• 한국유체기계학회 논문집
• /
• 제9권6호
• /
• pp.35-44
• /
• 2006

Operation conditions of a reheat cycle gas turbine for a combined cycle power plant was analyzed. Based on measured performance parameters of the gas turbine, a performance analysis program predicted component characteristic parameters such as compressor air flow, compressor efficiency, efficiencies of both the high and low pressure turbines, and coolant flows. The predicted air flow and its variation with the inlet guide vane setting were sufficiently accurate. The compressor running characteristic in terms of the relations between air flow, pressure ratio and efficiency was presented. The variations of the efficiencies of both the high and low pressure turbines were also presented. Almost constant flow functions of both turbines were predicted. The current methodology and obtained data can be utilized for performance diagnosis.

• 설비공학논문집
• /
• 제13권6호
• /
• pp.505-513
• /
• 2001

A revised VX cycle using ammonia/water as the working fluid is a cycle which is suitable to produce cooling utilizing low temperature hat sources. The cycle was analyzed numerically to investigate the effects of the design and operating conditions on the performance. It was shown that both COP and cooling capacity were significantly influenced by the performance of he rectifier. Insufficient UA of the rectifier reduced both ammonia mass fraction and mass flow rate of the vapor entering the condenser, which produced cooling effect in the evaporator. As the temperature and the mass flow rate of the heat source increased, both COP and exergetic efficiency decreased due to the irreversibilities produced in heat exchangers, but cooling capacity did not vary much. Cooling capacity increased significantly as the coolant temperature decreased, although COP and exergetic efficiency remained nearly constant.

• 설비공학논문집
• /
• 제8권3호
• /
• pp.351-360
• /
• 1996

This study focuses on the development and evaluation of the high efficiency absorption chiller-heater, which can be applied to a direct gas fired, double effect system with 40RT (508,000kJ) cooling capacity. The performance of the absorption chiller-heater is investigated through cycle simulation and experiment to obtain the system characteristics with the inlet tenperature of cooling, chilled water, and gas input flow rate. The efficiency of the different cycles has been studied and the simulation and experiment results show that higher coefficient of performance could be obtained for mixed flow cycle. The five percent difference was obtained from the comparison between experimental and cycle simulation results. As a result of this study, the optimum designs were determined based on the operating conditions and the coefficient of performance.

• 대한기계학회논문집B
• /
• 제36권3호
• /
• pp.293-299
• /
• 2012

대형 선박의 추진용 디젤엔진에서 버려지는 배기가스의 열을 회수하기 위한 랭킨사이클이 적용된 발전시스템에 대하여 R245fa 및 water 의 작동유체들에 따른 열역학적 효율 특성을 분석하였다. 그 이론적인 계산 결과로, 고정된 질량유량의 R245fa 에 대하여 터빈입구의 압력이 증가할수록 사이클, 시스템, 및 전체적 효율이 증가하였고, 사이클에 의해 발생되는 순동력도 증가하는 특성을 보였다. 반면, water 의 경우에는 R245fa 에 비하여 더 낮은 질량유량 및 터빈입구 압력의 비율에서 최대의 시스템 효율을 보였다. 또한 water 에 대하여 최적화된 사이클의 순출력, 시스템 효율, 및 전체적 효율의 값들은 R245fa 의 경우보다 더 크게 나타났다.

• 한국자동차공학회논문집
• /
• 제19권5호
• /
• pp.58-66
• /
• 2011

A 2-loop waste heat recovery system with Rankine steam cycles for the improvement of fuel efficiency of gasoline vehicles has been investigated. A high temperature loop(HT loop) is a system to recover the waste heat from the exhaust gas, a low temperature loop(LT loop) is for heat recovery from the engine coolant cold relatively. This paper has dealt with a layout of a LT loop system, the review of the working fluids, and the design of the cycle. The design point and the target heat recovery of the LT boiler, a core part of a LT loop, has been presented and analytically investigated. Considering the characteristics of the cycle, the basic concept of the LT boiler has been determined as a shell-and tube type counterflow heat exchanger, the performance characteristics for various design parameters were investigated.

• Journal of Advanced Marine Engineering and Technology
• /
• 제37권6호
• /
• pp.575-581
• /
• 2013

본 논문은 R744-R404A 캐스케이드 냉동시스템의 최적 냉매 충전을 위해 과냉도, 과열도, 내부열교환기 효율 등에 대한 영향을 분석한 것이다. 연구에 사용된 캐스케이드 냉동시스템의 고온 사이클에는 R404A, 저온 사이클에는 R744를 적용하였다. 그 주요 결과는 다음과 같다 : 고온 사이클의 과냉도, 과열도, 내부열교환기 효율과 저온 사이클의 증발온도와 압축효율은 크게 할수록 질량유량비가 작게 나타났다. 그리고 캐스케이드 온도차와 고온 사이클의 증발온도, 응축온도와 저온 사이클의 과냉도, 과열도, 내부열교환기 효율은 작을수록 질량유량비가 작게 나타났음을 확인하였다.

