EP2179239A1

EP2179239A1 - Heat exchanger with mini- and/or micro-channels

Info

Publication number: EP2179239A1
Application number: EP08775095A
Authority: EP
Inventors: Stefano Bernardinello; Andrea Bottazzo
Original assignee: MTA SpA
Current assignee: MTA SpA
Priority date: 2007-07-23
Filing date: 2008-07-15
Publication date: 2010-04-28
Also published as: WO2009013180A1; ITPD20070251A1

Abstract

A heat exchanger (1), with m ini- and/or m icro-channels, com prises a plurality of m ultiport tubes (2), extending between respective m anifolds (3,4) with a substantially longitudinal distribution, m utually spaced by respective interspaces (7) and distributed so as to form opposed surfaces (5, 6) of the heat exchanger (1) substantially parallel to the longitudinal direction (X) of the tubes; the exchanger further com prises a plurality of dividers (8) disposed in said interspaces (7) and capable of form ing a plurality of contiguous flow paths, through which a thermal exchange fluid is conducted from one to the other of said opposed surfaces (5, 6).

Description

HEAT EXCHANGER WITH MINI- AND/OR MICRO-CHANNELS. Technical field

The subject of the present invention is a heat exchanger with mini- and/or micro-channels, of the type including the characteristics mentioned in the preamble of the main claim, and a method for the construction of such an exchanger.

The invention is proposed mainly, but not exclusively, for applications of exchangers having the function of evaporator, or condenser, for a fluid liquid, such as for example water, or for a compressed gas. Technological background

In this technical field, the exchangers defined above are sub-divided into exchangers with mini-channels and with micro-channels according to the measurement of the passage cross-section of the channels, which is obviously smaller in the micro-channels than the cross-section of the mini-channels. They are also known by the term parallel flow exchangers, and are mainly used for applications in the motor vehicle and heat-technology field. In the first case such devices are employed for the cooling of the fluids circulating in the engines and of exchangers for the air-conditioning system of the vehicle, while in the second they are used as air condensers for refrigerating equipment.

The mini- and/or micro-channels are typically produced in pipes of flattened cross-section, by means of respective longitudinal dividing partitions. Such pipes, known by the term "multiport" tubes, in the applications described above are traversed by a thermal exchange medium such as, for example, a refrigerating fluid, and are typically connected to two manifold tubes, respectively for inlet and outlet. The multiport tubes are interconnected with one another by means of finning.

The typical geometric configuration is that of a radiator in which there are two front surfaces, respectively for inlet and outlet, for a primary working fluid of the gaseous type, typically ambient air, in thermal contact with the external walls of the multiport tubes and with the interconnecting finning. Exchangers of the aforesaid type are known, for example, from US 2006/0102332 and US 2002/0066554. This type of exchanger proves unsuitable, from the point of view of thermodynamic efficiency, for applications in which the primary fluid consists of liquids, for example water, or of compressed gases. The geometry of such exchangers in fact provides a high ratio between front surface and longitudinal length, traversed by the primary fluid. As a consequence, in order to obtain a convenient value for the thermal exchange coefficient it is necessary to maintain the speed of the primary fluid through the finning at a high level. This, in the majority of cases in which the primary fluid is an incompressible, or a compressed gas, would result in values being reached for flow rate and/or pressure of the primary fluid through the front surface that are beyond the limits of technological and economic feasibility. A solution to the problem could be to provide for the use of a plurality of exchangers with mini- and/or micro-channels finned with a reduced front surface, arranged in series. However, this does not represent an optimum option either from the point of view of the overall dimensions, or of the relative complexity, or of the production costs. Description of the invention The main aim of the present invention is that of providing a heat exchanger with mini- and/or micro-channels which is structurally and functionally designed to remedy all the drawbacks mentioned with reference to the prior art cited. This and other aims which will become clearer hereinafter are targeted and achieved by the invention by means of a heat exchanger with mini- and/or micro-channels which is produced according to the following claims. Brief description of the drawings

The characteristics and advantages of the invention will become clearer from the detailed description of a preferred, although not exclusive, embodiment thereof, provided by way of non-limiting example with reference to the appended drawings, in which:

- Figure 1 is a diagrammatic axonometric view of a heat exchanger with mini- and/or micro-channels which is produced according to the invention; - Figures 2 to 4 are three diagrammatic views of three respective alternative embodiments of the exchanger of Figure 1;

- Figure 5 is a diagrammatic sectional view of the alternative embodiment of Figure 4;

- Figure 6 is a diagrammatic sectional view of a respective alternative embodiment of the exchanger of Figure 1;

- Figure 7 is a section along the line VII-VII of Figure 6. Preferred embodiments of the invention

With reference to Figure 1, a heat exchanger 1 with mini- and/or micro- channels comprises a plurality of multiport tubes 2 with flattened cross- section, traversed by a refrigerating fluid. The tubes 2 are substantially parallel to one another and extend between an inlet manifold 3 and an outlet manifold 4 for the refrigerating fluid, with a substantially longitudinal distribution, defined by the axis X of each tube 2. The distribution of the tubes 2 forms two opposed surfaces 5, 6, substantially parallel to the axis X, each of which forms a tangent to each of the tubes 2. The tubes 2 are mutually spaced by respective interspaces 7, traversed by a primary thermal exchange fluid. The primary thermal exchange fluid is, for example, water to be cooled or a compressed gas. The exchanger 1 comprises a plurality of dividers 8, transverse with respect to the longitudinal direction X, each of which extends between a pair of adjacent multiport tubes 2. The dividers 8 subdivide each interspace into a plurality of sections 9. The sections 9 form a plurality of respective flow paths 10 through which the primary thermal exchange fluid is conducted from one to the other of the surfaces 5, 6. The fluid flows through the sections 9, passing from one section to another, contiguous therewith, by means (not shown) for transferring and reversing the flow, which are located at the surfaces 5, 6. Such means may comprise, for example, a plurality of manifolds. According to the alternative embodiment of Figure 2, in addition to the transverse dividers 8, the exchanger 1 comprises a plurality of dividers 1 1 , extending longitudinally, in a direction parallel to the axis X. The plurality of dividers 8, 1 1 subdivide the exchanger 1 into a plurality of sections 12, having a substantially rectangular profile and traversed by the thermal exchange fluid, on a plurality of contiguous flow paths, in a sim ilar manner to that described for the example of Figure 1 . I n the example of Figure 2, the exchanger 1 also comprises finning 13, including a plurality of fins 13a extending in the interspaces 7.

According to the alternative embodiment of Figure 3, a heat exchanger 15 with mini- and/or m icro-channels comprises a plurality of identical groups 16a,b,c,d (four groups in the example shown) , substantially identical to the exchanger of Figure 1 , or to the exchanger of Figure 2. The fluid flows through the groups 16a,b,c,d in series, passing from one group to another by means (not shown) for transferring the flow such as, for example, a plurality of manifolds. According to the alternative embodiment of Figures 4 and 5, a heat exchanger 20 with m ini- and/or micro-channels comprises a plurality of dividers 21 substantially parallel to the longitudinal direction defined by the axis X. I n each interspace 7, devoid of finning, in an intermediate position between the two m ultiport tubes 2 which delim it the interspace, a corresponding divider 21 is provided. Means and counter-means for blocking the surfaces 5, 6 are associated with the dividers 21 , so as to distribute each interspace 7 into respective contiguous channels 24a,b which are located on opposite sides with respect to the corresponding divider 21 . The channels 24a, b are traversed by the thermal exchange fluid in opposite directions, respectively outward and return directions. The blocking means comprise a metallic plate 22, parallel and adjacent to the surface 5, substantially orthogonal with respect to the dividers 21 and integral with the latter. Between the plate 22 and each of the tubes 2 a passage 23 is provided for com m unication between adjacent interspaces 7.

The counter-means comprises a metallic plate 26, opposed to the plate 22. The plate 26 is located on the blocking surface 5, in such a way as to be in contact with the plurality of tubes 2. The channels 24a,b are placed in comm unication via a respective opening 25 extending from the free end of the corresponding divider 21 to the plate 26. The primary thermal exchange fluid traverses the exchanger 20 in a transverse direction with respect to the longitudinal axis X, passing in sequence through the channels 24a, b along the path 27, shown diagram matically in Figures 4 and 5.

