A robust and simple correlation for internal flow condensation

Abstract

Accurate prediction of the heat transfer coefficient for internal flow condensation is essential for designing and optimizing condensers. Due to advances in manufacturing techniques and new environmental and safety regulations in recent years, applications arose with extensive use of microchannel condensers and low GWP refrigerants. Consequently, a new range of condensation flow conditions is emerging, which requires the evaluation of the accuracy of available correlations and the proposition of more accurate ones. In this work, the most extensive and updated experimental database for heat transfer coefficient (HTC) on internal flow condensation was gathered from the literature, which includes 69 working fluids, 12,017 data points, channel diameters ranging from 0.067 to 20.8 mm, and horizontal and vertical flow directions for smooth tubes. Correlations proposed from 1958 to 2023 were evaluated and compared to this database to verify their prediction error. A new simple HTC correlation was developed, showing that further improvement of available correlations is still possible. The new correlation predicted the database with a mean absolute error of 23.3 %, a 5.3 % relative improvement compared to the second-best-ranked and more complex correlation. This analysis showed that a few well-known dimensionless groups can accurately model the heat transfer process during condensation in a broad range of operational conditions.