• 설비공학논문집
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• 제12권12호
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• pp.1098-1125
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• 2000

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 1998 and 1999 has been done. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environment. The conclusions are as follows. 1) A review of the recent studies on fluid flow, turbomachinery and pipe-network shows that many experimental investigations are conducted in applications of impingement jets. Researches on turbulent flows, pipe flows, pipe-networks are focused on analyses of practical systems and prediction of system performance. The results of noise reduction in the turbomachinery are also reported. 2) A review of the recent studies on heat transfer analysis and heat exchanger shows that there were many papers on the channel flow with the application to the design of heat exchanger in the heat transfer analysis. Various experimental and numerical papers on heat exchanger were also published, however, there were few papers available for the analysis of whole system including heat exchanger. 3) A review of the recent studies on heat pump system have focused on the multi-type system and the heat pump cycle to utilize treated sewage as the heat source. The defrosting and the frosting behaviors in the fin-tube heat exchanger is experimentally examined by several authors. Several papers on the ice storage cooling system are presented to show the dynamic simulation program and optimal operation conditions. The study on the micro heat pipes for the cooling of high power electronic components is carried out to examine the characteristics of heat and mass transfer processed. In addition to these, new type of separate thermosyphon is studied experimentally. 4) The recent studies on refrigeration/air conditioning system have focused on the system performance and efficiency for new alternative refrigerants. New systems operating with natural refrigerants are drawing lots of attention. In addition to these, evaporation and condensation heat transfer characteristics of traditional and new refrigerants are investigated for plain tubes and also for microfin tubes. Capillary tubes and orifice are main topics of research as expansion devices and studies on thermophysical properties of new refrigerants and refrigerant/oil mixtures are widely carried out. 5) A review of the recent studies on absorption cooling system shows that numerous experimental and analytical studies on the improvement of absorber performance have been presented. Dynamic analysis of compressor have been performed to understand its vibration characteristics. However research works on tow-phase flow and heat transfer, which could be encountered in the refrigeration system and various phase-change heat exchanger, were seemed to be insufficient. 6) A review of recent studies on duct system shows that the methods for circuit analysis, and flow balancing have been presented. Researches on ventilation are focused on the measurement of ventilation efficiency, and variation of ventilation efficiency with ventilation methods by numerous experimental and numerical studies. Furthermore, many studies have been conducted in real building in order to estimate indoor thermal environments. Many research works to get some information for cooling tower design have been performed but are insufficient. 7) A review on the recent studies on architectural thermal environment and building mechanical systems design shows that thermal comfort analysis is sitting environment, thermal performance analysis of Korean traditional building structures., and evaluation of building environmental load have been performed. However research works to improve the performance of mechanical system design and construction technology were seemed to be insufficient.

• 설비공학논문집
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• 제16권12호
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• pp.1234-1268
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• 2004

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2002 and 2003 has been carried out. Focus has been put on current status of research in the aspect of heating, cooling, air-conditioning, ventilation, sanitation and building environment/design. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation in diverse facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat transfer, humidity was also interesting to promote comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing research topics. Well developed CFD technologies were widely applied for analysis and design of various facilities and their systems. (2) Heat transfer characteristics of enhanced finned tube heat exchangers and heat sinks were extensively investigated. Experimental studies on the boiling heat transfer, vortex generators, fluidized bed heat exchangers, and frosting and defrosting characteristics were also conducted. In addition, the numerical simulations on various heat exchangers were performed and reported to show heat transfer characteristics and performance of the heat exchanger. (3) A review of the recent studies shows that the performance analysis of heat pump have been made by various simulations and experiments. Progresses have been made specifically on the multi-type heat pump systems and other heat pump systems in which exhaust energy is utilized. The performance characteristics of heat pipe have been studied numerically and experimentally, which proves the validity of the developed simulation programs. The effect of various factors on the heat pipe performance has also been examined. Studies of the ice storage system have been focused on the operational characteristics of the system and on the basics of thermal storage materials. Researches into the phase change have been carried out steadily. Several papers deal with the cycle analysis of a few thermodynamic systems which are very useful in the field of air-conditioning and refrigeration. (4) Recent studies on refrigeration and air-conditioning systems have focused on the system performance and efficiency enhancement when new alternative refrigerants are applied. Heat transfer characteristics during evaporation and condensation are investigated for several tube shapes and new alternative refrigerants including natural refrigerants. Efficiency of various compressors and performance of new expansion devices are also dealt with for better design of refrigeration/air conditioning system. In addition to the studies related with thermophysical properties of refrigerant mixtures, studies on new refrigerants are also carried out. It should be noted that the researches on two-phase flow are constantly carried out. (5) A review of the recent studies on absorption refrigeration system indicates that heat and mass transfer enhancement is the key factor in improving the system performance. Various experiments have been carried out and diverse simulation models have been presented. Study on the small scale absorption refrigeration system draws a new attention. Cooling tower was also the research object in the respect of enhancement its efficiency, and performance analysis and optimization was carried out. (6) Based on a review of recent studies on indoor thermal environment and building service systems, it is noticed that research issues have mainly focused on several innovative systems such as personal environmental modules, air-barrier type perimeterless system with UFAC, radiant floor cooling system, etc. New approaches are highlighted for improving indoor environmental conditions and minimizing energy consumption, various activities of building energy management and cost-benefit analysis for economic evaluation.

