• Journal of Biosystems Engineering
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• v.11 no.1
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• pp.52-63
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• 1986

This study was performed to find out drying characteristics and develop drying model for the design of an efficient dryer or drying system of red peper. The basic model which describes drying phenomenon of red pepper was firstly established, and drying tests were conducted at 14-different drying conditions. In this test, the effects of drying air temperature and relative humidity on the rate of drying were undertaken. Finally, a new drying model based on these experimental results was developed to describe the drying characteristics of red pepper. The results from this study may be summarized as follows. 1. Drying constant of the basic model established from Lewis' experimental model and diffusion equation was theoretically deduced as a function of moisture content and inner-temperature of red pepper. 2. From the results of drying tests, drying air temperature was found to have the greatest effect on the rate of drying. However, the effect of temperature was small for the condition of high relative humidity, and for low temperature, the effect of relative humidity was found to be large even though the range of relative humidity was low. 3. Modified Henderson equation was found to be better than Chung equation as the EMC model for the estimation of the equilibrium moisture content of red Pepper. 4. Constant-rate drying period did not exist in the red pepper drying test. And falling-rate drying period was divided into three distinct phases. Drying rate was dependent on the moisture content, the inner-temperature of red pepper and the change of physical property due to drying. 5. Drying constant increased with decrease of free moisture content, but it decreased at the end of the drying period. Also, drying constant was dependent on the drying air temperature and relative humidity. 6. The new drying model developed in this study was found to be most suitable in describing the drying characteristics of red pepper. Therefore, it may be concluded that drying time could be accurately estimated by the new drying model.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.151-156
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• 2005

Auto exhausts and air pollution can become trapped in the cabin of vehicle, reducing the amount of oxygen available for breathing. Driver may feel sleepy, headaches, nausea, confusion, dizziness and lower levels of oxygen can damage the driver's general health. Consequently, oxygen generator purified oxygen into the car to help driver get the oxygen driver's body needs. In this study, in order to evaluate the oxygen generator performance, the samples that the various conditions(humidity(50%, 100%), flow and oxygen concentration) were examined. There were three types of oxygen generator; sample 1($2.5{\ell}/min$, $36%O_2$), sample 2($4.5{\ell}/min$, $41%O_2$) and sample 3($5{\ell}/min$, $39%O_2$). As the humidity increased from 50% to 100%, the oxygen concentration of the sample 1(36%), 2(41%) and 3(39%) was reduced $31%O_2$, $38%O_2$ and $38%O_2$, respectively. Also, the each sample measured that effect of human in car on oxygen concentration, if the oxygen concentration is one person in car, each sample of oxygen concentration was $20.8%O_2$, $23.7%O_2$ and $21.2%O_2$. From the above results, it was shown that oxygen generator for car, if the oxygen concentration is increased, effect of humidity is reduced, and that in the sample of supplying a high-rate of oxygen, the oxygen concentration is increased. It was suggested that effect of humidity on oxygen generator for car can be reduced according to the supply of oxygen.

• Proceedings of the Materials Research Society of Korea Conference
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• 2008.05a
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• pp.30.1-30.1
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• 2008

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.302-306
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• 2017

Humidity affect performance and durability of proton exchange membrane fuel cell (PEMFC). High humidity of gases generally enhance the performance, but high humidity have the danger of flooding. I-V performance, linear sweep voltammetry, cyclo voltammetry, and impedance of micro-channel cell measured with change of relative humidity (RH). Flooding phenomena started at RH 70%. Ion conductivity of membrane reached maximum value at RH 80%. Maximum current density of $1,700mA/cm^2$ (at 0.6 V) was obtained at RH 80%. Therefore the effect of ion conductivity increasement was higher than that of mass transfer decrease by flooding at RH 80%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.697-702
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• 2010

An enthalpy exchanger in which heat and moisture transfer occur between the indoor and outdoor air operates at various outdoor conditions. In this study, the effect of the outdoor-air temperature and humidity on the performance of an enthalpy exchanger was experimentally investigated. An apparatus was specially-made to accurately measure the incoming and outgoing dry- and wet-bulb air temperatures as well as the flow rates. Tests were conducted in constant-temperature and constant-humidity chambers at different outdoor temperatures and humidities. It is shown that the effectiveness of latent-heat exchange increases as the relative humidity increases; further, this effect exhibited minimal dependence on the absolute humidity. However, the effectiveness of sensible-heat exchange is independent of both temperature and humidity

• Journal of Power Electronics
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• v.15 no.3
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• pp.841-848
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• 2015

