An improved methodology for thermal calculation and design optimization of a thermosiphon waste heat boiler for CCPP

Abstract

The study is dedicated to enhancing design and computational methodologies for thermosiphon waste heat boilers (WHB) within combined cycle power plants (CCPP). The optimized WHB design and an improved thermal calculation approach are shown. The efficiency of the proposed WHB has been improved by optimizing the area and arrangement of the surface. The novel method incorporates considerations for the internal thermal resistance within thermosyphons and the graded velocity of natural circulation within the evaporation circuit. To refine the calculation method, empirical and experimental data concerning internal temperature gradient in thermosiphon functioning within a heat load spectrum of up to 17 kW/m2, were used. Important findings include three categories. Firstly, increasing the number of sections will slightly increase capital costs and decrease WHB gas temperature, which could be neglected by the unification of thermosiphon sections. Secondly, by applying this modified methodology to a power plant facility featuring a 6700 kW gas turbine engine (GTE), notable adjustments in thermal power were realized, amounting to 157 kW (approximately 6 %), along with corresponding electrical power adjustments of 149 kW (approximately 2 %). Third, the new method is limited to a GTE power of up to 10 MW due to the experimental data used for validation.