• Title/Summary/Keyword: Enthalpy Control

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Effect of Hydrothermal and Enzymatic Treatments on the Physicochemical Properties of Waxy Maize Flour (열수 및 효소 처리에 의한 찰옥수수가루의 물리화학적 특성)

  • Lee, Dong-Jin;Choi, So-Mang;Lim, Seung-Taik
    • Korean Journal of Food Science and Technology
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    • v.48 no.2
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    • pp.165-171
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    • 2016
  • Physicochemical properties of waxy maize flours prepared by hydrothermal and enzymatic treatments were evaluated. Waxy maize flours were hydrothermally treated using heat-moisture treatment (HMT) and annealing (ANN) and enzymatically treated using commercial enzymes (cellulase, proteinase, and pectinase). The HMT-modified waxy maize flours had low water absorption index (WAI), melting enthalpy, viscosity, and crystallinity. However, ANN-modified and enzymatically modified waxy maize flours had high WAI, melting enthalpy, and viscosity. X-ray diffraction analysis of ANN-modified and enzymatically modified waxy maize flours revealed a typical A-type pattern and displayed sharper crystalline peaks than those observed for the control groups (native waxy maize flours). In contrast, the crystallinity of HMT-modified waxy maize flours were decreased by hydrothermal treatment.

Effect of Certain Additives on Bread-Making Quality of Wheat-Purple Sweet Potato Flours (밀 및 자색고구마 가루의 제빵성에 대한 첨가제의 영향)

  • 김선영;유정희
    • Korean journal of food and cookery science
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    • v.13 no.4
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    • pp.492-499
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    • 1997
  • The effect of oxidants, gluten and gums on breadmaking quality of wheat-purple sweet potato(Ipomoea batatas) composite flour were studied. Alveograph tests of doughs showed that all additives increased the P, L and W values. Of these additives, L-Ascorbic acid, gluten, carboxy methyl cellulose have a significant effect on alveogram indexes. SEM showed that the dough added with additives changed some what in appearance when compared with the control. When oxidants was added, the doughs discontinuous gluten film were observed. No significant differences ,were evident in bread crumb color among the additives. And textural characteristics of bread crumb were influened by adding additives. Breads containing additives showed an increase in max weight, strength and hardness and a decrease in springness and cohesiveness. Average enthalpy values for all bread crumb after 7days increased with storage time. However, addition of additives decrease the rate of staling slightly more than that of the control. Addition of L-Ascorbic acid, L-Cystine, carboxy methyl cellulose and hydroxy propyl methyl cellulose increased the loaf volume significantly, and with except potassium bromate bread scores were acceptable.

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A Design Process for Reduction of Pressure Drop of Air-cooled Condenser for Waste Heat Recovery System (폐열 회수 시스템용 공랭식 응축기의 압력 손실 저감 설계)

  • Bae, Sukjung;Heo, Hyungseok;Park, Jeongsang;Lee, Hongyeol;Kim, Charnjung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.21 no.6
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    • pp.81-91
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    • 2013
  • A novel design process of a parallel multi-flow type air-cooled condenser of a dual-loop waste heat recovery system with Rankine steam cycles for improving the fuel efficiency of gasoline automobiles has been investigated focusing on reduction of the pressure drop inside the micro-tubes. The low temperature condenser plays a role to dissipate heat from the system by condensing the low temperature loop working fluid sufficiently. However, the refrigerant has low evaporation temperature enough to recover the waste from engine coolant of about $100^{\circ}C$ but has small saturation enthalpy so that excessive mass flow rate of the LT working fluid, e.g., over 150 g/s, causes enormously large pressure drop of the working fluid to maintain the heat dissipation performance of more than 20 kW. This paper has dealt with the scheme to design the low temperature condenser that has reduced pressure drop while ensuring the required thermal performance. The number of pass, the arrangement of the tubes of each pass, and the positions of the inlet and outlet ports on the header are most critical parameters affecting the flow uniformity through all the tubes of the condenser. For the purpose of the performance predictions and the parametric study for the LT condenser, we have developed a 1-dimensional user-friendly performance prediction program that calculates feasibly the phase change of the working fluid in the tubes. An example is presented through the proposed design process and compared with an experiment.

