question : 1

While cores increase the cost of castings, they also provide a number of distinct advantages. The most significant is the ability to produce complex internal passages. They can also enable the production of difficult external features, such as undercuts, or allow the production of zero draft walls. Cores can reduce or eliminate additional machining, reduce the weight of a casting, and reduce or eliminate the need for multi-piece assembly. Answer the following questions about cores.

1. The cores themselves must be produced, and generally have to be removed from core boxes or molds. What geometric limitations might this impose? How might these limitations be overcome?

2. Cores must be positioned and supported within a mold. Discuss some of the limitations associated with core positioning and orientation. Consider the weight of a core, prevention of core fracture, minimization of core deflection, and possible buoyancy.

3. Because cores are internal to the casting, adequate venting is necessary to eliminate or minimize porosity problems. Discuss possible features to aid in venting.

4. How might core behavior vary with different materials being cast—steel versus aluminum, for example?

5. Discuss several of the reasons cores may be made from a different material than the molding material used in the primary mold.

6. Core removal is another design concern. Discuss how several different core making processes might perform in the area of removal. What are some ways to assist or facilitate core removal?

Evaluate the disadvantages of ceramic over metal when loaded under dynamic
loading.

A 50 cm *50 cm copper slab 6.25 mm thick has uniform temperature of 300°C. Its temperature is suddenly lowered to 36°C. (quenched in water) Take The conductivity k-370 W/mK, the density rho-9100 kg/m³, the specific heat c-0.38 K/kg°C, the convection coefficient h=90 W/m2C.

1- Calculate the surface area, As

a - 0.125 m2
b- 0.5125 m2
c- 0.25 m2
d- 0.5 m2

2. Calculate the volume,

a- 0.0015625 m3
b- 0.003205 m3
c- 0.00078125 m3
d- 0.03587 m3

3. Calculate the characteristic length, Lc

a- 0.0625 m
b- 0.3125 mm
c- 0.00625 m
d- 0.003125 m

4. Calculate the Biot number, Bi

a- 0.00125
b- 0.00074
c- 0.00152
d- 0.000760

5. Calculate the thermal diffusivity, a (alpha)

a- 0.000107 m2/s
b- 0.0000107 m2/s
c- 0.0107 m2/s
d- 0.00107 m2/s

6. Calculate the constant of time, t (tau)

a- 1200.7 s
b- 0.125 s
c- 240.14 s
d- 120.07 s

7. Calculate the time required for the plate to reach the temperature of t1

a- 1560s
b- 312 s
c- 156 s
d- 0.156s

8. Calculate the time required for the plate to reach the temperature of t2

a- 586.275 s
b- 5862.75 s
c- 1172.55 s
d- 0.586 s

9. Calculate the temperature at the surface at time 100s , Ts 2

a- 279 ْ C
b- 210 ْ C
c- 36 ْ C
d- 150.8 ْ C

10. Calculate the total energy transferred from this plate during the first 100s , Q

a- 806.204 kJ
b- 485.841 kJ
c- 1139.874 kJ
d- 1.426 kJ

Drag measurements were taken for a 5 cm diameter sphere in water at 20 °C to predict the drag force of a 1 m diameter balloon rising in air with standard temperature and pressure. Given kinematic viscosity of water (v) = 1.0 X 10^-6 m²/s and kinematic viscosity of air (v) = 1.46 X 10^-5 m²/s.

1. Perform the Buckingham Pi theorem to generate a relationship for F_D as a function of the independent variables. Assume the drag F_D is a function of diameter (d), velocity (V), fluid density (ρ) and kinematic viscosity (v)

2.Determine the sphere velocity if the balloon was rising at 3 m/s

1- water at 100 degree and quality X=0.8 % has mass 0.1 kg find volume =?
2- R-410 at -10 degree and 100kpa find enthalpy h and energy u
3- water at 200kpa , v = 0.08 m^3/kg find pressure p and Quality x
4- water at 200 kpa , T= 270 degree find specific volume
5- water at p= 1200 kpa , V= 0.18m^3/kg find T,u

At a point in a circular duct with inner diameter of 0.200 m, the flow is fully developed and the air flow average velocity is 10.0 m/s with a mean temperature of 20.0° C. At a point exactly 5.00 m downstream, the mean temperature is 30.0° C. It is known that the wall temperature of the duct was held at a constant temperature between these two points. Find this wall temperature.

