• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.709-710
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• 2008

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.621-628
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• 2019

The use of the ammonia-water zeotropic mixture as a working fluid in the power generating system has been considered as a proven technology for efficient recovery of low-grade heat sources. This paper presents a thermodynamic performance analysis for ammonia-water evaporator using low-grade heat source, based on the exergy and entransy which has been recently introduced as a physical quantity to describe the heat transfer ability of an object. In the analysis, effects of the ammonia mass fraction and source temperature of the binary mixture are investigated on the system performance such as heat transfer, effectiveness, exergy destruction, entransy dissipation, and entransy dissipation based thermal resistance. The results show that the ammonia mass concentration and the source temperature have significant effects on the thermodynamic system performance of the ammonia-water evaporator.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.1
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• pp.65-72
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• 2012

Rankine cycle using ammonia-water mixture as a working fluid has attracted much attention, since it may be a very useful device to extract power from low-temperature heat source. In this work, the thermodynamic performance of regenerative ammonia-water Rankine cycle is thoroughly investigated based on the second law of thermodynamics and exergy analysis, when the energy source is low-temperature heat source in the form of sensible energy. In analyzing the power cycle, several key system parameters such as ammonia mass concentration in the mixture and turbine inlet pressure are studied to examine their effects on the system performance including exergy destructions or anergies of system components, efficiencies based on the first and second laws of thermodynamics. The results show that as the ammonia concentration increases, exergy exhaust increases but exergy destruction at the heat exchanger increases. The second-law efficiency has an optimum value with respect to the ammonia concentration.

• Solar Energy
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• v.18 no.4
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• pp.11-22
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• 1998

Floor panel heating system using hot water is the primary heating system of domestic residential building. This paper presents the results of performance analysis of the heat pump system with air source evaporator and single unit dual sink(SUDSk) condenser. The heat exchanger combines two separated condensers into a single condenser and the object of the SUDSk condenser is to release energy to dual sinks, i.e. air for air heating system and water for panel heating system in one single unit. Simulation program is developed for single unit dual source(SUDS) SUDSk heat pump system and some experimental data are obtained and compared with simulation results. Differences of heating capacity and COP in dual source operating mode are 7% and 8% respectively. Simulation results are in good agreement with test results. Therefore, developed program is effectively used for design and performance prediction of dual source dual sink heat pump system with SUDS evaporator and SUDSk condenser.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.862-863
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• 2007

In this article, we researched the characteristics of heat transfer of the bimetal for over-current protection device. Bimetal consists of two metals which have a different thermal expansion coefficient. To analyze the heat transfer characteristics, by using a bimetal which has a single metal, we analyzed the temperature distribution when bimetal acts a switch. As usual, heat source is applied to the bimetal. But, in the over-current protection switch, the current become heat source. So, by using the current as source, we performed the magnetic analysis and thermal analysis together.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.12
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• pp.1023-1029
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• 2015

Laser-assisted machining (LAM) is one of the most effective methods for enhancing the machinability of difficult-to-cut materials, such as titanium alloys and various ceramics, and has been studied by many researchers. LAM is a method that facilitates machining by softening a workpiece using a laser heat source. The advantages of the LAM process are decreases in tool wear, cutting force, and surface roughness. However, when the material is over-heated, melting or burning can occur. This study analyzed the heat source distribution with regard to overlapping of preheating on the laser heating path with an acute angle, a right angle and obtuse angles. Then, a power reduction method was proposed to reduce the melting and burning of the workpiece.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.569-572
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• 2003

In VLM-ST process, the fine detailed shape processing process is needed due to the use of thick sheets for layers. The developed process perform the fine detailed shape processing in VLM-ST parts using non-contact hot tool. To predict the heat-affected zone and temperature distribution of VLM-ST parts in detailed shaping, the heat flux from the tool to the surface was calculated for the finite element analysis by modeling the tool as a heat source of radiation. The dominant process parameters such as the radiated heat input, the tool speed, and the gap between the tool tip and the foam sheet (tool height) were considered in the analysis. The results showed a good agreement with the experiments.

• Journal of Welding and Joining
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• v.31 no.4
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• pp.62-66
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• 2013

Overlay welding is carried out to improve the corrosion resistance, wear resistance and heat resistance on the surface of the chemical plant and steelmaking plant structures. In overlay welding, control of the bead size and the temperature distribution of weldment are particularly important because that is directly connected to the improvement of quality and productivity. The aim of this study is to model the welding heat source that is very useful to analyze the bead size and temperature distribution of weldment. To find the welding heat source model, numerical analyses are performed by using FE software MSC-marc.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.8 no.4
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• pp.17-23
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• 2012

Due to reinforcement of international environment regulation and high oil prices, interest in renewable energy is growing. Countries participating in UNFCCC are continuously putting efforts in reducing greenhouse gas after enforcing Kyoto Protocol into effect on Feb, 2005. Energy used in buildings, which relies heavily on fossil fuel accounts for about 24% of total energy consumption. In this study, air, geothermal and water source heat pump systems for an 322 $m^2$ auditorium in an office building is simulated using TRNSYS version 17 for comparing energy consumptions. The results show that energy consumptions of air, geothermal and water source heat pumps are 14,485, 10,249, and 10,405 kWh, respectively. Annual equal payments which consider both initial and running costs become 5,734,521, 6,403,257 and 5,596,058 Won. Thus, water source heat pump is the best economical choice.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.195-201
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• 2001

An inverse heat conduction problem(IHCP) arises when unknown heat fluxes and whole temperature field are to be found with temperature measurements of a few points. In this paper, observers are proposed as solution algorithm for the IHCP. A 1-dimensional heat transfer problem is modeled with modal analysis and state space equations. Position of the heat source is estimated through test heat inputs and the autocorrelation among a few of temperature data. The modified Bass-Gura method is used to design a state observer to estimate the intensity of heat source and the whole temperature field of a 1-dimensional body. To verify the reliability of this estimator, analytic solutions obtained from the proposed method are compared.