• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.9
• /
• pp.916-922
• /
• 2009

Because thermal design of satellite carrying out mission in space is performed by thermal analysis result using thermal mathematical model, accuracy of thermal mathematical model is important and it can be improved by model correlation. Correlation steps of satellite thermal math model are composed of modeling of satellite configuration placed in thermal vacuum chamber, verification of correspondence between thermal math model and real satellite configuration, and adjustment of modeling parameters from major part to minor part etc. In this study, correlation success criteria was established and correlation for satellite thermal math model was performed using result of thermal vacuum test of satellite structure-thermal model to meet the success criteria. The overall results satisfied the criteria and this correlated thermal model was applied for detailed thermal design of satellite.

• Journal of Energy Engineering
• /
• v.21 no.2
• /
• pp.144-151
• /
• 2012

A district heating system produces thermal energy and supplies it to a large region. District heating systems can provide higher efficiencies and better pollution control than localized boilers. The heat generated by a district heating system is distributed to the customer via a network of insulated pipes. For the optimal operation of a district heating system, it is important to predict the distributions of pressure, flow rate and temperature of heating fluid within the network of pipes at various operating conditions. In this work, a mathematical modeling was performed to predict the dynamic hydraulic-thermal behaviors of heating fluid in the network of pipes for a district heating system. The mathematical model accounts for the conservations of mass, momentum and energy. In order to verify the validity of modeling, the modeling results were compared with the monitoring data of Gang-nam Branch of District Heating.

• Journal of Energy Engineering
• /
• v.20 no.1
• /
• pp.1-7
• /
• 2011

The performance and life-cycle costs of electric vehicle(EV) and hybrid electric vehicle(HEV) depend inherently on battery packs. Temperature uniformity in a pack is an important factor for obtaining optimum performance for an EV or HEV battery pack, because uneven temperature distribution in a pack leads to electrically unbalanced battery cells and reduced pack performance. In this work, a three-dimensional modeling was carried out to investigate the effects of operating conditions on the thermal behavior of a lithium-ion battery pack for an EV or HEV application. Thermal conductivities of various compartments of the battery were estimated based on the equivalent network of parallel/series thermal resistances of battery components. Heat generation rate in a cell was calculated using the modeling results of the potential and current density distributions of a battery cell.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.12 no.1
• /
• pp.43-49
• /
• 2007

The methods of physical oceanographic surveys to examine the effect of thermal discharge from nuclear power plants in Korea have been reviewed and a standard guide to the survey is proposed. It is desirable that in situ observation and numerical thermal diffusion modeling are conducted simultaneously to describe the variation in temperature distribution affected by thermal discharge from a power plant because any observation or numerical modeling alone has limits to do so quantitatively. It is suggested that the field observation must be based on the concept of heat budget modeling considering all artificial and natural heat sources/sinks around the power plant. Any results from numerical modeling must reach to a certain statistical significance level to use for a standard temperature distribution. In addition, the development of standard numerical codes is proposed to improve the problems shown in the past numerical circulation and diffusion modelling.

• Journal of Construction Engineering and Project Management
• /
• v.5 no.4
• /
• pp.16-22
• /
• 2015

This paper presents an automated computer vision-based system to update BIM data by leveraging multi-modal visual data collected from existing buildings under inspection. Currently, visual inspections are conducted for building envelopes or mechanical systems, and auditors analyze energy-related contextual information to examine if their performance is maintained as expected by the design. By translating 3D surface thermal profiles into energy performance metrics such as actual R-values at point-level and by mapping such properties to the associated BIM elements using XML Document Object Model (DOM), the proposed method shortens the energy performance modeling gap between the architectural information in the as-designed BIM and the as-is building condition, which improve the reliability of building energy analysis. Several case studies were conducted to experimentally evaluate their impact on BIM-based energy analysis to calculate energy load. The experimental results on existing buildings show that (1) the point-level thermography-based thermal resistance measurement can be automatically matched with the associated BIM elements; and (2) their corresponding thermal properties are automatically updated in gbXML schema. This paper provides practitioners with insight to uncover the fundamentals of how multi-modal visual data can be used to improve the accuracy of building energy modeling for retrofit analysis. Open research challenges and lessons learned from real-world case studies are discussed in detail.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.12
• /
• pp.1140-1148
• /
• 2004

