JP7298877B2 - Water heater - Google Patents

Description

The present invention relates to a latent heat recovery water heater using a plate heat exchanger.

A latent heat recovery type water heater is provided with a primary heat exchanger for recovering sensible heat and a secondary heat exchanger for recovering latent heat. As a primary heat exchanger, a plurality of heat transfer tubes are passed through a plurality of fins arranged side by side at predetermined intervals in the thickness direction, and high-temperature gas such as combustion exhaust of a burner is passed between the fins. A finned-tube system is known, which is capable of recovering sensible heat between a gas and a fluid flowing through a heat transfer tube.
On the other hand, as the secondary heat exchanger, a pair of heat transfer plates are joined together to form an internal flow path. A plate type is known in which both ends of an internal flow path are communicated with each other so that one side serves as an inflow path and the other side serves as an outflow path. As this heat transfer plate, Patent Document 1 discloses an invention in which V-shaped convex portions are provided and an exhaust passage is formed between the convex portions.

Japanese Patent No. 5043859

However, in the secondary heat exchanger of Patent Literature 1, the shape of the heat transfer plate is complicated, making it difficult to process, and there is a problem that the cost increases. Therefore, if the straight protrusions are used, the processing can be relatively easily performed, but the combustion exhaust flowing between the straight protrusions tends to become a laminar flow. As a result, a laminar flow boundary layer (adiabatic layer) having a low velocity is generated near the surface of the convex portion, which may hinder sufficient heat recovery and prevent an improvement in thermal efficiency.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a water heater capable of maintaining good thermal efficiency even if a plate-type heat exchanger is used .

In order to achieve the above object, the invention according to claim 1 is a water heater comprising a primary heat exchanger for sensible heat recovery and a secondary heat exchanger for latent heat recovery,
The primary heat exchanger has a plurality of fins arranged side by side at predetermined intervals in the thickness direction in the lower part of the first casing to which the burner is attached, and each fin is penetrated and the upstream end is connected to the secondary heat exchanger. A heat transfer pipe is connected and the downstream end is connected to the hot water discharge pipe,
The heat transfer tubes include a large diameter tube which penetrates each fin in a meandering manner in the first casing and whose upstream end is connected to the secondary heat exchanger via a connecting pipe, and a first heat transfer tube having a smaller diameter than the large diameter tube. a small-diameter pipe disposed outside the casing and connected to the large-diameter pipe, the downstream end of which is connected to the tapping pipe;
The secondary heat exchanger includes a plurality of pairs of pair plates, each of which is formed by combining two heat transfer plates to form an internal flow path between the two heat transfer plates, arranged side by side in the thickness direction in the second casing. An exhaust passage is formed between which the combustion exhaust passes, and both ends of each internal passage are communicated with each other to form an inflow passage to which a water supply pipe is connected at one end, and an outflow passage to which a connection pipe is connected at the other end. and form
Each heat transfer plate is provided with a plurality of linearly extending ridges inclined at a predetermined angle with respect to the passage direction of the combustion exhaust gas and arranged side by side at predetermined intervals to form an exhaust passage between the ridges. ,
A wide portion is formed at least on the downstream end in the passing direction of at least some of the ridges to make the exhaust passage between adjacent ridges narrower than on the upstream side in the passing direction. .
According to a second aspect of the present invention, in the configuration of claim 1, the wide portion is formed in a tapered shape in which the width of the ridge gradually widens from the upstream end to the downstream end in the passing direction. It is characterized by

According to the present invention, the ridges formed on each heat transfer plate are formed with wide portions that make the exhaust passage between the ridges narrower than the upstream side in the passing direction. The flow can be made turbulent, and good thermal efficiency can be maintained even with a plate type.
According to the second aspect of the invention, in addition to the above effect, the wide portion is formed in a tapered shape in which the width of the ridge gradually widens from the upstream end to the downstream end in the passing direction. Therefore, turbulent flow can be generated for a long time, and heat can be effectively recovered over the entire length of the protrusion.

