• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.6
• /
• pp.396-402
• /
• 2009

Recently many efforts have been carried out on the development of energy-efficient and environment-friendly systems in order to preserve natural environment and to reduce environmental loads in the branch of the urban planning and the building design. In this study, a mathematical method was developed and a numerical analysis was carried out with various parameters to provide substantial data for optimal design and operation of urban energy supply systems. Components of the system and their specifications, such as a co-generation system and other heating and cooling systems, could be obtained through this analysis for various resource and energy requirements in urban area. In this study, the system constituents and operating characteristics, and their economic performances such as the value of objective function, the amount of energy consumption were discussed for various load patterns and power load ratios. Also, it turns out that the optimal energy supply system can save energy by $10{\sim}20%$ in comparison with the conventional energy supply system.

• Proceedings of the KSME Conference
• /
• 2001.06c
• /
• pp.548-553
• /
• 2001

Recently, much attention is imposed on the design of the fuel assemblies in the Pressurized Light Water Reactor (PWR). Spacer grid is one of the main structural components in a fuel assembly. It supports fuel rods, guides cooling water and protects the system from the external impact loads. Various space grids have been proposed and new designs are also being created. In this research, a new spacer grid is designed by the axiomatic approach. The Independence Axiom is utilized for the design. For conceptual design, functional requirements (FRs) are defined and corresponding design parameters (DPs) are found to satisfy FRs in sequence. Overall configuration and shapes are determined in this process. Detail design is carried out based on the result of the axiomatic design. For the detail design, the system performances are evaluated by using linear and nonlinear finite element analysis. The dimensions are determined by optimization. Some commercial codes are utilized for the analysis and design.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.8
• /
• pp.1623-1630
• /
• 2002

Recently, much attention is imposed on the design of the fuel assemblies in the Pressurized Light Water Reactor (PWR). Spacer grid is one of the main structural components in a fuel assembly. It supports fuel rods, guides cooling water, and maintains a coolable geometry from the external impact loads. In this research, a new shape of the spacer grid is designed by the axiomatic approach. The Independence axiom is utilized for the design. For conceptual design, functional requirements (FRs) are defined and corresponding design parameters (DPs) are found to satisfy FRs in sequence. Overall configuration and shapes are determined in this process. Detail design is carried out based on the result of the axiomatic design. For the detail design, the system performances are evaluated by using linear and nonlinear finite element analysis. The dimensions are determined by optimization. Some commercial codes are utilized for the analysis and design.

• Solar Energy
• /
• v.12 no.1
• /
• pp.72-80
• /
• 1992

This paper is concerned with the accurate estimation of the thermal mass effect on the variation of indoor temperature for residential buildings. To carry out the analysis here, the method called "PSTAR(Primary and Secondary Terms Analysis and Renormalization)" has been extensively used. This method was originally developed by the National Renewable Energy Laboratory(NREL) in the United States. The test results reported here represent two extreme cases of the interior thermal mass, which demonstrate its effect on the interior thermal environment as well as on the overall thermal behavior of the building structure. The monthly heating and cooling loads are also extrapolated by using the renormalized model, which are crucial in designing and refurbishing HVAC systems for the building.

• Journal of computational fluids engineering
• /
• v.6 no.1
• /
• pp.1-13
• /
• 2001

The natural convection heat transfer and solidification in a stratified pool are studied. The flow and heat transfer characteristics in a heat generating pool are compared between single-layered and double-layered pools. And local Nusselt number distributions on outer walls are obtained to consider thermal loads on a vessel wall. The cooling and solidification of Al₂O₃/Fe melt in a hemispherical vessel are simulated to study the mechanism of heat transfer and temperature distribution. A unstructured mesh is chosen for this study because of the non-orthogonality originated from the boundaries of double-layered pool. Interface between the layers is modeled to be fixed. With this assumption mass flux across the interface is neglected, but shear force and heat flux are considered by boundary conditions. The colocated cell-centered finite volume method is used with the Rhie-Chow interpolation to compute cell face velocity. To prevent non-physical solutions near walls in case body force is large the wall pressure is extrapolated by the way to include body force. The numerical solutions calculated by current method show that averaged downward heat flux of the double-layered pool increases compared to single-layered pool and maximum temperature occurs right below the interface of the layers.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.7
• /
• pp.26-35
• /
• 2003

