• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1367-1373
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• 2011

This research concerns the development of a compression/absorption high-temperature hybrid heat pump that uses a natural refrigerant mixture. Heat pumps based on the compression/absorption cycle offer various advantages over conventional heat pumps based on the vapor compression cycle, such as large temperature glide, temperature lift, flexible operating range, and capacity control. In this study, a lab-scale prototype hybrid heat pump was constructed with a two-stage compressor, absorber, desorber, desuperheater, solution heat exchanger, solution pump, liquid/vapor separator, and rectifier as the main components. The hybrid heat pump system operated at 10-kW-class heating capacity producing hot water whose temperature was more than $90^{\circ}C$ when the heat source and sink temperatures were $50^{\circ}C$. Experiments with various $NH_3/H_2O$ mass fractions and compressor/pump circulation ratios were performed on the system. From the study, the system performance was optimized at a specific $NH_3$ concentration.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.19 no.3
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• pp.14-22
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• 2023

Steel-pipe civil structures, including steel-pipe energy piles and cast-in-place piles (CIPs), utilize steel pipes as their primary reinforcements. These steel pipes facilitate the circulation of a working fluid through their annular crosssection, enabling heat exchange with the surrounding ground formation. In this study, the cooling performance of a ground source heat pump (GSHP) system that incorporated steel-pipe civil structures was investigated to assess their applicability. First of all, the thermal performance test was conducted with steel-pipe CIPs to evaluate the average heat exchange amount. Subsequently, a GSHP system was designed and implemented within an office container, considering the various types of steel-pipe civil structures. During the performance evaluation tests, parameters such as the coefficient of performance (COP) and entering water temperature (EWT) were closely monitored. The outcomes indicated an average COP of 3.74 for the GSHP system and the EWT remained relatively stable throughout the tests. Consequently, the GSPH system demonstrated its capability to consistently provide a sufficient heat source, even during periods of high cooling thermal demand, by utilzing the steel-pipe civil structures.

• New & Renewable Energy
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• v.5 no.3
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• pp.32-39
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• 2009

The Samcheonpo ocean small hydropower plant (SHP) has a special feature of using marginal hydraulic head of circulating water system of fossil fuel power plant as a power source and having the characteristics of general hydropower generation and tidal power generation as well. Also, it contributes to reducing green house gases and developing clean energy source by recycling circulating water energy otherwise dissipated into the ocean. The efficiency of small hydropower plant is directly affected by effective head and flow rate of discharged water. Therefore, the efficiency characteristics of ocean hydropower plant are analyzed with the variation of water level and flow rate of discharged water, which is based on the accumulated operation data of the Samcheonpo hydropower plant. After the start of small hydropower plant operation, definite rise of water level was observed. As a result of flow pattern change from free flow to submerged flow, the instability of water surface in overall open channel is increased but it doesn't reach the extent of overflowing channel or having an effect on circulation system. Performance evaluation result shows that the generating power and efficiency of small hydropower exceeds design requirements in all conditions. Analysis results of CWP's water flow rate verify that the amount of flowing water is measured less and the highest efficiency of small hydropower plant is achieved when the effective head has its maximum value. In conclusion, efficiency curve derived from water flow rate considering tidal level shows the best fitting result with design criteria curve and it is verified that overall efficiency of hydropower system is satisfactory.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.8 s.251
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• pp.764-771
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• 2006

Knowledge of ground thermal properties is most important for the proper design of large BHE(borehole heat exchanger) systems. Thermal response tests with mobile measurement devices were first introduced in Sweden and USA in 1995. Thermal response tests have so far been used primarily for in insitu determination of design data for BHE systems, but also for evaluation of grout material, heat exchanger types and ground water effects. The main purpose has been to determine insitu values of effective ground thermal conductivity, including the effect of ground-water flow and natural convection in the boreholes. Test rig is set up on a small trailer, and contains a circulation pump, a heater, temperature sensors and a data logger for recording the temperature data. A constant heat power is injected into the borehole through the pipe system of test rig and the resulting temperature change in the borehole is recorded. The recorded temperature data are analysed with a line-source model, which gives the effective insitu values of rock thermal conductivity and borehole thermal resistance.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.5
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• pp.615-622
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• 2015

