FR2716961A1 - Device for injecting a pressurized fluid into a plate bundle of a heat exchanger. - Google Patents

Abstract

The subject of the invention is a device for injecting a fluid under pressure from a plate bundle (1) of a heat exchanger comprising channels for the circulation of said fluid, said device comprising at least one pipe (21) s 'extending over the entire width of the plate bundle (1) and provided with a first end (21a) open connected to means for supplying the pressurized fluid and with a second end (21b) closed. The pipe (21) comprises, on the one hand, calibrated orifices (22) for spraying the fluid in the channels of the plate bundle (1), distributed along generatrices and over the entire length of the pipe (21) and , on the other hand, means (23) for maintaining the fluid at a non-zero speed over its entire length and means (24) for emptying said pipe (21).

Description

The subject of the present invention is a device for injecting a fluid.

under pressure in a

  plate bundle of a heat exchanger.

  There are generally two types of heat exchangers. The first type of heat exchanger

  has a bundle of U-shaped tubes or a

  ceau of straight tubes, in which a fluid circulates.

  But this type of exchanger is of a design

  expensive and thermal efficiency is limited since the number of tubes depends on the space available

  which is in most cases restricted.

  The second type of heat exchanger, comprises a bundle of plates arranged contiguously

  and parallel to each other.

  The plates made of thin sheets, usually made of stainless steel, have edges

  with smooth surface and a central part provided with wavy-

  tions by which they are in contact with one another and by which they delimit channels forming a double circuit for the circulation of independent fluids and counter-current from one end to

the other from the heat exchanger.

  This type of plate bundle heat exchangers works with various fluids, in single phase

or in double phase.

  In the case where the charge to be heated is introduced into the exchanger in two phases, it is necessary to ensure an intimate mixture of the liquid and the gas in order to ensure a regular distribution of the mixture throughout the bundle of plates of the heat exchanger. To ensure the intimate mixing of the liquid and the gas, a phase injection device is used

liquid alone.

  This injection device consists of one or more pipes extending over the entire width of the plate bundle and provided with a first open end connected to means for supplying the fluid under

  pressure and a second closed end.

  The tubing is generally placed at the bottom of the plate bundle and its axis is

  perpendicular to the channels of said plate beam.

  In addition, the tubing has calibrated orifices for spraying the liquid into the channels of the plate bundle, along generators and

  over the entire length of said tubing.

  Pressurized liquid enters the tubing at one end, and is sprayed upward

  through all the channels of the plate beam.

  This pressurized liquid is then taken up by the gas which circulates at high speed at the entry of the fascia, mixes intimately with it, and circulates in

  the plate beam mixed with said gas.

  The double mixed phase thus created is distributed

  advantageously drank across the width of the channels and is then carried by the gas to the top of the

plate beam.

  This type of injection device used

  until now perfectly fulfills the main function

  for which it was designed, i.e. ensuring

  intimate mixing between liquid and gas and therefore

  quence, create the conditions for a homogeneous and regular distribution of the double phase as soon as it enters the

plate beam.

  On the other hand, a major drawback occurs

  sometimes, either upon commissioning, or accidentally-

permanently in operation.

  Indeed, the calibrated orifices, of small diameters, become partially or totally blocked, despite the presence of fine mesh filters at the inlet of the tubing and the installation must be periodically stopped to remove the tubing and clean it. Clogging of the calibrated orifices of the tubing is caused by fine particles, for example iron oxides or others, which come from an accumulation and stagnation of these particles

  at the bottom of the tubing, at the opposite end of the tubing

  very. Indeed, the particles which penetrate in the tubing are entrained at high speed towards the bottom of this tubing, practically in a straight line, where they crush, lose their speed, and fall to the part

  bottom of the tubing where they accumulate.

  Thus, a particle plug is formed which slowly leaves the bottom of the tubing and gradually gains the front of this tubing hiding more and more

  calibrated orifices, until complete obturation.

  The object of the invention is to avoid this inconvenience.

  comes while keeping the injection device efficient. The invention therefore relates to a device for injecting a pressurized fluid into a plate bundle of a heat exchanger comprising circulation channels of said fluid, said device comprising at least one tube extending over the entire width. of the plate bundle and provided with a first open end connected to means for supplying the fluid under pressure and with a second closed end, said

  tubing with calibrated spray orifices

  tion of said fluid in the channels of the plate bundle, distributed along generators and over the entire length of the tubing, characterized in that the tubing comprises means for maintaining the fluid at a non-zero speed over its entire length and means drain

of said tubing.

