Air principle · laminar displacement

Air as a piston.

Sometimes it is not about comfort but about a clean workstation. Then filtered air has to flow across the workstation in one direction: calm enough not to mix, and steady enough to push contaminants ahead of it to the extract. That is laminar displacement, and the Krantz VA-L is made for it.

The VA-L

A box above the workstation, a layer of air beneath it.

The VA-L hangs above the workstation and is fed with filtered air through a duct from the air handling unit. Guide vanes in the housing spread the air evenly over the discharge face, a finely perforated plate. Below it, the air sinks vertically with low turbulence and pushes contaminants from the working zone to the extract openings. (DS 4056 E p. 2)

The VA-L in the collection →

, technical data VA-L

(DS 4056 E p. 2):

Air volume 300–3,000 m³/h
Discharge velocity 0.15–0.4 m/s, related to L × W
Temperature difference supply – room −1 to −3 K
Pressure drop 10–40 Pa
Length 1,000–2,000 mm, width 500–1,000 mm, housing height 305 mm
Housing, guide vanes and discharge element in galvanised steel
Rectangular connection spigot at the end, optionally circular from above; spigot velocity below 4 m/s
Suspended at two fixing points, with threaded rods or quick-release clamps

What the air does

One direction, no mixing.

Top down

The displacement flow goes straight down onto the workstation. It is stable from 0.15 m/s. (VA-L, DS 4056 E p. 2)

Undisturbed by the people below

According to the datasheet, staff activity in the occupied zone below the VA-L does not disrupt the flow. (DS 4056 E p. 2)

Little air, low velocity

Air velocity and temperature difference in the occupied zone stay low. Krantz gives a low air volume and low energy costs as the result. (DS 4056 E p. 2)

Horizontally, across the full width

The same principle also works lying down: in an indoor firing range, an air distribution wall behind the shooter pushes the air like a piston along the range to the bullet trap. (VA-RSA, DS 4168 E p. 2)

When to choose laminar displacement

Where air has to carry something away.

Workstations where airborne contaminants must go: the VA-L keeps the working zone clean with filtered supply air (DS 4056 E p. 2).
Indoor firing ranges: powder fumes must not drift back to the shooter (VA-RSA, DS 4168 E p. 2).

Design limits

The limits per type.

Type	Application	Velocity	Max. ΔT	Air volume	Source
VA-L	above the workstation, suspended	0.15–0.4 m/s, stable from 0.15 m/s	−1 to −3 K	290–2,880 m³/h; pressure drop 10–40 Pa	DS 4056 E p. 2
VA-RSA	indoor firing range, wall behind the shooter	min. 0.25, max. 0.35 m/s along the range	stable piston flow up to approx. ±4 K	project volumes approx. 8,000–40,000 m³/h	DS 4168 E p. 2, p. 4–5

VA-L connection: choose the spigot height or diameter so that the velocity in the spigot stays below 4 m/s (DS 4056 E p. 2).

Typical mistakes

Where it goes wrong.

Too slow. The VA-L is specified from 0.15 m/s; below that, the datasheet gives no stable flow (DS 4056 E p. 2).
Too cold. The VA-L works at −1 to −3 K. A larger temperature difference is outside the datasheet.
Heating. The datasheet only covers supply air that is cooler than the room. It gives no heating mode.
No extract on the far side. A piston flow has a start and an end. Without extract where the air needs to go, it has no direction.
Heat sources in the flow. Rising warm air works against a downward low-turbulence flow.

Filters and containment

What happens behind the outlet matters just as much: the filter, the filter housing and the dampers. For BSL-3 and BSL-4 laboratories, pharmaceutical production and nuclear technology, Peek supplies the filter and shut-off systems of Krantz Filter- und Absperrsysteme in the Netherlands.

High containment →

The types in the collection

Laminar and piston flow: VA-L · VA-RSA

Displacement from the ceiling: Q-DN · Q-DV · VA-T · VA-TH

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