Hyun Dong Kim

Development of Small-scale Organic Rankine Cycle System and Study on its Operating Characteristics

KeyWords: Organic Rankine Cycle(유기랭킨사이클), Scroll Expander(스크롤팽창기), Thermal Efficiency(열효율), Isentropic Efficiency(등엔트로피효율)초록: 본연구에서는소형저온유기랭킨사이클시스템의작동특성을파악하기위하여R-245fa를작동유체로사용한소형ORC 발전시스템을설계및제작하였고, 다양한저온의열원온도에대한실험적연구를수행하였다. 저온열원을모사하기위하여최고150 °C의물을공급할수있는110 kW급의전기저항히터를제작하였으며, 컨트롤러를통해서다양한열원온도및유량조건에대한실험이가능하도록구성하였다. 또한, 상용공기용스크롤압축기를이용하여팽창기로개조하고동력계및동기식모터와직접연결하였다. 로드뱅크및PI 제어방식을사용하여팽창기의회전속도에따른동일열원온도조건에대한실험을각각수행하였으며, 소형ORC 시스템의성능에영향을미치는다양한인자들에 대하여분석하고논의하였다.Abstract: Experiments were conducted to determine the operating characteristics of a small-scale ORC (organicRankine cycle) system for various low-temperature heat sources. A small-scale ORC power generation systemadopting R-245fa as a working fluid was designed and manufactured. Hot water was used as the heat source,and the temperature was controlled using 110-kW electric resistance heaters that provided temperatures of upto 150 °C. An open-drive oil-free scroll expander directly connected to a synchronous generator was installedin the ORC unit. Experiments were conducted by varying the rotational speed of the expander under thesame heat source temperature conditions. The factors that influence the performance of the small-scale ORCsystem were analyzed and discussed.

Visualization study on the transient liquid film behavior and inner gas flow after rupture of a soap bubble

This study examined the transient behavior of liquid films and the flow of inner gas. Olive oil particles were inserted into a soap bubble through a Laskin nozzle for visualization, and the inner gas flow fields were measured by time-resolved particle image velocimetry. A pulse laser was used for contactless rupturing of the soap bubble. The transient behavior of the liquid film after the soap bubble ruptured was captured using a high-speed camera at 3,600 frames per second. After rupturing the soap bubble, the inner gas flowed out to the outside through the crack. This is called the primary flow. The removal velocity of the upper liquid film was faster than that of the bottom liquid film. The Kelvin–Helmholtz vortex was generated at the upper and bottom boundaries of the liquid film. A series of Kelvin–Helmholtz vortices, which arise in shear flow along a contact discontinuity, were formed around the bubble sphere. Secondary flow was generated due to a change in momentum after impinging the soap film to a point, and was faster than primary flow.Graphical Abstract

Development and Characterization of Small-Scale ORC System Using Scroll Expander

In order to determine the operating characteristics of a small-scale ORC (organic Rankine cycle) system for various low temperature heat sources, experiments were carried out. A small-scale ORC power generation system adopting R-245fa as a working fluid was designed and manufactured. Hot water was used for the heat source and the temperature was controlled by the 110 kW electric resistance heaters which provided up to 150 °C. Cooling temperature was controlled by a circulating water chiller to simulate various heat sink environments. An open-drive oil-free scroll expander directly connected to a high-speed synchronous generator was installed in the ORC unit. The efficiencies of the cycle and the expander, electric power of the developed ORC system with respect to the operating conditions were investigated by experiments. The factors which influence the performance of the oil-free scroll expander were analyzed and discussed.

Dynamic analysis of bubble-driven liquid flows using time-resolved particle image velocimetry and proper orthogonal decomposition techniques

AbstractAn experimental study to evaluate dynamic structures of flow motion and turbulence characteristics in bubble-driven water flow in a rectangular tank with a varying flow rate of compressed air is conducted. Liquid flow fields are measured by time-resolved particle image velocimetry (PIV) with fluorescent tracer particles to eliminate diffused reflections, and by an image intensifier to acquire enhanced clean particle images. By proper orthogonal decomposition (POD) analysis, the energy distributions of spatial and temporal modes are acquired. Time-averaged velocity and turbulent kinetic energy distributions are varied with the air flow rates. With increasing Reynolds number, bubble-induced turbulent motion becomes dominant rather than the recirculating flow near the side wall. Detailed spatial structures and the unsteady behavior of dominant dynamic modes associated with turbulent kinetic energy distributions are addressed.Graphical AbstractGraphical Abstract text

Design and Thermodynamic Analysis of Hybrid Tri-generation Gas Engine-Organic Rankine Cycle

Abstract >> In a gas engine, the exhaust and the engine cooling water are generated. The engine cooling water temperature is 100 ℃ and the exhaust temperature is 500 ℃. The amount of heat of engine cooling water is43 kW and the amount of heat of exhaust is 21 kW. Eight different hybrid organic Rankine cycle (ORC) systemconfigurations which considering different amount and temperature of waste heat are proposed for two gas enginetri-generation system and are thermodynamically analyzed. Simple system which concentrating two different wasteheat on relatively low temperature engine cooling water shows highest thermal efficiency of 7.84% with pressureratio of 3.67 and shaft power of 5.17 kW. Key words : Gas engine(가스 엔진), Engine exhaust(엔진 배기), Organic Rankine cycle(유기랭킨사이클), Hybridsystem(하이브리드 시스템), Thermodynamic analysis(열역학적 분석) † Corresponding author : kckim@pusan.ac.kr Received : 2015.01.02 in revised form 2015.01.24 Accepted: 2015.02.28Copyright ⓒ 2015 KHNES Nomenclature h : enthalpy (kJ/kg)η : efficiency

