Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/74—Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
  • G01F15/001—Means for regulating or setting the meter for a predetermined quantity
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
  • G01F15/005—Valves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
  • G01F15/08—Air or gas separators in combination with liquid meters; Liquid separators in combination with gas-meters

Definitions

• the present invention relates to the field of flowmeters for two-phase gas / liquid fluids.
• the flow measurement of a two-phase fluid composed of a liquid and a gas is a difficult operation when trying to measure a mass flow. Indeed, all the sensors measuring a flow are hampered when they are placed in the presence of a diphasic liquid whose density changes at any time. This is particularly valid for the flow measurement of cryogenic fluids such as liquid nitrogen.
• a turbine is installed in the fluid in motion and the speed of rotation of the turbine gives an image of the fluid velocity.
• - Pitot tube flowmeters two tubes are installed in the moving fluid to be measured. One tube is installed perpendicular to the flow and gives the static pressure, the other is installed parallel to the flow and gives the total dynamic pressure. The dynamic pressure difference between these two measurements makes it possible to calculate the flow rate.
• Electromagnetic flowmeters applicable only to fluids with sufficient electrical conductivity, use the principle of electromagnetic induction: An electromagnetic field is applied to the fluid and the electromotive force created (force proportional to the fluid flow) is measured. In the case of flow measurement of cryogenic fluids (non-conductive) such as liquid nitrogen, this principle is not applicable.
• Vortex flowmeters are based on the phenomenon of vortex generation that is observed behind a non-profiled fixed body placed in a moving fluid (Karman effect). Measuring the pressure variations created by these vortices gives the vortex frequency, which is proportional to the velocity of the fluid when the fluid retains constant properties. When the density of the fluid varies, the measurement is distorted.
• Thermal flow meters are based on measuring the temperature increase created by a constant supply of energy.
• a two temperature probe system measures the difference in temperature between the inflow and outflow of the flowmeter. Between these two probes, resistance brings a known amount of energy. When the heat capacity of the fluid in motion is known, the flow rate can be calculated from these measurements.
• this principle is not applicable to liquids biphasic whose thermal behavior (vaporization of the liquid) is totally different from monophasic liquids.
• the flow meter consists of a U or omega tube or curve in which the fluid flows.
• the U is subjected to a lateral oscillation and the measurement of the phase shift of the vibrations between the two branches of the U gives an image of the mass flow.
• its cost is quite high and when it is used at very low temperatures (liquid nitrogen at -196 ° C for example) and with a fluid whose density varies enormously and having a significant portion in the gas phase, there is need to strongly isolate the system (high-performance insulation such as vacuum insulation for example) and despite everything, measurements are distorted when the gas rate exceeds a few percent by weight. It should also be noted that measurement is often made impossible when the fluid velocity is low or zero (in the first half of the measuring range).
• the measurement of the flow rate of a two-phase liquid and in particular the measurement of the flow rate of a cryogenic fluid with an acceptable accuracy is not easy to achieve with the devices currently available on the market.
• devices have the following device:
• the two-phase liquid first goes into a phase separator which separates the liquid phase from the gas phase;
• the gas phase is directed to a volumetric flow meter (turbine type for example) with a temperature compensation;
• the liquid phase is also directed to a volumetric flow meter (turbine type for example);
• the most commonly used method is the increase of the liquid pressure.
• a flow meter will be installed at the outlet of a cryogenic pump (high pressure side).
• the liquid is for example pumped into a tank where it is at equilibrium and it is mounted under pressure by the pump, this almost without increasing temperature.
• the following piping and flowmeter can then create a pressure drop, this will not result in vaporizing the liquid provided that the pressure drop is significantly lower than the pressure increase created by the pump.
• This technique is for example perfectly suited to the flow measurement of nitrogen delivery trucks. It is reliable at an acceptable cost since the cryogenic pump is required for other reasons.
• the present invention seeks to provide a new simple and reliable solution for measuring the flow of two-phase gas / liquid cryogenic fluids, to solve all or part of the technical problems mentioned above.
• the fluid arrives under pressure conditions and temperature known or not.
• the liquid phase may be at equilibrium (boiling limit).
