Mechanical Engineer Interview Questions and Answers

In this Post, we will discuss Mechanical Engineer Interview Questions and Answers. These Questions and Answers may be helpful at all levels.

Mechanical Engineer Interview Questions and Answers

Q1. What do you mean by COP (Coefficient of Performance)?

Answer: COP or CP is the ratio of “useful heat supplied or removed by the considered system (Q)” and “the work required by the considered system (W)”.

COP= Q/W

The efficiency of the heat pumps and the refrigeration systems are denoted by its COP (Coefficient of Performance).

FOR HEAT PUMPS COP= ENERGY OUT/ENERGY IN.

For the Refrigeration system, the Coefficient of performance is determined by

COP for Refrigeration system = Energy usage of the compressor/ the amount of useful cooling at the evaporator.

A high COP value represents a high efficiency.

Q2. Describe COP of Heating and cooling?

Answer: COP of Heating and cooling

According to the first law of thermodynamics, the total energy of an isolated system is constant. Energy can be transformed from one form to another but can be neither created nor destroyed.

Where QH   is the heat transferred to the hot reservoir and QC  is the heat collected from the cold reservoir

QH = QC + W

W=QH-QC

COP OF HEATING = QH/W = QH/ (QH-QC)

TH & TC ARE THE TEMPERATURES OF RESERVOIRS

So, COP OF HEATING CAN ALSO BE WRITTEN AS

COP OF HEATING= TH/ (TH-TC)

COP OF COOLING = QC/ (QH-QC)

OR

COP OF COOLING = TC/ (TH-TC).

COP OF HEATING is unity (1) more than COP OF COOLING.

Question 3: Describe the Laws of Thermodynamics?

First Law of Thermodynamics- According to the first law of thermodynamics the total energy of an isolated system is constant. Energy can be transformed from one form to another but can be neither created nor destroyed.

Second Law of Thermodynamics

The second law of thermodynamics states that over the time entropy of an isolated system always increases. The second law of thermodynamics also states that the changes in the entropy in the universe can never be negative.

Here it is important to discuss the entropy. Entropy is a function of the state of the system. So, the change in entropy of the system means the change in its initial and final state.

Third law of Thermodynamics

The Third Law of Thermodynamics states that the entropy of a perfect crystalline structure approaches zero as the temperature approaches absolute zero.

Q4. Explain pitting?

Answer: Pitting corrosion or we can say Pitting, is one of the most damaging forms of corrosion. Due to pitting, small holes are formed on the metal surface. Pitting corrosion is more dangerous than uniform corrosion. The Pitting is caused by the environment and lack of uniformity in metal.

Question 5. How hydraulic clutches work?

Answer: The hydraulic clutches has a reservoir containing hydraulic fluid, and, when the clutch pedal is pushed down, the fluid becomes pressurized. It works along with the clutch plate to disengage the gear selected, and engage the new gear.

Question 6. Why Pipes are cylindrical in shape.

Answer: Cylindrical pipes are the most efficient to handle. When water flows through the cylindrical pipe, the pressure force is evenly distributed around the entire circumference of the pipe. A cylindrical pipe bending is easier compared to square pipes. Cylindrical pipes are easier to thread and seal compared to others. Manufacturing of cylindrical pipes is easier also volume calculation for cylindrical pipes is easier.

Q7. How the hydraulic system works?

Answer: A hydraulic drive system uses pressurized hydraulic fluid to power hydraulic machinery. In this system, energy is transferred due to pressure differences, not due to the kinetic energy of the flow. Hydraulic system works on Pascal’s Law.

The hydraulic system consists of the following parts.

The hydraulic pump is driven by an electric motor

Valves, fittings, pipes to guide and control the system

And the actuator for example hydraulic motor or hydraulic cylinder to drive the machinery

Question 8. What is the Role of nitrogen in welding?

Answer: Nitrogen is used to avoid the oxidation due to air from the atmosphere. The purpose of using nitrogen in the welding is to protect the weld area from oxygen and water vapor.

The atmospheric gases can reduce the quality of the weld or make the welding more difficult it depends on the materials being welded.

Question 9. What is the difference between stress and strain?

Answer:  Stress is the load per unit area. Stress can cause strain. Stress is the change in shape or size (deformation) resulting from applied forces.

Question 10. What type of boiler does not need a steam drum?

Answer: Super-critical pressure boiler does not contain a steam drum.

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