1 is a front view of a water heater with a front cover removed; FIG. 1 is a front view of a water heater with resin sheets, a controller, and a display operation panel omitted; FIG. FIG. 3 is a cross-sectional view of only the inner barrel of FIG. 2 taken along the line AA. FIG. 4 is a cross-sectional view taken along line BB of FIG. 3; It is a front view of a pair plate.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a front view showing an example of a water heater, with a front cover removed. FIG. 2 shows a state in which the resin sheet, the controller, and the display operation panel are removed from FIG.
This water heater 1 accommodates an inner shell 3 in which a burner 4, a primary heat exchanger 5, and a secondary heat exchanger 6 are provided in order from the top in a square box-shaped housing 2 with an open front. It is a reverse combustion type. Further, inside the housing 2, there are provided an exhaust part 7 extending backward from the lower part of the inner shell 3 and extending upward, a fan unit 8 connected to the burner 4 on the right side of the inner shell 3, and a fan unit 8. A gas supply unit 10 is connected to the fan unit 8 on the lower side of the , and is supplied with fuel gas from a gas introduction pipe 11 via a gas governor 9 . A controller 12 containing an electric circuit board is installed laterally on the lower right side of the inner barrel 3, and a display operation panel 13 exposed from the front cover is provided at the center of the lower part.

The burner 4 is of the all-primary-air type in which a mixture of fuel gas and all the combustion air necessary for combustion is burned. It has a casing 14, and the upper surface of the upper casing 14 is closed by a chamber 15 that projects upward and to which the fan unit 8 is connected. As shown in FIGS. 3 and 4, the lower surface of the upper casing 14 is provided with a burner hole plate 16 formed with a plurality of burner holes and protruding downward in an arc shape. ), the air-fuel mixture can be combusted.
The fan unit 8 accommodates a fan (not shown) in a fan case 17 that is circular in plan view, and has a fan motor 18 that rotates the fan at the center of the upper side of the fan case 17 .

The primary heat exchanger 5 has a plurality of fins 21, 21, . The fins 21 are arranged side by side at a predetermined interval, and are made of stainless steel in which the heat transfer tubes 22 are arranged so as to pass through the fins 21 in the left-right direction.
The heat transfer tubes 22 here are eight linear large-diameter tubes 23, 23 . , and linear small-diameter tubes 24, 24 . Of these, the large-diameter tube 23 has two ends that are adjacent to each other in the front and rear direction and are alternately connected to each other by the lower headers 25 provided on the left and right side surfaces of the middle casing 20, so that the large-diameter tube 23 is connected as a whole. It has a meandering shape. However, the right end of the rearmost large-diameter tube 23 is connected to the connection pipe 26 with the secondary heat exchanger 6, and the right end of the foremost large-diameter tube 23 is connected by a front header 27 extending vertically. It is connected to the right ends of the three small-diameter tubes 24 on the front side. A left side header 28 is provided on the left side surface of the middle casing 20 to connect the left ends of the front and rear three small diameter tubes 24 to each other. A right side header 29 is provided on the right side surface of the middle casing 20 to connect the right ends of the three small-diameter tubes 24 on the rear side.

Therefore, in the heat transfer tube 22 of the primary heat exchanger 5, the hot water flowing from the connecting tube 26 into the rearmost large-diameter tube 23 meanders forward while alternately passing through the lowermost large-diameter tubes 23, 23 . . . After that, the water flows from the front large-diameter pipe 23 to the front three small-diameter pipes 24 and the rear three small-diameter pipes 24 in order to the tapping pipe 30 .
A strip-shaped resin sheet 31 having a meandering conductive pattern covering substantially the entire surface is wound around the upper outer periphery of the middle casing 20 so that leakage of combustion exhaust from the middle casing 20 can be detected. A turbulence plate 32 is inserted in each large-diameter tube 23 to stir the hot water passing therethrough.

