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SpecialProblems25-260

SpecialProblems25-260 - temperature of 25 C The oil is...

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Special Problems for ME 200 - Spring 2011 Problems Due on March 25, 2011 SP25: A rigid tank contains 5 kg of R-134a initially at 20 C and 140 kPa. The refrigerant is now slowly cooled until its pressure drops to 100 kPa. (a) Determine the change in entropy (kJ/kg-K). (b) Is the entropy change positive or negative? (c) Calculate the heat transfer (kJ/kg). (d) Show the process on a T-s diagram. SP26: A solid object of AISI 302 steel at a temperature of 850 C is quenched in mineral oil at a
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Unformatted text preview: temperature of 25 C. The oil is contained in a well-insulated cylindrical tank that has a diameter of 1 m and a height of 1 m. The mass of the solid steel object is 8 kg. The specific heat and density of the oil are 1,950 kJ/kg-K and 890 kg/m 3 , respectively. (a) What is the change in entropy (kJ/K) of steel? (b) Calculate the change in entropy (kJ/K) of mineral oil. (c) What is the total entropy change (kJ/K) for the system comprising of steel and oil?...
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