Quantitative Visualization of Dissolved Oxygen Concentration Field in Micro Flows using PtOEP/PS Membrane

It is highly needed to measure the dissolved oxygen (DO) concentration field in water for a variety of purposes such as biological, industrial, environmental monitoring and medical application. Application of PSP (Pressure Sensitive Paint) which is sensitive to oxygen concentration has been carried out to measure DO concentration field using PtOEP/PS film and intensity based method under the UV-LEDs illumination. A micro round water jet having 100% of DO was obliquely impinged on to a PtOEP/PS film coated plate placed in a 0% of DO water container. DO concentration fields on the impinging plate were quantitatively visualized with a of spatial resolution. Through pixel-by-pixel calibration, uncertainty of each pixel by different sensitivity, different dye concentration and non-uniformity of illumination was removed. It is demonstrated that the high DO concentration region was coincided with the impingement area. The DO concentration gradient due to DO diffusion was affected by Reynolds number.

Characteristics of Bubble-driven Flow by Using Time-resolved PIV and POD Technique

In this paper, the recirculation flow motion and mixing characteristics driven by air bubble stream in a rectangular water tank is studied. The time-resolved PIV technique is adopted for the quantitative visu- alization and analysis. 488 nm Ar-ion CW laser is used for illumination and orange fluorescent (λex=540 nm, λem=560 nm) particle images are acquired by a PCO 10bit high-speed CCD camera (1280×1024). To obtain clean particle images, 545 nm long pass optical filter and an image intensifier are employed and the flow rates of compressed air is 3 l/min at 0.5 MPa. The recirculation and mixing flow field is further investigated by time-resolved POD analysis technique. It is observed that the large scale recirculation resulting from the interaction between rising bubble stream and side wall is the most dominant flow structure and there are small scale vortex structures moving along with large scale recirculation flow. It is also verified that the sum of 20 modes of velocity field has about 67.4% of total turbulent energy.

Flow Characteristics around Archimedes Wind Turbine according to the Change of Angle of Attack

Abstract. This paper describes aerodynamic characteristics of an Archimedes spiral wind turbine with variousangles of attack. The range of angles was controlled from - 30 o (clockwise) to + 30 (clockwise). The rotatingspeed of wind turbine at the same angle of attack in both directions was different. The reason why the-maximum rotational speed was observed at 15 o in clockwise direction can be explained based on angularmomentum conservation. Quantitative flow visualization around Archimedes wind turbine blade was carriedout between -15 o (clockwise) and +15 (counter clockwise) using high resolution PIV method. The relation-ship between drag force and rotating speeds was discussed. From these results, optimum design on yawingsystem of Archimedes spiral wind turbine may provide high efficiency on small wind power system.Key Words:Spiral Wind Power Generation(스파이럴형풍력발전), Archimedes Spiral(아르키메데스나선 ),Aerodynamics Characteristics(공력특성), PIV measurement(PIV측정), Angle of Attack(받음각) 기호설명 θ: Angle of Attack [

Quantitative Visualization of Oxygen Transfer in Micro-channel using Micro-LIF Technique

In the present study, oxygen transfer process across gas-liquid interface in a Y-shape micro- channel is quantitatively visualized using the micro laser induced fluorescence (µ-LIF) technique. Dif- fusion coefficient of Oxygen (DL) is estimated based on the experimental results and compared to its the- oretical value. Tris ruthenium (II) chloride hexahydrate was used as the oxygen quenchable fluorescent dye. A light-emitting diode (LED) with wavelength of 450 nm was used as the light source and phos- phorescence images of fluorescent dye were captured by a CMOS high speed camera installed on the microscope system. Water having dissolved oxygen (DO) value of 0% and pure oxygen gas were injected into the Y-shaped microchannel by using a double loading syringe pump. In-situ pixel-by-pixel calibration was carried out to obtain Stern-Volmer plots over whole flow field. Instantaneous DO concentration fields were successfully mapped according to Stern-Volmer plots and DL was calculated as 2.0675×10 -9 m 2 /s.

Numerical Simulation and Experimental Study on an Ejector System for VOC Recovery

Abstract. This paper is a basic study on volatile organic compounds(VOC) recovery system in a crudeoil carrier. VOC is easily evaporated in cargo tankers during loading and transportation of crude oil,causes serious environmental contamination and a huge economic loss. An ejector system is designed tomix VOC gas into crude oil flow to reduce VOC concentration. Detail two-phase flow inside the ejectoris simulated using a commercial CFD code. To verify the numerical prediction, a scale-down experimentis conducted. Instead of crude oil and VOC, water and air are used as the working fluids. Flow char-acteristics and main parameters are obtained by two-phase flow visualization and PIV measurements. Airvolume flow rate induced by the ejector is compared with respect to the volume flow rate of water usingexperimental and numerical results. Overall performance of the two-phase ejector predicted by the CFDsimulation agrees well with that of the experiment. Key Words:Two Phase Flow (이상유동), Ejector (이젝터), Flow Visualization (유동가시화), NumericalSimulation (수치해석)