Free Printable Quiz 1 Process Dynamics

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Quiz 1 Process Dynamics

Total questions: 61

Worksheet time: 31mins

Name

Class

Date

A liquid enters a stirred tank heater at a flow rate $F_i$ and temperature $T_i$ . What provides heat to the liquid inside the tank?

Condensing steam in a coil inside the tank

An electric immersion heater

Radiative heating from external lamps

Hot water circulating in an external jacket

Because the tank is well-stirred, the outlet temperature is equal to which temperature?

The liquid temperature inside the tank

The inlet temperature $T_i$

The steam saturation temperature

The ambient room temperature

Select the control objectives stated for the stirred tank heater.

Maintain the outlet temperature $T$ at a desired setpoint $T_s$

Maintain the liquid level (or volume) $V$ in the tank at a desired value

Maximize the steam flow rate to the coil

Minimize the inlet flow rate $F_i$

In the feedback temperature control for the tank heater, which device measures the tank temperature and sends a signal to the controller?

A thermocouple

A manometer

A rotameter

A tachometer

According to the feedback temperature control diagram, which inlet conditions are assumed constant?

Inlet temperature $T_i$ and inlet flow rate $F_i$

Steam flow rate and steam pressure

Outlet flow rate $F$ and outlet temperature $T$

Liquid level $V$ and tank pressure

From the description: In real operation, disturbances such as changes in $F_i$ (feed flow rate) or $T_i$ (feed temperature) occur frequently. Without control, these variations would cause $T$ and $V$ to fluctuate, leading to poor product quality or unsafe conditions. Therefore, a control system is required to automatically adjust the steam flow rate $F_s$ to maintain the desired temperature. Which variable does the control system automatically adjust to maintain the desired temperature?

Steam flow rate $F_s$

Feed flow rate $F_i$

Feed temperature $T_i$

Vessel volume $V$

According to the text on why control is needed, which of the following is explicitly cited as a disturbance in real operation?

Change in feed flow rate $F_i$

Change in vessel volume $V$

Change in controller setpoint $T_s$

Presence of a thermocouple

In a feedback control system: A thermocouple measures the actual liquid temperature $T$ . The controller compares $T$ with the setpoint $T_s$ . The error, $e = T_s - T$ , is sent to the controller. Which device measures the actual liquid temperature?

Thermocouple

Controller

Steam valve

Flow meter

In the feedback temperature control description, how is the error $e$ defined?

$e = T - T_s$

$e = T_s - T$

$e = F_s - F_i$

$e = V - T$

10.

If $T$ is too low ( $e > 0$ ), what action does the controller take according to the feedback temperature control description?

Opens the steam valve to increase heating

Reduces steam flow

Disconnects the thermocouple

Lowers the setpoint $T_s$

11.

If $T$ is too high ( $e < 0$ ), what action does the controller take according to the feedback temperature control description?

Reduces steam flow

Opens the steam valve more

Increases feed flow rate $F_i$

Raises the setpoint $T_s$

12.

What is the stated outcome of automatic adjustment in the feedback temperature control system?

Keeps the process temperature close to the desired value despite disturbances

Maintains feed flow rate $F_i$ at a constant value

Eliminates the need for a thermocouple

Maximizes vessel volume $V$

13.

Key Concept: Feedback control acts after a disturbance affects the system—it measures the deviation and corrects it. In contrast, feedforward control anticipates the effect of disturbances (like changes in $F_i$ or $T_i$ ) and adjusts the steam valve before the process variable deviates. Which statement aligns with the description of feedback control in this passage?

It predicts disturbances and adjusts the valve before any deviation occurs.

It measures the deviation caused by a disturbance and then corrects the system.

It ignores disturbances and maintains a constant valve position.

It compensates by changing setpoints in advance of any change.

14.

It waits for the process variable to deviate and then corrects it.

It anticipates disturbances and adjusts the steam valve before the process variable deviates.

It eliminates the need for measuring disturbances or process variables.

