JP7730779B2 - Latent heat recovery heat exchanger - Google Patents

Description

The present invention relates to a latent heat recovery heat exchanger that includes a housing with an internal heat exchange chamber through which combustion exhaust gas flows from rear to front, and multiple heat absorption pipes arranged in the heat exchange chamber, and that recovers the latent heat contained in the combustion exhaust gas to heat water flowing through the heat absorption pipes.

Originally, this type of latent heat recovery heat exchanger generally has an exhaust stack attached to the front plate of the housing, into which combustion exhaust gas flows via an exhaust port opened in the front plate. The front end of the bottom surface of the heat exchange chamber has a downwardly recessed drain receiver and a drain port through which drain water from the drain receiver is discharged. Drain water is highly acidic water that is generated when moisture in the combustion exhaust gas condenses on the outer surface of the heat absorption pipe. Most of the drain water is discharged from the drain receiver through the drain port, but some of the drain water in the drain receiver can be blown up by the combustion exhaust gas heading toward the exhaust port and splashed out of the exhaust stack, potentially contaminating the area around the outside of the exhaust stack.

In light of this, a conventional latent heat recovery heat exchanger, disclosed in Patent Document 1, is equipped with a cover plate that covers the drain receiving portion from above. This prevents the combustion exhaust gas from striking the drain water in the drain receiving portion with force due to the cover plate, thereby preventing the drain water from being stirred up. Furthermore, in this type of heat exchanger, holes are formed in the cover plate that allow the drain water on the cover plate to fall into the drain receiving portion, preventing the drain water from accumulating on the cover plate.

However, it was discovered that this system had the following drawback. Namely, when a hole was formed in the cover plate, the combustion exhaust gas that had gotten under the cover plate flowed upward through the hole, creating an upward flow of combustion exhaust gas within the hole. Some of the drain water that fell through the hole was then blown up by the upward flow of combustion exhaust gas, and was scattered outside the exhaust stack.

Japanese Patent Application Laid-Open No. 2016-223645

In light of the above, the present invention aims to provide a latent heat recovery heat exchanger that can more effectively prevent drain water from splashing outside the exhaust stack.

To solve the above problems, the present invention provides a latent heat recovery heat exchanger that includes a housing with an internal heat exchange chamber through which combustion exhaust gas flows from rear to front, and multiple heat absorption pipes arranged in the heat exchange chamber. The latent heat contained in the combustion exhaust gas is recovered to heat the water flowing through the heat absorption pipes. An exhaust pipe is attached to the front plate of the housing, into which combustion exhaust gas flows through an exhaust port opened in the front plate. The front end of the bottom surface of the heat exchange chamber is provided with a drain receiver that is recessed downward and a drain port for draining drain water from the drain receiver. Furthermore, a cover plate is provided that covers the drain receiver from above. The cover plate has a downward slope in one horizontal direction perpendicular to the front-to-rear direction, so that drain water on the cover plate falls into the drain receiver from one horizontal end of the cover plate.

According to the present invention, by giving the cover plate a downward slope in one horizontal direction, drain water on the cover plate falls from one horizontal end of the cover plate into the drain receiving section, eliminating the need to form a hole in the cover plate for drain water to fall through. Therefore, drain water is not blown up by the upward flow of combustion exhaust gas generated in the hole. As a result, drain water can be effectively prevented from splashing outside the exhaust stack.

In addition, in the present invention, it is desirable that the underside of the exhaust flow path within the exhaust stack be located above the front end of the cover plate that reaches the front plate of the housing, and that a wall be provided that extends above the front end of the cover plate to the same height as the underside of the exhaust flow path. This allows the wall to function as a barrier that prevents drain water on the cover plate from entering the exhaust flow path, more effectively preventing drain water from splashing outside the exhaust stack.

Furthermore, in the present invention, when the cover plate is formed in a stepped shape with the front portion positioned lower than the rear portion, it is desirable to provide an upright baffle plate at the other lateral end of the front portion of the cover plate to prevent combustion exhaust gas from flowing from the lateral outside of that end onto the front portion of the cover plate. Here, when combustion exhaust gas flows from the lateral outside onto the front portion of the cover plate, some of the drain water flowing down the step between the rear and front portions of the cover plate may be blown up by the flow of combustion exhaust gas. By blocking the flow of combustion exhaust gas from the lateral outside onto the front portion of the cover plate with a baffle plate as described above, the blowing up of drain water flowing down the step can be suppressed, and the splashing of drain water outside the exhaust stack can be more effectively prevented.

