FR2801381A1 - DEVICE FOR REFRIGERATING CELLS CONTAINING LIQUID SAMPLES IN PARTICULAR SAMPLES OF PETROLEUM PRODUCTS TO BE ANALYZED - Google Patents

Abstract

Device characterized in that it comprises on the one hand a Stirling cycle or pulsed gas cooling unit (10) constituted by compression module (16) cooperating with a cold finger (17), connected to a current source alternative and equipped with means capable of periodically varying the pressure of a high pressure working gas, in particular helium filling a working chamber subdivided into several compartments and extending in the compression module (16) and in the cold finger (17) so as to cause in a cold compartment located at the end of the cold finger (17) opposite the compression module (16) or first end (18) an expansion of the working gas making it possible to obtain very low temperatures at this level, and on the other hand dry contact heat transfer members (11) mounted on the cold finger (17) at the first end (18) thereof and cooperating with the cell containing the sample to be analyzed so as to allow this sample to cool to the desired temperature.

Description

The present invention relates to a device for

  refrigeration of cells containing liquid samples

  more or less viscous, in particular samples of

  petroleum products to be analyzed in temperature ranges

  res which can range from approximately + 50 to - 120 C. Certain physicochemical tests relating to the field of petroleum product analysis require cooling of the analysis cells and of the samples contained therein to temperatures of up to - 80 C or even - 120 C in certain special cases; among these tests, there may be mentioned by way of nonlimiting example the determination of the limit filterability temperature, of the thawing point, of the pour point, of the

  trouble or the flash point Tag and Abel.

  For this purpose, a device is conventionally used.

  tif of the type shown in Figure 1 schematically cons-

  titrated by a Rankine type cryostat 1 equipped with a reserve of cold coolant and cooperating with a circulation circuit 2 of this fluid according to the arrows a, this circuit

  with a circulation pump 3.

  The circulation circuit 2 is equipped. of a ser-

  pinion 4 surrounding cell 5 to be cooled.

  The assembly constituted by the coil 4 and the cell to be

  cool 5 is placed in an isothermal envelope 6 containing a thermal insulator 7. A temperature probe 8 makes it possible to

  check the cell temperature at all times 5.

  This conventional device in which the cell, containing the sample, is cooled by contact with the coil in which the heat transfer fluid circulates

a number of drawbacks.

  It should be noted in particular that the cooling

  ment of a cell at a temperature of - 80 C requires the use of a heat transfer liquid at a temperature

  about - 85 C to - 90 C, which requires the use of a cryogenic

  double stage Rankine type generator; however, such cryo-

  generators are bulky, noisy and fragile devices

the.

  In addition, to cool the cell, it is necessary

  be able to have a reserve of a cold heat transfer liquid remaining fluid at very low temperature; for this purpose, methanol is currently used essentially since the other available liquids whose implementation could also be envisaged are either very expensive or very volatile at room temperature. However, because of its toxicity,

  it is likely that the use of methanol in labs

  racks will be banned in the short term.

  Furthermore, due to their relative fragility, the cryo-generators of Rankine type are not integrated into the analyzers, which requires thermally insulated connecting lines with the latter; these lines of

  connection are a source of risk of leaks and thermal losses

  ques important, and therefore the overall performance of this

  type of cold source is very weak.

  It should also be noted that the control of the time

  cell temperature is delicate due to the disproportion

  tion of the available energy and the necessary energy, as well as the thermal shocks imposed on the cell at each

injection of heat transfer fluid.

  The object of the present invention is to provide a

  device allowing refrigeration at very low temperatures

  ture of cells containing liquid samples, in

  particularly samples of petroleum products to be analyzed

  be likely to remedy these drawbacks.

  To this end, it relates to a device characterized

  laughed at in that it comprises on the one hand a cooling unit

  Stirling cycle or pulsed gas and on the other hand dry contact heat transfer devices fitted

  on this cooling unit and cooperating with it

  lule containing the sample to be analyzed so as to allow

  to cool this sample to the desired temperature.

  Stirling cycle cooling units

  or pulsed gas which have been designed especially for the re-

  very low temperature cooling of electro-

  picnics are schematically constituted by a compression module cooperating with a cold finger, connected to an alternating current source and equipped with means capable of periodically varying the pressure of a working gas at high pressure, in particular helium filling a working chamber subdivided into several compartments extending in the compression module and in the cold finger; it is thus possible to provoke in a cold compartment located at the end of the cold finger opposite the compression module

  or first end, an expansion of the working gas allows

  both to get very low temperatures at this level.

  According to the invention, the dry contact heat transfer members are mounted on the cold finger, at the

  level of the first end of it.

