On recent advances in modeling of two-phase flow and heat transfer

General thermal design methods for two-phase heat exchangers are emerging that are based on local two-phase flow patterns and the flow structure of the two-phases. These methods promise to be much more accurate and reliable for predicting two-phase heat transfer coefficients and pressure drops than the older, statistically-derived empirical design methods that completely ignore flow regime effects or simply treat flows as stratified (gravity-controlled) or nonstratified (shear-controlled) flows, which greatly limits their accuracy, validity, and reliability and often results in prediction errors surpassing 100% within their supposed range of application. These new flow pattern and flow structure types of design methods are particularly suited for use in modern heat exchanger design software, which are typically incremental and hence require local methods that capture the real trends in experimental data. The status of these new developments is reviewed here for intube two-phase flow and heat transfer processes.