On the other hand, in the secondary heat exchanger 6, as shown in FIGS. 3 and 4, a pair of heat transfer plates 37, 37 are joined to face each other in a square cylindrical lower casing 35 communicating with the middle casing 20. A plurality of pair plates 36 are laminated in the front-rear direction, which is the thickness direction. Each heat transfer plate 37 has a horizontally long rectangular shape when viewed from the front, and a plurality of linear protrusions 38, 38, . . . , and on both the left and right sides, vertical projections communicating with the ridges 38 are provided. Therefore, in each pair plate 36, an internal flow path 39 is formed to flow in a zigzag pattern within the ridges 38, 38 . . . 41 are formed respectively. Thus, between the pair plates 36, 36, exhaust passages 42, 42 .

As shown in FIG. 5, each ridge 38 of each heat transfer plate 37 is formed in a tapered shape in which the width in a front view gradually widens from the upper end to the lower end, and the width is widened over the entire length. It forms a portion 38a. Therefore, each exhaust passage 42 formed between the protrusions 38, 38 has a tapered shape in which the width in a front view gradually narrows from the upper end to the lower end due to the wide portions 38a of the protrusions 38, 38 on both sides. It's becoming That is, in each exhaust passage 42, there is a difference between the cross-sectional area of the inlet at the upper end and the cross-sectional area of the outlet at the lower end.

Further, in the pair plates 36, 36, . is connected with Furthermore, in the pair plates 36, 36 . . . , the upper ends of the respective outflow portions 41 form an outflow path 45 communicating in the stacking direction. is connected with A water supply pipe 47 is connected to the inlet 44 and the connecting pipe 26 is connected to the outlet 46 .
Therefore, in the secondary heat exchanger 6, the water that has flowed into the inflow path 43 from the water supply pipe 47 through the inlet 44 flows into the internal flow path 39 through the inflow part 40 of each pair plate 36, and flows into the outflow part. 41 to outflow path 45 and out outlet 46 to connecting tube 26 .

The exhaust part 7 includes a drain receiver 50 attached to the lower surface of the lower casing 35 of the secondary heat exchanger 6 and an exhaust duct 51 erected at the rear of the drain receiver 50 . A bottom portion of the drain receiver 50 is connected to a neutralizer 53 via a drain discharge pipe 52 .
The exhaust duct 51 is made of a synthetic resin and has a horizontally elongated prismatic shape, and an upper cover 54 having a cylindrical exhaust tube portion 55 protruding from the upper surface of the housing 2 is joined to the opening at the upper end of the exhaust duct 51 . .

In the water heater 1 configured as described above, when water is supplied to the appliance, the controller 12 drives the fan motor 18 to rotate the fan at a rotation speed corresponding to the amount of combustion requested by a remote controller or the like. Then, the fan unit 8 draws in air in proportion to the number of revolutions of the fan. At the same time, fuel gas is supplied from the gas introduction pipe 11 and mixed with air through a venturi provided on the suction side of the fan unit 8 in the gas supply unit 10 to produce a mixture. The produced air-fuel mixture is discharged from the outlet of the fan case 17 into the chamber 15 of the burner 4, supplied into the upper casing 14, ejected from each flame hole of the flame hole plate 16, and ignited by an ignition electrode (not shown). being burned.

Combustion exhaust from the burner 4 passes between the fins 21, 21 in the middle casing 20 of the primary heat exchanger 5, exchanges heat with hot water flowing in the heat transfer tube 22, and recovers sensible heat. In the large-diameter tubes 23 of the heat transfer tubes 22, hot water is stirred by the turbulence plates 32, so that stagnation and temperature unevenness are less likely to occur.
The combustion exhaust that has passed between the fins 21 , 21 reaches inside the lower casing 35 of the secondary heat exchanger 6 from the middle casing 20 . Therefore, as shown by dotted lines in FIG. Latent heat is recovered by exchanging heat with the water flowing through the passage 39 .
At this time, each exhaust passage 42 is tapered toward the downstream side by the wide portions 38a, 38a of the adjacent ridges 38, 38, so that the combustion exhaust gas G flowing therethrough has a flow velocity of Rising turbulence destroys the laminar flow, which is diffused and becomes turbulent like G1. Therefore, latent heat is sufficiently recovered.

