The intial conditions for an air-standard Otto cycle operating with a compresssion ratio of 8:1 are 14.7 psia and 60degF. At the beginning of the compression stroke, the cylinder volume of 270 in^3 and 9 Btu of heat are added to the gas during the constant-volume heating process. Calculate the thermal efficiency and the mean effective pressure of the cycle.
In: Mechanical Engineering
Mahjong, Inc., has identified the following two mutually exclusive projects:
| Year | Cash Flow (A) | Cash Flow (B) | |||||||||||||||||||||||||||||||
| 0 | –$37,400 | –$37,400 | |||||||||||||||||||||||||||||||
| 1 | 19,750 | 7,300 | |||||||||||||||||||||||||||||||
| 2 | 15,270 | 13,800 | |||||||||||||||||||||||||||||||
| 3 | 12,750 | 20,270 | |||||||||||||||||||||||||||||||
| 4 | 9,750 | 24,270 | |||||||||||||||||||||||||||||||
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In: Mechanical Engineering
The air mass flow rate of a jet engine is 10 kg/s. The stagnation enthalpy at the exit of the turbine is 918 kJ/kg and the excess air is 4.5.
(a) What should be the mass flow rate of fuel injected in the afterburner, such that the stagnation enthalpy at the end of the afterburner is 1700 kJ/kg?
(b) What is the excess air in the afterburner?
(c) What is the maximum temperature in the afterburner?
In: Mechanical Engineering
A tube is placed vertically in a beaker of salt water with a specific gravity of 1.15. The interfacial tension between the air and the water is 32 mN/m and the contact angle is 30 degrees, calculate:
a) Capillary pressure in psi if the tube diameter is 0.0001 cm.
b) Capillary rise of water in tube.
c) If the cap rock thickness is 2ft, do you think this will stop water migration?
d) Radius in inches of the largest pore, if the displacement pressure is 25 kPa.
In: Mechanical Engineering
An epedemic is spreading form human to human. A hospital counts on the start of the epidemic 100 infected patients visiting on one day. One day later the number of patients coming is 300. Calculate the time constant of the spreading of the disease and calculate when the first infected entered the population. We estimate that the epidemic is controllable by a medicine, a single dose. How many doses do we need if the epidemic is spreading for 14 days?
In: Mechanical Engineering
An industrial coal-fired boiler for process steam is equipped with a 10-year-old electrostatic precipitator (ESP). Changes in coal quality have caused stack emissions to be in noncompliance with federal standards for particulate. Two mutually exclusive alternatives have been proposed to rectify this problem (doing nothing is not an option). New Baghouse: Capital investment $1,140,000, Annual operating expenses $73,200. New ESP: Capital Investment $992,500, Annual operating expenses $115,500. The life of both alternatives is 10 years, the effective tax rate is 40% and the after-tax MARR is 9%. Both alternatives qualify as seven-year MACRS (GDS) equipment. Make a recommendation regarding which alternative to select based on after-tax analysis using NPV.
In: Mechanical Engineering
A cross bar of a planer weighing 9 kN is raised and lowered by
means of two square threaded screws
of 40 mm outside diameter and 6 mm pitch. The screw is made of
steel and nut of phosphor bronze
having 42 mm height. A steel collar bearing with 30 mm mean radius
takes the axial thrust. The
coefficient of friction at the threads and at the collar may be
assumed as 0.14 and 0.10 respectively.
Find the force required at a radius of 120 mm of a handwheel to
raise and lower the load. Find also the
shear stress in the nut material and the bearing pressure on the
threads.
In: Mechanical Engineering
Charlie Chaplin’s Modern Times offers a parody of the assembly line grounded in real events. identify two scenes from the movie (you can either describe them briefly or use screen shots) that capture historical realities and one that you believe is an unwarranted exaggeration.
In: Mechanical Engineering
A thin tungsten wire (i.e. a filament) is heated to a given temperature T. In the visible range (i.e. wave length between 0.39µm and 0.77µm), Determine the following for the four cases listed below:
(a) the band fraction of emitted radiation energy
(b) the blackbody radiation energy emitted
The four cases correspond to to following values of T: (i) T=500K (ii) T=1500K (iii)T=2500K (iv) T=3500K
The melting temperature of tungsten is 3698K. Show all calculation details.
In: Mechanical Engineering
Consider a Carnot-cycle heat pump with R-410a as the working fluid. Heat is rejected from the R410a at 35 oC, during which process the R-410a changes from saturated vapor to saturated liquid. The heat is transferred to the R-410a at 0 oC. The specific volume during the isothermal heat addition process at 0 oC changes from 0.00841 m3 /kg to 0.02994 m3 /kg.
a. Show the cycle on P-T, P-v, and T-v diagrams.
b. Find the quality at the beginning and at the end of the isothermal heat addition process at 0 oC.
c. Find the pressure and specific volume at the four points.
d. Find the specific heat and specific work at each process.
e. Find the net specific heat and the net specific work during the cycle.
f. Determine the COP of the cycle using heat and work.
g. Determine the COP of the cycle using temperatures.
In: Mechanical Engineering
A system for the storage of thermal energy is to be designed using an underground tank of water. The tank is buried at a depth of 3 m and is a cube of 1 m on each side. The water in the tank is heated by circulating it through a solar energy collection system. A given heat input to the water may be assumed due to the solar energy flux. Characterize the design problem in terms of the fixed quantities and design variables. please solve and explain
In: Mechanical Engineering
1. Is the strength of a beam under a static load necessarily related its stiffness?
2. Distinguish between primary failure and secondary failure.
In: Mechanical Engineering
NOTE: What would the anwser be if it was a square plate with a circular hole?
The metallic, circular plate of diameter D and thickness t, has a concentric hole of diameter h in its middle, as shown. Metal density is ? = 8000 kg/m3 ; D = 5 cm.
1) When h = 0 (no hole), determine the maximum thickness t [in mm] so that the plate can stay afloat on the surface of water at 20°C.
2) The plate’s thickness is now 1 mm. Show that, in order for the plate to stay afloat on water surface, the hole’s diameter h satisfies a quadratic equation of the form h2 + Ah + B = 0, where A and B are constants. Using S.I. units [m, kg, s] and with h in m, determine the numerical values of A and B.
In: Mechanical Engineering
Water is contained in a closed, rigid, 0.2 m3 tank at an initial pressure of 5 bar and a quality of 50%. Heat transfer occurs until the tank contains only saturated vapor. Determine a)the final mass of vapor in the tank, in kg,b) the final pressure, in bar.
In: Mechanical Engineering
1. _____ lead to distortion surrounding the welded joints.
(a) Residual stresses (b) Cracks (c) Overlap (d) Incomplete fusion
2. Which of the following is NOT an issue in welded joints?
(a) Porosity (b) Cracks (c) Residual Stresses (d) Hot Shots
3. Which of the following is a solid state welding processes?
(a) Brazing (b) Soldering (c) Cold Welding (d) SMAW
4. In which of the following welding processes, filler metals only are melted at temperatures above 450°C?
(a) Brazing (b) Soldering (c) Cold Welding (d) SMAW
5. Which of the following is involved in friction welding process:
(a) Heat (b) Pressure (c) Both of them (d) None of them
6. In resistance welding, the required energy is generated by chemical reactions
(a) True (b) False
In: Mechanical Engineering