1 is a perspective view of a latent heat recovery heat exchanger according to an embodiment of the present invention; FIG. 2 is a cross-sectional side view taken along line II-II in FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2 . FIG. 2 is an exploded perspective view showing the attachment structure of the exhaust pipe in the latent heat recovery type heat exchanger according to the embodiment. FIG. 2 is a perspective view of a cover plate provided in the latent heat recovery type heat exchanger according to the embodiment.

Referring to Figures 1 and 2, a latent heat recovery heat exchanger A according to an embodiment of the present invention comprises a housing 1 having an internal heat exchange chamber 11 through which combustion exhaust gas flows from rear to front (from right to left in Figure 2), and a plurality of heat absorption pipes 2 arranged in the heat exchange chamber 11. The latent heat contained in the combustion exhaust gas is recovered to heat the water flowing through the heat absorption pipes 2.

The rear plate 1a of the housing 1 has an inlet 12 through which combustion exhaust gas flows in after passing through a sensible heat recovery heat exchanger (not shown), and the front plate 1b of the housing 1 has an outlet 13 through which combustion exhaust gas flows out after passing through the heat exchange chamber 11. Also attached to the front plate 1b is an exhaust stack 3 into which combustion exhaust gas flows in via the outlet 13. Three upper and lower flow straightening members 31, 32, and 33 are installed within the exhaust stack 3, and two upper and lower exhaust flow paths 3a and 3b are defined between the upper flow straightening member 31 and the middle flow straightening member 32, and between the middle flow straightening member 32 and the lower flow straightening member 33. The cross-sectional area of each exhaust flow path 3a and 3b is narrowed to increase the flow velocity of the combustion exhaust gas and prevent it from accumulating near the outlet of the exhaust stack 3.

The mounting structure of the exhaust stack 3 will now be described in detail with reference to Figure 4. In this embodiment, a mounting plate 4 having an opening 41 that matches the exhaust port 13 is provided for mounting the exhaust stack 3. The mounting plate 4 is then placed on the front surface of the front plate 1b with a gasket 42 sandwiched between them, and the flange portion 34 at the rear end of the exhaust stack 3 is placed on the front surface of the mounting plate 4 with a gasket 43 sandwiched between them. In this state, the flange portion 34, along with the gasket 43, mounting plate 4, and gasket 42, are fastened together to the front plate 1b with screws 44. The portion of the mounting plate 4 near the upper edge of the opening 41 is fastened together with the gasket 42 to the front plate 1b with screws 45, and the upper part of the flange portion 34 is fastened together with the gasket 43 to the mounting plate 4 with screws 46.

In this embodiment, six heat absorption pipes 2 are arranged vertically in the heat exchange chamber 11, extending in the front-to-rear direction while meandering horizontally, perpendicular to the front-to-rear direction. Adjacent heat absorption pipes 2, 2 are offset in the front-to-rear direction by half the meandering pitch. An inlet header 21 and an outlet header 22, to which the upstream and downstream ends of the six heat absorption pipes 2 are respectively connected, are attached to the outer surface of one side panel 1c in the horizontal direction of the housing 1. Water flowing through each heat absorption pipe 2 from the inlet header 21 to the outlet header 22 is heated by the recovery of latent heat due to the condensation of moisture in the combustion exhaust gas on the outer surface of each heat absorption pipe 2.

The bottom surface 111 of the heat exchange chamber 11, which is formed by the bottom plate of the housing 1, slopes downward toward the front. A downwardly recessed drain receiver 112 is provided at the front end of the bottom surface 111, into which drain water dripping from the outer surface of the heat absorption pipe 2 flows due to the slope of the bottom surface 111. Referring to Figure 3, the drain receiver 112 has its lowest horizontal portion, which roughly coincides with the exhaust port 13, and this portion is provided with a drain outlet 113 for draining the drain water within the drain receiver 112. The drain water drained from the drain outlet 113 is led to a neutralizer (not shown).

In addition, a guide plate 5 is provided at the upper front end of the heat exchange chamber 11 to guide the flow of combustion exhaust gas downward, preventing the combustion exhaust gas from proceeding straight into the exhaust stack 3 while still containing droplets of drain water. Furthermore, a cover plate 6 is provided at the lower front end of the heat exchange chamber 11 to cover from above the drain receiving section 112 near the exhaust port 13. This prevents the combustion exhaust gas from hitting the drain water in the drain receiving section 112 with too much force, preventing the drain water from being stirred up by the combustion exhaust gas.