Analysis of Heat Exchanging Performance of Heat Recovering Device Attached to Exhaust Gas Duct (열회수장치에 의한 열회수성능 분석)

  • 서원명;윤용철;강종국
    • Journal of Bio-Environment Control
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    • v.9 no.4
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    • pp.212-222
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    • 2000
  • This study was performed to investigate the performance of heat recovery device attached to exhaust gas flue connected to combustion chamber of greenhouse heating system. The experimental heat recovery system is mainly consisted of LPG combustion chamber and two heat recovery units; unit-A is attached directly to the exhaust gas flue, and unit-B is connected with unit-A. Heat recovery performance was evaluated by estimating total energy amounts by using enthalpy difference between two measurement points together with mass flow rate of gas and/or air passing through each heat recovery unit depending on 5 different flow rates controlled by voltage meter. The results of this experimental study, such as heat exchange behavior of supply air tubes and exhaust air passages crossing the tubes, pressure drop between inlet and outlet, heat recovery performance of exchange unit, etc., will be used as fundamental data for designing optimum heat recovery device to be used for fuel saving purpose by reducing heat loss amounts mostly wasted outside of greenhouse through flue.

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Non-thermal Plasma for Air Pollution Control Technology (저온 플라즈마 이용 대기환경설비기술)

  • Song, Young-Hoon
    • Applied Chemistry for Engineering
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    • v.17 no.1
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    • pp.1-11
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    • 2006
  • Non-thermal plasma technology for air pollution control, which are NOx, SOx, VOCs, soot, etc., is reviewed. In the early parts of the paper, generation of non-thermal plasma and plasma chemical process are introduced to provide an appropriate plasma condition (electron energy density) for treating air pollutions. Recent results on numerical simulation, optical diagnostics, and gas treatment are provided to characterize an optimal design of plasma generation and plasma chemical process. These data are also helpful to understand unique features of non-thermal plasma process that is achieved with relatively low temperature conditions, i.e. low enthalpy conditions of the treated gas molecules. In the later parts of the paper, several examples of recently developed non-thermal plasma techniques are illustrated, in which technical and economical assessments of the present techniques are provided.

Effects of Catalyst Dispersion for Reaction Energy Control on Eco-AZ91 MgH2 (Eco-AZ91 MgH2의 반응열 제어에 미치는 촉매 분산 효과)

  • SOOSUN LEE;SONG SEOK;TAE-WHAN HONG
    • Transactions of the Korean hydrogen and new energy society
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    • v.34 no.6
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    • pp.631-640
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    • 2023
  • This study selected Eco-AZ91 MgH2, which shows high enthalpy as a material for this purpose, as the basic material, and analyzed the change in characteristics by synthesizing TiNi as a catalyst to control the thermodynamic behavior of MgH2. In addition, the catalyst dispersion technology using graphene oxide (GO) was studied to improve the high-temperature aggregation phenomenon of Ni catalyst and to secure a source technology that can properly disperse the catalyst. XRD, SEM, and BET analysis were conducted to analyze the metallurgical properties of the material, and TGA and DSC analysis were conducted to analyze the dehydrogenation temperature and calorific value, and the correlation between MgH2, TiNi catalyst, and GO reforming catalyst was analyzed. As a result, the MgH2-5 wt% TiNi at GO composite could lower the dehydrogenation temperature to 478-492 K due to the reduction of the catalyst aggregation phenomenon and the increase in the reaction specific surface area, and an experimental result for the catalyst dispersion technology by GO could be ensured.

An Application of Optimum Heat Exchanger for the Grasp on Performance Characteristics of $NH_3$ Refrigeration System

  • Ha Ok Nam;Kwon Il Wook;Hong Suck Ju;Kim Jae Yeol;Lee Jong In;Jeon Sang Sin;Ha Kyung Soo;Lee Seung Jae;Park Chan Soo;Jeong Song Tae
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.14 no.2
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    • pp.69-74
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    • 2005
  • Since the use of CFC and HCFC refrigerants is to be restricted due to the depletion of ozone layer, this experiment applies the $NH_{3}$ gas to study the performance characteristics from the superheat control for improving the energy efficiency. The experiments are carried out for the condensing pressure of refrigeration system from 1500kPa to 1600kPa by 50kPa and for degree of superheat from $0^{circ}$ to $1^{circ}$ by $10^{circ}$ at each condensing pressure. As a result of experiment, 1) As degree of superheat increased, evaporating pressure of the compressor decreased so equilibrium temperature decreased. And specific volume of refrigerant vapors increased so refrigerant mass flow and heat load of the evaporator decreased. 2) An influence of change of condensing pressure on heat load of the evaporator was insignificant. 3) With the identical degree of superheat, change of compressed temperature was insignificant according to each condensing pressure, so there was little change in enthalpy.4) when the degree of superheat is $0^{circ}$C at each condensing pressure, the refrigeration system has the hi띤est performance.

