• Journal of the Korean Society for Heat Treatment
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• v.18 no.4
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• pp.223-228
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• 2005

Tube hydroforming provides a number of advantages over conventional stamping process, including fewer secondary operation, weight reduction, assembly simplification, adaptability to forming of complex structural components and improved structural strength and stiffness. It can produce wide range of products such as subframe, engine cradle, and exhaust manifold. In this study, the effect of the heat treatment conditions such as post seam annealing (PSA) and bright annealing (BA) on the ovality and hydro-formability of steel tubes has been investigated. Hydroformabilities have been estimated by the bulging heights obtained at various processing parameters such as internal pressure, axial feeding and heat treatment conditions. The ovality and forming height are strongly influenced by material properties after heat treatments.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.27-35
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• 2004

In this paper a method for finding solution of acoustic, vortex and entropy wave-equations in a cylindrical tube with variable section area was suggested under the consideration of that the high frequency instability in a rocket engine combustion chamber is an acoustic phenomena, which is coupled with combustion reaction, and that a combustion chamber and exhaust nozzle are usually shaped cylindrically. As a consequence of that some method, which enable the quantitative analysis of the influence of entropy and vortex waves to acoustic wave, was suggested.

• Journal of Energy Engineering
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• v.14 no.2 s.42
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• pp.73-81
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• 2005

An Experimental study was conducted to investigate the effective way for fuel consumption improvement in radiant tube burner heating system used in steel manufacturing process. To find effectiveness of increase of temperature and oxygen fraction of intake air on fuel consumption, the model radiant tube burner heating system with recuperator was designed to be able to adjust temperature and oxygen fraction of intake air, and was operated under various conditions with oxygen concentration in exhaust gas changed. The results show that burner chamber temperature was increased about $10\%$ of intake air temperature increase. so it was difficult to expect fuel consumption improvement. But only 1 or $2\%$ increase of oxygen fraction in intake air made a significant improvement in fuel consumption even though it made much NOx emissions also. Therefore, if NOx emissions is controlled under regulation with burner modification, it is expected that increase of oxygen fraction in Intake air is effective way to improve fuel consumption.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1068-1071
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• 2017

The turbine exhaust system consists of a turbine flange, heat exchanger, exhaust duct and thrust nozzle. Heat exchanger is used for the launch vehicle because of the advantage of reducing the weight of the helium gas and the storage tank by using the heat exchanger pressurization method compared to the cold gas pressurizing method. Since the gas generator is combusted in fuel-rich condition, the soot is contained in the combustion gas. Hence, the heat exchanger should be designed considering the reduction of the heat exchange efficiency due to the soot effect. In addition, the uncertainty of the heat exchange calculation and the evaluation of the influence of the combustion gas soot on the heat exchange can not be completely calculated, so the design requirements must include a structure that can guarantee and control the temperature of the heat exchanger outlet. In this paper, it is described that the component allocation, the design method considering the manufacture of internal structure, the advantages of new concept of nozzle design.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1319-1321
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• 2001

The purpose of this study is to manufacture and test a thermoelectric generator which converts unused energy from close-at-hand sources, such as garbage incineration heat and industrial exhaust, to electricity. A manufacturing process and the properties of a thermoelectric generator are discussed before simulation the thermal stress and thermal properties of a thermoelectric module located between an aluminum tube and alumina plate. We can design the thermoelectric modules having the good properties of thermoelectric generation. Resistivity of thermoelectric module for thermoelectric generation consisting of 62 cells was $0.15{\sim}0.4{\Omega}$. The maximum power of thermoelectric generator using thermoelectric generation modules can be defined as temperature function, and in this case. It can be analogized the lineal relation between current and voltage characteristics as function of temperature. The thermoelectric generator using 32 thermoelectric modules was assembled with 32 directly connected modules that they constrained for two kinds of heat transfer tube with key joints.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3053-3058
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• 2008

