• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.32 no.5
• /
• pp.335-341
• /
• 2008

Thermal transport from vertical heated surface to falling liquid film in a channel has been investigated experimentally. Air-flow is introduced into channel to make a counter flow against falling liquid film. This problem is of particular interest in the design of direct contact heat exchange system, such as cooling tower, evaporative cooling system, absorption cooling system, and distillation system. The effects of channel width and air flow rate on the heat transfer to falling liquid film are studied in detail. The results obtained indicate that heat transfer rate is gradually decreased with an increase in the channel width without air flow as well as with air flow in a channel. It is also found that heat transfer rate of air-flow is increased while heat transfer rate of falling liquid film is decreased with an increase in the air flow rate at a given channel width. However, total heat transfer rate from the heated surface is increased as the air flow rate is increased.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2291-2296
• /
• 2007

Thermal transport from vertical heated surface to falling liquid film in a channel has been investigated experimentally. Air-flow is introduced into channel to make a counter flow against falling liquid film. This problem is of particular interest in the design of direct contact heat exchange system, such as cooling tower, evaporative cooling system, absorption cooling system, and distillation system. The effects of channel width and air flow rate on the heat transfer to falling liquid film are studied in detail. The results obtained indicate that heat transfer rate is gradually decreased with an increase in the channel width without air flow as well as with air flow in a channel. It is also found that heat transfer rate of air-flow is increased while heat transfer rate of falling liquid film is decreased with an increase in the air flow rate at a given channel width. However, total heat transfer rate form the heated surface is increased as the air flow rate is increased.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.5
• /
• pp.513-522
• /
• 2013

In the present work, a numerical study of a horizontal falling film evaporator in a multi-effect distillation (MED) plant is performed. Tube bundles in the evaporator are described as porous media, and a volume-averaged method is applied. To calculate the fluid flow and phase change in the evaporator due to heat transfer in the system, FLUENT and user-defined functions (UDF) are used. To observe the performance of the evaporator under different operational conditions, tests are conducted for a steam mass flux ranging from 0.5 to 2.5 $kg/m^2s$ in the horizontal tube, for mass fraction of the noncondensable gas in the tube inlet ranging from 0% to 1%, and for film Reynolds numbers ranging from 100 to 1,000 for the falling film. The evaporation rate increases with the steam mass flux and Reynolds number. In contrast, the evaporation rate decreases by 0.87% with a 1% increase in the mass fraction of the noncondensable gas in the tube.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.2
• /
• pp.143-148
• /
• 2011

Corrosion at the top of a distillation column is a common problem in refineries and chemical plants. In particular, severe damage has been inflicted in refineries by corrosive materials such as hydrogen sulfide and chlorine. Therefore, the mechanism of the corrosion occurring at the top of a distillation column has been analyzed, and a model for forecasting the corrosion rate has been developed. Four major materials were selected for modeling: $H_2S$, $CO_2$, $H^+$ and $Cl^-$. These were selected by taking into consideration their effect on the corrosion rate. Studies on the transport phenomenon and reaction engineering for this model were carried out, and the reliability of the model was verified on the basis of the data measured at a real refinery.

• Resources Recycling
• /
• v.17 no.6
• /
• pp.50-56
• /
• 2008

A polypropylene fraction collected from the stream of post-consumer plastics was pyrolyzed. The aim of this study is to observe the dependence of yield of BTEX-aromatics normally used as solvent on the reaction temperature. To reach the goal, three experiments were carried out at different temperature between 650 and $700^{\circ}C$, using a fluidized bed reactor that shows an excellent heat transfer. In the experiments, product gases were used as a fluidizing medium to maximize the amount of BTEX-aromatics at fixed flow rate and feed rate during the pyrolysis. Oil, gas and char were obtained as product fractions. Product gases were analyzed with GCs(TCD, FID) and with a GC-MS system for qualitative analysis. For an accurate analysis of product oil, the product oil was distilled under vacuum, and separated the distillation residues from oil fractions that were actually analyzed with a GC-MS system. As the reaction temperature went higher, the content of BTEX-aromatics increased. The maximal yield of BTEX-aromatics was obtained at $695^{\circ}C$ with a value of about 30%. The main compounds of product gas were $CH_4$, $C_2H_4$, $C_2H_6$, $C_3H_6$, $C_4H_{10}$ and the product gas had an higher heating value about 45MJ/kg. It could be used as a heat source for a pyrolysis plant or for other fuel applications.

