USE SI UNITS
Problem Statement Normalizing is a heat treatment process used to relieve internal stresses, refine the grain size and improve mechanical properties. Normalizing is done to give steel a uniform and fine-grained structure. Normalizing is often used for ferrous alloys that have been austenitized and then cooled in open air. Normalizing not only produces pearlite, but also bainite and sometimes martensite, which gives harder and stronger steel, but with less ductility than full annealing. The normalizing experiment in Materials Science lab is conducted by preparing a small sample of metal. The metal will be heated inside a small furnace up to a certain temperature and it is expected that upon heating the metal will have a uniform temperature thoughout the body. The hot metal is then cooled until its temperature is back to room temperature again. You will help to establish the normalizing experiment in by designing all necessary requirement, such as the following: - Decide the material type and size. - Decide the heating temperature and the heating time. - Determine the cooling time, i.e. up to room temperature. - Generate the heating and cooling charts, i.e (time vs temperature for each heating and cooling process). For the report, you have to show the assumptions taken, the properties of material, details of calculation, and other necessary engineering aspects.
In: Mechanical Engineering
4. (a) Draw a P-V diagram of a real refrigerator that uses 1 kg
of HFC-134a as the working fluid.
Identify the compressor. condenser. throttle and the evaporator
stages of the cycle and indicate
where heat Qc, is extracted from the cold refrigerator and where.
Qa is released to the
environment. Also indicate where the refrigerant is in liquid. gas.
or a mixed phase.
(b) Show that the COP = Qc(Qh -Qc) can be expressed in terms of
the enthalpies at three points of the
cycle, explaining all steps of the derivation.
In: Mechanical Engineering
4. A Rankine cylce operates between pressures of 2 psia and 1500
psia. If the steam entering the turbine is superheated to
800oF, calculate the efficiency of the cycle. Neglect
pump work. Note: The peak of the superheat phase
of this cycle is outside the range of the text steam tables and is
difficult to locate on the text Mollier chart since it does not
have a 1500 psia constant pressure line. Please use the following
information taken from the Combustion Engineering steam tables. At
1500 psia and 800 oF, the steam would have an h = 1364
Btu/lbm and an s = 1.5073 Btu/lbm oR. You should be able
to find the value of h at 2 psia and an s = 1.5073 Btu/lbm
oR from the text steam tables or the Mollier chart. Then
you can calculate the parameters requested by questions 4 and
5.
State your answer as a percent to one decimal place. Example:
35.2
5. A Rankine cycle operates between pressures of 2 psia and 1500
psia. If the steam entering the turbine is superheated to
800oF, calculate the work produced per pound mass of
steam. Neglect pump work.
State your answer to two decimal places. Example:125.25
I WILL RATE YOU
In: Mechanical Engineering
8. In a Rankine cycle steam enters the turbine at 900 psia and
1000oF and exhausts at 1 psia. What is the thermal
efficiency? Neglect pump work.
State your answer as a percent to one decimal place. Example:
25.2
9. Steam is expanded to 12% moisture at 1 psia in a Rankine
cycle. If the initial pressure is 400 psia, what is the efficiency?
Neglect pump work.
Express your answer as a percent to one decimal place. Example:
32.5
I WILL RATE YOU
In: Mechanical Engineering
An ideal diesel engine uses air as the working fluid and operates
with a thermal efficiency ?th =0.5 with a rate of heat addition
Qin=120 kW. The temperature at the beginning and the end of the
addition heat (combustion) are respectively: T2=900 K and T3=2100
K. Assume constant specific heats (Cp and Cv). The air properties
at a room temperature T1=293.0 K are: Cp=1.005 kJ/kg.K,
Cv=0.718KJ/kg.K, the gas constant of air is R=0.287 kJ/kg.K and the
ratio of specific heats k=1.4. Calculate:
a/ The network Wnet and the rate of the heat rejected Qout in
kW.
b/ The mass flow rate of the air mair.
c/ The cutoff ratio rc.and the compression ratio r.
d/ T4
In: Mechanical Engineering
(c) Draw a schematic graph of resolved shear stress versus shear strain for a single crystal of a pure metal. Clearly label the point of the critical resolved shear stress and the three subsequent stages of dislocation behaviour. Describe these three stages.
(d) Explain why the critical resolved shear stress is much lower than the theoretical strength, based on the force required to break atomic bonds within the structure.
In: Mechanical Engineering
5 example in industrial
-valve in i/c engine
In: Mechanical Engineering
What distinguishes scientific and experiential disciplines?
| a) | Science is based on facts and is always right and cannot be falsifiable |
| b) | Scientific disciplines are more difficult to understand, teach and learn |
| c) | Experiential disciplines do not use the scientific process |
| d) | Experiential disciplines are based on standards and best practices and lack overarching principles, laws or axioms that can be applied to solving a wide variety of problems |
| e) | All of the above |
| f) | a and b only |
| b and d onl |
In: Mechanical Engineering
One end of the straw is blocked by a finger when You pushed the other side of straw under water h_0 (m) and right after that finger is removed from end of straw. You can see the level of water in the straw is rising. Find the depth of water in the straw h(t). Consider the situation as quasi equillibrium state and neglect the surface tension.
In: Mechanical Engineering
# sensors for process nonitoring : cutting process ..
- Briefly explain the process ( first explain it un general and then related with the sensor)
-- I need it typing and clear and at least 2 pages
In: Mechanical Engineering
In Finite Element Analysis (FEA) What is a local stiffness matrix and a global stiffness matrix?
In: Mechanical Engineering
Draw a simple circuit to open and close a double acting hydraulic cylinder.
In: Mechanical Engineering
Q11 a) What is the basis for piston rod design? Explain the significance of area ratio.
b) List 4 of the likely causes for slow or erratic motion of an actuator in a hydraulic equipment.
In: Mechanical Engineering
Mechanical vibration.
Examples of forced damped oscillation with harmonic force.
In: Mechanical Engineering
An oven may be regarded as a cube, each side 1.2m long. The oven stands on thin legs and the heat transfer through each of the six faces is identical. The walls and doors are all made of a stainless steel lining (thermal conductivity 20W/mK) 2mm thick, a layer 75mm thick of insulating material (thermal conductivity 0.25W/mK) and a mild steel outer sheet (thermal conductivity 48.5W/mK) 3mm thick. If the inner wall temperature is 400oC and the outer surface temperature is 100oC calculate the rate of heat loss from the oven. Estimate the heat transfer coefficient between the oven and the surrounding air at 30oC
[8.63kW, 14.3W/m2K]
In: Mechanical Engineering