As part of an investigation to evaluate the performance of Advanced Submergible Aerators installed in Hiyoshi Dam Reservoir (Kyoto), a field experiment was conducted on a destruction of a thermocline formed in August and October, 2012. At first, water temperature distribution near one aerator was observed in a vertical section of 10m-depth and 90m-disrance, by moving an observation device automatically from the aerator to a bank of the reservoir. Secondly, water temperature di stribution between two identical aerators 275m apart from each other was observed with five observation equipments fixed at regular intervals between two aerators. From these data, a horizontal intrusion of the entrained water, having an important role to destruct the thermocline, was visualized and its fundamental characteristics were clarified.

View full abstract

In this study, one box multimedia model to analyze the behavior of mercury and to assess the environmental risk was constructed and applied in Biwa lake and Yodo river basin. The amount of mercury emissions was estimated using PRTR data. The historical mercury emissions were estimated from the mercury usage data. The transboundary transport of mercury was also considered. The calculated value was compared with the measured values. The calculated value are well accorded with the measured value in every media. It was found that the multimedia model could reasonably predict mercury concentration in the atmosphere, solid, water, and also sediment.

View full abstract

Planktonic predator-prey interactions in homogeneous isotropic turbulence are studied by a series of numerical experiments and the effects on the ingestion rate of turbulence mixing and predator's ability are closely investigated. Particular attention is paid to the question how the simulation results are affected by taking account of the relative distance between predator and prey in deciding whether the prey have been consumed during the prey-predator contact. The numerical experiment shows that the optimal foraging strategy depends on the range of predator's detection of prey.

View full abstract

Here we present field experiment results and its examination to evaluate the performance of air lifting towers installed in Yamaguci Regulating Reservoir in Fukuoka. In the experiment, 4 air lifting towers with different size combination of diameter and length were used, and water flow velocity was measured at their bottom intakes and around water surface where their bubble plum es emitted from outlet rise up. From these data, quantity of water flowing to the bottom intakes and rising up to reservoir s urface was estimated. Finally, their data were compared with ones obtained by the prediction formula Asaeda et al. indicated, and it was found that they generally coincide with each other..

View full abstract

We have developed the successful technique to improve the temperature exchange efficiency at the heat exchange region by absorbing thermal radiation energy emitting from CO_2 1n the combustion exhaust gas. The electro-magnetic radiant materials as the absorption materials are applied at the inner surface of combustion chamber (Spectrum Heat Absorption Technique). .In order to check how robust our results are, the verification tests on the temperature exchange efficiency are carried out by employing the wick diffusion flames and fire tube and flue boilers. The fuels studied are kerosene, ethanoi, and methanol for wick diffusion flames and LNG for fire tube and flue boilers (capacity:6ton/h). From these results obtained from the verification test we may predict that the spectrum heat absorption technique is very useful and effective to achieve the high energy saving through the improvement of thermal efficiency on fossil fuel combustion.

View full abstract

A novel rotational internal combustion engine has been investigated in this study. No eccentric rotational component is used in this engine, resulting in vibration-free operation. The engine consists of rotor casing and two types of rotor; cycloid rotor and trochoid rotor. The shape of the cycloid rotor is characterized by epicycloid surface, and the trochoid rotor also superior-epitrochoid surface. In this paper, first, the typical configuration was shown. Next, a procedure for designing the rotors were described in detail. Furthermore the design drawing and appearance of the prototype engine were given. Its cyclic behavior, the time variations of the chamber volume and the estimated pressure were also indicated. Additionally the flame behavior in the working volume of the prototype engine driven in motoring condition, was presented. Finally the compactness and S/V ratio of the engine was investigated.

View full abstract

Recently, for development of gas cooking stoves used in kitchens, lower thermal strain for kitchen workers has been required. A novel evaluation system of the thermal environment caused by the gas cooking stove under development is proposed in this paper. The proposed system consists of two types of meas uring system. The first system "Mock-up", which has the same heat-transfer structure as that of human body, measures the typical human skin temperature of kitchen workers who have been heat-radiated with the stove. The another system is for a wide-area visualization of behaviors of the hot-gas from the stoveand the boiling pot on it.

