• Transactions on Electrical and Electronic Materials
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• v.1 no.4
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• pp.25-29
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• 2000

In this paper, PET(Ployethylene Terephthalate) films with semiconducting and interface layers were investigated, The electrical properties, such as volume resistivity, tan$\delta$(dissipation factor) and breakdown strength at various temperatures were measured. Thermal analysis of PET and semiconducting films were measured and compared by differential scanning calorimeter(DSC) of each film. It is found that the volume resistivity of films(dependence on semiconducting interface layers)and electrical properties of PET films are changed ,Breakdown strength and dissipation factor of PET films with semiconducting layer (PET/S/PET) are decreased more greatly than PET and PET/PET films, due to the increase of charge density of charges at two contacted interfaces between PET and semiconductor, The dissipation factor of each films in increased with temperature,. For PET/S/PET film, is depended on temperature more than PET of PET/PET. However, the breakdown strength is increased up to 85$\^{C}$ and then decreased over 100$\^{C}$The electrical properties of PET films with semiconducting/interface layer are worse than without it It is due to a result of temperature dependency, which deeply affects thermal resistance property of PET film more than semiconducting/interface layers.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.3
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• pp.7-17
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• 2014

Power electronics modules are semiconductor components that are widely used in airplanes, trains, automobiles, and energy generation and conversion facilities. In particular, insulated gate bipolar transistors(IGBT) have been widely utilized in high power and fast switching applications for power management including power supplies, uninterruptible power systems, and AC/DC converters. In these days, IGBT are the predominant power semiconductors for high current applications in electrical and hybrid vehicles application. In these application environments, the physical conditions are often severe with strong electric currents, high voltage, high temperature, high humidity, and vibrations. Therefore, IGBT module packages involves a number of challenges for the design engineer in terms of reliability. Thermal and thermal-mechanical management are critical for power electronics modules. The failure mechanisms that limit the number of power cycles are caused by the coefficient of thermal expansion mismatch between the materials used in the IGBT modules. All interfaces in the module could be locations for potential failures. Therefore, a proper thermal design where the temperature does not exceed an allowable limit of the devices has been a key factor in developing IGBT modules. In this paper, we discussed the effects of various package materials on heat dissipation and thermal management, as well as recent technology of the new package materials.

• Journal of Surface Science and Engineering
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• v.53 no.4
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• pp.160-168
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• 2020

A polymer-based carbon nanomaterial composite was fabricated and characterized for the application of a thermal conductive adhesive. Low-dimensional carbon nanomaterials with excellent thermal conductivity such as carbon nanotube (CNT) and graphene were selected as a filler in the composite. Thermal, electrical and adhesive properties of the composite were investigated with respect to the morphology and content of the low-dimensional carbon nanomaterials. As a result, the composite-based adhesive fabricated by the loading of surface-treated MWCNTs of 0.4 wt% showed uniform dispersion, moderate adhesion and effective heat dissipation properties. Finally, it was confirmed through the thermal image analysis of LED module that the temperature reduction of 10℃ was achieved using the fabricated composite adhesive with MWCNT-6A. Expecially, heat dissipation performance of the optimized composite adhesive was evident at the hot spot in the module compared to other samples mixed with graphene or different MWCNT loading ratios.

• Journal of Surface Science and Engineering
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• v.56 no.1
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• pp.55-61
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• 2023

As a preliminary study to produce functional nanocomposites in a heat dissipation device, we performed the direct synthesis of carbon nanotubes (CNTs) on the surface of alumina (Al₂O₃) powders. A thermal chemical vapor deposition (TCVD) system was used to grow CNTs directly on the Al₂O₃ surface. In order to investigate the growth behavior of CNTs, we varied both furnace temperature of the TCVD ranging from 700 to 850 ℃ and concentration of the ferritin-dissolved DI solution from 0.1 to 2.0 mg/mL. From the previous results, the gas composition and duration time for CNT growth were fixed as C₂H₄ : H₂ = 30 : 500 (vol. %) and 10 min, respectively. Based on the analysis results, the optimized growth temperature and ferritin concentration were found to be 825 ℃ and 0.5 mg/mL, respectively. The obtained results could be adopted to achieve mass production of nanocomposites with heat dissipation functionality.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.12.2-12.2
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• 2005

