METHOD AND FACILITY FOR HEAT TRANSFER BETWEEN A GRANULAR MATERIAL AND A FLUID

Abstract

A method is provided for heat transfer between a granular material (14) capable of forming a moving bed, and a fluid (15). The method includes filling with said granular material (14) a cylindrical chamber (2) of which the longitudinal axis (XX′) extends horizontally in the configuration of use, supplying the chamber (2) with fluid via at least one cylindrical fluid-receiving tube (3) arranged at least partially inside the chamber (2) and rotating the chamber (2) about an axis coincident with the longitudinal axis (XX′) of the chamber (2). The tube (3) is coaxial with the longitudinal axis (XX′) of the chamber (2) and opens at each of its ends to outside the chamber (2) so as to be able to be connected to a fluid circulation circuit (5) and the filling of the chamber (2) with the granular material (14) involves filling up to a height of fill (H) within the range of heights defined by the formula: R + a × R ⁢ 1 where R corresponds to the interior radius of the cylindrical chamber (2) and R1 to the interior radius of the cylindrical fluid-receiving tube (3) and a is comprised between 0 and 1.

Description

The present invention relates to a method and a facility for heat transfer between a granular material capable of forming a moving bed, and a fluid.

It relates in particular to a method for heat transfer between a granular material capable of forming a moving bed, and a fluid, said method comprising:

• • when a cylindrical chamber is in a configuration referred to as the configuration of use in which the longitudinal axis of said chamber is extending horizontally:
    • filling said chamber with a volume of granular material corresponding to the moving bed that is to be formed,
    • supplying said chamber with fluid via at least one cylindrical fluid-receiving tube arranged at least partially inside the chamber and
    • rotating said chamber about an axis coincident with the longitudinal axis of the chamber.

It should be noted that what is meant here by granular material is a collection of mechanically interacting non-cohesive particles. These particles are able to form a moving bed under the effect of rotation. In other words, this granular material is said to be loose.

Moving-bed heat exchangers in which heat is transferred between the granular material and a fluid circulating in at least one tube arranged inside the chamber are known. These heat exchangers are increasingly being studied because of the large number of industries liable to be using granular material. Such heat exchangers may find applications in the cooling or heating of fluid from the granular material or, conversely, applications in the cooling or heating of the granular material from the fluid. However, the heat-exchanger solutions hitherto developed are expensive, consume a great deal of energy, and are not optimized.

One object of the invention is to propose a heat transfer method and facility of the aforementioned type that enable optimal transfer of heat between the granular material and the fluid without adversely affecting the simplicity of the method and of the facility, and with the facility having a relatively moderate demand for energy.

To this end, one subject of the invention is a method for heat transfer between a granular material capable of forming a moving bed, and a fluid, said method comprising:

• • when a cylindrical chamber is in a configuration referred to as the configuration of use in which the longitudinal axis of said chamber is extending horizontally:
    • filling said chamber with a volume of granular material corresponding to the moving bed that is to be formed,
    • supplying said chamber with fluid via at least one cylindrical fluid-receiving tube arranged at least partially inside the chamber and
    • rotating said chamber about an axis coincident with the longitudinal axis of the chamber, characterized in that the cylindrical fluid-receiving tube is a fixed tube coaxial with the longitudinal axis of rotation of the chamber and opens at each of its ends to outside the chamber so as to be able to be connected to a fluid circulation circuit and in that the volume of granular material serving to form the moving bed in the cylindrical chamber corresponds to the filling of the chamber with granular material to a height of fill comprised within the range of heights defined by the formula:

$R+a\times R1$

where R corresponds to the interior radius of the cylindrical chamber and R1 to the interior radius of the cylindrical fluid-receiving tube and a is comprised between 0 and 1, this height of fill corresponding to the level of granular material in the chamber when the granular material is evenly distributed through the chamber and has been leveled.

