Work
The working fluid can be used to output useful work if used in a turbine. Also, in thermodynamic cycles energy may be input to the working fluid by means of a compressor. The mathematical formulation for this may be quite simple if we consider a cylinder in which a working fluid resides. A piston is used to input useful work to the fluid. From mechanics, the work done from state 1 to state 2 of the process is given by
Where ds is the incremental distance from one state to the next and F is the force applied. The negative sign is introduced since in this case a decrease in volume is being considered. The situation is shown in the figure which follows.
The force is given by the product of the pressure in the cylinder and its cross sectional area such that
Where A.ds = dV is the elemental change of cylinder volume. If from state 1 to 2 the volume increases then the working fluid actually does work on its surroundings and this is commonly denoted by a negative work. If the volume decreases the work is positive. By the definition given with the above integral the work done is represented by the area under a pressure - volume diagram. If we consider the case where we have a constant pressure process then the work is simply given by
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—Brachiate Guioth De Espinosa, Colombian storekeeper. As quoted in the New York Times, p. A6 (July 15, 1994)
“I suppose I have a really loose interpretation of “work,” because I think that just being alive is so much work at something you don’t always want to do.... The machinery is always going. Even when you sleep.”
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“A work of art is one through which the consciousness of the artist is able to give its emotions to anyone who is prepared to receive them. There is no such thing as bad art.”
—Muriel Rukeyser (1913–1980)