heat transfer question, show equations, assumptions, calculations and steps clearly. will give thumbs up rating if solved correctly in 30 minutes

Define thermal diffusivity (α) and give its mathematical expression.

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Steam enters an adiabaticnozzle operating at steady state at 20 bar, 320°C, with a velocity of 100 m/s. The exit pressure and temperature are 7 bar and 200°C, respectively. The mass flow rate is 5 kg/s. Neglecting potential energychanges, determine:

a.the exit velocity, in m/s.

b.the exit flow area, in cm2

In the two-tube heat exchanger with the same axis used as engine oil cooler, cold water enters the steel pipe with inner/outer diameter of 25/30 mm (K= 55 W/mK) entering with at 15°C temperature, 0.5 m/s speed and comes out at 25°C temperature. Hot oil enters the steel pipe with inner/outer diameter of 40/46 mm with a speed of 0.25 m/s at 60°C temperature. According to the oil is required to be cooled at 5°C;

A) Find the pipe length for parallel flow?

B) Find the pipe length for reverse flow. Examine the results.

C) Calculate the pressure loss of the oil and the required pump power in reverse flow.

1. What is mesh convergence and how is it achieved in FEA in the absence of a known exact solution?

2. What are the four main sources of error in finite element model in order of least important to most important?

What is the more beneficial in resisting torsion the solid section or the hollow section? State why?

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Abdul-Rahim Taysir

Two plates of thicknesses 25mm and 15mm are clamped together by an M8x1.25 bolt used with a regular nut and with regular washers placed on both the nut and bolt head sides. The top plate is 25mm thick with E=70 GPa and the bottom plate is 15mm thick with E=90 GPa Determine the fraction of external load borne by the bolts. The bolt, nut and washer are made up of steel (E=207 GPa). Note: Round up the bolt length to the nearest 5mm

1. i) The majority of machining operations involve tool shapes that are three dimensions, which refer to orthogonal and oblique cutting. Explain the mechanism of both cutting with an aid of diagram

ii) The accompanying illustration shows a fixture that is to be machined from rectangular blank. Recommend the type of operations, sequence required and specify the machine tools that are needed.

2. As an engineer, propose and describe the most suitable joining process for joining beam for bridge and describe the advantages of the process selection (6marks)

Which energy sector (Residential+Commerical, Transportation, Industrial Sector) has the greatest need for energy conservation and why? Which energy sector is most likely to achieve significant energy conservation and Why?

Answer to the following:

a. Define the flow work from the energy balance for the control volume system.

b. What is the flow work for the case of steady, incompressible flow?

c. Discuss the physical meaning of the equation for the above case b.

d. Discuss the reason why the flow work of a heat pump must be minimized.

e. Discuss which process is the best for a heat pump among the isentropic, polytropic, and isothermal processes in terms of the P-v property diagram

is polyurethane coating considered and organic coating? explain.

Experimentally it has been found that the toughness to fracture, varies with the thickness of the test specimen, under what conditions a minimum value (flat effort or flat deformation) is obtained and why ?.

1. An iron alloy with a carbon content of 0.05% C is heated up to 912oC in an atmosphere that produces 1.20% C on the surface and thus is maintained for 24 hours. Calculate the carbon content at 0.05 cm below the surface if (a) iron is CC and (b) iron is CCC. Explain the difference.

C-Fe bcc (Q= 20.900 cal/mol Do = 0,011 cm2/s ) C-Fefcc (Q= 32.900 cal/mol Do = 0,23 cm2/s ), ferror (0,0685)= 0,077, ferror(0,192) = 0,2139