• KIEAE Journal
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• v.10 no.4
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• pp.75-80
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• 2010

Generally, ground-source heat pump (GSHP) systems have a higher performance than conventional air-source systems. However, the major fault of GSHP systems is their expensive boring costs. Therefore, it is important issue that to reduce initial cost and ensure stability of system through accurate prediction of the heat extraction and injection rates of the ground heat exchanger. Conventional analysis methods employed by line source theory are used to predict heat transfer rate between ground heat exchanger and soil. Shape of ground heat exchanger was simplified by equivalent diameter model, but these methods do not accurately reflect the heat transfer characteristics according to the heat exchanger geometry. In this study, a numerical model that combines a user subroutine module that calculates circulation water conditions in the ground heat exchanger and FEFLOW program which can simulate heat/moisture transfer in the soil, is developed. Heat transfer performance was evaluated for 3 different types ground heat exchanger(U-tube, Double U-tube, Coaxial).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.7
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• pp.1038-1044
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• 2013

A research on thermal analysis method is conducted for the characterization of heat generation during operation of Interior Permanent Magnet Synchronous Motor(IPMSM) for Light Railway Transits(LRT) in this paper. Efficient cooling of the heat generated in the IPMSM is important because the excessive heat generated from the winding, core and permanent magnet makes it harder for a long time continuous operation of IPMSM. Therefore, in order to analyze the heat generation characteristics of the 110kW-class IPMSM as advanced research for application the IPMSM to the cooling device, the heat transfer coefficients for each component of the 110 kW-class IPMSM were derived and the thermal equivalent network was configured to perform the thermal analysis in this study. Finally, the 110kW-class IPMSM prototype is made and a comparative verification between the test data and the thermal analysis results through its various performance tests are carried out.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.1140-1151
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• 2023

Fully Ceramic Microencapsulated (FCM) fuel is emerging advanced fuel material for the future nuclear reactors. The fuel pellet in the FCM fuel is composed of matrix and a large number of TRistructural-ISOtopic (TRISO) fuel particles which are randomly dispersed in the SiC matrix. The minimum layer thickness in a TRISO fuel particle is on the order of 10^-5 m, and the length of the FCM pellet is on the order of 10^-2 m. Hence, the heat transfer in the FCM pellet is a multi-scale phenomenon. In this study, three multi-scale heat conduction models including the Multi-region Layered (ML) model, Multi-region Non-layered (MN) model and Homogeneous model for FCM pellet were constructed. In the ML model, the random distributed TRISO fuel particles and coating layers are completely built. While the TRISO fuel particles with coating layers are homogenized in the MN model and the whole fuel pellet is taken as the homogenous material in the Homogeneous model. Taking the results by the ML model as the benchmark, the abilities of the MN model and Homogenous model to predict the maximum and average temperature were discussed. It was found that the MN model and the Homogenous model greatly underestimate the temperature of TRISO fuel particles. The reason is mainly that the conventional equivalent thermal conductivity (ETC) models do not take the internal heat source into account and are not suitable for the TRISO fuel particle. Then the improved ETCs considering internal heat source were derived. With the improved ETCs, the MN model is able to capture the peak temperature as well as the average temperature at a wide range of the linear powers (165 W/cm~ 415 W/cm) and the packing fractions (20%-50%). With the improved ETCs, the Homogenous model is better to predict the average temperature at different linear powers and packing fractions, and able to predict the peak temperature at high packing fractions (45%-50%).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.8
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• pp.664-671
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• 2006

We propose the correlation to predict the spreading thermal resistance on a plate with symmetrical four heat sources. The correlation transforms four heat sources to a single equivalent heat source and then the spreading thermal resistance can be obtained with the existing equation for a single heat source. When the four heat sources are mounted on a square base plate, the correlation is expressed as a function of the heat source size, the length of base plate, the plate thermal conductivity and the distance between heat sources. Compared to the results of three-dimensional numerical analysis, the spreading thermal resistance by the proposed correlation is in good agreement within 10 percent accuracy.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.893-898
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• 2014

Recently, the interior permanent synchronous motor (IPMSM) has been applied to an integrated starter and generator (ISG) for hybrid electric vehicles. In the design of such a motor, thermal analysis is necessary to maximize the power density because the loss is proportional to the power of a motor. Therefore, a cooling device as a heat sink is required internally. Generally, a cooling system designed with a water jacket structure is widely used for electric motors because it has advantages of simple structure and cooling effectiveness. An effective approach to analyze an electric machine with a water jacket is a thermal equivalent network. This network is composed of thermal resistance, a heat source, and thermal capacitance that consider the conduction, convection, and radiation. In particular, modeling of the cooling channel in a network is challenging owing to the flow of the coolant. In this paper, temperature prediction using a thermal equivalent network is performed in an ISG that has a water cooled system. Then, an experiment is conducted to verify the thermal equivalent network.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.681-688
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• 2004