• the fluid may be composed of a liquid phase and a gaseous phase (two-phase liquid) in variable proportion.
• the solution can be applied to any fluid when the latter has a boiling temperature lower than the ambient temperature of the room where the flow meter is installed.
• the proposed scheme includes the following elements:
• this vessel acting as a phase separator, this vessel is advantageously equipped with a liquid phase level sensor, a liquid temperature sensor and a gas phase pressure sensor. It has been understood that it is preferred according to the invention the use of a tank volume where the liquid is quiet to allow the separation of the phases, but can also use a large pipe that will play this role of separator.
• This pipe is equipped with a temperature sensor of the gas flowing in this gas pipe.
• the assembly is preferably thermally insulated.
• the liquid flowing in the liquid flow sensor must not (or almost no) comprise gas.
• Each gas bubble passing through the sensor causes a large measurement error.
• this system proceeds to the following actions: - separation of the two phases of the fluid; the fluid arrives in the tank which is in fact a phase separator.
• the liquid naturally accumulates at the bottom of the tank and the gas in the upper part of the tank.
• Mass flow measurement of gas this measurement is performed in a conventional manner and well known to those skilled in the art, the gaseous phase of the fluid passes through the flow meter present on the gas line, which measures the volume flow rate of the gas.
• This flow meter may for example be of the vortex, ultrasonic, turbine or calibrated orifice type.
• the temperature sensor measures the temperature of the gas
• the pressure sensor measures its pressure.
• the calculator of the system calculates the density of the gas passing through the flowmeter. By thus disposing of the volume flow rate and the density of the gas, the computer then computes in a known manner the mass flow rate of the gas.
• Mass flow measurement of the gas can also be carried out directly by means of a thermal or Coriolis flow meter.
• the liquid is at its liquid / vapor equilibrium point. Any pressure drop as small as it causes the appearance of gas bubbles that significantly disturb the measurement.
• a slight overpressure of the liquid is then created by installing the liquid flow meter (present on the liquid outlet pipe) at a sufficient distance below the tank, preferably between 0.5 and 6 meters below the level of the tank, typically close to 1 meter. In other words, the tank is placed in the "up" position in the space (height "h") relative to the liquid flow sensor.
• the liquid arrives in the flowmeter very slightly undercooled. Between the outlet of the tank and the flowmeter, the temperature of the liquid does not change but its pressure increases. It is then possible to measure the flow rate of the liquid without creating gas bubbles provided that the flow sensor does not cause a pressure drop greater than the overpressure created by the difference in height between the tank and the flow meter.
• the liquid flow meter used may for example be of the vortex, ultrasonic or turbine type. The volume flow thus measured is then corrected by the density of the liquid to obtain the mass flow. This liquid density is calculated by the computer of the system through the temperature of the liquid measured by the temperature sensor which is equipped with the tank as mentioned above. - mixing of the two phases and output of the fluid: The gaseous part and the liquid part which have just passed respectively by a gas flow meter and a liquid flow meter are then mixed at the three-way valve before leaving the device.
• this three-way valve is controlled according to one of the modes that we will explain better below, but the skilled person understands from the foregoing that it represents a kind of "mixer tap” which mix the nitrogen gas and liquid nitrogen that reach him, in proportions that can dictate (and so dictate what comes out of this valve in its third way).
• the 3-way valve is slaved to the level of liquid in the tank via the information given by the liquid level sensor of which the tank is equipped.
• the 3-way valve when the liquid level in the tank is lower than a low setpoint, the 3-way valve is positioned to raise the level: It lets the gas pass and closes the passage of the liquid. Thus, the liquid level will rise in the tank.
• the 3-way valve when the liquid level is between a low setpoint and a high setpoint in the tank, the 3-way valve is positioned to let the liquid and the gas in a quantity more or less equal to 50/50. According to one of the embodiments, it can be envisaged that the valve lets the liquid and the gas pass in different proportions and even depending on the value of the liquid level.
• the three-way valve when the liquid level is higher than a high setpoint in the tank, the three-way valve is positioned to lower the level: It closes the passage of the gas and lets the liquid pass, so the liquid level goes drop in the tank.