It only responds to deviations that have already occurred.

15.

According to the passage, how are feedback and feedforward strategies commonly used in modern control systems for performance?

They are used independently and never combined.

They are often combined to improve performance.

They are avoided due to complexity.

They are only combined when disturbances cannot be measured.

16.

The passage states that the stability of a process refers to its ability to return to its normal operating condition after being disturbed. Based on this, what does process stability mean?

The ability to return to normal operation after a disturbance

The ability to avoid any deviation from steady state under all conditions

The need for external intervention to recover from disturbances

The tendency to amplify disturbances over time

17.

Consider the variable $x$ shown in the figure described in the passage. At time $t = t_0$ , the process experiences a disturbance that causes $x$ to deviate from its steady-state value. Over time, $x$ gradually returns to its original level without any external intervention. What is this type of system called?

Self-regulating (stable)

Unstable

Chaotic

Externally controlled

18.

The plotted response of the variable $x$ over time shows behavior after a disturbance at $t_0$ . Which behavior best matches the figure described in the passage?

Damped return to steady-state after the disturbance

Constant offset maintained indefinitely after the disturbance

Growing oscillations moving away from steady-state

Immediate snap back to steady-state with no oscillation

19.

The passage gives examples of self-regulating processes that automatically settle back after a small upset. Which of the following are examples of such self-regulating behavior? Select all that apply.

Temperature settling back after a small upset

Concentration automatically returning to its previous level

Flow rate stabilizing after a minor disturbance

An operator manually adjusting a valve to correct a disturbance

20.

Refer to the figure labeled "Unstable," which plots $y$ versus time after a disturbance at $t_0$ with curves A, B, and C and a dashed equilibrium line. Which curve represents behavior that diverges away continuously from the equilibrium after the disturbance?

Curve A

Curve B

Curve C

21.

In the figure labeled "Unstable," which curve corresponds to oscillations with increasing amplitude after the disturbance at $t_0$ ?

Curve A

Curve B

Curve C

22.

According to the figure labeled "Unstable," which curve shows decay without recovery toward the original value after the disturbance at $t_0$ ?

Curve A

Curve B

Curve C

23.

For systems exhibiting the "Unstable" behaviors described (divergence, increasing-amplitude oscillations, or indefinite decay), what is required to maintain stability?

External control

Passive observation

No control

Internal damping alone

24.

Based on the passage, riding a bicycle is inherently which type of system with respect to stability?

Stable

Neutral

Unstable

Self-correcting

25.

To keep a bicycle upright, which actions must be constantly adjusted according to the passage? Select all that apply.

Steering

Pedaling

Shifting body weight

Maintaining a fixed posture

26.

From the excerpt: "Stable System: Returns naturally to steady state (self-regulating). Unstable System: Moves away from steady state unless corrected by control action. A control system plays a crucial role in ensuring that industrial processes remain stable, safe, and predictable despite disturbances." Which statement best defines a stable system?

A system that requires continuous external intervention to avoid drifting from steady state

A system that returns naturally to steady state without external correction

A system that amplifies disturbances to achieve a new operating point

A system that remains at any state regardless of inputs or disturbances

27.

Based on the excerpt: "Stable System: Returns naturally to steady state (self-regulating). Unstable System: Moves away from steady state unless corrected by control action." What characterizes an unstable system?

It maintains steady state without any control action

It moves away from steady state unless corrected by control action

It immediately returns to steady state after a disturbance

It cannot be influenced by control action

28.

According to the statement: "A control system plays a crucial role in ensuring that industrial processes remain stable, safe, and predictable despite disturbances," what is the primary role of a control system in industrial processes?

To introduce disturbances that test system resilience

To ensure processes remain stable, safe, and predictable despite disturbances

To eliminate the need for monitoring and maintenance

To maximize variability to improve flexibility

29.

In Figure 1.9, which plot corresponds to operation near $T_3$ where a small disturbance is followed by a gradual return to $T_3$ , indicating a stable high-temperature steady state?

