• Journal of Welding and Joining
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• v.18 no.3
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• pp.76-82
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• 2000

In this study, three-dimensional heat flow in laser beam welding for deep penetration was analyzed by using F.E.M common code, and then the results were compared with the experimental data. The models for analysis are full penetration welds and are made at three different laser powers (6, 9.9, 4.5 kW) with two different welding speeds (5.8mm/s, 5mm/s). The characteristics of thermal absorption by the workpiece during deep penetration laser welding can be represented by a combination of line heat source through the workpiece and distributed heat source at the top surface due to the plasma plume above the top surface. This gives an insight into the way in which the beam interacts with the material being welded. The analyses performed with the combined heat source models show comparatively good agreement between the experimental and calculated melt temperature isotherm, i.e, the fusion zone boundary. The results are used to explain the "nail head" appearance of fusion zone, which is quite common in laser beam welds.eam welds.

• New & Renewable Energy
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• v.1 no.4 s.4
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• pp.30-37
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• 2005

Cycle simulation of Ground Source Heat Pump[GSHP] system was carried out to determine the design specification of basic components such as turbo compressor and heat exchangers. Part load operation characteristics of the designed GSHP system was estimated using the compressor and heat exchanger performance data. A 50RT class turbo compressor for GSHP system is now under development, in which R134a refrigerant is adopted as working fluid. The compressor with variable cascade diffusers is designed to work both in cooling and heating modes so that it can actively keep up with the climate change with high efficiency. The normal running speeds of the compressor are 59000rpm for heating mode and 70000rpm for tooling mode respectively. It has two identical impellers at both ends of the rotor so as to minimize aero-induced thrust force effectively. GSHP system was coupled with a vortical type heat exchanger, and heat gain and heat loss from ground were evaluated per a bore hole. For the optimal integration of the heat pump system, its header for circulating fluid was combined with the ground heat exchangers in parallel and series configuration.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.9
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• pp.599-607
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• 2008

In this study, air conditioning systems include ground source heat pump (GSHP), are evaluated for economic feasibility. The building is modeled an air conditioned for 280kW scale. This analysis is compared with the energy tariff programs of Korea and USA. The objectives of this paper are to evaluate the cost-effectiveness of the GSHP and combined system using Life-Cycle Cost (LCC) analysis, and to carry out the sensitivity analysis of key parameters. The paper considered the cases including the base case of air source heat pump and the other two alternates for comparisons. The combined system is not only a cost-effective way to the low energy consumption but also a way to avoid a high initial investment. The variations of initial investment and energy rates give a significant effect on the total LCC and payback period.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.251-257
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• 2000

A numerical simulation of the temperature rise for sliding surface in dry contact is based on Jaeger's formula combined with a calculated heat input. A gear tooth temperature analysis was performed. The pressure distribution has the Hertzian pressure distribution on the heat source. The heat partition factor is calculated along line of action. A Temperature distribution of tooth surface is calculated about before and after profile modification. A Temperature of addendum and deddendum in modified gear have reduced.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.2
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• pp.331-337
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• 2001

A numerical simulation of the temperature rise for sliding surface in dry contact is based on Jaegers formula combined with a calculated heat input. A gear tooth temperature analysis was performed. The pressure distribution has the Hertzian pressure distribution on the heat source. The heat partition factor is calculated along ling of action. A Temperature distribution of tooth surface is calculated about before and after profile modification. A Temperature of addendum and deddendum in modified gear have reduced.

• Journal of Hydrogen and New Energy
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• v.31 no.2
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• pp.234-241
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• 2020

This paper presents a thermodynamic performance analysis of a combined cycle consisting of regenerative organic Rankine cycle (ORC) and liquefied natural gas (LNG) Rankine cycle to recover low-grade heat source and the cold energy of LNG. The mathematical models are developed and the system performances are analyzed in the aspect of thermodynamics. The effects of the turbine inlet pressure and the working fluid on the system performance such as the mass flow rates, heat transfers at heat exchangers, power productions at turbines, and thermal efficiency are systematically investigated. The results show that the thermodynamic performance of ORC such as net power production and thermal efficiency can be significantly improved by the regenerative ORC and the LNG cold energy.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.13 no.2
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• pp.22-29
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• 2017

This study is performed to performance of the combined system the GSHP (Ground Source Heat Pump) system with the Earth tube system using EnergyPlus program. The Earth tube system using fan is characteristics as supply lower (higher) air temperature than outdoor air temperature in cooling and heating seasons, the GSHP system is characteristics as small indoor air temperature variation range. As the results of Earth tube + GSHP system simulation, GSHP power can be reduced than the GSHP single operation as 17.3% in cooling seasons and 32.5% in heating seasons, the GSHP design capacity can be replaced more small size.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.588-592
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• 2006

PV Thermal combined system produces the electricity and thermal energy which are needed for buildings. The system removes heat from PV module through air or liquid, so that its efficiency will be improved. The heat as the forms of hot air or hot water can be utilized for building use, like space heating and hot water. This paper describes the concept of PV Thermal combined system and its research and development trend at local and international levels. This materials can be used as a fundamental study source about PV Thermal combined system to apply fur building space heating.

• Nuclear Engineering and Technology
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• v.31 no.3
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• pp.294-302
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• 1999

The influence of source term release parameters on offsite health effects was examined for the YGN 3&4 nuclear power plants. The release parameters considered in this study are release height, heat content, and release time. The effects of core inventory change as a function of fuel burnup was also examined. The health effects by the change of release parameters are early fatalities, cancer fatalities, and early fatality distance. The results showed that early fatalities and early fatality distance decrease as release height increases, although it does not have significant influence on cancer fatalities. The values of both early and late health effects decrease as heat content increases. As release time increases, health consequence shows maximum value in 2 hours of release time and then decreases rapidly. As fuel burnup increases, early fatalities decrease rapidly, while cancer fatalities increase rapidly. Both cases show little variation afterward. Early fatality distance is almost same in all fuel turnup history. The information obtained through this research is very useful in developing strategies for reducing offsite consequences when combined with the influence of weather conditions on offsite risks.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.18 no.2
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• pp.61-68
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• 2022

Accurate evaluation of residual stress is important for stress corrosion cracking assessment. In this paper, electron beam welding experiment is simulated via finite element analysis and the sensitivity of the parameters related to the combined heat source model is investigated. Predicted residual stresses arecompared with measured residual stresses. It is found that the welding efficiency affects the size of the tensile residual stress area and the magnitude of maximum longitudinal residual stress. It is also found that the parameter related to the ratio of energy distributed to the two-dimensional heat source has little effect on the size of tthe tensile residual stress area, but affects the size of the longitudinal residual stress in the center of the weld.