In-tube thermodynamic analysis on incomplete/complete condensation in finned tube condensers using a conjugate heat transfer model

摘要

Considering both the incomplete and complete condensation, a conjugate-model-based approach is developed to characterize the distributed thermodynamic development inside finned tube condensers. Applied to an engineering oval finned tube, the approach verifies the in-tube flow pattern as annular and river in incomplete and complete condensation respectively; furthermore, quantifies and compares the varying characteristics of cooling wall temperature, condensation heat flux, condensation HTC, film thickness, wall shear in the two condensation.In incomplete condensation, the condensation HTC increases slowly with the condensation approaching, unaffected by the steam quality, or film Reynolds number. With regarding complete condensation, an immediate decline of cooling wall temperature, and condensation heat flux and HTC is observed at the end of condensation, one easy-freezing location is marked for the safety operation of condensers, and the backflow of air is found at the vapor outlet. Concerning the phase change section, due to a much lower cooling wall temperature, the complete condensation provides a much greater condensation heat flux, but a nearly equivalent condensation HTC, as comparing to the incomplete mode.The approach is beneficial in designing an enhanced finned tube and operating a field condenser efficiently. (C) 2019 Elsevier Ltd. All rights reserved.