As the development of high efficiency and high flux density LEDs, the trend of illumination lamp industry transfers from conventional-lamps to the LED-lamps. For energy efficiencies, LED lamps are superior to the conventional lamps, but they have heat problems. Especially, the heat problems are severe for the high luminance lamps. They degrade the soldering point of the metal PCB, and shorten the life cycle of LEDs. So, the solution of the heat sinking is very important to develop high luminance LED lamps. This study suggested a new method to solve the heat problems for high luminance LED lamps, and developed a LED lamp which has 1200W power. In this study, a water jacket is installed to the LED lamp, and the cooing water is circulated by a water pump.

• Journal of Chest Surgery
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• v.10 no.2
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• pp.299-314
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• 1977

Clinical experience on 16 cases of open heart surgery under the extracorporeal circulation with mild or moderate hypothermia and partial hemodilution technique at the National Medical Center during the period from June 1976 to October 1977. Nine of sixteen were congenital heart disease and seven were acquired heart disease. The age of the patient ranged between 6 and 48 years. The body weight varied from 18.5kg to 60kg and body surface area 0. 79-1.70m2. The average priming volume of pump oxygenator was 2080 ml, which was consisted fresh ACD blood, buffered Hartmann`s solution, Mannitol, 50% dextrose in water and Vit. C. The average hemodilution rate was 27%. The average flow 2.3 L/min/m2 or 80 ml/min and the duration of perfusion varied from 31 min to 270 min with average of 107 min. The perfusion was carried out under the mild or moderate hypothermia using core cooling alone in 10 cases, core cooling and local myocardial cooling with $0-4^{\circ}C$ physiologic saline in 2 cases. From a hemodynamic point of view, the blood pressure dropped down around 80 mmHg after the initiation of perfusion follwed by increase to safety level and stable during the perfusion. The central venous pressure remained within normal limits. In most cases, hemoglobin and hematocrit decreased during and after the perfusion. Hemogiobin level was decreased, average of 20.6 %, hematocrit 18.6%, pletelets 55% postoperatively. Plasma hemoglobin increased moderately, from preperfusion average valve of 7.79 mg % to post-perfusion value of 54.7 mg %. Electrolytes changes during cardiopulmonary bypass showed definite hypokalemia but changes of Na, Ca were not definite. Arterial blood gas analysis during cardiopulmonary bypass suggested that the metabolic acidosis which was accompanied by respiratory alkalosis which was corrected postoperatively. As the opera tive complication, transient hemoglobinuria in 4 cases and neurological signs in 2 cases were all cured. There were 2 death cases and operative mortality rate was 12.5%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.37-43
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• 2015

Evaporative cooling is a very effective way for exhaust heat recovery that uses both latent heat and sensible heat. This study investigated the performance of a heat recovery system using evaporative cooling. The experimental apparatus comprised a plastic heat exchanger, a water spray nozzle, an air blowing fan, a water circulation pump, and measuring sensors for the temperature, humidity, and flow rate. The effectiveness of the sensible heat recovery without evaporation was measured and compared with that of the total heat recovery with evaporation. The effectiveness of the sensible and total heat recoveries decreased as the air flow rate increased, and a much higher effectiveness was obtained with the counterflow arrangement in both cases. For total heat recovery, the effectiveness increased with the water flow rate, and the parallel flow arrangement was found to be more sensitive to the water flow rate than the counterflow arrangement.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.276-282
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• 2017

