• Transactions of the Korean hydrogen and new energy society
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• v.25 no.3
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• pp.297-304
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• 2014

The purpose of this study is to evaluate the experimental performance characteristics of a water-to-water geothermal heat pump featuring a vapor refrigerant injection for the production of hot water. The performance of geothermal heat pump with a vapor injection was evaluated by comparing with that of a conventional geothermal heat pump without a vapor injection. For heating operation, the geothermal heat pump with a vapor injection is superior in COP and heating capacity. The vapor injection was more effective for supplying hot water while overloading. The vapor injection was effective for the improvement of the cooling capacity. However, the vapor injection was not effective for the increasing of COP according to the increased input of a compressor. The advantage of vapor injection in water-to-water geothermal heat pump become disappeared while cooling operation with lower part loading.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1329-1334
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• 2004

The most compact and convenient pulse tube cryocooler for practical applications is the coaxial type. It can replace Stirling cryocooler without any change to the Dewar or the connection to the cooled devices. The experimental results of the coaxial inertance tube pulse tube cryocooler for cooling superconductor RF filter are presented in this paper. To find optimal conditions of inertance tube pulse tube cryocooler, no load temperature according to the variations of inertance tube volume, reservoir volume are measured, and the cool down characteristics at the particular conditions are presented. In case of the coaxial type inertance tube pulse tube refrigerator, cool down time is the lowest in the inertance tube diameter of 1.3 mm and inertance tube length of 1900 mm and lowest temperature is 112K. This results are not satisfactory for practical applications. So, We propose vacuum insulation between regenerator and pulse tube in the Stirling type coaxial pulse tube cryocooler. Stirling type coaxial pulse tube cryocooler with the vacuum insulation between regenerator and pulse tube was designed and manufactured by KIMM(Korea Institute of Machinery and Materials). The optimal conditions will be tested for Stirling type coaxial pulse tube cryocooler with the vacuum insulation between regenerator and pulse tube.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.169-173
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• 2008

Stirling engine is a promising heat engine with a high efficiency, muti-fuel capability, low emission, quiet operation, very low maintenance and long life. As one of the promising applications, solar power system based on the Stirling dish, providing net solar-to-electric conversion efficiencies reaching 30%, can operate as stand-alone units in remote locations or can be linked together in groups to provide utility-scale power. This paper introduced a new Scroll-type Stirling engine, being developed for solar power, superior to conventional Stirling engines. The Scroll-type Stirling engine is characterized as traits of continuous and wholly separated compression and expansion; one-way flow system; direct cooling and heating the fluid in the working spaces through the extensive inner surfaces of scroll wraps. All theses traits contribute to achieving thermodynamic cycle closer to the ideal Stirling cycle (exactly speaking, Ericsson cycle).

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.993-994
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• 2011

This paper presents the characteristic analysis of thermal behavior of a single-phase line-start permanent magnet motor(LSPM) for high-efficiency design. By analyzing of thermal behavior, it can consider demagnetization characteristics of permanent magnets. In addition, by calculating the allowable current density it will be able to reduce the size of the stator. For this reason single-phase LSPM is necessary to examine the thermal analysis. Thermal analysis was performed using heat source mapping, and it is verified by finite element method.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.3
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• pp.44-50
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• 1997

This paper describes an indirect sensing method for the rotor flux position of interior permanent magnet (IPM) brushless DC motors. The phase inductances of an IPM motor vary appreciably according to the rotor position. The waveform characteristics of the terminal voltage of IPM brushless DC motors is analysed and a simple and practical method for indirect sensing of the rotor position is proposed. A compact and economical sensorless drive is implemented and tested using a 87c196mc 16-bit one-chip microprocessor. The experimental results show the validity of the proposed method. The drive is applied to drive a compressor of air-conditioner and works well from 1,200 to 6,600 [rpm].

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.3
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• pp.285-293
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• 1998

This paper presents an experimental study on condensing heat transfer characteristics of R-22 alternative refrigerants, R-290 and R-410a on water sources heat pump. The apparatus mainly consisted of vapor pump condenser used to the test section evaporator manual expansion valve and measuring device. Test section constructed a smoothed tube of 10.07 mm ID and 12.7mm OD with a total length 6,300 mm was horizontal double pipe counterflow condenser. The refrigerants R-22, R-290 and R-410a were cooled by a coolant circulated in a surrounding annulus. Experimental range of mass velocities was changed from about 100 to 300 kg/($m^2$.s) and inlet quality 1.0 The credibility of experimental apparatus was 6 percent between heating capacity and cooling capacity added to compressor shaft power. The condensing heat transfer coefficients were increased with increasing mass velocity. However in case of R-290 they were more increasing than those of R-410a and R-22 Comparing the heat transfer coefficient between the experimental data and other's data the Cavallini-Zecchin's data was revealed to more similar prediction of author's experimental results on the average heat transfer coefficients.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.743-749
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• 2010

The primary object of this study was to develop the control algorithm and program for automatic submersible buoy which is free to move vertically within the water column by adjusting weight and buoyancy forces by air control. The experiment was performed to validate the usefulness of the program in the indoor water tank. In the experiment, the automatic submerging and surfacing of the buoy were controlled by water-pressure gauge and air control system. The buoy is raised by injecting compressed air from a compressor and then is lowered by releasing the air. The submerging and surfacing characteristics of the buoy calculated with the numerical model were similar to measurements obtained with the experiment. It was concluded that the algorithm and program could be useful in analyzing various parameters and submerging mechanisms required to design new type of automatic submersible fish cage system.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.83-86
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• 2006

In this study, the syngas producing facility that consists of pulverized coal feeding/gasification and hot gas clean-up system was tested for Indonesian subbituminous coal. And the DME conversion facilities have been developed and tested for converting syngas to DME by reactions with catalysts. So, the entrained-bed slagging type pi lot scale coal gasifier was operated normally in the temperature range of $1,400{\sim}1,450^{\circ}C,\;7{\sim}8kg/cm^2$ pressure. And Roto middle coal produced syngas that has a composition of $36{\sim}38%$ CO, $14{\sim}16%\;H_2,\;and\;5{\sim}8%\;CO_2$. Particulates in syngas were 99.8% removed by metal filters. $H_2S$ composition in syngas was also desulfurized by the Fe chelate system to yield less than 0.1 ppm level. When the clean syngas $70{\sim}100 Nm^3/h$ was provided to DME conversion rector, normally operated in the temperature range of $230{\sim}250^{\circ}C$ and $60kg/cm^2$ pressure, 4.5% DME was yielded.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.4
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• pp.280-284
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• 2002

This paper presents computer simulations of the stacking and transferring system for the fast freeform fabrication system. The stacking and transferring system is essential for the fast freeform fabrication system and its stable motion is very important for consistent stacking of the cut slices. The stacking and transferring system can be modeled as a pneumatic system. The system consists of air compressor, the control valve, and the cylinder. The governing parameters have been changed and the simulation results are shown to predict the time response of the system. The results show some parameters should be correctly tuned to obtain stable system response.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.10
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• pp.679-686
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• 2007

The cooling load in winter season is significant in many commercial buildings and hotels because of the usage of office equipments and the high efficiency of wall insulation. The development of a multi-heat pump that can cover heating and cooling simultaneously for each indoor unit is required. In this study, a 4-room simultaneous heating and cooling heat pump system was designed and its performance was measured at each operating mode. The system used R-410A and adopted variable speed compressor. The problems on the designed system were analyzed and defined. In addition, the solutions of the problems were suggested to improve system efficiency and to obtain the stable operation.