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.
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
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.
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.
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:
Referring to
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
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.
A conventional U-type heat exchanger used in the comparative example has a structure shown in
The heat exchanger of the present invention used in Examples 1 to 7 has a U-type structure as shown in
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
Referring to
As shown in
In Example 4, the hole diameters of the third to ninth orifices 733 to 739 were substantially decreased, i.e., reduced to 2 mm, resulting in a great increase in the flow resistance for the first fluid 31 in the baffle tube 7. Referring to
Referring to
Referring to
Referring to
According to Examples 1 to 7, it is manifested that the site of the third to ninth orifices 733-739 exhibits greater influence to the flow distribution in the heat exchange tubes 6 than those of the first and second orifices 731, 732. When the size of the third to ninth orifices 733-739 become larger, the flow amounts of the seventh to ninth heat exchange tubes 67-69 are excessively increased. On the other hand, when the size of the third to ninth orifices 733-739 is relatively small, the flow distribution in the heat exchange tubes 6 becomes uniform. However, as shown in Example 6, when the size of the third to ninth orifices 733-739 is excessively reduced, the flow distribution in the heat exchange tubes 6 becomes uneven, i.e., the first and second heat exchange tubes 61, 62 have higher flow ratios.
In conclusion, with the baffle tube 7 in the inlet header tube 4, the vortex flow and eddy flow problems may be alleviated. According to
Additionally, the heat exchanger according to the present invention may be configured for application to a large scale heat exchange system such as a heat exchanger in a nuclear power plant, a small size heat exchanger disposed in a small scale electronic device, or any other heat exchange devices known to those skilled in the art.
While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.