Study On Low Temperature Multi-effect Distillation With Thermal Vapor Compression

As MED-TVC(low-temperature multi-effect distillation with thermal vapor compression)has some technical advantages through the possibility of utilizing low temperature waste heat sources, increasing gained output ratio and reducing water cost, it was studied In the dissertation .The heat transfer coefficients inside and outside the horizontal tube were summarized. Not only the effects of tube diameter, inlet vapor velocity, steam condensing temperature and outlet vapor quality on the inside heat transfer coefficient, but also the effect of overall heat transfer temperature difference and flow density on the outside heat transfer coefficient were studied and compared. On these basis, the overall heat transfer coefficient was calculated in terms of different fouling resistance.Based on the mass and energy equations, the physical model and mathematic model of 6 different kinds of MED-TVC was established. Equal-area design method the mathematic model was solved through Equal-area design method combined Gauss-Jordan elimination. By using Visual Basic programming language, the MED-TVC calculation software was worked out which had better generality, friendly interface and re-embeddability. Both design calculation and check calculation can be done by the software.The effect of the feed seawater temperature, the heating steam temperature of NO.1 evaporator, the concentration ration, the steam extraction, the quantity and location of preheat flow, the form of TVC on performance of a distiller is discussed. Not only serial flow and parallel flow, but also system with and without TVC was compared. Synthetically, 4+2 parallel flow showed the best performance among the 6 flows.The conclusions provide a significant guidance in the specific extent of engineering.