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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Famous quotes containing the word work:
“Whatever your hand finds to do, do with your might; for there is no work or thought or knowledge or wisdom in Sheol, to which you are going.”
—Bible: Hebrew, Ecclesiastes 9:10.
“I don’t pity any man who does hard work worth doing. I admire him. I pity the creature who does not work, at whichever end of the social scale he may regard himself as being.”
—Theodore Roosevelt (1858–1919)
“There was a deserted log camp here, apparently used the previous winter, with its “hovel” or barn for cattle.... It was a simple and strong fort erected against the cold, and suggested what valiant trencher work had been done there.”
—Henry David Thoreau (1817–1862)