TERMODINÂMICA PROBLEMA, Exercícios de Termodinâmica

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5.15 A piston/cylinder arrangement contains 1 kg of water, shown in Fig. P5.16. The pistomn is spring loaded and initially rests on some stops. À pressure of 300 kPa will just float the piston and, at a volume of 1.5 mi, a pressure of 500 kPa will balance the piston. The initial state of the water is 100 kPa with a volume of 0.5 m?. Heat is now added until a pressure of 400 kPa is reached. a. Find the initial temperature and the final volume. b. Find the work and heat transfer in the process and plot the P-V diagram. A? Cv:H,O Fa 1 Cont:m,=m,=1kg 300 À 2 Energy: m(u, -u,))=,0,-,W, Straight line (linear spring): 100 + 1 | Ee From (0.5, 300) to (1.5. 500) os Lo Ls v The initial pressure can not lift the piston. 1: 100 kPa, vy=Vyim, =0.5 mig < ve => T,=-89.6€ xy = (0.5 - 0.001043)/1.69296 = 0.2947 0, =417.33+ 0.2947 x 2088.72 = 1032.9 kJ'kg 2: 400 kPa and on line, see figure => V,= 1.0 m? = V4=Vyim,=10 mjkg Superheated vapor Table B.1.2: T,=595ºC. u,=3292 k]kg 1W5= Í PdV= AREA = =(300 + 400)(L.0 - 0.5) = 175 kJ 195 = m(u,- 07) + (Wo = 1(3292 - 1032.0) — 175 = 2434 kJ