How do I convert velocity heads into bar for a static mixer?

Multiply: ΔP = N × K × ρv²/2, where N is the element count, K the velocity heads per element (1.5-3 for SK, 2-5 for SX), and ρv²/2 is one velocity head. In water at 1.5 m/s one head is about 1.1 kPa, so six SX elements cost roughly 0.13-0.34 bar.

Which static mixer type has the lowest pressure drop per element?

The SK helix: 1.5-3 velocity heads per element, the lowest in our range. The peer-reviewed literature agrees — helical elements run at roughly 5-6 times the friction factor of an empty pipe in laminar flow, while intensive cross-bar and grid geometries can sit an order of magnitude higher.

Does pressure drop double when I double the element count?

In the turbulent regime, yes — total ΔP scales linearly with element count. In deep laminar flow it grows faster than linear, which is why viscous duties need the pump head re-checked rather than extrapolated from a small test unit.

What happens to the pressure drop budget at peak flow?

It grows with the square of velocity. Our SX specification notes turbulent pressure drop at peak flow runs about 1.69 times the design-point value — a 30% velocity excursion is a 69% ΔP excursion, so the budget must be verified at maximum, not average, flow.

Static Mixer Pressure Drop per Element: SK vs SX vs SV

📅 October 30, 2026 ✍️ ywmixing Engineering Team ⏱️ 4 min read

Pressure drop per element is the quiet tiebreaker in every static mixer selection: two geometries that both hit your CoV target can differ by a factor of three in pumping cost. The comparison below uses the velocity-head ratings from our own specification pages, so the numbers match what a quotation will commit to.

The Ratings, Side by Side

Parameter	SK helix	SX cross-bar	SV corrugated plate
Pressure drop rating	1.5-3 velocity heads / element	2-5 velocity heads / element	0.1-0.5 bar across 8 elements at 2 m/s (water)
Viscosity ceiling	1,000,000 cP	10,000 cP	100 cP
Dispersion precision	≤ 10 μm	2-5 μm	1-2 μm
Elements to σX ≤ 5%	5-8 (180° twist)	4-6	4-8 (σX ≤ 1-5%)
Pipe range	DN15-DN500	DN25-DN800	DN15-DN1000
Clogging tolerance	Lowest risk (open helix)	Moderate (~70% open area)	High risk (2-5 mm channels)

Worked Example: DN50 Line at 1.5 m/s

One velocity head is ρv²/2. In water at 1.5 m/s that is about 1.1 kPa. Applying the ratings above to a six-element mixer:

Geometry	Heads total (6 elements)	ΔP at design flow	ΔP at peak flow (×1.69)
SK	9-18 heads	≈ 0.10-0.20 bar	≈ 0.17-0.34 bar
SX	12-30 heads	≈ 0.13-0.34 bar	≈ 0.22-0.57 bar

The 1.69 multiplier is not a safety guess: it is the square-law on a 30% velocity excursion (1.3² = 1.69), and our SX specification carries it explicitly. Budget the pump at peak flow, not average. The full derivation method — hydraulic-diameter approach, per-regime corrections — is in the pressure-drop calculation guide.

SX cross-bar static mixer elements whose open geometry sets the pressure drop per element

Why the Helix Is Cheap and the Cross-Bar Is Thorough

A 2025 peer-reviewed review of static mixers quantifies the trade: a helical element's friction factor is only about 5-6 times that of an empty pipe in laminar flow, while intensive cross-bar and grid geometries (the SMX class our SX belongs to) can run an order of magnitude higher — and need fewer elements, because each one cuts striations more aggressively (the review counts 10-15 helical elements to reach CoV < 0.05 in Newtonian laminar flow, versus about 5 for the most intensive geometries) (ACS Omega review, 2025). That is the whole deal in one sentence: the SK buys you the cheapest head per element and pays in element count; the SX pays more per element and finishes in fewer.

Pump-Head Decision Table

If your duty is…	Pick	Because
Marginal pump head, viscous blending to 10⁶ cP	SK type	Lowest heads per element, open helix passes fibers
Mid-viscosity (to 10,000 cP) needing 2-5 μm	SX type	Fewer elements to target; fine dispersion without 2 mm channels
Clean, ≤ 100 cP, tightest CoV in compact length	SV type	Best mixing efficiency per unit length; spec-sheet ΔP committed per 8-element unit

Between roughly 1,000 and 10,000 cP both SK and SX can run — see the sizing walkthrough for the element-count method before the pressure argument decides it.

FAQ

How do I convert velocity heads into bar?

ΔP = N × K × ρv²/2: element count × heads per element × one head. Water at 1.5 m/s makes one head ≈ 1.1 kPa, so 6 SX elements (2-5 heads each) land at 13-34 kPa ≈ 0.13-0.34 bar.

Which type has the lowest pressure drop per element?

The SK helix at 1.5-3 heads — consistent with published laminar data putting helical friction at only 5-6× an empty pipe versus an order of magnitude for intensive grid elements.

Does doubling the elements double the pressure drop?

In turbulent flow, yes — linear in element count. In deep laminar flow it grows faster than linear, so re-check the pump rather than extrapolating.

What does peak flow do to the budget?

ΔP scales with v²: a 30% velocity excursion costs 69% more pressure drop (the 1.69 factor our SX spec carries). Always verify at maximum flow.

Sources: ywmixing SV/SK/SX specification pages (velocity-head ratings, viscosity ceilings, dispersion figures, 1.69 peak-flow factor); "Static Mixers for High-Viscosity Systems: From Classical Helices to Machine-Learning-Optimized Geometries", ACS Omega (2025), DOI 10.1021/acsomega.5c08387 — helical friction factor ≈ 5-6× empty pipe, intensive geometries an order of magnitude higher, CoV < 0.05 at 10-15 helical elements. Head value ρv²/2 derived for water at 1.5 m/s.