• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.1
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• pp.28-34
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• 1999

According to the development of tool material and the improvement of machinability of cutting material like aluminium alloy, the higher spindle speed is needed. However, the higher speed causes the heat generation of bearings, the deformation of spindle unit parts, and the rotational accuracy of spindle to be worse. Therefore, it is essential to analyze and control the heat generation and the thermal behavior of spindle unit in order to have higher speed and better rotational accuracy. This paper shows the analogy between the analyzation of heat generation and thermal behavior of high speed spindle system by finite element method and the test results of actual temperature rise through running test, and shows the necessity of cooling the spindle and inner ring side of bearings for the thermal balance of high speed spindle system.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.76-81
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• 2012

In recent, there are tremendous efforts to apply co-generation concept in automobile to improve its thermal efficiency. The co-generation is basically a simple Rankine Cycle that uses the waste heat from the engine exhaust and coolant for heat source. In spite of developed nano technology and advance material science, the bulky co-generation system is still a big concern in automotive application. Therefore, the system should be effectively designed not to add much weight on the vehicle, but the capacity of the waste heat recovery should be still large. With such a goal in mind, the system thermal efficiency was investigated in terms of the system operation condition and working fluid. This paper provides a direction for the optimal design of the automotive co-generation system.

• Nuclear Engineering and Technology
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• v.50 no.3
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• pp.389-395
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• 2018

The present work aims to report the consequences of Darcy-Forchheimer medium in flow of Cross fluid model toward a stretched surface. Flow in porous space is categorized by Darcy-Forchheimer medium. Further heat transfer characteristics are examined via thermal radiation and heat generation/absorption. Transformation procedure is used. The arising system of nonlinear ordinary differential equations is solved numerically by means of shooting method. The effects of different flow variables on velocity, temperature, concentration, skin friction, and heat transfer rate are discussed. The obtained outcomes show that velocity was enhanced with the increase in the Weissenberg number but decays with increase in the porosity parameter and Hartman number. Temperature field is boosted by thermal radiation and heat generation; however, it decays with the increase in the Prandtl number.

• Journal of the Korea Institute of Building Construction
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• v.9 no.3
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• pp.103-107
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• 2009

It is necessary to develop a new technology for effectively controlling thermal crack caused hydration heat according to the increasing construction of large size massive concrete structures such as mat foundation of high-rise building. Therefore, to develop a new technology for reducing hydration heat of large size massive concrete in this study, it was investigated hydration heat generation properties of binder using latent heat materials. As a test result, it was confirmed that latent heat materials were advanced on the reduction of hydration heat and control of thermal crack. It is expected to be applied as the excellent technology on the management of hydration heat and thermal crack in large size massive concrete structures.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.7
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• pp.833-841
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• 2007

The aim of this paper is to analyze the conjugate problems of heat conduction in solid walls coupled with laminar free convection flow adjacent to a vertical flat plate under boundary layer approximation. Using the similarity transformations the governing boundary layer equations for momentum and energy are reduced to a system of partial differential equations and then solved numerically using Finite Difference Method(FDM) known as the Keller-box scheme. Computed solutions to the governing equations are obtained for a wide range of non-dimensional parameters that are present in this problem, namely the coupling parameter P. the Prandtl number Pr and the heat generation parameter Q. The variations of the local heat transfer rate as well as the interface temperature and the friction along the plate and typical velocity and temperature profiles in the boundary layer are shown graphically. Numerical solutions have been consider for the Prandtl number Pr=0.70

• Journal of the Korean Home Economics Association
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• v.24 no.3
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• pp.59-67
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• 1986

The heat of sewing needle is generated through the friction during the needle penetration into and withdrawal from fabrics. Therefore, effects of sewing condition for knitted fabric on the heat generation of needle was examined. The needle size was not the large influence factor of heat generation of needle but the needle point shape significantly affects needle temperature. And the super needle coated with fluoro resin had more effect on reducing the heat of needle. The decrease of sewing speed and the increase of stitch rate had more effect on the reduction in needle temperature. Also the Influence of a sewing thread on the needle temperature was very large compared with bare needle. As expected, an increase in the number of fabric layers result in higher needle temperature.

• Journal of the Korean Society of Combustion
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• v.18 no.3
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• pp.1-8
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• 2013

Thermodynamic and economic analyses of various types of gas turbine combined cycle power plants have been performed to establish criteria for optimization of power plants. The concept of efficiency, in terms of the difference in energy levels of electricity and heat, was introduced. The efficiency of power and heat generation by power plants with other purposes was estimated, and power generation costs were figured out for various types of combined heat and power plants(i.e., fired and unfired, condensing and non-condensing modes, single or double pressure HRSG).

• Journal of the Korean Society for Precision Engineering
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• v.28 no.6
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• pp.724-731
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• 2011

Dew generation on an outer surface is considered as an important issue to be settled in the field of home appliances. In the case of a refrigerator that is subject to the dew generation problem on the surface of an outer-door of refrigeration thread, and so as to solve this problem, the electric heater is generally used for drying the dew. However, the heater inevitably requires electrical power consumption that is one of critical issues on the refrigerator. In this study, to prevent dew generation without the heater, a method of using induced heat from room temperature was proposed. In edge sides of a door, high conductive plates are installed and received the heat from outside that is relatively high temperature, and the heat is transferred onto dew generation region. Using prototypes, performance test was conducted under a certain temperature and humidity condition. The experimental results show that the surface temperature on the dew generation region was increased about $0.3{\sim}2.5^{\circ}C$ without use of any heater.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.321-322
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• 2015

Thermoelectric power generation has emerged as a promising alternative technology because it offers a potential application in the direct conversion of waste heat into electric energy. The performance of thermoelectric power generator depends on thermoelectric materials and thermoelectric power module designs. The main objective of this study is to design a 100W thermoelectric generation (TEG) module and to get optimal operating conditions of the module. The design and performance of the TEG module will be presented.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.7
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• pp.642-648
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• 2000

Falling film heat transfer analyses with aqueous lithium bromide solution were peformed to investigate the transfer characteristics of the copper tubes. Finned(knurled) tube and a smooth tube were selected as test specimens. Averaged generation fluxes of water and the heat transfer performances(heat flux, heat transfer coefficient) were obtained. The results of this work were compared with the data reported previously. As the film flow rate of the solution increased, the generation fluxes of water decreased for both tubes. The reason is estimated by the fact that the heat transfer resistance with the film thickness increased as the film flow rate increased. The effect of the enlarged surface area at the knurled tube was supposed to be dominant at a small flow rate. The generation fluxes of water increased with the increasing degree of tube wall superheat. Nucleate boiling is supposed to occur at a wall superheat of 20 K for a smooth tube, and at 10 K for a knurled tube. The heat transfer performance of the falling film was superior to pool boiling at a low wall superheat below 10 K for both tubes tested. The knurled tube geometry showed good performance than the smooth tube, and the increased performance was mainly came from the effect of the increased heating surface area.