JPH0674688A - Heat exchanger particularly for corrosive fluid - Google Patents

Abstract

PURPOSE: To reduce an occupation volume and save an occupation position by providing a first group of flow passages for passage of a fluid communicated with opposing two surfaces and providing electrical heating means on at least another one flow passage group communicated with at least another one surface of a heat exchanger. CONSTITUTION: A block 1 is a substantially cube, and includes a first group 2 of a flow passage substantially parallel to a direction A for the purpose of passing a corrosive fluid to be kept in temperature. Further, the block 1 includes another flow passage group 3 having electrical heating means 4 which is substantially parallel to a direction B and is communicated with at least one surface of a cube perpendicular to the direction B for heating a fluid circulating in the block 1 and the flow passage 2. Hereby, there is ensured a heat exchanger which has a heat exchange output of about to 5 MW per 1 m<2> of the heat exchanger and which functions in a temperature range of -100 deg.C to 400 deg.C with a small occupation volume particularly for a corrosive fluid.

Description

Detailed Description of the Invention

[0001]

The present invention relates to heat exchangers, especially for corrosive fluids.

[0002]

2. Description of the Related Art In the chemical industry, agricultural product processing industry and surface treatment industry, corrosive fluids which must be maintained at a relatively constant temperature are used. If these corrosive fluids are the source of endothermic or exothermic reactions, it is necessary to heat or cool them in order to maintain them at the working temperature.

For this purpose, the corrosive fluid is passed through a heat exchanger, which is most often outside the treatment tank or reactor. Here, forced circulation of the fluid is carried out using tubing connected to a circulation pump. These heat exchangers are generally made of metal using can mill technology and are particularly susceptible to corrosion at the location of stressed welded or cold worked parts. Moreover, these heat exchangers occupy a very large area, so that with this known technique it is difficult to exceed a heat exchange power output of more than 1 MW / m ³ of the volume of the exchanger.

[0004]

The object of the present invention is to have an improved heat exchange output of about ³ MW to 5 MW per 1 m ^{3 of} exchanger,
Heat exchange, especially for corrosive fluids, that operates in the preferred operating temperature range of -100 ° C to + 400 ° C, enabling more than half the occupied volume reduction and significant space savings over the current state of the art. By creating a vessel
The purpose is to correct the above-mentioned drawbacks existing in the technical field.

[0005]

The heat exchanger according to the invention comprises a first group of flow paths for passage of a fluid to be heated or cooled leading to two opposite faces thereof, the heat exchanger It is characterized in that it further comprises at least another channel group leading to at least another face of the vessel, and that this other channel group is provided with electric heating means.

In the past, in order to manufacture a heat exchanger, a material having excellent thermal conductivity, being insensitive to corrosion, and having no porosity when contacted with a target fluid has been used. It was These materials are, for example, copper alloys mainly for liquids containing water, iron alloys for hydrocarbons, non-porous graphite for strong acids or graphite impregnated with materials such as polytetrafluoroethylene or phenolic resins or carbon. Is. These materials, which have good thermal conductivity, also generally have good electrical conductivity, which allows one skilled in the art to consider the risk of electric shock or short circuit, especially after a long service life in corrosive environments. In addition, it has been avoided to provide these materials with electrical heating means.

Advantageously, the heat exchanger is arranged in such a way that the first group of channels is substantially orthogonal to the other group of channels. This arrangement therefore adjusts the separation between the pipe groups in a way that avoids stresses due to thermal expansion and prevents leakage from the first flow channel group to the other pipe group, as well as the corrosive fluid At the same time, a third working axis, which is substantially perpendicular to the circulation axis and the installation axis of the electric heating means, is released, which serves for the passage of a cooling or preheating fluid, especially in the case of an endothermic or exothermic reaction It becomes possible to use it for installing the third channel group.

