What is a disturbance variable?

What is a disturbance variable?

• A. A variable that we have control over in the process
• B. A variable that we have no control over in the process but affects the material or heat flow of a process.
• C. A variable that measures energy efficiency
• D. A constant parameter used for calibration

Answer: (B)

Disturbance variables are external factors you can’t control but that perturb how material or energy moves through a process. They enter the system as exogenous inputs that change flow rates, temperatures, or heat transfer, causing deviations from the ideal or desired behavior. This is different from variables you deliberately set (manipulated inputs) and from fixed constants or performance metrics. In practice, disturbances could be fluctuations in feed temperature, feed rate, ambient conditions, or changes in heat transfer coefficients due to fouling or weather. Modeling them helps predict how the process will respond and supports designing controllers that reject or attenuate their effects.

Disturbance variables are external factors you can’t control but that perturb how material or energy moves through a process. They enter the system as exogenous inputs that change flow rates, temperatures, or heat transfer, causing deviations from the ideal or desired behavior. This is different from variables you deliberately set (manipulated inputs) and from fixed constants or performance metrics. In practice, disturbances could be fluctuations in feed temperature, feed rate, ambient conditions, or changes in heat transfer coefficients due to fouling or weather. Modeling them helps predict how the process will respond and supports designing controllers that reject or attenuate their effects.