Flow Characteristics in a Honeycomb Structure to Design Nanobubble Generating Apparatus

Abstract

A nanobubble generator with honeycomb structures producing a large amount of water including large nanobubble density in a short time is described. The nanobubble-generating performance is investigated for large and small apparatus having different honeycomb cell dimensions by applying computational fluid dynamics (CFD) coupled with a population balance model (PBM). The CFD simulation shows that a significant pressure drop and shear stress occur in the bubbly flow in the honeycomb cell. The numerical model is based on the Eulerian multiphase model and the PBM is used to calculate the bubble size distribution. The obtained CFD-PBM results are compared with the experimental results for large and small apparatus. Bubble size distributions in the honeycomb structure under different inlet absolute pressure can be predicted by the PBM. The maximum shear stress is determined as the main controlling factor for nanobubble generation.

Untapped Potential: Applying Microbubble and Nanobubble Technology in Water and Wastewater Treatment and Ecological Restoration

“…94 Thus, the use of MB and NB technology for aeration in ASP can significantly improve oxygen mass transfer and overall DO. 95−98 The volumetric gas−liquid mass transfer coefficients for MB-and NB-aeration are several times higher than those reported for conventional aeration (e.g., 0.29/min for a MB-sparger 88 and 0.042/min and 0.12/min for conventional aeration and MB-aeration, respectively 91 ). Due to high interior pressures in MBs and NBs, the concentration of dissolved gases in the bulk liquid is much higher than the corresponding gas saturation concentrations (i.e., gas solubility).…”

“…In addition to cavitation, electrolysis, − porous material, ,− and fluidic oscillators − were also used for MB and NB generation. More recently, some integrated techniques, e.g., by combining a centrifugal multiphase pump with a needle valve and by using generators with a honeycomb structure, , have been employed to generate MBs and NBs. More details of various MB and NB generation methods can be found in several recent reviews ,,, and are not discussed here.…”

“…Intensive aeration is required to maintain high DO due to the poor oxygen transfer efficiency of currently employed aeration technology . Thus, the use of MB and NB technology for aeration in ASP can significantly improve oxygen mass transfer and overall DO. − The volumetric gas–liquid mass transfer coefficients for MB- and NB-aeration are several times higher than those reported for conventional aeration (e.g., 0.29/min for a MB-sparger and 0.042/min and 0.12/min for conventional aeration and MB-aeration, respectively). Due to high interior pressures in MBs and NBs, the concentration of dissolved gases in the bulk liquid is much higher than the corresponding gas saturation concentrations (i.e., gas solubility). , For instance, Hamamoto et al reported that the DO in water after 45 min aeration of O 2 -NBs was 60 mg/L, approximately 7-fold higher than the oxygen solubility under ambient conditions .…”

Population Balance Modeling and Multi‐Response Optimization of a Swirling‐Flow Nanobubble Generator

“…In our previous study [14], computational fluid dynamicspopulation balance method (CFD-PBM) coupled simulation could predict the bubble size distribution involving several combinations of the bubble coalescence and breakage models. This model can determine the flow characteristics during bubble generation and predict the bubble size distribution up to Hilman Syaeful Alam the nanometer scale [15,16]. The purpose of this study is to combine the CFD-PBM coupled model and RSM in producing the design of a swirlingflow nanobubble generator with optimum performance.…”