• 대한기계학회논문집
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• 제16권2호
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• pp.325-335
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• 1992

In this work, direct contact 4-stage fluidized bed heat exchanger is experimentally studied to develop a new type of heat exchanger which recovers the energy contained in the high temperature waste gas exhausted from the industrial furnaces. A sand is used as a heat transfer medium in this experiment. To determine the optimum operating condition, 11 different perforated plates which have a different free area ratio with different hole diameter are used in the experiment. From the room temperature experiment, the pressure drop which is caused by fluidized bed formation is observed. The high temperature experiment is carried out to seek the optimum operating condition of high heat efficiency at low heat exchanger operation cost. The results of experiment are as following. The pressure drop in the high temperature condition can be predicted from the results of the room temperature experiment. And Nusselt number becomes smaller due to the increased interference between sand particles as Reynolds number increases when the dilute phase fluidized beds are formed in nigh temperature condition. But heat transfer amount through the total sand surface area become larger due to the large resident amount of sand. Considering the heat transfer amount and the heat exchanger operation cost, perforated plates which have either a 30% or 35% of free area ratio with 15mm of hole diameter are best fitted for our goal of this work. The values of .phi. which is a dimensionless number representing the absorption heat amount per unit sand rate are in the range from 0.4 to 0.5, when Reynolds number of waste gas ranges from 25-30 with these perforated plates.

• 해양환경안전학회지
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• 제27권5호
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• pp.647-655
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• 2021

IMO에서는 선박으로부터 온실가스 감축을 위해 선박의 에너지효율 증진에 관한 논의를 진행하고 있다. 현재, 선박으로부터 발생되는 폐열을 이용한 ORC 발전 시스템을 적용함으로써 선박으로부터 높은 에너지 변환 효율을 기대할 수 있다. 이 기술은 물보다 더 낮은 온도 범위에서 증발하는 프레온 또는 탄화수소 계통의 유기 매체를 작동 유체로 사용한다. 이를 통해 상대적으로 낮은 저온에서 증기(기체)를 생성 및 동력을 발생시킬 수 있다. 본 연구에서는 유기 랭킨 사이클인 ORC 발전 시스템에서 냉매와 폐열 사이 열·유동해석(Analysis of Heat flow)을 3D 시뮬레이션 기법을 이용하여 구조물의 내·외부에 흐르는 유체가 온도 변화, 속도 변화, 압력 변화 및 질량 변화를 통해서 구조물에 어떤 영향을 미치는지를 분석하고자 하며, 동 연구는 이 기법을 이용하여 ORC 발전 시스템에서 냉매와 선박 주기관의 배기가스로부터 일어나는 열교환기의 열전달을 해석하였다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.191-194
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• 2011

Low-grade waste heat has generally been discarded in industry due to lack of efficient recovery methods. In recent years, organic Rankine cycle(ORC) has become a field of intense research and appears as a promising technology for conversion of heat into useful work of electricity. In this work thermodynamic performance of ORC with superheating of vapor is comparatively assessed for various working fluids. Special attention is paid to the effects of system parameters such as the evaporating temperature on the characteristics of the system such as maximum possible work extraction from the given source, volumetric flow rate per 1 kW of net work and quality of the working fluid at turbine exit as well as thermal efficiency.

• 한국유체기계학회 논문집
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• 제18권1호
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• pp.29-36
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• 2015

Recently, Stirling engines are emerging as a key device for power conversion of renewable energy or waste energy. This study develops a LTDSE(Low Temperature Differential Stirling Engine) using a water spray for higher heat transfer and performs load performance tests for various flow rates and temperatures of hot water spray for variable engine loads emulated by a mechanical friction device. Internal temperature and pressure, working frequency and inlet and outlet temperature of the supply water are measured. As a result, the increases in flow rate and temperature of hot water respectively enhance the power output, efficiency and the working frequency, while the increasing engine load leads to decreases in working frequency but increases in the pressure amplitude. Eventually, it is revealed there exists a maximum shaft power of the test engine.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
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• pp.399-402
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• 2004

An aquifer thermal energy storage (ATES) model is simulated by FEFLOW according to the scenario of heat pump operation in two layered confining aquifer. The scenario is consisted of 4 steps: 90 days pumping (west well) and waste water injection (east well: 35 $^{\circ}C$), 90 day s stop, 90days pumping (east well) and waste water injection (west well: 5 $^{\circ}C$), and 95 days stop. The injection of the waste water is limited in the second layer and the first layer is aquitard. The temperature distribution at the surface shows low difference with reference temperature and opposit aspect with that of the second layer because the thermal transition through the first layer is very slow. Even though the simulated thermal transition in the aquifer system have a difference with real ATES system, optimal design and operate system can be developed with field tests and operational experience.

