MidTerm08 - NAME _ UT EID _ SIGNATURE _ PGE 421K Spring...

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NAME __________________ SIGNATURE ____________ UT EID __________ PGE 421K Spring 2008 Midterm Exam Open notes. A copy of Sandler’s book is allowed. No credit for answers without units or with incorrect or unspecified dimensions. Work all 8 problems. There is a bonus question. Put all your work on the exam paper. Blank pages are included throughout. 1) At an LNG processing terminal, a spherical tank contains 100 metric tons (= 10 5 kg) of liquid methane. The liquid occupies the entire volume of the tank. The tank is fitted with a pressure relief valve. The valve holds the pressure in the tank at an operator-specified value by permitting methane to escape if the tank pressure rises above the specified value. a. How many thermodynamic variables must be set to determine the state of the methane in the tank? b. The initial temperature in the tank is 140 K, and the pressure relief value is set at 3 MPa. What is the volume of the tank? c. The pressure relief valve is set at 3 MPa. How much energy must be added to the tank in order to bring the liquid methane to the bubble point? Your answer must include each of the following: a drawing of an appropriate control volume, a cumulative energy balance for that control volume, and a calculation that uses the cumulative balance. d. Because of faulty insulation on one side of the tank, a constant heat flux of 50 J/s enters the tank. The pressure relief valve is set at 3 MPa. How long until the tank contents are completely vapor phase? Methane thermodynamic properties chart on last page 15 pts
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2) A re-gasification unit at an LNG import terminal has been designed to handle 500 kg/s of methane. The unit consists of a pump, a heat exchanger and a compressor, as shown below. The methane enters the unit at T = 160 K and P = 2 MPa. a. The methane exits the pump at 160K and 12 MPa. At what rate must shaft work be supplied to operate the pump? State the assumptions used in your answer.
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This note was uploaded on 02/13/2012 for the course PGE 421K taught by Professor Bryant during the Spring '11 term at University of Texas at Austin.

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MidTerm08 - NAME _ UT EID _ SIGNATURE _ PGE 421K Spring...

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