• Publications of The Korean Astronomical Society
• /
• v.26 no.1
• /
• pp.25-35
• /
• 2011

A diagnostic tool has been proposed to convert the observed surface distribution of hydrogen recombination line intensities into the radial distributions of the electron temperature and the density in HII regions. The observed line intensity is given by an integral of the volume emission coefficient along the line of sight, which comprises the Abel type integral equation for the volume emission coefficient. As the emission coefficient at a position is determined by the temperature and density of electrons at the position, the local emission coefficient resulted from the solution of the Abel equation gives the radial distribution of the temperature and the density. A test has been done on the feasibility of our diagnostic approach to probing of HII regions. From model calculations of an HII region of pure hydrogen, we have theoretically generated the observed surface brightness of hydrogen recombination line intensities and analyzed them by our diagnostic tool. The resulting temperatures and densities are then compared with the model values. For this case of uniform density, errors in the derived density are not large at all the positions. For the electron temperature, however, the largest errors appear at the central part of the HII region. The errors in the derived temperature decrease with the radial distance, and become negligible in the outer part of the model HII region.

• Journal of the Korean Society of Combustion
• /
• v.10 no.1
• /
• pp.1-6
• /
• 2005

This paper presents the combustion characteristics of hydrocarbon fuel from a conventional pressure-swirl nozzle of a small-scale burner. The nozzle has orifice diameters of 0.256 mm and liquid flow rates ranging from 50 to 64 mL/min were selected for the experiments. The furnace temperature distribution along the axial distance, the gas emission such as CO, $CO_2$, NOx, $SO_2$, flue gas temperature, and combustion efficiency were studied. The local furnace and flue gas temperatures decreased with an increase in air velocity. At injection pressures of 1.1 and 1.3 MPa the maximum furnace temperatures occurred closer to the burner exit, at an axial distance of 242 mm from the diffuser tip. The CO and $CO_2$concentrations decreased with an increase in air velocity, but they increased with an increase in injection pressure. The effect of air velocity on NOx was not clearly seen at low injection pressures, but at injection pressure of 1.3 MPa it decreased with an increase in air velocity. The effect of air velocity on $SO_2$ concentration level is not well understood. The combustion efficiency decreased with an increase in air velocity but it increased with an increase in injection pressure. It is recommended that injection pressure less than 0.9 MPa with air velocity not above 8.0 m/s would be suitable for this burner.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• v.10 no.1
• /
• pp.76-82
• /
• 2005

This paper presents the combustion characteristics of hydrocarbon fuel from a conventional pressureswirl nozzle of a small-scale burner. The nozzle has orifice diameters of 0.256 mm and liquid flow rates raging from 50 to 64 mL/min were selected for the experiments. The furnace temperature distribution along the axial distance, the gas emission such as CO, $CO_2,\;NOx,\;S0_2,$ flue gas temperature, and combustion efficiency were studied. The local furnace and flue gas temperatures decreased with an increase in air velocity. At injection pressures of 1.1 and 1.3 MPa the maximum furnace temperatures occurred closer to the burner exit, at an axial distance of 242 mm from the diffuser tip. The CO and $CO_2$ concentrations decreased with an increase in air velocity, but they increased with an increase in injection pressure. The effect of air velocity on NOx was not clearly seen at low injection pressures, but at injection pressure of 1.3 MPa it decreased with an increase in air velocity. The effect of air velocity $SO_2$ concentration level is not well understood. The combustion efficiency decreased with an increase in air velocity but it increased with an increase in injection pressure. It is recommended that injection pressure less than 0.9 MPa with air velocity not above 8.0 m/s would be suitable for this burner.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.59 no.6
• /
• pp.61-71
• /
• 2017

The tracer gas method has an advantage that can estimate total and local ventilation rate by tracing air flow. However, the field measurement using tracer gas has disadvantages such as danger, inefficiency, and high cost. Therefore, the aim of this study was to evaluate ventilation rate in pig house by using the thermal distribution data rather than tracer gas. Especially, LMA (Local Mean Age), which is an index based on the age of air theory, was used to evaluate the ventilation rate in pig house. Firstly, the field experiment was conducted to measure micro-climate inside pig house, such as the air temperature, $CO_2$ concentration and wind velocity. And then, LMA was calculated based on the decay of $CO_2$ concentration and air temperature, respectively. This study compared between LMA determined by $CO_2$ concentration and air temperature; the average error and root mean square error were 3.76 s and 5.34 s. From these results, it was determined that thermal distribution data could be used for estimation of LMA. Finally, CFD (Computational fluid dynamic) model was validated using LMA and wind velocity. The mesh size was designed to be 0.1 m based on the grid independence test, and the Standard $k-{\omega}$ model was eventually chosen as the proper turbulence model. The developed CFD model was highly appropriate for evaluating the ventilation rate in pig house.