Preferably, the heat exchanger according to the invention comprises at least one distribution box or at least one cover together with the packing. Therefore, the distribution box allows the corrosive fluid to pass through the exchanger in multiple successive passes in a manner that optimizes the temperature rise curve and increases heat exchange efficiency. The shroud hermetically isolates the end of the heating means protruding from the group of channels it covers.

Preferably, the heat exchanger according to the invention is
The heat exchanger includes at least one temperature sensor mounted in a hole made in heat exchange with the heat exchanger. Therefore, the temperature sensor transmits in steady state the temperature of the block which is approximately equal to the operating temperature of the corrosive fluid, as well as temperature regulation, as well as heat to excessive temperatures that are incompatible with the mechanical strength required during operation of the exchanger. Allows protection of the entire exchanger.

Advantageously, the heat exchanger according to the invention comprises at least one channel group comprising a layer of tubes double-molded with a corrosion-resistant and excellent heat-conducting material. This arrangement allows the entire layer to be double-molded with a relatively inexpensive material of good thermal conductivity, if the material for the layer of corrosion resistant tube is too expensive, thus The cost of the heat exchanger can be reduced without compromising the heat transfer efficiency.

Advantageously, one channel group is realized by drilling a predetermined diameter and separation distance across at least one block of non-corrosive, non-porous material. The realization of holes by machining thus makes it possible to obtain better accuracy, better than the heat exchangers used in can manufacturing plants, and to comply with the external dimensions and performance specified for heat exchangers. .

Also preferably, the heat exchanger according to the invention has at least one electric heating resistor. This electric heating resistor rapidly reaches a constant high temperature depending on the strength of the current passing through it, thus making it possible to use the current passing through the resistor to accurately follow the temperature curve to be observed.

The heat exchanger according to the invention advantageously contains a thermally conductive powder inside the channel between the two closed ends of the channel. The thermally conductive powder is thus
Efficient heat transfer means between the flow path of the heat exchanger in which the electric heating means is housed and the rest of the heat exchanger while absorbing the thermal expansion without creating excessive internal stress Are configured.

Preferably, the powder fixes a heating wire in place in the hole so as to achieve an electrical heating resistance. Thus, this arrangement preferably results in a monoblock with a self-contained resistor that exhibits better thermal conductivity than a known type of shielding resistance inserted into the flow path in contact with powder that is preferably electrically insulating. It is possible to build a heat exchanger.

The present invention will now be described with reference to a particular embodiment, taken by way of non-limiting example with reference to the accompanying drawings.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a heat exchanger according to the invention, which can be operated up to a working pressure of 10 bar absolute, has a corrosion resistance such as graphite impregnated with polytetrafluoroethylene and an excellent thermal conductivity Contains a central block of material. The block 1 is made in the form of a right prism with a substantially flat surface. In the embodiment of FIG. 1, block 1
Is substantially cubic and has a first group 2 of channels that are substantially parallel to the direction A intended for the passage of corrosive fluids which are to be maintained in temperature. The first group of channels 2 is made in the form of a substantially cylindrical hole which runs on two opposite faces of a cube transverse to the block and orthogonal to the direction A. Block 1 is substantially parallel to direction B and
It includes another channel group 3 with electrical heating means 4 which is connected to at least one face of the cube orthogonal to the block 1 and is capable of heating the fluid circulating in the block 1 and the channel 2.

The block 1 likewise has a passage for a cooling or temperature-maintaining fluid, whether corrosive or not, which leads to at least one face of a cube which is substantially parallel to the direction C and orthogonal to the direction C. One flow channel group 5 that enables
Also attached. The electric heating means 4 may be an electric heating resistance, such as a shield heating element with a sheath electrically insulated from the conductor under voltage, the substantially cylindrical channels 2, 3,
The cross-sectional shape of 5 is adapted according to the desired heat exchange area. This cross section, which is generally circular, may likewise be oval, polygonal or star-shaped, preferably the edges are rounded.

