Home >> Industry Knowledge >> Nitrogen Generator (Nitrogen equipment) Flowmeter
Preface
This article provides a fluid flow through parallel plate distributor of a number of small holes
Design methods. The design is based on fluid flow through the theory of piercing
With the experimental data and the assumption of two trusted to carry out the. In sharp
Kong should be based on the adsorption layer, the distribution in the cross section to locate and the total flow
Is divided into equal sub-flows and the flow through the orifice of each hole 2
Kinds of cases, the thickness of a thin orifice plate flow distribution can enable the capacity of
Evenly enough to work device cross-sectional area.
In with desiccant, adsorbent and other equipment, operation, fluid
The correct distribution is an important factor. Porous plate is often used to ensure that
Fluid flows through the bed in the device cross section of the flow uniformity. Orifice
Distributor shown in Figure 1.
A principle of piercing the application of flow
Fluid flow through a sharp contraction in holes being accelerated due to its kinetic energy
(Velocity μ) increases, the pressure can be (p v) reduced. Fluid flow
Figure 1 absorber plate distributor
Section to section down to an orifice on the A1 at the A0, later
Degree reduced to shrink veins Office A2 (shown in Figure 2). Shrink veins at the surface
Product and the relationship between orifice area contraction coefficient of CC can be expressed as, CC
= A2 / A0. If the pressure is within a short distance in the upstream flow disturbance is not
Dynamic Office (section A1) and the narrowest point in the mobile section (section A2),
Then the application of energy and material equation was:
Figure 2 holes shrink with the flow line of
(μ2
2 / 2φ2) - (μ1
2 / 2φ1) + g (z2 - z1) +
∫ 2
1 vd p + w1 + F = 0
This type shall be Bernoulli's equation. Fluid flow of water in the same baseline
Plane (z = 0), ascended the throne can be equal to zero. If the fluid flow did not produce
Health and friction, they do not do work on the surrounding environment, and even if w1, and F for the
Zero, with the flow coefficient C into account the friction loss on the plate, as well as CC,
φ1 and φ2 (speed factor) equivalent, and the vessel cross-sectional area A1
m
A0, obtained after finishing incompressible fluid through the hole board, sharp
Hole Flow Q [1, 2, 3]:
Q = CA0
2gΔp
ρ (1)
Where: A0 --- holes flow through the cross section area, m2;
C --- flow coefficient;
Δp --- fluid the pressure drop through the hole, kgf / m2;
ρ --- Fluid Density, kg / m3;
g --- gravitational acceleration, mPs2.
This has been a simple and practical calculation of flow formula,
However, coefficient C is not a simple function, it is with the orifice
On the Reynolds number is related as shown in Figure 3 [1]. In the Reynolds number Re>
104, preferable 016 ~ 0161 as a small hole C-value.
Figure 3 orifice flow coefficient
Compressible fluid flow must be introduced for the expansion of correction factors,
Required under Δp / p to find out the correction factor (with plans to be investigated).
Two equal distribution of
Envisages that the flow through the distribution of the flow of holes in each board are equal, must be
To be forced to rearrange the fluid itself, so that each hole of the flow near the
Equal. If too much fluid resistance through pores become greater than the fluid
Rearrangement of resistance, they are required to re-arrangement of fluid may occur, thus
To obtain equal distribution of results. If the resistance through the distributor can be neglected
Excluding a little, then the fluid can not be unaffected forced rearrangement, it is by every little
Would be difficult to allocate the flow holes, because of least resistance through the distribution plate of
Channels are not just equal distribution of means.
Tests showed that the distribution area of a circle arranged according to concentric circles [4],
Concentric distance equivalent to pitch in each circle on the pitch are also similar
And so on, or slightly larger than the radial pitch. With concentric circles of equal spacing
10 laps, for example the area of distribution as the arrangement of holes criteria, shown in Figure 4
Shown.
(1) concentric circles of equal spacing
10-lap area distribution
(2) The total area of circle
The relationship between the radius of
Figure 4 Area of distribution
3 2 assumes that
(1) assuming current weight, eliminate resistance does not exceed the total flow from the entrance guide
Tube into the container by the sudden expansion (Figure 5) resulting
The friction loss. On this assumption, rearrangement of the resistance is defined as
Is equal to the total flow into the container when the loss of local resistance. Gas into
The container should not take over the gas nozzle into the container directly from the adsorption
Agent layer, should be made with air holes drilled through the wall or open a gate seam spray
Trachea (some things around the screen made for the cartridge), also can be used bubble
Cover to protect. Import of these gases, the resistance should be equal to the total rearrangement
Traffic flow through the perforation of full-length jet ring friction loss. Local resistance loss
Loss caused by pressure changes, from the familiar formula:
Δp = Σζ
ρw1
2
2g
(2)
Where: w1 --- to take over an average speed over-current cross-section, mPs;
Σζ --- and the local resistance coefficient;
Σζ = (1 --
A1
A2
) 2
A1, A2 --- import over and over-current section of the container surface
The plot, m2.
