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| A New Three Parameters Vapor Pressure Equation with High-precision Fitting and Accurate Extrapolation Ability for the Entire Region |
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Abstract The saturated vapor pressure equation characterizes the pressure-temperature relationship along the entire gas-liquid coexistence curve, spanning from the triple point to the critical point. And it is a carrier for the practical application of fluid saturated vapor pressure as a fundamental thermophysical property. Based on an in-depth analysis of the thermodynamic principles governing saturated vapor pressure, essential mathematical conditions for an ideal saturated vapor pressure equation are identified and summarized. Utilizing these conditions, a new saturated vapor pressure equation with only three parameters is proposed, which is simple and convenient for application. After analyzing the experimental data of saturated vapor pressure from the triple point to the critical point of 62 substances, it is proved that the fitting accuracy of the new equation to the experimental data is equivalent to that of Wagner equation, and the average absolute relative deviation from the experimental data is less than 1%, and the maximum absolute relative deviation is less than 5%. In terms of extrapolation performance, in the absence of experimental data using simple initial value setting and no parameter constraint fitting, the new equation significantly outperforms the Wagner equation in all extrapolation scenarios: towards the triple point, towards the critical point, and simultaneously towards both extremes, which proves that the new equation holds a more stable extrapolation trend and performance.
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Received: 28 October 2024
Published: 03 April 2025
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| Fund:Science and technology project of Yunnan Southwest United Graduate School |
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2025, Vol. 46 
