Mechanical Engineering Answers

A steady stream of air enters a horizontal compressor at the rate of 0.02 kg/s. The air temperature is 10o C at entry and 300o C at exit. The velocity of the air is 30 m/s at entry and 6 m/s at exit. During its passage through the compressor, the air experiences a heat loss of 105 kJ/kg of air. Calculate: (a) The change in kinetic energy per kg of air (b) The change in enthalpy per kg of air (c) The work done per kg of air (d) The power required to drive the compressor (e) The volume of air entering the compressor per second (f) The flow area of the entry pipe if the entry pressure is 1 bar Take R = 0.287 kJ/kgK and cp = 1.005 kJ/kgK

In a Rankine cycle, what is the entrance pressure of the turbine if the condenser

pressure is 105 KPa and the pump work is 20 KJ/kg. Use density of water entering the

pump, 950 kg/m

Choose a quantity to be represented by a variable, then write a mathematical expression for each.

1. The product of three consecutive integers

2.. Jose's age in 10 years

3. The distance traveled by a man driving at the rate of 45 kph

4. The total amount in pesos of 30 coins consisting of 5-peso coins and 10-peso coins

5. The sum of three consecutive odd integers

6. The fraction of work done by a man who can finish a job in three days

7. The total interest after one year if a fraction of P500 000 is invested at 5% annual interest rate and the remaining part is invested at 7.5% annual interest rate

8. A three-digit number whose hundreds digit is twice its tens digit and the tens digit is 3 more than the units digit

9. The percentage of alcohol in a mixture formed by combining 1.5 liter of pure water and x liters of 30% alcohol solution.

10. The total distance traveled by a boat 1 hour and 20 minutes upstream and 40 minutes downstream if the rate of the current is 3 kph.

2.) An asset costing P50,000 has a life expectancy of 6 years and an estimated salvage value of P8,000. Calculate the depreciation charge at the end of the fourth period using fixed-percentage method.

In 8m3 of atmospheric air at 10°C temperature are compressed to volume of 2m3 at 100°C.

Derive the equation for the unit step response of a first order low-pass system

Steam at a temperature of 250oC has a specific volume of 0.15436 m3/kg . What are the pressure , specific internal energy, enthalpy, and entropy? Use the Keenan Steam Table

The power input to the fan is 50 J/s and the power input to the heating element is 1.44 kJ/s. The air enters the fan with negligible velocity at a pressure of 1 bar and a temperature of 20 C, the volumetric flow rate being 0.5 m3 /min. After passing over the heating element, the air leaves the nozzle with a velocity of 25 m/s and a pressure of 1.1 bar. Treating the complete arrangement as a steady flow system and ignoring any heat loss from the system, determine: (a) The mass flow rate of air entering the fan in kg per second (b) The kinetic energy of the air leaving the nozzle per second (c) The change in enthalpy of the air occurring per second between entering the fan and leaving the nozzle (d) The temperature of the air as it leaves the nozzle. (e) The density of the air as it leaves the nozzle (f) The flow area at the nozzle exit. Take R = 0.287 kJ/kgK and cp = 1.005 kJ/kgK

 Derive the transfer function 𝐺1 (𝑠) = 𝑋(𝑠)/𝑈(𝑠) for the first-order system given by the dynamic equation 𝑑x/𝑑𝑡 + 𝑘𝑥 = 𝑢(𝑡). [2]

A thermal power plant generates 4000 KW and 400 KW for auxiliaries. Determine th net thermal efficiency if the heat generated by fuel is 15,000 KW.