Study on the PVT x Properties for Mixtures of Alternative Refrigerants

测量了HFC32 +HFC125、+HFC134a、HFC125 +HFC134a二元混合物在283K ~ 353K范围内、接近饱和压力~约20 MPa范围内的液相PVT性能。本工作采用的方法是一种新型的直接称重技术。将样品容器（约64cm<@D13@>D1）悬浮在电天平（1200(]SY.+- . [)0.001g）上，通过直接称重样品容器的毛重来观察密度。手油泵产生的压力通过毛细管传递给试样。将包括样品容器在内的悬浮机构浸入控制在（]SY.+- . [）0.02K的液体恒温器中。温度是用石英温度计测量的。采用最大压力为5(]SY.+- . [)0.003 MPa和25(]SY.+- . [)0.008 MPa的精密应变片测量压力。样品容器内的体积由在298.15K和0.1MPa下测量的甲醇比容得到。在不同的温度和压力下，对不同密度的纯HFC32、HFC125、HFC134a和HFC152a（纯度大于99.6%）的密度进行了观测，证实了密度计的可靠性，与参考值相比，测量的不确定度在（]SY.+- . [）0.002g/m<@D13@>D1。在（]SY.+- . [）0.0003 mol的不确定度范围内称重制备了混合物，并测量了HFC32/HFC125、HFC32/HFC134a和HFC125/HFC134a的液体二元混合物在不同温度和压力下的密度。用超声测速仪测量了饱和液体密度所需的泡点压力。在这些混合物中，由于HFC32/HFC125体系具有共沸混合物，因此对它们进行了窄间隔浓度的详细测量。这些结果与Fuller状态方程和Peng-Robinson状态方程有一定的相关性。

The PVT properties in the liquid phase for binary mixtures of HFC32 +HFC125, +HFC134a, and HFC125 + HFC134a were measured at from 283K to 353K and from near the saturated pressure to about 20 MPa.The method used in this work was the new direct-weighing technique. The sample vessel (about 64cm<@D13@>D1) was suspended to an electric balance (1200(]SY.+-。[)0.001g), and the densities were observed by direct weighing the gross weight of vessel contained the sample. The pressure generated by a hand oil pump was transmitted to the sample through the capillary tube. The suspension mechanism including the sample vessel was immersed in a liquid thermostat controlled within (]SY.+-。[)0.02K.The temperature was measured by a quartz thermometer. The pressure was measured by two precision strain gauges of maximum pressure : 5(]SY.+-。[)0.003 MPa and 25(]SY.+-。[)0.008 MPa.The volume in the sample vessel was obtained from the specific volume of methanol measured at 298.15K and 0.1MPa. The densities of pure HFC32, HFC125, HFC134a and HFC152a (purity : better than 99.6%) having the different density were observed at several temperatures and pressures, and the reliability of densimeter were confirmed to be measure an uncertainty within (]SY.+-。[)0.002g/m<@D13@>D1 compared with reference values.The mixtures were prepared by weighing with an uncertainty of within (]SY.+-。[)0.0003 mole, and the densities of liquid binary mixtures of HFC32/HFC125, HFC32/HFC134a and HFC125/HFC134a were measured at several temperatures and pressures. The bubble point pressures for these systems required to estimate the saturated liquid density were also measured by the instrument for ultrasonic speed measurement. Among these mixtures, They for HFC32/HFC125 were measured in detail for narrow interval concentrations, because that system has an azeotropic mixture. These results were correlated by the Fuller's equation of state and the Peng-Robinson's equation of state with a reasonable accuracy.