What is the WaterSteamPro Custom Units?

Do you have "headache" about converting from units in SI to units in units which you are using at every call to WaterSteamPro functions?

Do you want to tell WaterSteamPro functions to use you own custom dimensions?

Do you want to send parameters in WaterSteamPro functions and receive results in those dimensions what you want?

In this case the program WaterSteamPro Custom Units is designed for you.

The principles of WaterSteamPro Custom Units

WaterSteamPro Custom Units - it's simple extension under WaterSteamPro, consisting of some libraries.

One advantage (and disadvantage, since our disadvantages it's prolongation of our advantages) of WaterSteamPro in this fact that all it's functions receive arguments and return results in SI (Pa, K, N, Joule etc.).

From one hand it's program advantage, since you always know the dimensions, which used in functions.

But from the other hand you must every time made the units conversion from dimenstion you are used into dimensions in SI, the latest used by WaterSteamPro functions.

To solve the latest problem program WaterSteamPro Custom Units is designed.

This program practically identical to WaterSteamPro except follows:

all functions of the WaterSteamPro exist also in WaterSteamPro Custom Units. But they have prefix not "wsp", but "wcu". For example the function to calculate saturation pressure for given saturation temperature named not "wspPST(t)" (such as in WaterSteamPro), but "wcuPST(t)" etc.
WaterSteamPro Custom Units functions (with prefix "wcu") located in library "okawcu6.dll" and princeple of it's work is simple: they convert arguments from custom dimension to dimension in SI, call the "nature" function from WaterSteamPro (with prefix "wsp") and convert return value from SI to custom dimension.
In WaterSteamPro Custom Units added few new functions to change/view settings of units convertins. The description of these functions given below, and full parameters description given in section "Functions list" in documentation.

In WaterSteamPro Custom Units have own system files for using it in programs (Mathcad, Excel and so on), so you can use WaterSteamPro and WaterSteamPro Custom Units together at one PC. But it is recommended to use the same version of the WaterSteamPro and WaterSteamPro Custom Units.

The principles of units converting in WaterSteamPro Custom Units

To converting dimensions used simple linear dependance:

SIunit = A * CU + B,

where SIunit - dimension in SI (used by "nature" functions of the WaterSteamPro), A - factor of proportionality, B - addition, CU - dimension in user units system.

Given formula is used while converting the WaterSteamPro Custom Units functions arguments into SI before call to "nature" WaterSteamPro functions. To backword return values converting used next formula:

CU = (SIunit - B) / A

The samples of A and B:

for MPa: A = 1E6, B = 0;
for kJ/kg: A = 1000, B = 0;
for °C: A = 1.0, B = 273.15

To set up the parameters A and B used the WaterSteamPro Custom Units function:

wcuSETCU(unit_id, A, B)

where unit_id - unit type identificator, A - parameter A for given unit type, B - parameter B for given unit type.

For each type of dimension in WaterSteamPro Custom Units functions used special unique number - unit type identificator.

As example for pressures - unit type identificator equal to 1, for temperatures - 2, for specific volumes - 4 and so on. The full list of unit type identificators given below. In WaterSteamPro Custom Units functions list for each function and it's arguments given used unit type.

For default all user defined dimensions are identical to SI. It's mean that for all units used next values A = 1.0, B = 0.0.

But file with units conversion settings is exists This file allow to set parameters of units conversion by default. This file named "okawcu6.ini" and it's located in folder where WaterSteamPro Custom Units is installed. You can edit this file manually in anyone text editor (as example - Notepad).

When WaterSteamPro Custom Units installed the Setup Wizard suggest to select one of some files "okawcu6.ini", each of them describe own settings of units conversion.

Information about file "okawcu6.ini" used to set up units conversion settings

This file located in installation folder of the WaterSteamPro Custom Units. But each time of initalizing the WaterSteamPro Custom Units this file searched in next folders:

where the main executable file of current application is located.
where located the library "okawcu6.dll".
where WaterSteamPro Custom Units is installed.

The structure of "okawcu6.ini" given in file itself. Also in file given the examples of some units conversion settings.

