• 제목/요약/키워드: Water vapor effect

검색결과 356건 처리시간 0.06초

수직원관형 흡수기의 흡수과정에 미치는 비흡수가스의 영향 (Effect of a non-absorbable gag on the absorption process in a vortical tube absorber)

  • 허기준;정은수;정시영
    • 설비공학논문집
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    • 제10권4호
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    • pp.456-465
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    • 1998
  • Effect of a non-absorbable gas on the absorption process in a vertical tube absorber was investigated numerically. The water vapor mined with air as the non-absorbable gas is absorbed into LiBr/water solution film. The flow is assumed to be laminar and fully developed in both liquid and gas phases. The diffusion and energy equations were solved in both phases to give the temperature and concentrations, from which heat and mass fluxes were determined. It was shown that the local absorption rate decreases as the mass fraction of air in water vapor increases. The vapor pressure of water at the liquid-vapor interface reduces significantly since the non-absorbable gas is accumulated near the interface. The effect of non-absorbable gases on absorption rate becomes larger as the mass flow rate of the vapor decreases. For small amount of non-absorbable gases the total absorption rate of water vapor increases as the mass flow rate of the vapor decreases. Total absorption rate increases as the mass flow rate of the vapor increases for large concentration of non-absorbables at the inlet of an absorber.

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Kinetics of water vapor adsorption by vacuum-dried jujube powder

  • Lee, Jun Ho;Zuo, Li
    • 한국식품저장유통학회지
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    • 제24권4호
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    • pp.505-509
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    • 2017
  • Water vapor adsorption kinetics of vacuum-dried jujube powder were investigated in temperature and relative humidity ranges of 10 to $40^{\circ}C$ and 32 to 75%, respectively. Water vapor was initially adsorbed rapidly and then reached equilibrium condition slowly. Reaction rate constant for water vapor adsorption of vacuum-dried jujube powder increased with an increase in temperature. The temperature dependency of water activity followed the Clausius-Clapeyron equation. The net isosteric heat of sorption increased with an increase in water activity. Good straight lines were obtained with plotting of $1/(m-m_0)$ vs. 1/t. It was found that water vapor adsorption kinetics of vacuum-dried jujube powder was accurately described by a simple empirical model, and temperature dependency of the reaction rate constant followed the Arrhenius-type equation. The activation energy ranged from 50.90 to 56.00 kJ/mol depending on relative humidity. Arrhenius kinetic parameters ($E_a$ and $k_0$) for water vapor adsorption by vacuum-dried jujube powder showed an effect between the parameters with the isokinetic temperature of 302.51 K. The information on water vapor adsorption kinetics of vacuum-dried jujube powder can be used to establish the optimum condition for storage and processing of jujube.

직물 구조인자와 표면 가공특성이 스포츠 의류용 투습직물의 발수/방수/투습특성에 미치는 영향 (Effect of Fabric Structural Parameters and Surface Finishing Characteristics to Water Repellency/Proofing/Vapor Permeability of Breathable Fabrics for Sportswear Clothing)

  • 김현아
    • 한국의류산업학회지
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    • 제22권1호
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    • pp.112-118
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    • 2020
  • This paper examined the water repellency, water proofing and water vapor permeability of twelve types of woven fabrics for sports wear clothing. Their physical properties were compared and discussed with the fabric structural parameters and surface finishing effect. A water repellent property of 100% was obtained in the coated or laminated water repellent finished fabrics; in addition, cotton/nylon breathable composite fabrics treated with a laminated finishing and with low fabric density showed a 90% water repellency. Water proofing fabric above 6,000 mm H2O hydraulic pressure was achieved by coated or laminated finishing; however, high density fabric or medium-level coated fabrics exhibited 100% water repellent and low water proofing characteristics. Superior water vapor permeability characteristics with good water repellency and proofing properties were achieved at the 2.5 layered low density and with 0.7 - 0.9 cover factor nylon fabrics treated with hydrophilic laminated finishing. The regression analysis for examining the effects of fabric structural parameters and surface finishing such as coating and laminating to the water vapor permeability exhibited a high determination coefficient of fabric structural parameters of 63.5%; in addition,, main factors among fabric structural parameters appeared to be cover factor and fabric thickness per weight. Coating and Laminating factors exhibited determination coefficient of water vapor permeability parameters of 36.5%.

