• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.1
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• pp.125-137
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• 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.

• Journal of Mushroom
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• v.12 no.4
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• pp.363-366
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• 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%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.2
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• pp.137-141
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• 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.

• Journal of Environmental Science International
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• v.29 no.12
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• pp.1199-1204
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• 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.

• Journal of the Korea Safety Management & Science
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• v.24 no.4
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• pp.101-107
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• 2022

To test a flameproof enclosure for the safety certificate, a reference pressure of explosion needs to be determined. However, the explosion pressure may be changed according to relative humidity of explosive gases. Therefore, the guideline on relative humidity should be recommended for measuring the explosion pressure for accurate and reproducible testings. This study examined the relationship of explosion pressure with relative humidity of hydrogen (31 vol %)-air and acetylene (14 vol %)-air mixture gases. The explosion pressures were measured by increasing the relative humidity of the gases by 10 % from dry state to 80 % in a cylindrical explosion enclosure of 2.3 L. on ambient temperature and atmospheric pressure (1 atm). The maximum explosive pressures were remained almost constant until the relative humidity reached 10 % for the hydrogen-air mixture and 20 % for the acetylene-air mixture. However, the maximum explosive pressures linearly decreased as the relative humidity increased. Based on the results of the study, it would be recommended to use 10 % relative humidity for the hydrogen-air mixture and 20 % for the acetylene-air mixture as the critical value in testing a flameproof enclosure.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.3
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• pp.37-42
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• 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.

• Journal of Hydrogen and New Energy
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• v.25 no.5
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• pp.491-499
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• 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.

• Particle and aerosol research
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• v.9 no.2
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• pp.69-78
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• 2013

In this study, the atmospheric aerosol concentration measured at different relative humidity levels was analyzed. Using an optical particle counter, PM10 and PM2.5 concentration as well as particle size distribution were measured and the relation between these size resolved data and relative humidity was studied. The results showed that mass concentration increases as relative humidity increases. The comparison between PM1, PM2.5 and PM10 showed that the fine particles grow more than coarse particles as relative humidity increases. The results also showed that PM10-2.5 and relative humidity do not show close correlation, which means that the mass increase of PM10 at high relative humidity is mainly due to the growth of PM2.5.

• Journal of the Korea Safety Management & Science
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• v.25 no.1
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• pp.51-58
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• 2023

Determination of explosion reference pressure is important in designing and testing flameproof enclosures (Ex d). Although relative humidity affects to explosion pressure, its effect is not well investigated for the gas group IIB, IIA, and I. This study tested explosion pressure for Ethylene (8 vol.%), Propane (4.6 vol.%), and Methane (9.8 vol.%), which are the representative gas of the gas group IIB, IIA, and I, at ambient temperature and atmospheric pressure (1 atm) under different relative humidity (0% ~ 80%). Ethylene- and Propane-air mixed gases generally tended to decrease as the relative humidity increased; however, explosion pressure was largely dropped at 20% of relative humidity compared to 0% and 10% of relative humidity. On the other hand, Methane-air mixture gas showed similar pressures at 0% and 10% of relative humidity; but no explosion occurred at more than 20%. The results of this study can be used in setting a testing protocol of explosion reference pressure for designing and testing a flameproof enclosure.

• Journal of the Korean Geographical Society
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• v.48 no.1
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• pp.19-36
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• 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.