EGR 334 Thermodynamics Homework: 01

Chap 1: 19A town has a 1-million gallon storage capacity water tower. If the density of water is 62.4 lb/ft3, and local acceleration of gravity is 32.1 ft/s2, what is the force in lbf, the structural base must provide to support the water in the tower?-----------------------------------------------------------------------------------------------------------------------------------------Solution:

Principles: The structural support must support the weight of the water in the tower.

Density: Weight:

therefore:

and

where density of H20, = 62.4 lbm/ft3 volume, V = 1 000 000 gallons of H20 accel of gravity, g = 32.1 ft/s2

then

= 8.316 x106 lbf

So the base must hold over 8 million pounds.

EGR 334 Thermodynamics Homework: 01

Chap 1: 37The figure P1.37 shows a tank within a tank, each containing air. The absolute pressure in tank A is 267.7 kPa. Pressure gage A is located inside tank B and reads 140 kPa. The U-tube manometer connected to tank B contains mercury. Using data on the diagram, determine the absolute pressure inside tank B, in kPa, and the column length L, in cm. The atmospheric pressure surround tank B is 101 kPa. The acceleration of gravity is g = 9.81 m/s2

----------------------------------------------------------------------------------------------------------------------------------------Solution:

Using the pressure gage which gives a gage reading with respect to tank B.

where pA = 267.7 kPa and pgage_A = 140 kPa.

therefore:

Studying the manometer, the height L is related to the difference in pressure across it by

or

= 0.200 m = 20 cm

EGR 334 Thermodynamics Homework: 01

Chap 1: 51Convert the following temperatures from degrees F to degrees C:a) 86 deg. F b) -22 deg. F c) 50 deg F. d) -40 deg F. e) 32 deg F f) -459.67 deg F. Then convert each temperature to K.-------------------------------------------------------------------------------------------------------------------------------------Solution: Temperature Conversion oF= 1.8 oC + 32 oC =( oF - 32)/1.8 K = oC + 273.15

F C Ka 86 30 393.15b -22 -30 243.15c 50 10 283.15d -40 -40 233.15e 32 0 273.15f -459.67 -273.15 0

EGR 334 Thermodynamics Homework: 01

Chap 1: 59Answer the following true or false. Explain.a) A closed system always contains the same matter; there is no transfer of matter across its boundary.b) The volume of a closed system can change.c) One nanosecond equals 109 seconds.d) When a closed system undergoes a process between two specified states, the change in temperature between the end states is independent of details of the process.e) Body organs such as the human heart, whose shapes change as they perform their normal functions can be studied as control volumes.f) This book takes a microscopic approach to thermodynamics.--------------------------------------------------------------------------------------------------------------------------------------Discussion:a) A closed system always contains the same matter; there is no transfer of matter across its boundary.True……--------------------------------------------------------------------------------------------------------------------------b) The volume of a closed system can change.True…..this is because the density of the material in it can change.--------------------------------------------------------------------------------------------------------------------------c) One nanosecond equals 109 seconds.False…..1 ns equals 10-9 s. or 1 s = 109 ns-------------------------------------------------------------------------------------------------------------------------d) When a closed system undergoes a process between two specified states, the change in temperature between the end states is independent of details of the process.True……-------------------------------------------------------------------------------------------------------------------------e) Body organs such as the human heart, whose shapes change as they perform their normal functions can be studied as control volumes.True…..As long as the boundaries are clear and the paths by which material enter and leave the defined region are clearly designated. ------------------------------------------------------------------------------------------------------------------------f) This book takes a microscopic approach to thermodynamics.False……..This book takes a macroscopic view of Thermodynamics.