Mathematical Modelling and Simulation of Heat Transfer Analysis of Thermal Power Plant Components

Abstract

Boiler consists of several types of interconnected heat exchangers like superheater, reheater, economizer and boiler drum in which fluid flow and heat transfer processes takes place. It is very important to carry out heat transfer analysis and estimate the wall temperatures of various components for the safer and efficient operation of these components. In the present study, the dynamic behaviour of flue gases to water/steam heat exchangers of a typical 500 MW Thermal power plant components are studied using the mathematical modelling and computer simulation. Various boiler components like superheater, reheater, economizer and boiler drum are modelled under connected conditions. The convective heat transfer coefficient, non-luminous heat transfer coefficient and heat transfer calculations are done using correlations available in the open literature. In the sections where radiation is applicable, appropriate amount of radiation is considered. The equations represented in the entire processes of boiler are in the form of ordinary differential equations. Based on the mass balance, heat balance and heat transfer models, differential and algebraic equations are formulated. The steady state and dynamic equations thus formed are solved using Excel along with Visual Basic Application (VBA). Advanced Continuous Simulation Language (ACSL-X) solver is used for solving the differential and algebraic equations. All the fluid/steam properties and transport properties for flue gases (with moisture) are considered under variable temperature conditions. From the simulation, convective heat transfer coefficient, non-luminous heat transfer coefficient, heat transfer rate for steam/water and gas side, wall/metal temperature at inlet and outlet have been determined. The effects of variation of gas flow and steam temperature were studied on the performance of superheater, reheater and economizer. The deviation between simulation results and tested data was found within 0% to 1 % in the case of heat transfer coefficients, 2% to 7% in heat transfer rate and 0% to 0.7% deviation in steam temperature at outlet of superheater and reheater; which shows very good agreement. In addition to boiler components, modelling and simulation of turbine casing was also done where similar methodology was applied as heating sections of boiler. The obtained results of turbine casing were also found in good agreement with expected trends.