ChE 354 S14 – Homework Set #1: Due 1/22/14 (HW collected at start of class)

1) A closed oil recovery tank in your operation has a pressurized nitrogen layer on the top with an unknown pressure Pg. This is followed by a 3 m deep layer of oil with an s.g. = 0.88. There is a water layer with s.g. = 1.00 under the oil. A Hg filled manometer that has one leg open to the atmosphere [assume normal 1 atm unless otherwise directed] is attached to the tank at a point in the water layer. From the top of the oil to the water-Hg interface in the manometer is 3.9 m. On the other leg of the manometer (Hg-open air) the Hg is at an elevation 0.3 m higher than the other leg. What is the gauge pressure of the gas, Pg, in kPa? (Sketch the system noting the relevant data as an aid in solving the problem.) [ The s.g. of Hg can be found in the example manometer problem of Ch 2. Learn to use your text as a data source including the appendices in back.]

2) An oil pipeline was constructed to transport oil (s.g.=0.80) for 10 miles over a portion of the Coast Range in California. The path of the pipeline can be considered as straight runs mixed with 10 rises of 200 ft followed by 10 descents of 200 ft over hills. When completed the pipeline was tested with water (s.g. = 1.00) and it flowed in a satisfactory manner at a low flow rate and starting inlet pressure of 150 psig. Then oil was slowly introduced to the inlet end of the pipe. As the oil flowed the pressure at the inlet began to rise and the flow rate fell. Finally, the flow stopped all together as the pump could not provide enough pressure. The outlet of the pipe remained open. There was no problem with the pump at the inlet. You are the engineer asked to investigate this problem. What is a likely explanation?

3) One of the tallest buildings in the world is the Petronas Twin Towers in Kuala Lumpur at 1483 ft. If the pressure at a drinking fountain on the top floor (say 1450 ft) is 15 psig, what is the required pressure in the supply line at street level (assuming no flow)? What is a potential problem? What could you do about it?

4) An open-ended cylinder or can 1 ft long is originally full of air (1 atm assumed) at 70 degF. The can is slowly lowered into 70 degF water, open end down until the bottom of the can is at a depth of 10 feet. Assume the water is at 70 degF, the air in the can remains at 70 degF., and air is an ideal gas (the kind of assumptions you will be asked to make yourself in later problems). How high will the water rise in the can (in feet because of the units given)? [This is a problem to demonstrate not only hydrostatic balances but how easy the ‘difficult’ solutions are in this course. There is an analytical solution if you want to keep up with the messy factors involved. It is straightforward in EXCEL Solver and one can do a manual trial & error solution. I don’t normally use T&E solution problems on exams, except possibly ones that can be solved with one simple, thoughtful iteration.]