Mechanical Engineering 300 – Engineering Thermodynamics I

Sections 1 and 3 Spring Semester 2008

Homework 1

Due Friday January 25, 2008

Solve the following problems from S. R. Turns, "Thermodynamics: Concepts and Applications."

1.17, 1.32, 1.33, 1.39, and 1.42

Additional Problems

1. A large fraction of the thermal energy generated in the engine of a car is rejected to the air by the radiator through the circulating water. Should the radiator be analyzed as a closed system or as an open system? Explain. (C&B) Modify the system so that the system is closed, i. e., a "cooling system."

2. What fraction of a typical atom is empty space? (A typical atom has a radius of » 1.5 Å. A typical nucleus has a radius of 5 x 10-12 cm.)

3. Determine the mass and weight of the air contained in a room whose dimensions are 6 n x 6 m x 8 m. Assume the density of air is 1.16 kg/m3. (C&B)

4. Consider a system whose temperature is 18 ° C. Express this temperature in R, K, and ° F. (C&B)

5. Blood pressure is usually measured by wrapping a closed air-filled jacket equipped with a pressure gage around the upper arm of the person at the level of the heart Using a mercury manometer and a stethoscope, the systolic pressure (the maximum pressure when the heart is pumping) and the diastolic pressure (the minimum pressure when the heart is resting) are measured in mm Hg. The systolic and diastolic pressures of a healthy person are about 120 mm Hg and 80 mm Hg, respectively, and are indicated 120/80. Express both of these gage pressures in kPa, psi, and meter water column. (C&B)

6. A mercury manometer ( r = 13,600 kg/m3) is connected to an air duct to measure the pressure inside. The difference in the manometer levels is 15 mm, and the atmospheric pressure is 100 kPa. (a) Judging from the Fig. P1-62, determine if the pressure in the duct is above or below atmospheric pressure. (b) Determine the absolute pressure in the duct. (C&B)

"(C&A)" indicates a problem taken from Y. A. çengel and M. A. Boles, "Thermodynamics – An Engineering Approach," fifth edition.