• The Journal of Engineering Geology
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• v.28 no.3
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• pp.475-488
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• 2018

This study evaluates geothermal system efficiency in terms of input power and heat exchange volume on the heat-source and load sides, by applying a combined open-closed type loop system comprising a geothermal system and a groundwater well to a cultivation site. In addition, this study analyzes the effects of heating and cooling for a complex geothermal system, by evaluating the temperatures of an external site and a cultivation site during operation. During cooling operations the heat exchange volume on the heat source side, average 90.0kW/h for an open type system with an input of 235L/minute groundwater, and 40.1kW/h for a closed type system with an input of 85L/minute circulating water, for a total average heat exchange volume of 130.1kW/h. The actual heat exchange volume delivered on the load side averages 110.4kW/h. The average EER by analysis of the geothermal system's cooling efficiency is 5.63. During heating operation analysis, the heat exchange volume on the heat source side, average 60.4kW/h in an open type system with an input of 266L/minute groundwater, and 22.4kW/h in closed type system with an input of 86L/minute circulating water, for a total average heat exchange volume of 82.9kW/h. The actual heat exchange volume delivered on the load side averages 112.0kW/h in our analysis. The average COP determined by analysis of the geothermal system's heating efficiency is 3.92. Aa a result of the tradeoff between the outside temperature and the inside temperature of the production facility and comparing the facility design with a combined well and open-closed loops geothermal(CWG) system, we determine that the 30RT-volume CWG system temperature are lower by $3.4^{\circ}C$, $6.8^{\circ}C$, $10.1^{\circ}C$ and $13.4^{\circ}C$ for ouside temperature is of $20^{\circ}C$, $25^{\circ}C$, $30^{\circ}C$ and $35^{\circ}C$, respectively. Based on these results, a summer cooling effect of about $10^{\circ}C$ is expected relative to a facility without a CWG system as the outside temperature is generally ${\geq}30^{\circ}C$. Our results suggest that a complex geothermal system provides improvement under a variety of conditions even when heating conditions in winter are considered. Thus It is expected that the heating-cooling tradeoffs of complex geothermal system are improved by using water screen.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.7 no.1
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• pp.6-17
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• 1998

Tooth bleaching was being done more than 100 years ago, but the standard for vital tooth bleaching for the last quarter century has been the use of hydrogen peroxide with heat or with a combination of heat and light. The major disadvantages of this process are high cost, unpredictability of results, and patient discomfort. In March, 1989, the dental world was introduced to a new vital tooth bleaching process by Haywood and Heymann in their article "Nightguard vital bleaching(NGVB)." Interestingly enough, this simple technique could have been developed years ago if we had known about the chemical effects of carbamide peroxide on tooth structure. NGVB has created a resurgence in the area of bleaching, primarily because of its relative ease of application, the safety of the materials used, low cost, and the high percentage of successful treatments. This article was to explain simply about all around NGVB(etiology of stains, bleaching chemicals and mechanisms, bleaching effectiveness, side effect, documentation, indications, treatment therapy, laboratory procedure, case reports)

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.352-357
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• 2007

The objective of this study is to find the optimal set-point of a hybrid Plant, which is combined by renewable energy plant of the GSHP(Ground Source Heat Pump) and the conventional plant(chiller, boiler). The work presented in this study was carried out by using the EnergyPlus(Version 2.0). In order to validate the simulation model, field data were measured from a building. The GSHP was used as a base plant and the conventional plant as the assistant plant. Various temperatures were controlled (zone summer set-point, zone winter set-point, chilled water temperature, hot water temperature) to find the optimal set-point temperature of the system. The influence of the various set-points were analyzed seasonally.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.4
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• pp.382-389
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• 2012

