An Empirical Equation to Directly Calculate Parameter B4 of the Martin-Hou Equation of State

The Martin-Hou (MH) equation is a widely used equation of state in chemical engineering, mechanical engineering, and refrigeration technology design. It has pronounced advantages in calculations of liquid volume and enthalpy-entropy of high pressure gases and polar liquids. However, the determination of parameter B-4 of the MH equation by using the conventional method is very time-and computation-consuming, which significantly restricts the application of the MH equation in engineering calculations. This article proposes an empirical equation to conveniently calculate B-4 at different temperatures according to B-4(0.7) (B-4 at reduced temperature 0.7). The accuracy of the MH equation to calculate volume of pure liquids by using the proposed equation was verified by comparing tcalculated data with literature data. The proposed equation can remarkably decrease the time to determine parameter B-4, which would boost the application of the MH equation in engineering calculations.