High efficiency motors are demanded because of the viewpoint of environmental preservation. It is necessary to develop the technology of the energy conservation that can be achieved at low cost so that we may expand high efficiency motors onto the world. In this paper, the current status of the brushless DC motors and invertors to satisfy high efficiency, small size, high power and low cost is reviewed.
Micro-scale distributed power generation system, which means a micro-cogeneration system in almost cases, has been paid a great attention from a standpoint of saving fossil fuels' consumption and preventing global warming. Especially, polymer electrolyte fuel cell (PEFC) is considered the most promising power generation system for small scale commercial use and residential use. In the PEFC cogeneration system, small amount of waste heat at low temperature from a cell stack is almost used to produce hot water. Therefore, in the paper, we proposed a new heat utilization method of the waste heat for air conditioning. In the proposed home cogeneration system, absorption refrigerator is introduced in order to produce chilled water. Thermal performances of the proposed system have been analyzed by a computer simulation which was developed for the prediction both of power generation characteristics of PEFC and absorption refrigerator's behavior.
This paper aims to develop a hybrid system for snow melting and space cooling by using geothermal energy in order to improve the availability factor of the borehole heat exchanger. Based on field experiments, a feasibility evaluation of the system was performed. First, snow melting experiments using geothermal energy were performed and the comparatively good road surface situation was realized. The primary energy reduction rate over 70% was shown in comparison with the conventional snow melting system. Second, regarding a snow melting tank with the hot water piping, it was clarified that the snow melting was possible even in the low temperature water of approximately 9-10°C by using water sprinkling in the tank jointly. Finally, by supplying the space cooling and dehumidification panel with the cold through the borehole heat exchanger in summer, it was shown that the good cooling effect was obtained.
Ozone has the capability of sterilization and deodorization due to high oxidation power. It is also effective for the conservation of perishable foods and purification of water. However, ozone has a disadvantage, that is, conservation of ozone is difficult because it reacts to oxygen. Recently, ozone-contained ice is taken attention for the purpose of its conservation. The use of ozone-contained ice seems to keep food fresher when we conserve and transport perishable foods due to the effects of cooling and sterilization of ozone-contained ice. In the present study, we have developed an ozone-contained ice making machine employing pressurized air tight containers with commercially available size. And the performance evaluation of the system is also carried out. Furthermore, we investigated the sterilization effect of ozone-contained ice on conservation of fish. It was seen that ozone-contained ice is effective for sterilization of surface of fish.
Desiccant cooling processes can supply dry air by using lower temperature heat energy such as waste heat or solar heat. Especially, solar heat is useful heat source for the desiccant cooling since solar heat in summer tends to be surplus. This paper discusses the hourly cooling performance of the solar assisted desiccant cooling system, which consists of a desiccant wheel, a thermal wheel, two evaporative coolers, a cooling coil and flat plate solar water heater, assuming that the cooling system is applied to an office room of 250m3 in volume. The estimation indicated that the surface area needed to satisfy the dehumidifying performance in a sunny day was at least 30m2. Furthermore, surface area of 40m2 or larger provided a surplus dehumidifying performance causing a sensible cooling effect in evaporative cooler. Surface area of 30 m2 did not satisfy the dehumidifying performance required for high humidity condition, over 18.0g/kg(DA). The cooling demand of the cooling coil increased in such humidity condition due to the decrease in the sensible cooling effect of evaporative cooler. Auxiliary heater was required in a cloudy day since the temperature of water supplied from solar water heater of 40m2 did not reach sufficient level.
Performance analysis was made for the generator of the absorption refrigeration cycle using TFE/NMP as a working fluid. In this study the dynamic model was constructed. This model includes the heat and mass transfer characteristics in the generator and is able to predict the outlet concentration and the flow rate of the generated refrigerant vapor according to the change of the operating conditions of the absorption refrigeration cycle. The heat transfer in the generator was decided giving the heat transfer coefficient with temperature difference between the heat transfer wall of the generator and the solution. And the mass transfer was decided giving the over-all mass transfer coefficient between the solution bulk flow and the generated refrigerant bubbles. In this study the change of the concentration and the flow rate of the generated refrigerant vapor was mainly calculated when the strong solution flow rate, the generator wall temperature and the generation pressure were dynamically increased in incremental steps. And in starting and stopping the system, the effect of the generative heat transfer coefficient, over-all mass transfer coefficient and the strong solution flow rate were investigated.
This study focuses on the significant effect that a pressure difference across the orbiting thrust plate of a thrust-slide bearing has on the improved lubrication of the bearing in scroll compressor applications. A thrust slide-bearing model submerged in a refrigerant oil VG-56 was operated under pressurized conditions using R-22 as the pressurizing gas, where the pressure difference across the friction surface of the thrust bearing was adjusted from 0 to 1.0 MPa and the friction force and friction coefficient at the thrust slide-bearing were measured over a range of orbiting speeds. As a result, a significant improvement in lubrication at the thrust slide-bearing due to the pressure difference was addressed. Furthermore, a careful observation of wear state at the thrust slide-bearing addressed a significant formation of fluid wedge between the sliding surfaces due to axial loadings, which will definitely induce the addressed significant improvement in lubrication. In addition, the wedge formation was quantitatively addressed with FEM analysis of elastic deformation of the thrust plate, which was verified for its validity with measured strains on the thrust plate.
This study presents a theoretical development of excellent lubrication at the thrust slide-bearing of scroll compressors, caused by a wedge formation due to elastic deformation of the thrust plate at its periphery. In theoretical calculations, the average Reynolds equation by Patir & Cheng for rough sliding surfaces of the thrust slide-bearing was applied to analyze the fluid lubrication, while the solid contact theory by Greenwood & Williamson was applied to analyze the plastic and elastic contacts between the orbiting and fixed thrust plates. With the FEM-calculated wedge angle between the sliding surfaces, the oil film pressure, the solid contact force, the fluid frictional force and the solid shearing drag force were calculated to determine the resultant friction coefficient at the thrust slide-bearing. As a result, it was shown that the theoretical results have a good agreement with the lubrication test results, thus unveiling the essential contents of excellent fluid lubrication at the thrust slide-bearing, caused by the wedge formation due to large thrust loads.