• 한국농공학회지
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• 제16권4호
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• pp.3600-3610
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• 1974

Experimental work of batch-type dryer was conducted to develop its optimurm operating conditions by analyzing the major factors which affect the drying performance. A laboratory batch-type dryer was constructed and tested for various levels of heated-air rates, and depths of grain deposit. Tong-il rice variety having the initial moisture content of approximaely 23 per cent in wet basis was used for the experiment. The criteria selected for establishing the optimum operating condition were the drying performance rate, the thermal efficiency, and the operational cost of the dryer. The results of the study are summarized as follows: 1. The performance rate of dryer for a specific operating condition was defined as total amount of material dried per hour when the moisture content of grains in the upperlayer reaches to 16 per cent in wet basis. The optimum operating conditions as viewed in the rate of drying performance could be justified by functional realtionship between the depth of grain deposit and air flow rate. In other words, there was a definite depth of grain deposit for a given air-rate which make the dryer performance maximum. The optimum grain depth for the batch-type dryer with 3.3㎡ loading area and with the attached axial fan was about 35cm. 2. The thermal efficiency for the dryer was evaluated by the ratio of the latent heat required to evaporate the grain moisture to the heat input required to raise the ambient air-temperature to 40 degree centigrade. The optimum operating condition as viewed in term of thermal efficiency analyzed was that grater depth and lower air flow-rate may be desirable. This condition is contracted with the optimum condition as viewed by the dryer performance rate. 3. The annual operating cost of batch-type dryer was analyzed for different annual hour of use and for different operation condition. The optimum condition as viewed in terms of operating cost was almost identical to one as viewed in terms of dryer performance rate. Therefore, the most economical use of batch-type dryer for the same annual operating hours can be obtained when the dryer operated in the condition of maximum dryer performance rate. Increasing the annual operating hour may be desirable to cut down the dryer operation cost, since the annual hour of dryer use is much sensitive to the operating cost than any peractical conditions of dryer operation. 4. The most desirable operational condition as justified by combining all the criteria, dryer performance rate, thermal efficiency and annual operating cost, could be concluded to operate the dryer in the condition of maximum performance rate. The condition in general is identical to the lowest operation cost for a given annual operating hour.

• 지질공학
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• 제34권1호
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• pp.137-146
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• 2024

우리나라의 한국산업표준(KS F)에는 105 ± 5℃로 노건조된 암석을 대기중에 꺼내어 저울에 무게를 측정하도록 하고 있다. 그러나 건조로 외부의 대기에 노출된 암석에서는 대기중의 수분을 흡수하여 무게가 증가하는 문제가 발생된다. 본 연구에서는 정육면체 모양으로 가공된 크기가 다른 8개의 황등화강암 시편을 사용하여 측정 방법에 따른 건조무게를 측정하고 비교 분석하였다. 대기중에서 측정된 특이점의 건조무게는 건조로 속에서 측정된 건조무게에 비하여 더 작게 나타났다. 건조 방법에 따른 건조무게의 차이는 암석의 크기와 양(+)의 상관관계를 나타내었고, 암석의 단위무게당 건조무게 차이는 암석의 크기가 클수록 오히려 작아지는 음(-)의 상관관계를 나타내었다. 대기중 노출된 암석의 무게는 가열된 암석 주위에서 발생되는 대류의 영향과 대기중 수분 흡수로 인한 영향의 크기에 따라 결정되며, 특이점은 두가지 영향의 크기가 같을 때 발생된다. 암석의 크기가 클수록 특이점 발생까지의 시간이 더 오래 걸리고 무게의 감소량도 증가되었다. 또한, 수분 흡수에 의한 초기 측정 무게까지 회복되는 시간도 더 오래 걸렸다. 향후, 특이점의 무게와 건조로 내부에서 측정된 건조 무게에 관한 연구를 통하여 현재 한국산업표준(KS F) 시험규정의 한계점을 보완할 수 있을 것이다.

• Journal of the Korean Wood Science and Technology
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• 제32권2호
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• pp.9-18
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• 2004

본 과제는 Spruce재가 사우나와 같은 고온 공간용 부재(部材)로 사용되어질 때 나타나는 수지삼출의 문제점을 해결하여 그 방안을 제시코저 수행하였다. 건식(乾式)공간용 부재(部材)의 경우 적절한 열기건조가 이루어진다면 별도의 처리를 실시하지 않더라도 110℃의 수지삼출 안정선을 얻을 수 있는 것으로 확인되었으며, 고주파진공건조에 의해 수지삼출 안정선이 열기건조보다 약 20℃ 정도 더 상승하였다. 습식(濕式)폭로시험에서는 저압증기폭쇄처리재의 경우 열기건조재나 고주파진공건조재 모두 수지가 전혀 삼출되지 않은 반면에, 무처리재의 경우 건조방법에 관계없이 130℃ 이상의 폭로조건에서는 수지삼출의 정도가 건식(乾式)폭로시험의 경우보다 심한 것으로 나타나, 수지삼출을 예방하기 위하여 인공건조중 저(低)함수율 상태의 건조말기에 고온(高溫)을 적용하여 건조하는 것보다는 건조전 고(高)함수율 상태에서 과열(過熱)증기로 분무(噴霧)처리하는 것이 더 바람직한 것으로 확인되었다.

