• 한국응용과학기술학회지
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• 제28권2호
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• pp.178-184
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• 2011

The analysis of reaction kinetics provided that the reaction order was the $1^{st}$ of triglyceride and the rate constant was 0.067 $min^{-1}$. The transesterification of camelina oil using 0.6 wt% mixed catalyst which consists of 40 v/v% of potassium hydroxide (1 wt%) and 60 v/v% of tetra methyl ammonium hydroxide (0.8 wt%), was carried out at $65^{\circ}C$ on the tubular reactor packed with static mixer. The conversion was shown to be 95.5% at the 6:1 molar ratio of methanol to oil, flow rate of feed of 3.0 mL/min and 24 of element of static mixer. The volume of washing water emitted by 0.6 wt% mixed catalyst was the half of the volume emitted by 1 wt% potassium hydroxide.

• 대한기계학회논문집B
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• 제32권8호
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• pp.629-635
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• 2008

Recently, microturbines have received attention as a small-scale distributed power generator. Since the exhaust gas carries all of the heat release, the microturbine CHP (combined heat and power) system is relatively compact and easy to maintain. Generating hot water or steam is usual method of heat recovery from the microturbine. In this work, a heat recovery unit producing hot water was installed at the exhaust side of a 30 kW class microturbine and its performance characteristics following microturbine power variation was investigated. Heat recovery performance has been compared for different operating conditions such as constant hot water temperature and constant water flow rate. In particular, the influence of water flow rate and hot water temperature on the recovered heat was analyzed.

• Journal of Mechanical Science and Technology
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• 제14권6호
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• pp.690-698
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• 2000

The laminar boundary layer flow and heat transfer of anisotropic fluids in the vicinity of a wedge have been examined with constant surface temperature. The similarity variables found by Falkner and Skan are employed to reduce the stream wise-dependence in the coupled nonlinear boundary layer equations. The numerical solutions are presented using the fourth-order Runge - Kutta method and the distribution of velocity, micro-rotation, shear and couple stresses and temperature across the boundary layer are plotted. These results are also compared with the corresponding flow problems for Newtonian fluid over wedges. It is found that for a constant wedge angle, the skin friction coefficient is lower for micropolar fluid, as compared to Newtonian fluid. For the case of the constant material parameter K, however, the magnitude of velocity for anisotropic fluid is greater than that of Newtonian fluid. The numerical results also show that for a constant wedge angle with a given Prandtl number, Pr = I, the effect of increasing values of K results in increasing thermal boundary layer thickness for anisotropic fluid, as compared with Newtonian fluid. For the case of the constant material parameter K, however, the heat transfer rate for anisotropic fluid is lower than that of Newtonian fluid.

• 한국지반공학회논문집
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• 제27권10호
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• pp.5-12
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• 2011

본 연구에서는 해안지역의 지반개량과 통시에 오염된 간극수를 정화하기 위한 방법으로 반응컬럼을 이용한 연직배수 공법의 반응컬럼 길이의 결정을 위하여 제강슬래그의 반응성을 평가하였다. 제강슬래그의 카드륨에 대한 반응성을 초기 농도와 pH의 변화에 따라 실험을 수행하였다. 반응시간에 따른 카드륨의 제거량을 유사이차 반응식을 이용해서 평형흡착량($q_e$)과 유사이차 반응상수($k_2$)를 통해 정량적으로 평가하였다. 필요 반응시간은 유사이차 반응모델에서 계산된 평형흡착량($q_e$)와과 유사이차 반응상수($k_2$)의 곱의 역수로 제안하였다. 필요 반응시간을 이용하여 반응컬럼의 길이를 결정할 수 있을 것으로 판단된다.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.201-204
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• 2002

The rates of the aminolysis of S-phenyl substituted-acetate series $(RC(=O)SC_6H_4Z$, with R=Me, Et, i-Pr, t-Bu and Bn) with benzylamines $(XC_6H_4CH_2NH_2)$ are not correlated simply with the Taft's polar $({\sigma}^{\ast})$ and/or steric effect constants $(E_s)$ of the substituents due to abnormally enhanced rate of the substrate with R=Et. Furthermore, the cross-interaction constant, ${\rho}x_z$ , is the largest with R=Et. These anomalous behaviors can only be explained by invoking the vicinal bond $({\sigma})$-antibond $({\sigma}^{\ast})$ charge transfer interaction between C-$C{\alpha}$ and C-S bonds. In the tetrahedral zwitterionic intermediate, $T^{\pm}$ , formed with R=Et the vicinal ${\sigma}_{c-c}-{\sigma}^{\ast}_{c-s}$ delocalization is the strongest with an optimum antiperiplanar arrangement and a narrow energy gap, ${\Delta}{\varepsilon}={\varepsilon}_{{\sigma}^{\ast}}-{\varepsilon}_{\sigma}$. Due to this charge transfer interaction, the stability of the intermediate increases (with the concomitant increase in the equilibrium constant K (= $k_a/k_{-a}$)) and also the leaving ability of the thiophenolate leaving group increases (and hence $k_b$ increases) so that the overall rate, $k_n\;=\;Kk_b$, is strongly enhanced. Theoretical support is provided by the natural bond orbital (NBO) analyses at the B3LYP/6-31+$G^{\ast}$ level. The anomaly exhibited by R=Et attests to the stepwise reaction mechanism in which the leaving group departure is rate limiting.

