Quantitative validation of an in-flow water condensation model for 3D-CFD simulations of three-way junctions using indirect condensation measurements

Abstract

The usage of three way junctions to merge fluid streams is widely extended. For certain applications, such as refrigeration systems or internal combustion engines, the mixing of humid gaseous flow leads to bulk condensation, which compromises the integrity of the downstream elements. In this work, a test bench is adapted to manage the mixing of wet streams and a novel experimental technique is developed to measure condensation indirectly. Well-resolved temperature distributions are measured by means of a rotating array of thermocouples at experiments with and without humidity. Enthalpy balances using temperature distributions of both cases allow to infer the condensation mass fraction field. 3D CFD simulations with an in-flow condensation sub-model are compared with these measurements for two junction geometries and two operating conditions, with an average agreement of 11% in terms of condensation mass flow rate. The three-way junction design and its ability to reduce mixing is found to be of paramount importance to reduce bulk condensation. This validated model is therefore suitable for optimizing the junction geometry in terms of condensation reduction. With limited water condensation, NOx, CO2 and particulate matter emissions can be strongly abated for internal combustion engines by extending the usage of low-pressure exhaust gas recirculation to cold conditions.