It should be noted that what is meant by the chamber being filled with granular material to a height of fill, which corresponds to the level of granular material in the chamber is that the height of fill is, when the chamber is in the configuration of use, namely when the longitudinal axis of the chamber is horizontal, defined with respect to a horizontal reference plane. This horizontal reference plane is the plane that passes through the lowermost point of the cylindrical wall of the chamber when the chamber is in the configuration of use. This level is measured when the granular material has been leveled, namely under conditions in which the upper surface of the granular material is substantially flat. This leveling of the granular material evenly distributed through the chamber may be achieved simply by rotating the chamber. It should be noted that the volume of granular material that corresponds to this height or level of fill may be determined empirically or by calculation. In practice, for example, when both a is equal to zero and the height of fill is equal to the interior radius of the cylindrical chamber, the volume of the granular material serving to form the moving bed in the chamber is equal to half the volume of the chamber minus half the volume of the tube. The tube is a fixed tube, which is to say remains immobile while the chamber is being rotated. This tube therefore does not rotate as one with the chamber. The disposition of the fluid-receiving tube such that it is coaxial with the axis of rotation of the chamber makes it possible, in combination with a predefined level of fill of the chamber, to create a uniform and dense stream of the particles that make up the granular material around the fluid-receiving tube, thereby making it possible to optimize the transfer of heat between the granular material and the fluid. This design effectively allows near-permanent contact between the tube and at least some of the granular material as the chamber rotates. In particular, this design allows the stream of granular material to circulate over both the upper part and the lower part of the fluid-receiving tube as the chamber rotates. Thanks to this regime referred to as “dual-stream flow” of the stream of granular material, convection at the surface of the fluid-receiving tube is optimized, this optimization being beneficial to the transfer of heat. The coaxial disposition of the tube inside the chamber also allows the tube to be constantly supplied with fluid, in parallel with the rotating of the chamber. Obviously, the chamber, when filled, is re-closed before being rotated.

According to one embodiment of the method, the rotating of said chamber about an axis coincident with the longitudinal axis of the chamber is performed at an angular velocity comprised between 5 and 50 rpm.

According to one embodiment of the method, the cylindrical chamber, which is bounded by a cylindrical wall and two end faces, is, in order to fill it with granular material and/or empty it, equipped with at least one pluggable opening formed in the cylindrical wall of said chamber.

As a preference, this opening extends from one end face of the chamber to the other end face.

Another subject of the invention is a facility for heat transfer between a granular material capable of forming a moving bed, and a fluid, said facility comprising a cylindrical chamber having a configuration of use in which the longitudinal axis of the chamber extends horizontally, and in which said chamber is capable of being filled with a volume of granular material corresponding to the moving bed that is to be formed, at least one cylindrical fluid-receiving tube arranged at least partially inside the chamber and a rotational-drive system for rotating the chamber about an axis coincident with the longitudinal axis of the chamber, characterized in that the fluid-receiving tube is a fixed tube which is arranged coaxial with the longitudinal axis of rotation of the chamber and which opens at each of its ends to outside the chamber so as to be able to be connected to a fluid circulation circuit, and in that the volume of granular material serving to form the moving bed in the cylindrical chamber corresponds to the filling of the chamber with granular material to a height of fill comprised within the range of heights defined by the formula

R+a×R1, where R corresponds to the interior radius of the cylindrical chamber and R1 to the interior radius of the cylindrical fluid-receiving tube and a is comprised between 0 and 1, this height of fill corresponding to the level of granular material in the chamber when the granular material is evenly distributed through the chamber and has been leveled. This facility is capable notably of allowing implementation of the method described hereinabove. Once again, the disposition of the fluid-receiving tube such that it is coaxial with the longitudinal axis of rotation of the chamber, combined with a predefined level of fill of the chamber, makes it possible to create a uniform and dense stream of the particles that make up the granular material around the fluid-receiving tube, thereby making it possible to optimize the transfer of heat between the granular material and the fluid. This design effectively allows near-permanent contact between the tube and at least some of the granular material as the chamber rotates. In particular, this design allows the stream of granular material to circulate over both the upper part and the lower part of the fluid-receiving tube as the chamber rotates. Thanks to this regime referred to as “dual-stream flow” of the stream of granular material, convection at the surface of the fluid-receiving tube is optimized, this optimization being beneficial to the transfer of heat.