The aim of this study was to compare and analyze air temperature and humidity distribution and energy consumptions according to using air circulation fans in single-span greenhouses. The greenhouses located in Cheongnam-myeon, Cheongyang-gun, Chungcheongnam-do, Korea. There were cherry tomatoes in the greenhouses and the size of greenhouses was as follows;ridge height : 3.2 m, wide : 6 m, length : 95 m. The heating system was composed of a hot-water boiler and 6 FCUs(Fan Coil Unit)-4 FCUs were on bottom with duct and 2 FCUs were installed at 2.0 m. A total of 18 air circulation fans(impeller's diameter : 230 mm) were bilaterally arranged in 2 rows in the experimental greenhouse. The sensors for measuring air temperature and humidity were located at a quarter and three quarters of a length. The height of sensors were 0.8 m, 1.8 m. To calculate energy consumption in greenhouses, water temperature at inlet and outlet in a water pump, volume of water were measured. Form February 3rd to March 23th, temperature, humidity and energy consumptions were measured during heating time(6pm~7am). In a greenhouse without fans, the average differences of temperature and humidity were $0.75^{\circ}C$, 2.31%, respectively. The operation of fans showed their differences to $0.42^{\circ}C$, 1.8%. The standard deviation of temperature and humidity between measuring points in the greenhouse with fans was lower than the greenhouse without fans. Total energy consumptions in a greenhouse without fans were 4,673 kWh. In the greenhouse with fans, the total energy consumptions were 4,009 kWh. The energy consumptions in a greenhouse with fans 14.2% were less than the greenhouse without fans. Therefore, air circulation makes temperature and humidity uniform and saves energy consumptions for heating.

• Journal of IKEEE
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• v.27 no.1
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• pp.122-126
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• 2023

In this paper, a control system for a complex microbial incubator was proposed. The proposed control system consists of a control unit, a communication unit, a power supply unit, and a control system of the complex microbial incubator. The controller of the complex microbial incubator is designed and manufactured to convert analog signals and digital signals, and control signals of sensors such as displays using LCD panels, water level sensors, temperature sensors, and pH concentration sensors. The water level sensor used is designed and manufactured to enable accurate water level measurement by using the IR laser method with excellent linearity in order to solve the problem that existing water level sensors are difficult to measure due to foreign substances such as bubbles. The temperature sensor is designed and used so that it has high accuracy and no cumulative resistance error by measuring using the thermal resistance principle. The communication unit consists of two LAN ports and one RS-232 port, and is designed and manufactured to transmit signals such as LCD panel, PCT panel, and load cell controller used in the complex microbial incubator to the control unit. The power supply unit is designed and manufactured to supply power by configuring it with three voltage supply terminals such as 24V, 12V and 5V so that the control unit and communication unit can operate smoothly. The control system of the complex microbial incubator uses PLC to control sensor values such as pH concentration sensor, temperature sensor, and water level sensor, and the operation of circulation pump, circulation valve, rotary pump, and inverter load cell used for cultivation. In order to evaluate the performance of the control system of the proposed complex microbial incubator, the result of the experiment conducted by the accredited certification body showed that the range of water level measurement sensitivity was -0.41mm~1.59mm, and the range of change in water temperature was ±0.41℃, which is currently commercially available. It was confirmed that the product operates with better performance than the performance of the products. Therefore, the effectiveness of the control system of the complex microbial incubator proposed in this paper was demonstrated.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.581-586
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• 2009

Knowledge of ground thermal properties is most important for the proper design of large scale BHE(borehole heat exchanger) systems. The type, pipe size and thermal performance of the BHE is highly dependent on the ground source heatpump system-efficiency and instruction cost. Thermal response tests with mobile measurement devices were developed primarily for insitu determination of design data for large diameter BHE for triple-U spacer apply. The main purpose has been to determine insitu values of effective ground thermal conductivity and thermal resistance, including the effect of ground-water flow and natural convection in the boreholes. The test rig is set up on a some trailer, and contains a circulation pump, a inline heater, temperature sensors, flow meter, power analysis meter and a data logger for recording the temperature, fluid flow data. A constant heat power is injected into the borehole through the tripl-U pipes system of test rig and the resulting temperature change in the borehole is recorded. The recorded temperature data are analysed with a line-source model, which gives the effective insitu values of rock thermal conductivity and borehole thermal resistance of large diameter BHE for spacer apply.