Power generation cycle using ammonia-water mixture as working fluid has attracted much attention because of its ability to efficiently convert low-temperature heat source into useful work. If an ammonia-water power cycle is combined with a power cycle using liquefied natural gas (LNG), the conversion efficiency could be further improved owing to the cold energy of LNG at $-162^{\circ}C$. In this work parametric study is carried out on the thermodynamic performance of a power cycle consisted of an ammonia-water Rankine cycle as an upper cycle and a LNG cycle as a bottom cycle. As a driving energy the combined cycle utilizes a low-temperature heat source in the form of sensible heat. The effects on the system performance of the system parameters such as ammonia concentration ($x_b$), turbine 1 inlet pressure ($P_{H_1}$) and temperature ($T_{H_1}$), and condenser outlet temperature ($T_{L_1}$) are extensively investigated. Calculation results show that thermal efficiency increases with the increase of $P_{H_1}$, $T_{H_1}$ and the decrease of $T_{L_1}$, while its dependence on $x_b$ has a downward convex shape. The changes of net work generation with respect to $P_{H_1}$, $T_{H_1}$, $T_{L_1}$, and $x_b$ are roughly linear.

• Journal of Institute of Convergence Technology
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• v.2 no.2
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• pp.59-65
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• 2012

This paper presents the study on applications of a surplus heat source. The heat is generated while hardwood charcoals are produced. We measure the temperature of the generated heat and analyze whether it can heat water or not. The analytic results show that the generated heat is useful as one of heat sources. In agricultural methods using a vinyl house, heating expenses will be saved by 10~20% when the surplus heat source is used.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.2 no.2
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• pp.1-8
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• 2006

The objective of the present study is to investigate the load delivery characteristics of a hybrid-renewable energy system with geothermal and solar heat sources for hot water, heating and cooling of a residential house in Korea. The hybrid energy system consists of ground source heat pump of 2 RT for cooling with a 150 m vertical U-bend ground heat exchanger, solar collectors of 4.8 m2 and gas fired backup boiler. The averaged coefficient of performance of geothermal module during cooling and heating seasons are evaluated as about 4.5 and 3.8, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.3
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• pp.170-177
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• 2009

In the present study, a finite element analysis of conjugate heat transfer problem inside a cavity with a heat-generating conducting body, where constant heat flux is generated, is conducted. A conduction heat transfer problem inside the solid body is automatically coupled with natural convection inside the cavity by using a finite element formulation. A finite element formulation based on SIMPLE type algorithm is adopted for the solution of the incompressible Navier-Stokes equations coupled with energy equation. The proposed algorithm is verified by solving the benchmark problem of conjugate heat transfer inside a cavity having a centered body. Then a conjugate natural heat transfer problem inside a cavity having a heat-generating conducting body with constant heat flux is solved and the effect of the Rayleigh number on the heat transfer characteristics inside a cavity is investigated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.9
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• pp.881-888
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• 2004

Control algorithms for a dual source chiller air conditioning system were developed. These are control algorithms for the supply air temperature control, the supply header chilled water temperature control, the chiller chilled water temperature control, and the cooling tower water temperature control. These algorithms were analyzed by using a dynamic simulation program. Simulation results showed the energy savings and the satisfactory controls of an absorption and centrifugal chiller air conditioning system. Therefore, control algorithms developed for this study may effectively be used for the improved controls of the dual source chiller air conditioning system.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.16 no.4
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• pp.1-8
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• 2020

For a central cooling system of a medical facility composed of absorption chiller and screw chiller, the study was conducted on how to minimize the energy cost. In consideration of the energy cost, the optimal operation method in which the operation method of the heat source is changed according to the size of the cooling load was derived through simulation analysis. When applying the optimal operation method, the indoor environment, energy consumption, and energy cost were analyzed and compared with the reference operation method.

• Journal of the Korean Institute of Gas
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• v.18 no.2
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• pp.41-47
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• 2014

In this work a thermodynamic performance analysis is carried out for a combined cycle consisted of an organic Rankine cycle (ORC) and a LNG cycle. The combined system uses a low grade waste heat in the form of sensible energy and the LNG cold energy is used for power generation as well as for heat sink. The effects of the key parameters of th system such as turbine inlet pressure, condensation temperature and source temperature on the characteristics of system are throughly investigated. The simulation results show that the thermodynamic performance of the combined system can be significantly improved compared to the normal ORC which is not using the LNG cold energy.