Modelling the Transient Behaviour of Heat Recovery Steam Generators

Abstract

This paper describes a method used to compute the transient performances of assisted circulation heat recovery steam generators. These heat recovery steam generators are composed of several heat exchangers, each of which is a bundle of tubes. The method presented here treats each heat exchanger in a similar way, replacing the bundle of tubes with an ‘equivalent’ linear heat exchanger. This equivalent linear heat exchanger is then discretized in as many slices as required by the accuracy. The mass and enthalpy equations on each of these control volumes are solved by a fully explicit numerical method, adapted for the special conditions encountered in this kind of problem, allowing a considerable reduction of the computation time compared to other methods. Some emphasis is put on the modifications required to solve the equations for the evaporators because they are two-phase heat exchangers. A model for the steam drums is also presented together with simple models for the main control loops used in such systems. An example is presented in which an existing dual pressure level heat recovery steam generator is started from a cold state. The numerical predictions are in good agreement with measurements.

Compact Steam Bottoming Cycles: Minimum Weight Design Optimization and Transient Response of Once-Through Steam Generators

“…Its accurate estimation is challenging due to the variety and complexity of tube and fin geometries and finned tube geometry and arrangements. ESCOA-based correlations (Weierman, 1979) are normally considered the most comprehensive method as it includes tube pitches and number of tube elements in the bundle (Dechamps, 1995). The estimation of the heat transfer correlations requires calculation of several coefficients including Colburn number Co, Reynolds Re, and Prandtl Pr.…”

Mathematical Modelling of Dynamics of Boiler Surfaces Heated Convectively

“…The basic assumptions of the proposed model refer to the parameters of the working fluids. It was assumed that there are no changes in combustion gases flow and temperature in the arbitrary cross-section of the given superheater or economizer stage (Dechamps, 1995). The same applies to steam and feed water.…”

Estimation of condensate mass flow rate during purging time in heat recovery steam generator of combined cycle power plant

“…Many researchers have been conducted about modeling of HRSG [6][7][8][9][10][11]. Dechamps [6] described a method used to compute the transient performances of assisted circulation heat recovery steam generators. In his mathematical modeling bundle of tubes in each part of HRSG replaced with equivalent linear heat exchanger.…”