• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.19 no.4
• /
• pp.299-306
• /
• 2007

Recently, the numerical analysis using person shape model for CFD (Computational Fluid Dynamic) has been researched widely for the thermal comfort and inhaled air quality of human body in the indoor environments. The purpose of this research is to examine the characteristic of airflow and thermal environment around human body by the experiment of displacement ventilation that assumes the indoor environment of natural convection. In this study, thermal manikin was used instead of real human body. The Airflow characteristic around human body was measured in precision by PIV (Particle Image Velocimetry). This experimental result will be used as data for CFD benchmark test using person shape model.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.79.1-84
• /
• 1995

The thermal analysis method containing micro drilling characteristic is proposed for the first time. There are such problems in thermal analysis of micro hole drilling as the thermal modeling complexity of drilling process and the undesirable micro drilling characteristic. Especially, the undesirable micro drilling characteristic prevents our using conventional thermal modeling. To model the thermal behavior of the micro drilling process, the finite different method, where heat source vectors are distributed by the measured rhrust and torque, is proposed. This method agrees with thermal behavior of the real system. And, it enable to predict the temperature field near the drill during. The validity of this method is verified in comparing with experimental results.

• Journal of the Korea Safety Management & Science
• /
• v.4 no.4
• /
• pp.137-146
• /
• 2002

In order to investigate the effect of irradiation by $^{60}Co-\gamma$rays as well as the e thermal treatment on the dielectric deterioration in ethylene propylene rubber, insulating material for electric cables used in atomic power plants, charging discharging current, residual built- up voltage and dielectric properties are measu discussed in this study. Variance in the characteristic of relative dielectric constant as a function of tem was observed in relatively high dose of irradiation. Since glass transition tem appeared at tens of degree Celsius below zero, the characteristic is attributed orientation polarization. Dielectric loss is generally increased, with increasing d irradiation in the characteristic of dielectric loss as a function of temperature, No d loss by thermal treatment was observed. Dielectric resistance decreases with increa of irradiation in the characteristic of charging current as a function of temperature be considered that dielectric resistance seems to be recovered by thermal treatm characteristic of discharging current as a function of time in the specimen less ir become similar to that of the unirradiated, when thermal treated. A peak is shown residual built- up voltage as a function of time, and the corresponding time of the shorten as increasing dose of irradiation. It is also observed that the corresponding the peak is lengthened by thermal treatment.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.11-15
• /
• 2002

This paper presents the thermal characteristic analysis of a high-speed HMC with spindle speed of 50,000rpm. The spindle is supported by two radial and axial magnetic bearings. and the built-in motor is located between the axial and rear radial magnetic bearings. The X-axis and Y-axis feeding systems are composed of linear motor and linear motion guides, and the Z-axis feeding system is composed of servo-motor, ballscrew and linear motion guide. The thermal analysis model of high-speed HMC is constructed by the finite element method, and the thermal characteristics in the design stage are estimated based on the temperature distribution and thermal deformation under the conditions related to the heat generation of built-in motor, magnetic bearings, linear motors, servo-motor, ballscrew, and so on.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.4
• /
• pp.439-442
• /
• 2004

In this study, we investigated about electrooptics characteristic of three kinds of TN cell on the polyimide surface. Monodomain alignments of thermal stressed TN cell over temperature of liquid crystal isotropic phase were almost the same as that of no thermal stressed TN cells. However, the thermal stressed TN cells have many defects. Also, threshold voltage and response time of thermal stressed TN cells show the same performances as no thermal stressed TN cells. There were little changes of value in these TN cells. However, transmittances of TN cells on the polyimide surface decrease with increasing thermal stress time. Finally, the residual DC voltage of the thermal stressed TN cell on the polyimide surface shows decrease of characteristics as increasing thermal stress time. Therefore, the thermal stability of TN cell was decreased by high thermal stress for the long times.

• Journal of IKEEE
• /
• v.16 no.3
• /
• pp.177-181
• /
• 2012

This paper introduces a thermal compensation circuit with improved compensation characteristic for amplifiers to provide stable output power regardless environmental temperature. The proposed thermal compensation circuit is composed of two branchline couplers having two diodes between them. And, the thermistor whose resistance varies significantly with temperature inversely and a operational amplifiers, so called as OP-amp, control the diodes in the compensations circuit to realize more effective thermal compendation characteristic compared with conventional circuit.

• Journal of the Korean housing association
• /
• v.12 no.1
• /
• pp.85-92
• /
• 2001

The purpose of this study is to investigate the characteristic of the thermal environment at a living room by the heating system(floor radiation heating, forced convection heating, combined heating, radiation convection heating), and to compares the change of the thermal environment after operating the heating with after the operation stopped based on the floor radiation heating. This study proposes the basic data for the design and the development of the thermal storage structure heating system which not only utilizes fully the characteristic of the comfortable thermal environment but also reduces the preheating period and be able to use the off-peak electricity.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.447-448
• /
• 2006

High speed machining is the core technology that influences the performance of machine tools, and the high speed motor spindle is widely used fur the high speed machine tools recently. The important problem in this spindle is to reduce and minimize the thermal effect by motor and bearing. In this study, the analysis of thermal characteristic of spindle is performed according to the cooling methods of housing by using finite element method. This result can be applied to the design and manufacture of the high speed spindle.

• Nuclear Engineering and Technology
• /
• v.55 no.8
• /
• pp.2757-2772
• /
• 2023

The fluid retention effect of the Volume Control Tank (VCT) leads to a long time delay in Reactor Coolant System (RCS) concentration during the boration process. A coupled model combining a lumped-parameter sub-model and a computational fluid dynamics sub-model is currently used to investigate the concentration dynamic characteristic of RCS during the boration process. This model is validated by comparison with experimental data, and the predicted results show excellent agreement with experimental data. We provide detailed fields in VCT and concentration variations of RCS to study the interaction between mixing in VCT and the transient responses of RCS. Moreover, the impacts of the inlet flow rate, inlet nozzle diameter, original concentration, and replenishing temperature of VCT on the RCS concentration characteristic are studied. The inlet flow rate and nozzle diameter of VCT remarkably affect the RCS concentration characteristic. Too-large or too-small inlet flow rates and nozzle diameters will lead to unacceptable long delays. In this work, the optimal inlet flow rate and nozzle diameter of VCT are 5 m³/h and 58.8 mm, respectively. Besides, the impacts of the original concentration and replenishing temperature of VCT are negligible under normal operating conditions.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.17 no.5
• /
• pp.1-6
• /
• 2009

The temperature of exhaust gas was raised by increasing of engine movement on developing engine. Thermal of high temperature and pressure reverse in bellows, because of increasing of engine movement and the thermal performance of converter in combustion. As a result, thermal loss is increased and thermal efficiency is decreased rapidly in bellows, it can occur to damage in mechanical structure. In this study, it was necessary to analyze back pressure performance and thermal characteristic on driving condition in exhaust system. It was adapted braid type bellows and straight type exhaust pipe. It was compared with curve type exhaust pipe for lay-out on considering to design of exhaust system. It was necessary to improve thermal characteristic and back pressure performance so that expansion cavity pipe(ECP) was installed between bellows and catalyst convert. Not only decreasing back pressure was solved but also thermal characteristic problems in exhaust pipe because of increasing capacity. According to this study, the basis of data is presented when new exhaust system is designed.