• the liquid level in the tank remains between a low setpoint and a high setpoint and the liquid flow sensor only allows liquid without gas bubbles.
• the computer can then either show the total mass flow or the mass flow rates of the gas and liquid phases separately.
• Other display modes can be envisaged for example to show the energy equivalent of the fluid flow or to reveal the mass and volume of gas in the fluid.
• the present invention thus relates to a flow meter for two-phase liquid / gas cryogenic fluids, comprising:
• a liquid / gas phase separator preferably consisting of a tank, in the upper part of which the cryogenic fluid is admitted;
• a liquid flow sensor located on a liquid line in fluid communication with the lower part of the tank, the tank being placed in the upper position in the space relative to the liquid flow sensor;
• a gas pipe in fluid communication with the upper part of the tank, provided with a flow sensor of the gas phase circulating in this gas pipe;
• a three-way valve adapted to recover in two of its tracks on the one hand the downstream end of said gas pipe and on the other hand the downstream end of said liquid pipe.
• a device for measuring the liquid level in the tank preferably comprising two level sensors: a low level sensor and a high level sensor.
• the invention may furthermore adopt one or more of the following features: - A liquid flow meter is used with a pressure drop as low as possible.
• the pressure drop of the liquid flow sensor is less than the liquid charge height between the lower part of the tank and the liquid flow sensor, and preferably less than 2 meters high liquid.
• the liquid flowmeter chosen in the lower part of its measurement range recommended by the manufacturer is used.
• the flowmeter creates a very low pressure drop.
• the pressure drop of the market flow meters is typically close to 10% of its maximum pressure drop (flow divided by 3, load loss divided by 10).
• the liquid flow sensor being marketed for use in a recommended range of flow rates, range delimited by a recommended low flow rate and a recommended high flow rate, the liquid flow circulating in the liquid pipe is always located in a restricted range located between said recommended low flow rate and 30 to 70% of said recommended high flow rate.
• the selected flowmeter is "oversized" by using a flowmeter in its low measuring range: for example, a recommended flowmeter in use in the 300 - 3000 l / h range will be used on its low range. from 300 to 1500 l / h. It could be considered that this arrangement has the disadvantage of reducing the measurement range of the sensor.
• a sensor which initially has a measuring range of 1 to 10 300 to 3000 l / h can only be used with this technique over a range, for example from 1 to 5. This may appear as a factor limiting the use of this technique.
• the liquid flowmeter measures a flow rate higher than the outflow through the 3 rd channel of the 3-way valve (and therefore the outgoing flow of the device ) in that a "storage" of liquid is carried out.
• a "storage” of liquid is carried out.
• some of the fluid flow extracted from the vessel and passing through the liquid flow meter exits the apparatus (via the 3rd channel) while another portion (e.g., in a 50/50 ratio) of the liquid flow extracted from the tank and passing through the liquid flow meter is authorized by the controller and the three-way valve to go up in the gas line (pipe normally used to lower the gas to the 3-way valve). The liquid then accumulates in this gas line.
• the automation (controller) of the system positions the 3-way valve so as to block the passage of the liquid, the flow then progressively passes from 300 to 0 l / h.
• Phase 2 (which can be described as “destocking”: blockage of the flow in the liquid flowmeter and “destocking” of the liquid accumulated in the gas line):
• the 3-way valve blocks the passage of the liquid and leaves passing the gas
• the liquid stored in the gas pipe is then discharged through the outlet of the device (3 rd channel).
• the device When there is no more liquid, the device then delivers gas and the level of liquid in the tank rises. When this level goes above a threshold high), the automatism then opens the valve on the gas side and on the liquid side (for example 50/50) and then returns to Phase 1.
• the apparatus can measure flow rates in a very wide range, practically from 150 to 15001 / h in our example is a range of 1 to 10 as originally intended.
• one or more pressure and temperature sensors are available, capable of measuring the pressure, in particular in the gas phase of the vessel, and of measuring the temperature in the liquid phase of the vessel and, if appropriate, in the gas phase of the vessel; the tank and / or in the gas phase exiting through said gas line.
