• 제목/요약/키워드: Heat & Cooling Energy

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이산화탄소 냉방운전 시 냉매충전량 및 운전조건에 따라 내부열교환기가 성능에 미치는 영향 (Effects on Performance of an Internal Heat Exchanger According to Charge Amount and Operating Condition in $CO_2$ Cooling Mode)

  • 곽명석;조홍현
    • 한국지열·수열에너지학회논문집
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    • 제8권1호
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    • pp.13-20
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    • 2012
  • This is an experimental study on the performance characteristics of effective heat pump in the cooling mode using a single-stage compression $CO_2$ cycle with an IHX(internal heat exchanger). The performance of a single-stage compression with IHX was investigated according to charge amount and operating condition. Moreover, the performance characteristic of cooling operating was analyzed with the length of IHX. As a result, the optimum refrigerant charge amount was 2.2 kg. The optimal system COP for compressor frequency of 30, 40, 50, and 60 Hz was 3.493, 3.228, 2.978, and 2.659, respectively. Since the system with IHX can maintain large cooling capacity regardless of operating condition, the system performance doesn't reduce considerably under unfavorable condition. When the compressor frequency was 40 Hz, the COP for a system with IHX length of 3 m and 5 m was 3.361 and 3.51, respectively. By using the IHX into a $CO_2$ cooling system, the performance and reliability improves simultaneously.

지역의 경관을 고려한 도막방수재의 색채별 사계절 차열 및 축열 성능에 관한 연구 (A Study on the Four-Season Cooling Performance by Color of Water Proofing Membrane Materials Considering the View of Area)

  • 고진수;김병윤
    • 한국농촌건축학회논문집
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    • 제17권2호
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    • pp.9-16
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    • 2015
  • This study comparatively analyzed thermal characteristics of the green color, which is currently used the most, and other various colors of a rooftop urethane water proofing sheet. This study also analyzed the cooling performance by color of the water proofing sheet that fused cooling paints, and presented the effective water proofing sheet color for building energy savings. The experimental results are as follows: (1) The value of L (brightness) diminished, and brilliance also became lower from the white color to the black color, and thus, it was confirmed that relatively more heat was absorbed. In a and b chromaticity, which is the color attribute that ignores brightness, no special relationship was identified. (2) Considering that the cooling performance effect is bigger in summer than winter, due to heat reflection, the white water proofing sheet is more effective in building energy savings than the green water proofing sheet that is currently used the most. (3) The water proofing sheet's color has an impact more on cooling performance than the color of the background side of a structure on which water proofing sheet is installed. The experiment object of gray, of which background side is similar to cement mortar, was lower by $5.7^{\circ}C$ than the white background side.

축열식 지열원 히트펌프 시스템의 냉방기간 실증운전 결과 및 운영비용 분석 (Empirical Results and Operational Cost Analysis of Geothermal Heat Pump System using Thermal Energy Storage in Cooling Season)

  • 김득원;이동원;허재혁;김민휘
    • 설비공학논문집
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    • 제30권4호
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    • pp.167-174
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    • 2018
  • The geothermal heat pump systems were installed for heating and cooling of public buildings in Jincheon Eco-friendly Energy town. The heat pump system was operated at night to save on operational costs, and the cold heat was stored in thermal energy storage (TES). In this study, the performance of geothermal heat pump systems with the TES during the summer season was analyzed, and the operational costs with and without the TES were compared. The electric chiller model was used to simulate a heat pump applied without the TES system. Electric rates of each system were measured to calculate operational costs. When the TES is used in the air conditioning system, the electric load (30.4 MWh) calculated in the daytime can move to off-peak load time, and the operational cost is reduced by 36~54%.

남부지역 주거건물의 외피단열변화에 따른 에너지소비량 예측 (Prediction of the Amount of Energy Consumption by Variation in Envelope Insulation on a Detached House in Southern Part of Korea)

  • 문진우;한승훈;오세규
    • 한국주거학회논문집
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    • 제22권1호
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    • pp.115-122
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    • 2011
  • This study aimed at quantifying the impact of envelope insulation on energy consumption for thermal controls in residential buildings in southern part of Korea. A series of parametric simulations for a range of R-values of walls, roof, floor, and windows were computationally conducted for a prototypical Korean detached house. Analysis revealed that the total amount of heat gain was larger than that of heat loss, while the amount of energy for cooling was smaller than that for heating due to the difference of system efficiency; the envelope heat transfer was more significant for the heat loss, thus, the increase of the envelope insulation was more effective to reduce heating load; and there were certain levels of envelope insulation after which the energy saving effect was not significant. These findings are expected to be a fundamental database for the decision of proper insulation level in Korean residential buildings.

설비공학 분야의 최근 연구 동향 : 2016년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2016)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제29권6호
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    • pp.327-340
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    • 2017
  • 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 $CO_2$ 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.

