Simulation of innovative hybridizing M-cycle cooler and absorption-refrigeration for pre-cooling of gas turbine intake air: Including a case study for Siemens SGT-750 gas turbine

Abstract

Higher compressor intake-air temperature not only significantly reduces the performance of the gas turbine (GT), but also increases the NOx emissions. Absorption (AB) refrigeration, which is powered by heat, is a promising option for cooling GT intake air. M-cycle technology is a unique water-based indirect evaporative cooler (IEC) providing sub wet-bulb temperature. In novel hybrid pre-cooler, the air is cooled down to near dew-point temperature by the M-cycle first and then further cooled by the AB. Both AB and M-cycle coolers consume very little electricity and the main required sources (heat for AB refrigeration and water for the M-cycle IEC) are provided by waste heat from GT and condensed water from AB meaning almost zero-energy pre-cooler for GT intake air. The dependency of the intake mass flow and GT power output on the intake air temperature is first identified and correlated using experimental data provided by Siemens company, and then the required physical/mathematical modelling is presented and developed using Engineering Equation Solver. Finally, the GT performance is comprehensively discussed for a wide range of climate conditions when the AB and M-cycle work solely or jointly as a GT intake air pre-cooler. The hybrid pre-cooler was found to be a cost-effective way to boost the GT power output by 29%, however, this enhancement for GT using AB refrigeration and M-cycle IEC was around 17% and 15% in average respectively.