JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III PROCESS DYNAMICS AND CONTROL Previous Question Paper (August - 2022 - R18)

A process variable is a physical or chemical property of a process that is measured and controlled to maintain the process at a desired state. A load variable is any external input or disturbance that affects the process variable but is not manipulated by the controller.

Process variables are classified as:

• Controlled Variable (CV): The specific variable that is measured and maintained at a setpoint.
• Manipulated Variable (MV): The input variable that is adjusted by the controller to influence the controlled variable.

Load variables are classified as:

• Measured Load: Disturbances that can be detected and measured before they significantly impact the process, allowing for feedforward control.
• Unmeasured Load: Disturbances that occur randomly or are difficult to quantify, typically handled by feedback control loops.

A non-interacting system is a process configuration where multiple stages or tanks are connected in series such that the output of one stage does not influence the input of the preceding stage. In such systems, the flow from one tank to the next is independent of the liquid level in the downstream tank, often achieved by placing a pump or a restriction between them.

The classification of non-interacting systems is based on the number of stages:

• First-order non-interacting systems: A single process element where the output is determined solely by its own input and parameters.
• Higher-order non-interacting systems: Multiple first-order systems connected in series. The overall transfer function is the product of the individual transfer functions of each stage, represented as:

Because there is no feedback between stages, the characteristic equation is simply the product of the individual denominators, resulting in a system where the total time constant is the sum of individual time constants if the stages are identical.