• 가정과삶의질연구
• /
• 제9권2호
• /
• pp.155-170
• /
• 1991

The purpose of the study was to investigate the effects of demographic-socialogical variables.(ie. educational level, duration of marriage, mate selection type, monthly income, number of children and the frequencies of family's jonit-leisure-activity) and efficiency of the interspous communication on marital satisfaction over the family life cycle. The subject were 278 husbands and wives living in Seoul area who had the eldest child attending at elementary school, middle school , high school and university , respectively. The families were categorized to Duvall's family life cycle. Before the main study was conducted from SEP. 27 to OCT. 8. 1990. a pre-test was conducted on 52 subjects form SEP. 20 to SEP.23.1990. The values of Chronbach's α were obtained on the efficiency of the interspouse communication (α =0.885) and marital satisfaction (α=0.939). Data analysis was by Chronbach's α, ANOVA. Pearson's Product Moment Correlation. Path Analysis and Multiple Regression Analysis. The results were as follows; 1) Marital Satisfaction was positively related (1) to demographic-socialogical variables; educational level , monthly income, the frequencies of family's joint-leisure-activity (2) the efficiency of the interspouse communication. 2) Efficiency of the interspouse communication was positively related to the frequencies o family's joint-leisure-activity. 3) The relative importance of independent variables on marital satisfaction over the family life cycle was found to be varied in each stage of life cycle. (1) As for the group who had elementary-school-aged children; efficiency of the interspouse communication (β=0.717.p<.001), joint-leisure-activity frequency (β =0.303.p<.001), monthly income(β=0.202.p<.001), mate selection type(β=0.180.p<.05), (2) As for the group who had middle-school-aged children; efficiency of the interspouse communication (β=0.702.p<.001), (3)As for the group who had high school-aged children; efficiency of the interspouse communication (β=0.488.p<.001), joint-leisure-activity frequency (β=0.368.p<.001), (4)the group who had university-aged children; efficiency of the interspouse communication.(β=0.729.p<.001), monthly income (β=0.164.p<.01). The regression model showed that 55 percent of the marital satisfaction could be account for by demographic-socialogical variables and efficiency of the interspouse communication (R2=0.551)

• 한국유체기계학회 논문집
• /
• 제18권4호
• /
• pp.5-12
• /
• 2015

Several working fluids for Organic Rankine Cycle(ORC) were recommended by many researchers. However, the recommended optimal working fluids were not exactly same because the operating conditions of ORC and application were different. The major parameter to select the working fluid for ORC was the temperature of available thermal energy. In this study, low-grade thermal energy was used for the heat source for ORC and the appropriate working fluids were searched among 26 candidate working fluids. The requirements to be a working fluid for ORC were reviewed and the cycle analysis for simple cycle was conducted with $75^{\circ}C$ and $35^{\circ}C$ at the turbine inlet and exit, respectively. R600, R601, toluene were best candidates if the system could work without leaking the working fluid. Next, R236ea, R245ca, R245fa were recommended because they are not inflammable working fluids as well as better efficiency.

• Journal of Advanced Marine Engineering and Technology
• /
• 제36권8호
• /
• pp.1151-1157
• /
• 2012

OTEC기술은 신재생에너지 기술 중의 하나로 따듯한 표층수와 차가운 심층수의 온도차를 이용하여 전력을 생산하는 기술이다. 작동유체의 선정과 OTEC 사이클의 상태에 따라 에너지효율과 환경적인 측면에 많은 영향을 준다. OTEC의 작동유체로는 ammonia, R22, R407C, R410A가 있다. 본 논문에서는 OTEC 시스템의 최적화를 위해 $25^{\circ}C$에서의 증발압력를 비교하였다. 또한 밀폐사이클과 재생사이클에서의 작동유체에 따른 출력과 효율에 대하여 연구하였다.

• 상하수도학회지
• /
• 제24권2호
• /
• pp.203-210
• /
• 2010

The signification of calorie/water (C/W) ratio was investigated in the treatment of highly concentrated organic wastes by thermophilic oxic process (TOP). Swine waste was used in this study. When C/W ratio was 1.6, most of swine waste was decomposed and all water was evaporated in the 24-h injection cycle. To improve treatment efficiency of TOP treating swine waste, the effect of shortening the swine waste injection cycle was examined. The shortening of injection cycle was conducted to stimulate the activity of thermophilic bacteria. A high temperature in the reactor was maintained by shortening of the injection cycle. When the swine waste injection cycle was shortened, the C/W ratio was fixed at 1.6. As a result, by shortening the swine waste injection cycle from 24-h to 12 and 6-h, the maximum loading rate of swine waste per day could be improved 1.9 and 3.5 times, respectively.