  According to other characteristics of the invention

  tion: - the means for maintaining a non-zero speed of the fluid are formed by all or part of the tubing of progressively decreasing section relative to the direction of circulation of the fluid, - the part of the tubing of progressively decreasing section is formed by a ramp portion disposed opposite the calibrated orifices and near the closed end of the tubing, - the ramp portion represents approximately 20 to 50% of the length of the tubing, - the ramp portion extends over the entire length of the tubing, - the means for emptying the tubing are formed by a sealed isolation valve disposed at

  the end of the tubing opposite the open end.

  The characteristics and advantages of the

  vention will appear during the description which goes

  follow, given only by way of example and made with reference to the appended drawings, in which: - FIG. 1 is a partial schematic perspective view of a heat exchanger fitted with the device for injecting a pressurized fluid according to the invention,

  - Fig. 2 is a partial schematic view-

  in section along line 2-2 of FIG. 1, - Fig. 3 is a schematic view showing an example of connection of a tube of the device for injecting a fluid with the means for draining

this tubing.

  In Figs. 1 and 2 we have shown sche-

  matically a part of a heat exchanger which consists of a plate bundle i arranged inside

a grille 2.

  Conventionally, the plate bundle 1 is formed by a multitude of plates 10, arranged

  joined and parallel to each other.

  The plates 10 made of thin sheets, usually made of stainless steel, have edges

  with smooth surface and a central part provided with wavy-

  by which they are in contact with one another and by which they delimit a double circuit for the circulation of independent fluids and

  against the current from one end to the other of the exchanger.

  The plate beam has, at its end

  lower part, a manifold 11 for the outlet of a heat transfer fluid, connected, on the one hand, to one of the circuits of said plate bundle 1, and on the other hand, to a

  line 12 for discharging said fluid.

  This heat transfer fluid is introduced into the corresponding circuit of the plate bundle 1 by

  the upper end of said plate bundle.

  The fluid to be heated, which in this case consists of a mixture of liquid and gas, is introduced through the lower end of the bundle

1.

  This fluid to be heated circulates in the other circuit of the plate beam 1 and against the current of the

fluid to cool.

  To this end, the calender 2 is connected to a pipe 14 for introducing gas into the corresponding circuit of the plate bundle 1. The exchanger

  thermal includes a device 20 for injecting the li-

who is in this circuit.

  Line 14 brings the gas inside the enclosure and into the beam charge circuit at

plates 1.

  The liquid injection device 20 comprises, in the embodiment shown on

  Figs. 1 and 2, parallel pipes 21 and available

  between the collector 11. In what follows, we will only describe one

  tubing 21, the other tubing being identical.

  The tubing 21 has its axis perpendicular to the channels of the corresponding circuit of the plate bundle 1 and extends over the entire width of said plate bundle 1. The tubing 21 has a first open end 21a connected to means for supplying the liquid under pressure, not shown, and a second

closed end 22b.

  This tubing 21 has calibrated orifices 22 for spraying the pressurized liquid into the channels of the corresponding circuit of the plate bundle 1, distributed along generators and over all

the length of said tubing.

  The pressurized liquid enters the tubing 21 through its end 21a, and is sprayed towards

  the top through all of the calibrated orifices 22.

  This pressurized liquid is then taken up by the gas which circulates at high speed at the entrance to the plate bundle 1, mixes intimately with it, and circulates in the channels of the corresponding circuit of the

  plate bundle 1, intimately mixed with gas.

  The double mixed phase thus created is dis-

  advantageously tribes over the entire width of these channels and is then driven by the gas to the top of the

plate harness 1.

  The tubing 21 includes means for maintaining the liquid at a non-zero speed over its entire

  length and means of emptying said tube 21.

  In fact, a laboratory analysis of the phenomenon of blockage of the calibrated orifices 22 of the pipes 21 has shown that this blockage by fine particles, often iron or other oxides, results from an accumulation and stagnation of said particles. at the bottom of the pipe 21 opposite the end

open 21a.

  This accumulation is due to the profile of

  velocities, which is zero at the bottom of the pipe 21.

