Performance of an internally fan circulated air gap membrane distillation (AGMD) unit

Abstract

This work involves an experimental investigation of a novel air gap membrane distillation (AGMD) unit with an installed circulating fan within the condensation chamber. The installed fan breaks the resistance to mass and heat transfer in the gap chamber by inducing fluid mixing and a turbulent dissipation rate, which enhances the overall mass and heat transfer characteristics of the system and consequently the overall performance of the system. The system performance, such as vapor flux, specific thermal energy consumption (STEC), and desalinated water cost, of the new AGMD is evaluated and compared to the traditional AGMD system. The influence of fan design variables, including fan revolution, fan thickness, and fan diameter, on system performance is investigated. Furthermore, the effect of feed water temperature on the system’s performance is assessed and pre-sented. Results indicate that fan speed significantly improves the performance of the new AGMD system compared to conventional AGMD designs. Fan thickness recorded a marginal effect, and fan diameter registered some influence, while fan revolution exhibits the strongest impact on the sys-tem’s performance. The new system can attain a maximum flux and minimum STEC of 34.16 kg/ m2·h and 710.72 kWh/m3, respectively, as against the conventional units, which registered a peak vapor flux and lowest STEC of 17.69 kg/m2·h and 1,141.25 kWh/m3, respectively.