• 동력기계공학회지
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• 제10권2호
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• pp.36-40
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• 2006

In order to prevent the environmental pollution, the dryers are commonly used to treat sludge that one of sewages is polluting the quality of water. Generally, the drying method is various as to the property of material and use. Rotary dryer is a good apparatus to treat them. It is the way that is to make substance transmission and heat using hot air between sludge particle and heated gas. In this paper, we developed a 3-pass rotary dryer for a design program for the 3-pass rotary dryer with various conditions. The working conditions of dryer are a raw sludge feed rate, input & output water content and operation time etc.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2002년도 동계 학술대회 논문집
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• pp.362-368
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• 2002

가. 인공광원은 색온도, 연색지수, 파장대, 조도등에서 태양에 가장 근접한 메탈할라이드 등을 선정했다. 나. 광원을 공시비닐하우스에 적용키 위해 반사갓 재료 및 각도, 등 간격별로 요인시험한 결과 엠보싱처리 알루미늄 재료, 반사갓 각도 전후좌우 30$^{\circ}$, 등간격 550mm에서 가장 좋은 것으로 나타나 비닐하우스용 고추건조장치의 장조사부 설계.제작에 적용하였다. 다. 건조성능시험결과 시험구(인공광+열풍)가 대비구(열풍)에 비해 건감속도가 10.3-19.7% 향상되었고, 건조에너지도 16.1~17.1% 절감되는 것으로 나타났다. 라. 시험구 및 대비구의 색택(ASTA color) 및 당도에 대해 F-test 검증결과 5% 유의수준에서 고도의 유의차가 있는 것으로 나타났으며 ASTA color값은 차이가 컸으나 당도에서는 차이가 없는 것으로 나타났다. 결론적으로, 농가에서 사용하고 있는 하우스 열풍건조에 비해 색택 및 성분면에서 양호하기 때문에 비닐하우스 건조방식을 채택하는 농가를 대상으로 인공광조사 건조방식을 추가한다면 전천후 건조방식으로 적용이 가능할 것으로 사료되었다.

• 동력기계공학회지
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• 제9권4호
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• pp.51-57
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• 2005

In order to prevent the environmental pollution, the dryers are commonly used to treat sludge that one of sewages is polluting the quality of water. Generally, the drying method is various as to the property of material and use. Rotary dryer is a good apparatus to treat them. The rotary dryer is the way that is to make substance transmission and heating using hot air between sludge particles and heated gas. In this paper, we performed a numerical analysis of the inner air flow of the 3-pass rotary dryer through the changing rotational speed from 3rpm to 10rpm. In this result, we found that 3rpm is effective to dry material in terms of heat transfer because large scale velocity fluctuation is occurred inside the first and second drum. Also we confirmed that 5rpm and 8rpm showed up uniform flow at the center area of the first drum.

• 한국분말재료학회지
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• 제9권3호
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• pp.167-173
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• 2002

A new approach to produce nanostructured WC/Co composite powders by a mechanochemical process was made to improve the mechanical properties of advanced hardmetals. Homogeneous spherical W-Co salt powders were made by spray drying of aqueous solution from ammonium metatungstate($(NH_4)_6(H_2W_{12}O_{40})\cdo4H_2O$,AMT) and cobalt nitrate hexahydrate (Co(NO$_3$)$_2$.6$H_2O$). spray dried W-Co salt powders were calcined for 1 hr at $700^{\circ}C$ in atmosphere of air. The oxide powder was mixed with carbon black by ball milling and this mixture was heated with various temperatures and times in $H_2$. The $WO_3/CoWO_4$ composite oxide powders were obtained by calcinations at $700^{\circ}C$. The primary particle size of W/Co composite oxide powders by SEM was 100 nm. The reduction/carburization time decreased with increasing temperatures and carbon additions. The average size of WC particle carburized at $800^{\circ}C$ by TEM was smaller than 50 nm.

