• Title, Summary, Keyword: Water absorption

Search Result 3,017, Processing Time 0.059 seconds

Study on Reliability of Water Absorption Diagnosis through Precise Water Absorption Test

  • Kim, Hee-Soo;Bae, Yong-Chae;Kim, Hee-Dong
    • Journal of Electrical Engineering and Technology
    • /
    • v.7 no.5
    • /
    • pp.772-777
    • /
    • 2012
  • Accidents caused by water absorption in water-cooled generator stator windings often occur all over the world. The absorption into the insulator of the coolant, which is used to cool down the heat generated by stator windings during operation, leads to the deterioration of dielectric strength, and insulation breakdown. An insulation breakdown may cause not only an enormous economic loss but also a very serious grid accident that would compromise stable supply of electric power. More than 50 % of domestic generators have been in operation for more than 15 years, and water absorption tests performed on 50 water-cooled generator stator windings during a five-year planned preventive maintenance period beginning in 2006 identified water absorption problems in 10 of them, all of which required repair. Because the existing water absorption test detects this problem by utilizing stochastic methods after measuring the capacitances at the final positions of insulation breakdown, its accuracy is limited. This study demonstrates that water absorption can be more accurately diagnosed by utilizing method along with a more precise one.

Capillary Water Absorption Properties of Steel Fiber Reinforced Coal Gangue Concrete under Freeze-Thaw Cycles

  • Qiu, Jisheng;Zheng, Juanjuan;Guan, Xiao;Pan, Du;Zhang, Chenghua
    • Korean Journal of Materials Research
    • /
    • v.27 no.8
    • /
    • pp.451-458
    • /
    • 2017
  • The service life of coal gangue concrete(CGC) strongly depends on the capillary water absorption, this water absorption is susceptible to freeze-thaw cycles. In this paper, the cumulative water absorption and sorptivity were obtained to study the effects of 0, 0.5, 1.0, and 1.5 % steel fiber volume fraction added on the water absorption of CGC. Sorptivity and freeze-thaw tests were conducted, and the capillary water absorption was evaluated by the rate of water absorption(sorptivity). Three prediction models for the initial sorptivity of steel fiber reinforced coal gangue concrete(SFRCGC) under freeze-thaw cycles were established to evaluate the capillary water absorption of SFRCGC. Results showed that, without freeze-thaw cycles, the water absorption of CGC decreased when steel fiber at 1.0 % volume fraction was added, however, the water absorption increased with the addition of 0.5 or 1.5 % steel fibers. Once the SFRCGC specimens were exposed to freeze-thaw cycles, the water absorption of SFRCGC significantly increased, and 1.0 % steel fiber in volume fraction added to CGC caused the lowest water absorption, except for the case of the sample without steel fibers added. The CGC with steel fiber at 1.0 % volume fraction performed better. The SFRCGC has a strong response to freeze-thaw cycles. Results also showed that the linear function prediction model is practical in the field of engineering because of its simple form and a relatively high precision. Although the polynomial prediction model presents the highest computation precision among the three models, the complicated form and too many coefficients make it impractical for engineering applications.

A Study on the Effects of Water Absorption on the Thermal Conductivity of Insulation Materials (수분 흡수가 단열재의 열전도계수에 미치는 영향에 관한 연구)

  • Yoo, Seong-Yeon;Kim, Tae-Ho
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.25 no.3
    • /
    • pp.119-125
    • /
    • 2013
  • IInsulation material is generally used for preventing heat loss from heat transport fluids, and water absorption severely reduces the insulation property. The purpose of this study is to evaluate the amount of water absorption supplied by the pouring method and spraying method, to investigate the effects of water absorption on the thermal conductivity of an insulation material, and modeling the relation between water absorption and thermal conductivity. E-glass, a kind of glass fiber, and HYPERLITE, mainly composed of pearlite, are selected, to compare hygroscopic and insulation properties. E-glass is found to have much higher water absorptivity, compared to HYPERLITE. The thermal conductivity of the water-absorbed E-glass is increased by more than 150%, compared to that of no absorption, while variation of the thermal conductivity of HYPERLITE with water absorption is insignificant. A three-stage model of water absorption for thermal conductivity is developed, and the modeling results are found to be in good agreement with the experimental data.

Effects of the Changes in Handsheet Structure on the Water Absorption and Moisture Absorption (수초지 구조변화에 따른 흡수·흡습 특성 변화 연구)

  • Sung, Yong Joo;Kim, Dong Sung;Lee, Ji Young
    • Journal of Korea Technical Association of The Pulp and Paper Industry
    • /
    • v.48 no.3
    • /
    • pp.30-36
    • /
    • 2016
  • This study was conducted to investigate the influence of the changes in handsheet structure by beating, wet pressing and the addition of wood flour spacer on the water absorption and the moisture absorption properties. The higher beating treatment of BKP resulted in the denser structure of handsheet samples, which leaded to the lower water and moisture absorption. The wet pressing showed the similar effects by reducing the bulk of handsheets. In case of the handsheet samples with similar bulk structure made of different beaten pulps, the severer beating treatment increased the water absorption and the moisture absorption. The addition of the wood flour spacer resulted in the higher bulk following the higher water and moisture adsorption. Since the water and the moisture absorption properties of paper products could greatly affect on not only the product quality but also the process runnability, the control of the water response of paper product has been considered as very important technology. The results of this study might be useful for control of water and moisture absorption properties of paper products.

