Classifications

• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B19/00—Machines, plants or systems, using evaporation of a refrigerant but without recovery of the vapour
  • F25B19/005—Machines, plants or systems, using evaporation of a refrigerant but without recovery of the vapour the refrigerant being a liquefied gas
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
  • G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
  • G01K7/04—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples the object to be measured not forming one of the thermoelectric materials
  • G01K7/06—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples the object to be measured not forming one of the thermoelectric materials the thermoelectric materials being arranged one within the other with the junction at one end exposed to the object, e.g. sheathed type
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
  • F25B2400/23—Separators

Definitions

• the present invention is concerned with processes using a cryogenic fluid such as liquid nitrogen as a source of cold.
• a cryogenic fluid such as liquid nitrogen as a source of cold.
• the amount of cold that is provided to the process, via an injection of a cryogen, liquid nitrogen for example, is a critical parameter of the process. If too much cold or too little cold is brought to the process, the product obtained will not meet the specifications initially set.
• an excessive intake of cold causes the separation of the coating product (for example a sauce) which is found at the end of the cycle in the form of a powder while it was sought to adhere it to the surface of the pieces to be coated.
• the finished product does not have the sufficient dose of sauce on the surface, it does not comply with the specifications of the manufacture.
• an insufficient supply of cold causes a build-up of the products to be coated which is obviously not the goal. In this case, the product is lost.
• controlling the amount of cold (or energy) supplied to the user process is a key criterion for the control and success of this type of user process of a cryogen.
• the present invention is therefore also interested in the field of flowmeters for two-phase gas / liquid fluids.
• Measuring the flow rate of a two-phase fluid composed of a liquid and a gas is a difficult operation when trying to measure a mass flow rate. 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 simple and widespread cryogenic method for injecting a given quantity of cold into a process is to inject the cryogen, for example liquid nitrogen, through a calibrated orifice whose flow rate is known precisely under given rate conditions. of diphasic, pressure and temperature of liquid nitrogen. Thus, if the supply of liquid nitrogen remains in the same conditions, a simple rule allows to connect the amount of cold injected injection time. When doubling the injection time, we double the amount of cold injected.
• cryogen for example liquid nitrogen
• the system can of course be corrected by eliminating the gas phase by means of a phase separator upstream of the injection point.
• a system injecting liquid nitrogen without pressure regulation or phase separator can lead to dosing errors greater than 50%. Separating the gas phase by means of a separator and regulating the pressure thus allows a very clear improvement in the accuracy of the assay.
• the limits of a calibrated orifice system with a pressure regulator and a phase separator which certainly provides some improvement but which is insufficient in some cases.
• the liquid nitrogen at the injection point can then sub-cool the fluid.
• an in-line cooler (system installed in series on the liquid nitrogen line connecting the storage at the injection point) may be used or the liquid nitrogen in the storage tank may be subcooled.
• the pressure must therefore drop regularly to sub-cool the fluid in the tank (for example once a day) and then back up to be able to feed the injection point with sufficient and constant pressure.
• liquid nitrogen with well-defined physical conditions at the level of the tank can occur under different conditions at the injection site.
• the piping connecting the tank and the injection point can significantly change the temperature of the nitrogen at startup when it is not yet at its stabilized temperature.
• the mass of cryogenic fluid necessary for the process i.e necessary to obtain a temperature setpoint for the products is calculated;
• the mass of cryogenic liquid (measurement of the mass of cryogenic fluid) is introduced;
• the system calculates a mass of cryogenic fluid to be injected based on a fixed ratio between the mass of liquid nitrogen and the associated energy supply.
• this energy ratio can vary with the temperature of the liquid nitrogen entering the system but also with the parameters of the cooling process of food products.
• the document furthermore specifies that an intermediate reservoir may be used to dose (weigh) the mass of cryogenic fluid supplied to the process.
• This technique is only accurate when the cryogenic fluid is injected into the downstream user process (for example a churn) just after dosing. Indeed, when the liquid nitrogen is stored in a tank, even if it is very well thermally insulated, over time, the fluid loses its cooling properties. So, if the dosage of the fluid is performed too long before its injection, the amount of cold injected will be less than desired.
• the present invention aims to overcome the aforementioned drawbacks and is committed to this end to propose a new solution for accurate measurement of the amount of energy provided by a two-phase cryogen to a user downstream process of this cryogen.
• the gas and liquid phases are separated from the cryogenic fluid before the arrival of the cryogenic fluid in the user downstream process.
