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코일이 삽입된 수평원관내의 강제대류 열전달 특성에 관한 연구
박내현,이계한 明知大學校 産業技術硏究所 1997 産業技術硏究所論文集 Vol.16 No.-
An experimental work is performed in order to study the heat transfer and pressure drop characterastics in coil ribbed circular tubes. The heat transfer and pressure drop in coiled ribbed tubes are increased for Reynolds numbers of 10,000∼40,000. The dimensionless geometric parameters are pitch to height ratio(p/e), efficiency index(η) and the flow attack angle(α). test section was electrically uniformly heated and the pressure drop across the test section was obtained by a differential pressure transducer. In order to verify the accuracy of our experimental methods, the friction factor and heat transfer coefficient were determined for a smooth tube and showed good agreements with previous workers results. Experiments were performed for coil ribbed tubes which had different pitch to height ratios(5,10, and 15). Both the Stanton number and friction factor have maximun values when the pitch to height ratio of the rib was five. As Reynolds number increased, the 'efficiency index', (η≡(St/Sts)/(f/fs)) decreased. A performance comparison showed that heat transfer in the coil ribbed circular tube with a 15 pitch to height ratio was the best for the same friction power.
Factors Affecting the Growth of Coriolus versicolor in a Submerged Culture
김병각,이재흥,유무영,오광근,류근갑,박내현 한국균학회 1987 韓國菌學會誌 Vol.15 No.2
Various fermentation parameters were investigated to maximize the mycelial growth of Coriolus versicolor (Fr.) Quel in a submerged culture. These included pH, temperature, agitation speed and aeration rate. The broth pH was found to be very important for growth of the fungi and the optimal range was between 5.0 and 5.5. However, the culture temperature showed insignificant effects on the growth between 25 and 32℃. Both agitation speed and aeration rate affected the morphology and the final concentration of the mycelium. It was also found from shake flask culture experiments that Coriolus versicolor could utilize molasses. Macronutrient (i.e., glucose, yeast extract and molasses) concentrations of the fermentation medium were optimized by the experimental factorial design and response surface method.
경사지게 설치된 평행류형 알루미늄 열교환기의 공기측 전열 성능
김도영(Do-Young Kim),조진표(Jin-Pyo Cho),김내현(Nae-Hyun Kim),박내현(Nae-Hyun Park),황준현(Jun-Hyun Hwang) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.3
The effect of inclination angle on the heat transfer and pressure drop characteristics of the brazed aluminum heat exchangers is experimentally investigated. Three samples having different fin pitches (1.25, 1.5 and 2.0 ㎜) were tested. Results show that heat transfer coefficient is not affected by the inclination angle. However, the friction factor increases as the inclination angle increases with negligible difference between the forward and backward inclination. Both the heat transfer coefficient and the friction factor are the smallest at Fp=1.5㎜, followed by Fp=2.0㎜ and 1.25 ㎜. Possible explanation is provided considering the louver layout. Comparison with existing correlations is also made.
박영민(Youngmin Park),정영만(Youngman Jeong),이재근(Jaekeun Lee),박내현(Naehyun Park) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
Finned-tube heat exchangers are often made with aluminum fins and copper tubes. Usually the contact between fin collar and tube surface for finned tube heat exchanger is secured by mechanical expansion of the tubes. The objective of the present study is to apprehend how much effect clearance has on the performance of heat exchanger. This effect is studied using an experimental approach. The thermal fluid measurements are made using a psychometric calorimeter. Frontal air velocity varies in the range from 1.0m/s to 3.0 ㎧. The heat transfer rate of sample which has bigger clearance is only 27% compare with the other’s in dry condition. In wet condition, its heat transfer rate is 78% compare with the other’s.
핀-튜브 열교환기에서 PVE오일이 증발/응축 열전달 성능에 미치는 영향
이현우(Hyunwoo Lee),정영만(Youngman Jeong),이재근(Jaekeun Lee),박내현(Naehyun Park) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
In vapor compression systems which use refrigerant as a working fluid, the oil is commonly used for compressor lubrication. Since the presence of lubrication oil can change the characteristics properties of refrigerant, the oil affects the heat transfer performance of heat exchanger to a large extent. In this paper, we focus on the effect of PVE oil experimentally on heat transfer performance of the fin-tube heat exchangers which use R410A as a refrigerant. To evaluate the heat transfer performance, the refrigerant to air type test facility chamber has been used. Fin-tube heat exchanger with grooved has been tested while according to the oil mass fraction variation from nearly zero to 1.7 wt%. It was found that the low level of oil mass fraction has an obvious effect on heat transfer performance, while the high level seems no significant influence. The influence of the oil mass fraction to heat transfer performance, however, is different between evaporation and condensation.
마이크로채널 튜브를 사용한 알루미늄 응축기의 패스 수에 따른 열전달 및 압력강하 특성 연구
염새나(Saina Yan),박영민(Youngmin Park),정영만(Youngman Jeong),이재근(Jaekeun Lee),박내현(Naehyun Park) 대한설비공학회 2010 대한설비공학회 학술발표대회논문집 Vol.2010 No.6
The heat transfer rate and refrigerant pressure drop of 4 aluminum microchannel tube condensers with different pass number (4, 6, 8, 12) have been tested. As a comparison, the performance of one conventional round tube heat exchanger has also been examined. The experiment results showed that the heat transfer rate increased with the pass number increasing. The 12-pass microchannel tube condenser had the highest heat transfer rate and showed 11.8% higher than the conventional round tube heat exchanger under the same test condition. And the largest refrigerant pressure drop also happened in the 12-pass microchannel tube condenser according to the front air velocity range. Finally, the pressure drop under the same refrigerant mass flow rate of 80 kg/h was presented. The results showed the pressure drop of the 12-pass microchannel tube condenser was 18 times larger than the 4-pass one.