Remarks about the function set ("non-physical" functions)

There are some functions in WaterSteamPro, named "non-physical", which calculate properties of water and steam but have no physical meaning. For example, function wspCPSTX(t, x), calculates specific isobaric heat capacity (Cp) in double-phase area depending on temperature t and dryness factor x. In reality, that equals to infinity in double-phase area. However, the function returns the value defined from:

Cp_sw(t)·(1 - x) + Cp_ss(t)·x,

where Cp_sw(t) - is the function of specific isobaric heat capacity of water at saturation line; Cp_ss(t) - is the function of specific isobaric heat capacity of steam at saturation line.

All similar functions are marked by sign in list of WaterSteamPro functions. All these functions are defined when it is necessary to make optimization or find a root and therefore to calculate a value of a property. That may occurs automatically, for example, when Newton method is used. The second example: such up-to-date mathematical packages as Mathcad have built-in functions that find roots, minimums, maximums and so on. At that, if a function has a discontinuity the root may be not found even if it is situated in the tolerance range.

To solve this problem, for universality, the additional functions were defined in WaterSteamPro that return "non-real (physical)" values.

For the same purpose, WaterSteamPro has the ability to disable checking arguments for tolerance range. By default, when calling a function the argument range is checked before calculation. If an argument is out of range the error is occurred with code 2 (WSP_OUT_OF_RANGE).

To disable checking arguments function wspSETCHECKRANGEMODE(mode) is defined. Calling this function with argument equals to zero (0) disable checking the arguments for tolerance range which defined by the region of allowable parameters of the input equations. That allows calculating beyond the original regions with the values of the properties, which are not corresponding with real.

Warning!

From the WaterSteamPro 6.5, all "non-physical" functions when checking arguments mode is on (by default) are generated error with code 2 (WSP_OUT_OF_RANGE).

All functions, based on "non-physical" functions, at specified arguments sets can also generate the same error.

As example, function wspCPSTX(t, x) generate the error at any arguments sets (when checking arguments is on - see below). And function wspCPPH(p, h), which is internally can call wspCPSTX(t, x) - can generate the error only when parameters set (pressure p and specific enthalpy h) is correspondent to double-phase area.

So, by default "non-physical" functions will not work (only return error value "-1.0").

To "turn on" "non-physical" functions you need to disable the checking arguments mode. It can be done by preliminary call to function wspSETCHECKRANGEMODE(mode) with parameter mode = 0.