Top 20 Mechanical Engineer Interview Questions
This is the second part of the mechanical engineering viva questions. This part mainly discusses the common questions of refrigeration, air conditioning systems and some thermodynamics If You haven’t read the first part then go through link.
Automobile engineering interview questions
- What is Refrigeration? What is the unit of refrigeration?
Ans. Refrigeration is the process where heat is transferred from low temperature to high-temperature medium with the help of external work. Its unit is ton of refrigeration.
2. What is COP?
Ans. COP = Coefficient of Performance. It is used to measure the performance of a refrigeration system. It is generally expressed by the ratio of evaporation work or refrigeration effect to the compressor work or network.
3. What is a ton of refrigeration?
Ans. 1 ton of refrigeration means heat absorbed while melting 1 ton (2000 lb) of ice at zero degree Celsius at 24 hours.
4. What is BTU?
Ans. BTU = British Thermal Unit; 1 BTU is the amount of heat required to raise the temperature of one lb water by one degree Fahrenheit.
5. What is sub-cooling and superheating in refrigeration system ? Why these are used?
Ans. Sub-cooling or under cooling is done before throttling or expanding the refrigerant and it ensures that no vapor enters the expansion valve.
Super-heating is done before compression and it ensures that no liquid enters the compressor.
6. Which thermodynamic cycle is implied in the refrigeration system?answer: Reversed Carnot or Reversed Rankin Cycle.
Ans. Reversed Carnot or Reversed Rankin Cycle.
Top 20 Mechanical Engineer Interview Questions
7. What is the most commonly used refrigerant?
Ans. R134a
8. What is Vapor compression and Vapor Absorption Refrigeration system ?
Ans. (Difference between) / What are the advantages of Vapor absorption systems over Vapor compression?answer: Please follow this link for the answer – Vapor Compression Vs Vapor Absorption Refrigeration System
Detect absorbers and refrigerant in these systems – Li-Br and NH3 – H2O.answer: In Li-Br – Water is the refrigerant and Li-Br is the absorbent.
Detect absorbers and refrigerant in these systems – Li-Br and NH3 – H2O.answer: In Li-Br – Water is the refrigerant and Li-Br is the absorbent.
In NH3 – H2O: NH3 is the refrigerant and water is absorber.
Top 20 Mechanical Engineer Interview Questions
9. What is the LMTD method?
Ans. LMTD refers to Logarithmic Mean Temperature Difference. It is used to measure the temperature difference in double pipe heat exchangers. The more the LMTD the more heat will be transferred.
10. What is the difference between a cooler and an air conditioner?
Ans. For a cooler to become air conditioner it must meet the following requirements :
It must control the 1. temperature 2. Humidity 3. the motion of air 4. purity of air.
11. What is the difference between cooling tower and condenser?
Ans. Condenser is a heat exchanger which converts saturated vapor into liquid. For doing so the condenser temperature must be below than the saturation temp.
A cooling tower is a device in which recirculating condenser water is cooled by the evaporative method with direct contact to the atmosphere.
Top 20 Mechanical Engineer Interview Questions
12. What is a chiller?
Ans. Chiller is a device/machine for cooling something. (I will be writing some articles about chillers very soon)
13. What is the second law of thermodynamics?
Ans. The second law of thermodynamic depicts that the total entropy of an isolated system can never reduce over time.
14. What is ferrite?
Ans. Ferrite is a magnetic iron rock.
Top 20 Mechanical Engineer Interview Questions
15. Which pipes are used for steam lines?
Ans. Steel pipes with welded fitting are used for steam lines.
16. Distinguish between the shear center and elastic center.
Ans. The shear center is a center where the force can act with no twist, whereas elastic center is located at the center of gravity.
17. Name two vital conditions of a perfect gas.
Ans. Two vital conditions of perfect gas are:
• It should satisfy the state equation.
• Specific heat remains constant.
18. What is the meaning of the term Greenfield Project?
Ans. A Greenfield Project refers to a project that has been built from scratch and has been built in a way that does not cause pollution.
19. What is meant by pitting?
Ans. Pitting is when there is a small hole in the metal due to corrosion.
20. What is knurling?
Ans. Knurling is the process of creating a pattern on a bar that can be used as a handle.