View full abstract

In recent years, low-emission vehicles come into wide use. In this study, we estimated the influence of the spread of low-emission vehicles on atmospheric environment in Osaka area. We executed numerical simulations of photochemical air pollution by using WRF/Chem model under the typical mid-summer condition, and estimated the reduction amount of photochemical ozone concentration when all passenger cars were replaced by electric cars and all the power was generated by fossil-fuel power stations. The results show that the daily maximum concentration of ozone decreases in the most part of Osaka area, and the highly polluted area (above 100 ppb) is reduced by25 % compared with current case. However, ozone concentration was not so much reduced, i.e. only 4 ppb at maximum.

View full abstract

The regulations governing marine diesel engine NO_x emission in the International Maritime Organization (IMO) emission standards have become more stringent. Because it is difficult to fulfill these requirements by means of combustion improvement alone, effective aftertreatment technology is needed to achieve efficient NO_x reduction. In this paper, our recent experimental achievements on plasma emission control for marine diesel engines are presented based on our recent papers. Laboratory -scale and pilot-scale experiments are successfully carried out in our studies.

View full abstract

Medical instruments are generally sterilized by high pressure steam, ethylene oxide gas (EOG), or gamma radiation. However, high pressure steam needs higher than 121 ℃ and 2 atm, the EOG has a toxic consequence and takes long time for an operation. In addition, the cost of gamma radiation is high. Therefore we focus on sterilization using plasma. Plasma sterilization can sterilize a wide range of materials jn ambient temperature. In this study, we develop the sterilization device by air plasma using circulating flow, and evaluate the efficiency of the device by using biological indicators.

View full abstract

As the regulations governing diesel engine emissions become more stringent, an effective aftertreatment technology is thu s needed for, particularly with regard to particulate matter. Although the use of ceramic diesel particulate filters (DPF) is a leading technology in automobiles, it still presents a problem in terms of soot removal or regeneration for marine diesel engine operated with marine diesel oil including the sulfur. In the present study, to establish a nonthermal plasma DPF regeneration method for marine diesel engines, pilot-scale experiments are carried out. It is confirmed that the pressure difference of a DPF, which is a referential parameter of DPF regeneration, decreased only when the plasma is turned on. It is revealed that the DPF regeneration depends on exhaust gas temperature and regeneration at 270℃ has a better performance than that at 220℃. The required plasma energy is approximately 5% of the generated power of the marine engine.

View full abstract

Atmospheric mercury emissions from coal combustion and waste incineration processes have been drawing attention as global pollutant. It has been reported that wet desulfurization process and/or absorbing bed of activated carbon, which are generally installed in domestic coal fired power plants, can control mercury emissions. However, considering the growing diversity of fuels including waste products and the overseas market development, a low-cost dry process for mercury removal from stack gas needs to be developed in near future. Objective in this study is to utilize particle materials derived from waste products to capture gaseous mercury. Mercury absorption experiments have bee n conducted using some mineral particles. As a result, calcined paper sludge showed the high performance for mercury absorption.

View full abstract

Diesel particulate matter exhausted from marine diesel engine during the combustion process cause a various human health and environment impacts. Many methods were applied to control mass concentration of particulate matter from diese l exhaust gas. Many studies of electrostatic precipitator (ESP) were reported to collect low resistive particles generated from diesel engine. This research has been developed a new hole type electrostatic precipitator (ESP) to minimi ze re-entrainment. The ionic wind was used effectively and PM was guided to the hole installed in the PM-collection electrode for re-entrainment phenomenon control. Most particle are transported into the hole by pressure difference and ionic wind. In this study, it is intended to clarify the position of the optimum hole diameter and the distance between the electrodes to PM collection efficiency.

View full abstract

In recent years, pandemic outbreak due to a mutation of virus is paid close attention as a big problem that may collapse social order. Generally, the methods for preventing and healing disease by the virus depend on medical agents s uch as the vaccine or antiviral drug. However, the vaccine and antiviral drug could be poorly supplied when the pandemic occurred. Plasma has been proven to be capable of sterilizing bacteria and expected to inactivate the virus. In this study, we focused on the effect of chemical species generated by plasma flow on influenza viruses.