The list of unit types identificators

Unique unit type identificator	Unit type name	Dimension in SI	Examples of values in this dimension
1	Pressure	Pa	Pressure, saturation pressure
2	Temperature	K	Temperature, saturation temperature
3	Vapor fraction	-	Vapor fraction
4	Specific volume	m3/kg	Specific volume
5	Specific entropy	J/(kg·K)	Specific entropy, specific isobaric and isochoric heat capacities
6	Specific enthalpy	J/kg	Specific enthalpy, internal energy
7	Velocity	m/sec	Sound velocity
8	Joule-Tompson coefficient	K/Pa	Joule-Tompson coefficient
9	Thermal conductivity coefficient	Wt/(m·K)	Thermal conductivity coefficient
10	Dynamic viscosity	Pa·sec	Dynamic viscosity
11	Prandtl number	-	Prandtl number
12	Kinematic viscosity	m2/sec	Kinematic viscosity
13	Isoentropic exponent	-	Isoentropic exponent
14	Surface tension	N/m	Surface tension
15	Efficiency	-	Efficiency
16	Density	kg/m3	Density
17	Molar mass	kg/mole	Molar mass
18	Mass	kg	Mass
19	DPDT	Pa/K	Derivation of saturation pressure on saturation temperature
20	DVDPt	m3/(kg·Pa)	Derivate of specific volume on pressure with constant temperature
21	DUDPt	J/(kg·Pa)	Derivate of specific internal energy on pressure with constant temperature
22	DSDPt	J/(kg·K·Pa)	Derivate of specific entropy on pressure with constant temperature
23	DVDTp	m3/(kg·K)	Derivate of specific volume on temperature with constant pressure
24	DSDTp	J/(kg·K·K)	Derivate of specific entropy on temperature with constant pressure
25	Tolerance	-	Tolerance

Description of WaterSteamPro Custom Units function for working with units conversion

Set up parameters of units conversion for current session of working with WaterSteamPro Custom Units:

wcuSETCU(unit_id, A, B)

where unit_id - unit type identificator, A - parameter A for given unit type, B - parameter B for given unit type.

Receive parameters of units conversion for current session of working with WaterSteamPro Custom Units:

wcuGETCU(unit_id, *A, *B)

where unit_id - unit type identificator, *A - return parameter A for given unit type, *B - return parameter B for given unit type.

Converting of given value from custom dimension to dimension in SI:

wcuCU2SI(unit_id, value)

where unit_id - unit type identificator, value - value to convert.

Converting of given value from dimension in SI to custom dimension:

wcuSI2CU(unit_id, value)

where unit_id - unit type identificator, value - value to convert.

All values of unit_id must be taked from given above table.

Major information about using WaterSteamPro Custom Units

As written above our disadvantages - are prolongation of our advantages.

This is the truph for WaterSteamPro Custom Units too.

When you using the WaterSteamPro functions you can always be sure that functions used the SI units in all cases.

But for WaterSteamPro Custom Units it is not truph. This program convert units depending on user settings (as default - given in file "okawcu6.ini", and as current session given - with the function wcuSETCU(unit_id, A, B)).

And it can be very easy that you think that you use one dimension but in really case program use another dimension.

As example it may occur due to:

You set up (change) file "okawcu6.ini" for your needs, but after reinstall new version of program. And old file are rewritten to new file. And your calculations are depends on settings given in old file. With new file all values are wrong.
You send your document with calculations to another user, and he can have another settings on default. This also can result in wrong values.
You copy document from PC to notebook, where given another default settings.
and so on.

So it is strongly recommended to set up all units conversion settings in each document where you use WaterSteamPro Custom Units functions.

Another type of mistakes - in repeated redefinition of units converting while working with one document (or few documents) at one session.

In can be occur at next cases:

You define first parameters of units conversion at begin of calculation, and after, as example, at middle of calculation redefine it's secondary. Later, you want to recalculate your document. And may be that the program, in which you make calculation, don't process the WaterSteamPro Custom Units functions where you set up the parameters of units conversion. It can be occur due to that the modern programs (such as Excel, Mathcad), try to optimize calculations and don't process formulas that is not changed. It can result that you use wrong values.
You set up units conversion on one document and after loads another document where this settings are defined in another way. And such as in previous way the main program can don't calculate needed formulas where proper units conversion settings applied.
You set up units conversion in one document and make calculation in it. Later you load another document, in which parameters of units conversion are defined in another way. You calculated second document and after return to first document and add a few formulas used units conversion. And in this case these new formulas will use settings applied not in the same document, but units conversion settings applied latest (from second document). And it can result to wrong results.
and so on.

Such errors arise from fact that WaterSteamPro Custom Units can't know about the context in which it's functions are used.

So it's strongly recommended to set up units conversion settings only one time at begin of calculation. And it's recommended to take into account the process of set up of units conversion settints while recalculation. And recalculate all document while working with a few documents. In Excel the recalculation full worksheet can be done by pressing CTRL+ALT+F9.

But I hope that the WaterSteamPro Custom Units help you in your working.

Yours faithfully,
Konstantin Orlov