• Journal of Advanced Marine Engineering and Technology
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• 제30권5호
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• pp.597-607
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• 2006

This paper presents a numerical simulation of the behavior of the LiBr solution droplets and falling films in horizontal tube banks of absorber. The model developed here accounts for the details of the droplets formation and impact process for absorption on horizontal tubes including the heat transfer from solution film to the tube wall. Especially. the characteristic of unsteady behavior of solution flow has been investigated. Flow visualization studies shown that the solution droplets and falling films have some of the complex characteristics. It is found that. with the numerical conditions similar to the operating condition of an actual absorption chiller/heater, the outlet solution temperature and heat flux from solution film to the tube wall have a stable periodic behavior with time. The solution droplets and falling films in horizontal tube banks of absorber is a periodic unsteady flow. The results from this model are compared with previous experimental observation taken with a high-speed digital video camera and shown good agreement.

• 설비공학논문집
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• 제16권2호
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• pp.194-201
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• 2004

In the present study, the improvement of absorption characteristics on combined heat and mass transfer process in a falling film of a vertical absorber by change of geometric parameters were studied experimentally and analytically. The energy and diffusion equations are solved simultaneously to give the temperature and concentration variations at the liquid solution-refrigerant vapor interface and at the wall. Absorption behaviors of heat and mass transfer were analyzed through falling film of the LiBr aqueous solution contacted by refrigerant vapor in the absorber. Effects of film Reynolds number, geometric parameters by insert device (spring) and flow pattern on heat and mass transfer performances have been also investigated. Especially, effects of the flow pattern by geometric parameters have been considered to observe the total heat and mass transfer rates through falling film along the absorber. As a numerical and experimental result, maximum absorption rate was shown at the wave-flow by insert device (spring). The error ranges between experiment and analysis were from 5.8 to 12％ at Re$_{f}$ > 100.0.

• 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.

• 한국환경과학회지
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• 제23권5호
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• pp.781-786
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• 2014

Growth and physiological disorders caused by abnormally low temperatures were evaluated in pepper, an important field crop in Korea. In addition, the effects of chemical treatment using glutamine was verified on minimizing the damages by low temperature. The growth of pepper plants in stem length and diameter was suppressed as the temperature decreased from $25^{\circ}C$, and the suppression level was the highest for plants grown for 90 days at $20^{\circ}C$. However, root growth was not affected by the different temperatures. The number of leaf and leaf area decreased at the temperatures below $25^{\circ}C$, an optimum temperature for growth. Fresh weight and dry weight decreased for plants grown at $20^{\circ}C$. Pepper fruit yield also decreased by 11% at $20^{\circ}C$ in comparison to $25^{\circ}C$. Falling blossom rate was different depending on the growth temperature, and the rate was 27.2% at $25^{\circ}C$, 35.2% at $22.5^{\circ}C$, and 41.0% at $20^{\circ}C$, indicating that falling blossom rate increased as temperature decreased. Different growth temperatures did not affected on the level of symptom of calcium deficiency and Phytopathora blight. Falling blossom was severe at abnormally low temperature of $20^{\circ}C$, but the treatment of glutamine reduced falling blossom rate and increased the yield by 7.0% as compared to control. The optimum concentration of glutamine treatment was 10 mg/L for yields.

• 한국식품조리과학회지
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• 제24권4호
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• pp.511-516
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• 2008

In this study, composite flour and dough were prepared with concentrated sweet pumpkin powder(CSPP) at varying concentrations of 3, 6, 9, 12, and 15%. The samples and a control were then compared with regards to quality characteristics, including moisture, protein, and ash contents, farinogram characteristics, amylogram characteristics, and falling number of flour and extensogram characteristics of dough, in an effort to determine the optimal ratio of CSPP in the formulation. As the CSPP content increased, the moisture and protein contents of the flour increased, whereas the ash contents decreased. With regard to the farinogram characteristics of flour, water absorption, development time, and stability decreased with increasing CSPP content, while weakness increased. The control group evidenced a significantly higher beginning temperature of gelatinization as compared to the CSPP samples. The temperature of maximum viscosity, maximum viscosity, and falling number of flour decreased with increasing CSPP content. With regard to the extensogram characteristics of dough, extensibility decreased with increasing testing time and CSPP content, whereas resistance, maximum resistance, and R/E ratio increased. In conclusion, these results show that $6{\sim}9%$ CSPP may prove very useful as a substitute for wheat flour in the production of hardroll bread, and may provide good nutritional and functional properties.

• 한국조경학회지
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• 제27권1호
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• pp.19-28
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• 1999

This survey is to investigate the effect of plants and waterscape facilities on the thermal indoor environment and to provide basic data for proper plant cultivation to enhance indoor landscape. The survey of the measure of comfort on the indoor environment for the residents of Taegu shows that the measure of comfort on the thermal-environment, which consist of temperature and humidity, has more negative responses than the measure on lighting . are . sound environment, which consists of air freshness, lighting condition and sound environment. The experiments on the effect of the amount of leaves and the distance of plants on the indoor thermal-environment are made. The experimental results illustrate that, as the capacity of a plant becomes greater and the distance from the plant shorter, the falling effect of temperature and the rising effect of humidity on the top of the plant are taken higher than on the side of the plant. When the same amount of leaves is set up, the distance range of the rising effect of humidity becomes wider than that of the falling effect of temperature. The investigation of the effect of waterscape facilities on the indoor thermal-environment shows that temperature and humidity of the space with installed waterscape facilities are lower and higher than without facilities, respectively.

