The Design Calculation And Numerical Simulation Of 300MW Unit Low Pressure Heater

Before the opening of world climate conference, the Chinese government promised by 2020 the carbon dioxide emission of unit GDP will be reduced by 40-45% compared with that in 2005. This goal was far higher than 17% announced by US, and the highest emission reduction goal the European offered was 30%. In the future China will use its coal mainly for power generation, coal-firing power stations will thus become the main source of CO2 emission. The efficiency of boiler is about 90% from the thermal equilibrium point, but lowered to about 64.02% by the measurement of avaliable energy, because of the temperature difference between water and high temperature fume. Heat regeneration cycle is one of the measurements to raise the efficiency of boiler. Low pressure heat exchanger for heat regeneration is the core equipment of heat regeneration system and its running state has important influence on the system efficiency and safety.The design calculation of heat exchanger includes thermal calculation, structural calculation, flow resistance calculation and strength calculation. The mission took no consideration of strength calculation.Programed the Visual Basic program to complete the thermal calculation, structural calculation and flow resistance calculation, and drew space patterns according to the final results. The method of structural calculation referred to the《The Principle and Design of Heat Exchanger》, Shi Meizhong, Wang Zhongzheng (4th edition) the second chapter section2.2; Tubular heat exchanger thermal calculation referred to the same book, the second chapter section2.3; Tubular heat exchanger flow resistance calculation referred to the same book ,the second chapter section2.4; the general idea of the program could be produced according to the contents of the second chapter section2.6. For the low-pressure heater consists of three sections: superheated steam section, condensing section, spray water section, so the calculations were done respectively. For condensing section, phase transition existed, so the calculation method of the convection heat transfer coefficient was different from other sections without phase transition.Form is the basic interactive platform between user and computer in Visual Basic. Through adding control items such as textboxes, comboboxes, labels, command buttons and so on, and operation of documents 'reading and writing, function declaration, and putting all the calculation formulas into command_click incidents in the order of their sequence in the design calculation, all the problems were solved in order.To make the simulation easy to achieve, a simplified model was used. To minish the sluggish stop dead zone that commonly exist in baffle plate heat exchanger, diversion holes in reasonable sizes and uniform distribution were applied in the first baffle plate counting from inlet to outlet. Numerically simulated the shell-side fluid flow of heat exchangers without holes and with holes in different sizes, and qualitatively analysed the results to guide the actual application.