For use of the thermal cycle of the biochemical fluid sample, the isothermal temperature source with a large surface area was designed, fabricated and its thermal characterization was experimentally evaluated. The comprehensive overview of the technology trend on the temperature control devices was detailed. The large surface area isothermal temperature source was realized by using the vapor chamber heat spreader. The cost-effectiveness and simple manufacturing process were achieved by using the metal-etched wick structure. The temperature distribution was quantitatively investigated by using IR temperature imaging system at equivalent temperatures to the PCR thermal cycle. The standard deviation was measured to be within 0.7$^{\circ}C$ for each temperature cycle. This concludes that the presented isothermal temperature source enables no temperature gradient inside bio-sample fluid. Furthermore it can be applied to the cooling of the electronic devices due to its slimness and low thermal spreading resistance.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.928-933
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• 2009

The purpose of this study is to examine the energy consumption, carbon dioxide emission & energy cost of district heating using sewage source. The annual TOE of heat pump using sewage source save 37.1 percent than city gas boiler. And annual carbon dioxide emission of heat pump cut down 41.3 percent than city gas boiler. If it charges the rate schedule for district heating to apartment resident, collected amount are 3,127,170 thousand won. As energy cost of heat pump & circulation pump are 1,378,072 thousand won. the profits are 1,749,098 thousand won. As payback period is 8.97years, applicability is low level. However, it has advantages in energy consumption, carbon dioxide emission & energy cost. Therefore, it needs to proceed through government assistance.

• Land and Housing Review
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• v.9 no.4
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• pp.25-32
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• 2018

Application of geothermal energy in buildings has been gaining popularity as it provides the benefits of both heating and cooling a building. Among the various types of geothermal energy systems, ground-coupled heat pump system is the most commonly applied one in South Korea. A ground heat exchanger plays an important role as a heat source in winter and a heat sink in summer. For the stable operation of a ground-coupled heat pump system, a ground heat exchanger should be sized so that it provides sufficient heating and cooling energy. Heating and cooling energies generated in ground heat exchangers mainly depend on the temperature difference between the heating medium in ground heat exchangers and the surrounding ground. In addition, the performance of ground heat exchangers influences the change in ground temperature. Therefore, it is necessary to consider this interrelation between the change in the ground temperature and the performance of ground heat exchanger for an accurate estimation of its performance. However, previous thermal analysis models for ground heat exchangers are not competent enough to allow a complete understanding of this interrelation. Therefore, this study proposes a three-dimensional equivalent, transient ground heat exchanger analysis model. First, a previous thermal analysis model for ground heat exchangers, including an analytical model, a g-function, and a numerical model are analyzed. Next, to overcome the limitations of the previous models, a three-dimensional equivalent, transient ground heat exchanger model is proposed. Finally, this study validated the proposed model with the measurement data of the thermal response test, sandbox test, and TRNSYS DST model. All validation results showed a good agreement. These findings helped us to investigate the thermal performance of ground heat exchangers more accurately than the analytical models, and faster than the numerical models. Furthermore, the proposed model contributes to the design of ground heat exchangers by considering the different operation conditions of buildings.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.38-43
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• 2011

This study was carried out to evaluate the structural stability of hybrid type fan heater. The evaluation of structural safety of hybrid fan heater was conducted by using Ansys Workbench and CFX-11 under the design condition. The hybrid fan heater was operated by heat transfer for heat source supplied from electric heater and combustion gas. According to result of structural analysis, the maximum equivalent stress of hybrid fan heater was 150MPa when the temperature of heat transfer fluids was $150^{\circ}C$. It was found that the hybrid fan was structurally safe because the value of maximum equivalent stress was smaller than that of yield stress of the material.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3A
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• pp.391-399
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• 2008

Because of relatively high temperature, over $240^{\circ}C$, of asphalt for steel deck bridge during pavement procedure, the temperature of deck could rise over $100^{\circ}C$ and undesirable excessive displacement and thermal stress could occur. In this study, in order to estimate the thermal effect of pavement process and to find the optimal pavement process, a new thermal analysis technique with Equivalent Heat Source (EHS) is proposed and its applicability to the practical pavement of steel bridge is studied. EHS is developed to simulate the high temperature pavement materials and its thermal effect such as conduction and convection which cannot be explain easily in general structural analysis program for bridge design. To verify the applicability of new analysis technique with EHS, thermal analyses of steel deck bridge with uplift and curved bridge with various pavement procedures are presented.