• Journal of Power Electronics
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• v.4 no.3
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• pp.138-151
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• 2004

In this paper, a constant frequency phase shifting PWM-controlled voltage source full bridge-type series load resonant high-frequency inverter using the $4^{th}$ generation IGBT power modules is presented for innovative consumer electromagnetic induction heating applications, such as a hot water producer, steamer and super heated steamer. The bridge arm side link passive capacitive snubbers in parallel with each power semiconductor device and AC load side linked active edge inductive snubber-assisted series load resonant tank soft switching inverter with a constant frequency phase shifted PWM control scheme is evaluated and discussed on the basis of the simulation and experimental results. It is proved from a practical point of view that the series load resonant and edge resonant hybrid high-frequency inverter topology, what is called, DE class type, including the variable-power variable-frequency regulation function can expand zero voltage soft switching commutation area even under low output power setting ranges, which is more suitable and acceptable for newly developed induction heated dual pack fluid heaters. Furthermore, even the lower output power regulation mode of this high-frequency load resonant tank inverter circuit is verified so that this inverter can achieve ZVS with the aid of the single auxiliary inductor snubber.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.9
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• pp.455-462
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• 2015

Residential buildings account for a significant portion of the total building-energy usage in Korea, and a variety of research studies on the domestic boiler have therefore been carried out; however, most of these studies examined the boiler itself, whereby the part-load ratio characteristics and the corresponding gas-energy consumption patterns were not analyzed. In this study, the part-load ratio and operating characteristics of a domestic gas boiler were analyzed within a residential building equipped with a radiant floor-heating system; in addition, the energy consumption between condensing and conventional boilers was comparatively analyzed. Our results show that significant portions of the total operating hours, heating load, and energy consumption are in the part-load ratio range of 0 through 40%, whereby the energy consumption was significantly affected by the boiler efficiency under low part-load conditions. These results indicate that the part-load operation of a boiler is an important factor in residential buildings; furthermore, replacing a conventional boiler with a condensing boiler can reduce annual gas-energy usage by more than 20%.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2839-2844
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• 2008

A PEMFC(proton exchange membrane fuel cell) is a good candidate for residential power generation to be cope with the shortage of fossil fuel and green house gas emission. The attractive benefit of the PEMFC is to produce electric power as well as hot water for home usage. Typically, thermal management of vehicular PEMFC is to reject the heat from the PEMFC to the ambient air. Different from that, the thermal management of PEMFC for RPG is to utilize the heat of PEMFC so that the PEMFC can be operated at its optimal efficiency. In this study, dynamic thermal management system is modeled to understand the response of the thermal management system during dynamic operation. The thermal management system of PEMFC for RPGFC is composed of two cooling circuits, one for controling the fuel cell temperature and the other for heating up the water for home usage. Dynamic responses and operating strategies of the PEMFC system are investigated during load changes.

• Journal of Mechanical Science and Technology
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• v.18 no.5
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• pp.820-829
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• 2004

The In-Containment Refueling Water Storage Tank (IRWST), one of the design improvements applied to the APR -1400, has a function to condense the high enthalpy fluid discharged from the Reactor Coolant System (RCS). The condensation of discharged fluid by the tank water drives the tank temperature high and causes oscillatory condensation. Also if the tank cooling water temperature approaches the saturated state, the steam bubble may escape from the water uncondensed. These oscillatory condensation and bubble escape would burden the undue load to the tank structure, pressurize the tank, and degrade its intended function. For these reasons simple analytical modeling and experimental works were performed in order to predict exact tank temperature distribution and to find the effective cooling method to keep the tank temperature below the bubble escape limit (93.3$^{\circ}C$), which was experimentally proven by other researchers. Both the analytical model and experimental results show that the temperature distributions are horizontally stratified. Particularly, the hot liquid produced by the condensation around the sparger holes goes up straight like a thermal plume. Also, the momentum of the discharged fluid is not so strong to interrupt this horizontal thermal stratification significantly. Therefore the layout and shape of sparger is not so important as long as the location of the sparger hole is sufficiently close to the bottom of the tank. Finally, for the effective tank cooling it is recommended that the locations of the discharge and intake lines of the cooling system be cautiously selected considering the temperature distribution, the water level change, and the cooling effectiveness.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.1
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• pp.82-87
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• 2005

The purpose of this study is to suggest the characteristics and actual state of energy consumption by the analysis of energy consumption data in an office building. This study examines and analyzes daily and monthly energy consumption of an office building located in Seoul, Korea regarding type of load and business classification within a building. The results are as follows. 1) Energy consumption of office building for each type of load show similar consumption patterns, regardless of seasons such as cooling period and heating period. 2) Out of all annual energy consumption, consumption for lighting took about $43\;\%,$ general electric Power about $23\;\%,$ emergency power $25\;\%,$ computer center $5\;\%$ and cooling power $4\;\%,$ showing that the consumption for lighting was highest, and the percentage of energy consumption for cooling power for operation of cooling facilities took the lowest percentage. 3) Annual gas consumption used for heating and hot water supply were $38,\;36\;\%$ for officetel and office respectively, and $26\;\%$ for arcade. 4) Electricity consumptions used for cooling power for each use of building, office and officetel recorded in July and August of cooling seasons. Even though it shows different patterns for each month, energy consumption showed unique pattern throughout the cooling seasons.

