Heat exchange – With cleaning means for heat exchanger
Reexamination Certificate
1998-05-07
2001-03-06
Leo, Leonard (Department: 3743)
Heat exchange
With cleaning means for heat exchanger
C165S119000, C210S411000
Reexamination Certificate
active
06196301
ABSTRACT:
FIELD OF THE INVENTION
The subject of the present invention is a device for injecting pressurized fluids into a multiplate heat exchanger and to a method for cleaning such an injection device.
BACKGROUND OF THE INVENTION
Multiplate heat exchangers are generally formed by a leaktight chamber and by a plate pack placed in the said leaktight chamber and leaving a free space between them.
The plate pack is composed of a stack of mutually parallel plates leaving, between them, independent fluid flow circuits.
The plates, made of thin sheet metal, usually stainless steel or any other sufficiently ductile material, have edges with a smooth surface and a central part provided with corrugations by means of which they are in contact with one another and by means of which they delimit channels forming independent fluid flow circuits from one end of the heat exchanger to the other.
This type of heat exchanger with a plate pack operates with various fluids, in one-phase or two-phase mode.
If the charge to be heated is introduced into the exchanger in two-phase mode, it is necessary to mix the liquid and gas intimately so as to ensure uniform distribution of the mixture throughout the plate pack of the heat exchanger.
In order to ensure that the liquid and gas are intimately mixed, a device for injecting only the liquid phase is used.
This injection device consists of one or more nozzles which extend over the entire width of the plate pack and are provided with an open first end connected to pressurized-fluid feed means and with a closed second end.
The nozzle is generally placed in the lower part of the plate pack, and its axis is perpendicular to the channels of the said plate pack.
Moreover, the nozzle has calibrated holes for spraying the liquid into the channels of the plate pack, along generatrices and extending over the entire length of the nozzle.
The pressurized liquid enters the nozzle at one end and is sprayed upwards across the channels of the plate pack.
This pressurized liquid is then taken up by the gas, which flows at high speed, at the inlet of the plate pack, mixes intimately with the gas and flows, mixed with the gas, through the plate pack.
The two-phase mixture thus created is advantageously distributed over the entire width of the channels and is then entrained by the gas as far as the top of the plate pack.
This type of injection device perfectly fulfils the main function for which it was designed, namely, to ensure intimate mixing between the mixture and the gas and, consequently, to create the conditions for homogeneous and uniform distribution of the two-phase mixture as soon as it enters the plate pack.
A major drawback resides in the fact that the calibrated holes in the injection nozzles may be partially or completely blocked because of the presence in the liquid of particles or debris, for example metal particles or debris, despite the presence of filters inside the feed pipe for the liquid.
Thus, the operation of the heat exchanger is disturbed and its performance gradually deteriorates.
The injection nozzles must therefore be able to be cleaned regularly and, to accomplish this, the entire plant is shut down in order to be able to remove these injection nozzles and to clean them.
The operations of dismantling and cleaning the injection nozzles, and of refitting them, require, on average, shutting down the plant for one week.
SUMMARY OF THE INVENTION
The object of the invention is to avoid these drawbacks, while at the same time maintaining the efficiency of the injection device.
The subject of the invention is therefore a device for injecting pressurized fluids into a multiplate heat exchanger of the type comprising:
a leaktight chamber provided with means for feeding and discharging a first pressurized fluid,
a plate pack placed in the chamber and composed of a stack of plates which leave, between them, channels for the flow of this first fluid mixed with a second pressurized fluid, as well as for the flow of a heat-transfer fluid, and
at least one nozzle, for injecting the second fluid, which is provided with calibrated holes and extends over the entire width of the plate pack,
wherein the nozzle has a closed end and an open end which is connected to a pipe for feeding the second fluid, the pipe being provided with a shut-off means, and is further connected to a pipe for discharging the particles deposited on a filter unit placed inside the nozzle downstream of the point where the pipes join the nozzle with respect to the direction of flow of the second fluid, the discharge pipe being provided with a shut-off means.
According to other characteristics of the invention:
the filter unit is flat and extends perpendicular to the axis of the injection nozzle,
the filter unit has the shape of a pocket whose opening is directed towards the upstream end of the injection nozzle,
the pocket is conical in shape,
the filter unit is formed by a rigid support provided with holes and fixed to the internal wall of the injection nozzle, and by a fine-mesh filter pressed against that face of the rigid support which runs counter to the direction of flow of the second fluid,
the filter unit is formed by a rigid support provided with holes,
the fine-mesh filter is removably fitted onto the rigid support, and
the discharge pipe is placed along the axis of the nozzle for injecting the second fluid.
Another subject of the invention is a method of cleaning a pressurized-fluid injection device of this type. This method consists, during the operation of the multiplate exchanger, in cutting the supply of the second fluid by shutting off the pipe for feeding this second fluid, in opening the discharge pipe and in making the first fluid pass through the injection nozzle in the opposite direction to the direction of flow of the second fluid in order to dislodge the particles deposited on the filter unit and to discharge them via the discharge pipe.
REFERENCES:
patent: 1536415 (1925-05-01), Beck et al.
patent: 3941697 (1976-03-01), Johnson
patent: 4271019 (1981-06-01), Galletti
patent: 4413675 (1983-11-01), Gano
patent: 4612116 (1986-09-01), Hindman et al.
patent: 5190095 (1993-03-01), Fujimoto et al.
patent: 26 13 835 (1976-10-01), None
patent: 0 343 531 (1989-11-01), None
patent: 0 670 464 (1995-09-01), None
patent: 2 697 906 (1994-05-01), None
patent: 1 207 919 (1970-10-01), None
Leo Leonard
Packinox
Pollock, Vande Sande & Amernick, R.L.L.P.
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