Indicate whether the following statements are true or false. Explain.

1. The energy of simple compressible systems can be changed by energy transfer and by work associated with volume change.
2. A polytropic process with n ≠ k is adiabatic.
3. When an ideal gas undergoes a polytropic process with n = 1, the gas temperature remains constant.
4. The tires of airplanes and race cars inflated with oxygen instead of air.
5. Given temperature and specific volume of a two-phase liquid–vapor mixture, you cannot determine the specific internal energy.
6. The properties of velocity and elevation are included in the specification of an intensive thermodynamic state.

Air at Mach 1.8 at an altitude of 8 km ISA, passes through a normal shockwave.

a) Calculate the velocity of the flow in units of metres per second after the shock wave.

b) Calculate the change in specific entropy across the shockwave. Make sure you

include the appropriate units in your answer.

1. Define mass density and specific weight.
2. Define specific volume.
3. Define specific gravity.

Question 1

A copper tube having a cross-sectional area of 2000 mm² and length of 300 mm is placed between two rigid caps. Four 22 mm diameter steel bolts are symmetrically arranged parallel to the axis of the tube and are lightly fastened. Calculate:

1. The stress in the tube if the temperature of the assembly is raised by 70⁰C.
2. The load each bolt will carry at the raised temperature.                                  

            E_ST = 200 GPa;   α_ST = 12 x 10^-6 / ⁰C         

           E_CU = 100 GPa;   α_CU = 16 x 10^-6 / ⁰C

Air enters the compressor of a simple gas turbine at p₁ = 14 lbf/in², T₁ = 520°R. The isentropic efficiencies of the compressor and turbine are 83 and 87%, respectively. The compressor pressure ratio is 16 and the temperature at the turbine inlet is 2500°R. The volumetric flow rate of the air entering the compressor is 9000 ft³/min. Use an air-standard analysis.

Determine all temperatures at each state.

A) Determine the net power developed, in Btu/h.

B) Determine the thermal efficiency of the cycle

C) the temperatures at the compressor and turbine exits in °R

Calculate the temperature T of 40 kg of CO2 gas in a 500 liter vessel at 5 MPa. The critical pressure of CO2 is 7.39 MPa and the critical temperature is 31.05 ºC: also, specify the value of Z.

What type of tool or technique you are suggesting to choose appropriate materials, methods and machines to take decision on enhance existing production cell? Why do you prefer that tool or technique?

An exhaust fan systems consists of 4 parallel v-belts wrapped around driver pulleys A and driven pulley B with a diameter of 100 mm and 240 mm respectively. Coefficient of friction, μ between belt and pulleys is known as 0.25. Pulley groove, α has been design at an angle of 60°. The maximum permissible tension is 3860 N, cross-sectional area of the belt is A = 160 mm2 and density of belt’s material ρ = 1000 kg/m3. If the driver pulley A and driven pulley B rotates at a speed of 1800 RPM and 700 RPM individually due to slippages.

(i) Find the angle of contact of pulley A, given the pulley centre to centre distance is 1000 mm.

(ii) Calculate the tension distributed by centrifugal forces in one V-belt.

(iii) Deduce total power transmitted by the driver pulley A.

(iv) Deduce total power received by the driven pulley B.

(v) Find the belt slip percentage at pulley B

Find the critical path and critical time for the following business network:
Activity Pre. Act. Duration
A - 18
B A 25
C B 1
D C 14
E C 12
F E 1
G D 18
H E,G 3
I C 14
J F,I 16
K J 5
L J 25
M H 22
N K,L 13

The figure below gives data for an ideal vapor-compression heat pump cycle operating at steady state with Refrigerant 134a as the working fluid. The heat pump provides heating at a rate of 15 kW to maintain the interior of a building at T_H = 20°C when the outside temperature is T_C = 0°C.

Determine:

(a) the temperatures at the principal states of the cycle, each in °C.

(b) the power input to the compressor, in kW.

(c) the coefficient of performance.

(d) the coefficient of performance for a Carnot heat pump cycle operating between reservoirs at the building interior and outside temperatures, respectively.

A local elevator moves upward at a constant 3.3 mps passing a stopped express elevator. Precisely 2.8 seconds later the express elevator starts upward with a constant acceleration and catches up with the local elevator where the velocity of the local with respect to the express elevator is -9.3 m/s. Determine (a) the acceleration of the express elevator in m/s/s and (b) the distance traveled in m for the express to catch up with the local elevator.

q1) Fluid ( ρ = 850 kg/m³; μ = 0.08 Pa.s) flows through a 4-cm diameter tube at 0.5 m/s. The Reynolds number of the fluid is

q2 ) An oil with ρ= 900 kg/m³ and ν= 2x10^-4 m²/s flows upward through an inclined pipe of diameter 4 cm as shown in Fig. 1. The pressures at sections 1 and 2 (L =11.3 m apart) are p₁ = 359 kPa and p₂ = 201 kPa, respectively. Assuming steady laminar flow, compute the average velocity; in m/s.

q3) Fluid ( ρ = 850 kg/m³; μ = 0.08 Pa.s) flows through a 4-cm diameter tube at 50 m/s. The flow characterizes as:

Q4) The hydrodynamic entry length of laminar flow fluid ( S.G = 0.985 ; ν = 1.47x10^-5 m²/s) flowing through tube at 0.13 m/s is 27.6 cm. The tube diameter is:

Q) Fluid ( S.G = 0.985 ; ν = 1.47x10^-5 m²/s) flows through a 5-mm diameter tube at 3.3 m/s. The hydrodynamic entry length of this flow is:

Q6) Fluid ( S.G = 0.985 ; μ = 1.47x10^-2 Pa.s) flows through a 15-cm diameter tube at 3.3 m/s. The hydrodynamic entry length of this flow is:

When aging an aluminum alloy, the final hardness depends on time at the heat treatment temperature. The time to achieve peak age (maximum hardness):

Question 1

a) Determine the specific enthalpy of steam at 15 bar and 275°C .

b) Determine the degree of superheat and entropy of steam at 10 bar and 380 °C.

c) A superheated steam at 12.5 MN/m2 is at 650°C .Determine its specific volume.

Question 2

A superheated steam at 24 bar and 500 °C expands at constant volume until the pressure becomes 6 bar and the dryness fraction is 0.9. Calculate the changes in the internal energy of steam. Sketch the process in the form of a P-v diagram.

Question 3

Steam at 10 bar and 200 °C enters a convergent-divergent nozzle with a velocity of 60 m/s and leaves at 1.5 bar and with a velocity of 650 m/s. Assuming that there is no heat loss, determine the quality of steam leaving the nozzle.

Question 4

The temperature of feed water entering a boiler is 311 °C and steam is produced at 40 bar and 500 °C. The rate of heat transfer to the surroundings is 35 kW. Determine the mass flow rate of the working fluid for a heat input to the boiler of 6 MW.

Question 5

Exhaust steam from a turbine enters a condenser with a specific enthalpy of 2164 kJ/kg and a velocity of 75 m/s. During the cooling process, the heat loss to the cooling water per kg of working fluid is 1680 kJ/kg. The condensate exits the system with a velocity of 12 m/s. Sketch a systems diagram for the condenser and determine the specific enthalpy of the working fluid at exit from the condenser.

Question 6

A steady flow boiler is supplied with water at 15 kg/s, 100 bar pressure, and 200 °C. The water is heated and turned into steam. The steam leaves at 100 bar and 500 °C. Determine the heat transfer rate.