View full abstract

Nano-sized organic aerosols, nanoparticles (d_p < 50 nm), in the atmosphere have attracted a lot of attention in recent years because of adverse effects on human health. A new system combining a soft plasma ionization (SPI) source with a time-of-flight mass spectrometer (TOFMS) has been successfully developed and applied to direct and on-line analysis of smoke generated during combustion. The mass spectra of smoke were obtained in conjunction with the effects of gas species (air, Ar and He), pressure (1600-2600 Pa) and current (10-130 mA) of the SPI discharge. To investigate the ionization mechanism of the SPI, we also have studied spontaneous emission spectra from the SPI source. Considering the results from mass and emission s pectral data, we suppose an ionization mechanism of the SPI which can efficiently produce excitation ofN_2 in the presence o f the noble gas, leading to promote ionization of sample.

View full abstract

Non-catalytic hydrogen production from ammonia gas using a pulsed atmospheric plasma have been developed to solve the problems of hydrogen transportation and storages. Ammonia is easily decomposed by electron energy generated by plasma, which is converted to molecular hydrogen and nitrogen by global reaction; NH_3 + e → 0.5 N_2 + 1.5 H_2. A hydrogen yield attained 100% at an applied voltage of 15 kV and an ammonia flow rate of 0.2 L/min. T o improve the energy efficiency of hydrogen production, a plasma reactor with a hydrogen separator was proposed. As the hydrogen separator was inhibited the reverse reaction for ammonia formation (N + 3H→NH_3), the hydrogen yield attained 100% at an applied voltage of9kV and an ammonia flow rate of0.8L/min..

View full abstract

Tar decomposition techniques are desired to prevent blockage troubles in biomass gasification processes. In this study, various kind of catalysts were examined to improve the performance of tar decomposition at low oxygen atmosphere. It found that catalyst of BaZrO_3-based Co or catalyst of BaZrO_3-based Mn including Ni had strongly activity for tar decomposition and syngas generation. It also found that these catalysts kept the activity for long run time.

View full abstract

NO_x emitted from a stationary diesel engine generator was treated with a hybrid system comprising NO_x reduction by nonthermal plasma (NTP) and NO_x adsorption-desorption cycle. Adsorption-desorption system produces highly concentrated NO_x, which is effectively reduced by NTP treatment. Improved treatment performance and efficiency are achieved by re-injecting the NTP-treated gas mixture into the engine intake. In this study, an oxidation catalyst was employed to accelerate the system performance. It greatly enhanced the adsorption by converting NO to NO_2. The detailed analysis is reported at the presentation.

View full abstract

Dimethyl ether (DME) is a clean and economical alternative fuel which can be produced from various resources such as natural gas, coal, biomass through synthesis gas. Storage and transportation of DME is easy because DME has similar properties with liquefied petroleum gas(LPG). DME is already produced and utilized as LPG alternate for domestic and industrial use in China. In this study, to operate a micro gas engine by supplying a mixture fuel of butane and DME, fuel consumption and exhaust gases (NO,CO) were measured. From the experimental results, with an increase in the mixing ratio of DME, the percentage of CO was reduced, but the percentage of NO increased. Particulate matter (PM) generation was not observed either.

View full abstract

To broaden and lower the temperature window of the selective non catalytic reduction (SNCR) of nitric oxide (NO), the use of activated ammonia as the reduction agant was examined. An intermittent dielectric barrier dischalge (DBD) was employed to generate activated ammonia from molecular ammonia. Chemical composition was clear by gas analysis at exit of the DBD reactor, it found that the main species of the activate ammonia were H_2 and N_2. By experiments and chemical kinetics simulation, it was clear that H_2 was strongly contributed to enlargement of temperature window ofDeNOx.

View full abstract

In order to manage and maintain a hygienic indoor environment, it is necessary to estimate concentrations of contaminants such as airborne particles and disease agents. For these estimations of the contamination, a data assimilation method was used with data previously measured. In this study, the Variational Continuous Assimilation method was applied to estimate indoor contamination sources. For an objective room which has neither circulation of flow nor temperature distribution, VCA method was validated. However, for an objective room has circulation and temperature distribution, the validity was seemed to be limited.

View full abstract

By eutrophication of lake or marsh, a lot of blue-green algae increase explosively. Ultra-high pressure underwater shock waves were applied to treatment those algae. We used a large-sized apparatus for an experiment. The imploding detonation of propane-oxygen mixture was used to generate the underwater shock waves in underwater shock tube having inner diameter of 48.9 mm. We investigated the imploding detonation wave in approximately cone shaped combustion chamber having maximum inner diameter of 230mm and generated underwater shock waves of about 100 MPa. And we compared this result with earlier experimental result of a small-sized apparatus. We obtained same cases that the number of cells decreased about six digits from treatment before, and it was suggested that duration of underwater shock wave had an influence on algae.

