• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.3-8
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• 1998

The industrial revolution in England was based on the manufacturing systems by the power of water mill and rapidly progressed by the innovation of steam engine. It is no exaggeration to say that today's civilization is realized by the development of various types of power machinery, namely fluid machinery and heat engine. The electric energy is converted mainly from thermal energy (mainly steam) of mineral oil, coal and nuclear fuel through generator connected with steam turbine which is a kind of power machinery. There are various types of power machinery as shown in Tables 1a and 1b. They are classified into two types by use. One is absorption type of fluid and/or thermal energy, for examples, windmill and heat engine. The other is provision type of the energies for examples, pump, compressor and propulsion. By flow type, they are also classified by two types, turbo type and positive-displacement type. The turbo type began from water mill and windmill and evolve to steam turbine and finally to gas turbine. The positive-displacement type started from reciprocating water pump and developed into steam engine and changed to reciprocating combustion engine. The pumps and motors used in oil hydraulic system for power control are also positive-displacement type.

• Journal of Hydrogen and New Energy
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• v.22 no.2
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• pp.152-160
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• 2011

The electromagnetic characteristics of FCEVs (fuel cell electric vehicles) are much different from the existing combustion engine cars as well as hybrid, plug-in-hybrid, and pure electric vehicles due to the high voltage/current generated by a fuel cell stack which uses a compressed hydrogen gas reacted with oxygen. To operate fuel cell stack efficiently, BOP (Balance of Plant) which is consisted of many motors in water pump, air blower, and hydrogen recycling pump as well as inverters for these motors is essential. Furthermore, there are also electric systems for entertainment, information, and vehicle control such as navigation, broadcasting, vehicle dynamic control systems, and so on. Since these systems are connected by high voltage or general cables, EMC (Electromagnetic compatibility) analysis for high voltage and general cable of FCEV is the most important element to prevent the possible electric functional safety errors. In this paper, electromagnetic fields by high voltage and general cables for FCEVs is studied. From numerical analysis results, total time harmonic electromagnetic field strength from high voltage and general cables have difference of 13~16 dB due to ground effect by impedance matching. The EMI results of FECV at 10 m distance shows difference of 41 dB at 30 MHz and 54 dB at 230 MHz compared with only general cable routing.

• Agricultural and Biosystems Engineering
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• v.6 no.1
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• pp.22-26
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• 2005

A wind-heat generation system was developed and the system consisted of an electric motor, a heat generation drum, a heat exchanger, two circulation pumps and a water storage tank. The heat generation drum is an essential element determining performance of the system. Frictional heat was generated by rotation of a rotor in the drum filled with a working fluid, and the heat stored in the fluid was used to increase water temperature through the heat exchanger. Effects of some factors such as rotor shape, kind and amount of working fluid, rotor rpm and water flow rate in the heat exchanger, affecting the system performance were investigated. Amounts of heat generated were varied, ranging from 126,000 to 32,760 kJ/hr, depending on combination of the factors. Statistical analysis using GLM procedure revealed that the most influential factor to decide the system performance was amount of the fluid in the drum. Experiments showed that the faster the speed of the rotor, the greater heat was obtained. The greatest efficiency of the heat generation system, electric power consumption rate vs gained heat amount of water, was about 70%. Though the heat amount was not enough for plant bed heating of a 0.1-ha greenhouse, the system would be promising if some supplementary heat source such as air- water heat pump is added.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.4
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• pp.402-412
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• 1995

A new energy conversion system which converts wind energy directly to heat instead of transforming it to electric power beforehand is suggested in this study. The new energy conversion system is composed of two big parts divided by their functions. One of them is a wind turbine part, and another is the heat energy conversion part. The object of this study is confined only to the heat energy conversion part, so the wind turbine is replaced with an electric motor for the convenience of experiment. In the experimental process, pressure difference at the hydraulic pump, revolution speed of the hydraulic pump, temperature at a few points on the oil circuit and the water circuit are measured at time intervals of five minutes. And integral values of input energy to the system and stored energy in the system is investigated.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.776-781
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• 2001

To enhance thermal efficiency of thermal facility through recovery of low and medium temperature waste heat, 1MW organic Rankine cycle system was designed and developed. The exhaust gases of $175^{\circ}C$ at two 100MW power plants in pohang steel works were selected as the representative of low and medium temperature waste heat in industrial process for the heat source of the organic Rankine cycle system. HCFC-123, a kind of harmless refrigerant, was chosen as the working fluid for Rankine cycle. The organic Rankine cycle system with selected exhaust gases and working fluid was designed and constructed. From the operation, it was confirmed that the organic Rankine cycle system is available for low and medium temperature waste heat recovery in industrial process. The optimum operating manuals, such as heat-up of hot water, turbine start-up, and the process of electric power generation, were derived. However, electric power generated was not 1MW as designed but only 670kW. It is due to deficiency of pump capacity for supply of HCFC-123. So it is necessary to increase the pump capacity or to decrease the pressure loss in pipe for more improved HCFC-123 supply.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.403-407
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• 2016