• 대한기계학회논문집B
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• 제34권5호
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• pp.491-498
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• 2010

연료전지 자동차는 성능과 수명 측면에서, 전해질막의 가습이 필요하며, 이를 위해 반응기체인 공기, 수소의 높은 가습이 요구된다. 본 연구에서는 내경 75 mm공기공급관 내에 직접 삽입된 인젝터(노즐)과 액적제거를 위한 사이클론을 통한 가습장치를 고안하여 실험을 수행하였다. 충돌형 노즐 3 종류를 이용하여 분사압력, 공기 유량, 분사방향각도를 달리하여 실험을 수행하였다. 가습 성능을 분석하기 위해, 가습효율이라는 개념을 정의하였다. 별도의 외부 열공급원 없이 분사되는 물과 공기의 엔탈피가 자체 기화열 공급원으로, 분사되는 물의 양이 가습에 가장 중요한 변수임을 볼 수 있었다. 사이클론은 높은 공기유량에서 재비산이 발생되는 것을 볼 수 있었다. 노즐타입 PJ24, 분사방향 각도 90도, 분사압력 1200 kPa, 공기 유량 6000 nlpm에서 절대습도 $21.29\;kJ/kg_{da}$, 가습 효율 86.57%를 얻을 수 있었다.

• 공업화학
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• 제30권3호
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• pp.331-336
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• 2019

본 연구에서는 리튬이차전지의 초기 효율과 율속 특성의 향상을 위해 피치계 소프트 카본 음극재의 요구 물성 및 제조 공정변수에 대한 실험을 진행하였다. 피치는 석유계 잔사유를 사용하여 공정 온도를 변수로 합성하였다. 공정온도를 각각 360, 370, $410^{\circ}C$에서 3 h 진행하여, 86, 98, $152^{\circ}C$의 연화점을 갖는 피치를 제조하였다. 피치의 원소분석과 열적 특성을 EA 분석과 TGA 분석을 통해 고찰한 결과, 높은 연화점을 갖는 경우 낮은 H/C 및 발달된 열적안정성을 관찰할 수 있었다. 얻어진 피치를 $1,200^{\circ}C$에서 1 h 동안 탄화 열처리 공정을 진행하여 소프트 카본계 음극재를 제조하였다. XRD 분석을 통해 결정 구조를 고찰한 결과, 연화점이 높은 피치에서 제조된 소프트 카본은 상대적으로 고비점의 성분들로 구성되어 탄화 열처리공정 시 증발 성분의 감소 및 고리화에 참여하는 성분들의 증가로 인하여 결정성이 증가하였음을 고찰할 수 있었다. 결정성이 향상된 소프트 카본계 음극재에서 향상된 초기 효율과 율속 특성의 결과를 얻을 수 있었다. 향상된 초기 효율 및 율속 특성은 소프트 카본계 음극재의 발달된 결정 구조에서 기인하는 메커니즘에 대하여 논의하였다.

