The optimum location of vapor compressor in multistage vacuum membrane distillation system

This paper investigates the performance optimization of a multistage vacuum membrane distillation (MSVMD) system integrated with a mechanical vapor compressor (MVC) for efficient water desalination. The conventional integrated MSVMD and MVC systems lack a detailed analysis regarding the optimal placement of the MVC, which can influence both productivity and energy efficiency. To address this gap, this study evaluates different compressor placements within the MSVMD setup, assessing their impact on productivity and the gained output ratio (GOR) under various operational parameters, including feed temperature, flow rate, number of stages, and vacuum pressure. The results reveal that the optimal MVC placement can increase system productivity by up to 28 % and enhance energy efficiency, achieving a GOR of about 13. Middle MVC placements maximize productivity, yielding freshwater production up to 500 L/h, while different placements, depending on the feed temperature, optimize the GOR. The parametric study demonstrates that increasing feed temperature significantly boosts productivity, particularly at lower numbers of stages, but reduces GOR due to the higher thermal losses. Additionally, higher feed flow rates improve productivity, with GOR stabilizing at the highest flow rates, and lower pressures in the permeate side increase productivity while keeping GOR consistent. The optimized MSVMD system thus offers a balanced approach, achieving substantial freshwater production with high energy efficiency.