Thermodynamics Optimization On Exchangers Network And Shell And Tube Exchangers

With the rapid development of economy, resource consumption hasincreased more and more. According to scientific development view,transforming of economic growth pattern, constructing energy-saving andenvironment-friendly society and realizing sustainable development are allnecessary. The goal of energy-saving by 2010 has been put forward clearlyin the outline of'11th five-years planning'-energy consumption in unitGDP should be decreased by 20%.Enterprises consuming large proportion energy should takeenergy-saving and emission-reducing as the primary task and they eagerlyhope to make use of the exiting energy resource to the greatest extent.However, the energy streams of producing process are more complicatedto be arranged reasonably, so it is necessary to optimize the whole energyutilization system, find the optimal matching program and realize theenergy cascade utilization from the global perspective. Besides, as theindispensable part, heat exchangers are the very normal equipment for thechemical production process and refrigeration systems, and there are manyvarious categories and models. But how to reasonably evaluate theperformance of heat exchangers is the main topic for some scholars.Falling film evaporators have also been used in Food, Chemical, Seawaterdesalination industry etc and its application technology is more mature inthese industries. But there is no unified designing method for falling filmevaporator; moreover some influence factors are not compressive.This paper has made some simulation calculations to heat exchangenetwork and falling film evaporator by computer modeling and simulationtechnologies, and finally got the methods of optimizing heat exchanger network and evaluating thermodynamic properties for falling filmevaporator. In addition, the analyses have applied the concepts of exergyand entranspy as well.Firstly, as for heat exchange network, the optimization of energyutilization should be combined with many factors, such as energy structure,seasonal factors, employment of technologies with low energy consuming,reasonableness in energy utilization etc. This paper shows an example forprocess synthesis extending traditional pinch analysis with situation ofenergy utilization in different seasons. According to the optimizationanalysis, the energy consumption would be decreased apparently after theenergy integration over the year and the adjustment of the consumptionstructure of energy.Secondly, as for the falling film evaporator, this paper has establisheda thermal design model and a structure design model by Fortran Languageon the basis of heat transfer performance experiment of falling filmevaporation and simulation research material. And then an optimal tubearrangement combination is gained by iterating a numerical simulationprogram which is established based on distributed parameters for fallingfilm evaporator.At last, a simulation based on CFD technology (Fluent) has beendeveloped, and the results have shown that maldistribution of chilled wateris very serious in the vertical direction of tubes and it is proved that thisphenomenon severely deteriorated the process of heat transfer. At last, toimprove the distribution uniformity of chilled water, an improved structurewith second-level distributor is introduced, and the results show that theuniformity is much better than before. Besides, it is discussed that themaldistribution of mass flow has serious negative impacts to heat transferof falling film evaporator by the theory of entranspy.