According to one embodiment of the invention, the ratio of the interior radius of the chamber to the interior radius of the tube is comprised between 3 and 15.

According to one embodiment of the invention, the cylindrical chamber, which is bounded by a cylindrical wall and two end faces, is, in order to fill it with granular material and/or empty it, equipped with at least one pluggable opening formed in the cylindrical wall of said chamber. The chamber may be filled uniformly along the entire length of the chamber. Leveling may be achieved simply by rotating the chamber. As a preference, this opening extends from one end face of the chamber to the other end face.

According to one embodiment of the invention, said facility comprises at least one filling station for filling the chamber, said station comprising at least one hopper positioned above the chamber when the chamber is in the configuration of use, this hopper being mounted with the ability to move along an axis parallel to the longitudinal axis of rotation of the chamber. Once again, this disposition allows uniform filling of the chamber.

According to one embodiment of the invention, the facility comprises a collector of the granular material contained in the chamber, this collector being arranged beneath the chamber vertically in line with the opening formed in the cylindrical wall of the chamber. This makes the chamber simple to empty.

According to one embodiment of the invention, the rotational-drive system for rotating the chamber is configured to rotate the chamber at an angular velocity comprised between 5 and 50 rpm.

According to one embodiment of the invention, the rotational-drive system for rotating the chamber comprises at least one rotary member in meshing engagement with an exterior part of the chamber.

According to one embodiment of the invention, the fluid is a liquid, preferably water.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be clearly understood on reading the following description of exemplary embodiments, with reference to the appended drawings, in which:

FIG. 1 depicts a schematic view of a heat transfer facility according to the invention;

FIG. 2 depicts a view in transverse section of the chamber to illustrate the range of heights of fill of the chamber;

FIG. 3 depicts a view in transverse section of the chamber while it is being rotated so as to illustrate a “dual-stream flow” regime;

FIG. 4 depicts a partial perspective view of a heat transfer facility during the phase of filling the chamber with granular material;

FIG. 5 depicts a partial perspective view of a heat transfer facility during the phase of emptying the chamber of granular material.

As mentioned hereinabove, the invention relates to a method for heat transfer between a granular material 14 capable of forming a moving bed, and a fluid, and to the facility 1 notably for implementing such a method.

The granular material 14 may be of any kind and originate from the chemical, pharmaceutical, food or some other industry. FIG. 2 illustrates an example of a granular material 14 formed of glass beads. Ideally, the dimensions of the particles of the granular material 14 are comprised between 500 microns and 1 cm. The fluid 15 is a liquid, preferably water. Water offers good thermal-storage properties and is low in cost.

The facility 1 as illustrated in FIG. 1 comprises a cylindrical chamber 2 bounded by a cylindrical wall 6 and two end faces 7, in this instance each formed by an end plate with a central opening. This cylindrical chamber 2 has a longitudinal axis XX′ formed by the longitudinal axis of the cylinder. In the configuration of use, the longitudinal axis XX′ of the chamber 2 extends horizontally, as illustrated notably in FIG. 1.

The facility 1 further comprises a cylindrical fluid-receiving tube 3. This cylindrical tube 3 is arranged at least partially inside the chamber 2 so as to be coaxial with the longitudinal axis XX′ of the chamber 2. This cylindrical tube 3 opens at each of its ends to outside the chamber 2 or protrudes beyond said end face. The opening at each end of the tube 3 is arranged level with an end face 7 of the chamber 2 or protrudes beyond said end face. At each of its ends, this cylindrical tube 3 is connected to a fluid circulation circuit 5 so as to allow fluid to be received inside the tube 3 and said fluid to circulate inside the tube 3. To this end, the fluid circulation circuit 5 may be equipped with a pump, as illustrated in FIG. 1. Provision may be made for a rotary coupling between the tube and each end face 7 of the chamber so that the tube 3 does not rotate and only the chamber revolves about the tube 3. The tube 3 remains fixed.

