• 신재생에너지
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• 제9권4호
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• pp.32-39
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• 2013

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 is used to recover waste heat from exhaust gas and a low temperature loop is used to recover waste heat from cold engine coolant. This paper has dealt with a layout of low temperature loop system, the review of the velocity contours through numerical analysis. According to the result of analysis, the designed heat exchanger. And comparing with flow analysis results, LT Boiler is safe to operation.

• 대한기계학회논문집B
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• 제40권2호
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• pp.69-73
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• 2016

최근 자동차 엔지니어들은 자동차 엔진의 열효율을 향상시키기 위한 수단으로 폐열 회수 기술에 많은 관심을 기울이고 있다. 배기량이 큰 가솔린 엔진은 대체로 V형인데, 열 회수를 위해 두 개의 슈퍼히터를 각각의 배기 다기관 가까이에 설치하는 것은 비용 면에서 효율적이지 않다. 하나의 슈퍼히터를 한쪽 배기 다기관에 최대한 가깝게 부착하면 좀 더 높은 열교환 효율을 얻을 수 있으나 폐열회수를 위한 배기가스의 유량은 절반이 된다. 반면에, 배기가스의 유량을 전부 이용하기 위하여 두 배기관이 합류된 지점에 슈퍼히터를 설치하면 배기가스의 온도는 많이 감소된다. 이 사실을 바탕으로 슈퍼히터의 최적 위치를 조사하기 위하여 상용프로그램인 AMESim을 이용해 해석을 수행하였다. 이 때, 배기가스 유량 중 절반만을 사용하더라도 슈퍼히터를 배기 다기관과 최대한 가까이 부착하는 것이 엔진의 배기가스로부터 3.8 kW의 열을 더 회수할 수 있는 것으로 나타났다. 이 결과를 바탕으로 최적의 폐열 회수 모델을 도출하고 제안하였다.

• 한국자동차공학회논문집
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• 제20권2호
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• pp.21-29
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• 2012

A dual 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) only recovers the heat of the exhaust gas. A low temperature loop (LT loop) recovers the residual heat from the HT loop, the coolant heat and the remaining exhaust gas heat. The two separate loops are coupled with a heat exchanger. This paper has dealt with a layout of the dual loop system, the review of the working fluids, and the design of the cycle. The design point and the target heat recovery of the HT boiler, a core part of a HT loop, have been presented. The prototype of the HT boiler was evaluated by experiment. For the performance evaluation of the HT boiler, inlet temperature of the HT boiler working fluid was set equal to the temperature degree of sub-cool of $5^{\circ}C$ at the condensing pressure. The exit condition was the degree of super-heat set at $5^{\circ}C$. The characteristics of the HT boiler such as heat recovery and pressure drops of fluids were evaluated with varying flow rates and inlet temperatures of exhaust gas under various evaporating pressure conditions.

• 설비공학논문집
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• 제25권4호
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• pp.180-186
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• 2013

An electric vehicle is an environment-friendly automobile which does not emit any tailpipe pollutant. In a conventional vehicle with an internal combustion engine, the internal cabin of the vehicle is usually heated using waste heat from the engine. However, for an electric vehicle, an alternative solution for heating is required because it does not have a combustion engine. Recently, a heat pump system which is widely used for residential heating due to its higher efficiency has been studied for its use as a heating system in electric vehicles. In this study, a heat pump system utilizing air source and waste heat source from electric devices was investigated experimentally. The performance of the heat pump system was measured by varying the mass flow rate ratio. The experimental results show that the heating capacity and COP in the dual heat source heat pump were increased by 20.9% and 8.6%, respectively, from those of the air-source heat pump.

• 에너지공학
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• 제21권4호
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• pp.411-418
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• 2012

본 연구에서는 가솔린 엔진 자동차의 엔진 폐열 회수를 위한 이중 회로 랭킨 사이클 시스템에서 용적형 팽창기의 설계 팽창비에 따른 성능 해석이 수행되었다. 자동차 엔진 폐열 이용 랭킨 사이클 시스템에 사용되는 용적형 팽창기는 운전 조건에 따라 설계 팽창비가 운전 압력비보다 낮은 저팽창 조건과 설계 팽창비가 운전 압력비보다 높은 과팽창 조건으로 운전되므로 탈설계 조건에서 성능 예측이 중요하다. 또한 용적형 팽창기는 자동차 적용시 팽창효율 뿐만 아니라 부피와 무게를 최소화하는 것이 매우 중요하므로 이를 고려한 설계 팽창비의 최적화가 요구된다. 본 연구에서는 용적형 팽창기의 탈설계 조건에서 성능 예측을 통해 팽창효율과 팽창기의 용적을 동시에 고려하여 설계 팽창비를 목표 운전 압력비보다 낮도록 하여 저팽창 운전을 하도록 설계 하는 것이 유리함을 제시하였다.

