• Title, Summary, Keyword: melting time

Search Result 566, Processing Time 0.115 seconds

A Study on the Characteristics Analysis of Strands Melted by Over Current (과전류에 의해 용단된 소선의 특성해석에 관한 연구)

  • Choi, Chung-Seog;Kim, Hyang-Kon;Kim, Dong-Ook
    • Journal of the Korean Society of Safety
    • /
    • v.19 no.1
    • /
    • pp.60-65
    • /
    • 2004
  • The PVC insulated flexible cords are used mainly as power supply cords of electric appliance. This electric wire is a stranded wire consisted of dozens of strands. In case stranded wires are disconnected by mechanical stress, it weakens electrically. Finally, the over current flows through stranded wires, and electrical fire occurs. In this study, we analyzed the melting properties of strands by over current, such as melting process, melting current and melting time. And we analyzed that quantity of heat for melting, a cross sectional structure, and surface structure by optical microscope and SEM. As analysis results, melting time decreased as melting current increased. And quantity of heat for melting was low, too. From the cross sectional structure of melted wire, when a melting current low and melting time long, it was found that the dendrite structure grew. However, the dendrite structure is hard to grow because growing time is not enough when a melting current high and melting time short.

Development of glass melting furnace using both plasma and combustion (플라즈마/연소 융합기술을 이용한 세라믹계 유리 분말 기중용해로 개발)

  • Dong, Sangkeun;Lee, Eunkyung;Jeong, Woonam
    • 한국연소학회:학술대회논문집
    • /
    • /
    • pp.203-205
    • /
    • 2014
  • This paper is suggesting about glass melting technology, using both plasma and combustion heat source. The mixed flame was formed to flow pattern of turning by plasma and combustion in melting zone. The burning time was extremely extended for vitrification of raw materials in melting zone, as a result, meting time was significantly reduced. This system was designed to smaller size than existing glass melting facilities. We had achieved to 30% energy saving, due to reduce residence time of melted materials inside furnace.

  • PDF

The effects of heat treatment condition on critical characteristics of HTSC bulk (열처리조건이 초전도벌크의 임계특성에 미치는 영향)

  • 임성훈;한태희;박경국;조동언;이중근;한병성
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.356-359
    • /
    • 1997
  • The Effects of different melting temperature and holding time in the melting temperature on J$\sub$c/ of YBa$_2$Cu$_3$O$\sub$x/ based superconducting bulk using MPMG process were investigated. the value of critical current density was the largest at l120$^{\circ}C$, the melting temperature which is appointed to the mid point of (Y$_2$BaCuO$\sub$5/ + Liquid)region. With the melting temperature in which the value of J$\sub$c/ is the largest, J$\sub$c/ was again measured to see whether the holding time at this proper melting temperature has the effect on the critical characteristics. From the result above it was concluded that the melting temperature and holding time were important to improve the J$\sub$c/ and the formation of the Y$_2$BaCuO$\sub$5/. In this paper, the melting temperature obtained was l120$^{\circ}C$ and propel holding time could be obtained as 20 minute and the more holding time was not effective in the J$\sub$c/ improvement as well as the formation of Y$_2$BaCuO$\sub$5/.

  • PDF

The Effects of Melting Temperature and Holding Time on Critical Characteristics of HTSC Fabricated by Melting Method (용융온도와 유지시간이 용융법으로 제작한 고온초전도체의 임계특성에 미치는 영향)

