• Title/Summary/Keyword: 가열 속도

Search Result 570, Processing Time 0.029 seconds

A Study of Mixed Convection on a Flat Plate with an Unheated Starting Length (비가열부가 있는 평판에서의 혼합대류에 관한 연구)

  • 김민수;강영규;백병준;박복춘
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.17 no.5
    • /
    • pp.1304-1312
    • /
    • 1993
  • The buoyancy effects on mixed convection heat transfer over a flat plate surface with unheated starting length is reported. The governing equations are solved by a finite difference method using Patankar scheme and the solution was numerically obtained for various mixed convection parametr $Gr_{x}/Re_{x}^3$, and Prandtl number of 0.7 Local heat flux was measured by using Schilieren Interferometer. The local heat transfer results show that the presence of the unheated starting length can significantly accentuate the effects of buoyancy. The degree of accentuation of the buoyancy effects is strongly influenced by the magnitude of $Gr_{x}/Re_{x}^3$. When the parameter is larger than the order of $10^{-3}$, the contribution of natural convection to the heat transfer coefficients increased significantly due to the unheated starting length. In contrast, when $Gr_{x}/Re_{x}^3$ is smaller then about $10^{-5}$ , the buoyancy contribution is essentially unaffected by the unheated starting length. The shape of the velocity profile is also found to be highly responsive to the interaction between the buoyancy and the starting length.

Workability of Polymeric Concrete for Lunar Infrastructure (달 시설물을 위한 폴리머 콘크리트의 시공성 연구)

  • Lee, Jaeho;Lee, Tai Sik;Ann, Ki Yong;Chang, Byung Chul
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.37 no.2
    • /
    • pp.507-512
    • /
    • 2017
  • For manned planetary exploration, human beings are developing technologies that can permanently reside on the planet, and the basic three elements of residence, such as clothing and shelter, are required to support essential technologies in construction. In order to develop infrastructure construction technology internationally, various materials and methods such as local cementation, sulfur and aluminum have been tried. in this study, a purpose is proposed a polymer concrete construction validation technology that appropriates the conditions required for manmade exploration in order to develop construction infrastructure material technology using polymer. Concrete specimens with a 10% weight ratio polymer prepared by heating on the bottom were stabilized after 2 hours of heating, and the strength was lower than the top heating method, but the solidifying speed was 2 times faster. These results are expected to be applicable not only to construction of lunar facilities for manned exploration but also to improve the construction of infrastructures such as roads and levees to prevent dust.

Changes of Properties of Gel from Frozen Alaska Pollack Meat Paste (명태 냉동 고기풀의 gel 성상 변화)

  • JUNG Woo-Jin;PARK Seong-Min;LEE Kang-Ho;LEE Keun-Tai
    • Korean Journal of Fisheries and Aquatic Sciences
    • /
    • v.26 no.2
    • /
    • pp.133-140
    • /
    • 1993
  • In order to obtain the fundamental factors influencing on gelation of Alaska pollack meat paste during processing, the interactions among hydrophobic residues, disulfide bonds and gel strength were investigated. Hydrophobic interactions between actomyosin molecules were strengthened when the temperature was raised from $5^{\circ}C\;to\;65^{\circ}C$, especially between the range from $25^{\circ}C\;to\;35^{\circ}C$. Total SH groups were decreased at the higher heating temperature and the severe decreasing occurred from $45^{\circ}C$. However the amounts of free SH groups were increased significantly over $45^{\circ}C$.

