Constructal optimization for a marine boiler based on entransy theory

Abstract

<p indent="0mm">Based on entransy theory and constructal theory, performance optimization of a marine boiler is conducted by taking the outer diameters of the third convection evaporation tube, superheater tube, and economizer tube as the design variables with the total heat transfer area constraint of three main heat exchange components (evaporator, superheater, and economizer). The optimal construct and performance of the whole boiler are obtained. First, the optimization is performed by taking a complex function comprising the linear weighted sum of entransy dissipation rate and power consumption rate as the optimization objective. The influences of initial design parameters, such as heat preservation coefficient, weighting coefficient for the composite function, and heat transfer rate, on the constructal optimization results of the whole boiler, are analyzed. Results show that the optimal dimensionless tube outer diameters of the evaporator, superheater, and economizer are 1.2, 1.3, and 1.1, respectively, which make the composite function obtain the cubic minimum value of 0.737. Compared with the initial design point, the composite function of the overall boiler is reduced by 26.3%, and the comprehensive performance of the boiler is significantly improved. Second, the bi-objective optimization of the overall boiler based on the composite function is conducted based on the NSGA-II algorithm, and the corresponding Pareto frontier and optimal construct of the boiler are obtained, which can provide a wider selection space for the performance optimization and parameter design of the overall boiler. The results of this paper can provide a certain degree of theoretical guidelines for the overall performance optimization design of marine boilers.