• Title, Summary, Keyword: Melting temperature

Search Result 1,592, Processing Time 0.044 seconds

The Microstructural Changes of Free-Annealed Nylon 6 Filament Yarns - Comparison of UDY, POY, and FDY - (무긴장 열처리 나일론 6 필라멘트사의 내부구조 변화 - 미연신사, 부분배향사 및 완전연신사의 비교 -)

  • Lee Jung Ju;Cho Gil Soo
    • Journal of the Korean Society of Clothing and Textiles
    • /
    • v.13 no.1
    • /
    • pp.43-47
    • /
    • 1989
  • The microstructural changes of nylon 6 UDY, POY and FDY were compared after free-annealing through crystallinity, birefringence, and melting behavior analyses. Free-annealing was done at various temperatures $(120^{\circ}C\;,140^{\circ}C,\;160^{\circ}C,\;180^{\circ}C,\;200^{\circ}C)$ and times (15 min., 30 min., 60 min.) using vaccum oven. Crystallinity was measured by the density gradient column technique and birefringence was measured using a Nikon polarizing microscope with a quartz wedge and Senarmont compensator. Melting behavior was investigated on the basis of DSC melting corves. Crystallinites of specimens increased as the treatment temperature and time increased. Birefringence of UDY increased after annealing and increased as the treatment temperature increased. On the other hand, those of POY and FDY decreased after annealing. Especially, the changes of crystallinity and birefringence of treated POY were particularly lower than those of treated UDY and FDY. Melting peaks of untreated UDY, POY and FDY were different in the position and the shape, but little change was seen in melting peaks in spite of increasing the annealing temperature and time. UDY and FDY showed single melting peaks in all the specimens. But POY showed double melting peaks, which means the coexistences of crystals with different thermal properties.

  • PDF

Seed melting during seeded-melt growth process of YBCO superconductors

  • Kim, Chan-Joong;Hong, Gye-Won;Kim, Ho-Jin
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.14-16
    • /
    • 2002
  • Melting and re-solidification nature of $SmBa_2Cu_3O_{7-y}$ (Sm123) grains in Ba-Cu-O (Ba:Cu=3:5) liquid containing 0.7 at.% yttrium were investigated at the temperature lower than its melt point. When Sm123 grains/liquid powder compacts were heated to a temperature between two melting points of Ba-Cu-O liquid ($1000^{\circ}C$) and a Sm123 phase ($1060^{\circ}C$) and held at this temperature for appropriate time, Sm123 grains melted partly in the liquid that was formed by melting of the liquid-forming powder. During subsequent slow cooling, (Sm,Y)$Ba_2Cu_3O_{7-y}$ solidified at the outer parts of the unmelted Sm12 grains, which is distinguished from the core regions by lower $Sm_2BaCuO_5$ (211) density.

  • PDF

A Basic Study of the Snow Melting System for the Anti-Freezing Road using the Pulsating Heat Pipe (PHP를 이용한 도로융설 시스템에 관한 기초연구)

  • Kim, J.S.;Ha, S.J.;Son, K.J.
    • Journal of Power System Engineering
    • /
    • v.14 no.3
    • /
    • pp.19-24
    • /
    • 2010
  • The purpose of this study is to develop a snow melting system using the pulsating heat pipe(PHP). The experimental apparatus is consisted of a PHP, a concrete structure, a constant water thermostatic bath and a flowmeter. The experiment was performed at the outdoor air temperature of $-8^{\circ}C$ and inlet temperature of hot water of $75^{\circ}C$. PHP is the closed and non-loop type heat exchanger which is charging R-410A as an operating fluid. As experimental results, the temperature profile of vertical and horizontal orientation of concrete structure was measured with operating time. The heat flux of the snow melting was required more than 300 $W/m^2$. We confirmed that the snow melting system using the PHP was useful for anti-freezing road.

Zone-melting Process of NdBaCuO under Low Oxygen Pressure

  • Soh, Dea-Wha
    • Transactions on Electrical and Electronic Materials
    • /
    • v.3 no.2
    • /
    • pp.24-27
    • /
    • 2002
  • The NdBaCuO superconductor samples were zone-melted in low oxygen partial pressure (1%O$_2$+99%Ar). The zone-melting temperature was decreased about 12$0^{\circ}C$ film 1,06$0^{\circ}C$, the zone-melting temperature in air. Thus the loss of liquid phase (BaCuO$_2$ and CuO) was reduced during: the zone-melting process. The content of non-superconducting phase Nd422 in zone-melted NdBaCuO samples was clearly decreased and, therefore, the substitution of Nd for Ba was occurred. The superconductivity of zone-melted Nd$_{1+x}$Ba$_{2-x}$Cu$_3$O$_{y}$ prepared under low oxygen partial pressure was distinctively improved.d.d.d.

