• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.3
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• pp.218-225
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• 1990

Studies on the performance of a heat pump using non-azeotropic refrigerant mixtures are done. In order to estimate the thermodynamic properties for the selected non-azeotropic refrigerant mixtures including R22/R152a, R22/R142b, R22/R114 and R13B1/R152a, Peng-Robinson equation of state is adopted. The pressure-enthalpy diagram and the temperature-entropy diagram are plotted for each refrigerant mixture. Considerations on the capacity modulation for the heat pump system using refrigerant mixtures are taken into. Results show that when the heating load varies, the possibility for the capacity modulation is found in the heat pump system using a compressor with constant volume flow rate. Under a constant heating capacity condition in the heat pump system, the coefficient of performance increases when the refrigerant mixtures are used. The volume flow rate decreases as the mass fraction of lower boiler increases in this case.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.731-736
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• 2006

Groundwater heat pump (GWHP) system has been expected to achieve the higher coefficient of performance (COP) and more energy-saving than the conventional air-source heat pump (ASHP) system. Its performance significantly depends on the characteristics of groundwater and the underground thermal properties. Furthermore, there is a large difference of COP in utilizing groundwater between as a heat resource and as a thermal storage medium. For properties of groundwater there is suitable utilizing system. However, many of GWHP systems have not been considered sufficiently such properties. This research describes optimization of GWHP system according to the properties of groundwater based on 3D numerical heat and water transport simulation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.8
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• pp.605-611
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• 2012

The objective of this study is to investigate the influence of the cooling performance for a water-to-water 10 RT ground source heat pump by using the water switching and refrigerant switching method. The test of water-to-water ground source heat pump was measured by varying the compressor speed, load side inlet temperature, and ground heat source side temperature. The cooling capacity and refrigerant mass flow rate of the heat pump increased with increasing ground heat source temperature. But COP of the heat pump decreased with increasing ground heat source temperature. As a result, the water switching method with counter flow, compared to a refrigerant switching method, improves the cooling capacity and COP by approximately 6~9% in average, respectively.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.13 no.4
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• pp.31-38
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• 2017

The heating and cooling air conditioning field has been increasing the problems of energy consumption and global warming in the world. A geothermal heat pump has been known as one of the highest efficient heating and cooling system. In this study, the analysis about the test standards of the geothermal heat pump of the Republic of Korea was executed. From the research, the following results were given. It is needed to address the domestic test standard for direct heat exchange geothermal heat pump. Water to air multi geothermal heat pump test standard was only developed in Korea. The test standard to calculate a seasonal energy efficiency ratio for cooling period and heat seasonal performance factor for heating period should be newly developed to estimate actual annual energy consumption and $CO_2$ emission.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.5
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• pp.320-326
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• 2000

The canned motor of 3-phase induction is used for main coolant pump(MCP). The type of motor is canned-motor that stator and rotor are welded by sealed can. So, cooling water flows in the air gap of the canned motor as an independent cycling cooling system from the air gap to yoke of the motor to prevent high temperature of stator can and to lubricate bearing. Heat exchange is occurred between cooling water in the air gap and cooling water from the exterior pump to prevent rising of temperature in the motor. I has to analyze the characteristics of can exactly because the loss and the heat in the can are very important to design MCP. Therefore, thermal analysis is studied considering the effect of eddy-current los induced in the can.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.10
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• pp.678-686
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• 2011

Simulation study on the operating characteristics in the solar hybrid R744 heat pump system for residential applications was carried out with heat pump operating temperature, outdoor temperature and solar radiation. As a result, collector operating time is decreased by 1.5 hours due to the increase of water temperature in the heat storage tank when the heat pump operating temperature rises. Heat pump operating time is reduced by 19.4% owing to the high temperature of a heat storage tank. Besides, indoor heating time is decreased from 10.3 to 5.5 hours as the indoor temperature increases from $3^{\circ}C$ to $11^{\circ}C$. In addition to, when the solar radiation rises from 10 to 20 MJ/$m^2$, the maximum outlet temperature of a solar collector is increased from $65^{\circ}C$ to $71^{\circ}C$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.8
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• pp.571-579
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• 2011

Heat pump systems for commercial building with variable refrigerant flow(VRF) are expanding a market due to high energy efficiency, lower maintenance cost and easy installation comparing with the conventional heat pump with the constant refrigerant flow. In general, heat pump systems degrade the energy efficiency in the extremely low temperature regions. In this study, VRF heat pump system with refrigerant heating is experimentally investigated to overcome the low heating performance in the extremely low temperature regions. VRF heat pump system with refrigerant heating is found out the sufficient heating performance in the -25 degree temperature condition comparing with the conventional heat pump system and is obtained more than 2,500 kPa high pressure in the evaporator at low temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1192-1203
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• 2005

A technical analysis was conducted to predict the development trend for heat pump system. The study was based on a submitted patent from 1983 to 2002 in Korea, U.S.A. and Japan. The total number of raw data from the registered database was 19,261 and the obtained data to be analyzed through the filtering process was 5,143. Technical development of compression type heat pump was more dominant than the other types, absorption, adsorption, and chemical heat pump. The patents for compression type made up over $80\%$ in each country, Most of patents were developed for the defrosting and controlling technology of the compression type heat pump system. Approximately $24\%\;and\;62\%$ of the patents about compression type heat pump were for defrosting and control technologies, respectively.

• International Journal of Fluid Machinery and Systems
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• v.8 no.1
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• pp.13-22
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• 2015

This study presents a simulation model of a heat pump air conditioning system with a variable capacity compressor and variable speeds fans for electric bus. An experimental sample has been developed in order to check results from the model. Effects on system performance of such working conditions as compressor speed, evaporator fans speeds and the condenser fans speeds have been simulated by means of developed model. The results show that the three speeds can be adjusted simultaneously according to actual working condition so that the AC system can operate under the optimum state which the control objects want to achieve. It would be a good and simple solution to extend the driving ranges of EVs because of the highest efficiency and the lowest energy consumption of AC system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.7
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• pp.585-590
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• 2012

The objective of this study is to investigate the performance of a two-stage compression heat pump system for district heating. The experimental setup of heat pump consists of compressor, condenser, evaporator, expansion device, intercooler, flash tank, oil separator and accumulator. The experimental evaluations on the two-stage compression cycle were carried out under various operating conditions which were heat source temperature, the degree of compressor inlet superheat, and intermediate pressure. The temperature ranges of unutilized energy as the heat source were used in the test conditions. As the heat source temperature increased from $10^{\circ}C$ to $30^{\circ}C$, the COP and heating capacity of the heat pump system increased by 22.6% and 45.8%, respectively. The performance of the two-stage heat pump system increased by 5.2% with the variation of the intermediate pressure in the same heat source temperature conditions.