Performance prediction of finned air-cooled condenser using a conjugate heat-transfer model

Abstract

Finned air-cooling condensers save a significant amount of water in Rankine cycle power plants; however, their heat-removal capability is difficult to predict due to the condensation in finned tubes resulting from the coupled heat transfer between vapor and cooling air fluid. This study develops a conjugate-model-based approach to characterize the thermal-hydraulic development by the transverse flow of vapor and cooling air in a finned tube, and to quantify effects of varying vapor and cooling air operation on the in-tube condensation and out-tube air convection. The approach proposes all uncoupled conditions of a conjugate model on the heat-exchange interfaces, which guarantees that the temperature and heat flux are equal everywhere on the finned tube. Applied to an engineering finned tube, the model verifies that a high vapor mass flux likely reduces the condensation level, and the effect of non-condensable gases with the inlet mass fraction of 0–5% is negligible to the vapor condensation; an increase of cooling air velocity enhances the performance of both vapor condensation and cooling air convection effectively, and a decrease of atmosphere pressure reduces them obviously. The approach is beneficial in designing an enhanced finned tube and operating a field condenser efficiently.