FE Mechanical Practice Question Solution included after investigation
CASE E-052 Β· FE

The Turbine That Produced 1.2 MW From an Enthalpy Drop

The turbine power came from a 600 kJ/kg enthalpy drop, not from subtracting internal energies blindly.

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Case E-052 engineering failure visual
HOW THIS WORKS

Think like
a real engineer.

Follow the investigation process used in the field β€” in five guided steps.

1

Inspect

Review the problem, diagram, and evidence.

2

Commit

Choose your hypothesis.

3

Prove

Run calculations and test your idea.

4

Fix

Select and validate a safe correction.

5

Sign Off

See the full debrief and key takeaways.

Case Brief

SAME PRINCIPLES. HIGHER STANDARDS.
PROBLEM STATEMENT

Steam enters an adiabatic turbine at 2 kg/s with h1=3200 kJ/kg and exits with h2=2600 kJ/kg. Changes in kinetic and potential energy are negligible. A calculation reports -1.2 MW because it uses h2-h1 as turbine output. Determine the correct shaft power output and identify the sign/model error.

Thermodynamics Mechanical Design Verification Root Cause Analysis Safe Correction
E-052
INVESTIGATION WORKSPACE WORK THROUGH THE CASE β€” YOUR CHOICES MATTER.
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CASE CLOSED Β· ENGINEERING VERDICT

What actually failed β€” and what should change.

What failed

The enthalpy difference was given the wrong sign for turbine output.

What was missed

An open steady-flow device is naturally analyzed with enthalpy.

Corrected model

For the stated case, Wdot_out=mdot(h1-h2).

QUICK ANSWER

For an adiabatic turbine with negligible kinetic and potential energy changes, Wdot_out=mdot(h1-h2). At 2 kg/s with h1=3200 and h2=2600 kJ/kg, the output is 2Γ—600=1200 kW, or 1.2 MW.

ENGINEERING TAKEAWAY

For a steady adiabatic turbine with negligible kinetic and potential energy changes, shaft power out equals mass flow rate times inlet-minus-outlet enthalpy.

CASE QUESTIONS

Questions this case should settle.

Why is enthalpy used for turbines instead of only internal energy?

Enthalpy includes internal energy plus the flow-work term needed for steady-flow control-volume analysis.

What is the turbine power for a 600 kJ/kg enthalpy drop at 2 kg/s?

1200 kW.

NEXT FE PRACTICE QUESTION

The Refrigerator With a COP Greater Than One

Thermodynamics Β· 5–10 min

Continue Practice β†’
WHAT YOU’LL LEARN

Real failures. Lasting skills.

Each case is designed to build the judgment, analysis, and confidence you need for engineering exams β€” and beyond.

  • Apply core engineering concepts to real-world problems
  • Practice structured troubleshooting and analysis
  • Strengthen exam-ready thinking through realistic scenarios
COMMON QUESTIONS
Do I need prior knowledge to use these cases?

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Are the cases aligned with engineering exams?

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What happens after I complete a case?

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