tpx - Propriedades Termodinamicas de diversas substancias

tpx - Propriedades Termodinamicas de diversas substancias

A numerical test of the accuracy of TPX: the Clapyron Equation

The Clapyron equation states that dP_sat / dT = s_fg / v_fg Since this relationship involves 4 properties and 2 phases, it is a good test of consistency of the calculated properties and the accuracy of the methods used to find saturation states.

Let's consider water: Water Tcrit: Err:511 Tmin:Err:511(choosing T less than this will generate an error)

Temperature300change T and dT in cells B11 and B12 dT0.01and see how the results change calculate properties for saturated liq and vapor at T and T + dT:

compute h_fg = h_g - h_f, etc:

compute dPsat / dT as a finite difference approximation, and compare to the mean of s_fg / v_fg:

Data Table: percent error vs. T

Percent Error in satisfying Clayron Equation vs. T

P e r c e nt Error

Note the scale: the maximum percent error is 0.0006, so the max fractional error is 6.e-6!

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