COMSATS – LANCASTER
(Dual Degree Program)
EEE-112 Engineering Mechanics and Thermodynamics
Assignment # 1
Submission date: Mon, Sep 17, 2012
1. A certain fluid at 10 bar is contained in a cylinder behind a piston, the initial volume being 0.05 m3. Calculate the work done by the fluid when it expands reversibly: a. at constant pressure to a final volume of 0.2 m3;
b. according to a linear law to a final volume of 0.2 m3 and a final pressure of 2 bar; c. according to a law Pv = constant to a final volume of 0.1 m3; d. according to a law Pv3 = constant to a final volume of 0.06 m3; e. according to a law, P = (A/v2) – (B/v), to a final volume of 0.1 m3 and a final pressure of 1 bar, where A and B are constants. f. Sketch all processes on a Pv diagram.
2. 1 kg of a fluid expands reversibly according to a linear law from 4.2 bar to 1.4 bar; the initial and final volumes are 0.004 m3 and 0.02 m3. The fluid is then cooled reversibly at constant pressure, and finally compressed reversibly according to a law Pv = constant back to the initial conditions of 4.2 bar and 0.004 m3. Calculate the work done in each process and the net work of the cycle. Sketch the cycle on a Pv diagram.
3. A fluid at 0.7 bar occupying 0.09 m3 is compressed reversibly to a pressure of 3.5 bar according to a law Pvn = constant. The fluid is then heated reversibly at constant volume until the pressure is 4 bar; the specific volume is then 0.5 m3/kg. A reversible expansion according to a law Pv2 = constant restores the fluid to its initial state. Sketch the cycle on a Pv diagram and calculate: g. the mass of the fluid present;
h. the value of n in the first process;
i. the net work of the cycle.
4. A fluid is heated reversibly at a constant pressure of 1.05 bar until it has a specific volume of 0.1 m3/kg. It is then compressed reversibly according to a law Pv = constant to a pressure of 4.2 bar, then allowed to...
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