejectors. This fact can be accepted for all the expansion ratios of nozzles. (3) The jet noise is larger for the larger expansion ratios of nozzles. The effects of the expansion ratios of nozzles on the noise are much smaller than those of the employment of multiple nozzles. That is, the employment of multiple nozzles is greatly useful for reduction of noise.

View full abstract

The Water-Trickle solar collectors, developed by Dr. H.E. Thomason in the U.S., are said to be cheaper than the ordinary Flat-Plate collectors. But, due to the higher heat loss, caused by the mass transfer between the water and the glass, the collector efficiency of that type is somewhat lower than that of the flat-plate types, especially in the higher temperature range. So, we developed a new Water-Trickle collector in which the channels of the water passes are covered mechanically with the cover plates. As the results of the experiments, it is proved that the efficiency of the tested collector is improved greately, compared to the uncovered, and if these collectors are supplied at the cost cheaper by 20% to the ordinary flat-plate (black painted) collectors, these can be used widely for the low temperature applications, such as solar floor heating and solar heat-pump heating. And we also pointed out that the performance of the Water-Trickle collectors could be improved by either drawing off the moist air of the collector as the fresh, humidifying air of the rooms or applying the dual (water and air) collecting system.

View full abstract