• a separator 1 of liquid / gas phases constituted here of a tank, in the upper part of which is admitted the two-phase cryogenic fluid;
• a gas pipe 4 in fluid communication with the upper part of the tank, provided with a flow sensor 5 of the gas phase circulating in this gas pipe;
• a three-way valve 6 adapted to recover in two of its tracks (A, B) on the one hand the downstream end of said gas pipe and on the other hand the downstream end of said liquid pipe;
• a device 7 for measuring the level of liquid in the tank preferably comprising two level sensors: a low level sensor and a high level sensor;
• the tank is also equipped here with a pressure sensor 8 in the gas phase located in the upper position of the tank but we will not detail here the various pressure and temperature sensors that may be present on the installation, being able to measure the pressure in particular in the gas phase of the tank and to measure the temperature in the liquid phase of the tank and, where appropriate, in the gas phase of the tank and / or in the gas phase leaving via said gas line, for reasons well known to those skilled in the art.
• FIG. 2 then makes it possible to better visualize the operation of the three-way valve.
• the arrival “G” designates the arrival of the gas channel
• the arrival “L” designates the arrival of the liquid channel
• the channel “S” designates the exit of the valve.
• FIG. 2 i the case where the system orders the closure of the liquid channel and the opening of the gas channel is illustrated.
• FIG. 2 j illustrates the case where the system orders the opening of the liquid channel and the opening of the gas channel, for example in proportions 50-50.
• Figure 2 (k) illustrates the case where the system orders the closing of the gas channel and the opening of the liquid channel.
• valve 6 is slaved to the level of liquid in the tank via the information given by the level sensor 7.
• valve 6 when the liquid level is lower than a low level set point, the valve 6 is positioned by the controller to raise the level in the tank: It lets the gas pass and closes the passage of the liquid . Thus, the liquid level will rise in the tank.
• the valve 6 When the liquid level is between a low level setpoint and a high level setpoint (FIG. 4), the valve 6 is positioned to let the liquid and the gas in an amount, for example, substantially equal. In some cases, it can be envisaged that the valve allows the liquid and the gas to pass in different proportions and even depending on the value of the liquid level.
• valve 6 When the liquid level is higher than a high setpoint ( Figure 5), the valve 6 is positioned to lower the level: it closes the passage gas and let the liquid pass, which will lower the level of liquid in the tank 1.
• FIG. 6 then illustrates the operation of the device in Phase 1 explained above in the present description: this phase 1 is also called the "storage phase" of the liquid.
• the sensor 3 measures a flow rate higher than the flow rate coming out of the device. Indeed a part of this flow goes up in the pipe 4 (planned to lower the gas towards the valve 6) and accumulates there, until the levels in the tank and in the pipe 4 come closer, the difference pressure then decreases and the flow rate slows down.
• the automation of the system detects this situation (value measured by the valve 6 below a minimum flow) and then positions the valve to block the passage of the liquid ( Figure 7), to "destock" the stored liquid in the pipe 4, the valve delivers then by its 3 e exit way of the liquid, then of the gas (when all the liquid is destocked), the level of liquid in the tank rises, until this level returns between the high and low instructions, the controller will then reopen the valve on both sides (for example 50% gas side and 50% liquid side) etc. and we return to phase 1.

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• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• General Physics & Mathematics (AREA)
• Measuring Volume Flow (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)

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• 2013
  • 2013-11-21 FR FR1361472A patent/FR3013446B1/fr active Active
• 2014
  • 2014-11-13 CA CA2927878A patent/CA2927878A1/fr not_active Abandoned
  • 2014-11-13 EP EP14821698.9A patent/EP3071937A1/de not_active Withdrawn
  • 2014-11-13 AU AU2014351681A patent/AU2014351681B2/en not_active Ceased
  • 2014-11-13 US US15/038,408 patent/US10197425B2/en not_active Expired - Fee Related
  • 2014-11-13 WO PCT/FR2014/052893 patent/WO2015075351A1/fr active Application Filing
• 2019
  • 2019-01-04 US US16/240,246 patent/US10655997B2/en active Active

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