Heat Transfer Performance And Structure Optimization Of The Evaporator With Double Chambers And Double Tube Passes

The evaporator with double chamber double tube pass inherits the advantages of themulti-effect evaporation, compared with single chamber and tube evaporator has betterheat transfer performance, especially for the enrichment process significantly increasesthe viscosity of the liquid feed system, can reduce the material liquid in evaporation cyclepower consumption. At the same time, for the evaporator with double chamber doubletube pass, liquid into the separation chamber to achieve a uniform distribution, one canachieve better vapor-liquid separation, it can also improve system efficiency ofevaporation, to ensure stable flow between the double chamber. In this regard,first of all,the issue under different conditions, through the experimental analysis and comparison ofthe effects of liquid viscosity on heat transfer performance; On this basis, in order tofurther optimize the performance of the evaporator with double chamber double tubepass,but also by numerical simulation method to analyze the structure of the existingseparation chamber, dual-chamber flow field, temperature and concentration fields; Forthe current lack of uniformity in the structure of the flow field, temperature field andconcentration field separation chamber, proposed six kinds of structural improvementprogram, and simulation analysis of the separation chamber flow field, temperature field,concentration field and its uniformity, to determine an optimum structure and were in adifferent separation chamber of import feed speed and feed viscosity investigation andverification of the uniformity of the structure.To study the liquid system whose viscosity increases in the process of enrichment,anew type evaporator with double chambers and double tube passes was built.Experimenthas been carried out to analyze the heat transfer performance under varable viscosity from1.01~10.80mPa s,by using glycerol-water as the working fluid. The results shows that the operating mode of single separation chambers and single tube passes,double separation chambers and single tube passes and double chambers and double tube passes is realizable on the structure of double chambers and double tube passes. But the heat transfer performance under the operating mode of the double chambers and double tube passes is bett er than that under operating mode of the double separation chambers or double tube passes. The heat transfer performance of the double chambers and double tube passes can be further improved when a certain amount of inert solid particles is introduced into the heating tube to develope the form of the vapor-liquid-solid fluidization. When particle diameter is4~6mm, the average heat transfer coefficient of the double chambers and double tube passes decreases along with the going high of particle diameter; When particle volume fraction is less than2.06%, the average heat transfer coefficient increases along with the going high of particle volume fraction; when the particle volume fraction increased to3.01%, the average heat transfer coefficient presents a downward trend.Simulation analysis on the evaporator with double chamber double tube pass ofseparation chamber flow field, temperature field, concentration field show that, in theoriginal separation chamber structure, after the material liquid into the separationchamber is easy to form a short-circuit flow, resulting in poor uniformity of temperature,concentration distribution of double chambers, and by reasonably setting the separationchamber liquid inlet angle can significantly improve the concentration distribution ofseparation chamber, in which the optimal structure for the separation chamber (1) ofthe horizontal tangential feet inlet1is30°, separation chamber (2) the feet inlet2horizontal tangential is45°, In the material liquid inlet velocity of0.2to0.2m/s,glycerine-water solution concentration was20%-60%of the conditions, the separationchamber axial regional concentration difference maintained within4%, the radial feeddomain regional concentration difference maintained within1%.