(a)

(b)

(c)

(d)

30.

According to Figure 1.9, which plot depicts operation near $T_1$ where a disturbance is followed by a smooth return to $T_1$ , indicating a stable low-temperature steady state?

(a)

(b)

(c)

(d)

31.

Which plots in Figure 1.9 illustrate responses when operating near $T_2$ that diverge away from $T_2$ after a small disturbance, demonstrating an unstable middle steady state? Select all that apply.

(a)

(b)

(c)

(d)

32.

In Figure 1.9, for operation near $T_2$ shown in plot (c), what is the final behavior of the temperature after oscillations caused by a small disturbance?

Settles near $T_3$

Settles near $T_1$

Remains near $T_2$

Diverges without settling

33.

In Figure 1.9, for operation near $T_2$ shown in plot (d), what is the final behavior of the temperature after oscillations caused by a small disturbance?

Settles near $T_3$

Settles near $T_1$

Remains near $T_2$

Diverges without settling

34.

In the batch reactor described, two consecutive endothermic reactions occur as shown: $A \xrightarrow{k_1} B \xrightarrow{k_2} C$ . Which species is the desired product?

A and C

35.

In the reaction sequence $A \xrightarrow{k_1} B \xrightarrow{k_2} C$ , which species is identified as an undesired by-product?

None of the above

36.

Heat for the reactions in the batch reactor is supplied by which method?

Direct electrical heating inside the vessel

Steam circulating through a jacket around the reactor

Microwave irradiation of the reacting mixture

Preheated feed continuously added to the reactor

37.

What is the main manipulated variable used to achieve the economic objective in operating the reactor?

Initial concentration of A

Agitator speed

Steam flow rate $Q(t)$

Final cooldown time

38.

The economic goal for operating the reactor is to maximize profit $\Phi$ over the total reaction period $t_R$ . Which statement best describes this objective?

Maximize $\Phi$ by minimizing the production of B and maximizing the production of C over $t_R$ .

Maximize $\Phi$ defined as the integral over $t_R$ of revenue from B minus the cost of steam and the cost of A.

Maximize $\Phi$ by keeping the reactor isothermal and minimizing energy usage without considering product revenue.

Maximize $\Phi$ by minimizing $Q(t)$ irrespective of product formation.

39.

Refer to the figure showing the optimal profile of steam flow rate for a batch reactor. Which description best matches the profile over the batch time t_R?

Starts near $Q_{\max}$ and remains constant

Starts high and then decreases gradually toward near $Q_{\min}$ by the end

Increases steadily from near $Q_{\min}$ to $Q_{\max}$

Stays at zero throughout the batch

40.

Under a high steam flow rate (large Q), which outcome is stated for the reactor performance?

The reactor temperature rises quickly, leading to a high production rate of B

Steam cost is eliminated and the reaction stops

No B is produced

Secondary reactions are completely prevented

41.

What action is recommended near the end of the batch to prevent B from converting into unwanted C?

Increase the steam rate to maintain high temperature

Reduce the steam rate

Keep the steam rate constant at a high level

Add additional reactants to the batch

42.

Which statement about excessive heating due to high steam flow rate is correct?

It decreases steam costs and suppresses side reactions

It increases steam costs and promotes the secondary reaction that forms unwanted C

It has no effect on secondary reactions or costs

It ensures complete conversion of A to B without forming C

43.

When $Q(t)=0)$ (no steam flow), which outcomes are stated for the batch reaction? Select all that apply.

No heating occurs

Steam cost is eliminated

The reaction practically stops

B is produced at a high rate

44.

In practice, how does the optimal steam flow rate vary during the batch cycle to balance production and side reactions?

It remains at $Q_{\max}$ to maximize production of B

It is kept at $Q_{\min}$ to minimize energy consumption

It starts high to accelerate production of B and then gradually decreases to minimize side reactions and energy use

It oscillates randomly to avoid secondary reactions

45.

