• Smart Structures and Systems
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• v.9 no.5
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• pp.427-439
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• 2012

The present paper deals with the analytical solution of a functionally graded piezoelectric (FGP) cylinder in the magnetic field under mechanical, thermal and electrical loads. All mechanical, thermal and electrical properties except Poisson ratio can be varied continuously and gradually along the thickness direction of the cylinder based on a power function. The cylinder is assumed to be axisymmetric. Steady state heat transfer equation is solved by considering the appropriate boundary conditions. Using Maxwell electro dynamic equation and assumed magnetic field along the axis of the cylinder, Lorentz's force due to magnetic field is evaluated for non homogenous state. This force can be employed as a body force in the equilibrium equation. Equilibrium and Maxwell equations are two fundamental equations for analysis of the problem. Comprehensive solution of Maxwell equation is considered in the present paper for general states of non homogeneity. Solution of governing equations may be obtained using solution of the characteristic equation of the system. Achieved results indicate that with increasing the non homogenous index, different mechanical and electrical components present different behaviors along the thickness direction. FGP can control the distribution of the mechanical and electrical components in various structures with good precision. For intelligent properties of functionally graded piezoelectric materials, these materials can be used as an actuator, sensor or a component of piezo motor in electromechanical systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.3
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• pp.218-223
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• 2012

This study is focused on the evaluation of thermal output of TABS (Thermally Activated Building System). The aim of this study is to evaluate TABS in terms of the temperature difference between heating medium supply temperature ($T_s$) and return temperature ($T_r$), thermal output and the surface temperature distribution according to the design flow rate and the design flow temperature. Through the transient heat transfer simulation using temperature calculation using Crank-Nicolson FDM using Physibel Voltra 6.0 W, the temperature difference between $T_s$ and ��$T_r$, thermal output and the surface temperature distribution of specific TABS was calculated and evaluated. The results show that specific thermal output and temperature difference at $60^{\circ}C$ of supply water temperature were about 162 $W/m^2$, $13.6^{\circ}C$ respectively.

• Journal of Power System Engineering
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• v.16 no.5
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• pp.26-31
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• 2012

A numerical study has been carried out to investigate the heat and mass transfer of an oil pumping system with a variable shape of the housing using the CFD method. Especially, the electric motor and the pump combined together, accomplishes a research about the oil supplying system. In this study, the temperature and velocity distribution of the oil pumping system by varying the flow rate of supplying oil have been investigated. The temperature changes with each five conditions(flow rate of supply oil : 2, 4, 8, 12, and 16 liter/min) have also been studied. The numerical results show that the exhaust temperature decreases as the flow rate of the supplying oil increases. It also reveals that the temperatures change differently with the housing shape.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.1
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• pp.31-37
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• 2002

This paper is concerned with the development of a new method for making and separating ice and saving floated ice by installing an evaporation plate at in-water within a storage tank. In a conventional harvest-type ice storage system, a tank saves ice by separating a formed ice from an installed evaporation plate, which is located above an ice storage tank as an ice storage system. A new harvest-type method shows very good heat transfer efficiency than a convectional method. It is because the evaporation panel is directly contacted with water in a storage tank. Also, at a conventional system a circulating pump, a circulating water distributor and a piping are installed, but these components are not necessary in a new method. In this study two kinds of ice storage systems are experimentally investigated to study the thermal characteristics of ice storage tanks. The results showed discharge of cold capacity of new type indicated the high values about 30~40% based on five time of drive, the temperature difference of inlet/outlet occurred the big range about $1.3^{\circ}C$. So, the new type which makes ice in water showed superiorly.

• Journal of Power System Engineering
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• v.15 no.5
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• pp.37-42
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• 2011

The normal cooling system of a refrigerator is applied to indirect a cooling methods. But the Kimchi refrigerator is applied to direct the cooling method. Recently when the model was applied to both direct and indirect the cooling methods, the improvement was considerable. With the development of the living standards in Korea, there has been more sensitive dissatisfaction about the taste and the smell of Kimchi. In order to solve these kinds, there is a need to systematic and scientific approach. Based on these, the purpose of this study is to optimize design for improve the storage period of Kimchi refrigerator. In this research, we concentrate on the temperature change and heat transfer characteristics of interior parts of the Kimchi refrigerator due to control cycle of temperature and flow phenomenon of cooling air.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.830-833
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• 2004

