Direct numerical simulation of flow in spacer-filled channels: Effect of spacer geometrical characteristics

Membrane distillation heat transfer enhancement by CFD analysis of internal module geometry

“…However, while in the literature many works considered the elementary cell as a single set of crossing filaments [10,12], in this case the cell consisted of a small portion of a spacer filled channel, containing a number (between 5 and 6) of longitudinal and transversal filaments, thus allowing the simulation of the thermo fluid dynamics also among the rows of filaments.…”

“…Also in 2007, Koutsou et al [12] presented a novel modelling approach, adopting more powerful computing hardware and modern commercial CFD codes, with the possibility of modelling the fluid dynamics of complex geometries using Direct Numerical Simulations (DNS) with high-resolution computational grids. In this case the study is limited to fluid dynamics aspects, analysing in particular the dependences of pressure losses with the two main geometrical parameters characterising diamond spacers, i.e.…”

Comparative study of red grape must nanofiltration: Laboratory and pilot plant scales

“…The feed flow spacers, which usually consist in non-woven nearly cylindrical filaments, serve to separate adjacent leaves of the membrane and to create flow passages, but also to promote flow unsteadiness and therefore, to enhance mass transport. In this way, the undesirable fouling, concentration polarization and 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 5 osmotic pressure on the membrane surface are mitigated (Koutsou et al, 2007). The trade-off for a higher mass transfer rate is an increased pressure loss along the feed channel (Schwinge et al, 2004).…”

“…Therefore, the Reynolds number, defined on the basis of the average velocity and the spacer filament diameter, is less than 200 (Koutsou et al, 2007).…”

“…In fact, it has been concluded (Karniadakis et al, 1988) that this cylinders act as eddy promoters and their presence leads to the destabilization of the flow by essentially the same mechanism as in rectangular channels but at much lower Reynolds numbers (on the order of hundreds rather than thousands). In more recent studies, (Koutsou et al, 2007) the flow inside rectangular channels with non-woven diamond-shaped spacers were studied using direct numerical simulation. The results revealed that, for the range of geometrical parameters examined, the transition Reynolds number occurs at relatively low values: Re= 35 -…”