• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.456-463
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• 2019

Micro climatic conditions within the livestock facility are affected by various factors such as ventilation, cooling, heating, insulation and latent and sensible heat generation from animals. In this study, numerical BES method was used to simulate energy flow inside the poultry house. Based on the BES method and THI concept, degree of thermal stress of poultry was evaluated according to the locations in South Korea. Comparison of THI values within the poultry house was also carried out according to the stocking densities to reflect recent animal-welfare issue. Significant decrease in thermal stress of poultry was observed when the stocking density of $30kg/m^2$ was applied in the change of the seasons(p<0.05) however, there was no statistically significant difference in summer season(p>0.05). It meant that installation of proper cooling system is urgently needed. For Iksan city of Jeollabuk-do province, total 252 hours of profit for thermal stress was found according to decrease in the stocking density.

• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.576-585
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• 2018

Systematic management during the whole life cycle from construction to operation and maintenance is very important for the seven underground pipelines (waterworks, sewerage, electricity, telecommunications, gas, heating, oil including waterworks and sewerage). Especially, it is the construction process that affects the whole life cycle of underground buried pipeline. In order to construct a new city or to maintain different underground pipes, it is always necessary to dig the ground and carry out construction and related work. There is a possibility that secondary and tertiary breaks frequently occur in the pipeline construction process after the piping constructed first in this process. To solve this problem, a system is needed which can monitor damage in real time. However, the supply of electric power for continuous operation of the system is limited according to the environment of underground buried pipelines, so it is necessary to develop a stable electric power supply system using natural energy rather than existing electric power. In this study, we developed a system that can operate the pipeline monitoring system for long time (24 hours and 15 days) using natural energy using wind and solar light.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.3
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• pp.43-48
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• 2008

The economics of a passive solar heating system (PSHS) with the pebble bed heat storage was evaluated, and the applications of the PSHS were analyzed, in this study. The results are as follows: The heating load, solar heat gain, and stored heat/year of the PSHS in the solar house model were found to be 10,778MJ, 3,438MJ, and 11,682MJ, respectively. The yearly energy expenses of the PSHS and the alternative heating system (conventional coal heating system, CCHS), which uses coal, were found to be USD 1.60/year and USD 60.90/year, respectively, and the yearly expenses of the PSHS were found to be 38 times less than those of the alternative heating system (CCHS). If it will be supposed that the life cycle of the passive solar heating system, according to the results of the LCC analysis in the two systems, is 40 years, the total expenses for the life cycle of the PSHS and the CCHS will be USD 1,431.50 and USD 2,740.00, respectively. The period for the investment payback of the PSHS is six years.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.37-44
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• 2008

The global warming potential (GWP) of $CO_2$ refrigerant is 1/1300 times lower than that of R134a. Furthermore, the size and weight of the automotive heat pump system can decrease because $CO_2$ operates at high pressure with significantly higher discharge temperature and larger temperature change. The presented $CO_2$ heat pump system was designed for both cooling and heating in fuel cell vehicles. In this study, the performance characteristics of the heat pump system were analyzed for heating, and results for performance were provided for operating conditions when using recovered heat from the stack coolant. The performance of the heat pump system with heater core was compared with that of the conventional heating system with heater core and that of the heat pump system without heater core, and thus the heat pump system with heater core showed the best performance among the selected heating systems. On the other hand, the heating performance of two different types of coolant/air heat pump systems with heater core was compared each other at various coolant inlet temperatures. Furthermore, to use exhausted thermal energy through the radiator, experiments were carried out by changing the arrangement of a radiator and an outdoor evaporator, and quantified the heating effectiveness.

• Journal of Biosystems Engineering
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• v.26 no.6
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• pp.553-562
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• 2001

The greenhouse heating system with heat pump and latent heat storage was built for development of simulation model and validation. The computer simulation model for the system to predict temperature of air, soil surface and cover film in the greenhouse were developed and its validity was justified by actual data. From the analysis of experimentally measured and the simulation output, following results were obtained. 1. The expected values of inside air temperature for the greenhouse with a heat pump and a latent heat storage system were very much close to the experimental values at the error range of 1.0$\^{C}$. 2. The expected values of soil surface temperature fur the geenhouse with a heat pump and a latent heat storage system were very much close to the experimental values at the error range of 1.0$\^{C}$. 3. The expected values of thermal energy flow fur the greenhouse with a heat pump and a latent heat storage system were very much close to the experimental values at the error range of 167.2kJ/m$^2$h. 4. Heat lass value of day time was found to be larger than that of night time as much as 1.11 time. 5. At day time. the inside air temperature was shown to be higher than the set point of 7.0$\^{C}$. At night time, the inside air temperature was controlled in order to maintain higher temperatures than the set point.

