Towards the evaluation of heat and mass transfer in pipe flows with cocurrent falling films using One‐Dimensional Turbulence

Abstract

AbstractTurbulent mixed convection in an air‐water system is evaluated with a novel numerical solver implementing the stochastic One‐Dimensional Turbulence (ODT) model in a turbulent air flow surrounded by a laminar cocurrent water falling film in a cylindrical geometry. The ODT model is used as a reduced order surrogate model for the effects of turbulent advection, turbulent heat flux, and turbulent mass‐flux within a one‐dimensional domain. An ad‐hoc temporal‐to‐spatial transformation relying on the bulk flow gas velocity is used to obtain streamwise‐dependent statistics of the flow. The ODT simulation results are compared to simulations obtained with the assumption of a quasi‐laminar one‐dimensional gas flow, and to Reynolds‐Averaged Navier‐Stokes (RANS) reference data for a cocurrent water falling film evaporator [1]. The results show that the turbulent transport plays a decisive role in the estimation of interface gradients of temperature and vapor mass fraction. Although ODT predicts global quantities such as the interface temperature in a reasonable way, the model falls short of successfully predicting streamwise‐dependent radial profiles. Despite the shortcomings, the framework presented here is the first stepping stone towards the evaluation of complex multiphase momentum, mass, and heat transfer couplings with full scale resolution on potential evaporative devices. The model, thus, provides valuable information with minimal empiricism on the dynamics of the small scales for pioneering engineering applications.