• 한국환경기술학회지
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• 제19권6호
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• pp.570-575
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• 2018

폐수수탁처리업에 반입되는 산업폐수의 원수 성상이 매일 달라짐에 따라 전처리 공정인 응집침전공정의 효율적 운전이 어려운 실정이며, 이로 인해 후처리공정인 증발농축 및 대체 공정인 membrane 공정의 부하원인이 되고 있다. 이에 본 연구에서는 산업폐수의 효율적 처리를 위해 응집제 주입 방법별(단독주입, 동시주입, 순차주입, 역주입) 응집특성을 비교하기 위해 NaOH 주입 전 후 폐수 원수를 채수하여 실험하였다. 응집실험은 Jar-tester를 이용하여 진행하였다. 응집제주입방법별 TDS 제거효율은 순차주입(2.8 %) < 단독주입(3.9 %) < 동시주입(8.1 %) < 역주입(9.6 %) 순으로, TOC 제거효율은 단독주입(84.3 %) < 역주입(86.2 %) < 순차주입(88.6 %) < 동시주입(89.1 %) 순으로, 탁도 제거효율은 단독주입(99.7 %) < 순차주입(99.8 %) ${\fallingdotseq}$ 역주입(99.8 %) < 동시주입(99.9 %) 순으로 각각 나타내어, 이를 종합적으로 고려하여 판단한 결과 순차주입방법(무기응집제${\rightarrow}$고분자응집제)보다 무기응집제 및 고분자응집제를 동시에 주입하는 방법이 더 효율적인 것으로 나타났다.

• 한국축산시설환경학회지
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• 제14권3호
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• pp.193-200
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• 2008

양돈농가에서 설치되어 운영되고 있는 퇴비화시설에 대한 수분 증발량에 대한 조사결과를 요약하면 다음과 같다. 1. 돼지사육 두수는 단순 퇴비사 1,433두/호, 기계교반 퇴비화 시설 설치농가는 3,500두/호 이었다. 2. 퇴비화시설의 용적은 단순 퇴비사 $0.33m^3$/두, 기계교반 퇴비화시설 설치농가는 $0.25m^3$/두로 퇴비화시설 용적이 약 24.2% 정도 적은 것으로 조사되었다. 3. 조사농가의 수거돈분의 평균 수분 함량은 단순퇴비사 86.8%, 기계교반 85.7%로 기계교반 퇴비화시설 설치농가의 돈분의 수분 함량이 약 1.3% 정도 낮은 것으로 조사되었다. 4. 1일 투입되는 수분량은 단순 퇴비사 $4.1kg/m^3$/일, 기계교반 퇴비화시설 설치농가는 $6.5kg/m^3$/일로 기계교반 설치농가에서 약 36.9% 정도 단위면적당 수분량이 높게 투입되는 것으로 조사되었다. 5. 퇴비화기간동안의 발효온도는 단순퇴비화 시설에서 최고온도가 $45^{\circ}C$ 정도 상승하였으나, 기계교반 퇴비화시설 설치농가에서의 최고 발효온도는 $70^{\circ}C$까지 상승하는 것으로 조사되었다. 6. 수분 감소량은 퇴비화 시설 $1m^3$당 단순퇴비사 3.7 kg, 기계교반 5.2 kg으로 기계교반 퇴비화 시설이 약 28.8% 높은 것으로 조사되었는데 이는 퇴비더미내 발효온도 차이에 의한 원인인 것으로 판단되어졌다. 7. 퇴비화후 비료성분 함량은 질소 함량은 각각 0.84% 및 0.86%로 비슷한 경향으로 조사되었으며, ${P_2}{O_5}$(%) 성분도 0.78% 및 0.74%로 단순퇴비화시설에서 약간 높은 경향을 보였다. 그러나 OM 및 OM/N은 처리간에 큰 차이가 없는 것으로 조사되었다. 8. 따라서 양돈농가에서의 기계교반 및 단순퇴비화 시설을 이용하여 돈분뇨를 퇴비화하는 경우 돈분의 수분함량과 발효온도 및 수분 증발가능량 등을 고려하여 퇴비화 효율을 향상시키는 노력이 필요할 것으로 생각된다.