• 대한화학회지
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• 제37권12호
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• pp.1003-1009
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• 1993

여러 온도와 압력에서 벤젠의 점성도를 결정하여, 액체 벤젠의 점성도에 미치는 온도와 압력의 영향에 대하여 연구하였다. 여러 온도와 압력으로 유지되고 있는 일정한 밀도의 벤젠 속에서 공 낙하 시간을 측정함으로써 벤젠의 점성도를 산출할 수 있었다. 그 결과로부터 벤젠의 비부피에 미치는 온도와 압력의 영향, 자유부피에 미치는 온도와 압력의 영향에 대해서 알아보았으며, 결론적으로 벤젠의 점성도에 대한 온도와 압력의 영향을 온도와 압력의 변화에 따르는 자유부피의 변화에 의하여 고찰하였다.

• 한국식품과학회지
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• 제14권4호
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• pp.342-349
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• 1982

송풍식건조과정(送風式乾燥過程) 중의 말쥐치육의 건조기구(乾操機構)와 수분활성(水分活性)과의 관계를 검토하기 위하여 $47.5^{\circ}C$에서 풍속과 공기의 상대습도를 달리하여 실험한 결과를 요약하면 다음과 같다. 전체 건조과정은 정속건조기(定速乾燥期)와 감속건조기(減速乾燥期)로 구분되었다. 정속건조기(定速乾燥期)는 건조표면(乾燥表面)이 수분활성(水分活性) 1.0을 유지하는한 계속되었으며, 온도와 상대습도가 일정할 때 정속건조속도(定速乾燥速度)는 공기의 속도(速度)의 제곱근에 비례하였다. 감속건조기(減速乾燥期)는 건조기구(乾操機構)가 서로 다른 제(第)1 및 제(第)2감속건조기(減速乾燥期)로 구분되었다. 제(第)1감속건조기(減速乾燥期)는 모세관 응축수의 건조표면(乾燥表面)으로의 이동이 불충분한 불포화표면건조기(不飽和表面乾燥期)였으며, 이 때의 건조속도(乾燥速度)는 공기의 온도가 일정할 때 상대습도에 크게 좌우되었다. 제(第)1감속건조기(減速乾燥期)와 제(第)2감속건조기(減速乾燥期)의 변환점에서 표면경화현상(表面硬化現象)이 시작되었다. 상대습도의 변화에 따라 제(第)2감속건조기(減速乾燥期)가 시작될 때의 수분활성(水分活性)과 수분함량(水分含量)은 각각 다른 값을 나타내었다. 제(第)2감속건조기(減速乾燥期)는 다시 건조기구(乾操機構)를 달리하는 두 개의 건조기(乾燥期)로 구분되었다. 제(第)2감속건조기(減速乾燥期)의 1단계는 말쥐치육 내부의 모세관 응축수가 건조표면(乾燥表面)으로 확산, 증발하여 건조가 진행되었으며, 이때의 수분의 확산계수는 $47.5^{\circ}C$에서 $2.89{\cdot}10^{-10}m^2/sec$였다. 표면경화현상(表面硬化現象)은 말쥐치육의 수분활성(水分活性)이 0.7에 이를때까지 계속되었다. 제(第)2감속건조기(減速乾燥期)의 2단계는 수분활성(水分活性) 0.45에서 시작되었다. 이 때의 건조는 말쥐치육 내부에 다분자층(多分子層)으로 흡착(吸着)한 결합수의 건조표면(乾燥表面)으로의 확산, 증발에 의하여 진행되었다. 흡착수분(吸着水分)의 분자층(分子層)의 수는 4였으며, $47.5^{\circ}C$에서의 확산계수는 $4.38{\cdot}10^{-11}m^2/sec$였다.

• 대한기계학회논문집
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• 제19권6호
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• pp.1501-1509
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• 1995

It is known that the heat and mass transfer characteristics in the absorber are most sensitive of the temperature boost of all the heat exchangers and the development of a more efficient absorber should be highly important. This paper describes absorption experiments made with different inside tube diameters, tube length and tube shapes. The purpose of this study is to acquire basic knowledge about heat and mass transfer in a falling film type absorber with vertical inner tubes. Heat and mass transfer were measured for water vapor absorption into a Lithium Bromide-water solution flowing down an absorber of vertical inner tubes. As a result, insert spring tube compares bare tube and heat transfer improved by order of insert spring tube P2(pitch 20 mm) and P1(pitch 10 mm).

• International Journal of Air-Conditioning and Refrigeration
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• 제13권3호
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• pp.158-166
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• 2005

The present study investigated experimentally and numerically the enhancement of absorption performance due to the waviness of falling film in the vertical absorber tube. The momentum, energy and mass diffusion equations were utilized to find out temperature and concentration profiles at both the interfaces of liquid solution and refrigerant vapor and the wall. Flow visualization was performed to find out the wetting characteristics of the falling film. The maximum heat transfer coefficient was obtained for the wavy flow using spring as an insert device through both numerical and experimental studies. Based on the numerical and experimental results, the maximum absorption rate was found for the wavy-flow using spring as the insert device. The differences between experimental and analytical results ranged from $5.0\;to\;25\%\;when\;Re_j>100$.