  The configuration of these heat transfer devices varies depending on the test to be carried out.

artwork.

  According to a variant of the invention adapted as

  example for determining the wire limit temperature

  traceability of petroleum products in accordance with eu-

  ropéen pr EN 116, the heat transmission elements consist of a metallic tubular sheath, in particular of copper, surrounding the cell containing the sample to

  analyze and fitted on its side wall with a realistic sleeve

  dried in the same material whose shape and dimensions

  correspond to those of the first end of the cold finger

  and coming to style this first end.

  According to this variant, the tubular sheath

  as well as the first end of the cold finger wearing the man-

  metal plugs are mounted on the inside of an enclosure

  insulated cover containing thermal insulation.

  The configuration of the heat transmission members can of course be totally different depending on the test to be performed and therefore the type of cells.

to cool.

  In all cases, the heat transmission members are equipped with a temperature sensor cooperating with regulating members allowing fine adjustment.

cell temperature.

  More specifically, a cooling unit

  Stirling cycle generally involves a mo-

  essentially cylindrical compression element as well as a cold, essentially cylindrical finger located in the extension of the compression module coaxially to this

  module but having a smaller diameter.

  The compression module contains at least one main piston controlled by a linear or rotary motor powered by the alternating current source and moving

  back and forth to compress the working gas in a com-

  compression part. The cold finger, for its part, contains a hollow sweeping piston filled with an elastically mounted heat exchanger, moving at the same frequency as the main piston but in phase opposition and cooperating with the latter to periodically vary the pressure of the

  working gas in the different compartments of the chamber

  working hours; this sweeping piston subdivides the cold finger at its internal part into two compartments communicating with each other through the heat exchanger, namely on the one hand the cold compartment located at the first end of the cold finger and on the other hand a compartment located at the opposite end of this finger and connected to the compression compartment. Such a cooling unit known in

  itself whose configuration is for example disclosed

  ford in documents US-A-4,894,996 and US-A-5,088,288 will not be for the purpose of brevity described in more detail in

part of this talk.

  Taking into account the vibrations generated by the

  periodic placement of the main piston and the piston

  layeur, the refrigeration device according to the invention

  must cooperate with damping bodies

  ment of these vibrations when equipped with such a unit

cooling.

  To this end, and according to another characteristic of the invention, the cooling unit is fixed, by means of support legs mounted integrally on its side wall to a ballast plate, in particular made of steel of suitable mass, essentially parallel to its longitudinal axis and

  based on at least three, preferably four,

  weavers. The characteristics of the device which is the subject of the invention will be described in more detail with reference to the accompanying drawings in which:

  - Figure 1 is a schematic view of a device

  form in the prior art, - Figure 2 is a schematic view similar to Figure 1 of the device according to the invention, - Figure 3 is an "exploded" perspective view of a device according to the invention adapted determining the filterability limit temperature of a sample contained in a cell, according to Standard pr EN-116,

  - Figure 4 is a perspective view of a device

  form of the invention suitable for determining the point of

  thawing of a sample contained in a cell.

  According to FIG. 2, the cooling device

  ment consists of the association of a cooling unit

  dissement 10 with Stirling or pulsed gas cycle and 11 dry contact heat transfer members allowing

  cool cell 12 to the desired temperature

as a sample for analysis.

  The assembly constituted by the transmission organs-

  heat 11 and the cell 12 is mounted on the inner part of an insulated jacket 13 containing an insulator

  thermal 14. A temperature probe 15 makes it possible to determine

  at all times the temperature of cell 12.

  More specifically, the cooling unit 10 is constituted by a compression module 16 cooperating with a cold finger 17 whose cold end 18 located opposite the compression module 16 carries the organs of

  heat transmission 11 dry contact.

  According to Figures 3 and 4, the cooling unit

  ment 10 comprises a compression module 16 essentially

  cylindrical as well as a cold finger 17 also essential-

  ment cylindrical and located in the extension of the compression module 16 coaxially with this module; the diameter of the cold finger 17 is less than that of the compression module 16. The cooling unit 10 thus formed is fixed by means of support lugs 19 mounted on the side wall of the compression module 16 on a plate of the

  steel stage 20 of determined mass to balance the vi-

  brations generated by the back and forth movement of

  pistons moving to the inner part of the re-

cold 10.

  As shown in Figures 3 and 4 the ballast plate is parallel to the longitudinal axis of the weighing unit

  cooling 10 and based on four shock absorbers 21.

  According to FIG. 3, the cold end 18 of the cold finger 17 is capped with an annular copper sleeve 22 of

corresponding dimension.

  The annular sleeve 22 is fixed to the wall la-

  teral of a copper tubular sheath 24 surrounding a

  lule 25 for determining the limit temperature of

filterability of a sample.

