In the industry, globe valves, which are commonly used to precise control the flow rate along with opening and closing flow in pipes, are technically and economically limited in valve size due to ...structural instability related to complex internal flow passage. Butterfly valves, on the other hand, have advantages such as low weight and low manufacturing costs, but it is difficult to control the flow rate at an opening angle of 60°or higher and flow is unstable in the case of butterfly valve. Therefore, the purpose of this study is to have characteristics of flow rate of the globe valve that is used in the industry at the same diameter of pipeline and flow stability due to uniformity of flow through the baffle hole by adding 1/2 baffle to butterfly valve. Hole size of baffles were set at 5, 7 and 9 mm and baffles were set at the rear of the butterfly valve. To verify the method of numerical analysis, the results of experimental study were compared with the results of numerical study. As a results, it is confirmed that characteristics of flow rate of butterfly valve with baffle is similar to globe valve in the case of hole size 5 mm. In addition, flow pattern is to be stable by analyzing turbulence energy. Consequently, when applying baffle to butterfly valve, it is possible to reduce the flow unstability and change the flow rate of butterfly valve.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This study investigates the heat transfer characteristics of an insulated double pipe in accordance with the degree of vacuum and the working fluid pressure for liquefied natural gas transportation. ...A total of 16 cases were examined, and the degree of vacuum was set at 760, 0.1, 0.01 and 0.001 torr. Meanwhile, the working fluid pressure was set at 1, 3, 5 and 7 bar to analyze the effect of variables. A correlation analysis based on statistics was performed to quantitatively study the temperature distribution and the heat transfer characteristics. An approximated formula on the quantity of heat depending on the thermal conductivity of rarefied gas was also calculated. The approximated curve was compared with the theory formula. Consequently, the heat insulation property was improved in proportion to the degree of vacuum. A comparison of the approximated curve and the theory formula further showed that thermal conductivity was dominant at a high degree of vacuum.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this paper, the simplified approach using commercial computer software code was adopted to predict the performance of a kettle typed shell and tube heat exchanger. Similarly the numerical analysis ...using ANSYS/CFX is conducted for the same design and the result data are collected to analyze its performance numerically. In general, the heat exchanger performances are evaluated by predicting the temperature difference and pressure drop. The result data of both the analysis are compared to find the differences between the data. From the comparison, we came to know that the error percentage between the two analysis results is very low which is acceptable proving our design is convincible. Thereby we fabricated a prototype model of shell and tube heat exchanger (kettle type) with the same parameters used for these analyses.
Surface degreasing method with premixed flame is proposed as the removal method of adherent impurities on materials. Effects of adherent molecular thickness and surface potential energy on ...evaporation rate of adherent molecules and molecular evaporationmechanism were investigated and discussed in the present study. Evaporation processes of adherent molecules on surface molecules were simulated by the molecular dynamics method to understand thermal phenomena on evaporation processes of adherent molecules by using high temperature gas like burnt gas. The calculation system was composed of a high temperature gas region, an adherent molecular region and a surface molecular region. Both the thickness of adherent molecules and potential parameters affceted the evaporation rate of adherent molecules and evaporation mechanism in molecular scale.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Monitoring of OH chemiluminescence through an optical fiber was demonstrated to be a useful method in detecting self-excited combustion oscillations. OH chemiluminescence intensity detected by the ...optical fiber showed mostly excellent agreement with those obtained by high speed CCD camera measurements when combustion oscillations were strong. Symptoms of self-excited combustion oscillation were also studied in order to predict the onset of combustion oscillation before it proceeded to a catastrophic failure. For the purpose, we have found and proposed unique measures to tell the onset of self-excited combustion oscillations based on the careful statistics of fluctuating properties in flames, such as pressure or emission of OH radicals.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Recently, variousresearches and developments of heat exchangers with high thermal efficiencyhave been in progress to save energy. Baffles are used as design variables in a way that enhancesheat ...transfer performance of shell and tube heat exchanger. There have beenvarious of researches and developments in the relations between baffles andheat transfer performance. Existing studies on shell and tube heat exchangersare mainly about heat transfer properties of either segmental type baffles orhelical baffles. However, there is inadequateof study with comparisons between the two types ofbaffles. Thus, this paper aims to research changes in heat transfer properties according to thenumber of segmental and helical baffles. It shows pressure drop, temperaturedifference of inlet and outlet, heating surface area of inner flow region, andheat transfer coefficient in tubes.
Recently, there have been growing concerns on ships, one of the means to transport plant facilities, as studies on developing large scale plant facilities have been carried out. Particularly, carbon ...dioxide system, one of the fire safety systems, is mainly used as the fire safety facility of ships, and main valves are employed for supplying carbon dioxide. However, studies on main valves used in ships are yet to be carried out more. Especially, when carbon dioxide is sprayed as a main function of main valves at lower pressure than required, firefighting is put into difficulty. Accordingly, to solve such problem, this study observed internal pressure change using flow analysis of the main valve, then conducted fluid-structure interaction analysis based on its result, and finally investigated disk’s opening and closure and the structural safety and characteristics depending on valve’s inlet and outlet diameters.
A study of heat flux in a constant-volume combustion chamber Lee, Chi-Woo; Kim, Chi-Won; Kim, Si-Pom
Proceedings of the Institution of Mechanical Engineers. Part D, Journal of automobile engineering,
01/2003, Volume:
217, Issue:
9
Journal Article
Peer reviewed
Abstract
In the production of internal combustion engines, there has been a move towards the development of high-performance engines with fuel economy, lighter weights and smaller sizes. These trends ...help to answer problems related to thermal load and abnormal combustion, etc., in these engines. In order to clarify these problems, a thin film-type probe for instantaneous measurement of surface temperatures has been suggested. A method for manufacturing such a probe was established in this study. The instantaneous surface temperature of a constant-volume combustion chamber was measured by this probe, and heat flux was calculated and analysed with a Fourier series. For a thorough understanding of the characteristics of combustion, the authors measured the wall temperature of the combustion chamber and computed heat flux through a cylinder wall while varying the protrusion height of the probe. To achieve the above goals, an instantaneous temperature probe was developed, thereby making possible the analysis of the instantaneous temperature of the wall surface and unsteady heat flux in the constant-volume combustion chamber.
