FIELD OF THE INVENTION

[001] The presently disclosed subject matter is in the field of heat exchangers, in particular tube heat exchangers, and a flow directing insert therefor.

BACKGROUND OF THE INVENTION

[002] Effective and efficient production of hot water has become increasingly important, particularly since non-renewal resources are often used to heat water. Heat pumps are well known for heating fluids and include a vaporizer where a refrigerant is vaporized typically by heat from air blown over vaporizer coils; a heat exchanger or condenser, where relatively cool fluid is heated upon thermal contact with the relatively hot refrigerant, the refrigerant condensing in the condenser and passing that heat energy to the fluid to be heated. Heat pumps are efficient because about two thirds of the energy comes from the air, which is used to vaporize the liquid refrigerant in the vaporizer and about one third of the energy is required to compress the refrigerant in the gaseous state. The energy used to condense the gaseous refrigerant is typically electrical energy while the energy to vaporize the liquid comes from the thermal energy in the ambient air.

[003] Fig. 1 shows an exemplary prior art tube bundle 100 for a heat exchanger. Bundle 100 includes a series of tubes 102 arranged in rows and columns. A fluid, such as air, is flowed between the tubes.

SUMMARY OF THE INVENTION

[004] The present presently disclosed subject matter relates to a tube bundle for heat exchangers; and a flow-directing insert therefor. [005] In accordance with one aspect of the presently disclosed subject matter, there is provided a heat exchanger tube-bundle of tube rows and tube columns, including a flow-directing insert disposed between tube rows of the tubebundle. The tube bundle for the heat exchanger includes at least two rows of heat exchanger tubes; and at least one fluid-flow directing insert disposed between the at least two rows of heat exchanger tubes. The tubes are non-finned and oriented in an in-line configuration; and each of the inserts has a front wall, and upper and lower walls, which are shaped in correspondence to the heat exchanger tubes, to form one or more fluid flow passages.

[006] In some examples, the front wall of the insert is upwardly angled with respect to the vertical. In some examples, the tubes have an outer surface that is grooved or roughened. In some examples, the tube-bundle includes solid connections conductively connecting portions of the tubes and the inserts. In some examples, each tube column is formed in a one-piece serpentine configuration of a serpentine tube. In some examples, the insert and the tubes are non-uniformly distanced whereby the cross-sectional area of the fluid flow passages is non-uniform. In some examples, different columns of tubes have a different diameter and/or shape. In some examples, the front wall of the insert has a solar absorbing material. In some examples, the solar absorbing material is a black coating.

[007] In accordance with another aspect of the presently disclosed subject matter, there is provided a flow-directing insert for a heat-exchanger tube bundle having non-finned tubes oriented in an in-line configuration. The insert includes a front wall; an upper wall; and a lower wall. The upper and lower walls of the insert are shaped in correspondence to the heat exchanger tubes, thereby forming a fluid flow passage based on the shape of the upper and lower walls of the insert.

[008] In some examples, the front wall of the insert is upwardly angled with respect to the vertical. In some examples, the insert includes solid connections to allow conductive connection to the tubes of the tube bundle. In some examples, the insert is configured to form a non-uniform distance between the insert and the tubes whereby the cross-sectional area of the fluid flow passage is non-uniform. In some examples, the front wall of the insert has a solar absorbing material. In some examples, the solar absorbing material is a black coating.

[009] In accordance with yet another aspect of the presently disclosed subject matter, there is provided an inter-tube row, flow directing, insert for a nonfinned tube heat exchanger tube-bundle.

BRIEF DESCRIPTION OF DRAWINGS

[010] The invention may be more clearly understood upon reading of the following detailed description of non-limiting exemplary embodiments thereof, with reference to the following drawings, in which:

[011] Fig. 1 is a perspective view of an exemplary prior art tube bundle for a heat exchanger.

[012] Figs. 2-4 are a perspective view; a cross-sectional side view; and a cross-sectional end view, respectively, of a tube bundle with a flow-directing tubebundle insert, in accordance with one example of the presently disclosed subject matter.

[013] Fig. 5 is a side view of an exemplary flow-directing tube-bundle insert, in accordance with one example of the presently disclosed subject matter.

[014] Fig. 6 is a cross-sectional view of an exemplary line of tubes (a front tube and subsequent tubes), in accordance with examples of the presently disclosed subject matter.

[015] Fig. 7 is a cross-sectional view of an exemplary insert-tube arrangement, in accordance with examples of the presently disclosed subject matter.

DETAILED DESCRIPTION OF EMBODIMENTS [016] The invention may be more clearly understood upon reading of the following detailed description of non-limiting exemplary embodiments thereof, with reference to the drawings.

[017] The following detailed description of embodiments of the invention refers to the accompanying drawings referred to above. Dimensions of components and features shown in the figures are chosen for convenience or clarity of presentation and are not necessarily shown to scale. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.

[018] Illustrative embodiments of the invention are described below. In the interest of clarity, not all features/components of an actual implementation are necessarily described.

[019] Fig. 2 shows a tube bundle 20, in accordance with one example of the presently disclosed subject matter, illustrated with two in-line tube rows of tubes 22, illustrated as a sixteen “highVcolumn configuration. Fig. 3 shows a cross-section of a portion of the side of tube bundle 20, with columns of only a few “high” configuration; and Fig. 4 shows an end cross-section view of Fig. 3.

