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Heat exchanger

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20120292004 patent thumbnailZoom

Heat exchanger


A heat exchanger includes: an inlet header tube including opposite first and second ends and an inner space formed between the first and second ends; an outlet header tube parallel to the inlet header tube; a plurality of heat exchange tubes transversely extending between and fluidly connected to the inlet and outlet header tubes, each of the heat exchange tubes having a connecting end connected to the inlet header tube; and a baffle tube inserted into the inner space of the inlet header tube. The baffle tube has an open end proximate to the first end, a closed end proximate to the second end, and a plurality of orifices disposed between the open and closed ends to fluidly intercommunicate the inner space of the inlet header tube and the baffle tube. Each of the orifices is disposed in alignment with the connecting end of one of the heat exchange tubes.

Browse recent National Yunlin University Of Science And Technology patents - Yunlin, TW
Inventors: Ing-Youn Chen, Jhong-Syuan Tsai, Chi-Chuan Wang
USPTO Applicaton #: #20120292004 - Class: 165175 (USPTO) - 11/22/12 - Class 165 
Heat Exchange > Side-by-side Tubular Structures Or Tube Sections >With Manifold Type Header Or Header Plate >Inlet And Outlet Header Means

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The Patent Description & Claims data below is from USPTO Patent Application 20120292004, Heat exchanger.

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a heat exchanger, more particularly to a heat exchanger that includes a baffle tube inserted in an inlet header tube.

2. Description of the Related Art

Heat exchangers are widely applied to various devices such as condensers, evaporators, boiler furnaces, heat collectors using solar panels, heat radiators of nuclear reactors or electronic equipments, etc. The heat transfer efficiency of a heat exchanger is generally improved by an increase in the heat transfer area of the heat exchanger.

A conventional heat exchanger using gas to dissipate heat has a relatively low heat exchange efficiency and cannot meet current commercial demands. Therefore, it is desired in the art to increase the heat exchange efficiency of a heat exchanger by utilizing liquid to dissipate heat.

FIGS. 1 and 2 show a conventional heat exchanger that is usually used in an electronic equipment or a solar energy water heater. The heat exchanger includes an inflow tube 20, an inlet header tube 21 having an open end 211 fluidly connected to the inflow tube 20, an outlet header tube 22 parallel to the inlet header tube 21, and a plurality of heat exchange tubes 23 transversely extending between and fluidly connected to the inlet and outlet header tubes 21, 22. In use, a first fluid 11 is allowed to flow into the inlet header tube 21 through the inflow tube 20 and is then distributed among the heat exchange tubes 23. A second fluid 12 having a temperature higher or lower than that of the first fluid 11 is allowed to flow externally around the heat exchange tubes 23 so as to transfer heat from the second fluid 12 to the first fluid 11 or vice versa.

Generally, the cross section of the inflow tube 20 is smaller than that of the inlet header tube 21 such that let flow is induced near the open end 211 of the inlet header tube 21. As shown in FIG. 3, because of the inlet jet stream, vortex flow and eddy flow are generated at the open end 211 and even in first and second ones of the heat exchange tubes 231, 232 that are closest to the open end 211, resulting in relatively low flow amounts in the first and second heat exchange tubes 231, 232 compared to that in the remainder of the heat exchange tubes 23. In other words, the flow distribution among the heat exchange tubes 23 is uneven, thereby reducing the heat exchange efficiency of the conventional heat exchanger.

The aforesaid drawbacks may be overcome by moving the heat exchange tubes 23 away from the open end 211 of the inlet header tube 21. However, such an arrangement may result in an increase in the length of the inlet header tube 21, which makes the heat exchanger inapplicable for a small scale device.

SUMMARY

OF THE INVENTION

Therefore, the object of the present invention is to provide a heat exchanger that can overcome the vortex flow and eddy flow problems encountered in the prior art.

According to the present invention, a heat exchanger comprises: an inlet header tube including opposite first and second ends and an inner space formed between the first and second ends; an out 1 et header tube substantially parallel to the inlet header tube; a plurality of heat exchange tubes transversely extending between and fluidly connected to the inlet and outlet header tubes, each of the heat exchange tubes having a connecting end connected to the inlet header tube; and a baffle tube inserted into the inner space of the inlet header tube from the first end to the second end, the baffle tube having an open end proximate to the first end, a closed end proximate to the second end, and a plurality of orifices disposed between the open and closed ends to fluidly intercommunicate the inner space of the inlet header tube and the baffle tube, each of the orifices being disposed in alignment with the connecting end of one of the heat exchange tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invent ion will become apparent in the following detailed description of the preferred embodiments of the invention, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a conventional heat exchanger;

