Pressure Volume Relationship - Science and Environmental 压力-容积关系的科学和环境.ppt

Pressure Volume Relationship - Science and Environmental 压力-容积关系的科学和环境
Objectives
Explain Boyle's law.
Define pressuPressure Volume Relationship - Science and Environmental 压力-容积关系的科学和环境
Objectives
Explain Boyle's law.
Define pressure in general terms.
Compare atmospheric, hydrostatic pressure, and absolute pressure.
Correctly calculate absolute pressure for any depth of fresh or salt water
Correctly calculate pressure/volume relationships for a gas in a flexible container at any depth of fresh or salt water.
Correctly calculate the volume of gas in a cylinder of known volume, given a change in pressure.
Boyle’s Law:
Volume varies inversely with absolute pressure.
Density varies directly with absolute pressure.
Pressure
Definition
Force per unit area.
Atmospheric Pressure
Force exerted by the air column above us.
psi at sea level = 1 atm.
Hydrostatic Pressure
Force exerted by the water column above us.
Every 33' of sw = 1atm. (increase per foot of depth = .445 psi)
Every 34' of fw = 1 atm. (increase per foot of depth = .432 psi)
Absolute Pressure
Sum of atmospheric and hydrostatic pressure.
Can be expressed as
Atmospheres absolute (ATA)
Psi absolute (PSIA)
Example 1
Calculate the Absolute Pressure, in psia, at 61 feet in the ocean.
Answer:
Hydrostatic Pressure =
.445psi/ft x 61 ft = psi
Atmospheric Pressure =
psi
Absolute Pressure =

Example 2
Calculate the Absolute Pressure at 99' in the ocean in terms of ATA.
Method 1
Use the formula (Depth + 33)/33
Depth = (99+33)/33 = 132/33 = 4ATA
Method 2
Use the formula (Depth/33) + 1 = Depth ATA
Depth ata = (99/33) + 1 = 3atm +1atm = 4ata
Method 3
99 x .445psi = + = = 4ATA
Pressure/Volume Relationship
Formula
P1 x V1 = P2 x V2
P1 = Original Pressure
V1 = Original Volume
P2 = New Pressure
V2 = New Volume
Example 1
A BC has 6 quarts of air at the surface and is submerged
to 49' of fr