• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.39-43
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• 2002

A new model for heat transfer and thermal deformation analysis according to strip mm in coiling process has been proposed. Finite difference analyses for heat transfer of cold rolled coil have been carried out under various coiling tensions and strip crown using the equivalent thermal conductivity for the radial direction of cold rolled coil which is a function of strip thickness, surface characteristics and compressive pressure. The compressive pressure is calculated from a equation expressed as a function of hoop stress and coil tension considering strip mm obtained by experiment. Finite element method for thermal deformation of cold rolled coil has been performed to investigate the effects of the strip crown, the coil tension and temperature. From these analyses, it is found that the axial inhomogeneity of thermal deformation is increased as the strip crown, compressive pressure, and temperature drop in cold coiled strip increase.

• Journal of computational fluids engineering
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• v.10 no.3 s.30
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• pp.36-42
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• 2005

The present study numerically investigates the natural convection heat transfer in a 2-D square cavity containing a centered heat conducting body. Special emphasis is given to the influences of the Rayleigh number, the dimensionless conducting body size, and the ratio of the thermal diffusivity of the body to that of the fluid on the natural convection heat transfer in overall concerned region. The analysis reveals that the fluid flow and heat transfer processes are governed by all of them. Results for isotherms, vector plots and wall Nusselt numbers are reported for Pr = 0.71 and relatively wide ranges of the other parameters. Heat transfer across the cavity, in comparison to that in the absence of a body, are enhanced (reduced) in general by a body with a thermal diffusivity ratio less (greater) than unity. It is also found that the heat transfer attains a minimum as the body size is increased with a thermal diffusivity ratio greater than unity.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.266-271
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• 2009

The present study numerically investigated the effect of the geometry of the flattened tube on the thermal performance of a high temperature generator (HTG) of a double effect LiBr-water absorption system. The heat transfer tubes of the HTG were arranged behind a metal fiber burner. The heat transfer of the tubes of HTG were consisted with a set of circular and flattened tubes in series. FLUENT, as a commercial code, was applied for estimating the thermal performance of the HTG. Key parameters were the tube arrangement in the HTG. Temperature and velocity profiles in the HTG were calculated to estimate the thermal performance of the HTG. The heat transfer rate of a HTG tube was increased, and the gas temperature around the flattened tube was decreased as the pitch ratio was increased. The heat transfer rate for the circular tube bundle with the pitch ratio of 2.48 were larger by 10% respectively than that of 2.10 and the heat transfer rate for the flattened tube bundle with the pitch ratio of 1.88 were larger by 36% respectively than that of 1.63.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.227-232
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• 2008

Stirling engine for solar thermal power is an essential part of Dish-Stirling system which generates electricity by using direct normal irradiation and will go into commercialization in near future. For the Stirling engine used in this study is Solo 161 model the capacity of which is 10 kWe and was already used for the Dish-Stirling system of KIER in Jinhae. The receiver of Stirling engine absorbes concentrated solar radiation and transfer it to working fluid of Hydrogen. The working condition of striling engine is high temperature and high pressure to make high efficiency. Therefore the receiver should stand against high temperature of above 800 $^{\circ}C$ and high pressure of max. 150 bar with good performance of heat transfer. The receiver is composed of 78 Inconel tubes of 1/8" with thickness of 0.71 mm and two reserviors which is connected with two cylinders. In order to know the charaterristics of heat transfer of Stirling engine receiver, simulation on the heat transfer of the receiver of Solo 161 is conducted by using CFD code of Fluent. The heat flux on the receiver surface has a shape of Gaussian distribution so, it is necessary to simulate a whole receiver. However, It is difficult and time consuming to simulate the whole receiver that one tube with different heat flux conditions are considered in this study. From the simulation results, heat transfer charateristics of receiver are observed and tube wall and fluid temperature and heat transfer coefficient are obtained and compared with the calculated results from Dittus-Boelter's correlation.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.103-106
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• 2002

