MIN TAE-SIK (KR)
| JP2004108641A | 2004-04-08 | |||
| JP2004085142A | 2004-03-18 | |||
| KR970047730A | 1997-07-26 | |||
| JPH0320577A | 1991-01-29 |
| A heat exchanger with a combination of a laminar flow type and a turbulent flow type comprising a plurality of tubes having a rectangular cross-section and installed adjacent to each other so that an exhaust gas passes through passages between the tubes to exchange heat, characterized in that a laminar flow heat exchange part is installed at an inlet port through which the exhaust gas is introduced, and a turbulent flow heat exchange part is installed at an outlet port through which the exhaust gas is discharged. |
| The heat exchanger according to claim 1, wherein the laminar flow heat exchange part is constituted by flat surfaces of the tubes through which the exhaust gas passes. |
| The heat exchanger according to claim 1, wherein the turbulent flow heat exchange part is constituted by prominence and depression surfaces of the tubes through which the exhaust gas passes. |
| The heat exchanger according to claim 1, wherein a boundary between the laminar flow heat exchange part and the turbulent flow heat exchange part is a point at which a temperature boundary layer is formed as the exhaust gas passes therethrough. |
The present invention relates to a heat exchanger with a combination of a laminar flow type and a turbulent flow type, and more particularly, to a heat exchanger with a combination of a laminar flow type and a turbulent flow type capable of reducing an exhaust resistance and increasing heat transfer efficiency.
Generally, a heating apparatus includes a heat exchanger, in which an exhaust gas generated by fuel combustion is heat-exchanged with heating water, so that the heating water can be used to heat a building or used as warm water for domestic use.
FIG. 1 is a schematic view of a conventional heat exchanger including fins and tubes.
The heat exchanger shown in FIG. 1 includes tubes 11, 12 and 13 through which heating water flows, and fins 14 projecting from surfaces of the tubes 11, 12 and 13.
While such heat exchangers have been widely used, a large amount of material and a large number of processes are required, thus increasing the manufacturing cost.
In order to solve the problems, two kinds of heat exchangers having no fin have been proposed and are currently in use. The non-fin type heat exchangers use characteristics of laminar flow or turbulent flow, which are flow characteristics of an exhaust gas.
FIG. 2 is a schematic view of a heat exchanger using characteristics of laminar flow.
The heat exchanger shown in FIG. 2 includes tubes 21, 22 and 23 having a rectangular shape without any fin. The tubes are disposed at predetermined intervals, for example, 1mm or less, and have a height of 36mm or less.
Such a heat exchanger has an advantage in that heat transfer efficiency is increased since an exhaust gas passing through spaces between the tubes 21, 22 and 23 forms no temperature boundary layers.
FIGS. 3, 4, 5 and 6 illustrate the heat exchanger using the above theory.
FIGS. 3 and 4 are a perspective view and a side view of a conventional laminar type cylindrical heat exchanger having no fin, respectively, FIG. 5 is a cross-sectional view of a conventional planar laminar flow heat exchanger having no fin, and FIG. 6 is an exploded perspective view of the heat exchanger shown in FIG. 5.
The heat exchanger shown in FIGS. 3 and 4 includes a tube 31 formed with a heating water inlet port 32 and a heating water discharge port 33 at both ends thereof, having a flat cross-section, and wound in a spiral shape, which is appropriate for a cylindrical burner.
In addition, the heat exchanger shown in FIG. 5 is appropriate for a flat burner. A plurality of tubes 41 having a straight flat shape are installed in parallel, and heating water introduced through the heating water inlet port 42 passes through the plurality of tubes 41 and is supplied into a place in need of heating through a heating water discharge port 43.
However, since the non-fin type heat exchanger using laminar flow shown in FIGS. 3 to 6 has a small gap between the heat exchange tubes 31 or 41, an exhaust resistance is largely increased, and limitation in height of the heat exchange tubes 31 or 41 makes it difficult to fabricate a heat exchanger having a large capacity.
Hereinafter, a heat exchanger having turbulent flow characteristics will be described with reference to FIGS. 7 to 10.
FIG. 7 illustrates a concept of a turbulent flow heat exchanger, FIG. 8 is a perspective view of a conventional non-fin turbulent flow heat exchanger, FIG. 9 is a perspective view of a boiler employing the heat exchanger shown in FIG. 8, and FIG. 10 is a perspective view of another conventional non-fin turbulent flow heat exchanger.