• 한국식품과학회지
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• 제14권4호
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• pp.342-349
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• 1982

송풍식건조과정(送風式乾燥過程) 중의 말쥐치육의 건조기구(乾操機構)와 수분활성(水分活性)과의 관계를 검토하기 위하여 $47.5^{\circ}C$에서 풍속과 공기의 상대습도를 달리하여 실험한 결과를 요약하면 다음과 같다. 전체 건조과정은 정속건조기(定速乾燥期)와 감속건조기(減速乾燥期)로 구분되었다. 정속건조기(定速乾燥期)는 건조표면(乾燥表面)이 수분활성(水分活性) 1.0을 유지하는한 계속되었으며, 온도와 상대습도가 일정할 때 정속건조속도(定速乾燥速度)는 공기의 속도(速度)의 제곱근에 비례하였다. 감속건조기(減速乾燥期)는 건조기구(乾操機構)가 서로 다른 제(第)1 및 제(第)2감속건조기(減速乾燥期)로 구분되었다. 제(第)1감속건조기(減速乾燥期)는 모세관 응축수의 건조표면(乾燥表面)으로의 이동이 불충분한 불포화표면건조기(不飽和表面乾燥期)였으며, 이 때의 건조속도(乾燥速度)는 공기의 온도가 일정할 때 상대습도에 크게 좌우되었다. 제(第)1감속건조기(減速乾燥期)와 제(第)2감속건조기(減速乾燥期)의 변환점에서 표면경화현상(表面硬化現象)이 시작되었다. 상대습도의 변화에 따라 제(第)2감속건조기(減速乾燥期)가 시작될 때의 수분활성(水分活性)과 수분함량(水分含量)은 각각 다른 값을 나타내었다. 제(第)2감속건조기(減速乾燥期)는 다시 건조기구(乾操機構)를 달리하는 두 개의 건조기(乾燥期)로 구분되었다. 제(第)2감속건조기(減速乾燥期)의 1단계는 말쥐치육 내부의 모세관 응축수가 건조표면(乾燥表面)으로 확산, 증발하여 건조가 진행되었으며, 이때의 수분의 확산계수는 $47.5^{\circ}C$에서 $2.89{\cdot}10^{-10}m^2/sec$였다. 표면경화현상(表面硬化現象)은 말쥐치육의 수분활성(水分活性)이 0.7에 이를때까지 계속되었다. 제(第)2감속건조기(減速乾燥期)의 2단계는 수분활성(水分活性) 0.45에서 시작되었다. 이 때의 건조는 말쥐치육 내부에 다분자층(多分子層)으로 흡착(吸着)한 결합수의 건조표면(乾燥表面)으로의 확산, 증발에 의하여 진행되었다. 흡착수분(吸着水分)의 분자층(分子層)의 수는 4였으며, $47.5^{\circ}C$에서의 확산계수는 $4.38{\cdot}10^{-11}m^2/sec$였다.

• Journal of the korean society of oceanography
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• 제31권3호
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• pp.117-122
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• 1996

Oxygen consumption by the Manila clam, Ruditapes philippinarum (Bivalvia: Veneridae) maintained in a culture tank for 7-10 weeks was measured with an automatic intermittent-flow-respirometer (AIFR). There was evidence for an endogenous tidal rhythm of 12.4 h in oxygen consumption, at irregular intervals of between about 7 and 18 hours during experiments of between 22 h 5 min and 70 h 32 min (duration) recording for fasting animals in constant darkness at constant temperatures in the absence of tidal rhythms.

• 한국응용과학기술학회지
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• 제9권2호
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• pp.141-148
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• 1992

Transesterification reactions (methyl methacrylate with diethanolamine, ethylene glycol with dimethylphthalate) were kinetically investigated in the presence of zinc compound catalysts at $120{\sim}170^{\circ}C$ The amount of reactants was measured by gas chromatography. and the reaction rates also measured from the amount of reaction products and reactants upon each catalyst. The transesterification reactions were carried out under the first order conditions respect to the concentration of reactants, respectively, The overall reaction order was 2nd. The apparent rate constant (k') was found to obey first kinetics with respect to the concentration of catalyst. It shows that according to an increase in basicity of anionic species the rate constant increase, and that a linear relationship exists between ln k and pKa in transesterification reaction of methyl methacrylate with diethanolamine.

• 한국응용과학기술학회지
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• 제27권1호
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• pp.6-13
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• 2010

Esterification reaction between succinic acid and 1,4-butanediol was kinetically investigated in the presence of nontoxic organometallic compound catalyst(ESCAT-100E) at $150-190^{\circ}C$. The reaction rates measured by the amount of distilled water from the reaction vessel. The Esterification reaction was carried out under the first order conditions respect to the concentration of reactants, respectively. The overall reaction order was 2nd. The linear relationship was shown between apparent reaction rate constant and reciprocal absolute temperature. By the Arrhenius plot the activation energy have been calculated as 376.13 kJ/mol under nontoxic organometallic compound catalyst and also apparent reaction rate constant, k' was found to obey first kinetics with respect to the concentration of catalyst.

• 대한화학회지
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• 제15권6호
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• pp.330-347
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• 1971

Catalytic effects of metallic salts on the combustion of diesel fuel oil have been studied. In the case of organometallic salt, the active species are the metallic oxides resulted from combustion of the salts. The oxides act only on the residual solid carbon produced from the fuel oil combustion. The catalytic activity can be explained with the semiconductor theory just as in the case of the gas phase reaction. The chemical rate constant of the combustion of carbon, the soot from diesel fuel oil, is found to be $k_c=1.1{\times}10^4\;exp$ (-16,600/T) below $800^{\circ}K$. By addition of metallic oxides, the rate constant increases remarkably. This work has substantiated the belief that the effect of the metallic salts on the fuel oil combustion can conveniently be studied by checking directly the effect of the corresponding metallic oxide on the soot carbon.