According to an alternative embodiment of the invention (not shown) , dividers 21 are provided in only some of the interspaces 7. The interspaces 7 without a divider 21 , as in a further alternative embodiment of the invention not shown, are provided with respective finning. According to the alternative embodiment of Figure 6, an exchanger 30 with tube bundle 31 , but otherwise conventional, comprises a plurality of m ultiport tubes 32, with mini- and/or m icro-channels, traversed by a refrigerating fluid. The ends of the tubes 31 are firmly fixed, by adhesive means, to two respective tube plates 33, 34. A two-shot resin may conveniently be employed as adhesive.

As an alternative to securing by adhesive means, the tubes 31 may be firm ly fixed to the tube plates 33, 34 by means of expanding.

The tube bundle 31 is housed in a tank 35, in which a primary thermal exchange fluid, for example water to be cooled or a compressed gas, circulates along a path 36 which extends from an inlet manifold 37 to an outlet manifold 38. The exchanger 30 comprises a plurality of dividing partitions 39, inside the tank 35 and orthogonal to the tubes 32, so as to render the path 36 predom inantly transverse with respect to the tubes 32. Via the sections of the path 36 comprised between adjacent dividing partitions 39, the primary thermal exchange fluid is conducted from one to the other of two sem i-cylindrical surfaces 35a, b, respectively lower and upper, which form as a whole the inner wall of the tank 35.

The present invention, through the arrangement of the plurality of passages with mini- and/or micro-channels, and of the interspaces 7, provides an exchanger devoid of finning, having a high thermal efficiency also when the primary working fluid is a liquid or a compressed gas.

The invention therefore solves the problem mentioned with reference to the prior art cited, at the same time obtaining numerous advantages. These include that of being able to use the m ultiport technology to produce an evaporator for refrigerating a liquid, with the optional possibility of reverse cycle operation, as a heat pump.

The use of the solution with a tube bundle provides the possibility of avoiding brazing operations, replacing them with more practical and econom ic operations of securing by adhesive means and/or expanding.

Claims

CLAI MS

1. A heat exchanger (1), with mini- and/or micro-channels, comprising a plurality of multiport tubes (2), extending between respective manifolds (3, 4) with a substantially longitudinal distribution, said multiport tubes (2) being mutually spaced by respective interspaces (7) and distributed so as to form opposed surfaces (5, 6) of the heat exchanger (1) substantially parallel to the longitudinal direction (x) of said tubes (2), characterized in that it comprises a plurality of dividers (8) disposed in said interspaces (7) and capable of forming a plurality of contiguous flow paths, through which a thermal exchange fluid is conducted from one to the other of said opposed surfaces (5, 6).

2. A heat exchanger (1) according to claim 1, wherein said dividers (8) are disposed transversely with respect to the longitudinal direction (X) of said multiport tubes (2).

3. A heat exchanger according to claim 1 or claim 2, wherein finning (13) is provided in at least one of said interspaces (7).

4. A heat exchanger (1) according to claim 1, wherein said dividers (8) are substantially parallel to the longitudinal direction (X) of said multiport tubes (2).

5. A heat exchanger (20) according to claim 4, wherein blocking means and counter-means for said surfaces (5, 6) are associated with said dividers

(21) so as to distribute the interspaces into respective outward and return channels (24a, b) that are contiguous and in sequence.

6. A heat exchanger (20) according to claim 5, wherein said means and counter-means comprise respective plates (22) integral with said dividers (21) and substantially orthogonal thereto.

7. A heat exchanger (30) according to one or more of the preceding claims, wherein said plurality of m ultiport tubes (32) is disposed in a tube bundle (31 ) .

8. A heat exchanger (30) according to claim 7, wherein said m ultiport tubes (32) are fixed, at the opposed ends, to two respective tube plates (33,

34) by adhesive means and/or expanding.

9. A heat exchanger (30) according to claim 8, wherein said securing by adhesive means is obtained by means of a two-shot resin.

10. A heat exchanger ( 1 , 20, 30) according to one or more of the preceding claims, wherein said thermal exchange fluid comprises water.

1 1 . A heat exchanger ( 1 , 20, 30) according to one or more of the preceding claims, wherein said thermal exchange fluid comprises a compressed gas.