Numerical Simulation And Design Optimization Of Condensing Heat Exchanger Based On Gas Generator

The gas turbine generator is a kind of widely used facility in social life,but its thermal efficiency is only 30%-40%because most heat is carried away by cooling water and exhaust gas.Thereby,it wastes hugely.There are so many kinds of waste-heat utilization,no matter which way,efficient heat exchange equipment is fundamentalrequest of waste-heat utilization with gas turbine generator.Consider condensing waste-heat exchanger with normal exchanger,it can condense the vapor in the exhaust gas and release latent heat in vapor.Then the exhaust gas temperature has decreased and waste-heat utilization ratio has been increased,and harmful substances in the flue gas emission reduction.It has the advantages of energy saving and environmental protection,therefore,this paper chooses the condensing heat exchanger as the heat exchanger to recover the heat of the waste gas.This article describes a waste-heat utilization design of the gas turbine generators with real situation,including the selection of cooling water and flue gas recovery heat exchanger and arrangement of the whole system,get the waste-heat utilization system diagram finally.Analysing condensation heat transfer model of waste gas,choosing the appropriate heat transfer coefficient.According to condensing exchange characters of exhaust gas,the article establishes mathematical model and show the physical design of condensing waste-heat utilization exchanger by known conditions.3D physical model of exchanger is created by Gambit,the computational fluid dynamics'(CFD)pretreatment software.Then the grid is divided and initial boundary conditions are set up all by it.The Fluent is used to set up the characters of materials and boundary conditions,choose suitable turbulence model and multi-phase model,and compile the user defined files(UDF).With solution procedure of coupling heat and mass transfer,we can draw a conclusion to simulation,get the distribution diagrams of exhaust gas side' temperature,velocity and pressure,and get the different parameters'(such as inlet velocity,temperature and so on)influence of exchangers'performance(such as coefficient of heat transfer and thermal efficiency).The result of simulation indicatesvariation trendof exhaust gas by analyzing-distribution diagrams of exhaust gas side' temperature,pressure and velocity,so that we can find some problems in exchangers and optimize structure.Different parameters have great influence on heat exchange performance.Increasing the inlet water flow can enhance the coefficient of heat transfer and thermal efficiency of heat exchanger,however,the import and export pressure greatly increased and the outlet water temperature decreased significantly.Therefore,it need to choose the inlet water flow reasonablely.Reduction of inlet water temperature result in reduction of the whole water temperature.So condensation area increases and more latent heat is released.Thermal efficiency are improved.When gas velocity increases,sensible heat exchange between gas and tubes weakens,flue gas loss holds more proportion of heat load,thermal efficiency drops,and the differential pressure of inlet/outlet increases slightly.With the content enhancement of vapor,the coefficient of heat transfer and thermal efficiency all rise.Increasment of water vapour content enlarge its partial pressure,so condensation effect is better,the latent heat holds more proportion of heat load and thermal efficiency is improved obviously.The design calculation and process programming of condensing exhaust heat exc hanger in this article is based on gas generators.It has reference value on design calcul ation of condensing exhaust heat exchanger in gas engine and other similar eq-uipme nt.With analysis on CFD's simulation consequence,we can get different param-eters'influence on heat exchanger's thermal efficiency and coefficient of heat transfer.Andit has theoretical guiding significance on design and optimization of condensing exhaust heat exchanger.