If the heat exchanger is connected to a corrosive fluid circulation conduit, it separates the circulation of the corrosive fluid and the cooling fluid in relation to the outside and between each other. Distribution box 6, 7 and packing 8
have. These packings may be cut into sheets with a material such as polytetrafluoroethylene, or may also be made of expanded polytetrafluoroethylene or compressed expanded graphite. The electric heating means is likewise protected by a cover 9 which isolates the end under voltage from the electric heating means 4. This cover 9 is a parallelepiped-shaped box open on one side, similar to the shape of the distribution boxes 6, 7.

The distribution box or shroud is protected against corrosion by a adapted coating such as polytetrafluoroethylene (called Teflon coating).
The channels 2 that are substantially parallel to each other do not intersect the channels 3 and 5 that do not intersect with each other.
The tightness of the fluid between each other and with the electric heating means is
For this reason, it is realized in a state in which there is no porosity of the material that may connect the various flow paths 7, 3, 5.

In order to manufacture the cube 1, corrosion resistance and corrosion resistance are preferably provided by drilling parallel holes of a predetermined diameter and separation which communicate over a pair of opposite faces of the cube 1. Machining a block of non-porous material with good thermal conductivity. The parallel holes 2 of the first flow channel group lie in a plane that is also substantially orthogonal to the drilling surface of the flow channel group 5 and is substantially perpendicular to the drilling surface of the other flow channel group 3.

Referring to FIGS. 2A, 2B and 2C, three faces of the cube 3 (ie, an inlet face 10 for corrosive fluid, an installation face 11 for electric heating means, and an outlet face for cooling fluid). 12) as well as packing 6 for the fluids mentioned above. The same reference numerals as those in FIG. 1 are used in FIG.
The same elements are shown in (B) and (C). Figure 2
In (B), it can be seen that the flow path 3 is not equipped with the electric heating means 4. Since each flow path is made to have no intersection with any other flow path, heat transfer is necessarily conducted by conduction through the block 1. The heat transfer efficiency is therefore dependent on the quality of the thermal contact at the walls of the channels and the thermal conductivity of the material chosen to make the block 1. In particular, the electrical resistance 4 heats the block 1 during its use, which also transfers this heat to the fluid passing through the block, so that the heat between the electrical resistance 4 and the inner wall of the flow path 3 is reduced. The quality of the contact is important for the good operation of the heat exchanger. However, too tight adjustment will result in excessive stress as a result of thermal expansion. At this time, a large number of thermal cycles will cause cracks to be formed in the block, deformation, clogging of the electric resistance 4 in the flow path 3, and eventually seizure.

In the case of a heat exchanger connected to a fluid conduit,
The distribution boxes 6, 7 are assembled to the cube 1 with the packing 8 in between by known means or gluing such as braces, dowels, threaded rods and associated nuts. Advantageously, in a channel 3 or in a hole made in the cube 1 in heat exchange with the material of the cube 1,
One or more temperature sensors are arranged. This heat exchange is obtained through the interposition of adhesives or conductive greases or silicon-based materials filled with copper, aluminum, silver or similar metals. Considering that all heat exchange, whether by heating or by cooling, takes place through block 1, block 1 maintains the temperature of the fluid circulating therein very close to the temperature of the block. It can be seen that it constitutes one heat block with a tendency. This temperature maintenance makes it possible to limit the volume of corrosive fluid in the heat exchanger and thus the total amount of corrosive fluid to be used. A temperature sensor or measuring probe in heat exchange with the cube 1 is generally connected to a regulating device of a known type for controlling the power supply for heating the corrosive fluid and the cooling or preheating fluid.

Referring to FIGS. 3, 4 and 5, a heat exchanger according to the present invention similar to that shown in FIG. 1 has a flow path corresponding to the corrosive fluid and the cooling fluid, which is Basic parallelepipeds 21 assembled together in a gas-tight manner by means of threaded rods 22 or by other means such as gluing, continuous bolting or frame shielding
A cube 21 made in the form of a, 21b, 21c, 21d
Is included. The required air tightness is obtained by interposing a packing (not shown) similar to the packing 8 of FIG. 1, or interposing a paste, or by gluing.

