A voltage source and a current source both supply current on an electrical system. So why do we call a voltage source a voltage source? What is the difference between the two?
In: Mechanical Engineering
The energy flux of solar radiation arriving at Earth orbit is 1353 W/m2. The diameter of the sun is 1.39x109 m and the diameter of the Earth is 1.29x107 The distance between the sun and Earth is 1.5x1011 m.
(a) What is the emissive power of the sun as calculated from the parameters given above?
(b) Approximating the sun’s surface as black, what is its temperature (as calculated from the parameters given above)?
(c) At what wavelength is the spectral emissive power of the sun a maximum?
(d) Assuming the Earth’s surface to be black and the sun to be the only source of energy for the earth, estimate the Earth’s surface temperature. Assume that the Earth absorbtivity to solar irradiation is 0.7. The actual average temperature of the Earth is currently ~288 K. Why do you think there are differences between your prediction and the actual average temperature (assume that the given value of absorbtivity is correct)?
In: Mechanical Engineering
Write down the equation for the Stress-Strain relation in a fluid.
In: Mechanical Engineering
Express the shear stress at a wall, using the Newtonian model.
In: Mechanical Engineering
A 2in dia bolt is clamping sheets of the metal which are 8mm thick.the total length of the bolt is 12in. Calculate the length of the total threaded portion as well as threaded portion inside.
In: Mechanical Engineering
Which type of extinguisher can be used on all classes of fire?
A. Water
B. Foam
C. Class D
D. None of the above
In: Mechanical Engineering
Question from Transport Phenomena in Material Processing, D.R. Poirer & G.H. Geiger
#12.10
Describe the conditions under which the following terms are applicable: (1) self diffusion, (2)
tracer diffusion, (3) chemical diffusion, (4) interstitial diffusion, (5) substitutional diffusion,
(6) interdiffusion, and (7) intrinsic diffusion.
In: Mechanical Engineering
A vapor-compression heat pump with a heating capacity of 500 kJ/min is driven by a power cycle with a thermal efficiency of 20%. For the heat pump, Refrigerant 134a is compressed from saturated vapor at -10°C to the condenser pressure of 10 bar. The isentropic compressor efficiency is 80%. Liquid enters the expansion valve at 9.6 bar, 34°C. For the power cycle, 80% of the heat rejected is transferred to the heated space. (a) Determine the power input to the heat pump compressor, in kW (b) Evaluate the ratio of the total rate that heat is delivered to the heated space to the rate of heat input to the power cycle. Round answers to 3 significant digits.
In: Mechanical Engineering
A vapor-compression heat pump with a heating capacity of 500 kJ/min is driven by a power cycle with a thermal efficiency of 20%. For the heat pump, Refrigerant 134a is compressed from saturated vapor at -10°C to the condenser pressure of 10 bar. The isentropic compressor efficiency is 80%. Liquid enters the expansion valve at 9.6 bar, 34°C. For the power cycle, 80% of the heat rejected is transferred to the heated space. (a) Determine the power input to the heat pump compressor, in kW (b) Evaluate the ratio of the total rate that heat is delivered to the heated space to the rate of heat input to the power cycle. Round answers to 3 significant digits.
In: Mechanical Engineering
The majority of metals processing starts with what type of processing technique?
What is the difference between a wrought and a cast product?
Describe the Disamatic casting process. What is the advantage to this method over traditional sand casting?(Materials Engineering)
In: Mechanical Engineering
At the beginning of compression process of an air standard dual cycle operating with a compression ratio of 15.88, the pressure is 95 kPa and the temperature is 300 K. The cutoff ratio for the cycle is 1.15. Determine the thermal efficiency of cycle, if the pressure increases by a factor of 2.15 during the constant volume heat addition process. Use table F2 for variation of specific heats with temperature in the analysis.
In: Mechanical Engineering
The seawater through which a boat sails moves 4 knots towards
the East with respect to the bottom of the sea. The boat moves 15
knots with a direction of 60 degrees north of East with respect to
the seawater.
a) What is the velocity, magnitude and direction, of the boat with
respect to the bottom of the sea.
b) To navigate in a determined time interval and to a given destiny the boat requires a speed of 22 knots in a direction of 45 degrees west of North with respect to the bottom of the sea. What is it's velocity with respect to the water?
In: Mechanical Engineering
Consider a Rankine cycle with an ideal intermediate steam pickup, one of which is open and the other is closed feed water heaters. The steam enters the turbine at 12.5 MPa pressure and 550 degrees Celsius temperature and expands to 10 kPa condenser pressure. The steam separated from the turbine at 0.8 MPa pressure is sent to the closed feed water heater and the steam separated at 0.3 MPa pressure is sent to the open feed water heater. The feed water is heated to the condensing temperature of the steam leaving the turbine in the closed heater. The steam comes out of the closed heater as a saturated liquid, then the pressure is lowered into a valve and sent to the open feed water heater. Show the cycle in a T-s diagram with saturated liquid and saturated vapor curves.
a)
Water flow that must pass through the boiler for the production of 250 MW net power,
b)
Calculate the thermal efficiency of the cycle.
In: Mechanical Engineering
A spring with a spring rate of 75 lb/in has a working deflection of 1 in. It provides a minimum of 150 lb at installation. The spring is formed from 0.25 in diameter unpeened music wire. The coil has squared and ground ends, and it fits in a 2.1 in diameter hole with 0.1 in clearance.
Assuming a 15% clash allowance, find:
a) Safety factor for infinite life in fatigue
b) Shut height
c) Safety factor at shut height
d) Total number of coils
e) Free length
In: Mechanical Engineering
A single-tooth hardened-steel worm has a catalog rating of 2000 W at 600 rev/min when meshed with a 48-tooth cast-iron gear. The axial pitch of the worm is 25 mm, the normal pressure angle is 14.5°, the pitch diameter of the worm is 100 mm, and the face widths of the worm and gear are, respectively, 100 mm and 50 mm. Determine the three components of the load on the worm.
In: Mechanical Engineering