• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.43 no.12
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• pp.44-46
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• 2014

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.42-46
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• 2017

As $CO_2$ emission with imprudent using fossil fuel, annual mean temperature of earth is increased in every year. Geothermal energy is inexhaustible energy resource to solve this problem. Heat pump performance and heat exchange efficiency of ground loop are important to distribute widely. Thus, this study are performed to increase heat pump performance and heat exchange efficiency of ground loop with dual expansion valves and spacer. As a results, COP of cooling & heating is obtained improvement up to 11.4% using dual expansion valves, and heat exchange efficiency is increased up to 17.5% using spacer. It will be reduced initial installation cost due to increasing heat pump performance and heat exchange efficiency of ground loop.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.14 no.2
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• pp.1-7
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• 2018

The purpose of this study was to analyze the energy consumption of Elementary, Middle and High Schools in Daejeon Metropolitan City. The main results are as follow: 1) Annual energy consumption per class was 12,825 (kWh/class) at elementary schools, 15,780 (kWh/class) at middle schools, and 29,447 (kWh/class) at high schools, 2) Generally the smaller the size of the school, the higher the energy consumption per class. However according to the HVAC system there was no consistent pattern of energy consumption per class. 3) According to Box and Whisker's Chart, distribution of energy consumption of elementary and middle schools' had small range. However, the range of high schools increased. 4) Energy consumption in winter season was larger than that of summer season in schools.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5317-5322
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• 2013

This study presents a prediction method for heat transfer performance of a gas cooler of $CO_2$ heat pump using ${\epsilon}$-NTU method, and compared the results with the experimental data from the open literature. The heat transfer rate, refrigerant side outlet temperature and water side outlet temperature were calculated by using EES(Engineering Equation Solver)program in multi-tube-in-tube type $CO_2$ heat pump gas cooler. Analysis was performed in two methods : The first method performed without dividing into the test section by applying an analysis of the mean properties(mean analysis). The second method, tube length divided into 50 sections, was applied to the local properties(local analysis). From the present study, a good agreement at the local analysis was obtained between the analytical and experimental results by 0.3~1.1%, 1.31~1.88% and 3.12~5.18% for heat transfer rate, water and refrigerant side outlet temperatures, respectively.

• Journal of the Korean Institute of Gas
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• v.18 no.4
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• pp.13-20
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• 2014

In natural gas distribution system, gas pressure is regulated correspond to requirement using throttle valve which is releasing huge pressure energy as useless form. The waste pressure can be recovered by using turbo machinery devices such as a turbo expander. In this process, excessive temperature drop occurs due to Joule-Thompson effect during the expansion process. Installing natural gas boiler before or after the turbo expander prevents temperature drop. Fuel cell or gas engine hybrid system further improve the efficiency, but 1~2% of total transporting natural gas is used for operating the hybrid system. In this study, a heat pump system is proposed as a preheating device which can be operated without using transporting natural gas. Thermodynamic analysis on evaporating and condensing temperatures and refrigerants is conducted. Results show that R717 is proper refrigerant for the hybrid system with high COP and low turbine work within the defined operating conditions. In domestic usage in Korea, the heat pump system has more economic feasibility owing to natural gas being imported with a high price of LNG form.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.10
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• pp.879-887
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• 2003

Buildings with heating and cooling systems have been increased, since the requirement of thermal comfort for residents is grown. Heating and cooling systems, have been changed from two separate systems to one multi-function system which includes both heating and cooling. Especially, heat pump heating and cooling system has been adopted for general classrooms in schools since education environment improvement project has been launched. This research suggests the best option for the heat pump heating and cooling system in educational buildings through economic assessments for four alternative systems based on electric heat pump (EHP) and gas engine driven heat pump (GHP), which are most widely used for elementary, middle and high schools. The model buildings are in the Y high school which has 24 classes of new construction building, which will be built soon. Annual energy consumption for alternative systems uses BECS 3.10, which can be used for system simulation.

• Environmental and Resource Economics Review
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• v.20 no.2
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• pp.381-398
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• 2011

Recently, electricity peaks have frequently occurred in winter, and the concerns about failure in power supply are soaring. One of reasons is due to the increase in industrial demand with economic recovery, and the increases in household and commercial demand with unusual cold waves are spotted as a primary cause. Especially, the diffusion of electricity heat pumps (EHP) has led to the rapid increase in commercial electricity demand. The EHP diffusion is mainly associated with low electricity tariff and cheaper heating and cooling costs compared to those of gas-engine heat pumps (GHP). The problem is that distorted electricity tariff and herd behaviour toward heating and cooling devices could bring about nation-wide inefficiencies in resource allocation. The key countermeasures are as follows. The electricity tariff should be readjusted to a realistic level. The tariff scheme should be so modified that consumers rationally respond to the tariff. In addition, one should find ways to effectively manage electricity demand.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.212-217
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• 2009

냉방기기별 하절기 가동률 및 동시사용률 실태를 조사하여 건물의 용도 및 면적 별냉방기기의 시간별 부하률 과 동시사용률, 연간 사용일수 가동시간을 조사하여 냉방기기별 에너지 소비현황 하절기 에너지수급 영향분석을 하고자 하였다. 그리고 국내에 설치된 냉방기기를 대상으로 현장조사 진단을 통해 냉방기기 사용 실태 및 냉방성능을 측정하고, 현장 조사를 통한 만족도와 불만사항을 조사하여 냉방기기 보급 및 운전의 효율을 상승시키고 모든 냉방기기 국산화를 위한 기초자료와 이를 위한 정책적 지원방안 및 향후 냉방기기 기술개발 방향을 제시하고자 한다. 또한 냉방기기별로 문제점을 도출하여 향후 정책제도 개선에 반영할 수 있도록 하였다.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.14 no.1
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• pp.8-15
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• 2018

The purpose of this study was to analyze the energy consumption according to the HVAC systems in 122 elementary schools. To do this, we classified schools according to the HVAC systems. Selected schools were classified to the following groups by the HVAC equipments: EHP, EHP and GHP together and GHP. In addition we divided schools by the number of classes. The main results are as follow: 1) Annual average energy consumption at schools was about 300~900(kWh/students), $30{\sim}50(kWh/m^2)$, 9,000~29,000((kWh/class) 2) The smaller schools, the higher the energy consumption per class; energy usage of 10~19 classes's schools were approximately 3 times higher than 40 classes's schools. 3) Schools where the EHP was installed had the lowest energy costs and energy usage. The difference in energy costs was lower than the difference in energy usage because of the fuel price and the ratio of energy sources.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.7
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• pp.308-314
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• 2014

A heat pump has been considered as a thermal management unit for electric vehicles, including the heating and cooling of the cabin. However, the heat pump shows performance degradation at low outdoor temperatures or high compressor speeds. In this study, a R-134a heat pump for an electric vehicle was designed to improve system efficiency, by applying vapor injection with an internal heat exchanger. The heating performance characteristics of the vapor injection heat pump were analyzed at various compressor speeds and outdoor temperatures. The vapor injection heat pump showed 13.3% COP improvement over the non-injection heat pump, when the heating capacity was fixed at 5.2 kW. In addition, the heating capacity of the vapor injection system increased by 9.6%, as compared to the non-injection system.