Hi RP
Water is perhaps best studied substance, and chances are
that program you mentioned, a very sensible and useful one, was already
written. It, and the supporting data may not be available on line for free,
but data are available in printed form in any university library, e.g. in the
(famous) data compendium:
. "Landolt-Börnstein:
Numerical Data And Functional Relationships In Science And Technology,
It may be on line as well.
Below, I will give you a bunch of references to look through.
There is a whole:
"The International Association for the Properties of Water and Steam "
which is organising conferences and publishing
" Guideline on the Use of Fundamental Physical Constants
and Basic Constants of Water "
http://www.iapws.org/relguide/fundam.pdf
which will give you basic constants, checked and doublechecked, with references,
such as:
--------------------------------------------------------------------
For water's critical temperature, pressure, and density [14].
These values
(Tc = 647.096 K, p.c = 22.064 MPa, Dc = 322 kg/m 3 )
should be uniformly used.
The triple-point temperature of ordinary water is used to define the
base SI unit of
temperature, the kelvin, and is 273.16 K.
For the triple-point pressure, we recommend the
value measured by Guildner et al. [15], which is (611.657 ± 0.010) Pa
-----------------------------------------------------------------------------------
With these constants, some general 'equations of state' , such as
Van der Walls and it's generalisation already provide an aproximation.
But you may need more accurate and verified approaches.
The two references you found, on Clausius-Clapeyron eq. do apply, but it is
general thermodynamics, meaning:
While R=N*k - the gas constant is a universal constant,
Enthalpy H is a function specific to each material.
You still need values of this function in your p,T range
for your material (water) to reach your goal.
Here is bunch of references from search terms :
codata data water
phase transition, coexistence,
Maxwell rule
numerical pressure temperature phase diagram water
.....
to sort out and perhaps extract useful data for your quest.
The searches based on the above, lead to collections, such as
http://ublib.buffalo.edu/libraries/units/sel/engineering/prop.html
or
http://www.indiana.edu/~cheminfo/10-06.html
or
http://search.lsu.edu/query.html?qp=url%3Awww.lib.lsu.edu%2Fsci%2Fchem&qt=water
which list both printed and on-line sources of data.
Here, to complicate things a bit, is a review of many phases which
water can exists in
http://www.lsbu.ac.uk/water/phase.html
with some references, and important note on supercritical (unstable) forms.
This should get you started.
happy researching
hedgie |
Request for Answer Clarification by
rpavlick3-ga
on
12 Nov 2003 02:57 PST
I am somewhat dissatisfied with the answer you provided. While, the
information may be useful to me, it doesn't answer the question I have
asked.
Obviously, I can go to the library and research the properties of
water. I don't need an online answering service to tell me that. You
say I need the values for enthalpy H within the range of my problem
and the value of the gas constant. Well, there you go, that would have
solved half the question.
The other half of the question was *what* is the *equation* for the
melting curve? Not, where can I find it.
I apologize for my very direct attitude, but I really don't think 30
dollars is too little money to answer a question with:
p(t) = such and such for vaporization
p(t) = such and such for melting
these are variable definitions
i found this data here
Also, I don't really care about the nine phases of ice, the critical
point of water, or supercritical fluids. I am dealing with rather low
pressures and and temperatures near the triple point.
|
Clarification of Answer by
hedgie-ga
on
12 Nov 2003 05:04 PST
Hi again rpavlick
It is perfectly OK to be direct.
If you look at my other answers, you will
see that once I pick up a question I stick with it and provide
customer with as much information as needed to provide satisfactory
answer.
Some questions can be answered in one installment, some do require
clarifications. Your question was well and clearly formulated but I have
guessed wrong how much work you want to do yourself.
Since your question shows search and programing skills and that this
is a project rather then a passing interest, I have provided you with
pointers to information, rather then with specific data. I assumed
that you would enjoy clicking around a bit to see how much and what
kind of data is available.
I guess I was wrong in my guess and will now correct it by providing more
specific data and explanation. But first an explanations (which you may skip)
related to my first and unsatisfactory attempt: Because of the copyright
restrictions, we (researchers) cannot post complete sections (e.g.
tables) from printed books. Many more data exist in printed from, and
paid databases then on free web. So it was an information, assurance
that these data are in LB (as well as elsewhere) and you can get them
for free, even if I cannot post them. It may be obvious, but I do not
know what you know, until you tell me, right? I still do not know if
you are comfortable with calculus etc. I assumed you know what Gas
Constantis since the two web-pages you mentioned are fairly
technical. I will correct that mistake also.
1) Van der Waals equation of state (includes definition of R)
This is the most important chapter of thermodynamics needed here.
Actually, this and critical constants for water which I gave you
contain the answer to your question. Van der Waals equation describes
all three phases, solid, gas and liquid, all that with only three
constants (e.g. critical constants). For many applications this is
sufficient information about the phase transitions.
Please look at this paper first, it also explains how obtain melt-water
boundary. Tell me if it is too technical. There is more then you need but
parts are very pertinent to your question.
http://www.physto.se/~lipniack/statistical_physics/lecture6/lecture6.pdf.
p 12 explains coexistence of phases,
that is BOTH water-gas AND liquid-solid curves (boundary curves).
Here is intro to Thermodynamics which defines R on page 4
and Van Der Waals eq. on page 6.
Here is a paper entitled
"Computational derivation of coexistence curves for van-der-Waals-type
equations"
which describes in detail how to obtain the phase boundary curves.
http://www.iop.org/EJ/abstract/0143-0807/9/1/010/
Derivation uses Maxwell Rule, which is illustrated here:
http://www.inform.umd.edu/EdRes/Topic/Chemistry/ChemConference/ChemConf97/Paper8mirror/Kubasov.html
2) Data for water
While Van der Waals is the first and simplest approximation, many
applications need more precision. I do not know what your application
may require and in which form you want your data. The excellent and
comprehensive site I gave you for water contains much more then info
on ice-10. Here is a quote:
" There are many formulations giving the vapor pressure of ice and
water over various temperature ranges, mostly involving many empirical
parameters.
However, the following approximate formulae are
curious and give approximately straight-line Log-Log plots of integral
gradients 12, 8 and 4 with only physically meaningful parameters..."
http://www.lsbu.ac.uk/water/strange.html#vp
H(p,T) function is one way to describe the data, not necessarily
most suitable for your purpose, but I found those data for you.
3) Computer program and values of H
Clicking around that excellent site a bit, did lead me to the
following site:
http://penmelts.ess.washington.edu/index.html
Select
Mineral Calculator
Phase Water (on the left sidebar)
enter T and p
and computer will give you value of Enthalpy H (and other data)
Program and data can be downloaded for free
http://penmelts.ess.washington.edu/unixmelts_index.html
4) If you are happy with the answer, please do rate it . It helps me
to improve my skills if I know how well,or how badly, I did answer.
If you are not happy, please do ask for clarification.
hedgie
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