The flow valves and flow rate depending on the size of valve, also associated with the structure of medium resistance of the valve, with the pressure of the valve at the same time, temperature and the concentration of the medium has a certain internal relation factors.
Port area and the velocity and flow of the valve has a direct relationship, but the flow velocity and flow rate are two interdependent. When traffic must flow velocity, flow area can be smaller; Small flow rate, flow area can be larger. On the other hand, the flow channel area is large, its velocity is small; Port area is small, its velocity.
Medium velocity is large, valve size can be smaller, but the resistance loss is bigger, is easy to damage the valve. Velocity of flammable and explosive medium can produce electrostatic effect, dangerous; The flow rate is too small, the efficiency is low, not economic. On viscosity and explosive medium, should take smaller flow velocity. Oil and the viscosity of the liquid with viscosity size choose velocity, generally take 0.1 ~ 2 m/s.
Under normal circumstances, the traffic is known, the velocity can be determined by experience. Through the flow velocity and flow valve nominal diameter can be calculated.
Valve size is the same, its structure is different, the fluid resistance is different also. Under the same conditions, the greater the resistance coefficient of valve, the more fluid flow velocity and flow rate drop across the valve; The smaller the resistance coefficient of valve, the less fluid flow velocity and flow rate drop across the valve.
All kinds of commonly used medium velocity see the table below.
The name of the fluid
Conditions of use
The velocity
(m/s)
Saturated steam
DN > 200
DN = 200 ~ 100
DN < 100
30 ~ 40
25 to 35
15 ~ 30
Superheated steam
DN > 200
DN = 200 ~ 100
DN < 100
40 ~ 60
30 ~ 50
20 ~ 40
Low pressure steam
Rho < 1.0 (pabs)
15 ~ 20
Medium pressure steam
Ρ = 1.0 ~ 4.0 (pabs)
20 ~ 40
High pressure steam
Ρ = 4.0 ~ 12.0 (pabs)
40 ~ 60
Compressed gas
vacuum
Ρ acuities were pressure (table 0.3)
Ρ = 0.3 ~ 0.6 (gauge pressure)
Ρ = 0.6 ~ 1.0 (gauge pressure)
Ρ = 1.0 ~ 2.0 (gauge pressure)
Ρ = 2.0 ~ 3.0 (gauge pressure)
Ρ = 3.0 ~ 30.0 (gauge pressure)
