A converging–diverging nozzle is designed to generate an exit Mach number of 2. The nozzle is supplied with air from a large reservoir in which the pressure is kept at 6.5 MPa. Assuming one-dimensional isentropic flow, find

a. The maximum back-pressure at which the nozzle will be choked

b. The range of back-pressures over which there will be a shock in the nozzle

c. The design back-pressure

d. The range of back-pressures over which there is supersonic flow on the nozzle exit plane

. A rectangular steel bar is subjected to a fluctuating load from 30 kN tension to 30 kN compression. The bar is 30 mm wide and 7 mm thick with a hole in the middle that is 4 mm in diameter. Find the fatigue and yield factor of safety if the steel is cold-drawn AISI 1040. If the fatigue factor nf<1 and ny>1 then that means that the system will fail at a finite number of cycles. If that is the case, estimate the number of cycles to failure.

1a. Spheroidite steel is a good example of Metal Matrix Composite material. What are the matrix material and the dispersed phase acting as a reinforcing agent?

1b. Name one material that is commonly used as the fibers in fiber reinforced composites.

2a. In metals increasing “imperfections” e.g. grain boundaries, dislocations, vacancies in the material will increase or decrease the resistivity of that material? Briefly explain why.

2b. Does the resistivity of a copper increase or decrease when it is heated to a higher temperature? Briefly states why.

1a. Spheroidite steel is a good example of Metal Matrix Composite material. What are the matrix material and the dispersed phase acting as a reinforcing agent?

1b. Name one material that is commonly used as the fibers in fiber reinforced composites.

2a. In metals increasing “imperfections” e.g. grain boundaries, dislocations, vacancies in the material will increase or decrease the resistivity of that material? Briefly explain why.

2b. Does the resistivity of a copper increase or decrease when it is heated to a higher temperature? Briefly states why.

A pump has a displacement volume of 8 in3. It delivers 20 gpm at 800 rpm and 1100 psi. If the prime mover input torque is 2000 in · lb, a) What is the volumetric efficiency? b) What is the mechanical efficiency? c) What is the overall efficiency? d) What is the theoretical torque required to operate the pump?

Air expands through a turbine operating at steady state. At the inlet, p₁ = 150 lbf/in.², T₁ = 1400°R, and at the exit, p₂ = 14.8 lbf/in.², T₂ = 900°R. The mass flow rate of air entering the turbine is 5 lb/s, and 65,000 Btu/h of energy is rejected by heat transfer.

Neglecting kinetic and potential energy effects, determine the power developed, in hp.

Given:

• Stagnation-to-Stagnation pressure ratio P02/P01 = 3.0

• Mass flow rate m= 0.8 kg

• Inlet stagnation conditions of To1 = 295 K and Po1 = 100 kPa

• Tip speed U2 < 500 m/s

• Inlet hub radius d1h ≥ 0.04 m

• Isentropic efficiency ηisen ≥ 80%

Calculate Hydraulic Pump Power and Shaft Pump Power ?

The state at the beginning of compression of an air-standard Diesel cycle is fixed by p₁ = 100 kPa and T₁ = 310 K. The compression ratio is 18 and the cutoff ratio is 1.5.


Determine:

(a) the maximum temperature, in K.

(b) the pressure at the end of the expansion, in kPa.

(c) the net work per unit mass of air, in kJ/kg.

(d) the percent thermal efficiency.

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 the net power developed, in Btu/h.

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 the net power developed, in Btu/h.

Q3. 5 kg of water at T = 20° C and P = 7 bar is isobarically heated such that ΔU = 5000 kJ. (i) Find the initial and final volumes (in m3 ). (ii) Find Q and W (in kJ). (iii) Show the initial and final states on p-υ and T-υ diagrams (not to scale), denoting by arrows the direction of the process. Label the ‘f’ (saturated liquid) and ‘g’ (saturated vapor) points. Also, indicate the values of υf and υg on the x-axis of both the p-υ and T-υ diagrams.

Q4. Water inside a closed, rigid tank is cooled from its critical point to a final pressure of 10 MPa. (i) Sketch the process on p-υ and T-υ diagrams. Label the saturated liquid and saturated vapor states. (ii) Find the quality of the water after cooling. (iii) Calculate the heat transfer in kJ/kg.

Q5. Water of mass 1 kg contained in a piston-cylinder configuration is initially in a saturated liquid state (state A) at 10 bar. The water undergoes the following thermodynamic cycle: AB -> The water is heated isobarically until the water is in a saturated vapor state. BC -> The system is then cooled isochorically until the pressure is 1 bar. CD -> The system is further cooled isobarically until υD= υA. DA -> The system is finally heated isochorically back to state A. (i) Sketch this cycle on p-υ and T-υ diagrams (not to scale), using arrows to indicate the direction of each process. (ii) For each of the four states A to D, write down p, T and υ. (iii) For each of the four processes, evaluate the work and heat transfer (in kJ). (iv) What is the thermal efficiency of this power cycle?

Q6 (Bonus). Water of mass 2 kg in a closed, rigid tank is initially in the form of a twophase liquid-vapor mixture. The initial temperature is 50° C. The mixture is heated until the tank contains only saturated vapor at 110° C. (i) Find the initial pressure, in kPa. (ii) Find the work for the process, in kJ. (ii) Find the heat transfer for the process, in kJ.

A layer of cork 6 inch thick is used as layer of thermal insulation in a flat wall. The temperature of the cold side is 40 oF and that of the warm side is 180 oF. The thermal conductivity of the cork at 32 oF is 0.021 Btu/ft-h-oF and that at 200 oF is 0.032. The area of the wall is 25 ft. Estimate the rate of heat transfer through the wall. Answer: 182 Btu/hr

Design a refrigerator working on propane ammonia and R407C refrigerant and producing -20K, -10K and O K temperature during steady state operation....

carryout experimental validation using appropriate software.

write energy and exergy equation in Fortran 77 only...
plot graph in scilab....

Towers for support of the electric lines are made of wood (as-grown or laminated), steel or aluminum (either lattice structures or tubular poles), concrete, and occasionally reinforced plastics. What would you choose, and what constraints would you think must be met to select the best material?

and what formulas should be used to choose the best material?