Specifically, the facility 1 further comprises a rotational-drive system 4 for rotating the chamber 2 about an axis coincident with the longitudinal axis XX′ of the chamber 2. Thus, the fluid-receiving tube 3 is also coaxial with the axis of rotation of the chamber 2. This rotational-drive system 4 for rotating the chamber 2 comprises at least one rotary member 11 in meshing engagement with an exterior part of the chamber 2. This rotary member 11 here takes the form of a pinion arranged outside the chamber 2, beneath the chamber 2. This rotary member 11 meshes with a toothset on an end face of the chamber the end plate of which takes the form of a ring gear with circumferential teeth. These teeth form the toothset that meshes with the teeth of the pinion.

The drive system 4 further comprises at least one electric motor 12 engaging with the rotary member 11 to drive the rotation of said rotary member 11 about an axis parallel to the longitudinal axis XX′ of rotation of the chamber 2 and a control unit 13 controlling the electric motor(s) 12.

In the example depicted, what is provided is a drive system 4 having two assemblies made up of a motor/rotary member 11, namely one assembly per end face 7 of the chamber 2, said assemblies operating synchronously. As a variant, just one assembly may be provided.

The rotational-drive system 4 for rotating the chamber 2 is configured to rotate the chamber 2 at an angular velocity comprised between 5 and 50 rpm. The chamber 2 is intended to be filled with a volume of granular material 14 that corresponds to a height of fill H to which the chamber 2 is filled with granular material. This height H to which the chamber 2 is filled with granular material is measured with respect to a horizontal plane that passes through the lowermost point of the cylindrical wall of the chamber when the chamber is in the configuration of use. This height H corresponds to the level to which the chamber is filled with granular material. This height H is therefore measured when the granular material distributed uniformly through the chamber 2 has been leveled, as illustrated in FIG. 2. This height H is comprised within the range of heights defined by the formula R+a×R1, where R corresponds to the interior radius of the cylindrical chamber and R1 to the interior radius of the cylindrical fluid-receiving tube 3 and a is comprised between 0 and 1. It should be noted that a may be a whole number or decimal fraction. The expression “a is comprised between 0 and 1” also includes the possibility of a adopting the values 0 and 1.

In other words, the height of fill (or level of fill) of the chamber 2 is comprised between H1 and H2, where H1 is equal to R and H2 is equal to R+R1.

The height H is therefore, in order to achieve a “dual-stream flow” regime, comprised between R and R+R1. The volume of granular material corresponding to this height of fill may be determined by calculation when the dimensions of the chamber 2 and of the tube 3 and the dimensional characteristics of the granular material 14 are known, but may also be determined empirically, for example by viewing the fill. The inventors have noted that outside of this range of heights of filling, the regime is “single-stream flow”, namely the stream of granular material is located in the upper part of the tube or in the lower part of the tube, meaning that heat transfer is not optimized.

In the example depicted, the chamber 2 has a diameter equal to 40 cm. The cylindrical fluid-receiving tube 3 has a diameter equal to 10 cm. Ideally, the ratio of the interior radius of the chamber 2 to the interior radius of the tube 3 is comprised between 3 and 15.

In order to enable the chamber 2 to be filled with, and emptied of, granular material 14, the cylindrical chamber 2 is equipped with at least one pluggable opening 8 formed in the cylindrical wall 6 of said chamber 2. This opening 8 preferably extends from one end face 7 of the chamber 2 to the other end face 7.