This study explains the effects of lubricant and surface treatment on hot forging die life. The mechanical and thermal load, and thermal softening which is happened by the high temperature of die, in hot and warm forging, cause die wear, heat checking and plastic deformation, etc. This study is fur the effects of solid lubricants and surface treatment condition for hot forging die. Because cooling effect and low friction are essential to the long life of dies, optimal surface treatment and lubricant are very important to improve die life for hot forging process. The main factors, which affect die hardness and heat transfer, are surface treatments and lubricants, which are related to thermal diffusion coefficient and heat transfer coefficient, etc. For verifying these effects, experiments are performed for hot ring compression test and heat transfer coefficient in various conditions as like different initial billet temperatures and different loads. The effects of lubricant and surface treatment for hot forging die life are explained by their thermal characteristics. The new developed technique in this study for predicting tool life can give more feasible means to improve the tool life in hot forging process.

• 한국태양에너지학회:학술대회논문집
• /
• 2008.11a
• /
• pp.190-195
• /
• 2008

The objective of this research is to determine overall heat transfer coefficients (K-value) of exterior wall, floor, and roof of Nakseonjae, a Korean traditional residence via field measurement of transient heat flow and temperature difference across each envelope component. Heat flow sensors and T-type thermocouple were attached on the internal and the external surface of each building component, and real-time measurement data were collected for the three consecutive summer days. The K-values determined in this research showed good agreement with other results from open literature. Peak and annual thermal loads of the traditional residence estimated by a commercial energy simulation program were compared with those for a current apartment house. The traditional house showed lower annual cooling load than that of the current building. It may caused by the fact that the traditional building has less air-tight envelopes and no fenestration passing direct solar radiation into the space.

• Journal of the Korean Solar Energy Society
• /
• v.32 no.2
• /
• pp.42-49
• /
• 2012

In this article, the author carried out a theoretical study on the application techniques of a new Combined Passive Solar System (hereinafter referred to as the CPSS) of direct gain and trombe walls to get quick morning heating and to prevent afternoon overheating for office building. The numerical model proposed in this study can be used for the performance analysis of the CPSS in the winter and summer. Heating and Cooling loads are analysed for building energy consumption reduction using this numerical model. The results indicate that CPSS in the winter and summer modes could provide profitable conditions for improvement of indoor thermal comfort control and energy saving. consequently, the application of CPSS will not lead to significant reductions in the auxiliary air conditioning demand but also realize the environmentally friendly building.

• Journal of the Korean Solar Energy Society
• /
• v.31 no.3
• /
• pp.101-108
• /
• 2011

This study aims to suggest an energy consumption improvement plan for university buildings through an analysis of energy consumption. Upon a simulation of subject building to interpret energy consumption, it was found that 154.07kWh/$m^2$ of energy is consumpted annually. Improvement of design elements can cut down the energy consumption to 135.61kWh/$m^2$ according to an energy reduction analysis related to envelope performance improvement. Additional improvement of lights and heat exchanger can curtail annual energy consumption to 108.32kWh/$m^2$. Also, an analysis of energy consumption while increasing indoor temperature gradually showed that the two factors are in proportion. $6^{\circ}C$ higher temperature requires over twice of the current energy. Based on this survey result, performance improvement due to building management and envelope elements which influence to building cooling and heating loads can curtail building energy consumption.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.2076-2082
• /
• 2003

A cross-flow fan is widely used on many industrial fields: mining industry, automobile and home appliances, etc. The design point of the cross-flow fan is generally based on the region within low static pressure and high flow rate. It relatively makes high dynamic pressure at low speed because a working fluid passes through an impeller blade twice. However, it has low static pressure efficiency between 30% and 40% because of relative high impact loss. Recently, in the air-conditioning systems, the operating behaviors at the off-design points are highly regarded to broaden the application area for various air-cooling loads. Especially, at the lower flow rate, there exists a rapid pressure head reduction, a noise increase and an irregular flow field against a rearguider as a scroll of centrifugal fan. Numerical analyses are carried out for investigating the flow characteristics in a cross-flow fan including the impeller, the rearguider and the stabilizer. Especially, various types of rearguiders are estimated by numerical and experimental methods to insure the stable operation in the region of lower flow rate. Numerical domains are discretized by hexahedral cells. Three-dimensional, unsteady governing equations are solved using FVM, PISO algorithm, sliding grid system and standard ${\kappa}-{\varepsilon}$ turbulence model. ASHRAE standard fan tester is also used to estimate the performance of the modeled crossflow fan.