We develop a heat exchanger modules for a multi-burner boiler. The heat exchanger module is kind of a heat recovery steam generator (HRSG). This heat recovery system has 4 heat exchanger modules. The 1st module consists of 27 bare tubes due to high temperature exhaust gas and the others consist of 27 finned tubes. The maximum steam pressure of each module is 1 MPa and tested steam pressure is 0.7 MPa. In order to test these heat exchanger modules, we make a 0.5t/h flue tube boiler (LNG, $40\;Nm^3/h$). We tested the heat exchanger module with changing the position of each heat exchanger module. We measured the inlet and outlet temperature of each heat exchanger module and calculated the heat exchange rate. The results show that if module C is placed at second stage (the 1st stage is always module O, bare tube module), there is no need to attach an additional heat exchanger module. In this case the exit temperature of module C is low enough to enter an economizer which is more effective in heat recovery than a heat exchanger module.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.10
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• pp.769-775
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• 2008

In this study, the investigations on the dimpled type Exhaust Gas Recirculation (EGR) cooler have been focused on the high heat exchanger efficiency. To overcome low heat exchanger efficiency of general EGR cooler, the dimpled type EGR cooler was developed. It was ensured the improvement of the performance of the dimpled type EGR cooler related to the heat exchange based on a series of the experiment. These results were caused by the increase of thermal surface area in accordance with the dimple's one. The estimation model of the heat exchanger efficiency using the Effectiveness-NTU method was also developed in order to verify the validity of experimental result. Also, the program for the estimation of the heat exchanger efficiency on the EGR cooler with regard to the dimpled tube shape was developed. Resultantly, it was confirmed that the dimpled type EGR cooler could be served better performance than the conventional one in view of the heat exchanger efficiency.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.211-216
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• 2015

Heat exchanger tube array in a heat recovery steam generator is exposed to the hot exhaust gas flow and it could cause the flow induced vibration, which could damage the heat exchanger tube array. It is needed for the structural safe operation of the heat exchanger to establish the characteristics of flow induced vibration in the tube array. The researches for the flow induced vibration of typical heat exchangers have been conducted by using single cicular tube or circular tube array and the nondimensional PSD(Power Spectral Density) function with the Strouhal number, fD/U, had been derived by experimental method. From the present study, the basis for the application of flow induced vibration to the heat recovery steam generator tube array would be prepared. For the previous mentioned purpose, the present CFD analysis introduced a single fin tube and calculated with the unsteady laminar flow over the single fin tube. The characteristics of vortex shedding and lift fluctuation over the fin tube was investigated. The derived nondimensional PSD was compared with the results of the previous experimental researches and the characteristics of lift PSD over a single fin tube was established from the present CFD study.

• Journal of the Korean Society of Combustion
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• v.21 no.4
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• pp.30-38
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• 2016

Flame structure of co-firing coal and palm kernel shell (PKS) was investigated in a pulverized coal swirl burner by particle image velocimetry (PIV). The pulverized coal swirl flame is operated with a PKS blending ratio of 10%, 20%, and 30%. For all operating conditions, flame structures such as internal recirculation zone (IRZ), outer recirculation zone (ORZ), and exhaust tube vortex (ETV) were observed. In the center of flame, the strong velocity gradient is occurred at the stagnation point where the volatile gas combustion actively takes place and the acceleration is increased with higher PKS blending ratio. OH radical shows the burned gas region at the stagnation point and shear layer between IRZ and ORZ. In addition, OH radical intensity increases for a co-firing condition because of high volatile matter from PKS. Because the volatile gas combustion takes place at lower temperature, co-firing condition (more than 20%) leads to oxygen deficiency and reduces the combustibility of coal particle near the burner. Therefore, increasing PKS blending ratio leads to higher OH radical intensity and lower temperature.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.20-25
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• 2012

As a kind of distributed energy system, the co-generation system based Diesel engine using after-treatment device was devised for its environmental friendly and economic qualities. It is utilized in that the electric power is produced by the generator connected to the Diesel engine, and waste heat is recovered from both the exhaust gases and the engine itself by the finned tube and shell & tube heat exchangers. An after-treatment device composed ceramic heater and DOC(Diesel Oxidation Catalyst) is installed at the engine outlet in order to completely reignite the unburned fuel from the Diesel engine. In this study, mutual relation of each experimental condition was derived through minimum number of experiment using Taguchi Design and ANOVA recently used in the various fields. It is found that the total efficiency (thermal efficiency plus electric power generation efficiency) of this system reaches maximum 94.4% which is approximately higher than that of the typical diesel engine exhaust heat recovery system.