• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1446-1448
• /
• 2002

The short-time permissible temperature of an overhead distribution line conductor is determined by the softening characteristics of ACSR-OC, ACSR AW/OC 160, typical conductors employed in the overhead distribution line. Transient heat transfer equation and Newton's cooling law were applied to analyze the heating and cooling effects of the insulating conductors, respectively, and the error of co-relation was calibrated after simulating the softening test to assess the short-time characteristic of the insulating conductor. In order to verify the softening characteristic, the conductors were tested with heat cycle. The test was totally carried out 200 cycles, and 1 cycle was to heat and cool at 1.1 times permissible current of the conductor, 1.15 times for 120 minutes, respectively. After heating, the tensile strength and surface of the conductor were observed. In case of ACSR-OC, as the result of 100 hour heating test, the tensile strength of the insulator was 0.8 times the initial value. This is equivalent to the value of the conductors which are used for 10 years at sites.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2007.04a
• /
• pp.253-258
• /
• 2007

Guss asphalt used in pavement of a steel deck bridge may cause severe stress and displacement on the bridge as it is treated using very high temperatures ranging from $220^{\circ}C$ to $260^{\circ}C$. Therefore, it is critical to estimate the thermal effect of Guss asphalt on the steel deck bridge before the width and pattern of the unit portion are decided to minimize impact. In this study, introduce a new analysis method styled the Heat source of equivalent of the cable stayed bridge were conducted to verify the feasibility of numerical value analysis by comparing the results with the data measured. The thermal effects of Guss asphalt on the steel deck bridge according to temperature changes were also studied.

• Journal of Ocean Engineering and Technology
• /
• v.15 no.2
• /
• pp.79-87
• /
• 2001

In this paper, not only the development of optimizing of friction welding with more reliability and more applicability but also the development of in-process real-time weld quality (such as strength and toughness) evaluation technique by acoustic emission for friction welding of the engine exhaustive valve (SUH3-SUH35 dissimilar steels of 12.3mm, 16mm, 20mm, and 24mm in diameters) were performed, comparing with the other FRW matches of materials such as SUH3 to SUH31, STS303 and SUH3 to STS304. As an important result, the techniques for dissimilar friction welding optimization of engine heat resisting steels SUH3 and SUH35 (12.3mm, 16mm, 20mm, and 24mm) and its real-time weld quality evaluation by AE was developed, considering on both diameter and carbon equivalent effects.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.9 no.1
• /
• pp.14-18
• /
• 2010

Car muffler has the role to form the exhaust gas from high temperature- pressure to lower level and reduce the generated noise. Because of this role, its durability decrease as deformation by heat is occurred. This study is to analyze the flow of exhaust gas inside muffler and its coupled thermal deformation with 3-D modeling and ANSYS. There is the fastest flow at the exit of muffler with the maximum velocity of 54 m/s. And the maximum deformation or equivalent stress is shown at this model respectively as 0.00435 mm or 3414.4 MPa by the influence of heat and pressure at part of intersection with inlet and body of muffler.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2524-2529
• /
• 2008

The thermal system like a combustion chamber is believed to experience a significant instability problem with vibration in case that the thermal energy or the acoustic energy are transformed into a different form through a relevant path. This study deals with a numerically- predicted, Thermoacoustic instability in a Rijke tube by using a non-linear model for a heat source. The heating part where the energy transformation occurs actively is modeled after simulating two-dimensional cylinder case with constant surface temperature, and a nonlinear model that accounts for the transfer function of magnitude- and phase-characteristics is properly implemented so as to be dependent on the pulsation strength in the tube. The heat source model is observed to result in equivalent Thermoacoustic instabilities in the Rijke tube except low flow-rate cases in which the natural convection is dominant.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.19 no.4
• /
• pp.19-29
• /
• 1982

Galerkin's finite element method is applied to a two-dimensional heat convection-diffusion problem arising in the hydrodynamic lubrication of thrust bearings used in naval vessels. A parabolized thermal energy equation for the lubricant, and thermal diffusion equations for both bearing pad and the collar are treated together, with proper juncture conditions on the interface boundaries. it has been known that a numerical instability arises when the classical Galerkin's method, which is equivalent to a centered difference approximation, is applied to a parabolic-type partial differential equation. Probably the simplest remedy for this instability is to use a one-sided finite difference formula for the first derivative term in the finite difference method. However, in the present coupled heat convection-diffusion problem in which the governing equation is parabolized in a subdomain(Lubricant), uniformly stable numerical solutions for a wide range of the Peclet number are obtained in the numerical test based on Galerkin's classical finite element method. In the present numerical convergence errors in several error norms are presented in the first model problem. Additional numerical results for a more realistic bearing lubrication problem are presented for a second numerical model.