(2) assuming ratio: defined as the flow distribution device flows through the hole resistance
Resistance force for the rearrangement of 100 times, that is, Δp0 = 100Δp, is sufficient
To ensure equal fluid flow through each hole. This ratio was set for the design of
The minimum ratio, and for most cases, because the resistance of a rearrangement
As much. The smaller the ratio will reduce the possibility of access to the same traffic
Sex. But when the pressure drop does not allow such a high, it can be used
To achieve the highest value.
4 Example
A set of small-scale air separation plant, gas source is a Taiwan ZW20167 / 8 type
To provide oil-free air compressors, conversion to the standard state of air
Flow 3712m3 / h, air temperature 30 ℃, air pressure
0170MPa (A). To design a molecular sieve adsorber of the plate the distribution of
Device, adsorber diameter D = 235mm, imported over size
Φ25mm × 118mm.
(1) to determine the pressure drop rearrangement resistance calculation.
Found p = 017MPa, t = 30 ℃ when the physical properties of air data,
ρ = 719kg / m3, μ = 1817 × 10 - 6N · s / m2.
State calculations flow Q = 116912 × 10 - 3m3 / s,
Velocity w = 417mPs.
According to type (2), Δp =
719 × 4172
2 × 9181
(1 --
010,214
01235
) 2 =
7136kgf / m2.
(2) The calculation of the pressure through the distributor hole down.
Δp0 = 100Δp = 736 kgf / m2, take 750kgf / m2.
(3) Calculate the Reynolds number Re and determine the C value.
Re =
ρwD
μg
=
719 × 116912 × 10 - 3 × 01235
01785 × (01235) 2 × 1187 × 10 - 6 × 9181
= 3946
From Figure 3 Richard C = 0160.
(4) Find the correction factor ε.
Δp / p =
750
017 × 105 = 010107, Chattooga get ε ≈ 1, ie
For incompressible fluids.
(5) According to the pressure drop, according to equation (1) to determine the distribution of the different devices
Diameter hole flow (see Table 1).
(6) According to be called hole flow, determine the diameter of the small
Number of holes (see table 1). After calculation and order, the final selection of N =
57 holes, diameter of 112mm.
Holes with different diameters in Table 1 Traffic
Hole diameter
/ Mm
Flow through the holes
/ (M3 / h)
Number of holes
/ A
Total Flow
/ (M3 / h)
0,180,128,991,203,418
112 016,525,573,712
116 112,506,303,418
(7) according to the arrangement of Figure 4 to set the best criteria for the distribution of the form.
5 Conclusion
Using two assumptions, the application principle of piercing the design side traffic
France, which would ensure flow distribution device through the orifice hole flow equivalent sub -
Cloth, fluid can be evenly into the absorbent layer, so that adsorption and mass transfer area suction
With uniform movement, ensure the efficient use of adsorbent.
This design method is suitable for heat exchangers, towers of fluid flow
The equal distribution, improve equipment efficiency.
References:
[A] Keer Sen JM, Li Jiasen J F. Chemical Engineering, Volume Ⅰ [M]. DING Xu
Huai, Yu Cong, etc. translated. 3 version. Beijing: Chemical Industry Press,
1983.
[2] Mechanical Engineering Handbook Electrical Engineering Handbook Part editorial board. No. 7 Fluid
Mechanics [M] / / Mechanical Engineering Handbook. The basic theory Vol. 2nd edition. North
Beijing: Mechanical Industry Press, 1996.
[3] Shanghai Institute of Chemical Technology, Chengdu University of Technology, Dalian Institute of Technology prepared. Chemistry
Project [M]. Beijing: Chemical Industry Press, 1980.
[4] Duma Shinie Fu A Д. Chemical production machinery and equipment [M]. Lin Ji
Fang, Ding-hua, CHEN Yi-jian, etc., translated. Beijing: Chemical Industry Publishing
Society, 1958.