Research On Mixing Characteristics And Structure Optimization Of An Open Pond With Serpentine Channel

The use of microalgae as a raw material for the production of biodiesel is a sustainable biomass energy technology.Microalgae cultivation can utilize carbon dioxide and nitrogen oxides in industrial waste gas to alleviate greenhouse gas emissions and reduce environmental pollution.In addition,compared with diesel,biodiesel has good fuel performance and safety performance,and also has low environmental pollutants such as low sulfur dioxide and sulfide emissions and no aromatic alkanes.Therefore,the use of microalgae to produce biodiesel is an efficient,clean and environmentally friendly new energy utilization pathway with broad development potential.At present,the microalgae culture system is mainly composed of an open culture system and a closed photobioreactor.The open microalgae system has the characteristics of relatively low cost,low operating cost and easy amplification,and is suitable for commercial large-scale energy micro-Production of algae.The traditional open-type runway pool is driven by the paddle wheel to mix and flow the algae liquid in the runway.This circulation mode causes the turbulent flow to exist only in the flow field near the paddle wheel,and the rest of the area is still in the laminar or dead zone state,which is not conducive to sufficient Use sunl ight resources.At the same time,the recovery cost of the runway pool is high and it is easy to be affected by seasonal changes and temperature difference between day and night to further restrict the cultivation efficiency of microalgae.Aiming at the problems faced by traditional runway pools,this paper studies a new type of open serpentine channel microalgae culture system,which improves the flow mixing unevenness and diurnal heat loss by comprehensive design of channel culture tank and microalgae collection pool problem.Previously,researchers have made initial progress on flow field velocity,channel structure design and mixing strength.The key parameters such as dam spacing and dam length of the new channel pool have not been optimized.Therefore,this study applied computational fluid dynamics technology to model the channel pool and optimize the internal structure,and compared the simulation results with the experiment.The two-phase flow VOF model and the standard turbulence model are used to calculate the model,and the flow velocity is defined as the flow dead zone.The particle trajectory tracking method is used to quantify the vertical zone mixing time and the light-dark average cycle time of the microalgae particles in the channel pool.Then,the flow mixing characteristics of the relative spacing of the channel dams are compared with those of the channel dams.The results show that the relative spacing of the channel dams and the relative length are the best for the dead zone area and photosynthesis efficiency.The vertical mixing intensity in the channel pool is very important for the microalgae culture.In this paper,a device with a diagonal baffle is used to strengthen the vertical mixing in the channel pool,and the orthogonal oblique test method is used to analyze the optimal oblique baffle structure.