This paper presents an effective numerical method for analyzing three-dimensional unsteady conjugate heat transfer problems of a curved pipe subjected to infernally thermal stratification. In the present numerical analyses, the thermally stratified flows in the pipe are simulated using the standard $k-{\varepsilon}$turbulent model and the unsteady conjugate heat transfer is treated numerically with a simple and convenient numerical technique. The unsteady conjugate heat transfer analysis method is implemented in a finite volume thermal-hydraulic computer code based on a non-staggered grid arrangement, SIMPLEC algorithm and higher-order bounded convection scheme. Numerical calculations have been performed far the two cases of thermally stratified pipe flows where the surging directions are opposite each other i.e. In-surge and out-surge. The results show that the present numerical analysis method is effective to solve the unsteady flow and conjugate heat transfer in a curved pipe subjected to infernally thermal stratification.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.79-84
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• 2005

The numerical solutions are examined on the effect of a centered heat conducting body on natural convection in a 2-D square cavity. The influences of the Rayleigh number, the dimensionless conducting body size, and the ratio of the thermal diffusivity of the body to that of the fluid have been investigated on the natural convection heat transfer in overall concerned region. The analysis reveals that the fluid flow and heat transfer processes are governed by all of them. Results for isotherms, vector plots and wall Nusselt numbers are reported for Pr = 0.71 and relatively wide ranges of the other parameters. Heat transfer across the cavity, in comparison to that in the absence of a body, are enhanced (reduced) in general by a body with a thermal diffusivity ratio less (greater) than unity. The heat transfer are also found to attain a minimum as the body size is increased.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2082-2087
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• 2008

The heat transfer process from steam to web through the cylinder drum consists of the thermal resistance by condensate thickness. thickness of shell, and the contact resistance between cylinder and web. The most thermal resistance in conventional cylinder drum dryer is generated by condensate, which is increased by the increase on revolution per minute(RPM). Therefore, the increase of RPM for the production enhancement results in the more thermal resistance, and eventually RPM is restricted. In this study, the theoretical analysis on the characteristics of heat transfer in cylinder drum for paper dryer was performed in the stationary state of steam in drum. The overall heat transfer coefficient, steam quantity and heat transfer quantity were predicted by diameter and length of drum, condensate thickness, revolution per minute and steam temperature for experimental apparatus design.

• Journal of Mechanical Science and Technology
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• v.19 no.5
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• pp.1206-1215
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• 2005

The thermal stratification phenomena, frequently occurring in the component of nuclear power plant system such as pressurizer surge line, steam generator inlet nozzle, safety injection system (SIS), and chemical and volume control system (CVCS), can cause through-wall cracks, thermal fatigue, unexpected piping displacement and dislocation, and pipe support damage. The phenomenon is one of the unaccounted load in the design stage. However, the load have been found to be serious as nuclear power plant operation experience accumulates. In particular, the thermal stratification by the turbulent penetration or valve leak in the SIS and SCS pipe line can lead these safety systems to failure by the thermal fatigue. Therefore in this study an 1/10 scaledowned experimental rig had been designed and installed. And a series of experimental works had been executed to measure the temperature distribution (thermal stratification) in these systems by the turbulent penetration, valve leak, and heat transfer through valve. The results provide very valuable informations such as turbulent penetration depth, the possibility of thermal stratification by the heat transfer through valve, etc. Also the results are expected to be useful to understand the thermal stratification in these systems, establish the thermal strati­fication criteria and validate the calculation results by CFD Codes such as Fluent, Phenix, CFX.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.69-76
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• 2015

This study investigates the thermal efficiency and the efficiency of heat transfer through thermal analysis when the same heat is applied to a mortar frame by firing with various configurations of mortar. As the inside diameter of the mortar increases, the additional material must be reinforced. In comparison with the extent of getting cold due to models, a mortar with the strut under the gun barrel becomes cooler than one with no strut. The thermal deformation at firing becomes different. According to the configuration of mortar and its inside diameter, the extent of getting cold becomes different. This study result can be effectively applied for improving the efficiency of the heat transfer of mortar.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.147-150
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• 2006

A new class of heat transfer fluid with higher thermal conductivity, called nanofluids has been developed by Dr. S. Choi about decade ago. Many exciting experimental and theoretical results have been reported worldwide to predict the thermal conductivity enhancement of nanofluids, however, they sometimes show excessive large discrepancies between each other. This kind of disagreements in thermal conductivity data is partly ascribable to the accuracy of the measuring apparatus, that is, mostly used THM(transient hot-wire method). New thermal conductivity measuring method whose principle is different from that of conventional THM is proposed in this article and measurements and uncertainty analysis were made for the three nanofluid samples with different particle concentration of pure, 2% and 4% of AlN nanofluids.