• Title, Summary, Keyword: Relative humidity

Search Result 2,338, Processing Time 0.04 seconds

Effect of Relative Humidity on the Breakthrough of Charcoal Tubes during Mixed Organic Vapor Sampling (혼합 유기용제 포집시 습도가 활성탄관의 파과에 미치는 영향)

  • Yang, Hyeok Syng;Kim, Hyunwook
    • Journal of Korean Society of Occupational and Environmental Hygiene
    • /
    • v.6 no.1
    • /
    • pp.125-137
    • /
    • 1996
  • This study was designed to investigate effects of relative humidity on the breakthrough of charcoal tubes at a fixed vapor concentration and sampling time during mixed organic vapor sampling. A vapor generator was used to generate three different concentrations of mixed organic vapor and a stainless steel chamber was fabricated and utilized to maintain three different percentages of relative humidity while maintaining a constant temperature. The results were as follows; 1. At high relative humidity, breakthrough of mixed organic vapor occurred quickly at low vapor concentration than at high vapor concentration because of the reduced adsorption volume of charcoal tube due to humidity. 2. Breakthrough by competitive adsorption of vapors onto charcoal tube was observed at first from n-hexane having the lowest boiling point and highest vapor pressure among the three organic vapors investigated, followed by TCE. No breakthrough was observed from toluene under all experimental conditions. 3. For n-hexane, breakthrough was observed after 2 hours of sampling and breakthrough rates were increased as relative humidity increased. For TCE, breakthrough was found after 3 hours of sampling and breakthrough rates by sampling time were increased as vapor concentration increased. 4. The adsorbed amount of mixed organic vapor at breakthrough was shown to have statistically significant correlations with sampling time, relative humidity, and vapor concentration in descending order of correlation. Relative humidity and sampling time for n-hexane and sampling time and concentration for TCE were both statistically significantly correlated. 5. Relative humidity was found to affect the amount of breakthrough of mixed organic vapor and n-hexane. Among three percentages of relative humidity investigated, the amount of breakthrough at 85 % relative humidity was significantly larger than those of at lower percentages of relative humidity. No statistically significant difference was found between 25 % and 55 % relative humidity. 6. The results of multiple regression analysis between breakthrough and relative humidity, vapor concentrations showed that the coefficient of determination of mixed organic vapor was 0.263 and those of n-hexane and TCE were 0.275 and 0.189, respectively. 7. Flow rates of sampling pumps used were found to be affected by relative humidity present. At 25 %, 55 %, and 85 % relative humidity, the relative errors of sampling pump were 1.4 %, 13.4 %, and 18.6 %, respectively. In conclusion, the results of this study showed that high relative humidity could reduce the adsorption volume of charcoal tubes and subsequently increase breakthrough rates. Therefore, to prevent breakthrough when sampling mixed organic vapors, it is suggested that either sampling volume be reduced on the flow rate be lowered so as to minimize breakthrough of the most volatile organic vapor in the mixture. In addition, since the flow rates of a sampling pump can be adversely affected by high relative humidity, it is recommended to use a constant flow mode pump when sampling in the highly humid environment.

  • PDF

Characteristics of fruit body of Neolentinus lepideus according to relative humidity (상대습도에 따른 잣버섯의 생육형태)

  • Jang, Myoung-Jun
    • Journal of Mushroom
    • /
    • v.12 no.4
    • /
    • pp.363-366
    • /
    • 2014
  • This study was focused on finding a relationship between fruit-body growth and relative humidity in Neolentinus lepideus cultivation. The higher the relative humidity, the moisture content of pileus and stipe were also tends to be increased. The day of formation of primordia and development of fruit body was shortest at the relative humidity 95%. The yield and commercial yield were higher in the relative humidity 95% than in the other treatment. Individual weight of fruit body was the highest at the relative humidity 75% and 85%. Crack indices of pileus was the strongest at the relative humidity 65%.

Changes in the Levels of Ergosterol and Methionine as Indicators of Lentinula edodes Quality According to the Relative Humidity During the Storage Period

  • Park, Youn-Jin;Cho, Yong-Koo;Kim, Chan-Young;Jang, Myoung-Jun
    • Journal of Environmental Science International
    • /
    • v.29 no.12
    • /
    • pp.1199-1204
    • /
    • 2020
  • Lentinula edodes mushrooms cultivated under different relative humidities were wrapped at 4℃ and the results of storage characteristics were investigated. Changes in water content of fruiting bodies during the storage period showed the highest water content in fruit bodies harvested from the treatment with the highest relative humidity. The luminosity of the fresh fruiting bodies showed no significant change during the storage period, and the redness was higher in the relative humidity 95% treatment than in the other treatments. According to this study, the relative humidity of the pileus was 65%, and the content of Ergosterol was 0.67 ± 15 g / L at relative humidity of 65%, 80% and 95%. In addition, amino acid analysis and Principal Component Analysis (PCA) confirmed that methionine was the main cause of changes in storage time and relative humidity.

