U.S. patent application number 13/112949 was filed with the patent office on 2012-11-22 for heat exchanger.
This patent application is currently assigned to National Yunlin University of Science and Technology. Invention is credited to Ing-Youn Chen, Jhong-Syuan Tsai, Chi-Chuan Wang.
Application Number | 20120292004 13/112949 |
Document ID | / |
Family ID | 47174062 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120292004 |
Kind Code |
A1 |
Chen; Ing-Youn ; et
al. |
November 22, 2012 |
HEAT EXCHANGER
Abstract
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.
Inventors: |
Chen; Ing-Youn; (Yunlin
County, TW) ; Tsai; Jhong-Syuan; (Yunlin County,
TW) ; Wang; Chi-Chuan; (Hsinchu County, TW) |
Assignee: |
National Yunlin University of
Science and Technology
Yunlin
TW
|
Family ID: |
47174062 |
Appl. No.: |
13/112949 |
Filed: |
May 20, 2011 |
Current U.S.
Class: |
165/175 |
Current CPC
Class: |
F24S 10/742 20180501;
F28D 1/05316 20130101; F24S 80/30 20180501; Y02E 10/44 20130101;
F28F 9/0273 20130101 |
Class at
Publication: |
165/175 |
International
Class: |
F28F 9/02 20060101
F28F009/02 |
Claims
1. A heat exchanger comprising: an inlet header tube including
opposite first and second ends and an inner space formed between
said first and second ends; an outlet header tube substantially
parallel to said inlet header tube; a plurality of heat exchange
tubes transversely extending between and fluidly connected to said
inlet and outlet header tubes, each of said heat exchange tubes
having a connecting end connected to said inlet header tube; and a
baffle tube inserted into said inner space of said inlet header
tube from said first end to said second end, said baffle tube
having an open end proximate to said first end, a closed end
proximate to said second end, and a plurality of orifices disposed
between said open and closed ends to fluidly intercommunicate said
inner space of said inlet header tube and said baffle tube, each of
said orifices being disposed in alignment with said connecting end
of one of said heat exchange tubes.
2. The heat exchanger of claim 1, wherein said orifices of said
baffle tube include a first orifice disposed closest to said open
end of said baffle tube, and a second orifice disposed adjacent to
said first orifice oppositely of said open end, a remainder of said
orifices being disposed on one side of said second orifice opposite
to said first orifice, said first orifice being larger than said
second orifice, said second orifice being larger than each of said
remainder of said orifices.
3. The heat exchanger of claim 2, wherein an area of an interior
space of each of said heat exchange tubes is smaller than or equal
to an area of said first orifice and is larger than an area of said
second orifice.
4. The heat exchanger of claim 3, wherein said first, second, and
each of said remainder of said orifices have hole diameters that
are respectively 1-1.26, 0.73, and 0.5 times an inner diameter of
each of said heat exchange tubes.
5. The heat exchanger of claim 4, wherein said inner diameter of
each of said heat exchange tubes is 3 mm, and said hole diameters
of said first, second, and each of said remainder of said orifices
are respectively 3-3.8 mm, 2.2 mm, and 1.5 mm.
6. The heat exchanger of claim 5, wherein said hole diameter of
said first orifice is 3.8 mm.
7. The heat exchanger of claim 6, wherein said baffle tube has a
circular cross section with an inner diameter of 4 mm.
8. The heat exchanger of claim 7, wherein a distance of said
connecting end of said heat exchange tube from said first end of
said inlet header tube is 3.5 mm, a center-to-center distance
between adjacent ones of said orifices being 10 mm, a
center-to-center distance between adjacent ones of said heat
exchange tubes being 10 mm.
9. The heat exchanger of claim 1, further comprising an inflow tube
fluidly connected to said open end of said baffle tube.
10. The heat exchanger of claim 1, wherein said inlet header tube
has a square cross section.
11. The heat exchanger of claim 10, wherein said square cross
section of said inlet header tube has a width of 9 mm.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a heat exchanger, more
particularly to a heat exchanger that includes a baffle tube
inserted in an inlet header tube.
[0003] 2. Description of the Related Art
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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
[0009] 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.
[0010] 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
[0011] 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:
[0012] FIG. 1 is a perspective view of a conventional heat
exchanger;
[0013] FIG. 2 is a fragmentary enlarged sectional view of FIG.
1;
[0014] FIG. 3 shows simulation of velocity vector lines of the
conventional heat exchanger;
[0015] FIG. 4 is a plot illustrating flow ratios of the heat
exchange tubes of the conventional heat exchanger;
[0016] FIG. 5 is a perspective view of the preferred embodiment of
a heat exchanger according to the present invent ion
[0017] FIG. 6 is a fragmentary enlarged sectional view of FIG.
