TD homework - ME 2124 Introduction to Thermal-Fluid...

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ME2024 – Spring 2009 1 Thermodynamics Problems (TD) ME 2124 Introduction to Thermal-Fluid Engineering Homework Problems Thermodynamics (TD) Spring 2009 1. An archaeologist has found a hieroglyphic inscription describing how a team of 4,000 Egyptians could move a 20-ton granite block a distance of 1.5 cubits per minute. Assum- ing the Egyptians worked 12-hour days, with no days off, what was the progress of the block in furlongs per fortnight? Some useful 1 fortnight = 2 weeks 1 week = 7 days 1 hour = 60 minutes conversions: 1 furlong = 40 rods 1 rod = 5.50 yards 1yard = 3 feet 1 cubit = distance from elbow to extended middle finger (~18 inches) 2. A brewery produces 2 brews per hour, each brew consisting of 390 barrels of beer. As- suming that the retail price of the beer is $4.99 for six 12-ounce cans and that the brewery operates 24 hours per day, what is the retail value of a day's production, in yen? Some useful 1 dollar = 109.6 yen 1 barrel (beer) = 31 gallons conversions: 1 gallon = 8 pints 1 pint = 16 ounces 3. Consider the process of heating water on top of an electric range. a) The water is heated to 150 ° F. Define a system that could be used and measure- ments that could be made to determine the energy transfer to the water. Is the system open or closed? b) The water is heated to 150 ° F. Define a system that could be used and measure- ments that could be made to determine the energy transfer to the surroundings. Is the system open or closed? c) The water is heated until it is boiling vigorously. Are the systems defined in (a) and (b) open or closed? How would the determination of energy transfers be more difficult for this case? 4. For each of the systems described below the system boundary is shown by a dashed line. Determine whether each system is closed, open with fixed control surface, or open with moving control surface a) Garden hose nozzle with water flowing b) Bubble flowing though garden hose nozzle c) Diesel engine cylinder during compression (valves closed)
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ME2024 – Spring 2009 2 Thermodynamics Problems (TD) d) Diesel engine cylinder during exhaust (exhaust valve open) 5. Consider two temperatures, T 1 = 30 ° C and T 2 = 55 ° C. a) Determine the difference between these temperatures, Δ T , in ° C. Convert each temperature to K. Determine Δ T in K. When calculating temperature differences, does it matter whether we use a relative scale ( ° C) or an absolute scale (K)? What can you say about the magnitude of a ° C and a K? b) Determine the ratio T 2 / T 1 using temperatures in ° C. Convert each temperature to K. Determine the ratio T 2 / T 1 using temperature in K. When dividing or multiply- ing temperatures, does it matter whether we use a relative scale (C) or an absolute scale (K)?
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This note was uploaded on 04/10/2009 for the course ME 2124 taught by Professor Uzgoren during the Spring '08 term at Virginia Tech.

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TD homework - ME 2124 Introduction to Thermal-Fluid...

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