코일형 흡수기에서 증기 유동 방향이 유하액막 열전달에 미치는 영향 (제1부: 물을 이용한 실험) (Effect of Vapor Flow Direction on Falling Film Heat Transfer in a Coiled Tube Absorber (Part 1: Experiments with Pure Water))

  • 박경진;권경민;정시영;김병주
    • 설비공학논문집
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    • 제13권8호
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    • pp.720-729
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    • 2001
  • The effect of vapor flow direction on falling film heat transfer was experimentally investigated by using water. Parallel flow (both water and vapor downwards) showed higher heat exchange performance than counterflow(downward water and upward vapor). The difference became significant as the vapor flow rate was increased. It is supposed that the uprising vapor disturbs the solution film flow and heat transfer is reduced by uneven distribution or detachment of water film.

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EFFECTS OF WATERY VAPOR CONCENTRATION ON DROPLET EVAPORATION IN HOT ENVIRONMENT

  • Lee, M.J.;Kim, Y.W.;Ha, J.Y.;Chung, S.S.
    • International Journal of Automotive Technology
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    • 제2권3호
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    • pp.109-115
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    • 2001
  • A study has been conducted to clarify the effect of watery vapor concentration in hot ambient on droplet evaporation. Droplets of water, ethanol, n-hexadecaneand n-heptane were used in this experimental study. Ambient conditions are fixed at 470 K in temperature, 0.1 MPa in pressure and 2 m/s in velocity of ambient air. Watery vapor concentration was changed 0%~40% by 10% by add water to air. To obtain the time histories of droplet diameter after exposed in ambient, a suspended droplet in hot and humid ambient stream was synchronized with a back flash light, and enlarged droplet images were taken by a CCD camera. The evaporation rate constant of water droplet decreases slightly with the vapor concentration because diffusion velocity reduction of droplet vapor occurs on the surface. The values of ethanol and n-heptane droplet actively increase by effect that water from condensation of vapor flows into the droplet. The evaporation rate constant of n-hexadecane which has higher boiling point than water increases within around 30% of the concentration.

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섬유의 종류와 조합에 따른 직물의 수분전달 특성에 관한 연구 (A Study on the Effect of Fiber Type on the Water Vapor Transport Properties)

  • 나미희;김은애
    • 한국의류학회지
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    • 제14권3호
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    • pp.229-240
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    • 1990
  • The purpose of this study was to investigate the effect of hydrophilicity of the fiber on the water vapor transport properties of the fabric by using double layered fabrics of natural and synthetic fibers such as cotton, wool, nylon, dacron, orlon and polypropylene. Wickability and absorption rate were measured to determine the absorbancy of the fabrics. Dynamic and steady state water vapor transport properties were measured by cobaltous chloride method and evaporation method, respectively. Absorption was in the order of orlon> cotton > wool > nylon > polypropylene > dacron. Dynamic surface wetness of synthetic fabrics were faster than that of natural fabrics. For the double layered fabrics, higher water vapor transport was resulted when the natural fabric was exposed to lower vapor pressure and synthetic fabric was exposed to higher vapor pressure than when the fabrics were layered the other way around. Opposite result was obtained for orlon, which suggested that when the fabric of high absorbancy is exposed to the environment and lower absorbancy is to the skin, higher water vapor transpont could be resulted.

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Water - Assisted Efficient Growth of Multi-walled Carbon Nanotubes by Thermal Chemical Vapor Deposition

  • Choi, In-Sung;Jeon, Hong-Jun;Kim, Young-Rae;Lee, Nae-Sung
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2009년도 하계학술대회 논문집
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    • pp.418-418
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    • 2009
  • Vertically aligned arrays of multi-walled carbon nanotube (MWCNT) on layered Si substrates have been synthesized by water-assisted thermal chemical vapor deposition (CVD). We studied changes in growth by parameters of growth temperature, growth time, rates of gas and annealing time of catalyst. Also, We grew CNTs by adding a little amount of water vapor to enhance the growth of CNTs. $H_2$, Ar, and $C_2H_2$ were used as carrier gas and feedstock, respectively. Before growth, Fe served as catalyst, underneath which AI were coated as an underlayer and a diffusion barrier, respectively, on the Si substrate. The water vapor had a greater effect on the growth of CNTs on a smaller thickness of catalyst. When the water vapor was introduced, the growth of CNTs was enhanced than without water. CNTs grew 1.29 mm for 10 min long by adding the water vapor, while CNTs were 0.73 mm long without water vapor for the same period of time. CNTs grew up to 1.97 mm for 30 min prior to growth termination under adding water vapor. As-grown CNTs were characterized by using scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and Raman spectroscopy.

