• 대한기계학회논문집B
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• 제39권10호
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• pp.817-824
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• 2015

본 논문은 수직 오리피스 노즐의 유동 및 물질전달 특성에 대한 실험적 연구를 목적으로 한다. 구동유체 및 부유체의 유량, 용존산소 농도 그리고 소비 전력을 측정하였으며, 고속 카메라를 이용한 직접 촬영 기법으로 수직 혼합유동의 가시화 이미지를 획득하였다. 측정자료를 이용하여 질량비, 총괄 산소전달 계수 그리고 물질전달 성능계수를 도출하였다. 구동압력이 증가하면 질량비는 약간 감소하는 반면에, 산소전달 계수와 소비전력은 증가하였다. 구동압력이 증가하고 질량비가 작아지면, 기포의 미세화가 촉진되고 확산도가 증대되기 때문에 산소 전달율이 증가하였다.

• 한국수산과학회지
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• 제11권4호
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• pp.205-211
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• 1978

The effect of phenol derivatives (guaiacol, vanillin, o-vanillin, eugenol) and catechol derivatives (pyrogallol, resoicinol) to enhance the volumetric oxygen transfer coefficient, in the aerobic fermentation was studies. Guaiacol, vanillin, o-vanillin, pyrogallol and resorcinol revealed to enchance the volumetric oxygen transfer coefficient, and eugenol had no such ability. The enhancement of the oxygen transfer ability is probably due to the formation of the charge transfer complex by the derivatives and oxygen molecules.

• 한국환경과학회지
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• 제6권1호
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• pp.25-31
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• 1997

The variations of gas hold-up, overall volumetric oxygen mass transfer coefficients and liquid circulation velocity in an internal loop reactor were investigated to manifest scale-up effect. The relationship between superficial gas velocity and gas hold-up were found as Ugr = 0.045 $\varepsilon$r in the pilot-scale and Ugr = 0.056 $\varepsilon$r in the bench-scale reactor. The overall volumetric oxygen mass tractsfer coefficient, KLa was slightly increased in the pilot-scale than in the bench-scale reactor. Flow regime was changed from the bubble flow to the churn-turbulent flow when the superficial gas velocity reached to 3.5 - 4 cm/sec in the pilot-scale.

• Journal of Advanced Marine Engineering and Technology
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• 제35권5호
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• pp.640-646
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• 2011

용존산소는 물속에 용해되어 있는 산소량으로 수질의 지표가 된다. 본 논문은 이젝터-폭기 시스템의 용존산소특성에 미치는 염도의 영향에 대한 실험적 연구를 목적으로 한다. 이젝터-폭기 시스템은 모터-펌프, 이젝터, 모터-블로어, 폭기 및 순환수조, 제어판넬 등으로 구성된다. 처리수의 용존산소량은 염도가 증가함에 따라 감소하였으며, 산소전달율의 정량적인 변수인 총괄 물질전달계수는 염도가 증가함에 따라 증가하였다.

• International Journal of Fluid Machinery and Systems
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• 제5권1호
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• pp.10-17
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• 2012

The objective of this study was to investigate the oxygen transfer characteristics of an ejector aeration system. In order to evaluate the oxygen transfer performance of the ejector aeration system, a comparative experiment was conducted on a conventional blower aeration system. The effect of entrained air flow rate and aerating water temperature on the oxygen transfer efficiency was investigated. The dissolved oxygen concentration increased with increasing entrained air flow rate, but decreased with increasing aerating water temperature for two aeration systems. The volumetric mass transfer coefficient increased with increasing entrained air flow rate and with increasing aerating water temperature for both aeration systems. The average mass transfer coefficient for the ejector aeration system was about 20% and 42% higher than that of the blower aeration system within the experimental range of entrained air flow rates and aerating water temperatures.

• Environmental Engineering Research
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• 제21권3호
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• pp.233-240
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• 2016

The research aims to study the different flexible rubber tube diffusers used in urban wastewater treatment processes and aquaculture systems. The experiment was conducted in small-scale aeration tank with different physical properties of the tubes that were used as aerators. The volumetric mass transfer coefficient ($k_La$), oxygen transfer efficiency (OTE) and aeration efficiency (AE) were measured and determined to compare the diffusers. Moreover, the bubble hydrodynamic parameters were analyzed in terms of bubble diameter ($d_B$) and rising velocity ($U_B$) by a high speed camera (2,000 frames/s). Then the interfacial area (a) and liquid-side mass transfer coefficient ($k_L$) can be calculated. The physical properties (tube wall thickness, tensile strength, orifice size, hardness and elongation) have been proven to be the key factor that controls the performance (kLa and OTE). The effects of hardness and elongation on bubble formation, orifice size and a-area were clearly proved. It is not necessary to generate too much fine bubbles to increase the a-area: this relates to high power consumption and the decrease of the kL. Finally, the wall thickness, elongation and hardness associated of the flexible tube diffuser (tube No. 12) were concluded, to be the suitable properties for practically producing, in this research.

