Week_8_Recitation_1_.rev

# Week_8_Recitation_1_.rev - a thermal reservoir at 1500 K....

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Week 8 Recitation Bullet Items Entropy Change for Idea Gas with constant specific heats: s = c v dT/T + Rln(v 2 /v 1 ) 2245 c v,av ln(T 2 /T 1 ) +Rln(v 2 /v 1 ). s = c p dT/T - Rln(p 2 /p 1 ) 2245 c p,av ln(T 2 /T 1 ) - Rln(p 2 /p 1 ). Isentropic process of Ideal Gases with constant specific heats: pv k = const. Polytropic work Isentropic efficiencies Reversible steady-flow work for CV energy balance and pump work Rankine cycle and ideal Rankine cycle (with and without superheat) Recitation Problem 1. A closed, rigid container is divided into two gas-tight parts (A and B) by a well-insulated, frictionless piston of negligible heat capacity. The container is well insulated except at one end of part A. Each part of the container holds 1kg of an ideal gas with constant specific heats. C v =0.75 kJ/(kg K); C p /C v =1.4; and R=0.300 kJ/(kg K) Initially, T 1A = T 1B = 300 K; p 1A = p 1B = 180 kPa; and V 1A = V 1B = 0.5 m 3 . Heat Q 12 is added internally reversibly through the uninsulated end of the container from
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Unformatted text preview: a thermal reservoir at 1500 K. At the end of the process, V 2A = 3V 2B =0.75 m 3 . Find p 2B (kPa), T 2B (K), and S 2B S 1B (kJ/K). (Note: you should not have to consider the behavior of the gas in part A at all for this calculation.) Find p 2A (kPa), T 2A (K), and S 2A-S 1A (kJ/K). Find Q 12 (kJ). (Hint: use the first law.) What is the change of S (kJ/K) for the universe? A B 2 A B 1 Recitation Problem 2. A simple Rankine cycle operates between a pressure of 40 bar and 0.1 bar. The isentropic efficiencies are 92% for the pump and 88% for the turbine. m = 1000 kg/sec Sketch the corresponding ideal cycle on a T-s diagram. Find W p , W t , Q in , Q out , , and BWR....
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## This note was uploaded on 03/15/2010 for the course ENGRD 221 taught by Professor Staff during the Fall '08 term at Cornell University (Engineering School).

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