View full abstract

Membrane bioreactor employs air diffusion to clean the membrane surface with shear stress, and fluid velocity of two phase flow for continuously filtrating operation. Therefore, the optimization of air diffusion is important for the membrane surface cleaning. The group studied the phenomena on two phase flow in flow channels between the flat sheet membrane panels using computational fluid dynamics, and experimental methods. Based on the study, an optimized aeration diffusing structure is reported in this paper.

View full abstract

This research on reduction of membrane scouring aeration demand in membrane bioreactor was conducted using experimental fluid dynamics (EFD) and computational fluid dynamics (CFD). We evaluated the effect on motion ofPEG gel carrier in flow channel between flat membrane sheets, and confirmed that the motion of the carriers increase scouring perf ormance. In this research, analysis on the fluid flow field with CFD shows that uniform distributions of fluid vel ocity and its gradient are formed in the flow channels over all. Finally, we evaluated the reduction of scouring ae ration in the integrated Membrane Bioreactor applying carriers at the bench scale setup. The aeration demand is decreased by 50% with carriers in the evaluation test.

View full abstract

Gas-liquid plasma flow has received a great deal of attention because it is easy to make a synergistic effect of chemical reactions in gas phase and gas-liquid interface. As biological applications generally require low temperature and low heat transport, we have developed wire-water discharge system and studied characteristics of thermal flow and chemical transport. We focused on temperature rise, pH, conductivity, and concentrations of ozone and nitrogen dioxide.

View full abstract

Ultra-high pressure underwater shock waves ware applied to sterilized microbe. The imploding detonation of a propane-oxygen mixture was generated ultra-high pressure underwater shock waves. We investigated the imploding detonation using an experimental apparatus of sterilization with precombustion chamber having a maximum diameter of 230mm and a sample holder having inner volume of 7L. The experimental results show that the maximum pressure at the exits of sample holder was 600 times higher than the initial gas pressure and we found that the underwater shock waves have stably 100MPa. And we could sterilize Micro-cystis and Chlollera using by this experimental apparatus of sterilization.

View full abstract

We have developed a new technique that utilized ozonation under an acid condition, for treating dairy wastewater containing milk. The distinguished mechanism of this treatment is that the pollutants in the wastewater were solidified in a short period and that the wastewater quality was rapidly improved. In this condition, the energy consumption per unit mass of the removed pollutant was small, and the energy efficiency of this technique was higher than that of an advanced oxidation process or flotation technique. The ozone-bubble behavior in the wastewater was different from that in clean water. In the wastewater, the ozone-bubbles did not coalesce with each other, and the bubble velocity decreased. Hence, the change of the bubble behavior in wastewater af fected the solidification of pollutant and the recovery efficiency.

View full abstract

The majority of the living body is composed of water and the mechanism has not been clarified enough though water bears the key role from the viewpoint of the living body maintenance. The influence that these water exerts on the living body even when the difference is not admitted in a conventional water-quality test might be different. The method for the evaluation of the characteristic of the water that was not able to be identified in the present study by conventional water analyses is developed. We analyzed it by hitting the focus to the side of structure of water, and measuring to the growth of the near-infrared radiation spectrometry, the kinematic viscosity, hardness, and the plant and observing it. It was able to be shown that as a result of the experimental research, there was a difference also between the water that had been thought to be the same up to now. We presumed that the state of the congregation of the water molecule (structure) was related as the cause of inventing the difference.

View full abstract

We treated microorganisms using ultra high pressure underwater shock wave. In addition, we have observed with a scanning electron microscope and a microscope. Body surface of Brachionus plicatilis was destroyed and the contents spilled. The body surface of Chlorella were destroyed significantly. Although there was no big crack in the body surface as a result of carrying out the shock treatment of Microcystis, it turned out that the pigment is missing. These results have suggested that the damage of the living body by the shock wave is depende nt on the hardness of the body surface. That is, in the case of a living body with the hard body surface, the shock wave reflects at the bo dy surface, but in being a soft body surface, it penetrates the inside of the body.