  • PDF

A study on SiC crystal growth by sublimation process using resistance heating method (저항가열 방식을 적용한 승화법에 의한 SiC 결정 성장에 대한 연구)

  • Kang, Seung Min
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.25 no.3
    • /
    • pp.85-92
    • /
    • 2015
  • SiC crystals are well known for their true potential as high power devices and their crystal growth activity is actively carried out in domestic as well as in abroad. Until now the process to grow this crystal has been done by sublimation technique using radio frequency induction heating method. However in order to get better quality of SiC crystals, the stability of temperature is needed because SiC crystal tends to transform to other polytypes. So, the possibility of SiC crytals growth was evaluated by different heating method. This study aimed to observe whether the resistant heating method would show stable growth and better quality of SiC single crystal than that of RF induction heating. As a result, polycrystalline SiC crystals were grown by the growth rate of 0.02~0.5 mm/hr under the condition of $2100{\sim}2300^{\circ}C$ at the bottom side of the crucible and 10~760 torr. The polycrystalline SiC crystals with 0.25 and 0.5 mm in thickness were grown successfully without seed and characterized by optical stereo microscopic observation.

Establishment of $F_o-value$ Criterion for Canned Smoked-Oyster In Cottonseed Oil (훈제 굴 통조림의 가열살균기준 설정에 관한 연구)

  • HAN Bong-Ho;LEE Chang-Kook;IM Chi-Won;YU Hong-Sik
    • Korean Journal of Fisheries and Aquatic Sciences
    • /
    • v.28 no.3
    • /
    • pp.347-353
    • /
    • 1995
  • [ $F_o-value$ ] of canned smoked-oyster in cottonseed oil (SOCO) were measured using a microcomputer aided $F_o-value$ measuring system, and the microbiological safety of the canned SOCO was evaluated to optimize the energy consumption. Most of the microorganisms in raw oyster were saprophytes. No microorganisms were detected from the canned SOCO which was pretreated by conventional procedure and sterilized at $110^{\circ}C$ with $F_o-value$ of 5.92min and over. The most heat resistant microflora isolated from the raw oyster was Bacillus sp.. D-value at $121.1^{\circ}C$ and z-value of spores of Bacillus sp. in the SOCO homogenate were 4.10min and $10,91^{\circ}C$, respectively. After 120 days storage at $50^{\circ}C$, no growth of microorganisms was recognized from the canned SOCO with $F_o-value$of 5.92min.

  • PDF

Monitoring of Free Sugar and Amino Acid of Red Bean Paste by Corn Syrup Concentration and Heating Treatment Conditions (물엿농도와 열처리 조건에 따른 팥앙금 호화액의 당 및 아미노산의 변화 모니터링)

  • Rho, Min-Whan;Lee, Tae-Kyoo
    • Food Science and Preservation
    • /
    • v.13 no.5
    • /
    • pp.581-588
    • /
    • 2006
  • Dynamic changes of free sugar and amino acid in the mixture of red bean paste sediment by corn syrup concentration and heating conditions were monitored. Glucose and fructose contents of red bean paste increased with an increasing blown color intensity. Amino acid content was affected by the heating temperature, increased with an increase in browning color intensify. Browning color intensity of each samples increased up to $95^{\circ}C$, but decreased above $95^{\circ}C$. This result was the same tend as changes of glucose and amino acid. The result of correlation coefficients among free sugar amino acid and browning color intensity show that increase in browning color intensity was not correlated directly with changes of free sugar and amino acid content. It seems that the contents of free sugar and amino acid resolved from saccharides and protein were much mote than contents nea for browning reaction.

A Molecular Dynamics Study on the Liquid-Glass-Crystalline Transition of Lennard-Jones System (한 Lennard-jones 시스템의 액체-유리-결정 전이에 관한 분자동역학 연구)

  • Chang, Hyeon-Gu;Lee, Jong-Gil;Kim, Sun-Gwang
    • Korean Journal of Materials Research
    • /
    • v.8 no.8
    • /
    • pp.678-684
    • /
    • 1998
  • By means of constant- pressure molecular dynamics simulations, we studied the liquid- glass- crystalline transition of a system composed of Lennard- Jones particles with periodic boundary conditions. Atomic volume and enthalpy were calculated as functions of temperature during heating and cooling processes. The Wendt- Abraham ratio derived from radial distribution function and the angular distribution function characterizing short range order were analyzed to distinguish between liquid, glass and crystalline states. A liquid phase resulting from a slow heating of an initial fee crystal amorphized on fast quench, but it crystallized on slow quench. When slowly heated, the amorphous phase from fast quench crystallized into an fee structure. A system with free surface was shown to melt from the surface inward at a lower temperature than bulk system and to have a strong tendency for crystallization even during a fast quench from a liquid state.