This basic block-shaped arrangement enables mass production of the module structure and basic blocks, resulting in cost reduction due to economies of scale. Similarly, looking at FIG. 5, an electrical protective covering 23
Allows the connection of the electric heating elements 4, for example in series connection as represented in FIG. Similarly, the distribution box 24
a, 24b, 24c and 25a, 25b provide multiple passes in a manner that enhances heat transfer between the block and the fluid, eg, FIG.
In the case of, it may be arranged in such a way that one of the fluids circulates in four passes (the "pass" is a technical term,
Refers to the one round trip of one fluid in a heat exchanger). This arrangement makes it possible to easily insulate the whole by means of one insulating lining 26 (limited by the dashed line). From this lining, heating element 4
An electrical protective shroud 23 is located at a distance approximately equal to the thickness of this lining 26 from the heated part of the.

In the cover 23 remote from the block 1 at a constant high temperature, the connection of the electrical resistance 4 is thus arranged in such a way that it is not degraded by the high temperature of the block 1. A temperature sensor 27, which is housed in a hole of an axis substantially parallel to the electric heating element 4 and for measuring the temperature at a substantially central position of the block 21, likewise has an electrical protective cover 2
3 and the connection of the sensor 27 is not shown.

Looking at FIG. 6, the flow channel groups are not realized by penetrating into a block of material, but rather in planes that are substantially orthogonal to each other in such a way that the tubes are regularly spaced apart from one another. Corrosion resistant tube layers 32, 3 in
It is composed of 3, 35. Once the tube layer assembly is placed according to the predetermined separation distance, it uses a material 30 with excellent thermal conductivity such as cement, resin or aluminum alloy cast by fusion to cover the three flow channel groups. To do. The double molding of the assembly thus realized constitutes a block with dedicated piping or passages. Preferably, this double molding is done under vacuum or pressure, thus preventing the appearance of casting defects or porosity which is detrimental to good heat transfer.

Alternatively, a heating resistance layer 33 may be used to melt a powder mass of material having excellent thermal conductivity and thus cover the above three flow channel groups. Typically, a resistive, shielded and insulated element is used whose outer surface is metallic and is generally cylindrical in shape to cover the holes of FIG. However, when some kind of brittle material is used to make the block 1, the outer metal cylinder of resistance creates expansion, an excessive stress that can damage the block by causing cracking or contraction. there is a possibility. In this case, in particular, powder compacted inside the holes 3 around the heating element 4 can be used to mount an insulated electrical resistance on the cylindrical outer surface. The powder is preferably thermally conductive and comprises, for example, silicon dioxide, magnesium oxide or a ceramic pearl assembly interposed in the powder. The ends of the holes are preferably closed with resin to avoid powder leakage or loss.

Referring again to FIG. 7, the direct block 1 is also shown.
It is also possible to realize the insulation resistance directly inside the hole or the channel 3 provided for that purpose. Therefore, the hole 3 formed in the block 1 is provided with the heating wire 40 extended by the end of the current introducing path 41. This heating wire 4
The zeros are preferably fixed in place in the electrically insulating powder 42.

This powder is compressed by mechanical means and agglomerated by vibration inside the flow path 3. The ends 43 and 44 of the flow path 3 are generally closed by a resin, for example a resin called a "hot" resin based on silicon or any other heat resistant closure means. Thus, this arrangement allows no thermal stress to be created on the block, as no component is rigid and does not exert significant stress as it expands.

