A tank with an internal volume of 1 m3 contains air at 800

Chapter 5, Problem 5177

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A tank with an internal volume of 1 m3 contains air at 800 kPa and 258C. A valve on the tank is opened allowing air to escape and the pressure inside quickly drops to 150 kPa, at which point the valve is closed. Assume there is negligible heat transfer from the tank to the air left in the tank. (a) Using the approximation he < constant 5 he,avg 5 0.5(h1 1 h2), calculate the mass withdrawn during the process. (b) Consider the same process but broken into two parts. That is, consider an intermediate state at P2 5 400 kPa, calculate the mass removed during the process from P1 5 800 kPa to P2 and then the mass removed during the process from P2 to P3 5 150 kPa, using the type of approximation used in part (a), and add the two to get the total mass removed. (c) Calculate the mass removed if the variation of he is accounted for.