Refer to the diagram labeled "Figure 1.7 CSTR with cooling jacket," which shows a stirred tank with a cooling jacket, reactant feed, and product outlet. According to the accompanying list, which variable is identified as an input variable?

$c_{Af}$

$c_A$

$V$

$T$

46.

$c_A$

$F_b$

$T_{cj}$

$T_b$

47.

Based on the caption accompanying the diagram, what piece of equipment is depicted?

Continuous stirred-tank reactor (CSTR) with a cooling jacket

Plug flow reactor without heat exchange

Batch reactor with electrical heating

Distillation column with reflux

48.

Based on the listed sets in the figure and text, which set contains the input variables for the shown process?

Fi, Ti, Fst (F)

F, V, T

Steam, Condensate, Volume

Q, h, T

49.

According to the text, which set contains the output variables?

F, V, T

Fi, Ti, Fst (F)

Steam pressure, Coil temperature, Level h

Q, h, inlet temperature

50.

Which statement correctly defines manipulated (or adjustable) variables as classified in the text?

Variables whose values can be adjusted freely by the human operator or a control mechanism

Variables whose values change only due to environmental noise

Variables that cannot be measured directly

Variables that remain constant throughout operation

51.

Which statement correctly defines disturbances in the classification of input variables?

Variables whose values are not the result of adjustment by an operator or a control system

Variables set intentionally to achieve a desired output

Variables measured continuously by sensors

Variables that always equal the outputs

52.

Which statement correctly defines measured output variables?

Output variables whose values are known by directly measuring them

Output variables that cannot be measured directly

Input variables set by the operator

Variables that are calculated but never observed

53.

Which statement correctly defines unmeasured output variables?

Output variables that are not or cannot be measured directly

Output variables known from direct measurement

Input variables adjusted by a control mechanism

Variables whose values are always constant

54.

Based on the described feedback control configuration, which statement best characterizes how the controller operates relative to the controlled variable and set point?

It measures the controlled variable, compares it with the desired set point, and adjusts the manipulated variable to correct any error.

It predicts future values of the controlled variable using disturbance measurements and leaves the manipulated variable unchanged.

It measures unmeasured outputs and resets the set point to eliminate the error.

It adjusts disturbances directly to force the process to match the manipulated variable.

55.

What is the main goal of the feedback control configuration as described?

To keep the controlled variable at its target value even when disturbances occur.

To maximize the effect of disturbances on the controlled variable.

To change the set point whenever the process output varies.

To avoid measuring the controlled variable.

56.

In the feedback control diagram, which signal is directly compared with the set point to produce an error for the controller?

Measured outputs (controlled variables)

Manipulated variables

Unmeasured outputs

Disturbance measurements

57.

According to the feedback control description, which quantity does the controller adjust to correct the error?

Manipulated variable (e.g., valve opening or flow rate)

Set point value

Disturbance magnitude

Unmeasured outputs

58.

Which configuration measures disturbances before they affect the process and adjusts the manipulated variable in advance?

Feedforward control configuration

Feedback control configuration

On–off control configuration

Open-loop scheduling

59.

What is the stated purpose of feedforward control in the description?

To anticipate changes and take corrective action before an error occurs.

To wait for an error and then adjust the set point.

To eliminate the need for manipulated variables.

To measure only the controlled variable and ignore disturbances.

60.

Which example is explicitly given as a feedback control application?

Tank heater temperature control

Flow prediction using disturbance measurements

Disturbance-only regulation

Unmeasured output tracking

61.

Considering the roles of measurement in the two configurations, which statement is correct?

Feedback measures the controlled variable; feedforward measures disturbances before they affect the process.

Both feedback and feedforward measure only unmeasured outputs.

Feedback measures disturbances; feedforward measures the controlled variable.

Neither configuration uses measurements to adjust manipulated variables.

100 %

Quiz 1 Process Dynamics

Total questions: 61

Worksheet time: 31mins

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