As a continuation of the basic tests to determine the flux through the levitator valve at various gaps and pressures, I place a plate at various distances from the orifice as a valve and measure the flux versus pressure. Except at low pressures below 5 psig, the flux turns out to be monotonic, and not strictly proportional to the orifice area.

The Valve

Schematic of the device to measure flow through a plate valve. Air from the plenum at the left at [P, T] flows through the round orifice with diameter [D] and then through a gap between the plates of width [h]. The question mark [?] represents the unknown flux.

The Test Device

The actual device to measure flux between close plates. Sheets of aluminum foil maintain a space between acrylic plates and keep the sheets of aluminum squeezed flat.

Test Device Detail

The device with the top plate removed shows the 1/8" orifice from the plenum below and also some aluminum foil spacers.

The makers of Standard Reynolds Wrap claim their product has a thickness of between 6.3 and 7.7 microns. My measurements with a micrometer indicated a thickness of about 7.2 microns.

As in the experiments with open orifices, flux is related to the orifice area. I used strips of aluminum foil to build spacers. Flux 16 means the flux with a spacer with the width of 16 sheets of foil. Flux Max is the flux with no top plate.

Flow measurements below 0.5 scfm were at the end of the meter range and were difficult to read.

For pressures above about 5 psig, the flux ratios are relatively constant and increase with the orifice area. For example, at 10 psig, the flux through a 32-ply gap is about 1.75 times the flux through a 16-ply gap. As in that case, the ratios are generally close to and yet not in exact proportion to the ply (see table below).

Gap (ply)

10e-6 inches

mm

Area (m²)

Gap Ratio

Flux Ratio

4

29

.073

0.25

0.25

8

58

.146

0.50

0.59

16

115

.292

1.00

1.00

32

230

.584

2.00

1.75

Max

2.84

2.25

The flux ratios are not strictly in proportion to gap ratios. This discrepancy is noted not investigated further at this time since the goal of this exercise is to demonstrate that for the purposes of a simulation model, the flux through the valve is basically a function of pressure and gap size. Determination of the second order effects is a bit off the main path of this report on Radial Momentum.

The levitator under study typically operates in the pressure range from 5 psig to 20 psig and in the flux range from 2.2 scfm to 2.6 scfm. That places the gap at about 16 to 32 ply or about 24 ply or .438 mm and the flux ratio at about 1.375. Based on the flux through an open 1/8" orifice, a rule of thumb equation for valve flux is:

F = Fmax /2.25 * [1 + (h -.292)(1.75-1.00)/ (.584-.292)]

For Max Flux of 2.25: F = 1 + (h-.292) * 2.568,

so F(16) = 1, F(24) = 1.5 and F(32) = 1.75