Time-dependent natural convection in a glass melting furnace (유리용융로의 시간종속 자연대류)

  • Im, Gwang-Ok;Lee, Gwan-Su
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.21 no.7
    • /
    • pp.919-927
    • /
    • 1997
  • The main purpose of this study is to determine bifurcation as the primary instability of a glass melting furnace. Steady-state and unsteady characteristics of natural convection in the partially open cavity as appeared in a glass melting furnace is investigated by using numerical analysis. Three types of convection, such as steady laminar, unsteady periodic or unsteady quasi-periodic convection may occur according to the temperature difference between upper two isothermal surfaces along the depth of cavity in a glass melting furnace. In the temperature difference of 150-900 K between batch and free surface, the larger the temperature difference, the weaker the convection strength and unsteadiness. Since the glass viscosity is increasing exponentially in the lower temperature, the batch freezes the thermofluidic field especially below the surface of it. If the depth of cavity is 0.5 m, the bifurcation to time-dependent natural convection may occur in the range of 60-650 K. If that is 1.0 m, it may occur in the whole range of temperature difference.

An Experimental Study on the Melting of a Horizontal Cylindrical Ice-Bar Submerged in Water (물속에 水平으로 잠겨 있는 圓 形 얼음 棒 의 融解現象 에 관한 實驗的 硏究)

  • 이동욱;유상신
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.9 no.4
    • /
    • pp.414-420
    • /
    • 1985
  • The melting phenomenal of the horizontal cylindrical ice-bar submerged in water are experimentally investigated for the temperature range from 2.5.deg. C to 15.deg. C. The shapes of the melting ice-bar are recorded by the Photo-elasticity Apparatus with modification of the test section. The shadowgraphs of the melting ice-bar show that water adjacent to the bar flows upward for the temperature range from 2.5.deg. C to 5.6.deg. C while above the temperature of 5.6.deg. C the flow is downward direction. The local and average Nusselt numbers become minimum at 5.6.deg. C which is considered as a critical temperature and the Nusselt numbers increase as temperature difference from the critical temperature increase.

A Study on the Fabrication of Bi System Thick Film Using Melting Process (용융법에 의한 Bi계 Thick Film 합성)

  • Lee, Sang-Heon
    • The Transactions of The Korean Institute of Electrical Engineers
    • /
    • v.58 no.9
    • /
    • pp.1775-1777
    • /
    • 2009
  • BiSrCaCuO films were prepared on MgO single substerate at $885^{\circ}C$ by melt process. The films showed superconductivity above liquid nitrogen temperature (Tc= 96K). To investigate the effect of a melting temperature on the forming of the surface texturing, the samples were prepared under various temperature. The used powder was of high Tc phase. It is implies that the origin of the properties due to the heat treatment.

Study on the Melting Point of Ar by Molecular Dynamic Simulation (Ar의 녹는점에 관한 분자동역학적 고찰)

  • Chung, Jae-Dong
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.19 no.12
    • /
    • pp.883-888
    • /
    • 2007
  • As a starting point of investigating what molecular dynamic simulations can reveal about the nature of atomic level of heating and cooling process, argon described by the LJ potential is considered. Stepwise heating and cooling of constant rates are simulated in the NPT (constant number, pressure and temperature) ensemble. Hysteresis is found due to the superheating and supercooling. Drastic change of volume and energy is involved with phase change, but the melting point can not be obtained by simply observing the changes of these quantities. Since liquid and solid phases can co-exist at the same temperature, Gibbs free energy should be calculated to find the temperature where the Gibbs free energy of liquid is equal to that of the solid since the equilibrium state is the state of minimum Gibbs free energy. The obtained melting temperature, $T^*=0.685$, is close to that of the experiment with only 2% error.

Melting of Ice on the Heating Plate with Split Fins

  • Hong, Hi-Ki;Kim, Moo-Geun
    • International Journal of Air-Conditioning and Refrigeration
    • /
    • v.9 no.2
    • /
    • pp.1-7
    • /
    • 2001
  • One of the important applications of a contact melting process is a latent thermal energy storage system owing to its high heat flux and small temperature variation. In some previous works, the split fins have been employed in order to enhance the melting rate. In the present work, the direct contact melting was experimentally investigated using an ice as specimen for both split and non-split fins. It was shown that the contact melting by split fins increases the melting rate compared to that of non-split ones.

  • PDF

Analysis of PCM Wallboards Design Parameters using Dynamic Energy Simulation (동적 에너지 시뮬레이션을 이용한 PCM보드의 설계변수 분석에 관한 연구)

  • Lee, Jin-Uk;An, Sang-Min;Kim, Taeyeon;Lee, Seung-Bok
    • KIEAE Journal
    • /
    • v.12 no.4
    • /
    • pp.97-104
    • /
    • 2012
  • A phase-change material is a substance with a high heat of fusion which, melting and freezing at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid. Therefore, PCMs are classified as latent heat storage (LHS) units. The purpose of this study is to analyze PCM wallboard design parameters using dynamic energy simulation. Among the factors of PCM, melting temperature, latent heat, phase change range, thermal conductivity are very important element to maximize thermal energy storage. In order to analyze these factors, EnergyPlus which is building energy simulation provided by department of energy from the U.S is used. heat balance algorithm of energy simulation is conduction finite difference and enthalpy-temperature function is used for analyzing latent heat of PCM. The results show that in the case of melting temperature, the thermal energy storage could be improved when the melting temperature is equal to indoor surface temperature. It seems that when the phase change range is wide, PCM can store heat at a wide temperature, but the performance of heat storage is languished.