  • Lim, Sung-Hun;Han, Tae-Hee;Park, Kyung-Kuk;Yim, Seong-Woo;Cho, Dong-Eon;Han, Byoung-Sung
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.11 no.2
    • /
    • pp.154-161
    • /
    • 1998
  • The effects of melting temperature and holding time on the critical current density($J_c$) of $YBa_2Cu_3O_x$ based superconducting bulk fabricated by MPMG process were investigated. The amount of the formed $Y_2BaCuO_5$ phases increased with the melting temperature. However, the value of critical current density was highest at 1120 $^{\circ}C$. With this proper melting temperature, the effect of holding time on the critical characteristics was also investigated. In the case of Ag addition, the volume of the formed $Y_2BaCuO_5$ phase when the amount of Ag addition was 10 wt% and 20 wt% was observed to be highest at 20 minute and 40 minute respectively. But in the specimen without Ag, volume of $Y_2BaCuO_5$ phase increased as the holding time increased. The proper melting temperature and the holding time obtained were 1120 $^{\circ}C$ and 20 minute. The long holding time was not effective for the $J_c$ improvement as well as the formation of $Y_2BaCuO_5$.

  • PDF

Refining of Invar and Permalloy Fe-Ni Alloys by $Ar/Ar-H_2$ Plasma and Electron Beam Melting (Ar/Ar-$H_2$ 플라즈마 및 전자선 용해에 의한 인바 및 퍼멀로이 Fe-Ni 합금의 정련)

  • Park, Byung-Sam;Baik, Hong-Koo
    • Journal of Korea Foundry Society
    • /
    • v.15 no.2
    • /
    • pp.175-183
    • /
    • 1995
  • It is difficult to remove such interstitial impurities as sulfur, oxygen, hydrogen and carbon in Fe-Ni alloys. Thermodynamic and kinetic studies were carried out on the behavior of hydrogen gas, oxygen gas, Si, Al and slag, and the reaction time by the $Ar/Ar-H_2$ plasma and electron beam melting. After the addition of Al, Si, they were melted by Ar plasma with reaction time changed. 80%Ni-Fe alloys showed a better deoxidation than 36%Ni-Fe alloys. At $Ar-H_2$ plasma melting, the deoxidation was significant. In the case of the electron beam melting, the residual oxygen was higher than in Ar plasma melting because electron beam melting temperature was lower than that of Ar plasma. For the decaburization, it was melted by $Ar-O_2$ plasma melting, which could remove effectively carbon by activated oxygen in plasma. We added slag to Fe-Ni alloys for the desulfurization. As the result of this experiments, the amount of residual sulfur was not changed according to the slag ratio and reaction time.

  • PDF

Thermal Instability of Natural Convection in a Glass Melting Furnace (유리 용융로에서 자연대류의 열적 불안정성)

  • Lim, Kwang-Ok;Lee, Kwan-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.22 no.12
    • /
    • pp.1774-1783
    • /
    • 1998
  • The transition from steady laminar to chaotic convection in a glass melting furnace specified by upper surface temperature distribution has been studied by the direct numerical analysis of the two and three-dimensional time dependent Navier-Stokes equations. The thermal instability of convection roll may take place when modified Rayleigh number($Ra_m$) is larger than $9.71{\times}10^4$. It is shown that the basic flows in a glass melting furnace are steady laminar, unsteady periodic, quasi-periodic or chaotic flow. The dimensionless time scale of unsteady period is about the viscous diffusion time, ${\tau}_d=H^2/{\nu}_0$. Through primary and secondary instability analyses the fundamental unsteady feature in a glass melting furnace is well defined as the unsteady periodic or weak chaotic flow.

Detection of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp. and Staphylococcus aureus using duplex real-time PCR assay with melting curve analysis on fresh lettuce

