Development of Laser-Doppler Vibrating Tube Densimeter with High Accuracy at High Temperatures and Pressures.

We have developed a new vibrating tube densimeter that is capable of measurements of up to 870K and pressures to 70 Mpa。The densimeter features aδ-shaped design to enhance the length of vibration harmonics，laser-doppler detection of of vibration，wide-range piezoelectric input stimulus，real-time display of all vibration modes，and the elimination of all magnets and tube attachments。Vibrational stimulus is applied to a tube filled with the substance of interest over a time step with a piezoelectric actuator.The input stimulus is simultaneously sensed by computer.A helium-neon laser vibrometer is used to detect transient vibrational changes and an FFT analyzer provides all vibration modes。In the calibrations，the 5 I D 1 th i D 1 vibrational mode was used to achieve the greatest sensitivity。A statistical method was applied to develop a calibration@equation that was valid over a wide range of temperatures and pressures.A flow apparatus was constructed to PVT at high-temperature and high-pressure conditions.The system consisted of a syringe pump feed，high temperature oven with preheat，densimeter and syringe pump receiver.The feed pump was run in constant flow mode while the receiver pump was run in constant pressure mode.With this apparatus，densities of water，methanol，or water methanol mixtures were measured at supercritical conditions with an accuracy of 0.006g/cm I D13 I D1，which is fairly larger number than the resolution。The new densimeter along with the laser detection method eliminates magnets and extends the range of current vibration-type densimeters.

We have developed a new vibrating tube densimeter that is capable of measurements of up to 870 K and pressures to 70 Mpa. The densimeter features a δ-shaped design to enhance the length of vibration harmonics, laser-doppler detection of of vibration, wide-range piezoelectric input stimulus, real-time display of all vibration modes, and the elimination of all magnets and tube attachments. Vibrational stimulus is applied to a tube filled with the substance of interest over a time step with a piezoelectric actuator. The input stimulus is simultaneously sensed by computer. A helium-neon laser vibrometer is used to detect transient vibrational changes and an FFT analyzer provides all vibration modes. In the calibrations, the 5ィイD1thィエD1 vibrational mode was used to achieve the greatest sensitivity. A statistical method was applied to develop a calibration equation that was valid over a wide range of temperatures and pressures. A flow apparatus was constructed to PVT at high-temperature and high-pressure conditions. The system consisted of a syringe pump feed, high temperature oven with preheat, densimeter and syringe pump receiver. The feed pump was run in constant flow mode while the receiver pump was run in constant pressure mode.With this apparatus, densities of water, methanol, or water+methanol mixtures were measured at supercritical conditions with an accuracy of 0.006g/cmィイD13ィエD1, which is fairly larger number than the resolution. The new densimeter along with the laser detection method eliminates magnets and extends the range of current vibration-type densimeters.