Charlie is about to submit tender document for Ministry of Defense, at his home, in conjunction of procurement of 10 unit of Engineer Armored Vehicles.

Based on these Integrated Product and Process Design (IPPD) principles, provide Charlie's justification to support your company strategy to capture the contract.

1. Customer Focus.

2. Concurrent Development of Products and Processes.

3. Early and Continuous Life-Cycle Planning.

4. Proactive Identification and Management of Risk.

5. Maximum Flexibility for Optimization and Use of Contractor Approaches.

Develop Fortran code for double stage pulse tube cryocooler to achieve 20 k temperature using online configuration with regenerative matrix heat exchanger...

Develop Fortran code and plot the results in Sicilian for validation

A mass of 0.3 kg of saturated refrigerant-134a is contained in a piston-cylinder device at 240 kPa.
Initially, 70 percent of the mass is in the liquid phase. Now heat is transferred to the refrigerant at
constant pressure until the cylinder contains vapor only.
(a) show the process on a P-v and T-v diagrams with respect to saturation lines. Determine;
(b) the volume occupied by the refrigerant initially,
(c) the work done, and
(d) the total heat transfer.

A steel tank contains water at ? = 1.00 MPa and ℎ = 3100 kJ/kg. Determine the following:

a. State of the water; ie whether the water is compressed water or saturated water or superheated vapour? (Hint: Use Saturated water—Pressure table to compare ℎ at ? = 1.00 MPa)

b. Estimate the temperature of the water. (Hint: Use Saturated water—Pressure table or Superheated water, depending on the state you find in a)

c. Other properties of water in the tank can be determined knowing just ? and ℎ only. What postulate is this known as?

2. A 1 m3 pressure vessel operating at 500 kPa leaks causing steam to escape at that pressure. The leak was detected 30 mins after it started in which time the amount of liquid in the vessel decreased by 0.0015 m3 . The leak is due to a corrosion that causes a circular hole of radius 5 mm on the surface of the tank. Saturation conditions can be assumed to exist in the vessel. (Hint: Use property table to determine properties at 500 kPa)

Determine the following:

a. Mass flow rate of the steam

b. Exit velocity of the steam

c. Kinetic energy per unit mass of the steam

d. Flow energy of the steam per unit mass

Fluid Mechanics - True or False

1) Reynolds number represents the ratio of viscous force to the inertia force.
2) The entrance length (Le) for turbulent flow is greater than that for laminar flow for the same pipe diameter.
3) Increase the fluid viscosity leads to decrease the turbulence.
4) For laminar steady flow between parallel fixed plates, the pressure drop increase with increasing the thickness of the fluid layer between them.
5) For laminar steady flow for pipe, the pressure drop increase with increasing the pipe diameter.
6) For the same Reynolds number, friction factor for steady laminar flow between parallel plates is greater than that for pipe flow.
7) For turbulent flow, the thickness of viscous sublayer is greater than the thickness of inertial sublayer.
8) Darcy -Weisbach equation can be used for calculating the head of losses for both laminar and turbulent flow.
9) Minor losses important only for turbulent flow.
10) Minor losses for entrance flow conditions is less than that for exit flow conditions.

Only state if its False or True for each point.

A diesel cycle operates at and receives 400BTU of energy from the combustion process. The hot air standard is k=1.3. The diesel engine receives air at a pressure of 14.5psia, 90°F, and 0.55lb. What is the mean effective pressure of the engine? The cut-off ratio is 12% of the volume displacement and the percent clearance is 8%.

A rigid sealed tank contains 0.5 kg R-410a at 0^oC with specific volume 0.01m³/kg. The pure substance R-410a is now heated to a room temperature of 25^oC.

a. Find the volume of R-410a in the tank.              [2]

b. Find the final pressure R-410a in the tank          [2]

c. Find the process heat transfer.