• International journal of advanced smart convergence
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• 제4권1호
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• pp.127-136
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• 2015

This paper is a study of a simple distillation process. Its objective is to compare fuel production from plastic waste, its data collecting is from the factory and simple data calculated a suitable evaluation on the simple distillation plant built before calculation. The experiment with a simple distillation process is separated into three sections. The first section is a simple distillation process of distillation producing diesel using heat source by biomass. The second section is distillation process which produces fuel using heat source by burner. The third section uses heat source by burner incorporate with biomass. The experiment reveals that the result of the second section is the most efficient. In comparison with the experiments and the simple calculation, the result on the efficiency of work has error less than 5% and it is sufficient for the next experimental process. Thus, the study and design on a simple distillation process produces fuel from plastic waste has to concern mainly on design heat exchangers, flow rate and optimized temperature. Further study on this plant can be developed throughout the county due to its low cost and efficiency.

• International Journal of Advanced Culture Technology
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• 제3권2호
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• pp.58-66
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• 2015

This paper aims to compare the use of Centrifugal Turbine and Tesla Turbine in an application of Organic Rankine Cycle (ORC) Machine using Isopentane as working fluid expanding. The working fluid has boiling point below boiling water and works in low-temperature sources between $80-120^{\circ}C$ which can be produced from waste heat, solar-thermal energy and geothermal energy etc. The experiment on ORC machine reveals that the suitability of high pressure pump for working fluid has result on the efficiency of work. In addition, Thermodynamics theory on P-h diagram also presented the effect of heat sources' temperature and flow rate on any work. Thus, the study and design on ORC machine has to concern mainly on pressure pump, flow rate and optimized temperature. Result experiment and calculate ORC Machine using centrifugal Turbine efficiency better than Tesla turbine 30% but Tesla Turbine is cheaper and easily structure. Further study on the machine can be developed throughout the county due to its low cost and efficiency.

• 한국자동차공학회논문집
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• 제20권4호
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• pp.25-32
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• 2012

Cold start driving cycles exhibit an increases in friction losses due to the low temperatures of metal components and media compared to the normal operating engine conditions. These friction losses are adversely affected to fuel economy. Therefore, in recent years, various techniques for the improvement of fuel economy at cold start driving cycles have been introduced. The main techniques are the upward control of coolant temperature and the fast warm-up techniques. In particular, the fast warm-up techniques are implemented with the coolant flow-controlled water pump and the WHRS (waste heat recovery system). This paper deals with an effect of fast ATF (automatic transmission fluid) warm-up on fuel economy using a recovery system of EGR gas waste heat in a diesel engine. On a conventional diesel engine, two ATF coolers have been connected in series, i.e., an air-cooled ATF cooler is placed in front of the condenser of air conditioning system and a water-cooled one is embedded into the radiator header. However, the new system consists of only a water-cooled heat exchanger that has been changed into the integrated structure with an EGR cooler to have the engine coolant directly from the EGR cooler. The ATF cooler becomes the ATF warmer and cooler, i.e., it plays a role of an ATF warmer if the temperature of ATF is lower than that of coolant, and plays a role of an ATF cooler otherwise. Chassis dynamometer experiments demonstrated the fuel economy improvement of over 2.5% with rapid increase in the ATF temperature.

• 대한기계학회논문집B
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• 제23권9호
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• pp.1085-1097
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• 1999

A separate heat pipe system capacity of 3,700kW has been developed and applied to preheating the blast furnace gas for recovery of the waste heat from boiler. The system is designed to preheat the blast furnace gas up to $126^{\circ}C$ by using tho boiler exhaust gas of which temperature is $180^{\circ}C{\sim}220^{\circ}C$. The arrangement of the fin tubes as well as the shape of the fin has been carefully determined to minimize the fouling problems. The heat pipe system was found to be stable in circulation of the working fluid and the range of the temperature variation of the preheated blast furnace gas was within $10^{\circ}C$. It was proved through a long-term test that the selected tube arrangement and the shape of the fins are proper to prevent the fouling problems and that the pay-back period of the system Is within one year.

• 해양환경안전학회지
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• 제27권6호
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• pp.839-845
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• 2021

본 연구에서는 CO₂ 가스 배출 저감 및 선박 폐열 회수 증대를 목적으로 선박 배기로 버려지는 폐열을 전기로 변환하는 ORC(Organic Rankine Cycle) 발전에 대해 시뮬레이션을 통한 냉매별 효율을 보여주고 있다. 상대적으로 고온인 배기가스의 폐열과 상대적으로 저온인 냉각해수를 이용하여 Aspen HYSYS 11을 이용하여 시뮬레이션을 수행하였다. 해수냉각 ORC 발전시스템의 시뮬레이션 결과, 작동유체 효율은 R717 냉매가 2.86 %로 가장 높았고, 다음 순으로 R152a, R134a, R143a, R125a로 나타났다.