Novel design of liquid distributors for VMD performance improvement based on cross-flow membrane module

To enhance the vacuum membrane distillation (VMD) permeate flux of cross-flow membrane module (CF-MM), three kinds of novel liquid distributors were designed and evaluated by computational fluid dynamics (CFD) simulation. Based on the characteristics of the CF-MM, a three-dimensional liquid flow model was built in the shell side of the CF-MM. The feed flow conditions were simulated and calculated. Based on the simulation results, the structural parameters of the liquid distributors were optimized to achieve an even liquid distribution. The pyramidal and dome-like distributors have better liquid distribution than the flat-plate distributor. Two kinds of liquid distributors in flat-plate and pyramidal forms were fabricated and used to study their performances in VMD. Compared with the permeate flux of CF-MM without a distributor, the permeate flux increased to about 5% of the flat-plate distributors, and to about 6% to 12% of the pyramidal distributors. The optimized distributors significantly enhanced the VMD permeate flux of the CF-MM. With the novel pyramidal distributor, a maximum permeate flux of about 72 kg/m2h was achieved at feed inlet temperature of 358.15 K, vacuum level of 87 kPa, and feed interstitial velocity of 0.085 m/s.