• 한국태양에너지학회 논문집
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• 제27권3호
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• pp.7-13
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• 2007

A Dish type solar concentrating system consists of a parabolic concentrator and a cavity receiver. In order to achieve high temperatures from solar energy, it is essential to efficiently reflect the solar rays in the concentrator and to minimize thermal losses in the cavity receiver. Improving the economical efficiency of a solar power system required the stirling unit to be operated continuously. For continuous operation of the stilting unit, the receiver must be continuously provided with thermal energy from solar as well as additional combustion heat. It is possible for a hybrid solar receiver system equipped with an additional combustion to be operated 24 hrs/day. A hybrid solar receiver was designed and manufactured for a total thermal load of 35 kW in the operating temperature range $700^{\circ}C$ to $800^{\circ}C$. The hybrid receiver system was tested in gas-only mode by gas-fired heat to investigate thermal characteristics at inclination angle varying from 0 deg to 30 deg(cavity facing down) and the aperture to cavity diameter ratios of 0(closed cavity) and 1.0(open cavity). This paper has been conducted to measure temperature distribution in cavity surface and to analyze thermal resistances, and the evaporation and condensation heat transfer coefficient in all cases(open and closed cavity).

• 한국화재소방학회논문지
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• 제22권3호
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• pp.216-220
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• 2008

물분무소화설비는 화원의 냉각, 주변공기의 희석, 미세한 물방울의 증발에 의한 열차단과 같은 소화특성을 이용한다. 미분무수의 운동량은 입자가 큰 물방울에 비해 상대적으로 낮으며 화원의 침투능력도 효과적이지 못하다. 증발된 수증기에 의한 기여는 무게가 가볍고 밀도가 희박하여 화원에 일부분으로 제한되는 경향이 있다. 반면, 사이클식 미분무 패턴은 성층화된 분무 특성에 의해 공기 추출능력과 침투력이 개선될 것으로 예상된다. 이 논문에서는 유체공학적 화재모델인 FDS를 사용하여 교번식 미분무 패턴에 대해 분석된 소화능력을 다룬다. 저자는 이 분석이 미분무 노즐의 표본을 개발하기 위한 기본 개념을 제공할 수 있기를 기대한다.

• 설비공학논문집
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• 제24권5호
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• pp.391-400
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• 2012

In this study, performance of HFC32/HFC152a mixture is measured in the composition range of 20 to 50% R32 with an interval of 10% for the comparison with the conventional HCFC22 in water-source heat pumps. Tests are carried out under the same capacity in a heat pump bench tester equipped with a variable speed compressor at the evaporation and condensation temperatures of 7/$45^{\circ}C$ and -7/$41^{\circ}C$ for summer and winter conditions, respectively. Test results show that the compressor power of the HFC32/HFC152a mixture is 13.7% lower than that of HCFC22 while the coefficient of performance(COP) the HFC32/HFC152a mixture is 15.8% higher than that of HCFC22. Hence, from the view point of energy efficiency, the HFC32/HFC152a mixture is excellent as compared to HCFC22. Compressor discharge temperatures of HFC32/HFC152a mixture are increased up to $15.4^{\circ}C$ as compared to that of HCFC22. The amount of charge for HFC32/HFC152 mixture decrease up to 27% as compared to that of HCFC22. Overall, HFC32/ HFC152a mixture is an excellent long term candidate to replace HCFC22 in water-source heat pumps.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.250-250
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• 2012

Organic light-emitting diodes (OLED) and polymer light emitting diodes (PLED) have been regarded as the candidate for the next generation light source and flat panel display. Currently, the most common OLED industrial fabrication technology used in producing real products utilizes a fine shadow mask during the thermal evaporation of small molecule materials. However, due to high potential including low cost, easy process and scalability, various researches about solution process are progressed. Since polymer has some disadvantages such as short lifetime and difficulty of purifying, small molecule OLED (SMOLED) can be a good alternative. In this work, we have demonstrated high efficient solution-processed OLED with small molecule. We use CBP (4,4'-N,N'-dicarbazolebiphenyl) as a host doped with green dye (Ir(ppy)3 (fac-tris(2-phenyl pyridine) iridium)). PBD (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) and TPD (N,N'diphenyl-N,N'-Bis (3-methylphenyl)-[1,1-biphenyl]-4,4'-diamine) are employed as an electron transport material and a hole transport material. And TPBi (2,2',2''-(1,3,5-phenylene) tris (1-phenyl-1H-benzimidazole)) is used as an hole blocking layer for proper hole and electron balance. With adding evaporated TPBi layer, the current efficiency was very improved. Among various parameters, we observed the property of OLED device by changing the thickness of hole transporting layer and solvent which can dissolve organic material. We could make small molecule OLED device with finding proper conditions.