Here, as shown in Figure 3, the cover plate 6 has a downward slope in one horizontal direction (to the right in Figure 3). Therefore, drain water on the cover plate 6 falls from one horizontal end of the cover plate 6 into the drain receiving portion 112. Therefore, there is no need to form a hole in the cover plate 6 through which drain water can fall, as in conventional examples. If a hole were formed, the combustion exhaust gas that has slipped under the cover plate 6 would flow upward through the hole, creating an upward flow of combustion exhaust gas within the hole. Some of the drain water falling through the hole may then be lifted up by the upward flow of combustion exhaust gas and splash outside the exhaust stack 3. In contrast, in this embodiment, since no hole is formed as described above, such a problem does not occur, and splashing of drain water outside the exhaust stack 3 can be effectively prevented.

In addition, the underside of the exhaust flow path within the exhaust stack 3, i.e., the underside of the lower exhaust flow path 3b, is located above the front end of the cover plate 6, which reaches the front plate 1b of the housing 1. A wall portion 7 is provided that extends above the front end of the cover plate 6 and reaches the same height as the underside of the lower exhaust flow path 3b. This allows the wall portion 7 to function as a barrier that prevents drain water on the cover plate 6 from entering the lower exhaust flow path 3b. This more effectively prevents drain water from splashing outside the exhaust stack 3.

In this embodiment, the wall portion 7 is formed from a curved hanging plate portion 33a at the rear end of the lower straightening member 33 inside the exhaust stack 3, but this is not limited to this. For example, the exhaust port 13 could be formed with a chord-shaped lower edge whose height matches the underside of the lower exhaust flow path 3b, and the wall portion 7 could be formed from the lower part of the exhaust port 13 on the front plate portion 1b.

Referring also to Figure 5, the cover plate 6 has a stepped shape with the front portion 61 positioned lower than the rear portion 62, and a step portion 63 between the front portion 61 and the rear portion 62. The front portion 61 is sloped downward in one lateral direction. A fixing portion 64 is provided that protrudes rearward like a tongue from the rear portion 62, and is spot welded to the bottom surface 111 of the heat exchange chamber 11. The front portion 61 also has an escape hole 61a formed to prevent interference with the exhaust pipe 3 mounting screw 44.

With this type of cover plate 6, when combustion exhaust gas flows laterally outward onto the front portion 61, some of the drain water flowing down the step portion 63 may be lifted up by the flow of combustion exhaust gas. Therefore, in this embodiment, an upright baffle plate portion 65 is provided at the other lateral end of the front portion 61 of the cover plate 6 (the opposite direction from the downward slope) to prevent combustion exhaust gas from flowing laterally outward onto the front portion 61 of the cover plate 6. This suppresses the lifting up of drain water flowing down the step portion 63, more effectively preventing drain water from splashing outside the exhaust stack 3.

Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to this. For example, in the above embodiment, the cover plate 6 is provided to cover the portion of the drain receiving portion 112 closest to the exhaust port 12, but it is also possible to provide a cover plate that covers a wider area of the drain receiving portion 112.

A...Latent heat recovery heat exchanger, 1...Housing, 1b...Front plate portion, 11...Heat exchange chamber, 111...Bottom surface, 112...Drain receiving portion, 113...Drain outlet, 13...Exhaust port, 2...Heat absorption pipe, 3...Exhaust pipe, 3b...Lower exhaust flow path (exhaust flow path), 6...Cover plate, 61...Front portion, 62...Rear portion, 65...Baffle plate portion, 7...Wall portion.

Claims (3)

A latent heat recovery heat exchanger comprising a housing having an internal heat exchange chamber through which combustion exhaust gas flows from rear to front, and a plurality of heat absorption pipes arranged in the heat exchange chamber, and configured to recover latent heat contained in the combustion exhaust gas to heat water flowing through the heat absorption pipes,
An exhaust pipe is attached to the front plate of the housing, into which combustion exhaust gas flows through an exhaust port opened in the front plate,
A heat exchanger in which a drain receiving portion recessed downward and a drain outlet for draining drain water from the drain receiving portion are provided at the front end of the bottom surface of the heat exchanger, and a cover plate is further provided to cover the drain receiving portion from above,
This latent heat recovery type heat exchanger is characterized in that the cover plate has a downward slope in one lateral direction perpendicular to the front-to-rear direction, so that drain water on the cover plate falls from one lateral end of the cover plate into a drain receiving part. A latent heat recovery heat exchanger as described in claim 1, characterized in that the lower surface of the exhaust flow path within the exhaust stack is located above the front end of the cover plate that reaches the front plate portion of the housing, and a wall portion is provided that extends above the front end of the cover plate and reaches the same height as the lower surface of the exhaust flow path. A latent heat recovery heat exchanger as described in claim 1 or 2, characterized in that the cover plate is formed in a stepped shape with its front portion positioned lower than its rear portion, and a standing baffle portion is provided at the other lateral end of the front portion of the cover plate to prevent combustion exhaust gas from flowing from the lateral outside of that end onto the front portion of the cover plate.