• Journal of the Korean Solar Energy Society
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• v.29 no.5
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• pp.8-13
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• 2009

Feasibilities of the application of a micro gas turbine cogeneration system to a large size hospital building are studied by estimating energy demands and supplies. The energy demand for electricity is estimated by surveying and sorting the consumption records for various equipment and devices. The cooling heating, and hot water demands are further refined with TRNSYS and ESP-r to generate load profiles for the subsequent operation simulations. The operation of the suggested cogeneration system in conjunction with the load data is simulated for a time span of a year to predict energy consumption and gain profile. The simulation revealed that the thermal efficiency of the gas turbine is about 30% and it supplies 60% of the electricity required by the building. The recovered heat can meet 56% of total heating load and 67% of cooling, and the combined efficiency reaches up to 70%.

• Journal of the Korean Solar Energy Society
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• v.22 no.4
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• pp.1-9
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• 2002

This study is on the design and evaluation of Zero Energy Solar House(ZeSH) including active solar heating system. Various innovative technologies such as super insulation, passive solar systems, super window, ventilation heat recovery system...etc were analyzed by individual and combination for the success of ZeSH. The ESP-r simulation program was used for this. Simulation results shows that almost 77% of heating load can be reduced with the following configuration of 200mm super insulation, super windows, passive solar system and 0.3 ventilation rate per hour. Active solar heating system (ASHS) was designed for the rest of the heating load including hot water heating load. The solar assisted heat pump is used for the auxiliary heating device in order to use air conditioner but not included in this study. The yearly solar fraction is 87% with a solar collector area of $28m^2$. The parametric studies as the influence of storage volume and collector area on the solar fraction was analyzed.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.774-777
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• 2005

In this paper, a constant frequency phase shifting PWM controlled voltage source full bridge-type series load resonant high-frequency inverter using the IGBT power modules is presented for innovative consumer electromagnetic induction heating applications such as a hot water producer, steamer and super heated steamer. The full bridge arm side link passive quasi-resonant capacitor snubbers in parallel with the each power semiconductor device and high frequency AC load side linked active edge inductive snubber-assisted series load resonant tank soft switching inverter with a constant frequency phase shifted PWM control scheme is discussed and evaluated on the basis of the simulation and experimental results. It is proved from a practical point of view that the series load resonant and edge resonant hybrid high-frequency soft switching PWM inverter topology, what is called class DE type. including the variable-power variable-frequency(VPVF) regulation function can expand zero voltage soft switching commutation range even under low output power setting ranges, which is more suitable and acceptable for induction heated dual packs fluid heater developed newly for consumer power utilizations. Furthermore, even in the lower output power regulation mode of this high-frequency load resonant tank high frequency inverter circuit it is verified that this inverter can achieve ZVS with the aid of the single auxiliary inductor snubber.

• Journal of Korean Society on Water Environment
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• v.29 no.2
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• pp.184-195
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• 2013

Urbanization from agricultural/forest areas has been causing increased runoff and pollutant loads from it. Thus, numerous models have been developed to estimate NPS loading from urban area and Long-Term Hydrologic Impact Analysis (L-THIA) model has been used to evaluate effects of landuse changes on runoff and pollutant loads. However, the L-THIA model could not consider rainfall intensity in runoff evaluation. Therefore, the L-THIA model, capable of simulating runoff using 10-minute rainfall data, was applied to the study areas for evaluation of estimated runoff and NPS. The estimated Nash-Sutcliffe coefficient (NSE) values were over 0.6 for runoff, BOD, TN, and TP for most sites and watershed. The calibrated model was further extended to other counties for pollutant load potential evaluation. Pollutant load potential maps were developed and target areas were identified. As shown in this study, the L-THIA 2012 can be used for evaluation runoff and pollutant loads with limited data sets and its estimation could be used in identifying pollutant load hot spot areas for implementation of site-specific Best Management Practices.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.810-814
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• 2009

A experimental study of a high efficiency transport refrigeration system for sliced-raw fish transportation is presented in this paper. The refrigeration system, that is powered by the car engine, is equipped with heat storage for reverse cycle-hot gas defrost; the stored heat is used during defrost cycle of the system. The heat storage has size $400(L){\times}350(W){\times}250(H)\;mm$ and made of fin-tube heat exchanger. System performance and container operating conditions are experimentally investigated and analyzed under cooling and defrosting conditions with heat storage materials. The water is faster about 30% than paraffin in cooling-down time of heat storage materials with load and unload.