• KIEAE Journal
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• v.16 no.6
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• pp.109-114
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• 2016

Purpose: The underground air is the warm air discharged from the porous volcano bedrock 30-50m underground in Jeju, including excessive humidity. The temperature of the underground air is $15-20^{\circ}C$ throughout the year. In Jeju, the underground air was used for heating greenhouses by supplying into greenhouses directly. This heating method by supplying the underground air into greenhouses directly had several problems. The study was conducted to develop the heat pump system using underground air as heat source for resolving excessive humidity problem of the underground air, adopting the underground air as a farm supporting project by Ministry of Agriculture, Food and Rural Affairs(MAFRA) and saving heating cost for agricultural facilities. Method: 35kW scale(10 RT) heat pump system using underground air installed in a greenhouse of area $330m^2$ in Jeju-Special Self-Governing Province Agricultural Research & Extension Services, Seogwipo-si, Jeju. The inlet and outlet water temperature of the condenser, the evaporator and the thermal storage tank and the underground air temperature and the air temperature in the greenhouse were measured by T type thermocouples. The data were collected and saved in a data logger(MV200, Yokogawa, Japan). Flow rates of water flowing in the condenser, the evaporator and the thermal storage tank were measured by an ultrasonic flow meter(PT868, Panametrics, Norway). The total electric power that consumed by the system was measured by a wattmeter(CW240, Yokogawa, Japan). Heating COP, rejection heat of condenser, extraction heat of evaporator and heating cost were analyzed. Result: The underground air in Jeju was adopted as a farm supporting project by Ministry of Agriculture, Food and Rural Affairs(MAFRA) in 2010. From 2011, the heat pump systems using underground air as a heat source were installed in 12 farms(16.3ha) in Jeju.

• Journal of the Korean Solar Energy Society
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• v.35 no.6
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• pp.25-33
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• 2015

In this study, heating performance of the air-cooled heat pump with vapor-injection (VI) cycles, re-heater and solar heat storage tank was investigated experimentally. Devices used in the experiment were comprised of a VI compressor, re-heater, economizer, variable evaporator, flat-plate solar collector for hot water, thermal storage tank, etc. As working fluid, refrigerant R410A for heat pump and propylene glycol (PG) for solar collector were used. In this experiment, heating performance was compared by three cycles, A, B and C. In case of Cycle B, heat exchange was conducted between VI suction refrigerant and inlet refrigerant of condenser by re-heater (Re-heater in Fig. 3, No. 3) (Cycle B), and Cycle A was not use re-heater on the same operating conditions. In case of Cycle C, outlet refrigerant from evaporator go to thermal storage tank for getting a thermal energy from solar thermal storage tank while re-heater also used. As a result, Cycle C reached the target temperature of water in a shorter time than Cycle B and Cycle A. In addition, it was founded that, as for the coefficient of heating performance($COP_h$), the performance in Cycle C was improved by 13.6% higher than the performance of Cycle B shown the average $COP_h$ of 3.0 and by 18.9% higher than the performance of Cycle A shown the average $COP_h$ of 2.86. From this results, It was confirmed that the performance of heat pump system with refrigerant re-heater and VI cycle can be improved by applying solar thermal energy as an auxiliary heat source.