View full abstract

We conducted a two-dimensional numerical simulation of ferromagnetic floc motion (coagulated particles containing ferromagnetic particles) in a magnetic field and a flow field to analyze the effect of physical parameters( number of magnets, floc diameter, volume content rate of magnetic particles, mean value of fluid velocity, and kinetic viscosity) on magnetic separation performance. In the present study, we used magnetic fields applied by permanent neodymium magnets. The calculation results show that the logarithm of the residual rate of the flocs is approximately proportional to the number of applied magnets and the residual rate is approximately expressed as a function with parameters stated above in this study.

View full abstract

This paper aims at designing a simplified method to estimate the potentials of photovoltaic systems and solar water heaters in municipal scale based on public statistics. The method consists of three st eps: calculating energy demand in households, investigating potentials of the solar energy technologies and estimating the effect on primary energy reduction. This study provides functions to calculate energy consumption by household types. It was verified by the comparison with statistic data of electricity and gas consumption. Because roof areas are not available in statistics, the study found parameters to estimate roof areas from building areas. The results show that the solar energy equipment reduces energy consumption by 30-60% in detached houses in Tokyo, and that the payback year is expected less than 20 years.

View full abstract

In order to prevent the global warming, t he emission of greenhouse gases must be reduced. In the public transportation, an electric bus is suitable for realizing this. H owever, electric vehicles have been limited to political uses in public corporations due to the constraint of the battery weight. To address this issue, the electric bus system charged quickly at every bus stop using electric power generated from renewable energy sources has been proposed. One of the characteristics is light weight of the storage device. A simulator calculating the consumption energy between bus stops is required for utilizing this advantage. In this study, the simulator for full size bus is developed by extrapolating the data of the EV minivan, and the capacity of the storage device mounted on the bus is designed on t rial.

View full abstract

The mega solar plant consisting of a flat solar cell module requires a large land. And power generation is changed with time as flat solar cell has a high directivity. The purpose of this study is to reduce the directivity (effect on the output of the solar position) and compactification (decrease installation area) of solar cell module. The point of view is ramification structure of plant. The plant is getting the energy by photosynthesis. It means that the plant evolves to receive light efficiently. From this, it is thought that the plant is the form which was excellent in a compact and light density. Therefore, if leaf of the plant is replaced by a solar cell, excellent light density can be obtained. The plant have branch structure to get light. To express branch structure, L-system and GA are used in numerical analysis, The optimal solution of the plant form and light density were obtained. Result of analysis, the solar cell module which simulated a plant form is confirmed that light density increased in comparison with the flat solar cell module.

View full abstract

The development of a system containing renewable energy for local production and local consumption is a very important research issue, 丘om environmental and safety points of view. As an example of this type of research, in order to develop a system for local production and I ocal consumption, a study about the utilization of large amounts 'of renewable energy was performed at Kitami City, Hokkaido. First of all, the exploitable renewable energy sources in the city are found to be tidal, wind and solar generations. However, for the maχimum utilization of these resources, energy storage systems or controllable power generators are necessary. In orderto supply the whole Kitami City's power demand, a system containing wind, tidal and solar power generation together with sodium-sulfur (NaS) batteries is developed and presented in this work. Because Kitami city has the particularity that is located ina very cold region and that the demand during winter is big and that of summer small, this paper proposes a seasonal energyshifting method, 丘om summer to winter, taking into account economic and environmental aspects. Results show that, compared toconventional systems, environmental impact is reduced to about 1/6, but the total cost increases about 6 times.

View full abstract

The objective of this research is to improve efficiency of conventional evacuated solar collector by simulation. To achieve this, the upper half of vacuum tube consists of Non-imaging Fresnel lens. Non-imaging Fresnel lens consists of many prisms and has acceptable half-angle. The vacuum tube is designed by changing parameters, for example, a position of heat collector, the radius o f the vacuum tube and the number of prisms. The optical efficiency is calculated by ray tracing. As a result, parameters, which affect optical efficiency greatly, are number of prisms and the distance between heat collector and center of vacuum tube. The greatest optical concentration ratio was about 3.0 when parameters of vacuum tube changed.

