JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III PROCESS DYNAMICS AND CONTROL Previous Question Paper (September - 2021 - R18)

A process variable is a physical or chemical quantity within a process that is measured and controlled to ensure the desired operation. These variables represent the state of the system and are categorized based on their role in the control loop.

The primary types of process variables are:

• Controlled Variable (CV): The specific process parameter that must be maintained at a setpoint. Example: The temperature of a chemical reactor.
• Manipulated Variable (MV): The variable adjusted by the controller to influence the controlled variable. Example: The flow rate of cooling water entering the reactor jacket.
• Disturbance Variable (DV): An uncontrolled input that affects the process and causes the controlled variable to deviate from the setpoint. Example: A sudden change in the ambient temperature or feed composition.

In a continuous process, raw materials are fed and products are removed simultaneously, making it ideal for high-volume industries like oil refineries and power plants. In contrast, a batch process involves processing a fixed amount of material through a series of steps, commonly used in pharmaceutical manufacturing, specialty chemicals, and food processing where product variety and precise quality control for smaller quantities are required.