ES 202 Fluid and Thermal Systems Lecture 5: Buoyancy & ES 201 Review (12/10/2002)

Assignments Reading: –Cengel & Turner Section 11-1 –ES 201 notes Homework: –10-28, 10-32, 5-62E, 5-75 in Cengel & Turner –For Problem 10-28, “10 cm” should be changed to “9.5 cm” in the figure for consistency –Look up steady state devices (nozzle, diffuser, turbine, compressor, heat exchanger)

Road Map of Lecture 5 Announcements Buoyancy –Cargo problem as introduction –Archimedes’ principle –Examples Review of ES 201 concepts –Fundamentals of control volume analysis common form of conservation equation –steady state device: nozzle, diffuser, turbine, compressor, heat exchanger function design assumption operation assumption

Announcements Feedback on problem session Advice on data analysis, interpretation For Section 5 only: –Lab write-up due tomorrow by 5 pm at my office

Quiz on Lecture 4 Name at least two ways to find the resultant hydrostatic force on a submerged surface. The center of pressure is always above/below the centroid of a submerged surface. Explain your answer. Compare the hydrostatic forces acted on Surface AB in the following configurations: A B A B A B

Cargo Problem as Introduction Work on the problem Give me a physical reason for the cause of the buoyancy force

Archimede’s Principle The buoyancy force acting on a body immersed in a fluid:  is equal to the weight of the fluid displaced by the body (magnitude);  and it acts upward through the centroid of the displaced volume (direction).

More Example Problems

Conservation and Accounting Principles Common structure of accounting equation: storage = in – out + production The above equation can be expressed in –rate form –finite time form Major difference between the accounting of various extensive properties –means of transport (can be classified as “in” term) –production

Production (Physics) The simple book-keeping form does not contain any physics. It is true in general, even in balancing your check book. The “physics” part comes in through the prescription of the production term. What is the production for the followings: –mass –energy –momentum –entropy