• the mass flow rate of the gas phase is measured (a direct mass measurement or a volume measurement corrected by the taking into account of the pressure and the temperature of the gas, which is known to those skilled in the art) is carried out.
• the energy flow rate associated with this gas flow rate is calculated by taking into account the enthalpy variation of the gas between its vaporization temperature and the temperature of the gas leaving the downstream user cooling process (for example of cooling food products) in real time .
• the mass flow rate of the liquid phase is measured (a direct mass measurement or a volume measurement corrected by the taking into account of the density is carried out, which again is known to those skilled in the art).
• the energy flow rate associated with this liquid flow rate is calculated, taking into account the temperature of the liquid and the vaporization energy of the liquid at this temperature. Considering that this liquid will be entirely vaporized, for this vaporized gas, the calculation also takes into account the enthalpy variation of this gas between its vaporization temperature and the gas temperature at the outlet of the downstream cooling process (as for the gas phase mentioned above). -above).
• the two phases are (re) mixed to supply the user downstream process with this mixture.
• the calculations associated with the measurement of the flow of cryogenic liquid take into account the temperature, the pressure and the ratio between the gas phase and the liquid phase liquid nitrogen, the calculations also take into account the temperature of downstream use (eg freezing of food products).
• the system can associate an energy value and a cooling efficiency with a mass of liquid nitrogen.
• the temperature of the cryogen is not taken into account. In many cases, this temperature is constant and this does not affect the accuracy of the measurement.
• the temperature of the cryogen varies, then the amount of energy provided by a given mass of liquid nitrogen under given pressure and temperature conditions also varies. If the temperature of the cryogen decreases the amount of energy available in the liquid nitrogen will be automatically greater.
• the system proposed here takes into account the temperature of the cryogen and this phenomenon. Thus, the measurement of the energy provided remains fair even when the temperature varies.
• the mass flow rate of the gas phase is available (whether by a direct measurement or by a conversion of a volume flow);
• this mass flow rate is converted into energy by using tables and taking into account the enthalpy variation of the gas between its temperature of vaporization and the temperature of the gas output of the real-time user cooling process (the appended FIG. 2 provides an example of a table for calculating the nitrogen gas energy in the case of a downstream process which is a method of freezing).
• the mass flow rate of the liquid phase is available (whether by a direct measurement or by a conversion of a volume flow);
• this mass flow rate is converted into energy by using tables and taking into account the temperature of the liquid and the vaporization energy of the liquid nitrogen at this temperature, as well as the enthalpy variation of the gas resulting from the vaporization of this liquid between its vaporization temperature and the gas temperature at the output of the user downstream cooling process in real time (the appended FIG. 3 provides an example of a table for calculating the energy of liquid nitrogen in the case of a downstream process which is a freezing process).
• the present invention thus relates to a method of assaying the energy supplied to a downstream process using a cryogenic fluid, comprising the following steps:
• the energy flow rate associated with this gas flow rate is calculated by taking into account the enthalpy variation of the gas between its vaporization temperature and the gas temperature read at the output of said downstream process in real time.
• the energy flow rate associated with this liquid flow rate is calculated, taking into account the temperature of the liquid and the vaporization energy of the liquid cryogen at this temperature, and taking into account, for the gas resulting from the vaporization of this liquid, liquid, the enthalpy variation of this gas between its vaporization temperature and the temperature of the gas output of said downstream process in real time.
• the present invention also relates to a flowmeter for two-phase liquid / gas cryogenic fluids, able to measure the energy supplied by the cryogenic fluid passing through the flow meter to supply a downstream process using this cryogenic fluid, comprising:
• phase separator capable of separating the gas and liquid phases from the cryogenic fluid reaching the flowmeter.
• a gas flow sensor capable of measuring the mass flow rate of the separated gas phase.
• a liquid flow sensor capable of measuring the mass flow rate of the separated liquid phase.
• an acquisition and data processing unit capable of: calculating the energy flow rate associated with the gas flow rate measured by the gas flow rate sensor, taking into account the enthalpy variation of the gas between its vaporization temperature and the temperature of the gas; recorded at the output of said downstream process in real time, and

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Separation By Low-Temperature Treatments (AREA)

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• 2014
  • 2014-07-29 FR FR1457345A patent/FR3024540B1/fr active Active
• 2015
  • 2015-07-21 US US15/329,815 patent/US10466088B2/en active Active
  • 2015-07-21 WO PCT/FR2015/052007 patent/WO2016016546A1/fr active Application Filing
  • 2015-07-21 EP EP15753968.5A patent/EP3175206A1/de not_active Withdrawn

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