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[en] Commercial buildings are generally cooling-dominated and therefore reject more heat to a vertical ground heat exchanger(GHE) than they extract over the annual cycle. Shallow ponds can provide a costeffective means to balance the thermal loads to the ground and to reduce the length of GHE. The objective of this work has been to develop a design tool for surface water heat exchanger(SWHE) submerged in shallow pond. This paper presents the analysis results of the impact of design parameters on the length of SWHE and its application effect on geothermal heat pump(GHP) system using vertical GHE. In order to analysis, We applied method on designing the length of SWHE. Analysis results show that the required pipe length of SWHE was decreased with the increase of approach temperature difference and with the decrease of pipe wall thickness. In addition, when the SWHE was applied to the GHP system, the temperature of vertical GHE was more stable than that of standalone GHE system.
[en] The response spectrum method is widely used to determine the seismic responses of components, equipment, and piping systems in nuclear power plants. However, in case of multiply supported components, the effect of the relative displacement between supports should be considered. However, owing to the nature of response spectra, the phase difference between supports is lost. To overcome this, many investigations have been conducted, but conflicts still remain. Thus, in this study, a method to express relative displacement numerically between two supports is proposed and its results are compared with those of conventional methods.
[en] To decrease the N-16 radioactivity, a decay tank is installed at the reactor outlet pipes in PCS (Primary Cooling System) for research reactors. The decay tank represents a significant portion of building due to own huge volume, thus efficient and elaborate design is required. The decay tank consists of circular cylinder body, two elliptical heads, perforated plates, and flow guides. The perforated plate makes evenly distributed flow using plate holes with decreased flow velocity. A numerical method is utilized to analyze the flow features and calculate the residence time inside the tanks. To obtain more accurate residence time, available numerical methods, such as streamline, massless particle, and user-defined scalar, are used and compared.
[en] One of the important factors to consider when designing long-distance natural gas high-pressure pipeline in arctic environments is the establishment of pipeline fracture control measures. The methods used for prediction of ductile fracture propagation of gas pipeline are simple numerical solution, Battelle two curve method, and full scale pipe burst test. In this paper, we investigate the requirements of pipe material applied to the arctic pipeline in Russia, and compare the pipeline design application cases with the three methods of setting the required value of pipeline material fracture toughness. It is considered appropriate to apply the BTC method incorporating the correction factor.
[en] Geothermal heat pump (GHP) systems have been proved to be one of the most efficient systems for heating and cooling in buildings. However, an optimal energy performance depends on a good control of the system components, including heat pumps and circulation pumps, which affect to the total energy consumption of system. This paper presents the simulation results of the heat pump performance for two different control schemes, i.e. constant setting temperature (Control-A) and variable setting temperatures (Control-B) in buffer tank. A dynamic simulation tool, TRNSYS 17, was used to model the entire system and to assess the performance of the system. Simulation results show that the Control-B, which controls the temperature in buffer tank with outdoor air temperature, is a effective way to reduce the energy consumptions in heat pump (7.7%) and circulation pump (7.5%).
[en] Fusion technology is attracting attention as the ultimate new source of energy based on the abundance of its fuels and the social and environmental acceptability. The Korean fusion demonstration tokamak reactor (K-DEMO), a facility for the demonstration of scientific and engineering feasibility, is currently in the pre-conceptual design phase. A breeding blanket, which is essential in K-DEMO tokamak, is an important mechanical and functional component for both tritium breeding and neutron multiplying. However it must be radio-activated due to the neutron irradiation, and thus accompany decay heat generation during their maintenance. A component of reduced activation ferritic martensitic (RAFM) steel layer and tungsten first wall accompanies significant decay heats by tens of kilowatts after the plasma shutdown. We evaluate their radio-activated characteristics under the fusion neutron irradiation and demonstrate that thermal managements should be taken into account in the light of heat transfer aspects of cooling.
[en] KOLAS (KOrea Laboratory Accreditation Scheme) belongs to APLAC (Asia Pacific Laboratory Accreditation Cooperation). KOLAS manages the accreditation scheme for measurement traceability to SI units. As per June 2016, there are 22 KOLAS laboratories for liquid flow metering. Among them, 12 laboratories participated in the proficiency test (PM2015-08) for water flow metering, organized by KASTO (Korea Association of Standards and Testing Organizations). This proficiency test was performed with three kinds of flow ranges (3.6 m3/h ~ 12 m3/h, 40 m3/h ~ 80 m3/h, 40 m3/h ~ 200 m3/h) considering the CMC (calibration and measurement capability) of the participating laboratories. The purpose of the proficiency test was to find out measurement equivalence of the CMC’s between each participating laboratory and the reference testing laboratory (KRISS). The measurement equivalence was tested by the number of equivalence (En). If |En| < 1, the measurement equivalence was established. All the participating laboratories passed this proficiency test.
[en] The domestic unique research reactor, HANARO (Hi-flux Advanced Neutron Application ReactOr), has been constructed with the open-pool, the core is submerged in, for the multi-purpose neutron application. The reactor has a primary cooling system to remove the fission heat from the core and its connected fluidic systems. Since the works are required at the reactor pool top as a characteristic of the research reactor, the radiation shall be minimized with the operation of the hot water layer system to avoid unnecessary radiation exposure on the workers during work at the pool top. Moreover, the pool water management system is connected to the reactor pool to maintain the pool temperature below 50℃ to minimize the uprising radioactive gas or impurity from the colder pool bottom. For the efficient flow rate of the PWMS, the thermal capacity of heat exchanger is selected with 260 kW in the normal operation condition. In this paper, the modeling is formulated to figure out whether or not each pool temperature maintains below the temperature limit and the calculation results show that the des
[en] In this review paper, the trend for optical technology is described as the development of mechanical industries in the 21st century. Optical technology has been essential in various industries such as mechanical, electronic industries as the convergence technology. Based on the roadmap of optical science and technology, 12 working groups are categorized as the technical point of view and most of them are closely related to mechanical industries. Especially, solid-state lighting, optical metrology and industrial laser processing are important technologies in precision engineering and manufacturing. This paper introduces these optical technologies and their technological issues to look into the development trends and expectation.
[en] This paper deals with a walking pattern generation algorithm with waist motion for improving the energy efficiency of a quadruped robot. Most quadruped robots without a waist joint have problems that walking is unnatural compared with quadruped animals, and their energy efficiency is low owing to the limited degrees-of-freedom of the body. To solve these problems, we studied the walking pattern generation of a quadruped robot with a waist joint. First, we selected walking parameters and generated foot trajectories by referring to the actual walking data on a dog. Second, we generated the body trajectory using the preview control to maintain walking stability. Third, we realized a quadruped walking pattern generation algorithm by integrating a waist motion generation strategy capable of improving energy efficiency and animal mimicry. Finally, the walking stability and energy efficiency improvements of the quadruped robot were verified through the Webots dynamics simulator.