• Journal of Biosystems Engineering
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• 제19권2호
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• pp.112-123
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• 1994

At present, no appropriate drying conditions can be found for the heated-air drying of mushroom in Korea. Usually, mushroom is being dried at the temperature range of 40 to $50^{\circ}C$ until the moisture content reaches 10~13% (wb). However, drying characteristics of the mushroom should be investigated for quality improvement and efficient drying operation of the mushroom. The results of this study may be summarized as follows ; 1. The effect of air temperature on the rate of drying was greater than that of relative humidity for drying of mushroom, and the rate of drying was increased with increase in the air temperature. 2. Drying rate for Shiitake mushroom showed falling-rate period of drying without constant-rate period of drying. Drying rate for Oyster mushroom showed a short constant-rate period at the initial stage of drying process, and followed by falling-rate period of drying. 3. Exponential and App.-Diffusion models were found to describe well the drying process of Shiitake mushroom. Exponential and Thompson models for Oyster mushroom in which Thompson model was the most suitable for Oyster mushroom. 4. The equilibrium moisture content of the mushroom decreased with decrease in the air temperature and increase in the relative humidity. In room condition($20^{\circ}C$, 54% RH), the calculated values of the equilibrium moisture content showed 11.17% for Shiitake mushroom and 13.19% for Oyster mushroom, respectively.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.242-247
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• 2009

The present study has been conducted to reduce the cold air drying rate. According to the cold air drying method, the quality-excellent product could be made and there would be little change of color, taste and smell. As compared with the hot air drying, the cold air drying equipment has the superior dehumidification in a constant drying zone. However, in a falling drying zone that equipment is not energy-efficient because the drying period could be longer by the dehumidificated.

• 한국수산과학회지
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• 제21권1호
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• pp.16-20
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• 1988

다시마의 건조와 수축특성을 알기위한 기초자료를 얻고자 건조중인 다시마의 건조 및 수축특성에 미치는 채취부위, 공기의 온도, 상대습도 및 풍속의 영향에 관하여 실험한 결과를 요약하면 다음과 같다. 1) 다시마의 열풍건조과정은 항률건조 기간이 없이 바로 감률건조기가 나타났으며 이것은 다시 감률건조 1단계 및 2단계로 구분되었다. 2) 두께가 얇은 선단부가 기부보다 수축이 더 많이 되었으며 공기의 온도 $50^{\circ}C$, 상대습도 $30\%$, 유속 0.4m/s의 일정한 건조 조건하에서 다시마의 선단부, 중간부 및 기부를 120분까지 건조하였을 경우 수축율은 각각 $57.5\%,\;54.0\%,\;42.7\%$이었다. 3) 상대습도가 낮은것은 높은것에 비해 건조속도 및 수축속도는 빨랐으나 함수률 $20\%$까지 건조하였을 경우 수축율은 오히려 상대습도가 높은것이 증가하였다.

• 한국안전학회지
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• 제39권1호
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• pp.33-40
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• 2024

This study analyzes the impact of regular preventive maintenance (PM) on reducing the failure rate and occurrence of falling accidents of industrial overhead doors. A reliable safety device model with an additional safety device, which is installed to replace a defective one, is proposed. The research methodology involves collecting breakdown and falling accident records, comparing and analyzing data before and after regular PM implementation, and experimenting with two types of retrofittable safety devices. Key findings are as follows. 1. Regular PM implementation significantly reduces the failure rate of old overhead doors. 2. A parallel structured model with two alternative safety devices can minimize falling accident risks. The study's contributions include the following. 1. The positive impact of PM on extending overhead door lifespan is quantified. 2. A general safety device model that can be retrofitted and used as replacement with a fail-safe function is proposed.

• 대한기계학회논문집B
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• 제21권2호
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• pp.294-302
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• 1997

Falling-film evaporation experiments for aqueous solution of lithium bromide (LiBr) were performed on a horizontal smooth 19.05-mm-dia copper tube. Average heat transfer coefficients were obtained with varied film Reynolds numbers, system pressures, LiBr concentrations and degrees of wall superheat. Heat transfer coefficients increase with increasing system pressure and decreasing concentration. For degrees of wall superheat, the heat transfer coefficient did not't show the distinct trend. For this experimental ranges, heat transfer coefficients showed maximum values at an optimal film Reynolds number. The results of this work were compared with pool boiling data reported previously, and it was shown that the heat transfer performance is superior to the pool boiling.

