Please explain the effect of size of supercooled region, present just ahead of liquid solid interface, on the shape/type of liquid solid interface and eventually on the final microstructure of an alloy during freezing

SUBJECT PHASE

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.