R452B 냉매 적용 물대물 지열원 히트펌프 유닛의 냉난방 운전 성능 특성 (Heating and Cooling Performance Characteristics of a Water-to-Water Heat Pump with R452B Refrigerant)

  • 최연성;강희정;김은오
    • 한국지열·수열에너지학회논문집
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    • 제13권4호
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    • pp.14-20
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    • 2017
  • Refrigerant having high global warming potentials will be phased out due to environmental protection issues. R410A has been widely used in geothermal heat pump. However, it has a little high GWP by 2088 value. One of the recommended substitute for R410A refrigerant is R452B which having a GWP by 698 value. In this paper, the heating and cooling performance of the water-to-water geothermal heat pump unit with R452B was experimentally investigated. The performance of the heat pump adopting R452B was also compared with the system applying R410A. The heating and cooling capacity of R452B heat pump system showed a slightly lower values within 2% comparing with R410A system. However, the R452B system's coefficient of performance was enhanced by 5.2% and 13.7% at heating and cooling mode, respectively.

$Na_4P_2O_7{\cdot}10H_2O$의 축열방열시 열전달 특성에 관한 실험적 연구 (An experimental study of heat transfer with $Na_4P_2O_7{\cdot}10H_2O$ as P.C.M.)

  • 이채문;임장순
    • 태양에너지
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    • 제9권1호
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    • pp.70-77
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    • 1989
  • Sodium pyrophosphate that melting point is $79-80^{\circ}C$ have been Studied on heat storage and heat discharge. In heat storage process, sodium pyrophosphate was kept up initial temperature $50^{\circ}C,\;60^{\circ}C,\;70^{\circ}C$ which melt by heated water at temperature $85^{\circ}C,\;90^{\circ}C,\;95^{\circ}C$. In heat discharge process, initial temperature of sodium pyrophosphate was maintained at temperature $85^{\circ}C,\;90^{\circ}C,\;95^{\circ}C$ which varied cooling temperature $50^{\circ}C,\;60^{\circ}C,\;70^{\circ}C$. The experiment has been reached conclusions as follows. 1) Heat transfer properties of phase change material is controlled by conduction during heating and cooling process. 2) The temperature increased rapidly at initial stage and transient region increase slowly because of characteristic of latent heat. 3) The lower cooling water temperature is the less the time that get to thermal equivalent state take during discharge process. 4) The higher cooling water temperature is the less temperature difference between top and bottom in P.C.M during discharge process.

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열전모듈 냉장고의 에너지 효율에 미치는 설계인자의 영향 (The Effect of Design Parameters on the Energy Efficiency of a TEM Refrigerator)

  • 이태희;김진호
    • 한국지열·수열에너지학회논문집
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    • 제14권3호
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    • pp.29-34
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    • 2018
  • To present the design direction of the thermoelectric module (TEM) refrigerator, analysis of the effect of the design parameters on the energy efficiency and performance of the refrigerator is performed. The design parameters considered are the cooling capacity of the TEM and the heat transfer performance of the heating and cooling surface of the TEM. The heat transfer performance is the most effective design parameter for improving cooling power. The smaller ΔT and cooling capacity of the TEM make the higher efficiency of the refrigerator.

냉각속도가 지르칼로이-4 피복관의 취성에 미치는 영향 (Effect of Cooling Rate on the Behavior of the Embrittlement in Zircaloy-4 Cladding)

  • 김준환;이명호;최병권;정용환
    • 열처리공학회지
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    • 제18권2호
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    • pp.112-118
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    • 2005
  • Study was focused on the effect of the cooling rate on the embrittlement behavior of Zircaloy-4 cladding simulated Loss Of Coolant Accident (LOCA) environment. Claddings were oxidized at given temperature and given time followed by various water quenching in the range of $0.6^{\circ}C$ and $100^{\circ}C$ per second. Cladding failed after water quenching above the threshold oxidation. Threshold oxidation was decreased as the cooling rate increased, which is due to the matensite structure formed during fast cooling rate.

그래핀 입자의 크기와 혼합비율이 나노유체의 비등열전달에 미치는 영향에 대한 실험적 연구 (A Experimental Study on the Boiling Heat Transfer Characteristics of Nanofluids by the Size and Mixing Ratio of Graphene Particle)

  • 박성식;김영훈;김남진
    • 한국태양에너지학회 논문집
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    • 제35권2호
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    • pp.53-62
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    • 2015
  • Boiling heat transfer characteristic is very important in the various industries such as solar thermal system, power generation, heat exchangers, cooling of high-power electronics components and cooling of nuclear reactors. Therefore, in this study, boiling heat transfer characteristics such as critical heat flux (CHF) and heat transfer coefficient under the pool boiling state were tested using graphene nanofluids. Graphene used in this study, which have the same thermal conductivity but with different sizes. The experimental results showed that the highest the CHF and boiling heat transfer coefficient increase ratio for graphene nanofluids was at the 0.01 vol.%. At the present juncture, the CHF and boiling heat transfer coefficient increase ratio of the small-sized graphene nanofluids was higher than the large-sized graphene nanofluids.