Since the areas under the process curve on a P-V diagram are different, the next figure shows that each process gives a different value for the boundary work.Ĭopyright ©1998 The McGraw-Hill Companies. 1.34 CALCULATE the work done in constant pressure and constant volume processes. Streeter, Victor, L., Fluid Mechanics, 5th Edition, McGraw-Hill, New York, ISBN 07-062191-9. P is the absolute pressure and is always positive. P., Thermodynamics, McGraw-Hill, New York. The boundary work is equal to the area under the process curve plotted on the pressure-volume diagram. Mcgraw Hill as capably as evaluation them wherever you are now. So as we work problems, we will be asking, "What is the pressure-volume relationship for the process?" Remember that this relation is really the force-displacement function. Once the process is determined, the pressure-volume relationship for the process can be obtained and the integral in boundary work equation can be performed. To calculate the boundary work, the process by which the system changed states must be known. The above equation W b is valid for a quasiequilibrium process and gives the maximum work done during expansion and the minimum work input during compression. Skip to main content Accessibility help We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Since the work is process dependent, the differential of boundary work, d W b, is This is what happens when steam, the "gas" in the figure below, contained in a piston-cylinder device expands against the piston and forces the piston to move thus, boundary work is done by the steam on the piston. Boundary work occurs because the mass of the substance contained within the system boundary causes a force, the pressure times the surface area, to act on the boundary surface and make it move. Work is energy expended when a force acts through a displacement.
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