Sound velocity of fluid is important thermodynamic parameter. But viewing from the existing literature

there is a lack of sound velocity data. This paper presents the calculation of sound velocity for the adiabatic two-phase flow of refrigerant through capillary tube based on homogenous equilibrium model. According to the definition of sound velocity and Martin-Hou equation of state the sound velocity is obtained using the finite difference method. The sound velocities of three refrigerants

R22

R134a

R744

have been calculated in this paper. The calculation results have been validated by published experimental data and showed fair agreement with the experimental data with an error band of 4%. According to the calculated two-phase sound velocity data

the sonic curves were drawn in the pressure-enthalpy diagram. The data and curves show that the sound velocity increases with the entropy at the same pressure. From the triple point pressure sound velocity on the isentropic curve increases firstly and then decreases. Sound velocity on the isenthalpic curve decreases monotonically for R134a and R744. But the sound velocity of R22 increases firstly then decreases.