태양열 집열관 과열방지를 위한 지중열교환기 연구

황현창(Hyun-Chang Hwang),Ri-Guang Chi,이계복(Kye-Bock Lee),이석호(Seok-Ho Rhi) 한국산학기술학회 2016 한국산학기술학회논문지 Vol.17 No.7

하절기 줄어드는 온수부하는 태양열 집열기 과열의 주된 원인이다. 과열방지목적으로 공냉 또는 차단막이 사용되는 데 이는 추가적인 기계적요소를 필요하게 되고 장기 운용 시 파손 등의 우려에 따라 그 신뢰도도 크게 저하된다. 지중열교환 기는 지열을 열원으로 방열 또는 흡열을 진행하는데, 지열을 고 열원으로 하여 흡열을 목적으로 하는 연구가 대다수이며 지열원이 저열원으로 이용하는 방열에 대한 연구는 부족한 편이다. 그리하여 본 연구에서는 태양열집열판의 과열방지를 목 적으로 하는 지중열교환기의 가능성 및 그 성능에 대한 연구를 진행하였다. 여름철 최대 150oC이상의 고온을 유지하는 태양 열집열판의 열을 방출하기 위하여 1.2m의 하부 깊이를 갖는 50m 나선형 지중열교환기를 설치하였고 이를 통해 순간 냉각이 가능한 것으로 확인되었으며, 태양열집열판의 여름철 과열에 의한 파손을 방지할 수 있었다. 그리고 다양한 변수에 대한 이론 적인 계산을 통하여 0.33kg/s의 최저 순환유량만 유지해주면 지열 열교환기의 길이에 따른 방열효과에 큰 영향을 미치지 않 음을 판단할 수 있다. 또한 축열조와의 공동 사용시 냉각효과는 여름철 과열시 충분한 과열방지 제어가 가능한 것으로 조사 되었다. The heating load using solar hot water is lower in summer than in the other seasons. This decreased heating load leads to the overheating solar collectors and related components. To prevent overheating of the solar collectors, air cooling and shading shields were used. On the other hand, it requires additional mechanical components, and reduces the system reliability. The geothermal heat dump system to release the high temperature heat (over 150oC) transferred from the heat pipe solar collectors was investigated in the present study. Research on the heat dump to cool the solar collector is rare. Therefore, the present study was carried out to collect possible data of a geothermal heat dump to cool the solar collector. A helical type geothermal heat exchanger was buried at a 1.2m depth. Experimentally and numerically, the geothermal heat dump was investigated in terms of the effects of parameters, such as the quantity of solar radiation, aperture area of the collector and the mass flow rate. A pipe length of 50m on the geothermal heat exchanger was suitable with a 0.33 kg/s flow rate. The water reservoir was a possible co-operation solution linked to the geothermal heat exchanger.

한국 기후 상에서 지열히트펌프와 공대공히트펌프의 성능계수 비교

Bilal Ahmad,Kim, Dong-Hwan,Bahk, Sae-Mahn,Choi, Eun-Soo 明知大學校 産業技術硏究所 2009 産業技術硏究所論文集 Vol.28 No.-

This paper discusses a Coefficient of Performance of geothermal heat pump and air-to-air heat pump in the climatic conditions of Republic of Korea in heating mode.A vertica IU-shaped geothermal heat exchangεr using water as the working fluid has been designed using the temperature gradient of Korean soil obtained from Korea Meteorological Administration (KMA). The analysis was carried out using finite volume software ‘Fluent’. The heated water from the geothermal heat exchanger was used as the heat source for the heat pump circui t. A Comparison of Coefficient of Performance of geothermal heat pump and air-to-air heat pump in the climatic conditions of Republic of Korea has been dis cussed in heating mode. And it has been shown that using geothermal heat pumps is more efficient than air-to-air heat pump in the climatic conditions of Republic of Korea for heating purpose..

심부지열 용 동축 열교환기 성능예측을 위한 열전달 실험 및 해석

정국진,정윤성,박준수,이동현,Jung, Kuk-Jin,Jeong, Yoon-Seong,Park, Jun Su,Lee, Dong Hyun 한국교통대학교 융복합기술연구소 2017 융ㆍ복합기술연구소 논문집 Vol.7 No.1

The Heat exchanger for deep geothermal system is very important to enhance the efficiency of the system. The co-axial heat exchanger is used due to the limitation of digging space. The heat transfer on the external surface of outer pipe should be high to receive a large amount of heat from the ground. However, the inner pipe should be insulated to reduce the heat loss and increase the temperature of discharge water. This study made experiment apparatus to describe the co-axial heat exchanger and measure the heat transfer coefficients on the internal and external surface. And the pin-fin was designed and fixed on the internal surface to increase the efficiency of heat exchanger. Finally, we calculated the temperature of discharge water using the heat transfer circuit of co-axial heat exchanger and heat transfer coefficient which from experimental results. The water temperature was reached the ground temperature at -500 m and following the ground temperature. When the water return to the ground surface, the water temperature was decreased due to heat loss. As the pin-fin case, the heat transfer coefficient on the internal surface was decreased by 30% and it mean that the pin-fin help to insulate the inner pipe. However, the discharge water temperature did not change although pin-fin fixed on the inner pipe.