The turbulent flow heat exchanger shown in FIG. 7 has prominences and depressions formed at surfaces 51 and 52 thereof to generate turbulent flow of an exhaust gas G, thereby improving heat transfer efficiency. Reference character W designates heating water.
The heat exchanger shown in FIGS. 8 and 9 has a tubular shape. A burner 63 is installed at an upper part of the heat exchanger, and a plurality of smoke tubes 61 are installed under the burner 63 at predetermined intervals such that a space between the smoke tubes 61 functions as a passage through which an exhaust gas passes.
The smoke tubes 61 have a flat tube shape, surfaces of which have prominences and depressions 62.
While the heat exchanger having the above-mentioned structure can remarkably reduce an exhaust resistance, since the above-mentioned heat exchanger has substantially the same shape as the heat exchanger used in the tubular boiler, a large amount of materials must be non-economically consumed.
Meanwhile, the heat exchanger shown in FIG. 10 is a flat heat exchanger 71, in which metal thin plates 71b and 71c having prominences and depressions 71a are brazed and coupled to the surface of the heat exchanger. While the heat exchanger has good heat transfer efficiency, complex manufacturing processes thereof are non-economical.
In order to solve the foregoing and/or other problems, it is an object of the present invention to provide a heat exchanger having prominences and depressions formed on tube surfaces thereof, without any fin, and employing a combination structure of a laminar flow type and a turbulent flow type to decrease an exhaust resistance and increase heat transfer efficiency.
One aspect of the present invention provides a heat exchanger including a plurality of tubes having a rectangular cross-section and installed adjacent to each other so that an exhaust gas passes through passages between the tubes to exchange heat, characterized in that a laminar flow heat exchange part is installed at an inlet port through which the exhaust gas is introduced, and a turbulent flow heat exchange part is installed at an outlet port through which the exhaust gas is discharged.
In this case, the laminar flow heat exchange part may be constituted by flat surfaces of the tubes through which the exhaust gas passes.
In addition, the turbulent flow heat exchange part may be constituted by prominence and depression surfaces of the tubes through which the exhaust gas passes.
Further, a boundary between the laminar flow heat exchange part and the turbulent flow heat exchange part may be a point at which a temperature boundary layer is formed as the exhaust gas passes therethrough.
According to the present invention, as prominences and depressions are formed at a portion of surfaces of tubes constituting a non-fin laminar flow heat exchanger, it is possible to provide a heat exchanger capable of providing good heat exchange performance, simple structure, and low manufacturing cost.
The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a schematic view of a conventional heat exchanger constituted by a tube and fins;
FIG. 2 is a schematic view of a conventional heat exchanger using laminar flow characteristics;
FIGS. 3 and 4 are a perspective view and a side view of a conventional non-fin cylindrical laminar flow heat exchanger, respectively;
FIG. 5 is a cross-sectional view of a conventional non-fin flat laminar flow heat exchanger;
FIG. 6 is an exploded perspective view of the heat exchanger shown in FIG. 5;
FIG. 7 illustrates a concept of a conventional turbulent flow heat exchanger;
FIG. 8 is a perspective view of a conventional non-fin turbulent flow heat exchanger;
FIG. 9 is a schematic perspective view of a boiler employing the heat exchanger shown in FIG. 8;
FIG. 10 is perspective view of another conventional non-fin turbulent flow heat exchanger;
FIG. 11 is a graph showing the relationship of an exhaust resistance and a gap between tubes of a non-fin laminar flow heat exchanger;
FIG. 12 is a graph showing the relationship of a distance to a position at which a temperature boundary layer is formed, and a gap between tubes of a non-fin laminar flow heat exchanger;
FIG. 13 illustrates a speed boundary layer;
FIG. 14 illustrates a temperature boundary layer; and
FIG. 15 is a schematic view of a heat exchanger with a combination of a laminar flow type and a turbulent flow type in accordance with an exemplary embodiment of the present invention.
Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
FIG. 11 is a graph showing the relationship of an exhaust resistance and a gap between tubes of a non-fin laminar flow heat exchanger, and FIG. 12 is a graph showing the relationship of a distance to a position at which a temperature boundary layer is formed, and a gap between tubes of a non-fin laminar flow heat exchanger.