In general, drum-type boilers are designed for base load duty and applied under constant pressure operation mode. Recently, however conditions often occur that even drum-type boilers have to operate at partial load conditions. A feasibility study on adopting the sliding pressure operation for drum-type boiler was conducted, and corresponding performance changes and effects on the equipment were analyzed by utilizing a process simulation model. As a result, the conclusion was reached that drum type boilers are able to adopt the sliding pressure operation and can improve of net efficiency at part load operation in spite of the Rankine cycle efficiency reduction due to the decreases in main steam pressure. Because of thank to improvement of high pressure turbine stage-1 internal efficiency and power savings of boiler feed water pump. The sliding pressure operation is advantageous in terms of stress level relief for boiler tube as well as maintaining the rating steam temperature at part load condition. However, cautions are required because the drum boilers have poor dynamic response characteristics which may get worse during the sliding pressure operation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.10
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• pp.387-393
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• 2016

A ground source heat pump system maintains a constant efficiency due to its stable heat source and radiant heat temperature which provide a more effective thermal performance than that of the air source heat pump system. As an eco-friendly renewable energy source, it can reduce electric power and carbon dioxide. In this study, we analyzed one year of data from a web based remote monitoring system to estimate the thermal performance of GSHP with the capacity of 3RT, which is installed in a low energy house located in Daejeon, Korea. This GSHP system is a hybrid system connected to a solar hot water system. Cold and hot water stored in a buffer tank is supplied to six ceiling cassette type fan coil units and a floor panel heating system installed in each room. The results are as follows. First, the GSHP system was operated for ten minutes intermittently in summer in order to decrease the heat load caused by super-insulation. Second, the energy consumption in winter where the system was operated throughout the entire day was 7.5 times higher than that in summer. Moreover, the annual COP of the heating and cooling system was 4.1 in summer and 4.2 in winter, showing little difference. Third, the outlet temperature of the ground heat exchanger in winter decreased from $13^{\circ}C$ in November to $9^{\circ}C$ in February, while that in summer increased from $14^{\circ}C$ to $17^{\circ}C$ showing that the temperature change in winter is greater than that in summer.

• Journal of Biosystems Engineering
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• v.27 no.6
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• pp.565-572
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• 2002

In order to control the root-zone temperature of greenhouse crops in the hydroponics at hot and cold season, heat pump system for cooling and heating was built and tested in this work. The system was air-to-water type and vapour compression type. The heating and cooling mode was selected by the four way valve. Capacity of the compressor was 3.75㎾ and heat transfer area of the evaporator and the condenser were 3.05㎡ and 0.6㎡, respectively. According to the performance test, it could supply heat of 42,360 to 64,372kJ/h depending on the water circulation rate of 600 to 1,500ℓ/h, respectively, when indoor air temperature was 10∼20$\^{C}$. COP of heat pump system was 3.0 to 4.0 in the heating mode. But, COP of the cooling mode was 1.3 to 2.1 at indoor temperature of 20∼35$\^{C}$. The feasibility test in the greenhouse the developed heating and cooling system was installed, showed that the heating cost of the developed system was only about 13% of that of the conventional heating system. The heating cost of the developed system was 367won/day(electric consumption 9.7㎾h/day), while that of the conventional system was 2,803won/day(oil consumption 7.7ℓ/day) at the same heating mode.

• Journal of Biosystems Engineering
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• v.43 no.4
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• pp.342-351
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• 2018

Purpose: Recently, an increasing number of farms have been cultivating shiitake mushrooms using a sawdust substrate and a cooler/heater. In this study, an attempt was made to develop an environmental control system using a heat pump for cultivating high-quality shiitake mushrooms. Methods: An environmental control system, consisting of an air-to-water type heat pump, a thermal storage tank, and a radiator in a variable opening chamber, was designed and fabricated. The system was also installed in the cultivation facility of a farm cultivating shiitake mushrooms so as to compare the proposed control system with a conventional environmental control system using a cooler-condensing unit and an electric hot water boiler. Results: The uniformity of the environment was analyzed through environment measurements taken at several positions inside the cultivation facility. It was determined that the developed environmental control system is able to control the variations in temperature and relative humidity to within 1% and 3%, respectively. In addition, a maximum temperature difference of $30^{\circ}C$ (maximum of $35^{\circ}C$, minimum of $5^{\circ}C$) and a maximum relative humidity difference of 30% (maximum of 90%, minimum of 60%) can be attained within 30 min inside the cultivation facility through the cooling of the heat pump and heating of the radiator in a variable opening chamber. Thus, the developed control system can be used to cultivate high-quality shiitake mushrooms more effectively than a conventional cooler and heater. Conclusions: In comparison with a conventional environmental control system, the developed system decreased the yield of ordinary mushrooms by 65%, and increased that of high-quality mushrooms by 217%. This corresponds to a 16% increase in gross farm income. Consequently, the developed system is expected to improve the income of shiitake mushroom cultivating farms.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.4
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• pp.499-505
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• 2009

Many other countries have investigated the residual sludge treatment process to save the existing water resource and produce the high suspended solid concentration sludge. There are various methods for concentrating residual sludge, but the membrane system has received the most interest for its efficiency. The objective of this study was to evaluate the application of membrane filtration system for the residual sludge treatment. The experiment equipment was composed of Lab scale Crossflow tubular membrane filtration system. Generally, crossflow operation mode demands high electric cost mainly for the pump energy. So to cut off electric cost, very low Crossflow velocity was used in this experiment. Results confirmed that suspended solid concentration of residual sludge could be concentrated to 57,000mg/L in low Crossflow velocity tubular membrane system,. This concentration can be directly injected into the dehydrator. Based on the results, we know that the Crossflow tubular membrane system should be replaced conventional residual sludge treatment system.