Condensation in plain horizontal tubes: recent advances in modelling of heat transfer to pure fluids and mixtures

Abstract

Recent work on improving general thermal design methods for condensation inside plain, horizontal tubes is presented, summarizing primarily the advances proposed at the Laboratory of Heat and Mass Transfer at the EPFL in collaboration with the University of Padova and the University of Pretoria. This work has focused on the development of a unified flow pattern, two-phase flow structure model for describing local heat transfer coefficients for pure fluids, azeotropic mixtures and zeotropic mixtures. Such methods promise to be much more accurate and reliable than the old-style statistically-derived empirical design methods that completely ignore flow regime effects or simply treated flows as stratified (gravity-controlled) or non-stratified (shear-controlled) flows. To achieve these goals, first a new two-phase flow pattern map for condensing conditions was proposed, which has been partially verified by flow pattern observations. Secondly, a new condensation heat transfer model for pure fluids and azeotropic mixtures has been developed including not only flow pattern effects but also interfacial roughness effects. Finally, the widely used Silver-Bell-Ghaly condensation model for miscible vapor mixtures has been improved by including the effects of interfacial flow structure and roughness on vapor phase heat transfer and a new non-equilibrium effect added

Statistical characterization of two-phase slug flow in a horizontal pipe

“…Since no experimental data of void fraction was obtained, the numerical results are compared with Rouhani-Axelsson void fraction correlation for horizontal flow (Thome, 2005). Table 2 shows that a reasonable agreement was obtained between the predicted average void fraction values and correlation results, especially for Cases 1 and 2.…”

Experimental Investigation of Condensation Heat Transfer Characteristics of R-134a Vapor in Horizontal Heat Exchanger

“…The theoretical results are determined using three of the most quoted predictive models, Shah, Cavallini and Thome [14]- [16]. These theoretical results are calculated by engineering equations solver (EES) software based on similar operating conditions and plotted with experimental results for comparison.…”

Condensation of refrigerant R407C in multiport minichannel section

“…Review of the modern calculation methods for heat transfer coefficient and pressure drop in the condensation in conventional and minichannels was reviewed and discussed in [9]. Authors show the usefulness of Silver-Bell-Ghaly [17,3], Thome [18], and Cavallini et al [8] calculation methods. These methods are developed based on a mechanism of zeotropic mixtures flow condensation.…”