Numerical Calculation Model and Simulation Optimization of a Effective Speece Cone for Recirculating Aquaculture System
|School||Shanghai Ocean University,|
|Keywords||recirculating aquaculture system Speece cone simulation optimization performance test oxygenation transfer efficiency|
Recirculating aquaculture system is an efficient method of industrializedaquaculture production, using water recycling technology, aeration technology,disinfection technology, temperature， ammonia, nitrogen, salts control and regulationtechnology to achieve integration of the aquaculture and intelligent control, which isbenefit in breeding density, high utilization of water resources, less pollution.It istendency of aquaculture industry in the future.Aeration technology is one of the key technologies of industrial aquacultureprocess. Reasonable and efficientive aeration ways can effectively increase theutilization of the equipment, improve production efficiency and reduce costs. At present,the bubble column is mainly used in the domestic industrial aquaculture as an aerationequipment, which has advantages of simple structure, less technical precision, andmanufacturing convenience and disadvantages of the demand for equipment installationspace and low aeration efficiency. In onther country of aquaculture, aeration equipmentfor industrial aquaculture are mainly using U-tubes, low head oxygen devices andoxygen cones.They have the advantages of high oxygen efficiency, low energyconsumption for different aquaculture system requirements on oxygen supply. In viewof the structural characteristics, aeration methods and effects of the oxygen equipment,an efficient aeration device——pure oxygen cone was designed.Currently, the Speece cone is not widly used in domestic aquaculture aeration. Thisis primarily caused by the undeveloped technology of the Speece cone.The existingmodels can not be widely applied in real practices and are not exact.The performance ofthe cone can only be conjectured by lots of experiments.It needs heavy work and theresults are deeply influenced by the conditions of experiments, therefore the resluts canhardly match by demands of optimal designs and increasing efficiency. According tothe principle and the composition of the oxygenation Speece cone, the present study setup a numerical calculation model of bubble fluid dynamics in aquaculture oxygenationSpeece cone, which is based on balance law of oxygen in water. Furthermore, thesimulation optimization method of Speece cone was developed and applied to designsome Speece cones. By the simulation optimization, designer can predict the oxygenation transfer efficiency and oxygen bubbles dissolution, which concerned withsome dissolved oxygen data such as oxygen concentration, bubble size, and masstransfer coefficient. By comparing those data, the optimization design of dimensions,depth, initial bubble size, flow rate of water and gas can be determined. The efficientoxygen cone theory system established, react the effect on a number of factors impacton the oxygen transfer efficiency for efficient oxygen cone, and determine the influencefunction for each of these factors. Based on the theoretical system, when the theefficient oxygen cone is on work, the aeration efficient can be adjusted and improved bycontrolling the various operating parameters.The simulation optimization program of Speece cone was based on the method offinite differential and enumeration. The program can simulate changes of the variousparameters at different operating times, as well as real-time data of each variable indifferent locations in the aeration cone. The simulation algorithm can alarm errors,unreasonable values of the design variables and possible problems on running. Anddifferent ranges of variable values, the the efficient oxygen cone of the best entry, exitradius, water, the speed of the air intake and optimum aeration cone height can becalculated, resulting in the best optimization program.The simulation optimization program of Speece cone was based on the method offinite differential and enumeration. The program can simulate changes of the variousparameters at different operating times, as well as real data of each variable in differentlocations in the aeration cone. The simulation algorithm can alarm errors, unreasonablevalues of the design variables and possible problems on running. The different ranges ofvariable values, the the efficient oxygen cone of best entry, exit radius, water, the speedof air intake and optimum aeration cone height can be calculated, resulting in the bestoptimization program.Cone structures are designed by changing the position of the oxygen inlet tube forthree options.The oxygen inlet is arranged on the vertical pipe by0.045m from the topof the cone, the central level straight pipe is0.12m from the elbow by0.05m under thetop of the cone. The mixture model and the standard turbulence model in fluentsoftware are applied to simulate the internal fluid field in the Speece cone with differentstructures. The fluid performance in the tubes of the oxygen-water contacting point forvarious cone structure are revealed by velocity distribution and velocity vector ofmultiphase flow. The analysis of the data of numerical simulation indicates that theoptimum structure is the oxygen inlet tube arranged at the lower part of the verticalwater inlet pipe on the top of the cone.Design and make different physical models of pure oxygen aeration cone witn airintake at different position on tne Speece cone.The experimental equipment is mainly composed of pumps, aeration cone, water tank, oxygen tank and dissolved oxygendetection system. Detection system designed by the PLC, dissolved oxygen sensors andcomputer，which can detect the Speece cone on-line.The oxygen transfer experimentproved that the numerical simulation is in the same line with the experimental results.Design a movable supporting means for pure oxygen cone with he movable axleinstalled at the bottom of the aeration cone and design maintenance removal tool.Thebearing puller is designed for its maintenance.The implement is designed mainly inparts as follows: aerodynamical system, chuck, adjustable stroke guide-way, shaftbracket and so on. We developed a new kind of chuck. It is round and can encircle theaxis. Meanwhile, the chuck is adjustable too, so that it can be fit for many kinds ofshafts. Replace the traditional manual disassembly way into the aerodynamical systemto speed up the removement,reduce labor and improve the work efficiency.Through simulation optimization, the design of Speece cone was simplified, thedimensions were optimized and the performance was improved. Based on oxygenbubble dynamics theory, this study established the optimization method of Speece conedesign and verified by some Speece cone experiment. The optimization method canprovide reliable design for efficient oxygenation Speece cone in recirculatingaquaculture system.