5;
[0018] FIG. 7 shows simulation of velocity vector lines of the
preferred embodiment according to the present invention;
[0019] FIG. 8 is a plot illustrating flow ratios of the heat
exchange tubes of Example 1;
[0020] FIG. 9 is a plot illustrating flow ratios of the heat
exchange tubes of Example 2;
[0021] FIG. 10 is a plot illustrating flow ratios of the heat
exchange tubes of Example 3;
[0022] FIG. 11 is a plot illustrating flow ratios of the heat
exchange tubes of Example 4;
[0023] FIG. 12 is a plot illustrating flow ratios of the heat
exchange tubes of Example 5;
[0024] FIG. 13 is a plot illustrating flow ratios of the heat
exchange tubes of Example 6; and
[0025] FIG. 14 is a plot illustrating flow ratios of the heat
exchange tubes of Example 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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 (.beta.) 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
[0036] 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.degree. C.
[0037] 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 (.beta.) 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
[0038] 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.degree. C.
[0039] 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 (.beta.) of the heat
exchange tubes 6 in each of Examples 1 to 7 are respectively shown
in FIGS. 8 to 14.
TABLE-US-00001 TABLE 1 Orifice Exam- Hole diameter of orifices (mm)
ple 731 732 733 734 735 736 737 738 739 1 4 3.7 3.2 3.2 3.2 3.2 3.2
3.2 3.2 2 4 3.5 3 3 3 3 3 3 3 3 3.7 3.2 2.8 2.8 2.8 2.8 2.8 2.8 2.8
4 3.5 3 2 2 2 2 2 2 2 5 3 2.2 1.5 1.5 1.5 1.5 1.5 1.5 1.5 6 2.8 2
1.2 1.2 1.2 1.2 1.2 1.2 1.2 7 3.8 2.2 1.5 1.5 1.5 1.5 1.5 1.5
1.5
[0040] Referring to FIG. 8, the flow distribution in the heat
exchange tubes 6 slightly decreases as the total flow rate (Q) of
the heat exchange tubes 6 increases. The first and second heat
exchange tubes 61, 62 have relatively higher flow ratios than those
of the third to seventh heat exchange tubes 63-67 because of the
relatively large hole diameters of the first and second orifices
731, 732, which allow a larger volume of the first fluid 31 to flow
therethrough and into the first and second heat exchange tubes 61,
62. Moreover, because of the effect of the moment of inertia, the
first fluid 31 has a higher flow rate near the eighth and ninth
orifices 738, 739, thereby resulting in relatively high flow ratios
in the eighth and ninth heat exchange tubes 68, 69.
[0041] As shown in FIGS. 9 and 10, Examples 2 and 3 have curve
profiles of flow ratio similar to that of Example 1. In these two
examples, the hole diameters of the orifices 73 were reduced that
resulted in an increase of the flow resistance of the first fluid
31 in the baffle tube 7. Because of the increased flow resistance
and the moment of inertia, in each of Example 2 and Example 3, the
flow ratio of the eighth heat exchange tube 738 is higher.
[0042] 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 FIG. 11, because
of the greatly increased flow resistance, the first fluid 31 tends
to flow into the fifth to seventh beat exchange tubes 735 to 737
rather than the eighth and ninth heat exchange tubes 738, 739.
Moreover, it is apparent that, in Example 4, the slope of the curve
from the fifth to ninth heat exchange tubes 735 to 739 is
relatively smaller than that in Examples 1 to 3.
[0043] Referring to FIG. 12, in Example 5, when the first orifice
731, the second orifice 732, and each of the remainder of the
orifices 733-739 respectively have hole diameters of 3 mm, 2.2 mm.,
and 1.5 mm, the first fluid 31 is evenly distributed in the nine
heat exchange tubes 6. In other words, the differences in the flow
ratios among the nine heat exchange tubes 731-739 become relatively
small.
[0044] Referring to FIG. 13, the flow ratios of the first and
second heat exchange tubes 61, 62 are higher than those of the
remainder of the heat exchange tubes 63-69 in Example 6. Since the
hole diameters of the third to ninth orifices 733-739 were
excessively decreased to 1.2 mm, the flow resistance adjacent to
the third to ninth orifices 737-739 is extremely high that causes
the first fluid 31 to flow into the first and second heat exchange
tubes 61, 62 through the first and second orifices 731, 732 where
the flow resistance is relatively low.
[0045] Referring to FIG. 14, the flow ratios of the heat exchange
tubes 6 in Example 7 are similar, which indicates a substantially
uniform flow distribution in the heat exchange tubes 6. It is
apparent from Examples 5 and 7 that the optimum conditions for the
hole diameters of the orifices 73 are respectively 3-3.8 mm for the
first orifice 731, 2.2 mm for the second orifice 732, and 1.5 mm
for each of the remainder of the orifices 733-739. In other words,
the hole diameters of the first, second, and each of the remainder
of the orifices 731, 732, 733-739, are respectively 1-1.26, 0.73,
and 0.5 times the inner diameter of each of the heat exchange tubes
6, i.e., 3 mm.
[0046] 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.
[0047] 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 FIGS. 8 to 14, each of the heat exchange tubes 6 has a
flow ratio larger than 7%, which is much larger than that of the
conventional heat exchanger in Comparative Example (the lowest one
is 2%). Moreover, the flow distribution in the heat exchange tubes
6 of the present invention can be controlled to be uniform by
controlling the sixes of the orifices 73, thereby improving the
heat exchange efficiency of the heat exchanger.
[0048] 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.
[0049] 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.
* * * * *