As a vital part of renewable energy and electrical traction, power converters are supposed to have high reliability and good performance. However, power semiconductors produce considerable heat when the power converter works, which results in high junction temperatures that lower the reliability and performance of the power semiconductors. Many studies show that ambient humidity has a significant effect on power devices, but the influence of high humidity on junction temperatures has yet to be studied. Therefore, this paper presents a thermal model for power converters in moist air to obtain the junction temperature increase, which is utilized for the power converter used in a Switched Reluctance Motor System. Simulation results show that the law of converter temperature distribution is independent of the relative humidity in the case of fixed ambient temperature, whereas the temperature in the power converter decreases as the ambient relative humidity increases. These simulation results are validated with the experimental results.

• Journal of the Korean Ceramic Society
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• v.48 no.4
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• pp.293-297
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• 2011

The thermodynamic behavior of phenolic resin was investigated to verify the relation between the properties of porous ceramics with $ZrO_2$-C system for submerged entry nozzle and the characteristics of phenolic resin with various relative humidity. The green and the sintered density were decreased between 25% and 50% relative humidity, whereas they were gradually enhanced above 50% relative humidity. The highest value of apparent porosity was 20.1% and the minimum compressive strength was 69MPa in the specimen using the powder exposed to 50% relative humidity. As a result of thermal analysis for phenolic resin, the shift of endothermic peak to low temperature and the reduction of exothermic peak were observed, and the peaks corresponded to melting and curing of phenolic resin, respectively. The melting and the curing of phenolic resin generate the change of green density, and it can affect the properties of submerged entry nozzle.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.1
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• pp.29-43
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• 1998

This study was to investigate the effect of .compressive load and cyclic humidity(2$0^{\circ}C$, 65% and 90% RH) on the physical and mechanical properties of corrugated board. Corrugated boards in the study were under compressive load and under cyclic humidity, and their properties were compared to those without load. Results were summarized as follows ; 1 Statistically significant correlation was shown between the ring crush of the boards and the compressive strength of cylinder specimen made from the boards. So we could study the compressive behavior of board with cylinder specimen. 2. The boards under the compressive load increased their moisture content and thickness much more than those without load both in constant and in cyclic RH. 3. The compressive and tensile strength of board samples were inversely and closely proportional to the sheet moisture content regardless of their load and humidity history. 4. The moisture content did not show any significant proportionality to the change of burst strength of boards within this experiment. 5. Board reconditioning in standard condition led to the recovery of the strength loss that had occurred under various load and humidity condition. 6. The handsheets prepared from the boards that had experienced compressive load and cyclic humidity, and those with no-load and 65% RH did not show any significant difference in strength properties. No physical damage or load-carrying properties of the wood fiber were observed by the compressive load and cyclic humidity history.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.5
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• pp.314-320
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• 2021

Controlling ambient humid condition through high performance humidity sensors has become important for various fields, including industrial process, food storage, and the preservation of historic remains. Although aerosol deposited humidity sensors using ceramic BaTiO₃ (BT) material have been widely studied because of their longtime stability, there remain critical disadvantages, such as low sensitivity, low linearity, and slow response/recovery time in case of the sensors fabricated at room temperature. To achieve superior humidity sensing properties even at room temperature condition, BT-Cu composite films utilizing aerosol deposition (AD) process have been proposed based on the percolation theory. The BT-Cu composite films showed gradually improved sensing properties until the Cu concentration reached 15 wt% in the composite film. However, the excessive Cu (above 30 wt%) containing BT-Cu composite films showed a rapid decrease of the sensing properties. The results of observed surface morphology of the AD fabricated composite films, to figure out the metal filler effect, showed correlation between surface topography as well as size and the amount of open pores according to the metal filler content. Overall, it is very important not only dielectric constant of the humidity sensing films but also microstructures, because they affect either the variation range of capacitance by ambient humidity or adsorption/desorption of ambient humidity onto/from the humidity sensing films.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.262-268
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• 1998

This study were performed to find the cooling effect and to provide design data during summer season. for the Pad ＆ Fan system of Venlo type greenhouse. The temperature and humidity variation along the greenhouse width and wind velocity in the greenhouse were surveyed. Also, the influence of shading on the cooling effect were analyzed. While Pad ＆ Fan system were operated, the temperature, humidity and wind velocity in greenhouse were different by the distance from the Pad and the height from the ground. The temperature difference between Pad and Fan was about 8.1$^{\circ}C$~10.4$^{\circ}C$ without shading and about 4.4$^{\circ}C$~5.5$^{\circ}C$ with shading.