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 a=√δρ/δρ 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.%流体的音速是流体重要的热力学参数,从现有文献看,制冷剂两相区的音速数据缺乏.采用均相流模型,从马丁-侯状态方程出发,根据绝热音速的定义α=√(e)p/(e)pad,利用有限差分方法得到了常用的制冷剂R22、R134a、R744两相区的等熵绝热音速数据,并用文献中的两相区音速实验结果对其进行了验证,表明两者音速误差在4％以内.根据计算出的两相区音速数据,利用相关软件在lgp-h图里面绘制了等音速线,对两相区音速数据进行了分析讨论.数据显示相同压力下,随着熵值的增大,音速值逐渐变大；自三相点压力至饱和压力等熵线上的音速会出现先增大后减小的现象；等焓线上的音速,R134a、R744单调递减,R22先增大后减小.
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