• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.46 no.4
• /
• pp.487-494
• /
• 2010

In order to test the applicability of bunker-A in a diesel engine for small-fishing boat, the investigation of the engine performance and the exhaust emission was performed under various conditions of fuel property, intake air pressure and fuel temperature. It was also performed based on IMO NOx Technical code. At high load, the energy consumption rate of bunker-A was lower than that of diesel oil, and the characteristics of exhaust emission of bunker-A were similar to those, and NOx emission rates of both fuels satisfied the IMO NOx emission regulation limits. The energy consumption rate and characteristics of exhaust emission were improved as the intake air pressure was increased, but these were not improved remarkably as the temperature of bunker-A was heated. However, at low load the energy consumption rate, CO emission rate and HC emission rate of bunker-A were higher than those of diesel oil, but NOx emission rates of the fuels were about the same. In addition, at low load the energy consumption rate and CO emission rate of bunker-A were increased as the intake air pressure and the temperature were higher than normal conditions. Accordingly, it is thought that the use of bunker-A in a kind of test engine is possible at high load. On the other hand, it is thought that more research is needed to improve the combustion efficiency under low temperature and low load condition.

• Journal of Welding and Joining
• /
• v.16 no.2
• /
• pp.111-121
• /
• 1998

It is well recognized that a excessive temperature gradient from the junction of head to skirt in axial direction in a hot pressure vessel can cause unpredicted high thermal stress at the junction and/or in axial direction of a skirt. this thermal stress resulting from axial thermal gradient may be a major cause of unsoundness of structural integrity. In case of cyclic operation of hot pressure vessels, the thermal stress becomes one of the primary design consideration because of the possibility of fracture as a result of cyclic thermal fatigue and progressively incremental plastic deformation. To perform thermal stress analysis of the junction and cylindrical skirt of a vessel, or, at least, to inspect quantitatively the magnitude and effect of thermal stress, the temperature profile of the vessel and skirt must be known. This paper demonstrated the temperature distribution and thermal stress analysis for the junction of skirt to head using F.E. analysis. Effect of air pocket in crotch space was quantitatively investigated to minimize the temperature gradient causing the thermal stress in axial direction. Effect of the skirt height on thermal stresses was also studied. Analysis results were compared with theoretical formulas to verify th applicability to the strength calculation in design field.

• Journal of Hydrogen and New Energy
• /
• v.20 no.6
• /
• pp.526-533
• /
• 2009

In this paper, cycle performance analysis of $CO_2-C_3H_8$ (R744-R290) cascade refrigeration system with internal heat exchanger is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree and gas cooling pressure and evaporating temperature in the propane (R290) low temperature cycle and the carbon dioxide (R744) high temperature cycle. The main results were summarized as follows : The COP of cascade refrigeration system of $CO_2-C_3H_8$ (R744-R290) increases with the increasing subcooling degree, but decreases with the increasing superheating degree. The COP of cascade refrigeration system increases with the increasing evaporating temperature, but decreases with the increasing gas cooling pressure. Therefore, superheating and subcooling degree, compressor efficiency, evaporating temperature and gas cooling pressure of $CO_2-C_3H_8$ (R744-R290) cascade refrigeration system have an effect on the COP of this system.

• Journal of Hydrogen and New Energy
• /
• v.23 no.5
• /
• pp.521-529
• /
• 2012

Since the energy demand for refrigeration and air-conditioning has greatly increased all over the world, thermally activated refrigeration cycle has attracted much attention. This study carries out a performance analysis of a vapor compression cycle (VCC) driven by organic Rankine cycle (ORC) utilizing low-temperature heat source in the form of sensible heat. The ORC is assumed to produce minimum net work which is required to drive the VCC without generating an excess electricity. Effects of important system parameters such as turbine inlet pressure, condensing temperature, and evaporating temperature on the system variables such as mass flow ratio, net work production, and coefficient of performance (COP) are thoroughly investigated. The effect of choice of working fluid on COP is also considered. Results show that net work production and COP increase with increasing turbine inlet pressure or decreasing condensing temperature. Out of the five kinds of organic fluids considered $C_4H_{10}$ gives a relatively high COP in the range of low turbine inlet pressure.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.8
• /
• pp.1430-1435
• /
• 2007

We developed a 440MHz surface acoustic wave (SAW) microsensor integrated with pressure-temperature sensors and ID tag. Two piezoelectric substrates were bonded, in which ${\sim}150\;{\mu}m$ cavity was structured. Four sides were completely sealed by JSR photoresist (PR). Pressure sensor was placed on the top substrate, whereas ill tag and temperature sensor were placed on the bottom substrate. Using network analyzer, the developed microsensor was wirelessly tested. Sharp reflection peaks with high S/N ratio, small signal attenuation, and small spurious peaks were observed. All the reflection peaks were well matched with the coupling of mode (COM) simulation results. With a 10mW RF power from the network analyzer, a ${\sim}1$ meter readout distance was observed. Eight sharp ON reflection peaks were observed for ID tag. Temperature sensor was characterized from $20^{\circ}C$ to $200^{\circ}C$. A large phase shift per unit temperature change was observed. The evaluated sensitivity was ${\sim}10^{\circ}/^{\circ}C$.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.6
• /
• pp.193-200
• /
• 2007

