• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1025-1030
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• 2008

We develop 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 10 bar and tested steam pressure is 4 bar. In order to test these heat exchanger modules, we make a 0.5t/h flue tube boiler (LNG, $40\;Nm^3/h$). The test results of 100% boiler load show that heat transfer rate of 1st module is 49.7 Mcal/h which is 34% of total heat transfer rate and that of 2nd module is 82.6 Mcal/h which is 57% of total heat transfer rate. The reason of higher the heat transfer rate of 2nd module than that of 1st module is that the 2nd heat exchanger module has finned tubes instead of bare tube. The boiler load 50% results show that only 2 heat exchanger modules are needed to extract the heat from the flue gas to water. From this result, it is very important of optimum design of the first finned tube among all water tubes.

• Particle and aerosol research
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• v.15 no.3
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• pp.105-113
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• 2019

The exhaust emissions from coal-fired power plants have received much attention because coal-fired power plants are the one of the largest sources of particulate matter (PM) emissions in South Korea. To measure the PM10 and PM2.5, we developed the novel diluter which is comprised of ejector and porous tube in series. The dilution ratio must be defined to calculate particle concentrations of the sampled air as well as to probe match for the isokinetic sampling. For this reason, we verified the dilution ratio of the developed diluter by the flow rate, numerical solution, gas concentration and particle concentration. The ejector-supplied flow rates were 10-50 L/min and the porous tube-supplied flow rates were 30, 50 L/min in this study. All methods above showed similar dilution ratios to each other within 10 % error rate. The dilution ratio was confirmed by comparing mass concentrations before and after the dilution process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.740-746
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• 2017

Infrared signatures emitted from hot exhaust gases generated by the internal combustion engine and generator of naval ships and from the metal surfaces of the funnel have become the targets of infrared homing missiles, which is the main cause of a reduced survivability of naval ships. The infrared signatures from the exhaust gas and the metal surface of a funnel can be reduced by installing an infrared signature suppression (IRSS) system on a ship. The IRSS system consists of three parts: an eductor that generates turbulent flow of the exhaust gas, a mixing tube that mixes the exhaust gas with ambient air, and a diffuser that forms an air film using the pressure difference between the inside and outside air. As a basic study to develop an IRSS system using domestic technology, this study analyzed the model test conditions of an IRSS system developed by an overseas engineering company and installed on a domestic naval ship, and a numerical heat-flow analysis was conducted based on the results of the aforementioned analysis. Numerical heat-flow analysis was performed using a commercial numerical-analysis application, and various turbulence models were considered. As a result, the temperature and velocity of the exhaust gas at the educator inlet and diffuser outlet and that of the metal surface of the diffuser were measured, and found to agree well with the measurement results of the model test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.793-798
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• 2017

In modern naval ships, an infrared signature suppression (IRSS) system is used to reduce the metal surface temperature of the heated exhaust pipe and high-temperature exhaust gases generated from the propulsion system. Generally, the IRSS systems used in Korean naval ships consist of an eductor, mixing tube, and diffuser. The diffuser reduces the temperature of the metal surface by creating an air film due to a pressure difference between the internal gas and the external air. In this study, design variables were selected by analyzing the shapes of a diffuser designed by an advanced overseas engineering company. The characteristics of the design variables that affect the performance of the IRSS were investigated through the Taguchi experimental method. A heat flow analysis technique for IRSS systems established in previous studies was used analyze the performance of the diffuser. The performance evaluation was based on the area-averaged value of the metal surface temperature and exhaust gas temperature at the outlet of the diffuser, which are directly related to the intensity of the infrared signature. The results show that the temperature of the exhaust gas was significantly affected by changes in the diameter of the diffuser outlet, and the temperature of the diffuser's metal surface was significantly affected by changes in the number of diffuser rings.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.05a
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• pp.171-176
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• 2004

Heat regenerator attached in small-scale regenerative radiant tube burner was designed using the theoretical computation code and was confirmed the performance of waste heat recovery ratio. From the computation, when ceramic ball of 4-5kg was used, temperature efficiency and available waste heat recovery ratio were predicted 80% and 70%, respectively. Similar efficiencies were obtained from the experiments using LPG. However, since exhaust gas temperature entered into regenerator was below 85$0^{\circ}C$ which was much lower than that we expected, preheat air temperature was lowered below 80$0^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.676-684
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• 1990

This study is on the pulsating combustion of premixed gas in a Rijke type combustor made of a honeycomb flame holder in a tube. Modelling for the onset condition of the oscillation is made by the ratio of the acoustic power generation based on the analysis of heat transfer to the power loss due to the thermoviscous dissipation and radiation. Experiment is performed for the characteristics of acoustic, thermal and combustion. It is shown that the theoretical modelling for the oscillation may be used as a limit condition. And the combustion analysis for the acoustic power generation is needed for better prediction of the onset condition. Experimental result shows that, by pulsation, the flame length is shortened and the flame temperature is decreased with increase in the heat transfer coefficient. The NO$_{x}$ concentration in the exhaust gas is significantly reduced by pulsation and the concentration of unburned hydrocarbon shows a little increase.e.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.55-66
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• 2004

In this paper a method for finding solutions 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 mathematical analysis of the influence of entropy and vortex waves to acoustic wave. was suggested. According to the method reflection coefficients of acoustic wave on a supercritical nozzle was numerically calculated, through which it was presented that entropy or vortex waves can strengthen or weaken the reflection rate of acoustic wave.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.2
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• pp.120-125
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• 2011

As an effort to secure economically viable heat recovery units, innovative fin shapes for industrial boilers are studied for better performance. In the present study a numerical modeling for the analysis of heat exchanger performance is conducted using a commercial software, ANSYS CFX and the results are compared with the experimental data. Out of several candidate fin shapes curved wavy fin is selected for the present study. Both numerical and experimental data are directly compared for heat transfer rate and pressure drop with the assumed constant surface temperature of $60^{\circ}C$. Exhaust gas is obtained from a test apparatus which supplies variable flow rates. The numerical results show reasonable agreements with the experimental data within 10% in terms of both total heat transfer and pressure loss.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.405-413
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• 2013

The char oxidation characteristics of high ash coal were experimentally investigated at several temperatures (from 900 to $1300^{\circ}C$) for 4 types of coals (Gunvor, Glencore, Noble, and ECM) under atmospheric pressure in a drop tube furnace (DTF). The char reaction rate was calculated from the exhaust gas concentrations (CO and $CO_2$) using FT-IR, and the particle temperature was measured using the two-color method. In addition, the activation energy and pre-exponential factor for high ash coal char were calculated based on the Arrhenius equation. The results show that as the ash content increases, the particle temperature and area reactivity decreases. This is because in high ash coal, the large heat capacity of the ash, ash vaporization, and relatively low fixed carbon content of ash suppress combustibility during char oxidation. As a result, the higher ash content of coal leads to high activation energy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.7
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• pp.675-681
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• 2012

The char oxidation characteristics of ashless coal with a relatively low ash content and high heating value were experimentally investigated at several temperatures (from $900^{\circ}C$ to $1300^{\circ}C$), in various oxygen concentrations (from 10% to 30%) under atmospheric pressure in a drop tube furnace. The char reaction rate was calculated from the exhaust gas concentrations (CO, $CO_2$) measured by FT-IR, and the particle temperature was measured by the two-color method. In addition, the activation energy and pre-exponential factor of ashless coal char were also calculated based on the Arrhenius equation. The results show that higher temperature and oxygen concentration result in a higher reaction rate of ashless coal, and the activation energy of ashless coal char is similar to that of bituminous coal.