The plugging member for plugging this opening 8 may be formed by a mobile part of the cylindrical peripheral wall 6 of the chamber 2. This mobile part may take the form of at least one flap or shutter which in the closed position closes said opening. The transition from the position in which the opening is closed to the position in which it is open may be achieved by sliding and/or pivoting and/or removing said mobile part.

The facility 1 also comprises a filling station for filling the chamber 2. This station comprises at least one hopper 9 positioned above the chamber 2 when the chamber 2 is in the configuration of use. This hopper 9 is mounted with the ability to move along an axis parallel to the longitudinal axis XX′ of rotation of the chamber 2, as illustrated in FIG. 4.

The facility also comprises a collector 10 of the granular material 14 contained in the chamber 2. This collector 10 is arranged beneath the chamber 2 vertically aligned with the opening 8 formed in the cylindrical wall 6 of the chamber 2, as illustrated in FIG. 5.

In practice, the chamber 2 is in the configuration of use, namely with its longitudinal axis XX′ extending horizontally. The opening 8 of the chamber is therefore oriented skyward in order to fill the chamber 2 with granular material 14, and the hopper 9 is moved parallel to the longitudinal axis XX′ that forms the axis of rotation of the chamber 2 in order to fill the chamber 2 evenly, namely along the entire length of the chamber 2. Leveling may then be achieved simply by rotating the chamber 2 so as to check that the level or height of fill conforms to that desired. This filling is therefore performed over the entire length of the chamber 2 thanks to the moving of the hopper 9, as illustrated in FIG. 4. Once the height of fill H has been reached, the opening 8 of the chamber is re-closed. During this filling, fluid 15 may also be conveyed into the fluid-receiving tube 3. Once the filling of the chamber 2 has been performed and the chamber 2 has been re-closed, the chamber 2 may be rotated and fluid 15 may circulate along the fluid-receiving tube 3 under the action of the pump with which the fluid-circulation circuit 5 is equipped. A transfer of heat between the granular material and the fluid may be achieved under a “dual-stream flow” regime. Temperature control may be performed on the granular material 14 and/or on the fluid 15. The rotating of the chamber 2 may be halted for example when the temperature difference between the temperature of the granular material and the temperature of the fluid is less than a predetermined value.

Because of the relative positioning of the tube 3 in the chamber 2 and because of the level of fill of the chamber 2, the heat transfer is optimal, as illustrated by FIG. 3, because the transfer of heat can occur continuously over the upper part and the lower part of the tube 3 as the chamber 2 rotates. Once the heat transfer has finished, the rotating of the chamber 2 is stopped and the chamber 2 is emptied, as illustrated in FIG. 5. To do this, the opening 8 of the chamber 2 is oriented toward the ground and opened. The contents of the chamber 2 are tipped out into the collector 10 produced in this instance in the form of a tray with an open top face, this tray being arranged beneath the chamber 2 vertically aligned with the opening 8 formed in the cylindrical wall of the chamber 2. A further filling of the chamber 2 as described hereinabove can then be envisioned in order to perform a new operation of transferring heat between a loose granular material and the fluid 15, the heat transfer operation each time involving filling the chamber 2, which is in the configuration of use, with said granular material, supplying the chamber with fluid via the cylindrical fluid-receiving tube 3 arranged at least partially inside the chamber 2, and rotating the chamber 2 about its longitudinal axis XX′. This rotating is performed in parallel with the circulating of the fluid inside the fluid-receiving tube 3.