[020] The rows of tubes 22 of tube bundle 20 have an in-line arrangement I configuration; in other words, exemplified in Fig. 4, as having an upper tube row of tubes 24a and 26a; an intermediate tube row of tubes 24b and 26b; and a lower tube row of tubes 24c and 25c. Tube bundle 20 may include additional tube rows, and any suitable number of tubes in each row). The three tube rows and two tube “columns” are only illustrative/exemplary - the number of tubes is not limited. Intermediate to each tube row are a series of fluid flow-directing tube-bundle inserts 28. Tube bundle 20 typically has a fan (not illustrated) on the rear side (left side in Fig. 4) to draw air over tubes 22, i.e. draw air between the tube-rows thereof - in fluid/air passages 40, noted below.

[021] Fig. 5 illustrates an exemplary design of flow-directing insert 28 including an upper wall 34, a lower wall 36, and a front wall 38 - the walls having a thickness T. As best visualized in Fig. 4, upper wall 34 and lower wall 36 are shaped to correspond to tubes 22 adjacent thereto. This correspondence provides a fluid flow passage 40 that may be generally uniform in cross-sectional area, as illustrated in Fig. 4, and that is narrow relative to (narrower than) the intertube row space without inserts 28. However, insert 28 can be designed wherein the correspondence provides a non-uniform flow passage, for example, having a larger (or smaller, or even non-linear) cross sectional flow area at the front portion of passage 40 compared to the rear portion of the passage. Such deviations from a uniform cross-sectional flow area may be advantageous depending on the change in temperature of the fluid as the fluid exchanges heat while passing over the tubes. It should be understood that the fluid-flow area of passages 40 are smaller than the fluid flow area without inserts 28.

[022] Front wall 38 of insert 28 serves to block fluid, whereby the fluid is restricted to only flow in passages 40 to thereby control/limit the cross-sectional fluid flow area. As such, heat exchange between the fluid/air and tubes 22 is improved. If tube bundle 20 is used as part of an evaporator, the outer surface of front walls 38 of each insert 28 may be coated with a solar absorbing material - e.g. black colored; and the front walls may be angled to better face toward the sun, as illustrated in Fig. 2, Fig. 4, and Fig. 7. Obviously, the evaporator as a whole may be angled so that front walls 38 better face toward the sun (e.g., at a 30 to 60 degree angle).

[023] This angling of front wall 38 of insert 28 is with respect to the vertical so that the front wall faces more upward than horizontal. The solar absorbing material (e.g. black coating) increases the heat energy at front walls 38. That energy is thus transferred to walls 34 and 36; onward to the fluid in passages 40; and ultimately to tubes 22 and the fluid therein.

[024] Best seen in Fig. 4, inserts at the top and bottom may be “partial” (e.g. “half”) inserts, identified as top insert 28t and bottom insert 28b.

[025] Fig. 6 illustrates an option where tubes 22 of tube rows subsequent to (downstream of) the “front” tube rows 24, are “smaller” than the tubes in the front tube row. In this context, “smaller” means that when viewed from the fluid flow direction, the subsequent tubes 26a, 26b, and 26c appear smaller. In fact, tubes 22 of subsequent tube rows may have varied shapes / geometries, typically for increased heat transfer area, for example in the form of an oval tube 60 (with their longer dimension in the fluid flow direction. According to another example, tubes 22 in a further subsequent tube row (e.g., tube row 27) may have tubes 29 with projections 62.

[026] As known, tubes 22 may be grooved/roughened on their inner walls to improve heat transfer. It is also known to groove/roughen the outer surface of heat exchanger tubes, although that may not be convenient with all prior art heat exchanger/tube bundle designs. However, the designs described herein may be conveniently used with tubes having grooved/roughened outer surfaces.

[027] In the case where tubes 22 are round, the outer grooves/bumps could be helical (i.e., have a spiral configuration; not in a straight/cylindrical line) to further enlarge the heat transfer surface area.

[028] Fig. 7 shows an exemplary optional arrangement between insert 28 and tubes 22 wherein in certain locations there are solid connections 70 between limited portions of the insert and the tubes for improved heat exchange due to the conduction. Solid connections 70 provide a conductive contact at those limited portions between inserts 28 and tubes 22. Connections 70 may be a part of insert 28, to allow the conductive connection with tubes 22. Connections 70 are typically “downstream” of the air-flow inlet (i.e. not adjacent front wall 38; in other words tubes 26 or subsequent tubes). In such subsequent tubes 26 (and/or 27), the air/fluid is colder than in the front of tube bundle 20, which receives fresh “warm” air. As the air is cooled, its density/volume is smaller so the flowrate may be kept more uniform.

[029] It can be noted that an advantage of using a non-finned tube is that each tube column can be formed of one tube by bending in a serpentine configuration rather than requiring welding/soldering of end U-shaped turn- about/arch at the ends of linear tubes. In other words, tubes 24a, 24b, and 24c (the front “tube column”) can be made of one tube; a one-piece configuration - the same for tubes 26a, 26b, and 26c (the second “tube column”).

[030] It should be understood that the above description is merely exemplary and that there are various embodiments of the present invention that may be devised, mutatis mutandis, and that the features described in the abovedescribed embodiments, and those not described herein, may be used separately or in any suitable combination; and the invention can be devised in accordance with embodiments not necessarily described above.