FIG. 2 is a fragmentary enlarged sectional view of FIG. 1;

FIG. 3 shows simulation of velocity vector lines of the conventional heat exchanger;

FIG. 4 is a plot illustrating flow ratios of the heat exchange tubes of the conventional heat exchanger;

FIG. 5 is a perspective view of the preferred embodiment of a heat exchanger according to the present invent ion

FIG. 6 is a fragmentary enlarged sectional view of FIG. 5;

FIG. 7 shows simulation of velocity vector lines of the preferred embodiment according to the present invention;

FIG. 8 is a plot illustrating flow ratios of the heat exchange tubes of Example 1;

FIG. 9 is a plot illustrating flow ratios of the heat exchange tubes of Example 2;

FIG. 10 is a plot illustrating flow ratios of the heat exchange tubes of Example 3;

FIG. 11 is a plot illustrating flow ratios of the heat exchange tubes of Example 4;

FIG. 12 is a plot illustrating flow ratios of the heat exchange tubes of Example 5;

FIG. 13 is a plot illustrating flow ratios of the heat exchange tubes of Example 6; and

FIG. 14 is a plot illustrating flow ratios of the heat exchange tubes of Example 7.

DETAILED DESCRIPTION

OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 5 and 6, the preferred embodiment of a heat exchanger according to the present invention is used for conducting heat exchange between a first fluid 31 and a second fluid 32. The heat exchanger includes: an inlet header tube 4 having opposite first and second ends 41, 42, and an inner space 43 formed between the first and second ends 41, 42; an outlet header tube 5 substantially parallel to the inlet header tube 4; a plurality of heat exchange tubes 6 (nine in the embodiment) transversely extending between and fluidly connected to the inlet and outlet header tubes 4, 5; a baffle tube 7 inserted into the inner space 43 of the inlet header tube 4 from the first end 41 to the second end 42; and inflow and outflow tubes 33, 34.

Each of the heat exchange tubes 6 has a connecting end 60 connected to the inlet header tube 4. The baffle tube 7 has an open end 71 proximate to the first end 41 of the inlet header tube 4, a closed end 72 proximate to the second end 42 of the inlet header tube 4, and a plurality of orifices 73 (nine in the embodiment) disposed between the open and closed ends 71, 72 to fluidly intercommunicate the inner space 43 of the inlet header tube 4 and the baffle tube 7. Each of the orifices 73 is disposed in alignment with the connecting end 60 of one of the heat exchange tubes 6.

The inflow and outflow tubes 33, 34 are respectively fluidly connected to the open end 71 of the baffle tube 7 and the outlet header tube 5 such that a fluid pathway for the first fluid 31 flowing from the inflow tube 33 to the outflow tube 34 through the inlet header tube 4, the heat exchange tubes 6, and the outlet header tube 3 is formed. The second fluid 32 is allowed to externally flow around the heat exchange tubes 6 so as to exchange heat with the first fluid 31 via the heat exchange tubes 6.

In this preferred embodiment, the fluid pathway is classified as a U-type fluid pathway in that the inflow and outflow tubes 33, 34 are disposed at the same side with respect to the heat exchange tubes 6. Alternatively, the inflow and outflow tubes 33, 34 may be disposed at opposite sides with respect to the heat exchange tubes 6 such that the fluid pathway is classified as Z-type.

Preferably, radiator fins (not shown) may be disposed between and connected to the heat exchange tubes 6 to improve the heat exchange efficiency between the first and second fluids 31, 32.

According to the present invention, due to the design of the baffle tube 7 that is inserted inside the inlet header tube 4, no eddy flow is induced in the inlet header tube 4. As shown in FIG. 7, the first fluid 31 is allowed to flow into the baffle tube 7 and subsequently flows into the inner space 43 of the inlet header tube 4 through the orifices 73. A portion of the first fluid 31 directly flows into the heat exchange tubes 6, and another portion of the first fluid 31 which does not directly flow into the heat exchange tubes 6 circulates around the baffle tube 7 and eventually flows into the heat exchange tubes 6. Because no vortex flow or eddy flow is generated in the inlet header tube 4, the flow distribution of the first fluid 31 in the heat exchange tubes 6 becomes relatively uniform as compared to that of the conventional heat exchanger (see FIG. 3), thereby improving the heat-exchange efficiency of the heat exchanger. In this embodiment, the inflow tube 33 and the baffle tube 7 have the same cross sections, i.e., 4 mm in diameter.

Preferably, the inlet and outlet header tubes 4, 5 respectively have a square cross section. Alternatively, the cross sections of the inlet and outlet header tubes 4, 5 may be in the form of any shape.