The spalling analysis of high strength concrete columns needs a very complex and difficult process accounting for peeling of cover concrete as well as thermal, thermo-stress and hygro-transfer phenomena. However, the study on the spalling analysis method is insufficient. The practical spalling analysis algorithm is developed in this study, which formulates a vapor pressure equation as the parameter of temperature and cover depth and uses the compatibility condition In results of the spalling analysis, as the concrete strength increases and the content of PP fiber decreases the degree of spalling increases. This shows a similar result as the previous experimental study. Therefore the developed algorithm suggested in this study is expected to be useful in predicting the spalling of high strength concrete columns.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.22 no.1
• /
• pp.1-7
• /
• 2013

Pneumatic cylinders are widely used to actuators in automatic equipments because they are relatively inexpensive, simple to install and maintain, offer robust design and operation, are available in a wide range of standard sizes and design alternatives. This paper presents a comparative study among the dynamic characteristics of meter-out and meter-in speed control of pneumatic cushion cylinders with a relief valve type cushion mechanism. Because of the nonlinear differential equations and a requirement for simultaneous iterative solution in a mathematical model of a double acting pneumatic cushion cylinder, a computer simulation is carried out to investigate pressure, temperature, mass flow rate in cushion chamber and displacement and velocity time histories of piston under various operating conditions. It is found that the piston velocity and pressure response in meter-in speed control are more oscillatory than with meter-out those when pneumatic cushion cylinders are driven at a high-speed. In meter-out speed control, the effective area of the flow control valve is larger than that of meter-in, and the supply pressure has to be much higher than the pressure required to move the load because it has also to overcome the back pressure in cushion chamber.

• Journal of the Korean Institute of Gas
• /
• v.2 no.4
• /
• pp.1-6
• /
• 1998

In order to increase design efficiency, it is required to design steam boiler pressure parts systematically considering daily start-stop operation and load variation. The objective of this research is to develope an integrated system for increasing design efficiency of boiler pressure parts. The developed system consists of three program modules: (1) flexibility design module for the header stub considering fatigue life, (2) fatigue limit calculation and life evaluation module for the thick-walled boiler pressure part under cyclic operation using TRD301 code, (3) drawing automation module for the header and drum producing design drawings, welding data and bill of materials.

• 유체기계공업학회:학술대회논문집
• /
• 2000.12a
• /
• pp.259-264
• /
• 2000

The functions of the plug valve are the control of flow rate as well closing and opening pipe lines. Analyses on the flow characteristics in plug valve port are required to improve the performance and safety at severe operating conditions such as high-pressure and high-temperature. In this study, numerical analyses are carried out with varying the opening rate (fraction of the full open to close) of the valve and the shapes of valve Uk: straight, convex, concave and mixed shapes. The parameters influencing the flow characteristics in the valve are the discharge coefficient( $C_v$) and the resistance coefficient( K). Therefore, the distributions of static pressure, velocity vector and stream lines are investigated, and $C_v$ and K are calculated in each opening rate and shape. In case of full open, the static pressure passed through the valve port has almost been recovered. However, in case of other opening rates, the pressure does not permanently regained due to pressure drop leading to loss. This phenomenon in each shape of the valve shows the different behaviors. Calculation results show that the mixed shape has the best flow attribute.

• Preventive Nutrition and Food Science
• /
• v.13 no.4
• /
• pp.321-326
• /
• 2008

In order to improve the market competitiveness of the processed products of Undaria pinnatifida, various extraction conditions of Undaria pinnatifida were examined to determine the optimal conditions for the extraction of its valuable components. The highest level of alginic acid content was detected after 90 min of typical extraction or after 20 min of pressure extraction, after which the levels decreased slightly. The concentrations of reducing sugar and crude protein were also high after 90 min of typical extraction. Both alginic acid and reducing sugar were extracted in greater amounts using pressure extraction. The reducing sugar content was $2.8{\sim}3.2$ times higher using pressure extraction rather than typical extraction. Furthermore, the extraction results were superior with the, pressure extraction method. The appropriate temperature and duration of extraction were found to be $120^{\circ}C$ for 20 min. The use of a single enzyme yielded better results during extraction compared to the use of a mixture of enzymes. 20 min of pressure extraction followed by the addition of 0.1% pectinase and 2 hr of further extraction at $50^{\circ}C$ yielded high contents of alginic acid and reducing sugar from Undaria pinnatifida.