  • PDF

Analysis of Hyperbolic Heat Conduction in a Thin Film (박막에서 쌍곡선형 열전도 방정식에 의한 열전도 해석)

  • 정우남;이용호;조창주
    • Journal of Energy Engineering
    • /
    • v.8 no.4
    • /
    • pp.540-545
    • /
    • 1999
  • The classical Fourier heat conduction equation is invalid at temperatures near absolute zero or at very early times in highly transient heat transfer processes. In such situations, a hyperbolic equation model for heat conduction based on the modified Fourier law is introduced because the wave nature of heat propagation becomes dominant. The Fourier model and the hyperbolic model for heat conduction are analyzed by using the Green's function technique together with the integral transform. Analytical expressions for the heat flux and temperature distributions in a finite slab subjected to a periodic surface heating at one of its surfaces are presented and the results obtained from each model are compared with each other. The thermal wave implied b the hyperbolic model is shown to travel through a medium and to reflect back toward the origin at the other insulated surface. On the other hand, the heat by the Fourier model propagates at an infinite speed instantaneously after a thermal disturbance is felt throughout the medium.

  • PDF

Kinetics on the Microwave Carbonization of Rice Chaff (왕겨의 마이크로파 탄화속도)

  • Kim, Ji Hyun;Ryu, Seung Kon;Kim, Dong Kook
    • Korean Chemical Engineering Research
    • /
    • v.43 no.6
    • /
    • pp.683-690
    • /
    • 2005
  • The microwave carbonization of rice chaff was performed, and their kinetics were compared to those of conventional thermal carbonization. Thermal carbonization was carried out at $300-600^{\circ}C$ for 30 minutes. The weight loss and C/H mole ratio remarkably increased as increase of temperature, while there was no carbonization by microwave dielectric heating in spite of increasing incident power and irradiation time. However, microwave carbonization was successfully performed by addition of 6 wt% of thermal carbonized rice chaff, it's C/H mole ratio is larger than 3.0, as a catalytic initiator to uncarbonized rice chaff, and the kinetics was depended on the incident power and irradiation time, resulting in the coincide with thermal carbonization to the Arrhenius equation. The activation energy of microwave carbonization was quite low as compared to that of thermal carbonization, while the kinetic constant was large. This is due to the internal volumetric heating characteristics of carbonized rice chaff by microwave. The effect of ash, and C/H mole ratio and amount of carbonized rice chaff were investigated on microwave carbonization.

Comparison Study of Germination and Cooking Rate of Several Soybean Varieties (콩 품종에 따른 발아속도와 익힘속도의 비교)

  • Kim, Dong-Hee;Choi, Hee-Sook;Kim, Woo-Jung
    • Korean Journal of Food Science and Technology
    • /
    • v.22 no.1
    • /
    • pp.94-98
    • /
    • 1990
  • Seven varieties of soybeans (Paldal, Danyeob, Jangbaek, Baegun, Jangyeobkong and 2 cultivars of Local 1 and Local 2) were investigated to compare the germination properties and cooking rate. The growth rate of soybean sprout roots was slower for larger size of soybeans. A 100% of germination was obtained for Danyeobkong and Paldalkong. Local 1 and Local 2 were lowest, 47% and 31%, respectively in germination ratio. The hardness of cooked soybeans measured by the maximum cutting force of cotyledon showed that Local 2 was softer and Danyeobkong was harder than other varieties.

  • PDF