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Unformatted text preview: Thermal & Fluids Engineering I. Spring 2006. Homework #2 Solution. WebCT post date: 02/02/2006 217 Calculate the work, in joules, that is done in the quasiequilibrium process from state 1 to state 2 shown in the figure. Approach: The work done is the area under the curve of P versus V . Use geometry to calculate this area. Assumptions: 1. The process is quasiequilibrium. Solution: The work for a quasiequilibrium process is W = PdV ∫ The area under the curve from state 1 to state 2 is represented as W = (100kPa)(21)cm 3 + (50kPa)(32)cm 3 = (150 kPa ⋅ cm 3 ) 1000Pa 1kPa 3 1 100 3 3 m cm 0.15 J W = Answer Thermal & Fluids Engineering I. Spring 2006. Homework #2 Solution. Page 2 225 In the figure below, a piston is resting on a set of stops. The cylinder contains CO 2 initially at –30 ° C and 45 kPa. The mass of the piston is 1.2 kg and its diameter is 0.06 m. Assuming atmospheric pressure is 101 kPa, how much heat must be added to just lift the piston off the stops. Approach: A force balance on the piston can be used to calculate the gas pressure at piston liftoff. The ideal gas law is used to determine the final temperature. As a last step, apply the first law to find heat added. Assumptions: 1. Specific heat is constant. 2. Carbon dioxide behaves like an ideal gas under these conditions. Solution: The piston will just lift off when the pressure inside equals the pressure outside plus the weight of the piston per unit area....
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This note was uploaded on 05/05/2008 for the course MANE 2250 taught by Professor Tascuic during the Spring '06 term at Rensselaer Polytechnic Institute.
 Spring '06
 Tascuic

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