Reference no: EM13706657
In thermodynamics, how do you know if pressure is constant, volume is constant, PV is constant or PV^n is constant when going through a problem. I know that a rigid vessel means constant volume, any other tricks I can use to distinguish between each because while reading a problem I just have no clue. Also any advice on how to go about solving problems? This class is literally making me go crazy!
An example problem would be something like:
An air pistol contains compressed air in a small cylinder, shown in Fig. P5.134. Assume that the volume is 1 cm3, pressure is 1 MPa, and the temperature is 27°C when armed. A bullet, m = 15 g, acts as a piston initially held by a pin (trigger); when released, the air expands in an isothermal process (T = constant). If the air pressure is 0.1 MPa in the cylinder as the bullet leaves the gun, find
a. The final volume and the mass of air.
b. The work done by the air and work done on the atmosphere.
c. The work to the bullet and the bullet exit velocity.
Another example problem would be like:
A piston/cylinder has 0.5 kg air at 2000 kPa, 1000 K as shown. The cylinder has stops so Vmin = 0.03 m3. The air now cools to 400 K by heat transfer to the ambient. Find the final volume and pressure of the air (does it hit the stops?) and the work and heat transfer in the process.
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The mass of piston on top of the tank
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Determine the maximum length of a cylindrical walnut
: It is known that a long log floats with its axis horizontal. A very short log, however, floats with its axis vertical. Determine the maximum length of a cylindrical walnut log 30 cm in diameter that will cause it to float with its axis vertical.
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Calculate the conduction heat loss for the following wall
: Calculate the conduction heat loss for the following wall: 15ft long, 8ft tall. Calculate for 8 hr, inside temperature at 78F and the outside temperature at 3F. Wall components from outside to inside are brick; 1.2cm(1/2 in.) plywood; wood studs, 5x1..
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Height difference between two columns of mercury manometer
: A vertical frictionless piston-cylinder device contains nitrogen at 125 kPa. The outside atmospheric pressure is 100kPa. The piston diameter is 25 cm. The height difference between the two columns of mercury manometer (in cm), connected to the side o..
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Find the final volume and the mass of air
: An air pistol contains compressed air in a small cylinder, shown in Fig. P5.134. Assume that the volume is 1 cm3, pressure is 1 MPa, and the temperature is 27°C when armed. A bullet, m = 15 g, acts as a piston initially held by a pin (trigger); when ..
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Determine the total deformation of the specimen
: The specimen shown has been cut from a 1/4 in.-thick sheet of vinyl ( E = 0.45 X 106 psi) and is subjected to a 350-lb tensile load. Determine ( a) the total deformation of the specimen, (h) the deformation of its central portion BC.
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Find the wnet-efficiency-back work ratio-rate of heat input
: An Ideal reheats Rankine cycle. From 1 to 2 we go through Turbine 1. Then 2 to 3 we reheat in a steam generator. Then 3 to 4 we go through Turbine 2. Then from 4 to 5 we go through a Condenser. From 5 to 6 we go through a pump.
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Contains a two-phase liquid-vapor mixture of refrigerant
: A Closed, Rigid tank contains a two-phase liquid-vapor mixture of Refrigerant 22 initially at -20oC with a quality of 50.36%. Energy Transfer by heat into the tank occurs until the refrigerant is at a final pressure of 6 bars. Determine the final tem..
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What is the rate of heat loss per meter of pipe
: A pipe with OD 6.03cm, ID 4.93cm carries steam at 250deg C with h = 200 W/m^2.K The pipe is covered with 2.5cm of magnesia (85%) insulation followed by 2.5cm of polystyrene (k = .025 W/m.K The outer surface is exposed to air at T = 20 deg C with h = ..
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