• Resources Recycling
• /
• v.17 no.5
• /
• pp.3-10
• /
• 2008

We researched recycle of mixed waste acids including HF, $CH_{3}COOH$, $HNO_3$ produced during semiconductor wafer process. At first, we recovered HF in form of $Na_{2}SiF_6$ by precipitation using $NaNO_3$ and $Na_{2}SiO_3$. Concentration of HF was made down from 110 g/L, initial concectration, to 0.5 g/L and Recovery rate of HF was 99.5%. After recovery of HF, concentration of $HNO_3$ and $CH_{3}COOH$ is 498 g/L, 265 g/L respectively. From that mixed acid, we recovered $CH_{3}COOH$ using 2 stages of fractional distillation. In first stage, $CH_{3}COOH$ was distilled for separation from $HNO_3$. And in second stage, we recoverd refined $CH_{3}COOH$ by using fractional distillation for removing a little amount of $HNO_3$ in $CH_{3}COOH$ vapor. The concentration of recovered $CH_{3}COOH$ in second stage is 20% and finally recovery rate of $CH_{3}COOH$ is about 87.5%.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.18 no.2
• /
• pp.51-58
• /
• 2023

This paper proposes a deep learning method for estimating the heart rate from facial videos. Our proposed method estimates remote photoplethysmography (rPPG) signals to predict the heart rate. Although there have been proposed several methods for estimating rPPG signals, most previous methods can not be utilized in low-power single board computers due to their computational complexity. To address this problem, we construct a lightweight student model and employ a knowledge distillation technique to reduce the performance degradation of a deeper network model. The teacher model consists of 795k parameters, whereas the student model only contains 24k parameters, and therefore, the inference time was reduced with the factor of 10. By distilling the knowledge of the intermediate feature maps of the teacher model, we improved the accuracy of the student model for estimating the heart rate. Experiments were conducted on the UBFC-rPPG dataset to demonstrate the effectiveness of the proposed method. Moreover, we collected our own dataset to verify the accuracy and processing time of the proposed method on a real-world dataset. Experimental results on a NVIDIA Jetson Nano board demonstrate that our proposed method can infer the heart rate in real time with the mean absolute error of 2.5183 bpm.

• Journal of environmental and Sanitary engineering
• /
• v.11 no.2
• /
• pp.65-73
• /
• 1996

The objective of this study is to investigate the removal efficiency of volitile organic compounds in soil, and the mechanism of desorption by bench scale microwave heating, Silt soil used for experiment and was impregnated with toluene, tetrachloroethylene, o-xylene and p-dichlorobenzene and the microwave treatment was conducted in a modified domestic microwave oven : 2450MHz, 700W. According to the results of the research the removal efficiency was improved with increasing water contents and the soil temperature appeared to plateau period extending to 2-3minutes corresponds to the temperature a which steam distillation was expected. The value of removal rate constant (k) were calculated on dry and moisty silt soil, respectively, which showed linear with increasing microwave heating time. Therefore, addition of a certain amount of water to the contaminated soil can efficiently enhance the ability of the soil to absorb microwave energy and promote the evaporation of the volitile contaminants.

• Nuclear Engineering and Technology
• /
• v.4 no.2
• /
• pp.109-115
• /
• 1972

The evolution of radioiodine 131I from a sodium peroxide system as a function of time, temperature, and carrier gas (nitrogen) flow rate was studied. Virtually no iodine was volatilized at 25$0^{\circ}C$ and a very small amount, of the order of 10$^{-3}$ % per flour, at 63$0^{\circ}C$. Substantially greater amounts of iodine were volatilized at 7$25^{\circ}C$ and 83$0^{\circ}C$. The data are consistent with the hypothesis that the mechanism of transfer is distillation of sodium iodide, and that elemental iodine is not produced in this system.

• Polymer(Korea)
• /
• v.29 no.1
• /
• pp.64-68
• /
• 2005

To recycle collected high-impact polystyrene (HIPS) wastes as liquid fuel, depolymerization characteristics of HIPS by pyrolysis was studied. The effects of temperature and time on the pyrolysis of HIPS were investigated. The depolymerization temperature and activation energy of HIPS pyrolysis increased with increasing heating rate. In general, conversion and liquid yield gradually increased with pyrolysis temperature and pyrolysis time. Each liquid product formed during pyrolysis was classified into gasoline, kerosene, light oil and heavy oil according to the distillation temperature based on the petroleum product quality standard of Korea Petroleum Quality Inspection Institute. As a result, the amount of liquid products produced during HIPS pyrolysis was in the order of gasoline》heavy oil〉kerosene〉light oil. Especially 51${\pm}$6 wt% of HIPS treated was obtained as gasoline.