An indoor package air-conditioner (PAC) has complex noise sources such as motor noise and fluid noise caused by the fan motor, heat transfer and shroud. Sound intensity techniques and ODS(Operational deflection shape) techniques are applied to identify the noise characteristics of an indoor air-conditioner's cabinet. The sound intensity is used to visualize the noise source locations. and the ODS to visualize the vibration pattern and to obtain the dynamic characteristics of the noise source. Acoustic intensity and operational deflection distribution are obtained in space domains as well as frequency domains. Using the visual information of source locations and its dynamic characteristics, the damping patch is applied to reduce structure borne noise in the cabinet. As a result, the noise emitted by the cabinet is reduced by 5dB.

• Journal of IKEEE
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• v.23 no.3
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• pp.793-799
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• 2019

In this study, the diffusion process and the thermal energy distribution gradient of the sensor were confirmed by using the finite element analysis program (COMSOL) of the mesh method to analyze the thermal diffusion in the wearable fabric (Nylon) + MWCNT gas sensor. To analyze the diffusion process of thermal energy, the structure of the gas sensor was modeled in a two dimension plane. The proposed modeling was presented with the characteristic value for the component of the sensor, and the gas sensor designed using the mesh finite element method (FEM) was proposed and analyzed by suggesting the one-way partial differential equation in the governing equation to know the degree of thermal energy diffusion and the thermal energy gradient. In addition, the temperature gradient 10[K/mm] of the anode-cathode electrode layer and the gas detection unit was investigated by suggesting the heat velocity transfer equation.

• Journal of Surface Science and Engineering
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• v.54 no.3
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• pp.152-157
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• 2021

The pseudocapacitor has a high energy density characteristic because it accumulates charges through a paradic redox reaction. However, due to its strong insulation properties, metal hydroxides should be designed as structural systems optimized for charge transfer to support fast electron transport. Also, Nickel material is weak to heat and is easily deformed when used as a cathode material, so stability must be secured. In this study, nickel hydroxide was produced by electrodeposition to secure the stability of nickel. Electrodeposition is a synthetic method suitable for growing optimized nickel hydroxide because it allows fine control. Nickel hydroxide (Ni(OH)₂) is a metal hydroxide used as a pseudocapacitor anode due to its high capacitance, electrical conductivity and resistance. Therefore, in order to determine how Ni(OH)₂ nanosheets are formed and what are the optimization conditions, various measurement methods were used to focus on structural growth of nanosheets produced by electrodeposition.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.1962-1971
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• 2022

The liquid lead-lithium (Pb-17Li) blanket has many applications in fusion reactors due to its good tritium breeding performance, high heat transfer efficiency and safety. The compatibility of liquid Pb-17Li alloy with the structural material of blanket under magnetic field is one of the concerns. In this study, corrosion experiments China low activation martensitic (CLAM) steel and 316L steel were carried out in a forced convection Pb-17Li loop under 1.0 T magnetic field at 480 ℃ for 1000 h. The corrosion results on 316L steel showed the characteristic with a superficial porous layer resulted from selective leaching of high-soluble alloy elements and subsequent phase transformation from austenitic matrix to ferritic phase. Then the porous layers were eroded by high-velocity jet fluid. The main corrosion mechanism of CLAM steel was selective dissolution-base corrosion attack on the microstructure boundary regions and exclusively on high residual stress areas. CLAM steel performed a better corrosion resistance than that of 316L steel. The high Ni dissolution rate and the erosion of corroded layers are the main causes for the severe corrosion of 316L steel.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.4
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• pp.184-190
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• 2022

In an attempt to apply hybrid rocket to the RATO (Rocket-Assisted Take Off) system, combustion characteristics of the non-circular grain were figured out in this study. Having larger combustion area, it was reconfirmed that the non-circular grain has advantages over regression rate, characteristic velocity and chamber pressure in which all gave higher values. Experiments were performed to understand the effect of the non-circular grain geometry over time where local regression rates depending on grain location were analyzed. It was found that the regression rate of five distinct locations were different. Partial conclusion driven was that these differences are due to the heat transfer caused by dissimilar distances from the flame layer. Besides, as combustion duration increased, the fuel port became circular, and the regression rate converged to a single value over the whole grain.