Recently the Predicted Mean Vote (PMV) has been used as an important index to evaluate the degree of the indoor thermal comfort in modern residential buildings. It is known that the PMV is mainly affected by four major factors, which are the air temperature, the air velocity, the humidity and the mean radiant temperature (MRT). Through the numerical calculation of the temperature and the modeling of the mean radiant temperature considering the solar radiation, we proposed the new modeling strategies of the mean radiant temperature and investigated the PMV index and evaluated the MRT. Also, we compared the numerical results with the experimental values. As the results, we found out that the MRT is affected by the wall temperature and the solar radiation. We also knew that the new modeling strategies of the mean radiant temperature is a more correct way of PMV calculation. Especially, the new modeling is necessary for the spaces like an atrium and large rooms with windows mainly influenced by solar radiation.

• International conference on construction engineering and project management
• /
• 2015.10a
• /
• pp.532-536
• /
• 2015

This paper presents an automated computer vision-based system to update BIM data by leveraging multi-modal visual data collected from existing buildings under inspection. Currently, visual inspections are conducted for building envelopes or mechanical systems, and auditors analyze energy-related contextual information to examine if their performance is maintained as expected by the design. By translating 3D surface thermal profiles into energy performance metrics such as actual R-values at point-level and by mapping such properties to the associated BIM elements using XML Document Object Model (DOM), the proposed method shortens the energy performance modeling gap between the architectural information in the as-designed BIM and the as-is building condition, which improve the reliability of building energy analysis. The experimental results on existing buildings show that (1) the point-level thermography-based thermal resistance measurement can be automatically matched with the associated BIM elements; and (2) their corresponding thermal properties are automatically updated in gbXML schema. This paper provides practitioners with insight to uncover the fundamentals of how multi-modal visual data can be used to improve the accuracy of building energy modeling for retrofit analysis. Open research challenges and lessons learned from real-world case studies are discussed in detail.

• Proceedings of the IEEK Conference
• /
• 2005.11a
• /
• pp.171-174
• /
• 2005

The circuit simulation analysis and diagnosis methods are used to instruments in detail when they give apparently abnormal readings. In this paper, a new simulator through an analysis of the important circuits modeling under severe accident conditions has been designed, the realization for a body work instead of the two sorts of the Labview & Pspice as an one order command in the Labview program. The program can be shown the output graph form the circuit modeling as an order commend. The procedure for the simulator design was divided into two design steps, of which the first step was the diagnosis methods, the second step was the circuit simulator for the signal processing tool. It has three main functions which are a signal processing tool, an accident management tool, and an additional guide from the initial screen.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.8 no.4
• /
• pp.19-28
• /
• 1999

In order to control thermal deformation of the machine origin of machine tools a empirical model and a compensation system have been developed, Prior to empirical modeling the volumetric error considering shape errors and joint errors of slides is formulated through the homogeneous transformation matrix (HTM) and kinematic chain. Simulation results of the HTM method show that the thermal error of the machine origin is more critical than position-dependent errors. In order to make a stable and effective software error compensation system the GMDH (Group Method of Data Handling) models are constructed to estimate the thermal deformation of the machine origin by measuring deformation data and temperature data. A test bar and gap sensors are used to measure the deformation data. In order to compensate the estimated error the work origin shift method is developed by implementing a digital I/O interface board between a CNC controller and an IBM PC. The method shifts the work origin as much as the amounts which are calculated by the pre-established thermal error model. The experiment results for a vertical machining center show that the thermal deformation of the machine origin is reduced within $\pm$5$mu extrm{m}$.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.10 s.181
• /
• pp.2589-2596
• /
• 2000

As current manufacturing processes require high spindle speed and precise machining, increasing accuracy by reducing volumetric errors of the machine itself, particularly thermal errors, is very important. Thermal errors can be estimated by many empirical models, for example, an FEM model, a neural network model, a linear regression model, an engineering judgment model, etc. This paper discusses to make a modeling of thermal errors efficiently through backward elimination and fuzzy logic strategy. The model of a thermal error using fuzzy logic strategy overcomes limitation of accuracy in the linear regression model or the engineering judgment model. It shows that the fuzzy model has more better performance than linear regression model, though it has less number of thermal variables than the other. The fuzzy model does not need to have complex procedure such like multi-regression and to know the characteristics of the plant, and the parameters of the model can be mathematically calculated. Also, the fuzzy model can be applied to any machine, but it delivers greater accuracy and robustness.