Effects of relative humidity on the physical properties of PVA impregnated paper (상대습도의 변화가 PVA 함침처리지의 물성에 미치는 영향)

  • Kim, Tae-Young;Joung, Yang-Jin;Kim, Du-Ki;Heo, Yong-Dae;Sung, Yong-Joo
    • Journal of Korea Technical Association of The Pulp and Paper Industry
    • /
    • v.42 no.3
    • /
    • pp.37-42
    • /
    • 2010
  • The properties of paper are very susceptible to moisture content originated from relative humidity. This propensity of PVA impregnated paper was investigated in this study. Especially the hardening effect of borax treatment after PVA impregnation on the response of paper sample to the relative humidity was evaluated. When the moisture content was increased with the relative humidity, tensile stretch and tear resistance were increased while tensile strength and stiffness were decreased. A great increase in folding endurance of PVA impregnated paper sample was found at the higher relative humidity. The borax treatment could reduce the response of PVA impregated paper to the relative humidity.

Soft Sensor Development for Predicting the Relative Humidity of a Membrane Humidifier for PEM Fuel Cells (고분자 전해질 연료전지용 막가습기의 상대습도 추정을 위한 소프트센서 개발)

  • Han, In Su;Shin, Hyun Khil
    • Transactions of the Korean hydrogen and new energy society
    • /
    • v.25 no.5
    • /
    • pp.491-499
    • /
    • 2014
  • It is important to accurately measure and control the relative humidity of humidified gas entering a PEM (polymer electrolyte membrane) fuel cell stack because the level of humidification strongly affects the performance and durability of the stack. Humidity measurement devices can be used to directly measure the relative humidity, but they cost much to be equipped and occupy spaces in a fuel cell system. We present soft sensors for predicting the relative humidity without actual humidity measuring devices. By combining FIR (finite impulse response) model with PLS (partial least square) and SVM (support vector machine) regression models, DPLS (dynamic PLS) and DSVM (dynamic SVM) soft sensors were developed to correctly estimate the relative humidity of humidified gases exiting a planar-type membrane humidifier. The DSVM soft sensor showed a better prediction performance than the DPLS one because it is able to capture nonlinear correlations between the relative humidity and the input data of the soft sensors. Without actual humidity sensors, the soft sensors presented in this work can be used to monitor and control the humidity in operation of PEM fuel cell systems.

The Effects of Pressure, Wind Velocity, and Diameter of Wet Element on the Measurement of Relative Humidity by a Psychrometer (압력, 풍속 및 습구온도계의 크기가 건습구습도계를 이용한 상대습도 측정에 미치는 영향)

  • Chi, D.S.;Kim, S.T.;Park, C.B.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.2 no.2
    • /
    • pp.137-141
    • /
    • 1990
  • When the relative humidity is measured with an aspirated psychrometer, three factors, which affect the measurement of relative humidity, are atmospheric pressure, the size of wet element and the wind velocity. This paper investigated the effects of the above three factors, and the computer code was developed in order to enhance the accuracy of the relative humidity measurement. As results, it is found that the relative humidity decreases by 6%RH with increasing atmospheric pressure from 650 mbar to 1100 mbar. It is found that the relative humidity drops down when the size of the wet element increases, though the effect of the size of the wet element is not significant. Finally, relative humidity increases with the increasing wind velocity. The difference between the psychrometic table in the present KS and the present results is about 2%RH maximum. As a conclusion, the three factors mentioned above should be considered in order to secure accurate measurement of relative humidity.

