External Circulation Fluidized Bed Heat Exchanger Design And Heat Transfer Performance Experimental Research

External circulating fluidized bed heat exchanger takes advantages of wide range of flow rates,and higher heat transfer coefficient at low flow rates.However,up to now the design and related experimental research of integrated exterior circulating fluidized bed heat exchanger is still in the blank.Based on the widely used shell and tube heat exchanger in industry this research actually designed and constructed a complete external circulating fluidized bed heat exchanger,and studied the flow and heat transfer performance with this experimental bench of external circulating fluidized bed heat exchanger.Firstly,with theoretical analysis and experiment research,the inert solid particles used in the external circulating fluidized bed heat exchanger is examined to study its flow velocity in liquid.By Ergun equation and drag force formula the physical quantity affected solid fluidization velocities are listed.The liquid-solid fluidization experiment gave the initial and terminal fluidization velocity by using seven kinds particles.By curve fitting this paper corrected initial fluidization velocity calculation equation,and verified the formula of terminal fluidization velocity based on the experiment data.Secondly,based on the above theoretical analysis and experimental results,an external circulating fluidized bed heat exchanger using industrial shell and tube heat exchanger structure is designed and built.The exchanger is designed as a water-steam condenser referring to a conventional fixed tubesheet shell and tube heat exchanger.All parts of the external circulating fluidized bed exchanger are designed combining with the terminal fluidization velocity of solid particles.The size of external circulating fluidized bed exchanger inlet plenum,seperator,circulating pipes and back-mixing spout is analyzed in detail considering the size structure and the experimental limited conditions.Third,the performance of cold flow characters on external circulating fluidized bed heat exchanger is tested.With theoretical analysis,the flow pressure drop of the external circulating fluidized bed heat exchanger is divided into three parts:(1)The flow pressure drop loss caused by fluidized solids particle mass in the heat exchanger;(2)The inlet plenum,vents and other parts of the pressure drop;(3)Pressure drop along the flow in the heat exchange bundle tube.By simultaneous recording the external circulating fluidized bed exchanger global and local flow pressure drop,flow pressure loss empirical equation obtained in coefficient calculation.Finally,the total heat transfer coefficient of external circulating fluidized bed was experimentally investigated.By using Wilson graphical method,the tube outer convection heat transfer coefficient,tube wall thermal conductivity and the inner tube wall convection heat transfer coefficient were calculated by the experiment data.With the global optimization method,external circulating fluidized bed heat exchanger optimum operating conditions is determined.In fouling experiment,the calcium carbonate was used as the tube medium to test the heat exchanger overall heat transfer coefficient.The research results showed that the overall heat transfer coefficient of external circulating fluidized bed heat exchanger is efficient than conventional heat exchanger in adequate operation condition,and external circulation fluidized bed heat exchanger modification has solid economical value.