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Layered System의 아웃도어 의류에의 적용 - 수분전달 특성을 중심으로 - (Application of Layered System to the Outdoor Clothing - Through Water Vapor Permeability -)

  • 오애경
    • 한국의류산업학회지
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    • 제8권6호
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    • pp.709-712
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    • 2006
  • The aim of this study is to find out comfortable combinations of layered system for outdoor activities through water vapor permeability. Layering fabrics is an effective way of controlling water transport properties in fabric systems for outdoor activities and analysis of these systems may be useful for designing comfortable clothing. Seven fabrics were chosen for the experiments: two fabrics for base layer, two for the middle layer and three for the shell layer. A total of 12 different layered systems, which are all possible combinations were established using selected fabrics. The water vapor permeability was measured using JIS L1099 under isothermal and non-isothermal conditions. It was found that layered system was working together as a whole having influence on each layer, though every layer offers varying degree of water vapor permeability. Furthermore, it was also found that an optimal combination of the three layered system does exist although the combination may differ according to the ways. The shell layer is the greatest effect of water vapor permeability under isothermal and non-isothermal conditions within layered system.

부직포 충전재의 구조적 특성이 수분전달 특성에 미치는 영향-단층구조와 이층구조 부직포의 비교- (The Effect of Geometrical Structure on the Moisture Transport Properties of Nonwoven Batting Materials)

  • 김희숙;나미희
    • 한국의류학회지
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    • 제24권6호
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    • pp.810-818
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    • 2000
  • The purpose of this study was to analyze the effect of geometrical structure on the moisture transport properties of nonwoven batting materials. Two types of nonwovens were used such as single and double layered nonwovens. Steady and dynamic state water vapor transport properties were measured by absorption, evaporation and cobaltous chloride method respectively. The results of this study were as follows: 1) Geometrical structure affected water vapor evaporation, but there were no differences between single and double layered nonwovens in moisture absorption. Thickness and air permeability were influencing factor on water vapor transport rate. 2) Directionality of double layered nonwoven was observed both in steady and dynamic state moisture transport. There were differences between upper and lower layer of double layered nonwoven both in moisture absorption rate and color change by cobaltous chloride method. 3) In dynamic state of water vapor transport rate, single layered nonwoven reached more rapidly at the established relative humidity. It was confirmed that geometrical structure affected water vapor evaporation and hydrophilicity of fiber affected moisture absorption because there were much more water vapor transport rate by evaporation than absorption within the same period of time.

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Kinetics of Water Vapor Adsorption by Chitosan-based Nanocomposite Films

  • Seog, Eun-Ju;Zuo, Li;Lee, Jun-Ho;Rhim, Jong-Whan
    • Food Science and Biotechnology
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    • 제17권2호
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    • pp.330-335
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    • 2008
  • Water vapor adsorption kinetics of 3 different types of chitosan-based films, i.e., control chitosan, chitosan/montmorillionite (Na-MMT), and chitosan/silver-zeolite (Ag-Ion) nanocomposite films, were investigated at temperature range of $10-40^{\circ}C$. In all the films, water vapor is initially adsorbed rapidly and then it comes slowly to reach equilibrium condition. Reasonably good straight lines were obtained with plotting of 1/($m-m_0$) vs. l/t. It was found that water vapor adsorption kinetics of chitosan-based films was accurately described by a simple empirical model and the rate constant of the model followed temperature dependence according to Arrhenius equation. Arrhenius kinetic parameters ($E_a$ and $k_o$) for water vapor adsorption by chitosan-based films showed a kinetic compensation effect between the parameters with the isokinetic temperature of 315.52 K.