Claims

1. A method for heat transfer between a granular material capable of forming a moving bed, and a fluid, said method comprising: R + a × R ⁢ 1

when a cylindrical chamber is in a configuration referred to as the configuration of use in which the longitudinal axis of said chamber is extending horizontally: filling said chamber with a volume of granular material corresponding to the moving bed that is to be formed, supplying said chamber with fluid via at least one cylindrical fluid-receiving tube arranged at least partially inside the chamber and rotating said chamber about an axis coincident with the longitudinal axis of the chamber, wherein the cylindrical fluid-receiving tube is a fixed tube coaxial with the longitudinal axis of rotation of the chamber and opens at each of its ends to outside the chamber so as to be able to be connected to a fluid circulation circuit and in that the volume of granular material serving to form the moving bed in the cylindrical chamber corresponds to the filling of the chamber with granular material to a height of fill comprised within the range of heights defined by the formula:

where R corresponds to the interior radius of the cylindrical chamber and R1 to the interior radius of the cylindrical fluid-receiving tube and a is comprised between 0 and 1, this height of fill corresponding to the level of granular material in the chamber when the granular material is evenly distributed through the chamber and has been leveled.

2. The heat transfer method as claimed in claim 1, wherein the rotating of said chamber about an axis coincident with the longitudinal axis of the chamber is performed at an angular velocity comprised between 5 and 50 rpm.

3. The heat transfer method as claimed in claim 1, wherein the cylindrical chamber, which is bounded by a cylindrical wall and two end faces, is, in order to fill it with granular material and/or empty it, equipped with at least one pluggable opening formed in the cylindrical wall of said chamber.

4. The heat transfer method as claimed in claim 3, wherein the pluggable opening formed in the cylindrical wall of the chamber extends from one end face of the chamber to the other end face.

5. A facility for heat transfer between a granular material capable of forming a moving bed, and a fluid, said facility comprising a cylindrical chamber having a configuration of use in which the longitudinal axis of the chamber extends horizontally, and in which said chamber is capable of being filled with a volume of granular material corresponding to the moving bed that is to be formed, at least one cylindrical fluid-receiving tube arranged at least partially inside the chamber and a rotational-drive system for rotating the chamber about an axis coincident with the longitudinal axis of the chamber, wherein the fluid-receiving tube is a fixed tube which is arranged coaxial with the longitudinal axis of rotation of the chamber and which opens at each of its ends to outside the chamber so as to be able to be connected to a fluid circulation circuit, and in that the volume of granular material serving to form the moving bed in the cylindrical chamber corresponds to the filling of the chamber with granular material to a height of fill comprised within the range of heights defined by the formula R+a×R1, where R corresponds to the interior radius of the cylindrical chamber and R1 to the interior radius of the cylindrical fluid-receiving tube and a is comprised between 0 and 1, this height of fill corresponding to the level of granular material in the chamber when the granular material is evenly distributed through the chamber and has been leveled.

6. The heat transfer facility as claimed in claim 5, wherein the ratio of the interior radius of the chamber to the interior radius of the tube is comprised between 3 and 15.

7. The heat transfer facility as claimed in claim 5, wherein the cylindrical chamber, which is bounded by a cylindrical wall and two end faces is, in order to fill it with granular material and/or empty it, equipped with at least one pluggable opening formed in the cylindrical wall of said chamber.

8. The heat transfer facility as claimed in claim 7, wherein the opening extends from one end face of the chamber to the other end face.

9. The heat transfer facility as claimed in claim 5, wherein said facility comprises at least one filling station for filling the chamber, said station comprising at least one hopper positioned above the chamber when the chamber is in the configuration of use, this hopper being mounted with the ability to move along an axis parallel to the longitudinal axis of rotation of the chamber.

10. The heat transfer facility as claimed in claim 7, wherein the facility comprises a collector of the granular material contained in the chamber, this collector being arranged beneath the chamber vertically in line with the opening (8) formed in the cylindrical wall of the chamber.

11. The heat transfer facility as claimed in claim 5, wherein the rotational-drive system for rotating the chamber is configured to rotate the chamber at an angular velocity comprised between 5 and 50 rpm.

12. The heat transfer facility as claimed in claim 5, wherein the rotational-drive system for rotating the chamber comprises at least one rotary member in meshing engagement with an exterior part of the chamber.

13. The heat transfer facility as claimed in claim 5, wherein the fluid is a liquid, preferably water.