  Particles entering it are entrained

  born at high speed towards the bottom, practically in a straight line, where they crash, lose their speed, and fall to the bottom of the tubing where they accumulate. A plug of debris is thus formed which leaves slowly from the bottom of the pipe 21 and gains little fear towards the front, hiding more and more orifices.

  calibrated 22 until general obturation.

  Thanks to the means for holding the liquid at a non-zero speed over the entire length of the tube 21, the fine particles are constantly entrained and follow the fluid threads until they are discharged at

through the calibrated orifices 22.

  As shown in Figs. 1 and 3, these means for maintaining a constant speed of the liquid are formed by all or part of the tube 21 of progressively decreasing section relative to the direction

  for circulation of the liquid in said tube 21.

  The part of the tubing 21 of progressively decreasing section is formed, for example, by a ramp portion 23 disposed opposite the calibrated orifices 22 and near the closed end 21b of

tubing 21.

  For example, the tubing 21 has a length of between 1 and 1.3 m, a diameter of between 5 and 15 cm and the ramped portion 23 represents

  approximately 20 to 50% of the length of the tubing 21.

  According to a variant, the ramp portion 23

  may extend over the entire length of the tubing 21.

  Thanks to the ramp portion 23, the fine particles are constantly entrained at non-speed

  zero and follow the fluid threads until they escape

  cuation through the calibrated orifices 22.

  I1 therefore no longer accumulates fine particles in the tubing 21, especially at the end 21b opposite the inlet 21a of the liquid in

said tubing 21.

  However, it may happen that the filters placed

  upstream of the pipe 21 are partially destroyed.

  In this case, the liquid is no longer filtered, and certain filter debris is found in the tube 21. These debris with a diameter greater than the diameter of the calibrated orifices 22 accumulate at the bottom of the

  tubing 21 and close the calibrated orifices 22.

  It is therefore advisable to be able to evacuate them

  during operation of the heat exchanger.

  To this end, the end 21b of the pipe 21 is equipped with means for emptying said pipe 21 which are constituted by a sealed isolation valve 24. As shown in FIG. 3, the end 21b of the tubing 21 is connected to the sealed isolation valve 24 located outside the grille 2 by a

conduit 25.

  The conduit 25 is connected, on the one hand, to the end 21b of the pipe 21 by a flange 26 and a bayonet system 27 and, on the other hand, to the valve

isolation 24 by a flange 28.

  The conduit 25 can be produced either using a flexible hose or using a rigid conduit

  fitted with two expansion joints 29.

  The downstream side of the isolation valve 24 is

  connected to a discharge circuit, not shown.

  If the tubing 21 is blocked by large debris, there is an increase in the loss of

load through tubing 21.

  In this case, the isolation valve 24 is then quickly opened for a very short time and under the effect of the pressure, the debris plug is immediately removed.

  Then, the isolation valve 24 is immersed.

  immediately closed, as soon as the pressure drop in the

  tubing 21 returns to its normal value.

  The injection device according to the invention makes it possible to avoid an accumulation of debris inside the tubing, while retaining its efficiency.

Claims (6)

  1. Device for injecting a pressurized fluid into a plate bundle (1) of a heat exchanger comprising circulation channels of said fluid, said device comprising at least one tube (21) extending over the entire width of the plate bundle (1) and provided with an open first end (21a) connected to means for supplying the pressurized fluid and with a closed second end (21b), said tube (21) having calibrated orifices ( 22) spraying said fluid into the channels of the plate bundle (1), distributed along generators and over the entire length of the tubing (21), characterized in that the tubing (21) comprises means (23) for maintaining the fluid at a non-zero speed over its entire length of the tubing (21) and means (24) for draining said tubing.   2. Device according to claim 1, characterized in that the means (23) for maintaining a non-zero speed of the fluid are formed by all or part of the tubing (21) of progressively decreasing section relative to the direction of circulation of the fluid . 3. Device according to claim 2, characterized in that the part of the tubing (21) of progressively decreasing section is formed by a ramp portion (23) disposed opposite the calibrated orifices (22) and near the end (21b) closed tubing (21).   4. Device according to claim 3, characterized in that the ramped portion (23) represents   approximately 20 to 50% of the length of the tubing (21).   5. Device according to claim 3, characterized in that the ramp portion (23) extends   over the entire length of the tubing (21).   he 6. Device according to claim 1, characterized in that the means for emptying the tubing (21) are formed by a sealed isolation valve (24) disposed at the end (21b) of the tubing (21) opposite to the end (21a) open.