Midterm_II_2002_w_Answers_

Midterm_II_2002_w_Answers_ - MEAM 203 FALL 2002 THERMO -...

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MEAM 203 FALL 2002 THERMO - MIDTERM II Closed books. Answer all three questions. Write clearly! Explain all steps. Answers without clear explanation will be discounted. GOOD LUCK . (30%) 1. In a counter flow heat exchanger air is used to heat up water. Air enters the heat exchanger at 2 kg/s, 125 kPa, and 1000 K and leaves at 100kPa and 400 K. Water enters at 0.5 kg/s, 200kPa, 20C, and it leaves as liquid vapor mixture at 200kPa. (15 %) (A) What is the quality of the exiting steam? ( 5%) (B) What is the rate of change in the air entropy? (10%) (C) What is the total rate of entropy generation? Assume that the air is an ideal gas with temperature-independent specific heat Cp=1kJ/kg-K and R=0.287kJ/kg-K. The properties of the water are given below: Water: T=20C; p=200kPa; u=84kJ/kg; h=84kJ/kg; v=0.001m 3 /kg; s=0.3kJ/kg-K Saturated water at p=200kPa; u v =2530kJ/kg; h v =2707kJ/kg; s v =7.13kJ/kg-K; u l = 505kJ/kg; h l = 505kJ/kg; s l =1.53kJ/kg-K; (30%) 2. An adiabatic tank of volume V is initially evacuated. The tank is connected through a valve to a line that carries an ideal gas at pressure p L and temperature T
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Midterm_II_2002_w_Answers_ - MEAM 203 FALL 2002 THERMO -...

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