• 한국태양에너지학회 논문집
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• 제26권4호
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• pp.9-16
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• 2006

Geothermal-energy has been getting popular as a natural energy source for green buildings these days. Public building with gross area more than $3000m^2$, planned after March, 2005, should spend about 5% of total building cost for equipment run by natural energy source (e.g. geothermal, solar heat, solar power, etc) according to renewable energy promotion law in Korea. As a result geothermal-energy using heat pump system is emerging as a effective alternative for realistic and economic plan although design guidelines and construction code for the system is in progress and technical data is far from sufficient. The quantitative analysis on the performance of geothermal-energy using heat pump system is insufficient for appropriate design of it. In this paper, cooling performance of geothermal-energy using heat pump system of residential and retail etc. mixed-use building has been analyzed on the basis of temperature comparison between inlet and outlet of heat exchangers of the operating system. Additionally, dry-bulb temperature and relative humidity have been measured and analyzed together as an index of indoor thermal environment.

• 한국유체기계학회 논문집
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• 제19권6호
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• pp.34-42
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• 2016

The organic Rankine cycle (ORC) has been used to convert thermal energy to mechanical energy or electricity. The available thermal energy could be waste heat, solar energy, geothermal energy, and so on. However, these kinds of thermal energies cannot be provided continuously. Hence, the ORC can be operated at the off-design point. In this case, the performance of the ORC could be worse because the components of the ORC system designed based on a design point can be mismatched with the output power obtained at the off-design point. In order to improve the performance at the off-design point, a few components were replaced including generator, bearing, load bank, shaft, pump and so on. Experiments were performed on the same facility without including other losses in the experiment. The experimental results were compared with the results obtained with the previous model, and they showed that the system efficiency of the ORC was greatly affected by the losses occurred on the components.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.97-103
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• 2007

This study was carried out to compare the thermal performance and operating characteristics of evacuated tubular solar collector(ETSC) with different working fluid. The evacuated tubular solar collectors with different working fluid of heat pipe were investigated in the same operating condition for a indoor experiment equipment. First, the result of working fluid with Water showed that $F_R({\tau}{\alpha})$ was 0.6636 and $F_RU_L$ was -1.8457 Second, Ethanol showed that $F_R({\tau}{\alpha})$ was 0.6147 and $F_RU_L$ was -0.6365. Third, Flutec-pp9 showed that $F_R({\tau}{\alpha})$ was 0.515 and $F_RU_L$ was -3.2313. Finally MA's showed that $F_R({\tau}{\alpha})$ was 0.6572 and $F_RU_L$ was -2.0086.

• 한국태양에너지학회 논문집
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• 제28권5호
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• pp.28-35
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• 2008

The aim of this study was to analysis the Heating/cooling performance of movable insulation system built in apartments. The process of this study is as follows: 1) Test-cells of movable insulation are designed through the investigation of previous paper and work. The type of the movable insulation used in test-cell is low emissivity(5%) insulation, measured for heating season and the thermal effects are analyzed. 2) The simulation program(Design Builder) was used in energy performance analysis. the reference model of simulation was made up to analysis energy performance on movable insulation system. 3) Selected reference model(Floors:15, Area of Unit:115.5$m^2$) for heating/cooling energy analysis, Energy performance simulation with various variants, such as slate angle of movable insulation(5$^{\circ}$, 30$^{\circ}$, 50$^{\circ}$) and position of movable insulation. Consequently, When movable insulation system is equipped with balcony window of Apartment, Annual heating energy of reference model was cut down at the average of 5.4kWh/$m^2$ or 4.6% of heating/cooling energy.

• KIEAE Journal
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• 제16권2호
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• pp.33-41
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• 2016

Purpose: The window energy rating system was developed in early 1990's and various kind of rating system has been implemented in advanced country such as Europe, Australia, Canada and the US since 2000. In Korea, the Energy Consumption Efficiency Rating Indication System has been implemented to promote supply of high efficiency window since July 2012. Normally, the window energy rating system based on heat balance which considers both thermal losses and solar heat gain is used and applied only to residential buildings. However, the system used nationally only considers thermal losses and is applied to every building regardless of its usage. Therefore, in this study, we indicated problems of domestic window energy rating system and looked for improvements. Method: We analyzed thermal performance of various windows through dynamic simulation applied to detached house and compared results with those of domestic and foreign rating system. Result : Thermal performance of south windows is more affected by SHGC than U-value, and that of north windows is also affected by SHGC a lot. The difference between the results of our study and current system is statistically significant. As a result, appropriate evaluation criteria which considers solar heat gain is required.

