Water Compression Systems
Name: Kevin W.
Date: September 2003
To whom it may concern:
I was reading a book on the Internet and the character's ship had water compression systems.
The book also said that water could not actually be compressed. When I asked my chemistry
teachers at school, they said that they did not know much about it. My question here is:
Can water be compressed at all? Why or why not?
All substances, gases, solids, and liquids, including water, are compressible. Some
substances just require more pressure per change in volume to compress than others. The
numerical value of the compressibility depends both on the temperature and on the pressure
too. That is how hard you have to squeeze at one pressure to obtain a certain fractional
decrease in the volume is different than at some other pressure. The same for two different
temperatures. Under most "normal" lab conditions however solids and liquids are usually
considered to be incompressible.
Technically speaking, water can be compressed, but very little even at high pressures. For
practical design purposes, water is considered an incompressible fluid, that is, its density
does not change with pressure. The reason anything is compressible is due to how close the
atoms are packed together. If you think about air, it is highly compressible because there
is considerable spacing between the atoms, so it is relatively easy to force the atoms closer
together. When you have a liquid, the atoms are much closer together and considerable
pressure is required to make them any closer. Solids will compress some as well, but it
takes significant pressure. Temperature also plays a factor in density (and thus
compressibility), just ask your chemistry teacher about the ideal gas law.
I am not sure what your book was using a "water compression system", but hydraulic systems
are used almost everywhere to transmit power across a system. What a hydraulic system does
is put a liquid (usual an oil of some type) under pressure, route that pressurized liquid
through pipes or hoses, and releases the pressure at a place where work needs to be done,
usually through a motor or cylinder that transfers the pressure into work. You might want
to research on hydraulic systems (hydraulic lifts, hydraulic elevators, etc.) to get a better
understanding on how energy can be transferred around in a hydraulic system.
Hope this helps and thanks for using NEWTON.
Christopher Murphy, P.E.
Water is said to be "practically" incompressible. This statement is true for most
considerations at low pressures. But at higher pressures and as temperatures vary, there
will be changes in density which must be taken into account when doing any engineering
calculations. I hope that this is a help.
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