• Journal of Magnetics
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• 제6권1호
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• pp.23-26
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• 2001

Nano-crystalline hexaferrite $BaFe_{12}O_{19}$(BaM) thin films have been prepared by the sol-gel method. A solution of Ba-nitrate and Fe-nitrates was dissolved in solvent with the stoichiometric ratio Ba/Fe=1/10. Films were spin-coated onto $SiO_2$Si substrates, dried and then heated in air at various temperatures. In films prepared at a drying temperature $T_d=250^{\circ}C$ and a crystallizing temperature 650${\circ}C$, single-phase BaM was obtained. High coercivities were obtained in these nano-crystalline thin films, 4~5.5 kOe for hexaferrite. Polycrystalline BaM/$SiO_2$/Si(100) thin films were characterized by Rutherford backscattering (RBS), thermogravimetry (TGA), differential thermal analysis (DTA), x-ray diffraction (XRD), and vibrating sample magnetometry (VSM), as well as Fourier transform infrared spectroscopy (FTIR). The perpendicular coercivity $H_{C\bot}$ and in-plane coercivity $H_{CII}$ after annealing at 650${\circ}C$ for 2 hours were 4766 Oe and 4480 Oe, respectively, at room temperature, under a maximum applied field of 10 kOe.

• 한국지반환경공학회 논문집
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• 제24권9호
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• pp.25-32
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• 2023

한국산업표준(KS F)에는 건조된 흙과 암석의 무게를 측정하는 다양한 규정들이 있다. 그러나, 110±5℃ 또는 105±5℃로 건조 후 공기 중에서 건조무게를 측정하면 측정시간이 지속됨에 따라 무게가 감소 후 증가하는 무게 특이점이 나타난다. 본 연구에서는 울릉도 현무암질 암석을 40~110℃로 노건조 하였고, 0.0001g(0.1mg) 감도의 전자저울에 무게를 측정하여 무게 특이점을 찾았고, 나타난 무게 특이점을 이용하여 건조무게를 쉽게 결정할 수 있는 방법을 제시하였다. 온도에 따른 암석시편의 특이점을 다양하게 분석한 결과, 특이점은 40~110℃의 온도구간에서 모두 나타났고 가열온도가 높을수록 특이점의 무게가 작게 나타났다. 특별히, 무게 특이점이 지속되는 현상이 나타났고, 가열온도가 높을수록 특이점의 지속시간이 짧게 나타났다. 대류측정 실험의 결과에 의하면 특이점의 발생 원인은 가열된 암석이 공기와의 접촉에 의해 발생된 대류현상이 원인이라는 것을 알 수 있었다. 노건조된 암석의 무게 감소는 대류발생으로 인한 영향이 공기 중 수분 흡수의 영향보다 우세할 때 발생된다. 반대로 암석의 무게 증가는 공기 중 수분 흡수의 영향이 대류발생으로 인한 영향보다 우세할 때 발생된다.

• 자원환경지질
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• 제33권5호
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• pp.391-404
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• 2000

This study investigated the geochemical characteristics of mine drainage discharged from an abandoned coal mine in the Hwasoon area. Surface water samples were collected from 23 locations along the Hancheon creek. The concentration of Zn and Cu in stream waters was highest at low pH (3.53), whereas the content of TDS and TDI was highest at high pH (7.78) due to the concentration of Ca, $HCO_3$ and $SO_4$. At the upstream site, the Ba, Fe, Mn, Zn, and $SO_4$ contents were relatively high but decreased significantly with the distance from the coal mine. On the contrary, the Na and $NO_3$ contents were low at the upstream site but increased downstream. Yellow precipitate material collected in the Hancheon consisted mainly of iron and LOI. This yellow precipitate was heated from 100 to $900^{\circ}C$ for 1 hour. With increasing temperature, the intensity of hematite peaks were sharply produced in X-ray pattern and the absorption band Fe-O of hematite increased in IR due to dehydration and melting. The yellow to brown precipitate and evaporite materials were collected by a air-dry from the acid mine water at the laboratory. After drying, the concentration of ions in the acid water samples increased progressively in oversaturation with respect to either gypsum, ferrohexahydrite or quenstedetite. The X-ray powder diffraction studies identified that the precipitated and evaporated materials after drying were well crystallized gypsum, ferrohexahydrite and quenstedetite. Diagnostic peaks used for identification of gypsum were the 7.65, 4.28, 3.03, 2.87 and 2.48$\AA$ peaks and those for ferrohexahydrite were the 5.46, 5.12, 4.89, 4.44, 4.05, 3.62, 3.46, 3.40, 3.20, 3.03, 2.94, 2.53, 2.28, 2.07, 1.88 and 1.86${\AA} peaks. The IR spectra with OH-stretching, deformation of $H_2O$and ${SO_4}^{2-}$stretching vibration include the existence of gypsum, ferrohexahydrite and quenstedetite in the precipitated and evaporite materials. In the SEM and EDS analysis for the evaporite material, gypsum with well-crystallized, acicular, and columnar form was distinctly observed.