설비공학 분야의 최근 연구 동향

이대영(Dae-Young Lee),김사량(Sa Ryang Kim),김현정(Hyun-Jung Kim),김동선(Dong-Seon Kim),박준석(Jun-Seok Park),임병찬(Pyeong Chan Ihm) 대한설비공학회 2017 설비공학 논문집 Vol.29 No.6

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with CO2 as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type’s office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.

지열 히트펌프 시스템의 계절별 지중 열교환 특성 및 지반내 온도 변화

심병완(Shim, Byoung-Ohan) 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.06

The geothermal heat pump system is designed for cooling and heating for three stories building (2,435 m²) includes total 79 heat pumps. Therefore, the monitoring system is installed for each floor and the data is automatically transmitted to the monitoring system. Heat exchange rate and temperature of a geothermal heat pump system have been monitored for a long period. The seasonal operation of geothermal heat pump shows the different shape of heat exchange rate for cooling and heating. Ground water flow can influence on heat exchange rate and thermal storage of the system. In order to define the hydraulic characteristics and groundwater temperature variation, the relationships among air temperatures, groundwater temperatures, water table, and precipitation are analysed.

설비공학회 분야의 최근 연구 동향

이대영(Dae-Young Lee),김현정(Hyun-Jung Kim),김동선(Dong-Seon Kim),박준석(Jun-Seok Park),임병찬(Pyeong Chan Ihm) 대한설비공학회 2018 설비공학 논문집 Vol.30 No.6

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2017. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) In building mechanical system research fields, twenty studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (2) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to the ventilated cavity of curtain-wall system for enhancing insulation and preventing condensation, the improvement plans of condensation defect examples in apartment building and the calculation method for the transmitted solar irradiance using the total horizontal irradiance. The subjects of building energy are worked on the energy consumption characteristics in office buildings, energy performance analysis for energy saving potentials in a hospital building, outdoor air cooling system operated with load prediction, building energy efficiency rating changes by enhanced building envelope standards, energy saving effect for the external insulation construction, energy reduction of a heating network through the application of an absorption heat pump, analysis of thermal load profile according to the window retrofit in an old school building, calculating regional balance point temperature for heating degree-days in korea, short-term load prediction using artificial neural network models, the simple window model applied to EnergyPlus, possibility of building energy saving through the building data, optimal cooling operation of a single family house model equipped with renewable energy facility by linear programming. The remained studies are related to the comparison between korea and china evacuation laws in office building, the effect of cold air stimulation during the driver’s drowsiness, the calculation of the attachedpiping-material rate for the building mechanical-service system in office buildings, the development of a modularlightweight steel ceiling system and the evaluation of local loss coefficients for different waveguide-below-cutoff (wbc) arrays of electromagnetic pulse. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, research subjects include the improvement of Type II and double-effect absorption heat pumps, the seasonal performance of compression heat pumps, a vertical receiver in a compression heat pump, the performance of a domestic built-in ice maker and the performance characteristics of a surface water heat pump system. In the alternative refrigeration/energy system category, subjects include a membrane dehumidification system, a CO₂-hydrate circulation system, a Zeolite 13x chemical thermal energy storage system and the performance criteria for heat pumps as a renewable energy device. In the system control category, subjects include a defrosting control system using photoelectric sensors and the control method for an organic thermal storage-chiller system. (4) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for prediction of stratification model for diffusers in underfloor air distribution system using

설비공학회 분야의 최근 연구 동향

이대영(Dae-Young Lee),김사량(Sa Ryang Kim),김현정(Hyun-Jung Kim),김동선(Dong-Seon Kim),박준석(Jun-Seok Park),임병찬(Pyeong Chan Ihm) 대한설비공학회 2016 설비공학 논문집 Vol.28 No.6