As shown in FIG. 11, when a gap between tubes constituting the heat exchanger is increased, an exhaust resistance is reduced, and when the gap between the tubes is reduced, the exhaust resistance is increased.
Therefore, in order to reduce the exhaust resistance of a non-fin laminar flow heat exchanger, it is necessary to expand the gap between the tubes.
However, as shown in FIG. 12, when the gap between the tubes is increased, a temperature boundary layer may be rapidly formed, thereby decreasing heat exchange performance.
The above relationship will be described in detail with reference to FIGS. 13 and 14.
FIG. 13 is a view showing a speed boundary layer, and FIG. 14 is a view showing a temperature boundary layer.
Provided that a hot fluid moves in a direction parallel to a wide thin solid plate at a speed of U 8 , when a temperature of the fluid at this time is T 8 , as shown in FIG. 13, a speed of the fluid in contact with the plate becomes 0, and a speed of the fluid far from the plate is increased up to U 8 .
At this time, positions lower than the speed U 8 correspond to oblique lines of FIG. 13. That is, a speed boundary layer starts from an end of the plate.
Meanwhile, the temperature of the fluid in contact with the plate is maintained at T 8 from a start end of the plate at which the fluid enters to a certain section A, and then the temperature of the fluid becomes T 0 after the certain section. The point at which the fluid temperature T 0 starts is referred to as a boundary layer forming point (Point B of FIG. 14).
After the boundary layer forming point, the temperature of the fluid in contact with the plate becomes T 0 , and the temperature of the fluid far from the plate is increased up to T 8 . In this case, positions lower than the fluid temperature correspond to oblique lines of FIG. 13.
Therefore, when the gap between the tubes of the non-fin laminar flow heat exchanger is increased, the exhaust resistance is reduced, but a temperature boundary layer is rapidly formed, thereby decreasing heat transfer efficiency.
Such a problem can be overcome by the structure of the heat exchanger shown in FIG. 15.
FIG. 15 is a schematic view of a heat exchanger with a combination of a laminar flow type and a turbulent flow type in accordance with an exemplary embodiment of the present invention.
Referring to FIG. 15, the heat exchanger 100 includes a plurality of tubes 110, 120 and 130 constituting a non-fin laminar flow heat exchanger and installed at predetermined gaps a.
The tubes 110, 120 and 130 include a laminar flow heat exchange part (C section) having straight structures into which an exhaust gas is introduced, with reference to a point (B point) at which a temperature boundary layer is formed, and a turbulent flow heat exchange part (D section) having prominence and depression structures 110a, 120a, 120b and 130a formed at surfaces of the tubes 110, 120 and 130 disposed after the point at which the temperature boundary layer is formed.
As described with reference to FIG. 12, when the gap a between the tubes 110, 120 and 130 is increased to reduce an exhaust resistance, the temperature boundary layer may be rapidly formed, thereby decreasing heat transfer efficiency.
Therefore, the laminar flow heat exchange part (C section) is formed at the exhaust gas inlet port, only before the temperature boundary layer is formed, to thereby maximally absorb heat. When the laminar flow heat exchange part is also formed after the temperature boundary layer forming point (B point), the temperature boundary layer is formed, and thus the heat transfer efficiency is decreased. In order to prevent the problem, the turbulent flow heat exchange part (D section) having prominence and depression surfaces 110a, 120a, 120b and 130a is formed after the temperature boundary layer forming point (B point) to increase heat transfer efficiency.
Meanwhile, it is also possible to increase the gap between the tubes in order to reduce an exhaust resistance on the basis of the structure of the laminar flow heat exchange. In addition, even when the gap between the tubes is increased, since a turbulent flow heat exchange part may be formed to increase heat transfer efficiency, the present invention can provide advantages of both of conventional laminar flow and turbulent flow heat exchangers.
While few exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes may be made to these embodiments without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.
As can be seen from the foregoing, a heat exchanger with a combination of a laminar flow type and a turbulent flow type in accordance with an exemplary embodiment of the present invention employs a structure in which prominences and depressions are formed at surfaces of tubes of a non-fin laminar flow heat exchanger to combine the laminar flow type and the turbulent flow type. As a result, it is possible to provide the heat exchanger capable of reducing an exhaust resistance and increasing heat transfer efficiency.