Similarly, a ceramic pearl assembly or a ceramic pearl assembly passed through the heating wire 40 in a manner to enhance the electrical insulation of the wire 40 in relation to the hole 3, especially when the material of the block 1 exhibits significant electrical conductivity. It is also advantageous to use a perforated ring assembly. As an airtight device for the ends of the channel 3, a closure device 43, 4 made of polytetrafluoroethylene or other non-conductive natural or synthetic material.
4 can be used.

Naturally, the invention is not limited to the embodiments described above, and numerous variants can be added without departing from the scope of the invention. Thus, the shape of the blocks can be any, as long as it is suitable for realizing a two-dimensional or three-dimensional resolution of completely different channels distributed in the shape of a plurality of parallel channel groups which do not intersect. Preferably, in the case of a part machined according to three orthogonal axes, a rectangular parallelepiped shape is used. The number of flow paths may be arbitrary, as is the number of continuous paths in which any one fluid runs in the exchanger. As long as substantially all of the volume of the central block is used, the flow passages may or may not lead to two opposite faces of the heat exchanger. Finally, the number of temperature sensors, their arrangement as well as their arrangement of electrical connections can be any, optionally within or outside the electrical junction box of the heating means.

[Brief description of drawings]

FIG. 1 is a schematic exploded perspective view of a heat exchanger according to the present invention.

2 is a side view of a block of the heat exchanger, (A) is a side view taken along the direction A of FIG. 1, (B) is a side view taken along the direction B of FIG. 1, and (C) is a view. It is a side view which followed the direction C of 1.

3 is a cross-sectional view of a heat exchanger according to the present invention, FIG.
FIG. 3 is a III-III arrow view of FIG.

FIG. 4 is a top view of a heat exchanger according to the present invention.

5 is a cross-sectional view of a heat exchanger according to the present invention, FIG.
FIG. 5 is a VV arrow view of FIG.

FIG. 6 shows a schematic perspective view of another embodiment of a heat exchanger according to the invention.

FIG. 7 is a schematic cross-sectional view of an electric heating resistor covering a flow path of a heat exchanger according to the present invention.

[Explanation of symbols]

 1, 21-Block 2, 3, 5-Channel group 4-Electric heating means 6, 7-Distribution box 8-Packing 9-Cover 30-Heat conductive material 32,33-Corrosion resistant tube 40-Heating wire 42 -Powder

Claims (10)

[Claims] 1. A heat exchanger, in particular for a corrosive fluid, comprising a first group of channels for the passage of this fluid, said channels leading to two opposite faces of the exchanger. Such a heat exchanger further comprising at least another channel group (3) leading to at least another face (11) of the heat exchanger, and the other channel group. A heat exchanger, characterized in that the is equipped with an electric heating means (4). 2. A heat exchanger according to claim 1, characterized in that the first channel group (2) is substantially orthogonal to the other channel group (3). 3. At least one cover (9) with at least one packing (8) or at least one distribution box (6, 7), characterized in that it comprises at least one. The heat exchanger according to item 1. 4. The heat exchanger includes at least one temperature sensor mounted in a hole made in heat exchange with the heat exchanger. The heat exchanger according to item 1. 5. At least one channel group is characterized in that it comprises a layer of corrosion-resistant tubing (32, 33) double-molded with a good heat-conducting material (30). Item 5. The heat exchanger according to any one of items 1 to 4. 6. At least one channel group (2,
3, 5) is carried out by drilling a predetermined diameter and separation distance across at least one block (1, 21) of non-corrosive non-porous material. The heat exchanger according to any one of claims 1 to 5. 7. A heat exchanger according to claim 1, characterized in that it comprises at least one electric heating resistor (4). 8. The heat exchanger according to claim 1, wherein the flow path contains a thermally conductive powder (42). 9. Heat exchanger according to claim 8, characterized in that the powder (42) is electrically insulating and preferably comprises silicon dioxide or magnesium oxide. 10. The powder (42) immobilizes the heating wire (40) in place in the hole (3) by electrically insulating the heating wire (40) from the wall of the hole (3). The heat exchanger according to claim 9, wherein: