• Plant Journal
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• v.10 no.2
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• pp.28-37
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• 2014

Recently, it is considered that environment and energy are critical issues all over the world. In power generation sector in Korea, almost power stations are constructed and operated as cogeneration plants in conformity with this trend. KDHC(Korea District Heating Corporation) goes one step further adopting renewable energy technology like heat pump using wasted heat for energy-saving and environment improvement. This study investigates the performance characteristics by the location of waste heat recovery heat pumps of 5 Gcal/h capacity in 150 MW-class Gwang-gyo cogeneration plant using commercial software 'THERMOFLEX'. Prior to analysis, the simulations are performed with actual operation data, and then the validation of simulations is verified by checking the error within 2%. After verification, the simulations are carried out with 3 locations and the effect on electrical power output and heat output is analyzed. As a result, overall efficiency of cogeneration plant is the highest in the case of heat pump located before DH(District Heating) Heater because of the largest increase of heat output despite of decrease of electrical power output.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.56-66
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• 2021

In this study, a waste heat recovery system was devised and the performances of components incorporated to recover the heat generated during the processing of aerobic liquid-composting in a livestock manure treatment facility were analyzed. In addition, the availability of recovered heat was confirmed. The heat generated by liquid fermentation in the livestock manure treatment facility was also checked. Experimental temperatures were set at 35, 40, and 45 ℃ based on considerations of the uniformity of aerobic liquid-composting fermentation tank temperature and its operating range (34.5 ~ 43.9 ℃). Recovered heat energies from the combined heat exchanger, which consisted of PE and STS pipes, were 53.5, 65.6, 74.4 MJ/h, The heat pump of capacity 5 RT was heated at 95.6, 96.1, 98.9 MJ/h and the heating COPs of the pump were 4.53, 4.62, and 4.65, respectively. The maximum hot water production capacity of the heat exchanger assuming a fermentation tank temperature of 45 ℃ confirmed an energy supply of 56 360 kcal/day. The heating capacity of the FCU linked to the heat storage tank was 20.8 MJ/h, and the energy utilization efficiency was 96.1%. When livestock manure was dried using the FCU, it was confirmed that the initial function rate was reduced by 50.5 to 45.8 % after drying.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.119-119
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• 2010

무한 지속 가능한 지열 에너지를 활용한 공조시스템인 지열원 냉난방 시스템은 기존의 공조 시스템보다 열원이 안정적이기 때문에 높은 효율과 우수한 성능을 가지므로, 기후변화협약 대응의 주요수단으로서 기술개발과 보급이 증대되고 있다. 본 연구에서는 대수층 축열 지열원 열펌프 시스템에 대한 실증 연구를 통하여 대수층 축열 지열원 열펌프 시스템의 하절기 냉방 성능을 분석하였다. 대수층 축열 냉난방 시스템은 주입정과 양수정의 2개의 우물공이 설치되어 있으며, 겨울 난방 운전 중에 한 개의 우물공으로부터 지하수를 열펌프로 유입한 후 낮은 온도의 지하수를 타 우물공에 축열하고, 하절기에 겨울에 저온으로 축열된 우물공으로부터 지하수를 열펌프로 유입하여 온도가 증가된 지하수를 타 우물공에 주입한다. 즉, 계절별로 열펌프에서 생성된 냉수와 온수의 대수층 축열을 위하여 계절별로 주입정과 양수정이 바뀌게 된다. 본 연구의 대수층 축열 지열원 열펌프 시스템의 2009년 8월의 주요일자별 시스템 운전 중의 평균 냉방 열펌프 유닛 COP와 냉방 시스템 COP는 각각 4.7과 3.4이상의 우수한 성능을 나타냈다. 또한, 모든 일자에 대하여 외기온도가 $31.6^{\circ}C$서 $22^{\circ}C$까지 변화가 크게 나타났지만 열펌프 유닛 COP와 시스템 COP의 변화는 미소하였다. 이는 양수정으로부터의 지중 순환수가 운전기간 중에 $17.5^{\circ}C$로 일정하게 유지되었기 때문이다. 양수정과 주입정 사이에 5개의 관측공을 설치하였으며, 양수정 측에 인접한 관측공의 온도는 거의 변화가 없었으며, 단기간이지만 널리 사용되고 있는 수직밀폐형 시스템과 달리 지속적인 냉방운전 중의 양수 온도의 증가는 발생하지 않아 안정적인 성능을 나타냈다. 주입정에 인접한 모니터링 홀의 온도는 심도가 깊은 곳의 온도가 낮은 곳보다 높게 나타났다. 이는 냉방 운전 시 열펌프 유닛의 실외열교환기에서 지중 순환수가 냉매로부터 열을 취득하여 온도가 상승하면서 주입정측에 온열이 축열이 진행되었기 때문으로 분석되며, 하절기의 냉방 운전 시간이 증가할 경우 축열 효과는 더욱 증가할 것으로 예상된다. 양수정과 주입정 중간의 모니터링 홀의 온도는 2009년 8월 가동 중에 온도변화는 없었는데, 이는 양수정과 주입정 사이의 열간섭이 발생하지 않았기 때문으로 분석된다. 일자별로 운전 중의 열펌프 유닛 COP는 차이가 없었지만, 운전 및 정지 시간을 모두 포함한 시스템 소비전력과 냉방용량을 모두 합산하여 산정한 일일 평균 냉방 열펌프 유닛 COP와 냉방 시스템 COP는 일자별로 다소 차이가 발생하였는데, 이는 각 일자별로 열펌프 유닛 가동율의 차이로 인하여 열펌프 유닛 가동 전에 먼저 작동되는 지중순환펌프의 운전 소비전력의 차이와 열펌프의 단속운전 시의 열손실과 추거 소비전력의 차이 때문이다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.1
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• pp.11-27
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• 2017

The road network system of major domestic urban areas such as city of Seoul was rapidly developed and regionally expanded. In addition, many kinds of life-lines such as electrical cables, telephone cables, water&sewerage lines, heat&cold conduits and gas lines were needed in order for urban residents to live comfortably. Therefore, most of the life-lines were individually buried in underground and individually managed. The utility tunnel is defined as the urban planning facilities for commonly installing life-lines in the National Land Planning Act. Expectation effectiveness of urban utility tunnels is reducing repeated excavation of roads, improvement of urban landscape; road pavement durability; driving performance and traffic flow. It can also be expected that ensuring disaster safety for earthquakes and sinkholes, smart-grind and electric vehicle supply, rapid response to changes in future living environment and etc. Therefore, necessity of urban utility tunnels has recently increased. However, all of the constructed utility tunnels are cut-and-cover tunnels domestically, which is included in development of new-town areas. Since urban areas can not accommodate all buried life-lines, it is necessary to study the feasibility assessment system for utility tunnel by urban patterns and capacity optimization for urban utility tunnels. In this study, we break away from the new-town utility tunnels and suggest a quantitative assessment model based on the evaluation index for urban areas. In addition, we also develop a program that can implement a quantitative evaluation system by subdividing the feasibility assessment system of urban patterns. Ultimately, this study can contribute to be activated the urban utility tunnel.

• Journal of the Korean Institute of Gas
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• v.4 no.1 s.9
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• pp.63-68
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• 2000

We have developed a new relief valve which is a safety device for the domestic gas-fired hot water boilers. The relief valve has been designed to expand the inner diameter of the inlet, the outlet and the seat of the valve considering the relief capacity, and also to separate the spring from the room heating water. Therefore, we could minimize the adhesion and/or obstruction of the inlet and the corrosion phenomena of the spring which used to be the problem of the conventional relief valves. Test results of the developed relief valve showed that the performance of the opening pressure, reseating pressure, tightness, endurance were excellent, and the operating boiler with developed relief valve was evaluated as very good. The standardization and application of the relief valve can provide the advantage of component exchange and easy maintenance and repair.

• Transactions of the KSME C: Technology and Education
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• v.3 no.1
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• pp.1-13
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• 2015

In this study, a new dynamic VRF-type heat pump simulation model is proposed which incorporates frosting and defrosting models. Toward this end, a simple frosting model based on the perfect analogy, and lumped system based defrost model, are proposed. Then, frosting and defrosting models are incorporated into a dynamic heat pump model which adopts segment-by-segment local heat exchanger model and map-based variable speed compressor model. Thus, the model can naturally represent locally uneven frosting and defrosting on the heat exchanger surface. Developed simulation model is validated against available experimental data to show good agreement within 10% error for capacity and COP. Finally, developed dynamic heat pump model is applied to annual heating season simulation to show that seasonal COP of heat pump is degraded by 7% due to frosting and defrosting.

• The Journal of Engineering Geology
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• v.28 no.3
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• pp.475-488
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• 2018

This study evaluates geothermal system efficiency in terms of input power and heat exchange volume on the heat-source and load sides, by applying a combined open-closed type loop system comprising a geothermal system and a groundwater well to a cultivation site. In addition, this study analyzes the effects of heating and cooling for a complex geothermal system, by evaluating the temperatures of an external site and a cultivation site during operation. During cooling operations the heat exchange volume on the heat source side, average 90.0kW/h for an open type system with an input of 235L/minute groundwater, and 40.1kW/h for a closed type system with an input of 85L/minute circulating water, for a total average heat exchange volume of 130.1kW/h. The actual heat exchange volume delivered on the load side averages 110.4kW/h. The average EER by analysis of the geothermal system's cooling efficiency is 5.63. During heating operation analysis, the heat exchange volume on the heat source side, average 60.4kW/h in an open type system with an input of 266L/minute groundwater, and 22.4kW/h in closed type system with an input of 86L/minute circulating water, for a total average heat exchange volume of 82.9kW/h. The actual heat exchange volume delivered on the load side averages 112.0kW/h in our analysis. The average COP determined by analysis of the geothermal system's heating efficiency is 3.92. Aa a result of the tradeoff between the outside temperature and the inside temperature of the production facility and comparing the facility design with a combined well and open-closed loops geothermal(CWG) system, we determine that the 30RT-volume CWG system temperature are lower by $3.4^{\circ}C$, $6.8^{\circ}C$, $10.1^{\circ}C$ and $13.4^{\circ}C$ for ouside temperature is of $20^{\circ}C$, $25^{\circ}C$, $30^{\circ}C$ and $35^{\circ}C$, respectively. Based on these results, a summer cooling effect of about $10^{\circ}C$ is expected relative to a facility without a CWG system as the outside temperature is generally ${\geq}30^{\circ}C$. Our results suggest that a complex geothermal system provides improvement under a variety of conditions even when heating conditions in winter are considered. Thus It is expected that the heating-cooling tradeoffs of complex geothermal system are improved by using water screen.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.199-199
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• 2011

