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RISS 인기검색어
- 검색키워드
- 저자 : Bimlesh Kumar (검색결과 6 건)
- 무료
- 기관 내 무료
- 유료
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Investigations of Mixing Time Scales in a Baffled Circular Tank with a Surface Aerator
Bimlesh Kumar,Ajey Patel,Achanta Rao 대한환경공학회 2011 Environmental Engineering Research Vol.16 No.1
The oxygen transfer rate is a parameter that characterizes the gas-liquid mass transfer in surface aerators. Gas-liquid transfer mechanisms in surface aeration tanks depend on two different extreme lengths of time; namely, macromixing and micromixing. Small scale mixing close to the molecular level is referred to as micromixing; whereas, macromixing refers to mixing on a large scale. Using experimental data and numerical simulations, macro- and micro-scale parameters describing the two extreme time scales were investigated. A scale up equation to simulate the oxygen transfer rate with micromixing times was developed in geometrically similar baffled surface aerators.
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Shape effect on optimal geometric conditions in surface aeration systems
Bimlesh Kumar,Ajey Kumar Patel,Achanta Ramakrishna Rao 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.1
The performance of surface aeration systems, among other key design variables, depends upon the geometric parameters of the aeration tank. Efficient performance and scale up or scale down of the experimental results of an aeration system requires optimal geometric conditions. Optimal conditions refer to the conditions of maximum oxygen transfer rate, which assists in scaling up or down the system for commercial utilization. The present work investigates the effect of an aeration tank's shape (unbaffled circular, baffled circular and unbaffled square) on oxygen transfer. Present results demonstrate that there is no effect of shape on the optimal geometric conditions for rotor position and rotor dimensions. This experimentation shows that circular tanks (baffled or unbaffled) do not have optimal geometric conditions for liquid transfer, whereas the square cross-section tank shows a unique geometric shape to optimize oxygen transfer.
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Design considerations and economics of different shaped surface aeration tanks
Bimlesh Kumar,Achanta Ramakrishna Rao 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.6
This paper deals with the design considerations of surface aeration tanks on two basic issues of oxygen transfer coefficient and power requirements for the surface aeration system. Earlier developed simulation equations for simulating the oxygen transfer coefficient with theoretical power per unit volume have been verified by conducting experiments in geometrically similar but differently shaped and sized square tanks, rectangular tanks of length to width ratio (L/W) of 1.5 and 2 as well as circular tanks. Based on the experimental investigations, new simulation criteria to simulate actual power per unit volume have been proposed. Based on such design considerations, it has been demonstrated that it is economical (in terms of energy saving) to use smaller tanks rather than using a bigger tank to aerate the same volume of water for any shape of tanks. Among the various shapes studied, it has been found that circular tanks are more energy efficient than any other shape.
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Performance comparison of batch and continuous flow surface aeration systems
Bimlesh Kumar,Achanta Ramakrishna Rao 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.6
The oxygen transfer rate and the corresponding power requirement to operate the rotor are vital for design and scale-up of surface aerators. The aeration process can be analyzed in two ways such as batch and continuous systems. The process behaviors of batch and continuous flow systems are different from each other. The experimental and numerical results obtained through the batch systems cannot be relied on and applied for the designing of the continuous aeration tank. Based on the experimentation on batch and continuous type systems, the present work compares the performance of both the batch and continuous surface aeration systems in terms of their oxygen transfer capacity and power consumption. A simulation equation developed through experimentation has shown that continuous flow surface aeration systems are taking more energy than the batch systems. It has been found that batch systems are economical and better for the field application but not feasible where large quantity of wastewater is produced.
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Mass transfer and shear rate in baffled surface aerator
Bimlesh Kumar,Ajey Kumar Patel,Achanta Ramakrishna Rao 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.2
The scale up or scale down of the process variables in a surface aerator requires information about the shear rate prevailing in the system. In fact, the performance of surface aerator depends upon the shear rate. Shear rate affects the mass transfer operation needed by the surface aerator. Theoretical analysis of shear rate suggests a nonlinear behavior with rotational speed of the impeller, which has been shown in the present work. Present work also shows that in a geometrically similar system of baffled surface aerator, shear rate can be used as a governing parameter for scaling up or down the mass transfer phenomena.
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Scale up criteria for dual stirred gas-liquid unbaffled tank with concave blade impeller
Thiyam Tamphasana Devi,Bimlesh Kumar 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.8
Experimental investigation has been done in unbaffled gas-liquid stirred tanks using dual concave bladeimpeller to analyze the mass transfer, power consumption and gas holdup. Optimal impeller clearance has been suggestedfor lower and upper impeller based on maximum mass transfer rate. Numerical modeling has been done to analyzethe flow pattern for different combinations of impeller clearance. The lower impeller positioned at 0.3 of tank diameterand clearance between lower and upper impeller at 0.4 of tank diameter gave the maximum mass transfer coefficient. Scale-up criteria for mass transfer rate, power and gas holdup have been developed for optimal geometrical similarsystems of unbaffled stirred tanks with dual concave impeller.
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