• 한국태양에너지학회 논문집
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• 제34권6호
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• pp.27-37
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• 2014

Heat island is caused by changes of land coverage structure of cities and use of energy in buildings. As a result energy use in buildings get to increase further followed by rising of GHG emission and deteriorating climate change. Eco-friendly housing complex is a kind of plan that applies environmental control elements like water and green spaces to housing complex. With these methods, it can be expected to create thermal environment of indoor and outdoor. In this paper quantitative examination is studied on using CFD to find out the effects of river, water permeable, parks and planting on thermal environment. And by comparing field measurements with CFD results which are aimed to development phase housing complex, feasibility and usability of the CFD analysis results are confirmed. And also, analysis on the ventilation performance followed by natural ventilation system is analyzed by selecting one building in housing complex. Based on the results, the possibilities of energy reduction through making thermal environment and applying natural ventilation are studied. With these outcomes, creating thermal conditions and using natural ventilation would be contributed to GHG reduction.

• 한국태양에너지학회 논문집
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• 제31권1호
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• pp.1-7
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• 2011

This study was accomplished to evaluate the performance of Multi Effect Distillation(MED) for solar thermal desalination system. It was designed Multi effect distillation with $3m^3$/day capacity and Shell&Tube type heat exchanger. Also, The effective heat transfer of Shell&Tube heat exchanger was used Cu(90%)-Ni(10%) corrugated tube. The parameters relating to the performance of Multi Effect Distillation are known as hot water flow rate. The experimental conditions for each parameters were $18^{\circ}C$ for sea water inlet temperature, $6m^3$/hour sea water inlet volume flow rate, $75^{\circ}C$ for hot water inlet temperature, 2.4, 3.6, and $4.8\;m^3$/hour for hot water inlet volume flow rate, respectively. The results are as follows, Development for Multi effect distillation was required about 40kW heat and 35kW cooling source to produce $3m^3$/day of fresh water. Based on the results of this study, It makes possible to secure economics of desalination system with solar energy which is basically needed development of high efficiency fresh water generator.

• Tribology and Lubricants
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• 제37권1호
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• pp.14-24
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• 2021

This study shows the effect of the thermal boundary condition around the tilting pad journal bearing on the static and dynamic characteristics of the bearing through a high-precision numerical model. In many cases, it is very difficult to predict or measure the exact thermal boundary conditions around bearings at the operating site of a turbomachine, not even in a laboratory. The purpose of this study is not to predict the thermal boundary conditions around the bearing, but to find out how the performance of the bearing changes under different thermal boundary conditions. Lubricating oil, bearing pads and shafts were modeled in three dimensions using the finite element method, and the heat transfer between these three elements and the resulting thermal deformation were considered. The Generalized Reynolds equation and three-dimensional energy equation that can take into account the viscosity change in the direction of the film thickness are connected and analyzed by the relationship between viscosity and temperature. The numerical model was written in in-house code using MATLAB, and a parallel processing algorithm was used to improve the analysis speed. Constant temperature and convection temperature conditions are used as the thermal boundary conditions. Notably, the conditions around the bearing pad, rather than the temperature boundary conditions around the shaft, have a greater influence on the performance changes of the bearing.

• 한국태양에너지학회 논문집
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• 제32권5호
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• pp.11-17
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• 2012

In this study, a simulation program was developed with heat transfer model in the thermal storage tank for a solar collector and burner combined heating and hot water supply system. Analysis was conducted with variation of operating condition and schedule to analyze performance of a hot water supply and panel heating system with a solar collector and burner combined thermal storage tank. The simulation program is divided two sections. One part is calculation of temperature variation of water which flows through the panel in the floor for heating of the residential house during 24 hours, and the other part is heat transfer calculation for the reaction time to get desired water temperature in the thermal storage tank. As results, light oil consumption and system performance during operation period were analyzed with variation of climate condition and with or without solar collector. Most of the case, oil could be saved about from 24 to 41% with installing the solar collector. The performance of the system is more dependent on radiation time of the solar collector rather than the intensity of the solar radiation which was adopted for the climate analysis.

• 한국세라믹학회지
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• 제54권3호
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• pp.200-204
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• 2017

Molybdenum (Mo), an electrode material of alkali metal thermal-to-electric converters (AMTEC), facilitates grain growth behavior and forms Mo-Na-O compounds at high operating temperatures, resulting in reduced performance and shortened lifetime of the cell. Mo/TiN composite materials have been developed to provide a solution for such issues. Mo is a metal that possesses excellent electrical properties, and TiN is a ceramic compound with high-temperature durability and catalytic activity. In this study, a dip-coating process with an organic solvent-based slurry was used as an optimal coating method to achieve homogeneity and stability of the electrodes. Cell performance was evaluated under various conditions such as the number of coatings, ranging from 1 to 3 times, and heat treatment temperatures of $800-1100^{\circ}C$. The results confirmed that the cell yielded a maximum power of 9.99 W for the sample coated 3 times and heat-treated at $900^{\circ}C$.