For the sake of clarity, the nine heat exchange tubes 6 and the nine orifices 73 from the open end 71 to the closed end 72 of the baffle tube 7 are respectively denoted by reference numerals 61 to 69 and 731 to 739. The first heat exchange tube 61 and the first orifice 731 are disposed closest to the open end 71 of the baffle tube 7, and the second heat exchange tube 62 and the second orifice 732 are respectively disposed adjacent to the first heat exchange tube 61 and the first orifice 731 opposite to the open end 71. The remainder of the heat exchange tubes 63, 64, 65, 66, 67, 68, and 69, and the remainder of the orifices 733, 734, 735, 736, 737, 738, and 739 are respectively disposed on one side of the second heat exchange tube 62 and the second orifices 732 that is opposite to the first heat exchange tube 61 and the first orifice 731. It should be noted that the number of the heat exchange tubes 6 and that of the orifices 73 are the same, and are not limited to nine in other embodiments of this invention.

Preferably, in order to further overcome the drawbacks associated with the prior art that the flow amounts of the first and second heat exchange tubes 61, 62 are relatively low, in this embodiment, the first orifice 731 is larger than the second orifice 732, and the second orifice 732 is larger than each of the remainder of the orifices 733-739. Moreover, in order to avoid accumulation of excessive pressure in the baffle tube 7 that may adversely influence the inflow of the first fluid 33, an area of an interior space of each of the heat exchange tubes 6 is preferably designed to be smaller than or equal to an area of the first orifice 731 and to be larger than an area of the second orifice 732.

The performances of a conventional heat exchanger and the preferred embodiment of the heat exchanger according to the present invention were assessed by a numerical simulation using EFD.lab software as described below. The flow ratio (β) of each of the heat exchange tubes 6 of the heat exchangers was calculated by the EFD.lab software and is defined as a ratio of the flow rate in one heat exchange tube to the total flow rate (Q) in all of the heat exchange tubes 6.

COMPARATIVE EXAMPLE

A conventional U-type heat exchanger used in the comparative example has a structure shown in FIG. 1, in which the inlet and outlet header tubes 21, 22 have a square cross section with a width of 9 mm, each of the nine heat exchange tubes 23 has an inner diameter of 3 mm, and the inflow tube 20 has an inner diameter of 4 mm. A distance of an opening of the heat exchange tube 231 from the open end 211 of the inlet header rube 21 is 3.5 mm. The first fluid 11 is water having a temperature of 25° C.

FIG. 3 shows the simulation plot of velocity vector lines of the convent tonal heat exchanger. Inlet jet stream and vortex flow are generated at the open end 211 of the inlet header tube 21 near the first and second heat exchange tubes 231, 232, and even in the first heat exchange tube 231. The inlet jet stream and vortex flow result in relatively low flow amounts in the first and second heat exchange tubes 231, 232. According to FIG. 4, when the total flow rate (Q) is 1-4 L/min, the flow ratio (β) of the first heat exchange tube 231 is smaller than 6% and is quite lower than the flow ratios of the remainder of the heat exchange tubes 23, which indicates an extremely uneven flow distribution in the heat exchange tubes 23 of the conventional heat exchanger.

Examples 1 to 7

The heat exchanger of the present invention used in Examples 1 to 7 has a U-type structure as shown in FIG. 5, in which the inlet and outlet header tubes 4, 5 respectively have a square cross section with a width of 9 mm, each of the heat exchange tubes 6 has a circular cross section with an inner diameter of 3 mm, the baffle tube 7 has a circular cross section with an outer diameter of 6 mm and an inner diameter of 4 mm, and each of the orifices 73 of the baffle tube 7 has a circular shape. A distance of the connecting end 60 of the first heat exchange tube 61 from the first end 41 of the inlet header tube A is 3.5 mm, a center-to-center distance between two adjacent orifices 73 is 10 mm, and a center-to-center distance between two adjacent heat exchange tubes 6 is 10 mm. It should be noted that the inflow tube 31 has the same cross section as that of the baffle tube 7 in Examples 1 to 7. The first fluid 31 is water having a temperature of 25° C.

In Examples 1 to 7, each of the orifices 73 has a hole diameter that is varied (see Table 1) so as to verify the influence of the size of the orifices 73 on the flow distribution in the heat exchange tubes 6. For each of Examples 1 to 7, the total flow rate (Q) varied from 1 to 4 L/min. The flow ratios (β) of the heat exchange tubes 6 in each of Examples 1 to 7 are respectively shown in FIGS. 8 to 14.



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stats Patent Info
Application #
US 20120292004 A1
Publish Date
11/22/2012
Document #
13112949
File Date
05/20/2011
USPTO Class
165175
Other USPTO Classes
International Class
28F9/02
Drawings
15



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