• 대한기계학회논문집B
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• 제39권1호
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• pp.61-69
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• 2015

본 논문은 수직 오리피스 이젝터의 혼합유동 및 산소전달 특성에 대한 실험적 연구를 목적으로 한다. 실험장치는 전동 모터-펌프, 오리피스 이젝터, 순환 수조, 공기압축기, 고속 카메라 시스템 그리고 제어 및 측정기기로 구성하였다. 측정된 구동유체 및 유입공기의 유량을 이용하여 유량비를 도출하였다. 이적터에서 분출된 혼합유동의 가시화를 통해 정성적 거동을 고찰하였으며, 용존산소 농도를 측정하여 총괄 산소전달계수를 도출하였다. 구동유체의 유량이 일정하고 압축기의 공기압이 높아지면 유량비와 산소전달계수는 증가하며, 압축기의 공기압이 일정하고 구동유체의 유량이 증가하면 유량비는 감소하지만 산소전달계수는 증가하였다. 기포의 크기에 따른 체류시간 및 확산도와 수직 혼합유동의 도달거리는 2 상의 접촉면적과 시간에 크게 영향을 미치기 때문에 산소전달율의 중요한 변수임을 유추할 수 있다.

• Journal of Microbiology and Biotechnology
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• 제23권10호
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• pp.1445-1453
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• 2013

The scale-up criterion of constant oxygen mass transfer coefficient ($k_La$) was applied for the production of itaconic acid (IA) in a 50 L pilot-scale fermentor by the fungal cells of Aspergillus terreus. Various operating conditions were examined to collect as many $k_La$ data as possible by adjusting the stirring speed and aeration rate in both 5 L and 50 L fermentor systems. In the fermentations performed with the 5 L fermentor, the highest IA production was obtained under the operating conditions of 200 rpm and 1.5 vvm. Accordingly, we intended to find out parallel agitation and aeration rates in the 50 L fermentor system, under which the $k_La$ value measured was almost identical to that ($0.02sec^{-1}$) of the 5 L system. The conditions of 180 rpm and 0.5 vvm in the 50 L system turned out to be optimal for providing almost the same volumetric amount of dissolved oxygen (DO) into the fermentor, without causing shear damage to the producing cells due to excessive agitation. Practically identical fermentation physiologies were observed in both fermentations performed under those respective operating conditions, as demonstrated by nearly the same values of volumetric ($Q_p$) and specific ($q_p$) IA production rates, IA production yield ($Y_{p/s}$), and specific growth rate (${\mu}$). Specifically, the negligible difference of the specific growth rate (${\mu}$) between the two cultures (i.e., $0.029h^{-1}$ vs. $0.031h^{-1}$) was notable, considering the fact that ${\mu}$ normally has a significant influence on $q_p$ in the biosynthesis of secondary metabolites such as itaconic acid.

• Korean Chemical Engineering Research
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• 제47권4호
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• pp.506-511
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• 2009

미생물셀룰로오스의 생산성을 높이기 위하여 원심(centrifugal) 임펠러와 경사원심(inclined centrifugal) 임펠러가 사용되었다. 발효조 내의 유체흐름 형태와 부피산소전달 계수가 고찰되었으며 원심 임펠러 및 경사원심 임펠러가 장착된 발효조 내에서 G. hansenii PJK 균주에 의하여 미생물 셀룰로오스가 생산되었다. 유체는 발효조 하부에서 원심 임펠러의 실린더 내부를 통과하여 발효조 벽면을 향해 순환되었다. 임펠러의 회전속도 100 rpm에서 부피산소전달계수는 터바인 임펠러 계에 비하여 경사원심 임펠러의 경우는 23%, 원심 임펠러의 경우는 15%에 불과하였다. 하지만 미생물셀룰로오스 생산 불능 돌연변이주로의 전환이 방지되어 20 rpm의 경사원심 임펠러의 회전속도에서 미생물셀룰로오스의 생산량이 터바인임펠러의 최적회전속도 300 rpm에서의 미생물셀룰로오스 생산량과 같았다.

• KSBB Journal
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• 제6권3호
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• pp.231-240
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• 1991

Recently, developments of large scale and high density cell culture methods have been the objects of many researches, because the demand of various pharmaceutical products produced by animal cell culture has been rapidly increasing. The cell culture equipment should have the requirements such as sufficient oxygen transfer and mixing, low shear stress and surface tension, and small foaming. In order to develop a proper bioreactor meeting these requirements simultaneously, a perfluorocarbon having high solubility of oxygen was sprayed into the medium as an oxygen carrier instead of air. Also, a new impeller was developed and combined together with the perfluorocarbon spraying system so as to design a new bioreartor for cell cultivation. The new impeller had better characteristics of mixing and oxygen transfer than the paddle and cell-lift impellers based on the same, shear rate. But, it was observed that the volumetric oxygen transfer coefficient of the new bioreactor decreased with increasing cell density during E. coli fermentation.