Effect of non-condensable gas on heat transfer within the hollow fin condenser of metallic and polymer vapor chambers

Abstract

• Effect of non-condensable gas (NCG) in condensers with hollow fins is investigated. • Thermal behavior and performance of polymer and aluminum condensers are compared. • Predictions of the numerical diffusion model agree well with experimental data. • Performance of air-cooled polymer and aluminum condensers is comparable. • Aluminum condensers are more sensitive to NCG than polymer ones. A vapor chamber with hollow fins was manufactured and tested with condensers made of polymer and aluminum. The fins are 5.3 mm in inner diameter and cooled by forced air convection. The use of polymer instead of aluminum has little influence on the performance: it is of interest for weight reduction when the cooling medium is air. The impact of non-condensable gas (NCG) is studied experimentally using IR temperature measurements on the fins and performance monitoring over time. To complete the study, a numerical model of film condensation inside a vertical tube in the presence of NCG is developed. The model combines hydrodynamic and axial mass diffusion phenomena with 2D heat conduction in the wall. A good agreement is found between experimental results and model predictions. The effect of the NCG mass, heat load, external cooling coefficient and wall thermal conductivity is studied though a parametric analysis. When the wall thermal conductivity increases, so does the volume occupied by NCG inside the fins and the performance degradation. In other words, aluminum condensers are more sensitive to NCG than polymer ones, and the difference is all the more important as external cooling is efficient.