  • Lee, Na-Ri;Kwon, Kyung-Yoon;Choi, Sung-Wook;Koo, Min-Seon;Chun, Hyang-Sook
    • Journal of Food Hygiene and Safety
    • /
    • v.26 no.2
    • /
    • pp.114-119
    • /
    • 2011
  • In this study, two duplex real-time PCR approach with melting curve analysis is presented for the detection of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp. and Staphylococcus aureus, which are important food-borne bacterial pathogens usually present in fresh and/or minimally processed vegetables. Reaction conditions were adjusted for the simultaneous amplification and detection of specific fragments in the ${\beta}$-glucuronidase (uidA, E. coli), thermonuclease (nuc, S. aureus), hemolycin (hly, L. monocytogenes) and tetrathionate reductase (ttr, Salmonella spp.) genes. Melting curve analysis using a SYBR Green I real-time PCR approach showed characteristic $T_m$ values demonstrating the specific and efficient amplification of the four pathogens; $80.6{\pm}0.9^{\circ}C$, $86.9{\pm}0.5^{\circ}C$, $80.4{\pm}0.6^{\circ}C$ and $88.1{\pm}0.11^{\circ}C$ for S. aureus, E. coli O157:H7, L. monocytogenes and Salmonella spp., respectively. For all the pathogens, the two duplex, real-time PCR was equally sensitive to uniplex real-time PCR, using same amounts of purified DNA, and allowed detection of 10 genome equivalents. When our established duplex real-time PCR assay was applied to artificially inoculated fresh lettuce, the detection limit was $10^3$ CFU/g for each of these pathogens without enrichment. The results from this study showed that the developed duplex real-time PCR with melting curve analysis is promising as a rapid and cost-effective test method for improving food safety.

Thermal Behaviour of Polyglycolic Acid in Melt Polymerization of Glycolide (글리콜리드 용융중합시 폴리글리콜산의 열적 거동)

  • 김학용;길명섭
    • Textile Science and Engineering
    • /
    • v.35 no.1
    • /
    • pp.38-43
    • /
    • 1998
  • Thermal behaviour of polyglycolic acid in melt polymerization of glycolide was investigated as a function of lauryl alcohol content. There were showed three endothermic peaks such as glycolide melting peak, lower molecular weight melting (oligomer) peak and higher molecular weight melting peak at early stage on glycolide melt polymerization under lauryl alcohol. But there were showed only two peaks, glycoside melting peak and lower molecular weight melting peak without laurel alcohol. Conversion increased slowly with the reaction time up to 50 minutes, and then gave a sudden increase above that. The reaction time to disappear in glycolide melting peak during polymerization was shortened with the increase of lauryl alcohol content. Zero-shear viscosity of polyglycolic acid decreased with the increase of free acid content in glycolide.

  • PDF

An analysis of snow melting process for a study of defrosting phenomena (제상 현상 연구를 위한 눈 융해 과정 해석)

  • Lee, K.S;Ko, Y.W.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.11 no.1
    • /
    • pp.38-47
    • /
    • 1999
  • An improved one-dimensional modeling of snow melting was obtained by considering both the effect of heat capacity and the decreasing influence of porosity. Using the improved model, the effects of initial snow temperature, initial snow density and the heat flux on the snow melting were investigated. It is found that the drainage starting time is delayed and the drainage rate becomes smaller with lower initial snow temperature. ResuIts also show that the drainage starts at the same time when an initial snow density is over a certain value. Melting efficiency increases linearly with an increasing initial snow temperature. With increasing the initial density of the snow and the amount of heat supplied, the melting efficiency increases, then converges to a constant value.

  • PDF

An Experimental Study of Accelerating Phase Change Heat Transfer

  • Oh, Yool-Kwon;Park, Seul-Hyun;Cha, Kyung-Ok
    • Journal of Mechanical Science and Technology
    • /
    • v.15 no.12
    • /
    • pp.1882-1891
    • /
    • 2001
  • The present paper investigated the effect of ultrasonic vibrations on the melting process of a phase-change material (PCM). Furthermore, the present study considered constant heat flux boundary conditions unlike many of the previous researches adopted constant wall temperature conditions. Therefore, in the present study, modified dimensionless parameters such as Ste* and Ra* were used. Also, general relationships between melting with ultrasonic vibrations and melting without ultrasonic vibrations were established during the melting of PCM. Experimental observations show that the effect of ultrasonic vibrations on heat transfer is very important throughout the melting process. The results of the present study reveal that ultrasonic vibrations accompany the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They enhance the melting process as much as 2.5 tildes, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, various time-wise dimensionless numbers provide conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.

  • PDF