  • PDF

A Study on the Change of Humidity by City Size in South Korea (한국의 도시 규모별 습도 변화에 관한 연구)

  • Ko, Myungchan;Lee, Seungho
    • Journal of the Korean Geographical Society
    • /
    • v.48 no.1
    • /
    • pp.19-36
    • /
    • 2013
  • This study aimed to investigate the change of humidity by city size in South Korea. Using daily mean relative humidity and water vapor pressure during the period of 1954~2011 for 14 weather stations in South Korea, the change of humidity by city size was analyzed. The change of relative humidity had a continuous decreasing trend for the period of 1954~2011. The decreasing trend in large city was bigger than these of rural one. The seasonal relative humidity was significantly changed in spring and winter. The change of water vapor pressure was rarely changed significance of the results by city size. It was not shown the result to constant trend by city size. There was a negative correlation between relative humidity and mean temperature. And change of relative humidity was correlated with city size. Moreover, there was not correlation between relative humidity and water vapor pressure by city size. The decreasing trend of relative humidity was similar to increasing trend of temperature by urbanization. However, there was not shown significant result of water vapor pressure.

  • PDF

Effect of relative humidity in swine house on pathogenesis of swine pleuropneumonia (돈사의 상대습도가 돼지흉막폐렴의 병인에 미치는 영향)

  • Jeong, Hyun-kyu;Han, Jeong-hee;Kim, Jae-hoon
    • Korean Journal of Veterinary Research
    • /
    • v.36 no.1
    • /
    • pp.131-142
    • /
    • 1996
  • The effect of relative humidity in swine house on swin pleuropneumonia was examined in piglets experimentally infected with Actinobacillus pleuropneumoniae serotype 5. A total of 20 piglet were grown under 30~40%, 41~50%, 51~64% and 65~80% relative humidity chambers after intratracheal inoculation of A pleuropneumoniae. Characteristic fibrinous pleuropneumonia was observed in the pigs grown at the low relative humidity groups. The detailed results were as follows : 1. Growth performance and environment conditions were lower than high relative humidity groups. 2. Characteristic histopathological findings were fibrinous pleuritis and pneumonia accompanied congestion, hemorrhage, thrombosis and edematous change. 3. Antigenic distribution of inoculated bacterium was found mainly in alveolar macrophages or accumulated foci of macrophages adjacent to necrotic area. 4. Characteristic electron microscopic findings were proliferation of type II pneumocyte with increased lamella bodies and activated alveolar macrophages with pseudopods and widening of interstitium.

  • PDF

Effects of Curing Temperature on Autogenous Shrinkage, Relative Humidity, Pore Structure of Cement Pastes

  • Park Ki-Bong
    • Journal of the Korea Concrete Institute
    • /
    • v.17 no.5
    • /
    • pp.853-856
    • /
    • 2005
  • A low water/cement ratio leads to autogenous shrinkage of cement paste at an early age. This autogenous shrinkage is related to the change of relative humidity in the pore structure that is formed during the hydration process. The relationship between autogenous shrinkage and relative humidity change are relatively well defined today, but the effects of temperature on autogenous shrinkage, relative humidity, and pore structures have been studied less systematically. This study focused on correlating alterations of these properties of cement paste hydrated at constant temperatures of 20, 40, and $60^{\circ}C$. The test results clearly indicate that increasing curing temperature resulted in increased porosity, particularly for pores between 5 to 50 nm as measured by MIP, and increased autogenous shrinkages, as a consequence of a reduction of relative humidity at early ages.

Effects of Relative Humidity on the Evaporator Pressure Drop (증발기의 압력강하에 대한 상대습도의 영향)

  • 김창덕;강신형;박일환;이진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.16 no.5
    • /
    • pp.397-407
    • /
    • 2004
  • It is well known that some key parameters, such as evaporating temperature, refrigerant mass flow rate, face velocity and inlet air temperature, have significant influence on the evaporator performance. However performance studies related to a humid environment have been very scarce. It is demonstrated that the refrigerant mass flow rate, heat flux, water condensing rate and air outlet temperature of the evaporator significantly increase with air inlet relative humidity. As the air inlet relative humidity increases, the latent and total heat transfer rates increase, but the sensible heat transfer rate decreases. The purpose of this study is to provide experimental data on the effect of air inlet relative humidity on the air and refrigerant side pressure drop characteristics for a slit fin-tube heat exchanger. Experiments were carried out under the conditions of inlet refrigerant saturation temperature of 7 $^{\circ}C$ and mass flux varied from 150 to 250 kg/$m^2$s. The condition of air was dry bulb temperature of 27$^{\circ}C$, air Velocity Varied from 0.38 to 1.6 m/s. Experiments Showed that air Velocity decreased 8.7% on 50% of relative humidity 40% of that at degree of superheat of 5$^{\circ}C$, which resulted that pressure drop of air and refrigerant was decreased 20.8 and 8.3% for 50% of relative humidity as compared to 40%, respectively.