• Journal of Biosystems Engineering
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• v.35 no.2
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• pp.108-115
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• 2010

This study was conducted to estimate the optimum temperature and required time for soil sterilization when heated water was circulated through underground heating pipes in the greenhouse which solar heat was influenced to the temperature of soil during the summer day. Two different types of heating pipes were used for the experiment. One was a polyethylene pipe(XL) and the other was a corrugated ring shaped stainless steel pipe(STS). The results of the studies were summarized as follows; By measuring the thermal characteristics of the XL and STS, it was examined that the average temperature differences of the inlet and outlet were $8.5^{\circ}C$ and $13.3^{\circ}C$, the average flowrates were 15.3 L/min and 5.6 L/min, and the average radiation powers were 9.1 kW and 4.1 kW, respectively. As results of the regression analysis of underground temperatures, when average soil temperature was$35^{\circ}C$, an average water temperature was $80^{\circ}C$, and XL was used, it was estimated that the possible heat transfer distance, the required time for heat transfer and heat flux to reach the underground temperature of $60^{\circ}C$ were 300 mm, 230 hours, and $7.57kW/m^2$, respectively.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.571-571
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• 2009

지열은 날씨와 기온 등에 영향을 받지 않고 연중 가동할 수 있어 기저부하를 담담할 수 있는 유일한 신재생에너지 자원이므로 이에 대한 기술개발이 시급하다. 우리나라는 비화산지대이며 지중 온도가 가장 높은 지역의 5km에서 약 $170^{\circ}C$ 내외이므로 외국에 비해 지온경사도가 크지 않은 편이다. 그리고 3km 이상에서는 지하대수층이 거의 존재하지 않기 때문에 지열발전을 위해서는 EGS 기법을 도입할 수 밖에 없는 실정이다. 그리고 지열수를 확보할 수 있는 온도범위가 약 $100{\sim}150^{\circ}C$ 정도이므로 이에 적합한 지열발전 플랜트를 선정할 필요가 있다. 일반적으로 지열발전에 적용되는 플랜트는 건증기 지열발전, 플래쉬증기 지열발전, 바이너리 사이클 지열발전으로 분류할 수가 있으나 국내 여건에 맞는 방식으로서 바이너리 사이클 발전으로서 ORC 플랜트 또는 Kalina 사이클 플랜트가 적합하므로 이에 대한 기술 개발이 적극적으로 이루어져야 한다. 따라서 국내 지열발전의 기술개발에 있어서 핵심요소는 심부천공 및 EGS를 위한 인공파쇄기술과 지상 플랜트로서 저온지열 발전 플랜트의 기술확보가 필요한 실정이다. 이와 같은 기술개발이 완성되면 발전 뿐만아니라 집단지역난방, 온실 및 양어장 등에도 열공급이 가능한 열병합발전이 가능하게 될 것이다. 또한, EGS 기술로서 상업적 성공을 이룬 것은 세계적으로 2~3개 사례에 불과한 신기술로서, EGS 기술의 국내 조기 실현으로 기술 선점 및 해외 수출을 모색할 필요가 있다. 그리고 심부 지열자원은 국내 어디에나 부존하는 ubiquitous 자원이며 이산화탄소 배출이 전무한 청정 국산 에너지 자원이나, 이의 개발에는 높은 초기 투자비와 risk를 요하므로 민간 업체의 투자가 제약을 받는다. 따라서 정부의 적극적인 지원하에 산.학.연 중심으로 시범보급이 우선 이루어진 후 민간의 자발적 투자를 통한 지열 개발을 유도할 필요가 있다.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.587-589
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• 2009

The districts of underground geologic structure in Jeju island where underground air is distributed are lava cave, pyroclastic, open joint, and crushing zone. Such districts are identified to secure an enough airflow when air ventilation layer is to secure 25-35m in depth. In Jeju, Ground air is used for heating greenhouse and fertilizing natural $CO_2$ gas by suppling directly into greenhouse. But the heating method by suppling ground air into greenhouse directly bring about several problem. The occurrence of disease of the crops by high humidity is worried because the underground air which becomes discharge from underground air layer has over 90% relative humidity. The underground air is inadequate in heating for crops which need high temperature heating such as mangos, Hallbong and mandarin orange because the temperature of it is $15{\sim}18^{\circ}C$. Also There is worry where the ventilation loss becomes larger because the air pressure inside greenhouse is high by supplying underground air directly. In this study the heat pump system using underground air as heat source was developed and heating performance of the system was analysed. Heating COP of the system was 2.5~5.0 and rejecting heat into greenhouse and extracting heat from underground air were 40,000~27,000 kcal/h, 30,000~18,000 kcal/h respectively.