Enhancement of Thermal Efficiency of Exhaust Gas Economizer for Ultra Small Combined Cycle

Abstract

The economizer is the most important component in the ultra small combined cycle (USCC) using gas and steam turbines to utilize the high energy in the exhaust gas from the gas turbine. The flow pattern of the exhaust gas through the finned tubes of evaporation and superheating strongly affected the thermal efficiency of the present compact economizer. When the inlet exhaust pipe was simply connected to the economizer, sufficient steam to operate the steam turbine could not be obtained. To investigate the low heat recovery rate and the flow pattern in the economizer, 1/5 scale model experiment by using a water was conducted. The observation showed non-uniform flow cased by the eddy in the inlet plenum. A flow nozzle was installed at the inlet plenum of the actual USCG economizer to suppress the non-uniform flow. After the installation of the flow nozzle, the heat recovery rate in the economizer was increased from 41.4% to 51.1%.