• Journal of the Korean Institute of Gas
• /
• v.2 no.4
• /
• pp.25-33
• /
• 1998

The characteristics of evaporation heat transfer for the utilization of LNG cold energy was investigated experimentally using liquified nitrogen and a solution of ethylene-glycol and water under horizontal two-phase conditions in the small-scale equipment of a cryogenic heat exchange system. The inner tubes in the double pipe heat exchanger with 8 mm and 15 mm inner diameter and 6 m length were adopted as a smooth test tubes and enhanced tubes by means of wire-coil inserts. Heat transfer coefficients and Nusselt number for the test tube were calculated from measurements of temperatures, flowrates and pressures. The correlations in a power-law relationship of the Nusselt number, the Reynolds number and Prandtl number for heat transfer were proposed which can be available for design of cryogenic heat exchangers. The correlations showed heat transfer coefficients for the wire-coil inserts were much higher than those for the smooth tubes, increased by more than 2.5 ${\~}$ 5.5 times depending upon the equivalent Reynolds number. Form and length of cryogenic double pipe heat exchanger were proposed for applicable to the utilization of LNG cold energy.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.83-88
• /
• 2004

In this study, the flow and thermal performance of the heat sink and fan-sink were experimentally studied to predict the operating condition of the fan-sink. The experiments of the flow and thermal resistance of the heat sink with various inlet blockage, which were occurred by the shapes of the axial fans, were conducted for the proof of the effects of the inlet blockages. The greater the inlet blockage of the heat sink, the higher the pressure drop and lower the thermal resistance of the heat sink will be. The operating point of the fan-sink was predicted by the pressure drop curve with the inlet blockage, which was corresponded to the selected fan and the fan performance curve, and verified by the performance test of the fan-sink. The predicted operating point of the fan-sink had good agreement with the result of the performance test of the fan-sink within $0.7\%$ of the volume flow rates. Measured thermal resistance of the fan-sink was equivalent to that of the heat sink with the same inlet blockage of the fan-sink. It was shown that the heat transfer characteristics of the heat sink were influenced by the flow interaction between the selected fan and the heat sink. To improve the thermal resistance of the heat sink, it is necessary to consider appropriate flow patterns of the fan outlet entering into the heat sink.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.2
• /
• pp.241-250
• /
• 2000

In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-22. Two internal geometries were tested ; one with smooth inner surface and the other with micro-fins. Data are presented for the followin~ range of variables ; vapor quality($0.1{\sim}0.9$), mass flux($200{\sim}600kg/m^2s$) and heat flux($5{\sim}15kW/m^2$). The micro-fin tube showed higher heat transfer coefficients compared with those of the smooth tube. The difference increased as the vapor quality increased. Surface tension force acting on the micro-fin surface at the high vapor quality is believed to be responsible. Different from the trends of the smooth tube, where the heat transfer coefficient increased as the mass flux increased, the heat transfer coefficient of the micro-fin tube was independent of the mass flux at high vapor quality, which implies that the surface tension effect on the fin overwhelms the vapor shear effect at the high vapor quality. Present data(except those at low mass flux and high quality) were well correlated by equivalent Reynolds number, Existing correlations overpredicted the present data at high mass flux.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.2
• /
• pp.95-100
• /
• 2007

An experimental study was performed to evaluate the in-plate evaporation heat transfer and flow characteristics of a evaporator used in automobile. Two test-cores with different heat transfer area, bead-shape and bead-array were tested, A type and B type. For the heat transfer, Nusselt number for B type test-core reaches a value nearly equal to the one for A type test-core, in the whole range of equivalent Reynolds number. But, for the same mass flow rate of refrigerant, hA for B type test-core becomes higher with the increase of the mass quality of refrigerant than for A type test-core. In a flow visualization experiment, the wake zone of refrigerant circulating at u-turn position of plate is observed.