View full abstract

These days, there are desire to use renewable energy. One of the renewable energy is solar energy. Solar energy is almost no impact on environment. However, since solar irradiation depends on climates, it is unstable. For this reason, we should grasp detailed characteristics and finally develop efficient driving control plan for the solar thermal energy systems. We focus on two types of the solar collectors, flat plate type solar collector and evacuated type solar collector. High precision mathematical models are developed to grasp the characteristics of these two solar collectors. With these model s, we first simulate them. And then we carry out experiment to investigate the validity of the models. As a result, we grasped the characteristics of two type solar collectors, and confirmed the validity of the mathematical models we have constructed.

View full abstract

Concerning a hot water supply system, about 3.5 millions units of electrical heat-pump system have been used in Japan as of May 2013. Those systems effectively utilize surplus electricity at very early morning in Japan, while solar thermal panel constantly increases in the world. Although the performance of the heat pump system would be very high, it isn't more superior being than the simple solar thermal panel from a viewpoint of energy consumption. The present study has started to get fundamental information how much electricity can be saved through a year at Yokohama area when we use a decompression solar collector as an evaporator of heat pump system. We have constructed a testing device, which consists of four solar collectors being about 7.8 m^2 and a compressor of the heat pump system with the nominal maximum power consumption of 1.6 kW. We got preliminary experimental data by operating in winter season of January 2013. This paper introduces the device and the experimental results.

View full abstract

Simulation is carried out to find the temperature distributions of working chamber and the temperature fluctuation at the casing wall for the basic study on the scale adhesion problem and the thermal deformation of the screw expander. Furthermore,the mean temperature of the circumferential and the axial direction were calculated to clarify the temperature characteristics. Influence of internal leakage in the temperature distribution of the working chamber is remarkable after the second half of the expansion process .Mean temperatu re and temperature fluctuations of the casing wall including range mentioned above will be appreciated the influence of leakage. Mean temperature distribution in the axial direction causes a large non-uniformity at the supply port side and the circumferential temperature distribution causing large non-uniformity close to the admission end.

View full abstract

Atmospheric pressure low temperature plasma jet has been applied for enhancement of bio-mass combustion. The atmospheric pressure plasma was generated by a coaxial dielectric barrier discharge with a stimulated bio-mass gas consisted of methane 0.3 ?/min and nitrogen 0.7 ?/min. The dielectric barrier discharge was driven by a sinusoidal high voltage with 8 kV and 17 kHz. A filament-type discharge was observed between a high voltage electrode and grounded one. A consumed power for the plasma generation was estimated by V-Q Lissajous method. The V-Q Lissajous method indicated that the electrical power consumed in the atmospheric pressure plasma was 0.2 W.

View full abstract

In recent years, use of renewable energy has been required more by accident of nuclear power plant in the Great East Japan Earthquake and the depletion of natural resources. In this study, we focus on heat utilization that is efficient than electronic power use of woody biomass, and consider the promotion of bio-oil as an alternative fuel use in facilities with many heavy oil consumption in the industrial sector. In addition, environmental performance and economic evaluation of both the demonstration and simulation of introducing bio-oil in the facility a lot of heavy oil consumption in Saitama Prefecture is shown. Then the effectiveness of the Bio-oil production and utilization system is proposed.

View full abstract

The purpose of this study is to establish the basic technology to achieve CO_2 reduction and hydrogen production by using exhaust gas, waste steam, and sawdust. We used sawdust with mean particle diameter of 10,100 and 600μm, and applied shock heating technique by the shock wave driven by high pressure helium. The experimental apparatus is a standard shock tube having inner diameter of 100 mm. We found that hydrogen concentration increases gradually with increase of the rate of small sawdust and increase of temperature. The highest hydrogen concentration was about 60%. The shock heating temperature for acquiring the value of high hydrogen concentration was about 1360K.

View full abstract

Flow and heat transfer characteristics of heat transfer fluid in vertical coaxial double tube type ground heat exchanger were investigated numerically. Heat transfer characteristics are influenced with the flow directions which are center-in and annulus-in. Ground temperature profile also affects on the heat transfer characteristics. In the case of constant ground temperature, heat transfer rate of the center-in condition was greater than the annulus-in condition. On the other hand, the heat transfer rate becomes lower for the condition of variable ground temperature profile of which the temperature of surface is lower than that of deep area. This degradation was more remarkable for the center-in condition and the difference between the flow directions became smaller. Detail of the heat transfer characteristic is also discussed.

