To start a three-phase motor, three switches (A, B and C) are required in such a way that its operation occurs only under the following conditions: • When closed only B • When closed only C • When A and B are simultaneously closed and C is not closed • When A and C are simultaneously closed and B is not closed

Whats the difference between fracture surfaces of ductile and brittle materials? Whats the effect of axial load verse torsional load on the fracture surface of ductile and brittle materials.

Air within a piston cylinder assembly executes a Carnot refrigeration cycle between hot and cold reservoirs at TH=500 K and TC=300 K, respectively. The magnitude of the heat transfer rejected to the high temperature reservoir is 250 kJ per kg of air. The pressure at the start of the isothermal expansion is 325 kPa. The air can be modeled as an ideal gas with constant specific heat.
For the air as a system, determine
a. (5) the coefficient of performance.
b. (5) the net work input to the cycle in kJ/kg.
c. (10) the Pv and Ts diagrams for the cycle with arrows showing the directions of the processes.

Çapı 50 mm olan sabit kesitli bir borudan 1.5 m/s hızla su akmaktadır. Boru girişindeki etkin basınç 590 kPa’dır. Borunun çıkışı, girişinden 25 m daha yüksekte ve atmosfer basıncındadır.
(ρsu=1000 kg/m3, g=9.81 m/s2)
a) Borunun giriş ve çıkışı arasındaki yük kaybını bulun. b) Boru yatay bir yüzey üzerine yerleştirilirse, akış hızı ile çıkış basıncı aynı kalacak şekilde giriş basıncını hesaplayın.

Water flows at a speed of 1.5 m/s through a fixed section pipe with a diameter of 50 mm. The effective pressure at the pipe Inlet is 590 KPA. The outlet of the pipe is 25 m higher than its entrance and is at atmospheric pressure.
(psu=1000 kg / m3, g=9.81 m / s2)
a) find the load loss between the input and output of the pipe

b) if the pipe is placed on a horizontal surface, calculate the input pressure so that the flow rate and the output pressure remain the same

A vapor-compression refrigeration cycle working with R22 contains a liquid-to-suction heat exchanger. The saturated liquid refrigerant at 40 ℃ leaving the condenser and entering
the heat exchanger is used to superheat the saturated vapor refrigerant leaving the evaporator at 7 ℃ by 8 ℃. If the compressor is capable of pumping 5 1/s of vapor refrigerant measured
at the inlet to the compressor and the compression processes are considered isentropic in both cases listed below, determine;

(a) The refrigerating capacity in kW, the compressor power in kW, and the COP of the system in the absence of the heat exchanger.
(b) The refrigerating capacity in tons refrigeration, the compressor horsepower, and the COP of the system in the presence of the heat exchanger.

Explain fibers and voids in a microstructure?

An actual Rankine Engine turbo-generator receives steam at a pressure of 10MPa and etropy of 6.931 j/kgK, the steam then expands to 500kPa with a temperature of 250°C and leaves the condenser as a saturated liquid at 150°C.

a. find the engine thermal efficiency of the actual engine

b. The actual steam rate for the engine

c. if the mechanical efficiency is 80% and the generator efficiency is 90%. What is the combined work in kW if mass steam flow rate is 5000kg/hr?

Select a solid, rectangular, Eastern hemlock beam for a 5m simple span carrying a superimposed uniform load of 4132 N/m

a. What is N-S equations for incompressible flows in cartesian coordinates in long form (in x,y,z coordinates)?

b. What is continuity equation and N-S equations for incompressible flows in polar coordinates in long form (in r,θ,z)

c. What is N-S equations in x direction for Planar Couette- Pouseille flow and derive an equation for velocity variation using boundary layer conditions

d. Assume an incompressible, steady, axissymmetric, fully developed Pouseille flow in a cylindrical pipe (infinitesimally long in z direction). The flow is in z direction, and radial and tangetial velocity is zero. Derive and simplify the N-S equation in z direction to find out the velocity in z direction. (need to use the boundary conditions to solve for integration constants)

Question 2

2.1       A brass rod of 25 mm in diameter is enclosed in a steel tube. The tube is 10 mm thick with an outside diameter of 50 mm. The bar and the tube are initially 1 m long and are rigidly fastened together at each end. Calculate the stresses in the two materials when the temperature is raised by 80 ⁰C.                               

