JNTU
JNTU B.Tech III Year PROCESS DYNAMICS AND CONTROL Previous Question Paper (March - 2021 - R18)
Answer any five questions. All questions carry equal marks.
Main
Discuss the process dynamics of first-order processes with an example.
Answer
A first-order process is characterized by a single energy or material storage capacity and a single resistance to flow. The dynamic behavior is described by a first-order linear differential equation:
The response to a step input is exponential, defined by
Distinguish between interacting and non-interacting systems.
Answer
In a non-interacting system, such as two liquid tanks in series where the second tank is fed by the first without any back-pressure or flow dependence, the dynamics of each tank are independent. The transfer function of the combined system is simply the product of the individual transfer functions:
In an interacting system, the second tank affects the first, typically because the flow between them depends on the levels in both tanks. This coupling means the output of the first stage is a function of the state of the second stage. Consequently, the transfer function cannot be represented as a simple product of independent terms, as the interaction introduces a secondary feedback effect that alters the overall time constants of the system, resulting in a more sluggish response compared to a non-interacting system with the same individual components.
Explain how the basic strategy of control is employed in an industrial furnace heating systems. Is the system is self regulating?
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Write the objectives of process control systems.
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Which one of the three controllers P, PI and PID would give more robust closed loop response to an under-damped second order system? Also give detailed applications.
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A PID controller is at steady state with an output pressure of 9 psig. The set-point and pen-point are initially together. At time t=0, the set-point is moved away from the pen-point at a rate of 0.5 in./min. The motion of the set-point is in the direction of lower readings.
Plot the out-pressure versus time, if the knob settings are Kp = 2 psig/in. of pen travel; Ti = 1.25 min; Td = 0.4 min.
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Also plot the response if suddenly Ti = 0 and other settings remains unchanged.
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What is a controller tuning? Why tuning a controller is necessary?
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How optimum tuning parameters obtained using ISE, IAE and ITAE approaches in controller settings. Also write the correlation among them.
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Explain Pneumatic control valve operation in detail. Also describe its characteristics.
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Develop feedback control system for the following process parameter controls:
- Flow control
- Pressure control
- Temperature control
- Composition control
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Discuss the implementation of feed-forward control and ratio control methods employed in boiler systems. Also write its merits and demerits.
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