Comparative Study on the Absorption of Water after Oral Administration of Various Sports Drinking Beverages to Rabbits (수종의 스포츠 음료를 토끼에 경구 투여한 후 수분 흡수에 대한 비교연구)

  • Kim, Chong-Kook;Lee, Beom-Jin
    • Journal of Pharmaceutical Investigation
    • /
    • v.25 no.1
    • /
    • pp.1-7
    • /
    • 1995
  • After oral administration of various drinking solutions, the initial absorption rate of water through gastrointestinal tract of the rabbits was evaluated using tritinated water $(^3H_2O)$ as a marker to develop the sports drinking beverage for Korean people. The polynomial curve fitting over 20 min was performed using computer program to obtain the initial absorption rate of water from the tangent line of the fitted equation because initial absorption rate of water was more critical compared to elimination rate during exercise. The amount of water absorbed was increased but a large variation was observed among testing preparations in a small study group $(2{\leq}n{\leq}6)$. The initial absorption rate of water from isotonic sports drinking beverages was statistically significant when compared to hypertonic cola but was not significant when compared to hypotonic solutions (potable water and barley water). In case of hypertonic sports dringking beverages (i.e. Takeda), initial absorption rate of water was not improved and efficient when compared to other isotonic sports dringking beverages. The initial absorption rate of water from prescribed isotonic sample solution containing electrolytes, carbohydrates, and vitamins was not statistically significant when compared to other isotonic drinking beverages but showed similar absorption profile. It was obvious that isotonic solutions simultaneously containing electrolytes, vitamins and carbohydrates (sugar and glucose) had a tendency to increase the initial absorption of water compared to hypotonic (potable water and barley water) and hypertonic preparations (orange juice and cola). Although statistical significance of initial absorption rate of water between isotonic sports drinking beverages and hypotonic potable and barley water was not observed, unlike the hypertonic solutions, isotonic sports drinking beverages may aid not only to replenish loss of water, electrolytes and other nutrients during the exercise but also to prevent dehydration and muscle fatigue, resulting in improved physical performance in an exhausted condition.

  • PDF

A Study on the Water Absorption Velocity of Sized Fabrics (푸새직물의 흡수속도에 관한 일연구)

  • 오화자
    • Journal of the Korean Home Economics Association
    • /
    • v.25 no.2
    • /
    • pp.31-38
    • /
    • 1987
  • This paper aims to examine the velocity of water absorption of cotton, hemp, and T/C fabrics sized by rice, wheat, potato, corn flour and pp.V.A.. Experimental variables such as the concentration of sizing agents, the moisture regain of unsized fabrics and the ironing temperature showed the following results. 1. When the fabrics were sized, the velocity of water absorption increased according to the order of corn, rice, potato, wheat flour and pp.V.A. for cotton fabrics, of corn, potato, rice, wheat flour and pp.V.A. for hemp fabrics, and of corn, wheat, rice, potato flour and pp.V.A. for T/C fabrics; corn flour showed the highest velocity of water absorption and pp.V.A. did the lowest among all the others mentioned above. 2. The higher fabric density, the higher velocity of water absorption. The finer the count of fabric yarn, the higher velocity of water absorption. 3. The material of sized fabrics most affected the velocity of water absorption than other factors of those. 4. To a certain extent, the higher the concentration of sizing agent, the higher the velocity of water absorption. 5. The fabrics with moisture regain of 20% before sizing showed the highest velocity of water absorption. 6. The ironing temperature after sizing fabrics mentioned below showed the highest velocity of water absorption; 180$^{\circ}C$ for cotton, 200$^{\circ}C$ for hemp, and 160$^{\circ}C$ for T/C fabrics.

  • PDF

A Study on the Diagnosis for Water Absorption of Generator Stator Windings (발전기 고정자 권선의 흡습 진단)

  • Bae Y.C.;Kim H.S.;Lee D.Y.
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • /
    • pp.297-298
    • /
    • 2006
  • Water leak for the water-cooled generator stator windings affects seriously the availability and the reliability of power plants. Generally, water absorption test is conducted in the power plant during outage in order to confirm if leak part is in the bars or not. In this paper, it is described that the capacitance of winding bars is measured by using the developed water absorption instrument system and the water absorption of winding bars is evaluated by using the stochastic methods. The good results by proposed diagnosis technique can be got. It is expected that the reliability of diagnosis for water absorption is increased if the proposed methods are applied to evaluate the water absorption of stator winding bars.

