Calculate steam blowing disturbance factor from blow and MCR density and velocity, or solve any missing density or velocity value.
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Disturbance Factor (Steam Blowing) Formula
The disturbance factor compares the dynamic pressure during steam blowing to the dynamic pressure at maximum continuous rating, usually called MCR. The calculator uses density and velocity at both conditions.
DF = (0.5*rho_b*V_b^2)/(0.5*rho_m*V_m^2)
The 0.5 terms cancel, so the same formula can also be written as:
DF = (rho_b*V_b^2)/(rho_m*V_m^2)
Rearranged formulas for solving a missing input:
rho_b = (DF*rho_m*V_m^2)/(V_b^2)
V_b = sqrt((DF*rho_m*V_m^2)/rho_b)
rho_m = (rho_b*V_b^2)/(DF*V_m^2)
V_m = sqrt((rho_b*V_b^2)/(DF*rho_m))
- DF = disturbance factor, unitless
- rho_b = density at blow condition
- V_b = velocity at blow condition
- rho_m = density at MCR condition
- V_m = velocity at MCR condition
The density inputs may be entered in kg/m³, g/cm³, or lb/ft³. The velocity inputs may be entered in m/s, km/h, or ft/s. The calculator converts these values to base units before applying the formula.
If disturbance factor is the missing value, the calculator divides the blow-condition dynamic pressure by the MCR dynamic pressure. If one of the density or velocity values is missing, it rearranges the same equation to solve that specific variable.
Common Unit Conversions for Steam Blowing Calculations
Use these conversions when checking values by hand or comparing data from different sources.
| Quantity | Unit | Conversion to base unit |
|---|---|---|
| Density | kg/m³ | 1 kg/m³ |
| Density | g/cm³ | 1 g/cm³ = 1000 kg/m³ |
| Density | lb/ft³ | 1 lb/ft³ = 16.0185 kg/m³ |
| Velocity | m/s | 1 m/s |
| Velocity | km/h | 1 km/h = 0.277778 m/s |
| Velocity | ft/s | 1 ft/s = 0.3048 m/s |
Disturbance Factor Result Guide
| Disturbance factor | Meaning |
|---|---|
| Less than 1.0 | The blow condition has lower dynamic effect than the MCR condition. |
| Equal to 1.0 | The blow condition and MCR condition have the same dynamic pressure basis. |
| Greater than 1.0 | The blow condition is more severe than the MCR condition. |
Example
Example 1: Calculate disturbance factor
Suppose the density at blow condition is 4 kg/m³, the velocity at blow condition is 220 m/s, the density at MCR is 5 kg/m³, and the velocity at MCR is 160 m/s.
DF = (4*220^2)/(5*160^2)
DF = 193600/128000 = 1.5125
The disturbance factor is 1.5125.
Example 2: Calculate velocity at blow condition
Suppose the disturbance factor is 1.5, the density at blow condition is 4 kg/m³, the density at MCR is 5 kg/m³, and the velocity at MCR is 160 m/s.
V_b = sqrt((1.5*5*160^2)/4)
V_b = sqrt(48000) = 219.0890 m/s
The velocity at blow condition is 219.0890 m/s.
FAQ
What does disturbance factor mean in steam blowing?
Disturbance factor is a ratio of dynamic pressure at the steam blowing condition to dynamic pressure at the MCR condition. A higher value means the steam blow produces a stronger cleaning effect relative to normal rated operation.
Why is velocity squared in the disturbance factor formula?
Dynamic pressure is proportional to density times velocity squared. Because velocity is squared, a small increase in velocity can cause a much larger increase in disturbance factor.
Does disturbance factor have a unit?
No. Disturbance factor is unitless because it is a ratio of two dynamic pressure terms. The density and velocity units still matter during calculation, so values must be converted consistently before applying the formula.