  According to European standard pr EN 116, the cell is constituted by a pipette 26 of particular shape consisting of a reservoir, an inlet tube and an outlet tube connected to a vacuum source. The inlet tube passes through a plug 27 closing the tubular sheath 24 and is connected at its lower end to a container 28 containing the sample to be analyzed by means of

filtration 29.

  A centering basket 30 allows the tube to be held

  inlet to the internal part of the tubular sheath 24.

  The plug 27 is also provided with a temperature probe 31 making it possible to determine at any time

  the temperature prevailing inside the container 28.

  According to FIG. 3, the assembly formed by the tubular sheath 24 and by the annular sleeve 22 covering the cold end 18 of the cold finger 17 constitutes the organs

  dry contact heat transfer system 11.

  This assembly 11 is fixed to the ballast plate, at the cold end 18 of the cold finger 17 by means of a clamping jumper 32 and a ring

upper 33.

  According to FIG. 4, the dry contact heat transmission members 11 ′ are constituted by a metal transmission plate 35 fitted on the cold finger 17

  and held thereon by means of a flange 34.

  The transmission cover 35 is applied against the cold end 18 of the cold finger 17 by the internal face

from its bottom 36.

  The outer face of the bottom 36 of the transfer plate

  mission 35 opposite the internal face by which it is applied against the cold end 18 of the cold finger 17

  carries a cell 37 for determining the defrosting point

tion of a sample.

  This cell 37 is equipped with an inlet port 38 and an outlet port 39 for the sample.

  to be analyzed as well as two optical sensors 40 and 40 '

  acting respectively as transmitter and receiver. A temperature sensor 41 fixed to the cell 36 by

  through a flange 39 makes it possible to follow at any time

  both the temperature of the sample.

Claims (5)

R E V E N D I C A T I ON S   1) Cell refrigeration device containing more or less viscous liquid samples in particular samples of petroleum products to be analyzed in particular to determine their limit filterability temperature, their thawing point, their pour point or their cloud point, this in temperature ranges which can range from around + 50 to - 120 C, characterized in that it comprises on the one hand a cycle cooling unit   Stirling or pulsed gas (10) constituted by module   pressure (16) cooperating with a cold finger (17), connected to an alternating current source and equipped with means capable   to vary the pressure of a working gas periodically   high pressure, in particular helium filling a working chamber subdivided into several compartments and extending in the compression module (16) and in the cold finger (17) so as to cause in a compartment   cold located at the end of the cold finger (17) opposite the mo-   compression dule (16) or first end (18) a   working gas tent allowing very low temperatures to be obtained at this level, and on the other hand dry contact heat transfer members (11) mounted on the cold finger (17) at the first end ( 18) thereof and cooperating with the cell containing the sample to be analyzed so as to allow cooling   this sample at the desired temperature.   2) Device according to claim 1, characterized in that   the heat transmission members (11) are constituted   killed by a metallic tubular sheath (24), in particular made of copper, surrounding the cell (25) containing the sample to be analyzed and equipped on its side wall with a sleeve (22) made of the same material whose shape and dimensions correspond to those of the first end of the finger   cold and which comes to cap this first end.   3) Device according to any one of claims 1   and 2, characterized in that the heat transmission members (11) as well as the first end (18) of the cold finger (17) are mounted on the internal part of an isothermal envelope (13) containing a thermal insulator (14).   4) Device according to any one of claims 1   to 3, characterized in that the heat transfer members (11) are equipped a temperature probe (15).   5) Device according to any one of claims 1   to 4, in which the cooling unit comprises a compression module   (16) essentially cylindrical containing at least one piss   main tone controlled by a linear or rotary motor   lying by the alternating current source and moving in   back and forth to compress the working gas in a comparison   compression material as well as a cold finger (17) also essentially cylindrical, located in the extension of the compression module coaxially with this module but having a   smaller diameter and containing a hollow sweeping piston   fold of a resiliently mounted heat exchanger moves   erasing at the same frequency as the main piston but in phase opposition, and cooperating with the latter to periodically vary the pressure of the working gas in the different compartments of the working chamber, this scanning piston subdividing the cold finger (17 ) at its internal part in two compartments communicating with each other through the heat exchanger, namely on the one hand the cold compartment located at the first end (18) of the cold finger (17)   and on the other hand a warm compartment located at the op-   placed with this finger (17) and connected to the compression compartment   compression module (16), characterized in that   the cooling unit (10) is fixed by means of support legs (19) mounted integrally on its side wall to a ballast plate (20) in particular of steel essentially5 parallel to its longitudinal axis and resting on at least three preferably four shock absorbers (21).