Three Dimensional Thermal-Elastic Plastic Analysis of GMAW Considering the Melting of Weld Bead (비드의 용용상태를 고려한 가스메탈 아크용접의 3차원 열탄소성 변형 해석)

  • Jang-Hyun Lee;Jong-Gye Shin;Ji-Hoon Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.39 no.1
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    • pp.49-60
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    • 2002
  • Welding is essential in ship production since welding is very popular method for joining two or more metals. However, welding causes residual stress and distortion and these give a bad influence to the structure strength and assembly of ship blocks. Therefore, prediction and treatment of residual stress and distortion is a key to accuracy control in shipyard. In this paper, a computational procedure, based on thermal-elastic-plastic 3-dimensional FEA, has been suggested to simulate butt and fillet welding process. In the simulation process, temperature distribution at each time step is obtained by heat transfer analysis and then thermal deformation analysis is done with obtained temperature distributions to find the residual stress and distortion. In heat transfer analysis, enthalpy method is used to realize phase change at melting temperature. Also element birth and death method is used to simulate adding of weld metal in both heat transfer analysis and thermal elastic plastic analysis. The proposed procedure is verified by related researches and the results show good agreement with those of related researches.

Study on PEM-Fuel-Cell Humidification System Consisting of Membrane Humidifier and Exhaust Air Recirculation Units (막가습기와 공기극 재순환을 사용한 고분자 전해질 연료전지의 가습특성 해석)

  • Byun, Su-Young;Kim, Beom-Jun;Kim, Min-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.4
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    • pp.337-344
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    • 2011
  • The humidification of reactant gases is crucial for efficiently operating PEM (polymer electrolyte membrane) fuel cell systems and for improving the durability of these systems. The recycle of the energy and water vapor of exhaust gas improves the system performance especially in the case of automotive application. The available humidification methods are steam injection, nozzle spray, humidification by enthalpy wheel, membrane humidifier, etc. However, these methods do not satisfy certain requirements such as compact design, efficient operation and control. In this study, a hybrid humidification system consisting of a membrane humidifier and exhaust-air recirculation units was developed and the humidification performance of this hybrid humidifier was analyzed. Finally, a new practical method for optimal design of PEM-fuel-cell humidification system is proposed.

Effects of Al-doping on IZO Thin Film for Transparent TFT

  • Bang, J.H.;Jung, J.H.;Song, P.K.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.207-207
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    • 2011
  • Amorphous transparent oxide semiconductors (a-TOS) have been widely studied for many optoelectronic devices such as AM-OLED (active-matrix organic light emitting diodes). Recently, Nomura et al. demonstrated high performance amorphous IGZO (In-Ga-Zn-O) TFTs.1 Despite the amorphous structure, due to the conduction band minimum (CBM) that made of spherically extended s-orbitals of the constituent metals, an a-IGZO TFT shows high mobility.2,3 But IGZO films contain high cost rare metals. Therefore, we need to investigate the alternatives. Because Aluminum has a high bond enthalpy with oxygen atom and Alumina has a high lattice energy, we try to replace Gallium with Aluminum that is high reserve low cost material. In this study, we focused on the electrical properties of IZO:Al thin films as a channel layer of TFTs. IZO:Al were deposited on unheated non-alkali glass substrates (5 cm ${\times}$ 5 cm) by magnetron co-sputtering system with two cathodes equipped with IZO target and Al target, respectively. The sintered ceramic IZO disc (3 inch ${\phi}$, 5 mm t) and metal Al target (3 inch ${\phi}$, 5 mm t) are used for deposition. The O2 gas was used as the reactive gas to control carrier concentration and mobility. Deposition was carried out under various sputtering conditions to investigate the effect of sputtering process on the characteristics of IZO:Al thin films. Correlation between sputtering factors and electronic properties of the film will be discussed in detail.

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