• Fire Protection Technology
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• s.29
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• pp.39-45
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• 2000

All objects emit thermal radiation and this radiation is the basis of the techniques used to detect flames. The usual phenomena occurring in the initial stage of a fire are generally invisible products of a combustion and visible smoke. Liquid or gaseous materials do not undergo a smoldering stage such fires develop very rapidly. Also, the heat generated by the initial flames is usually not sufficient to active a heat detector. In this case the most effective criterion for automatic fire detection is the flame. In fire regulation of korea, the compulsory standard provided that a flame detector shall be installed a place of the attachment hight of detector is higher than 20 m, chemical plants, hangar, refinery, etc.. The result of the research and development are discriminated between a flame and other radiant emitters, developed PZT pyroelectric element is based on the use of photo-voltanic cell, developed IR band-pass filter that only allow a 4.3 radiation wavelength to reach the sensors and developed IR flame detector.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1516-1521
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• 2004

An inverse boundary analysis of surface radiation in an axisymmetric cylindrical enclosure has been conducted in this study. Net energy exchange method was used to calculate the radiative heat flux on each surface, and a hybrid genetic algorithm was adopted to minimize an objective function, which is expressed by sum of square errors between estimated and measured heat fluxes on the design surface. We have examined the effects of the measurement error as well as the number of measurement points on the estimation accuracy.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.2
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• pp.82-87
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• 2022

The PZT piezoelectric ceramic on the copper alloy plate shows a extraordinary pattern resulted from the electromagnetic and thermal radiation induced by copper coil. The Eddy current or magnetic field by the polarization of PZT grains contained Pb, Zr, Ti with oxide is performed to show the change of array pattern at piezoelectric grains, especially wave-shaped or wrinkled configuration along with lines of electromagnetic field are becoming larger than before while applying the coil induction.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.3
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• pp.319-327
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• 2001

The objective of this study is to clarify the effect of thermal radiation environments on human thermal comfort, depending on different canyon types and surface materials on the human thermal comfort in a housing complex in Pohang city, Korea. For this purpose, the operative temperature and new effective temperature were calculated based on the modified mean radiant temperature of canyon models variated by the existence of direct radiation existence, surface materials, and the width and length of the street spaces in a housing complex. These indices for the canyon have been calculated from the meteorological data of Pohang city, which include air temperature, relative humidity, air velocity, global solar radiation and cloud. And the monthly averages of these climate factors measured at noon have been used. The results are as follows: (1) It is revealed that the short-wave radiosity reached the human body is affected by direct solar radiation and surface materials, and the long-wave radiosity by canyon types. (2) The existence of direct solar radiation, the kinds of surface materials and canyon types affect operative temperature($OT_n$) and new effective temperature($ET^*{_n}$). (3) The analysis of the human heat balance in the canyon indicates that the influence of radiation on human body is marc likely to be affected by the existence of direct solar radiation on human model.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.842-846
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• 2001

Our company produces boilers for industrial usages or power plants. The aim of this study is to investigate the flame structure, heat transfer to evaporator tube wall and NOx emission in the furnaces. Also we are to derive correct FEGT(Furnace Exit Gas Temperature) characteristic curve. When we design furnace and superheater, economizer etc. FEGT characteristic curve is very important factor for optimum design. We calculated turbulent reacting flow, heat transfer and NOx emission in furnace by using numerical modeling with the help of commercial code. Three dimensional steady state calculation is done. k-e turbulence model and equilibrium chemistry combustion model with $\beta-probability$ density function is used. To calculate radiation heat transfer discrete ordinates model is used. And we measured FEGT at several operating plants. Measurement is done by R-type thermocouple. Radiation shield is attached to the thermocouple to prevent radiation effect. Measured and calculated results show good agreement. And we could understand the flame structure and NOx formation positions in each furnaces.

• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.7-13
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• 2017

An experimental study was conducted to identify the quantitative measurement bias for the bare-bead thermocouple (TC), which was widely used for measuring temperature in fire experiments. To this end, an apparatus could be controlled individually gas flow rate, preheating temperature and incident radiative heat flux was developed to simulate the thermal environments of fire. A relative measurement bias of bare-bead TC was evaluated with the comparison of double-shield aspirated TC. As a result, the relative measurement bias of bare-bead TC was gradually increased with the increase in radiative heat flux with constant gas temperature. The relative bias was also significantly increased with the decrease in gas temperature. Quantitatively, at the gas temperature of $20^{\circ}C$, the bare-bead TC had the relative bias of approximately 400% with the radiative heat flux of $20kW/m^2$ corresponding to thermal radiation level of the flashover. The present study was intend to provide fire researchers with methodologies for the reanalyses of temperature measured using bare-bead TC, radiation corrections, and validation of fire modeling.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.3
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• pp.294-302
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• 1998

Ignition characteristics of a vertical solid fuel plate with block have been investigated experimentally. For low radiant heat flux, ignition does not occur in a vertical solid fuel plate without block. In the case with the block on a vertical fuel plate, however, ignition can occur by increasing the residence time and the time to absorb the incident radiation flux by fuel vapor in gas phase. The ignition occurs below block and the point varies according to the block location and the block height. As the block height increases, the block locates at higher position, and the hot wall temperature increases, the ignition delay time decreases. Also as the initial temperature of fuel plate rises, the ignition delay time of the solid fuel plate decreases. The temperature distribution of solid fuel plate with block is nearly proportional to the radiant heat flux distribution. Therefore, the effect temperature by natural convection heat transfer is of the same order as that of inhibition of temperature increase by pyrolysis.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.316-321
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• 2000

In this study, heat collecting performance was study of flat plate solar collector by the angle. A method of study on were made turn out artificial sun by the angle of 0, 15, 30 degrees. The heat performances were measured the tube array surface temperature by thermo-couple. The winter season natural condition for 4 times on the angles of various general and emboss glass at optimum distance(0.68m) calculated of between sun and solar collector. To sum up temperature rise is appear more or less that emboss glass is all the better for general glass. The temperature variable at below of 30 degree was appear very less. The maximum performance of this system at that it is tilt angle of 30 with general glass is appear Q:11.54(kcal/min) and ${\Delta}T=18.9^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.10
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• pp.1363-1370
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• 1997

Single liquid droplet combustion processes including heating, evaporation, droplet burning and flame radiation were theoretically investigated by adopting nongray gas radiation model for the radiative transfer equation (RTE). n-Heptane was chosen as a fuel and the numerical results were compared with the experimental data available in the literature. The discrete ordinate method (DOM) was employed to solve the radiative transfer equation and the weighted sum of gray gases model (WSGGM) was applied to account for nongray effect by CO$_{2}$, and H$_{2}$0. Therefore, detailed effects by nongray gas and its comparison with the gray gas model could be figured out in the results. It is found that the radiative heat flux is higher when the nongray model is used, thereby reducing the maximum gas temperature and the flame thickness, but the total burning time increases due to the deceased conductive heat flux in nongray model. Consequently, a better agreement with experimental data could be obtained by using nongray model.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.89-96
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• 2005

This study has been performed on the mechanism of heat transfer between stratospheric airship and its surroundings while the airship is staying in the air at the altitude of 20km. The computational grid of airship has been generated and the results influenced by the number and the shape of grids have been compared. The temperature distributions have been obtained through this thermal analysis considering three modes of heat transfer - conduction, convection and radiation - in stratospheric conditions. Based on the airship's surface and inner temperature variations, the influence of temperature distributions on the helium envelope and the payload has been predicted.