In: Mechanical Engineering
In the Injection Moulding Process, thicker parts are more susceptible to shrinkage. Explain why this is the case.
In: Mechanical Engineering
This is problem 5-5 from El-Wakil’s Powerplant Technology book -- steam expands ideally in a turbine from 2500 psia and 1000 degFahrenheit to 1 psia. Compare the maximum steam velocities and the number of stages required by (a) a velocity-compounded impulse turbine, (b) a pressure-compounded impulse turbine, and (c) a 50 percent reaction turbine if the optimum blade velocity may not exceed 885 ft/s in any of them. Take all nozzle angles to be 25°.
In: Mechanical Engineering
A CAT D&H (power-shift) dozer is used to push material that weights 87 pcf in the bank state. It is estimated that the material will swell 5% from a bank state. The material is in a loose stock pile and is to be moved an average distance of 250 ft on a 2% downhill grade. The operator is average. Job efficiency is estimated to be at a 50-min hour. Assume that the dozer will have an 0.39 coefficient of traction. The O&O cost for the dozer is $86 per hour and the operator's wage is $17.50 per hour plus 44% for fringes, insurance and worker's compensation. Calculate the production in bcy per hour. (Reference Table 7.2 and Figure 7.13)
TABLE 7.2 Caterpillar job condition correction factors for
estimating dozer production
Track-type tractor Wheel-type tractor
Operator
Excellent 1.00 1.00
Average 0.75 0.60
Poor 0.60 0.50
Material
Loose stockpile 1.20 1.20
Hard to cut; frozen
with tilt cylinder 0.80 0.75
without tilt cylinder 0.70 —
cable-controlled blade 0.60 —
Hard to drift; “dead” (dry, noncohesive 0.80 0.80
material) or very sticky material
Rock, ripped or blasted 0.60–0.80 —
Slot dozing 1.20 1.20
Side-by-side dozing 1.15–1.25 1.15–1.25
Visibility
Dust, rain, snow, fog, or darkness 0.80 0.70
Job efficiency
50 min/hr 0.83 0.83
40 min/hr 0.67 0.67
Direct-drive transmission
(0.1-min fixed time) 0.80 —
Bulldozer*
Adjust based on SAE capacity relative
to the base blade used in the estimated
dozing production graphs
Grades—see the graph
In: Mechanical Engineering
Using the given lead-tin phase diagram for an alloy content of 80 wt % Sn and a temperature of 100 C (a) what is the primary phase (b) what are the mass fractions of eutectic and primary phases? Show tie line used and all calculations. Use standard lead-tin phase diagram.
In: Mechanical Engineering
Instead of the control-volume formulation, such as the Reynolds transport theorem (Eqs. 11.5 and 11.6 of WMD), please consult fluid mechanics textbooks such as “Viscous Fluid Flow” by F.M. White (Chapter 1 & 2) and derive the Navior-Stokes equation for a Newtonian fluid flow starting from Newton’s second law: F= ma where F, m, a are the force, mass, and acceleration respectively, following a fluid element. In the derivation you should state (or argue) clearly the assumptions you made and the following key terms:
(1) How the stress and strain rate tensors are defined on a fluid element and their relationship.
(2) the definition of a “Newtonian” fluid,
(3) the definition of the coefficient of viscosity and the coefficient of bulk
viscosity (the second coefficient of viscosity)
(4) the relation between the thermodynamic pressure and the mean flow
pressure
In: Mechanical Engineering
A shell and tube type of heat exchanger with one shell pass and two tube passes will be designed to provide the given heat transfer rate Q(kW) to cool hot water by using cold river water . The hot water flows through the shell and the cold water flows through the tubes. The inlet and outlet temperatures of the hot water and the cold water are given as Thi, The and Tci, Tce in degrees Celcius. Design the shell and tube heat exchanger by making necessary assumptions to calculate the dimensions of the heat exchanger. Q= 10 KW Hot Fluid( Water) Thi= 70 Celcius The= 40 Celcius Cold Fluid ( Water) Tci= 5 Celcius Tce= 15 Celcius 1) Assume the tube diameter and tube length . 2) Assume fouling coefficient based on inside and outside tubes, hdi and hdo . 3) Select the material of construction for the tubes to determine the thermal coefficient. 4) Find the Log Mean Temperature Difference (LMTD) . 5) Obtain the Correction Factor F. 6) Calculate the Mean Temperature Difference. 7) Assume the Overall Heat Transfer Coefficient “U” as initial guess according to type of heat exchanger. 8) Calculate the provisional area. 9) Calculate the number of tubes based on the assumed tube diameter, thickness of the pipe and tube length L. 10) Calculate the tube pitch and bundle diameter. 11) Obtain the bundle diameter clearence. 12) Select the minimum Shell thickness according to nominal shell diameter. 13) Calculate the shell inside diameter 14) Calculate the baffle spacing. 15) Calculate the area for cross flow for the hypothetical row of tubes at the shell equator ( at the shell diameter plane). 16) Calculate the shell side mass flow velocity. 17) Calculate the shell side equivalent diameter ( hydraulic diameter) 18) Calculate the shell side Reynolds number. 19) Calculate or obtain the Prandtl number. 20) Calculate the shell side heat transfer coefficient. 21) Read the friction factor from Jf tablet for the calculated Shell side Reynolds number in order to calculate the shell side pressure drop. 22) Calculate the number of tubes per pass. 23) Calculate the tube-side mass velocity. 24) Calculate the tube-side velocity. 25) Calculate the Prandtl and Reynolds numbers for fluids inside the tubes. 26) Calculate the heat transfer coefficient hi. 27) Calculate the overall heat transfer coefficient “U”. 28) Compare the calculated “U” with that assumed in step 7). If the difference is large , start iteration by changing the tube length till the difference is small enough. 29) Calculate the tube-side pressure drop.
In: Mechanical Engineering
I want an example of the kinetics of rocket with FBD which calculate the curvilinear motion and rectilinear motion
In: Mechanical Engineering
Saturated water vapor at 300F enters a compressor operating at steady state with a mass flow rate of 5 lb/s and is compressed adiabatically to 750 psi.
Determine:
a) The percent isentropic compressor efficiency.
b) The rate of entropy production, in hp/R.
In: Mechanical Engineering
You are the test engineer responsible for the final production testing of an automobile (VW Golf R 2018) - create a list of tests with specifications as well as a block diagram depicting your test plan and the order in which you plan to test the car.
In: Mechanical Engineering
In regards to the Injection Moulding Process. Explain why thicker parts can be more susceptible to shrinkage ,suggest two methods to reduce the shrinkage for a given component geometry?
In: Mechanical Engineering
Why does shrinkage occur in the injection moulding process?
You can use diagrams to assist with your answers if you like.
In: Mechanical Engineering
Explain how the processing parameters for INJECTION MOULDING can influence the tensile strength for a given polymer, explain this in terms of polymer properties.
In: Mechanical Engineering
In regards to the Injection Moulding Process, discuss which polymer properties influence the MFI (melt flow index) and how the individual polymers MFI is related to the various processing parameters for injection moulding. You can use diagrams to assist with your answers if you like.
In: Mechanical Engineering
Identify the key steps in the injection moulding process, explaining how and why temperature, time and pressure are important in each step.
In: Mechanical Engineering