• 설비공학논문집
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• 제13권8호
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• pp.720-729
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• 2001

The effect of vapor flow direction on falling film heat transfer was experimentally investigated by using water. Parallel flow (both water and vapor downwards) showed higher heat exchange performance than counterflow(downward water and upward vapor). The difference became significant as the vapor flow rate was increased. It is supposed that the uprising vapor disturbs the solution film flow and heat transfer is reduced by uneven distribution or detachment of water film.

• 설비공학논문집
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• 제11권3호
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• pp.414-421
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• 1999

Falling film rectification involves simultaneous heat and mass transfer between vapor and liquid interface. In the present work, the adiabatic rectification process of ammonia-water vapor on the vertical plate was investigated. The continuity, momentum, energy and diffusion equations for the solution film and vapor mixture were formulated in integral forms and solved numerically. The model could predict the film thickness, the pressure gradient, and the mass transfer rate. The effects of Reynolds number and ammonia concentration of solution and vapor mixture, rectifier length, and the enhancement of mass transfer in each phases were investigated. The stripping of water in vapor mixture occurred new the entrance of ammonia solution, which imposed the proper size of an adiabatic rectifier. Rectifier efficiency increased as film Reynolds number increased and as vapor mixture Reynolds number decreased. The improvement of rectifier efficiency was significant with the enhancement of mass transfer in falling film.

• International journal of advanced smart convergence
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• 제9권2호
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• pp.38-48
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• 2020

The shaking-off the dust from balustrade of higher stories may cause the higher risk of falling accident rate. Main purpose of this study was to quantify an effect of balustrade heights and blanket types on possibility of falling accident relative to one's motor controllability during shaking-off the dust of the blanket from balcony. Female participants, who consisted of total 10 under condition of balustrade height of 3 kinds (90 cm, 110 cm, 130 cm) and blanket types (0.4 kg, 1.6 kg, 3 kg, 200^⁎230 cm), performed repetitively the task of shaking-off the dust of the blanket. Vertical position and velocity of center of mass due to increase of blanket weigh in case of balustrade height of 90 cm was increased, but vertical ground reaction force was decreased swiftly. That is, the higher balustrade height was, the less distance difference between center of mass and center of pressure was.

• 대한기계학회논문집B
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• 제37권5호
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• pp.513-522
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• 2013

본 연구에서는 다중효용 증발식 담수기에 쓰이는 강하막식 증발기의 수치해석을 수행하였다. 증발기에 사용되는 다관군을 다공성 매질로 묘사하고 공간평균 개념을 적용하였다. 증발기 내부의 유동계산 및 열 전달로 인한 상변화를 계산하기 위해서 FLUENT 와 UDF 가 사용되었다. 작동조건에 대한 증발기의 성능변화를 살펴보기 위해 수평관 내 증기 질량 유속을 $0.5{\sim}2.5kg/m^2s$, 관내입구 측 비 응축성 기체의 질량분율을 0~1%, 그리고 수평관 외 뿌려지는 강하막의 액막 레이놀즈 수를 100~1000 으로 바꾸어가며 해석을 수행하였다. 관내 증기유속 및 관외 강하막 레이놀즈 수가 증가할수록 증발량은 증가하였으며, 관내 비 응축성 기체의 질량분율이 1%증가함에 따라 증발량이 0.87%줄어들었다.

• 대한기계학회논문집
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• 제19권4호
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• pp.1071-1082
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• 1995

Numerical analyses have been performed to obtain the absorption heat and mass transfer coefficients and the absorption mass flux from a falling film of the LiBr aqueous solution which is cooled by cooling air. Heat flux at the wall is specified in terms of the heat transfer coefficient of cooling air and the cooling air temperature. Effects of operating conditions, such as the heat transfer coefficient, the cooling air temperature, the system pressure and the solution inlet concentration have been investigated in view of the local absorption mass flux and the total mass transfer rate. Effects of film thickness and film Reynolds number on the heat and mass transfer coefficients have been also estimated. Analyses for the constant wall temperature condition have been also carried out to examine the reliability of present numerical method by comparing with previous investigations.