View full abstract

We have now designed a new α^+-type engine that is considered about higher buffer pressure and higher engine speed. Note that the α^+-type mechanism is suitable for low-temperature-difference Stirling engines and the α^+-type engine has a mechanism that is possible to use a regenerator with a suff iciently large area without large load applied to the crankshaft. The α^+-type engine is most effectively applied to power generation using combined solar heat and combustion heat from a wood biomass because the engine can be driven by indirect heating using 300 degC thermal oils. We report the plan and design of new 10 kW class engine that reduces size of half, increases thermal efficiency from 12% to 20%.

View full abstract

Since the Great East Japan Earthquake occurred in 2011, power load leveling has become a major and urgent issue in Japan. Thus, in order to promote the issue, use of ice slurry formed during the midnight for a cold storage of foods at a daytime attracts attention. A harvest method where ice growing on a cooling solid surface is scraped by a scraper is a typical formation method of ice slurry. However, ice structure strongly affects the scraping force. So, to control ice structure, the correlation among the controlled initial crystal orientation and ice structure has been investigated. In this paper, based on the correlation and removal behavior of ice, a possibility of control of the scraping force is investigated.

View full abstract

In off-line heat transport systems, erythritol is occasionally used as heat storage materials.Then, our purpose is to simulate numerically heat response of heat storage tank using erythritol. In this paper, one-dimensional unsteady heat conduction experiment for erythritol was conducted. As a result, in melting process, simulation results are in good agreement with experimental data. However, in unsteady freezing process, they are not in good agreement.

View full abstract

Ammonia-water absorption refrigeration cycle converts thermal energy input into concentration difference of the refrigerant in solutions, then produces cooling. In the proposed system, refrigerant weak solution and strong solution are separately stored in tanks, which works as heat storage. This study investigated the feasibility of solution storage for thermal storage by dynamical simulation and examined the actual performance of heat release process experimentally. When separated refrigerant and weak solution were put into the evaporator and the absorber respectively cooling effect was observed to have almost steady output. It was also found that the cooling effect clearly depended on the mass flow rate of the refrigerant, which suggests that the heat release process is dominated by mass transfer, not heat transfer. The results reveal that solution storage functions as thermal storage definitely.

View full abstract

To achieve efficient air conditioning of data centres, we constructed a spot cooling-type carbon dioxide heat transportation system for servers on the basis of typical data centre air-conditioning techniques. In previous studies, we investigted the operational characteristics of forced and natural circulation methods under the condition of two-phase flow between server racks, with carbon dioxide as the working fluid. In this paper, we focused on a sudden unsteady variation in variables such as temperature and flow rate that may cause heat transportation in this system to become unstable. Here we construct a mathematical model and investigate the transient operational characteristics of heat transportation with two-phase flow in the unsteady state through simulations and experiments. Factors such as the server room temperature and cooling water temperature were considered as key variables that influence the heat transfer characteristics of the condenser and evaporator. The results showed that the experimental and simulated effects of air temperature and cooling water temperature were almost consistent. We also clarified the transient characteristics of the heat transportation system with carbon dioxide as the working fluid.

View full abstract

Utilization of waste heat is effective ways to reduce primary fuel consumption. Currently, low temperature waste heat around 130 ℃ is hardly used. Absorption cycle is worked by low temperature waste heat and it generates chilled heat. But heat supply area is far from the demand area. Therefore, it is required to transport thermal energy efficiently. Solution Transportation Absorption cycle (STA) is one of the studied heat transportation technology. STA is considered as realizable technology. But There is no data of measurement to know STA behavior. The objective of this study is to measure STA behavior. Experimental condition is 0m ・ 100m ・ 200m solution transportation. As a result of the experiment, STA of COP higher than normal cycle but inner condition is same as STA and normal cycle.

View full abstract

The objective of this study is to investigate the contribution of distributed energy system when electricity and gas utilities stop operation due to disasters. The distributed energy system consists of gas engine, solar energy technologies and energy storage, which is installed in apartment building. Optimal combination of the technologies was derived by minimizing total system cost under the constraint of energy sustained days for which the distributed energy system keeps electricity and hot water supplies independently. The results indicate that gas engine has priority to be selected and gas storage tank for emergency has an important role. It was found that initial cost increases to keep energy supply in winter due to fuel shortage. The way of reducing fuel consumption is to enhance thermal insulation of building. It was found that enhancing thermal insulation has effect to reduce energy storage as battery which is required for long energy sustained days more than six days.

View full abstract