⚛️ NPCIL Interview Experience – Mechanical Engineering (GATE 2025)

• Date: 14th June 2025
• Venue: Kalpakkam, Tamil Nadu
• Duration: ~35–40 minutes
• Panel: Friendly and technically strong – multiple members

Introduction & Atmosphere:

The interview began on a friendly note. The panel tried to ease my nerves by cracking a light joke and casually asked:

• “Is this your first interview or have you attended any earlier?”
• “Why didn’t you apply for BARC?”

Then, they asked me which subjects I was most comfortable with. I responded:
Thermodynamics, Heat Transfer, Fluid Mechanics, and Strength of Materials.

Technical Questions and Discussion:

1. Cross-Flow Heat Exchangers:
   • “Can you give real-life examples of cross-flow heat exchangers?”
2. Fins and Heat Transfer:
   • “When do we use fins?”
   • “What’s the difference between efficiency and effectiveness of a fin?”
   • Given a slab with water on one side and air on the other:
     • “Which side will have a higher heat transfer coefficient?”
     • “On which side should we place the fins, and why?”
3. Sustainability and Energy Storage:
   • “Suppose we stop using fossil fuels and rely completely on solar and wind energy — what challenges would arise and how can they be overcome?”
   • “What energy storage methods exist apart from batteries?”
   • Given a hydropower setup where a turbine lifts water using a pump:
     • “Which energy conversion — turbine or pump — results in more losses?”
     • “Can this setup function as a battery system to store energy?”
4. Engines and Power Plants:
   • “What is the compression ratio of SI and CI engines? Which one is more efficient and why?”
   • “Why are thermal power plants usually located near water reservoirs?”
   • “Since this plant is near the sea, can we use sea water in the condenser? What precautions must be taken?”
5. Plant Efficiency and Types:
   • “What is the efficiency of a typical thermal power plant?”
   • “What are the differences between supercritical and subcritical power plants?”
   • “In which type of plant is the load on the condenser lower for the same power output?”

Additional Mechanical & Practical Application Questions:

6. Frequency and RPM Relation:
   • “What is the frequency of electrical power supply in India?”
     • (Expected answer: 50 Hz)
   • “What is the corresponding RPM of a turbine shaft at this frequency?”
     • (Hint: Use RPM=120×fP\text{RPM} = \frac{120 \times f}{P}RPM=P120×f​, where f is frequency and P is number of poles)
7. Speed Reduction Mechanism:
   • “If we want to reduce shaft speed from input to output, what mechanical system can we use?”
     • (Expected answer: Gearbox, pulley-belt system, or reducer)
8. Power Bill and Units:
   • “Have you ever paid your electricity bill?”
   • “What is the cost of one unit of electricity?”
   • “What does one unit of power mean?”
     • (Expected: 1 unit = 1 kWh = 1000 watts used for 1 hour)
9. See-Saw Concept – Real Life to Mechanics:
   • “Do you know what a see-saw is? Have you ever played on one?”
   • Asked me to:
     • Draw its structure on the whiteboard.
     • Identify and explain its mechanical parts.
     • Draw the Shear Force Diagram (SFD) and Bending Moment Diagram (BMD).
     • Asked: “If the two persons on either side have unequal weights, how can the see-saw be balanced?”
     • Final question: “Is the see-saw a cantilever beam or a simply supported beam?”

Performance Summary:

• ✅ Strong Areas: Heat transfer, real-life mechanical systems, sustainability-based questions, and fluid mechanics
• 🟡 Moderate Areas: Advanced control systems, precise RPM-frequency calculations, and BMD/SFD under asymmetrical loads

The interview was well-balanced between conceptual depth, practical relevance, and real-world application of mechanical engineering principles. The panel encouraged whiteboard usage for drawing and logical reasoning.

Current Status: Result Awaited