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2015. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering were carried out in the areas of flow, heat and mass transfer, cooling and heating, and air-conditioning, the renewable energy system and the flow inside building rooms. Research issues dealing with air-conditioning machines and fire and exhausting smoke were reduced. CFD seems to be spreading to more research areas. (2) Research works on heat transfer area were carried out in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the economic analysis of GHG emission, micro channel heat exchanger, effect of rib angle on thermal performance, the airside performance of fin-and-tube heat exchangers, theoretical analysis of a rotary heat exchanger, heat exchanger in a cryogenic environment, the performance of a cross-flow-type, indirect evaporative cooler made of paper/plastic film. In the area of pool boiling and condensing, the bubble jet loop heat pipe was studied. In the area of industrial heat exchangers, researches were performed on fin-tube heat exchanger, KSTAR PFC and vacuum vessel at baking phase, the performance of small-sized dehumidification rotor, design of gas-injection port of an asymmetric scroll compressor, effect of slot discharge-angle change on exhaust efficiency of range hood system with air curtain. (3) In the field of refrigeration, various studies were carried in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, a cold-climate heat pump system, CO2 cascade systems, ejector cycles and a PCM-based continuous heating system were investigated. In the alternative refrigeration/energy system category, a polymer adsorption heat pump, an alcohol absorption heat pump and a desiccant-based hybrid refrigeration system were investigated. In the system control category, turbo-refrigerator capacity controls and an absorption chiller fault diagnostics were investigated. (4) In building mechanical system research fields, eighteen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the user and location awareness technology applied dimming lighting control system, the lighting performance evaluation for light-shelves, the improvement evaluation of air quality through analysis of ventilation efficiency and the evaluation of airtightness of sliding and LS window systems. The subjects of building energy were worked on the energy saving estimation of existing buildings, the developing model to predict heating energy usage in domestic city area and the performance evaluation of cooling applied with economizer control. The studies were also performed related to the experimental measurement of weight variation and thermal conductivity in polyurethane foam, the development of flame spread prevention system for sandwich panels, the utilization of heat from waste-incineration facility in large-scale horticultural facilities.

In-situ response test of various borehole depths and heat injection rates at standing column well geothermal heat exchanger systems

Lee, Changhee,You, Jangyoul,Park, Hyeonku Elsevier 2018 Energy and buildings Vol.172 No.-

<P><B>Abstract</B></P> <P>In this study, we analyzed the thermal conductivity characteristics of a well-type underground heat exchanger with respect to the amount of injected heat per meter. Although a constant amount of heat was injected into the system, we compared and analyzed data for different borehole depths. We compared three different injection heat values (250, 300, and 350 W/m). We also analyzed the effective thermal conductivity with respect to different initial ignoring times (2 h, 3 h, and 5 h) based on different rock types and borehole depths. We did not observe a linear relationship between the rock types (alluvium, gneiss, and granite) and the borehole depth. The results suggest that different rock types have different thermal conductivity characteristics and the variation in the results is likely caused by groundwater, which affects the thermal conductivity measurements. For future geothermal heat exchanger designs, it is imperative to select a specific value for heat flow and an appropriate injection heat value depending on the rock type.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We analyzed the thermal conductivity of a well-type underground heat exchanger. </LI> <LI> We compared data for different borehole depths at 3 injection heat values. </LI> <LI> We analyzed effective thermal conductivity by 3 initial ignoring times. </LI> <LI> There is no linear relationship between rock types and the borehole depth. </LI> <LI> Different rock types have different thermal conductivity characteristics. </LI> </UL> </P>

지중열교환기 제어방법에 따른 지열시스템의 냉방 성능 특성 분석

박차식(Chasik Park),박경우(Kyoungwoo Park) 호서대학교 공업기술연구소 2013 공업기술연구 논문집 Vol.32 No.2

본 연구에서는 실증용 현장 사이트에 설치된 분산형 지열 시스템에 대하여 지중열교환기 운전조건에 따른 시스템 성능 특성을 분석하였다. 본 지열 시스템은 밀폐형과 개방형으로 구성된 지중열교환기가 설치되어 있고,지중열원을 지중열교환기의 2차유체와 열교환을 하여 열원을 저장하는 종합지열센터인 축열조와 열펌프로 구성되어 있다. 부하조건에 따라 운전조건을 나누어 종합지열센터인 축열조 내부 온도변화와 시스템 냉방성능 특성을 분석하였다. The pacer is to simulate the cooling performance characteristic or the geothermal system with respect to the operating conditions o f the ground heat exchanger. The distributed geothermal system was composed o f heat pump, a storage tank and ground heat exchangers. The variations o f water temperature in the storage tank was analyzed using the law o f energy conservation. The heat pump modeling was based on the map-based model. Controlling the pump o f the ground heat exchanger resulted in the ability to improve the cooling performance in the geothermal system.

복사패널이 적용된 건물일체형 지열원 시스템의 난방성능 분석

김상진,이진욱,김태연,이승복 한국태양에너지학회 2012 한국태양에너지학회 논문집 Vol.32 No.5

Ground source heat pumps(GSHPs) are among the most efficient and comfortable heating and cooling technologies currently available, because they use the earth’s natural heat to provide heating, cooling, and often, water heating. And Building Integrated Geothermal System(BIGS) is one of GSHPs which install ground heat exchanger(GHE) in energy pile without borehole to save the investment cost. Therefore, the experiment is to evaluate the heating performance of BIGS in Korea. The experimental results indicate that the average heat pump COP and overall system’s COP values are approximately 4.4 and 3.0 in one week. This study shows that the BIGS could be used for heating in Korea.