2.2       If the composite bar is then subjected to an axial tensile load of 60 kN, find the resulting stresses.                                                                                                           

2.3       Calculate the final length of the composite rod. (use brass rod)                     

            E_st = 200 GPa; α_st = 12 x 10^-6 / ⁰C

            E_br = 100 GPa; α_br = 19 x 10^-6 / ⁰C

Case Study In Francisco Automotive Manufacturing Plant, a large number of engineering activities are carried out in a wide range of areas. These activities include design, production of parts, assembly, testing, and quality assurance. Many of the manufacturing processes in the plant are performed using automated technologies and equipment. People also perform some of the manufacturing tasks and the plant employs over 400 workers. The decision on whether people or machines will be used for a particular task is dependent on many factors, including costs, time, quality and worker health and safety. The plant considered here produces a many parts for vehicles and assembles them. Among the parts produced are engine materials and parts, pumps, fans, some exterior parts, and electronics components. The plant normally operates three shifts per day and has production lines including machining equipment, conveyers and overhead cranes, punch presses, and paint-spray booths. The plant utilizes electricity and natural gas extensively. A number of workers at the plant have over the last six months been subject to several different health problems. The following information has been received by the head engineer at the plant. a) In an assembly area that was installed recently, workers have to bend to the ground throughout the day to attach several small parts onto a large and heavy vehicle component. Some workers have begun to develop lower back pain, likely due to the repetitive bending. The problem has become so severe for one of the workers that he has been told by his doctor to stay off work for two weeks so his back can recover. The manufacturing engineers who designed the assembly operation had wanted to use an automated system, but that option was deemed not to be economic. So they used a manual operation, but did not take into account industrial ergonomics, as they had no expertise in that discipline. b) An increased incidence of respiratory illnesses has been reported over the last month by workers operating near the paint-spray booths. Many of the substances used in the booths (paints, solvents, etc.) are known to be causes of the observed respiratory illnesses. But the workers are not supposed to come into contact with any of the substances because the paint-spray booths are designed to ensure that all materials exit the plant through a high capacity ventilation system and that no materials can leak back into the plant. No tests had been carried out on the ventilation system, or on the air quality around the paint spray booths, so it is uncertain whether or not there have been any leaks into the plant from the paint-spray booths. c) In an area of the plant where metal cutting occurs and workers use protective eyewear, workers have reported minor eye injuries. The area in question is one where it is common knowledge that the workers do not routinely use the protective eyewear. It is often observed to be hanging on nearby hooks or to be loosely hanging around the necks of workers. Workers complain that they find the protective eyewear uncomfortable and do not think it is needed or important. The plant manager knows of this behavior but overlooks it, since enforcing the use of the protective eyewear seems may make the workers unhappy and, consequently, less productive. That, he feels, could render the plant non-competitive.

Question:

1) Should the head engineer endeavor to rectify the health problems on her own, or should she report the problems to the plant manager beforehand? The head engineer is not sure if she will receive the support of the plant manager in rectifying the problems; what should she do if support is not provided?

2) Do you feel that some of the health problems that have occurred are due to worker health and safety being unduly compromised to allow the plant to be more productive or profitable

3) Which of the unsafe conditions and acts identified in part b are (1) of a technical nature, or (2) related to human behavior or management

An open forging die used to forge a cylindrical part with the initial diameter is 45 mm and the initial height is 40 mm. The coefficient of friction at the die-work interface is 0.20. The height after forging is 25 mm. The yield strength of the work material is 285 MPa, and its flow curve is defined by a strength coefficient of 600 MPa and a strain-hardening exponent of 0.12. Determine the force in the operation (a) just as the yield point is reached (yield at strain = 0.002), (b) at a height of 35 mm, (c) at a height of 30 mm, and (d) at a height of 25 mm.

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