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Unformatted text preview: trol volume) 21 Example 11
– Is this classroom an open or closed system? – What about an aircraft engine? 22 Properties
– Property: – Independent properties: A 1 m3 container is fully filled with water. Since the
water density is 1000 kg/m3, the total mass of the water
is 1000 kg. Among the volume, density, and mass, how
many of them are independent properties? 23 Properties
– Extensive properties: – Intensive properties:
m
V
T
p
ρ m 1/2 m
1/2 V 1/2 V
T
T
p
p
ρ
ρ
1/2 24 State and Equilibrium
– State: The “conditions” of system as described by
its properties
For example, in this classroom, air temperature T, air
density ρ, and relative humidity φ characterize the state. 25 State and Equilibrium
Equilibrium:
A state of balance with no unbalanced forces
in the system. (Uniform p, T, C, etc.)
– e.g. mechanical: forces (pressure)
thermal: temperature
phase: vaporliquid
chemical: combustion 26 Units
– Basic quantities Physical quantity SI English mass kg lbm length m ft time s s temperature K R amount of matter mol lbmol electric current A A amount of light cd candles
27 Units
– Derived quantities Force (Newton’s law of motion)
SI force unit English force unit 28 Unit Conversion
(See Equation Sheet) 29 2. Specific Volume, Pressure,
Temperature, Engineering Design
and Analysis, and Methodology  Specific Volume 30 Pressure
– Pressure: p = normal force / area 31 Pressure
For a column of fluid
Freebody diagram
p1A p1
∆z ∆z mg p2
p2
A 32 Pressure
– Atmospheric pressure vacuum patm fluid ∆z 33 Pressure
– System pressure
patm
fluid
∆z gas
psys psys 34 Pressure
Example 21
Given: patm = 14.7 psia, g = 32.2 ft/s2, h = 100 ft,
ρ = 62.4 lbm/ft3
– –
–
– Find: ppump
Assumptions:
Basic equations: vacuum
100 ft 35 Pressure
Absolute, gage and vacuum pressure
pabs
pgage
Atmospheric pressure
– patm pvac
Zero pressure 36 Pressur...
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 Spring '08
 GAL

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