In this study, the combined system of a solid-oxide fuel cell (SOFC) and a proton-exchange membrane fuel cell (PEFC) is developed. The proposed system consists of a SOFC-PEFC combined system and a photovoltaic system (PV) as the energy supply to a micro-grid. The exhaust heat of the SOFC is used for the steam reforming of the bio-ethanol gas with time shift utilization of the exhaust heat of the SOFC in optional time. The SOFC-PEFC combined system with the PV was introduced in a micro-grid of 30 residences in Sapporo, Japan. The operation plan of the system has three cases: without solar power, with 50% and with 100% of solar output power. Moreover, three types of system operation of using the SOFC independent operation, PEFC independent operation and SOFC-PEFC combined system are used to supply the demand side. A comparative study between the types of system operation is presented. The power generation efficiency is investigated for different load patterns: average load pattern, compressed load pattern and extended load pattern. This paper reported that the power generation efficiencies of the proposedsystem in consideration of these load patterns are 27% to 48%.

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The purpose of the present study is to clarify both the surface tension and the pipe diameter effects on two-phase flows in horizontal small diameter pipes. In the experiments, four-kinds of test liquids with different fluid properties were used together with 3, 5 and 9 mm i.d. test pipes. The flow parameters studied were flow pattern, bubble size, liquid film thickness, void fraction and pressure drop, etc. The flow patterns covered were bubbly, slug, and annular flows. From the measured data, the data of interfacial friction force per unit volume, F_i, was also obtained. By comparing data obtained in different pipe and test liquid combinations, the effects of the surface tension and the pipe diameter on the flow parameters have been clarified. In addition, new correlations of mean liquid film thickness and interfacial friction factor in annular flow have been derived with some dimensionless groups.

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An all-electric home using an electric storage heater with safety and cleaning is expanded. However, the general electric storage heater leads to an unpleasant room temperature and energy loss by the overs and shorts of the amount of heat radiation when the climate condition changes greatly. Consequently, the operation of the electric storage heater introduced into an all-electric home, a storage type electric water heater, and photovoltaics was planned using weather forecast information distributed by a communication line. The comfortable evaluation (the difference between a room-temperature target and a room-temperature result) when the proposed system was employed based on the operation planning, purchase electric energy, and capacity of photovoltaics was investigated. As a result, comfortable heating operation was realized by using weather forecast data; furthermore, it is expected that the purchase cost of the commercial power in daytime can be reduced by introducing photovoltaics. Moreover, when the capacity of the photovoltaics was increased, the surplus power was stored in the electric storage heater, but an extremely unpleasant room temperature was not shown in the investigation ranges of this paper. By obtaining weather information from the forecast of the day from an external service using a communication line, the heating system of the all-electric home with low energy loss and comfort temperature is realizable.

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In the case of a hypothetical failure of a residual heat removal (RHR) systems under mid-loop operation, vapor generated in a reactor core forms two-phase flow in a stagnant liquid and rises the water level in the core. The vapor flows into a steam generator through a hot leg, and condenses in the steam generator. Since the flow rate of vapor from the reactor core to the hot leg depends on the water level and the void fraction α in the reactor core, the reliable analysis of the RHR failure cannot be carried out without accurately estimating the void fraction in the reactor core. Although a number of studies on void fractions in two-phase flows in rod bundles have been carried out, there are few experimental data on void fractions in rod bundles under the stagnant condition. Void fractions in four by four rod bundles under the stagnant condition were measured for a wide range of gas volume fluxes to examine the validity of available void correlations. Flow patterns were visualized by using a high-speed video camera to examine the effects of flow pattern on the void fraction. As a result, the following conclusions were obtained: (1) Dependence of the void fraction on the gas volume flux J_G changed at J_G ≅ 1.5 m/s due to the flow pattern transition. (2) Murase's correlation agreed well with the void fraction in the two kinds of rod bundles having different dimensions under the stagnant condition.

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The bent pipe wall thinning phenomenon has been often found at the elbow of pipelines in the power engineering industry. Liquid droplet impingement (LDI) erosion could be regarded to be one of the major causes of unexpected troubles occasionally occurred in the inner bent pipe surface. In this paper, three-dimensional numerical simulations are conducted for a bent pipe. Typically the pipe diameter is 170mm and the bending angle is 90 degree, the mass flow rate of droplet is 4.5×10^-3 kg/s with the velocity of 280m/s at the entry. The calculations employ a two-phase flow model. A computational fluid dynamic tool has been adopted by using one-way and two-way fluid-droplet coupled system in high Reynolds number regions. This computational fluid model is built up by incompressible Reynolds averaged Navier-Stokes equations using different turbulent flow computational models and the SIMPLE algorithm, and the numerical droplet model adopts the Lagrangian approach. The momentum transfers between droplet and carrier fluid are calculated by using two different fluid-droplet coupled methods. The interactional force between carrier and droplet are taken into account by momentum transfer in Eulerian-Lagrangian approaches. Based on the carrier streamlines and droplet trajectories, the two-way calculation using the interactional momentum transfer calculations could be a more appropriate model to simulate the bent pipe wall thinning phenomena, the effects of droplet size are also demonstrated numerically. Finally, it is shown that turbulence models are not sensitive to the involved droplets.

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The standard solid oxide fuel cell (SOFC) performance is related to its chemical reaction, electrical resistance, gas diffusion polarization, and operating temperature. We start this paper by discussing the performance simulation from our research. A tubular-type SOFC has an axial direction distribution of the gas concentration, and its electrodes and electrolyte have an electric current density distribution. In addition, these distributions are important to the performance simulation. The analysis results were in good agreement with the experimental data, and this indicates that these are useful for a high performance SOFC design. The last part of this paper is about temperature distribution calculation for the SOFCs sub-module. Since performance change is by temperature, numerical thermal and fluid analysis is really important for SOFC module design. In this study, we discuss numerical analysis in SOFC module, considering the electrochemical /reforming reaction. The analysis results agreed well with the experimental data, thus demonstrating the effectiveness of the prediction model.

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Pressurized solid oxide fuel cells (SOFCs) using a gas turbine for the bottoming cycle convert energy very efficiently. The performance of a tubular SOFC made by a plasma spray coating method was measured at levels of pressure between 0.1 and 0.59 MPa. The cell voltage increased with the operating pressure. Moreover, it was determined that polarization decreased under pressurization, using the current interruption. Anode performance was also measured with a reference electrode. The estimated concentration overvoltage from the measurement of permeability was used to estimate the activation overvoltage of the anode. The anode activation overvoltage was affected by the partial pressure of H₂O instead than that of H₂.

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