Mechanical Engineering Questions with Answers

What is a Gibbs Phase Rule

Gibbs phase rule states that for a heterogeneous system in equilibrium with C components in P phases, the degree of freedom F = C - P + 2.

What is an ideal Refrigeration Cycle?

The ideal refrigeration cycle is reverse of Carnot cycle, working as a heat pump instead of as a heat engine.

What is Psychrometry?

Psychrometry is the study of air and water vapor mixtures for air conditioning

What is the difference between Absolute humidity and relative humidity.

The absolute humidity ω is the ratio of masses of the vapor and air, i.e., ω = m_v/m_a. The relative humidity φ is the ratio of the vapor pressure to the saturation vapor pressure at that temperature, i.e., φ = p_v/p_v,sat.

What is saturation ration with reference to air conditioning

The saturation ratio is the ratio of the absolute humidity to the absolute humidity at saturation, or, ψ = ω/ω_sat.

Q: The temperature of a place is 35 °C with a relative humidity of 40%. Can it be cooled using a conventional air cooler?

Ans: We need to find the wet bulb temperature for the point T = 35°C and φ = 40% using a Psychrometric Chart. As per the chart, the wet bulb temperature is between 20 and 25°C. So the place can be cooled down to a comfortable temperature using an evaporative cooler.

Q: The temperature of a palce is 37 °C with relative humidity of 83%. To what temperature can it be cooled using a conventional air cooler?

Ans: The wet bulb temperature is about 34.2°C for this situation. Thus, ordinary cooler cannot be used to reduce room temperature. You will need to use an air conditioner.

Q: What is the device used in ships and submarines to control buoyancy and stability?

Ans: Ballast Tank

Q: What is the latest trend in Predictive Maintenance?

Ans: Model Based Condition Monitoring

Q: What is Model Based Condition Monitoring

This method involves spectral analysis on the motor’s current and voltage signals and then compares the measured parameters to a known and learned model of the motor to diagnose various electrical and mechanical anomalies

Q: What is TPM

Ans: Total Productive Management (TPM) is a system of maintaining and improving the integrity of production and quality systems through the machines, equipment, processes, and employees that add business value to an organization.

Q: As per TPM, how Overall Equipment Effectiveness is calculated?

Ans: OEE has three factors which are multiplied to give one measure called OEE
Performance x Availability x Quality = OEE

Each factor has two associated losses making 6 in total, these 6 losses are as follows:

Performance = (1) running at reduced speed - (2) Minor Stops

Availability = (3) Breakdowns - (4) Product changeover

Quality = (5) Startup rejects - (6) Running rejects

Q: What is the difference between TPM and TQM ?

Ans: TQM focuses on the quality of the product, while TPM focuses on the equipment used to produce the products. TQM and TPM can both result in an increase of quality. TPM can be seen as a way to help achieving the goal of TQM