  • PDF

Analysis of Operation Parameters of Pilot-Scale Packed-Absorption System for Airborne Methyl Ethyl Ketone Control (공기 중 메틸에틸케톤 제어를 위한 Pilot-Scale 흡수 시스템의 운영인자 분석)

  • Jo, Wan-Kuen;Kim, Wang-Tae
    • Journal of Environmental Science International
    • /
    • v.20 no.4
    • /
    • pp.501-509
    • /
    • 2011
  • Unlike many laboratory-scale studies on absorption of organic compounds (VOCs), limited pilot-scale studies have been reported. Accordingly, the present study was carried out to examine operation parameters for the effective control of a hydrophilic VOC (methyl ethyl ketone, MEK) by applying a circular pilot-scale packed-absorption system (inside diameter 37 cm ${\times}$ height 167 cm). The absorption efficiencies of MEK were investigated for three major operation parameters: input concentration, water flow rate, and ratio of gas flow-rate to washing water amount (water-to-gas ratio). The experimental set-up comprised of the flow control system, generation system, recirculation system, packed-absorption system, and outlet system. For three MEK input concentrations (300, 350, and 750 ppm), absorption efficiencies approached near 95% and then, decreased gradually as the operation time increased, thereby suggesting a non-steady state condition. Under these conditions, higher absorption efficiencies were shown for lower input concentration conditions, which were consistent with those of laboratory-scale studies. However, a steady state condition occurred for two input concentration conditions (100 and 200 ppm), and the difference in absorption efficiencies between these two conditions were insignificant. As supported by an established gas-liquid absorption theory, a higher water flow rate exhibited a greater absorption efficiency. Moreover, as same with the laboratory-scale studies, the absorption efficiencies increased as water-to-gas ratios increased. Meanwhile, regardless of water flow rates or water-to-gas ratios, as the operation time of the absorption became longer, the pH of water increased, but the elevation extent was not substantial (maximum pH difference, 1.1).

Monitoring the water absorption in GFRE pipes via an electrical capacitance sensors

  • Altabey, Wael A.;Noori, Mohammad
    • Advances in aircraft and spacecraft science
    • /
    • v.5 no.4
    • /
    • pp.499-513
    • /
    • 2018
  • One of the major problems in glass fiber reinforced epoxy (GFRE) composite pipes is the durability under water absorption. This condition is generally recognized to cause degradations in strength and mechanical properties. Therefore, there is a need for an intelligent system for detecting the absorption rate and computing the mass of water absorption (M%) as a function of absorption time (t). The present work represents a new non-destructive evaluation (NDE) technique for detecting the water absorption rate by evaluating the dielectric properties of glass fiber and epoxy resin composite pipes subjected to internal hydrostatic pressure at room temperature. The variation in the dielectric signatures is employed to design an electrical capacitance sensor (ECS) with high sensitivity to detect such defects. ECS consists of twelve electrodes mounted on the outer surface of the pipe. Radius-electrode ratio is defined as the ratio of inner and outer radius of pipe. A finite element (FE) simulation model is developed to measure the capacitance values and node potential distribution of ECS electrodes on the basis of water absorption rate in the pipe material as a function of absorption time. The arrangements for positioning12-electrode sensor parameters such as capacitance, capacitance change and change rate of capacitance are analyzed by ANSYS and MATLAB to plot the mass of water absorption curve against absorption time (t). An analytical model based on a Fickian diffusion model is conducted to predict the saturation level of water absorption ($M_S$) from the obtained mass of water absorption curve. The FE results are in excellent agreement with the analytical results and experimental results available in the literature, thus, validating the accuracy and reliability of the proposed expert system.

Changes in the Water Absorption Properties of Pulp Mold manufactured with Oil Palm EFB by surface treatments (표면처리에 의한 오일팜 EFB 기반 펄프몰드의 흡수특성 변화)

  • Kim, Dong-Sung;Sung, Yong Joo;Kim, Chul-Hwan;Kim, Se-Bin
    • Journal of Korea Technical Association of The Pulp and Paper Industry
    • /
    • v.47 no.1
    • /
    • pp.75-83
    • /
    • 2015
  • The applicability of oil palm biomass, EFB(Empty Fruit Bunch) as raw materials for environmental friendly packaging material, pulp mold, was evaluated in this study. The changes in the water absorption properties of pulp mold by the addition of EFB and the surface treatments with PVA and AKD were analyzed by measuring the changes in the water absorption rate and the water contact angle. The each pulp mold sample was prepared by using laboratory wet pulp molder. And the water absorption rate of each samples were evaluated by measuring times for the absorption of a 0.1 ml water drop on the pulp mold sample surface. The addition of EFB to the pulp mold made of OCC resulted in the decrease of water absorption rate and the increase in the water contact angle. The surface treatments with PVA and AKD on the OCC pulp mold showed the significant reduction in the water absorption rate. However, in case of ONP pulp mold, the addition of EFB and the surface treatments with PVA and AKD showed no big changes in water absorption times. Those might be come from the finer surface structure of ONP pulp mold which were made of more finer and flexible fibers and more hydrophilic fibers. The results of this study showed the functional properties such as water absorption rate, could be controlled by the application of EFB and the treatments with AKD or PVA, especially in case of the OCC pulp mold.