• Journal of the Korean Wood Science and Technology
• /
• v.45 no.1
• /
• pp.85-95
• /
• 2017

This study aimed at more precisely estimating the age of big old trees using dendrochronological method. Gesan-gun in Chungbuk (CBGS), Gurye-gun in Jeonnam (JNGR) and Uljin-gun in Gyeongbuk (GBUJ) were study areas and Zelkova serrata (ZS) and Pinus densiflora (PD) selected as protected trees therein were used as experimental tree species. The increment cores were extracted from 12, 8, and 6 ZSs and 10, 3, and 9 PDs in CBGS, JNGR, and GBUJ, respectively, using an increment borer (${\phi}5.2mm$). In order to clearly distinguish tree-ring boundary, the surface in the transverse section was cut for ZS using a sliding microtome and sanded for PD using a sand paper. Ring widths were measured in the resolution of 0.01 mm. Based on the measurement values, 203-year long (1813-2015) ZS local master tree-ring chronologies were successfully established and 175-year long (1841-2015) ZS local master tree-ring chronology for JNGR was also successfully established. In the case of PD, 154-, 175-, and 250-year long local master tree-ring chronologies for CBGS, JNGR, and GBUJ were successfully established, respectively. In the comparisons between local master tree-ring chronologies, they showed low t-values and Glks. According to the comparisons of the local master tree-ring chronologies with 50-year (1950~2000) average temperature and precipitation distribution maps, the annual variations of local master tree-ring chronologies seem to be determined by not temperature but precipitation. For such cross-dating therefore more local master tree-ring chronologies have to be established at the least based on the distribution map for precipitation.

• Proceedings of the KIEE Conference
• /
• 1993.11a
• /
• pp.59-62
• /
• 1993

The evaluation of the temperature of the motor in operation is necessary for smaller and lighter design of motors and for the determination of insulation class. And the evaluation of the temperature in thermal transient state is necessary for the determination of the intermittent rating and the protection from the thermal overload. The temperature can be calculated exactly by considering the loss distribution, the thermal resistances and the thermal capacities dependent on temperature. Using the detailed thermal equivalent circuit, the temperature of any local part of the motor can be evaluated. The comparison between the calculated results and the experiments is performed to verify the validity of the analysis.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1250-1254
• /
• 2004

To develop more compact and light generators which have high capacity, the most important thing that should be considered is the inner cooling system. Under all circumstances, the temperature of rotor and stator windings must be kept below the maximum temperature of insulation to maintain reliability and prolong durability of the machine. Therefore, the development of more effective cooling system and the exact prediction of windings are essential to produce our unique generator model which is reliable and competitive in international market. In this study, the flow of cooling air and the temperature distribution of winding is analyzed by using computational fluid dynamics. This analysis can lead to optimize the structure of cooling system and predict a local temperature rise.

• Transactions of the Korean hydrogen and new energy society
• /
• v.29 no.5
• /
• pp.442-449
• /
• 2018

Research on High temperature polymer electrolyte fuel cell (HT-PEMFC) has actively been conducted all over the world. Since the HT-PEMFC can be operated at a high temperature of $120-180^{\circ}C$ using phosphoric acid-doped polybenzimidazole (PBI) electrolyte membrane, it has considerable advantages over conventional PEMFC in terms of operating conditions and system efficiency. However, If the thermal distribution is not uniform in the stack unit, degradation due to local reaction and deterioration of lifetime are difficult to prevent. The thin plate separator reduces the volume of the fuel cell stack and improves heat transfer, consequently, enhancing the cooling effect. In this paper, a large area flow field of thin plate separator for HT-PEMFC is designed and sub-stack is fabricated. We have studied stack performance evaluation under various operating conditions and it has been verified that the proposed design can achieve acceptable stack performance at a wide operating range.

• Journal of Magnetics
• /
• v.3 no.4
• /
• pp.123-126
• /
• 1998

The magneto-impedance (MI) has been measured in the annealed Co66Fe4Ni1B14Si15 amorphous ribbon for the evaluation of anisotropy field. MI at the frequency of 10 MHz is related to the transverse permeability from rotational magnetization depending on the local anisotropy field. MI varies sensitively with the annealing temperature, reflecting the change of anisotropy field distribution. The local anisotropy fields evaluated from MI Profiles are discussed in terms of the magnetic softness and microstructural change by the annealing.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.16 no.1
• /
• pp.81-88
• /
• 1987

In this paper, the local effective thermal conductivities and calculated by using the actual temperature distribution in packed bed. The variations of these are investigated for radius and air stream direction, flow rate and particle diameter. The resulting local effective thermal conductivi-ties are classified in the inner zone of bed and vicinity zone of the wall surface. Also these are related to dimensionless axial direction position, radius direction position, and particle diameter and Reynolds number which uses particle diameter as the characteristic length. If these correla-tions are represented by function, the equation is showed in Eq. (3-4). This equation is well satisfied with experimental results within $\pm25\%.$