ATES(Aquifer Thermal Energy Storage) 열펌프 시스템은 기존의 다양한 열원 적용 시스템 대비 효율이 우수한 것으로 알려져 유럽과 미국에서 건물 냉난방 시스템으로 적용되고 있다. 특히, ATES 시스템은 기존의 냉난방 시스템 대비 경제성이 우수한 것으로 알려져 있으나 국내에서는 이에 대한 연구 결과는 전무한 실정이다. 본 연구에서는 ATES 열펌프 시스템의 실증 성능 결과를 분석하였으며, LNG 보일러와 에어컨을 사용하는 기존의 냉난방 시스템을 비교시스템으로 ATES 열펌프 시스템의 경제성 평가를 수행하였다. ATES 시스템의 연간 실증 성능 실험결과 ATES 시스템은 외기온도와 무관하게 연중 안정적인 성능을 나타내었다. 경제성 평가시에 생애주기법(Life Cycle Cost)을 적용하여 ATES 열펌프 시스템의 설치 및 운전에 필요한 총 소요비용을 산정하고, 이 결과를 바탕으로 투자회수기간법을 통해 ATES 시스템의 투자회수 기간을 산정하였다. 생애주기법 적용 시에 현재가치법을 사용하였으며, 현재가치법은 수명주기에 발생하는 모든 투자비용과 절감액을 일정한 시점을 기준으로 등가환산하는 방법을 의미한다. 현재가치법에 사용되는 현재가치는 초기비용과 현재가치계수의 곱으로 나타나는데, 여기에서 현재가치계수는 임의의 이자율로 일정기간 동안 정기적인 할부금액이 적립될 때의 현재금액을 구하기 위해 사용하는 계수를 의미한다. 전기와 LNG는 각각 2009년 7월의 (주)한국전력공사와 (주)한국가스공사의 고시요금을 적용하였다. 본 시스템은 실증 설비용량인 20RT를 대상 건물로 가정하였고, 초기투자비는 크게 공사비와 냉난방 설비 구입비로 구성되어 있으며, 기본적인 물가지표는 (사)한국물가정보(KPI)의 고시 데이터를 참조하였다. 각 시스템의 초기투자비는 ATES 시스템이 비교대상 기존 냉난방 시스템 대비 5.7배 높게 나타났다. 일일 8시간 사용기준으로 계절별 전력요금을 고려한 연간운전 비용은 ATES 시스템이 기존 시스템 대비 냉난방 시에 각각 77%와 16%를 나타내어 운전비용이 연간 절감되었고, 난방 운전 시 절감 비율이 냉방시보다 크게 나타났다. 두 시스템에 대한 생애주기비용을 산정하기 위하여 에어컨과 보일러의 기존시스템과 ATES 시스템의 가용연수를 모두 20년으로 설정하였고, 유지보수 비용은 초기투자비용의 2%로 설정하고, 할인율은 은행 예금이자를 기준으로 5%로 설정하였다. 전기와 LNG의 요금 상승률은 (사)한국물가정보를 바탕으로 각각 2%와 8%로 가정하였다. 이러한 조건에서 생애주기법을 이용한 경제성평가는 ATES 시스템의 경우 생애운전비용이 초기투자비용보다 작게 나타났으며, 기존 냉난방 시스템은 생애운전비용이 초기투자비용에 비하여 높게 나타났다. 본 연구 대상 ATES 열펌프 시스템의 실증 성능 데이터와 기존 문헌으로부터 얻은 냉난방 시스템의 성능 결과를 이용하여 생애주기 비용을 적용한 결과 ATES 시스템의 기존 시스템 대비 투자회수 기간은 6.62년으로 나타났다. 특히, 본 연구에서는 ATES 시스템이 국내 최초로 적용됨에 따라 스크린 등의 부품을 다소 고가의 제품으로 시스템에 적용하였으므로 ATES 시스템의 신뢰성과 안정성이 확보되면 초기 투자비 감소가 가능할 것으로 예상되며, 기존 시스템 대비 투자회수 기간은 더욱 감소될 수 있을 것으로 예상된다.

• Journal of Energy Engineering
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• v.21 no.4
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• pp.435-443
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• 2012

The combination of space shortage and the high population density concentrated in urban areas of South Korea has resulted in the growth of large-scale high-rise residential complexes, naturally affecting water and hot water usage patterns as well. But the current designs for water and hot water supply in South Korea rely mostly on international design standards and data calculated on site due to the severe shortage of basic data in relation to actual use, which result in the frequent problem of the under-or over-design of water and hot water supply. The following study measures the hot water supplier's conditions and the user's heat usage to realize the amount of time required for hot water supply load generation and the pattern of actual use in order to create basic data for effective hot water supply facility design and maintenance.

• Journal of Energy Engineering
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• v.26 no.2
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• pp.99-120
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• 2017

In SS branch of Korea District Heating Corporation, Combined Heat & Power power plant with 99MW capacity and 98Gcal / h capacity is operated as a district electricity business. In this region, it is difficult to operate the generator due to the problem of surplus heat treatment between June and September due to the economic recession and the decrease in demand, so it is urgent to develop an economical energy new business model. In this study, we will develop an optimized operation model by introducing a renewable energy hybrid system based on actual operation data of this site. In particular, among renewable energy sources, fuel cell (Fuel Cell) power generation which can generate heat and electricity at the same time with limited location constraints, photovoltaic power generation which is representative renewable energy, ESS (Energy Storage System). HOMER (Hybrid Optimization of Multiple Energy Resources) program was used to select the optimal model. As a result of the economic analysis, 99MW CHP combined cycle power generation is the most economical in terms of net present cost (NPC), but 99MW CHP in terms of carbon emission trading and renewable energy certificate And 5MW fuel cells, and 521kW of solar power to supply electricity and heat than the supply of electricity and heat by 99MW CHP cogeneration power, it was shown that it is economically up to 247.5 billion won. we confirmed the results of the improvement of the zone electricity business condition by introducing the fuel cell and the renewable energy hybrid system as the optimization process model.