• 동력기계공학회지
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• 제17권2호
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• pp.87-94
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• 2013

Applicability of organic Rankine cycle for a passenger car with 3.5 L gasoline engine to convert low grade waste heat to useful shaft power has been numerically studied. Working fluid is R134a, and the Rankine cycle is composed of boiler for recovering engine cooling water heat, super heater for recovering exhaust gas heat, scroll expander for converting waste heat to shaft power, condenser for heat emission, internal heat exchanger, and feed pump. Assuming efficiencies of 90% for the heat exchangers, 75% for the scroll expander, and 80% for the feed pump, the Rankine cycle efficiency of 5.53% was calculated at the vehicle speed of 120 km/hr. Net expander shaft output after subtracting the power required to run the pump was 3.22 kW, which was equivalent to 12.1% improvement in fuel consumption. About the same level of improvement in the fuel consumption was obtained over the vehicle speed range of 60 km/hr~120 km/hr.

• 대한기계학회논문집B
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• 제36권7호
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• pp.711-719
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• 2012

유기 랜킨 사이클(ORC)을 이용한 선박 주기관 폐열 회수 시스템의 열역학적 분석을 수행하고 적용 가능성 및 효과를 검토하였다. 이론 해석에서는 ORC 와 ORC 에 열을 전달하기 위한 열전달 루프, 냉각수 공급 펌프를 모두 고려하여 전체 효율을 예측하였다. ORC 사이클의 성능은 증발기와 응축기의 특성과 열전달 루프의 온도 조건을 달리하여 평가되었으며 그 특성을 사이클 효율과 시스템 효율 관점에서 비교하였다. 수에즈막스 유조선에 대하여 ORC 사이클은 $250^{\circ}C$ 이하의 폐열 조건에 대하여 약 10%정도의 열효율을 보였다. ORC 이용하여 엔진 폐열로부터 주기관 출력의 3~4%에 해당하는 전력을 생산할 수 있으며 수에즈막스 유조선에 적용 시, 정상 운항시 필요한 전력의 59~69%를 ORC 생산 전력으로 대체하여 운항 중 연료 소모량을 절감시킬 수 있는 것으로 나타났다.

• 한국자동차공학회논문집
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• 제20권2호
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• pp.78-84
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• 2012

The purpose of this study is to investigate the performance characteristics of new exhaust heat recovery device for the engine's fast warm-up. In this study, two different interior area designed for prototyping and on the exhaust heat recovery device to evaluate the performance compare the performance characteristics were chosen a better product. A company's product and selected prototype-2 were evaluated and compared the performance. This experiment was conducted under the same conditions. The time from starting to warm-up of engine was measured. As a result, the performance characteristics of the prototype-2 was not higher than that of the A company's product. However, in comparison with base system, prototype-2 of the exhaust heat recovery device discover that the warm-up time was shortened.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.81-91
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• 2013

A novel design process of a parallel multi-flow type air-cooled condenser of a dual-loop waste heat recovery system with Rankine steam cycles for improving the fuel efficiency of gasoline automobiles has been investigated focusing on reduction of the pressure drop inside the micro-tubes. The low temperature condenser plays a role to dissipate heat from the system by condensing the low temperature loop working fluid sufficiently. However, the refrigerant has low evaporation temperature enough to recover the waste from engine coolant of about $100^{\circ}C$ but has small saturation enthalpy so that excessive mass flow rate of the LT working fluid, e.g., over 150 g/s, causes enormously large pressure drop of the working fluid to maintain the heat dissipation performance of more than 20 kW. This paper has dealt with the scheme to design the low temperature condenser that has reduced pressure drop while ensuring the required thermal performance. The number of pass, the arrangement of the tubes of each pass, and the positions of the inlet and outlet ports on the header are most critical parameters affecting the flow uniformity through all the tubes of the condenser. For the purpose of the performance predictions and the parametric study for the LT condenser, we have developed a 1-dimensional user-friendly performance prediction program that calculates feasibly the phase change of the working fluid in the tubes. An example is presented through the proposed design process and compared with an experiment.

• 대한기계학회논문집B
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• 제22권11호
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• pp.1547-1554
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• 1998

The object of this study was to develop an economic assessment program for the optimal design of the cogeneration systems composed of combining engine, generator, waste heat recovery exchanger, absorption chiller, and boiler, etc. The energy demand categorized by electric power, heating, cooling and water supply was determined by statistical data of the existing cogeneration systems. An economic assessment was performed by comparing the total cost of cogeneration system with that of non-cogeneration system. The total cost was evaluated by adding initial investment to operational cost considering efficiency of equipment, cost of equipment, fuel and electricity. To confirm the validity of the developed program, a hotel building with an area of $127,960m^2$ was selected, and the simulated results were compared with the measured data. The difference between the simulated and the measured values for the selected hotel building was approximately 12% for annual electric consumption.