• Journal of Hydrogen and New Energy
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• v.31 no.1
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• pp.112-121
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• 2020

In this work energy and entransy characteristics of heat exchangers are analyzed for 12 different flow arrangements of heat exchangers. The dimensionless parameters are number of entransy dissipation (Ng), number of entransy dissipation-based thermal resistance (Nr), and entransy dissipation-based effectiveness of heat-exchanger (εg). The dimensionless parameters are expressed analytically in terms of the effectiveness of heat exchanger (ε), heat capacity ratio (c), and number of transfer unit (N) for optimal performance of heat exchangers. Results showed that the dimensionless parameters based on the entransy dissipation can be useful concepts for optimal design of heat exchangers.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.91-102
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• 2015

Analytical solutions for the forced convection heat transfer of viscoelastic fluids obeying the Giesekus model are obtained in a concentric annulus under laminar flow for both thermal and hydrodynamic fully developed conditions. Boundary conditions are assumed to be (a) constant fluxes at the walls and (b) constant temperature at the walls. Temperature profiles and Nusselt numbers are derived from dimensionless energy equation. Subsequently, effects of elasticity, mobility parameter and viscous dissipation are discussed. Results show that by increasing elasticity, Nusselt number increases. However, this trend is reversed for constant wall temperature when viscous dissipation is weak. By increasing viscous dissipation, the Nusselt number decreases for the constant flux and increases for the constant wall temperature. For the wall cooling case, when the viscous dissipation exceeds a critical value, the generated heat overcomes the heat which is removed at the walls, and fluid heats up longitudinally.

• Coupled systems mechanics
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• v.11 no.3
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• pp.199-215
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• 2022

The present paper deals with the axisymmetric deformation in homogeneousisotropic thermoelastic solid with two temperatures, with and without energy dissipation using modified couple stresstheory. The effect of energy dissipation and two temperature isstudied due to the concentrated normalforce, normalforce overthe circularregion, thermal pointsource and thermalsource over the circular region. The Laplace and Hankel transform techniques have been used to find the solution to the problem. The displacement components, conductive temperature distribution, stress components and couple stress are computed in the transformed domain and further calculated in the physical domain using numerical inversion techniques. Effects of two temperature and energy dissipation on the conductive temperature,stress components and couple stress are depicted graphically.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1471-1481
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• 2014

This paper presents the new power dissipation model of individual switching device in a high-level modular multilevel converter (MMC), which can be mostly used in voltage sourced converter (VSC) based high-voltage direct current (HVDC) system and flexible AC transmission system (FACTS). Also, the voltage balancing method based on sorting algorithm is newly proposed to advance the MMC functionalities by effectively adjusting switching variations of the sub-module (SM). The proposed power dissipation model does not fully calculate the average power dissipation for numerous switching devices in an arm module. Instead, it estimates the power dissipation of every switching element based on the inherent operational principle of SM in MMC. In other words, the power dissipation is computed in every single switching event by using the polynomial curve fitting model with minimum computational efforts and high accuracy, which are required to manage the large number of SMs. After estimating the value of power dissipation, the thermal condition of every switching element is considered in the case of external disturbance. Then, the arm modeling for high-level MMC and its control scheme is implemented with the electromagnetic transient simulation program. Finally, the case study for applying to the MMC based HVDC system is carried out to select the appropriate insulated-gate bipolar transistor (IGBT) module in a steady-state, as well as to estimate the proper thermal condition of every switching element in a transient state.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.2
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• pp.275-284
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• 1997

Thermodynamic behavior of a composite system which is composed of two simple thermal subsystems with constant heat capacities is analyzed, and several thermodynamic phenomena are investigated. The changes of the states and the potential work of the composite system are shown as the interaction between the subsystems in the composite system. The potential work is defined as the possible maximum available work from the composite system, and it is a thermodynamic property of the composite system. The decrease of the potential work is the same as the available work output from the composite system in reversible processes. The dissipation of available work is directly connected to the generation of entropy. The concepts of exergy and internal energy can be explained as a special case of the potential work.