The combustion exhaust that has passed through the lower casing 35 enters the drain receiver 50 of the exhaust portion 7, moves to the rear portion of the drain receiver 50, rises in the exhaust duct 51, and is discharged to the outside through the exhaust cylinder portion 55. be. The drain generated in the secondary heat exchanger 6 drops into the drain receiver 50 and is discharged to the outside of the instrument via the drain discharge pipe 52 and the neutralizer 53 .

As described above, according to the secondary heat exchanger 6 and the water heater 1 of the above-described embodiments, each heat transfer plate 37 has a plurality of ridges 38 extending linearly at a predetermined angle with respect to the passage direction of the combustion exhaust gas. , 38 are arranged side by side at predetermined intervals to form exhaust passages 42, 42 . By forming the wide portion 38a that narrows toward the downstream side in the passing direction of the exhaust passage 42, the flow of the combustion exhaust gas in the exhaust passage 42 can be made turbulent, and good thermal efficiency can be maintained even with the plate type. .
In particular, here, the wide portion 38a is formed by tapering the width of the projection 38 so that the width gradually widens from the upstream end to the downstream end in the passage direction, so that turbulence can be generated for a long time. This enables effective heat recovery over the entire length of the protrusion 38 .

In the secondary heat exchanger of the above configuration, each ridge provided on the heat transfer plate is tapered over its entire length to form a wide width portion. It is also possible to form a partially wide portion by tapering only the end portion of the . It is not necessary for all of the wide width portions to have the same form, and it is also possible to mix ridges that are tapered as a whole and ridges that are partially tapered. It is not limited to a tapered shape, and it is also possible to make only one side an inclined surface, or to form a wide portion in stages.
In addition, it is not limited to the form in which wide width portions are formed on all of the ridges, and an improvement in thermal efficiency can be expected by forming wide width portions only on some of the ridges, such as ridges that are alternately arranged in the parallel direction. .
Furthermore, the number and inclination angle of the protrusions can be changed as appropriate, and the positions of the inflow part and the outflow part, the inflow path and the outflow path are not limited to the above-described forms.

In addition, the form of the burner and the primary heat exchanger, the arrangement of the fan unit, the arrangement of the controller, and the like can be changed as appropriate. The present invention can also be applied to a water heater that does not have to be of the reverse combustion type and has a secondary heat exchanger above the primary heat exchanger.
Also, in the primary heat exchanger, the number of large-diameter tubes can be appropriately increased or decreased, and there is no problem even if there is no small-diameter tube as the heat transfer tube. The cross-sectional shape may be circular instead of elliptical. The directions of the fins and the heat transfer tubes may be reversed from the above embodiment, and the fins and the heat transfer tubes may be provided in multiple stages rather than in one stage.
Furthermore, the fan unit is a premixed type that supplies a mixture of fuel gas and combustion air to the chamber. The present invention can also be applied to a water heater that introduces fuel gas and combustion air into a chamber on the side.

DESCRIPTION OF SYMBOLS 1... Water heater, 2... Housing, 3... Inner body, 4... Burner, 5... Primary heat exchanger, 6... Secondary heat exchanger, 7... Exhaust part, 8... Fan Unit 10 Gas supply unit 12 Controller 14 Upper casing 20 Middle casing 21 Fin 22 Heat transfer tube 23 Large diameter tube 24 Small diameter tube 26... Connection pipe, 30... Hot water discharge pipe, 35... Lower casing, 36... Pair plate, 37... Heat transfer plate, 38... Projection, 38a... Wide portion, 39... Internal flow path, 40... Inflow part, 41... Outflow part, 42... Exhaust passage, 43... Inflow route, 45... Outflow route, 47... Water supply pipe, 50... Drain receiver, 51... Exhaust duct.

Claims (2)

A water heater comprising a primary heat exchanger for sensible heat recovery and a secondary heat exchanger for latent heat recovery,
The primary heat exchanger has a plurality of fins arranged side by side at predetermined intervals in the thickness direction in the lower part of the first casing to which the burner is attached, and the upstream end penetrates each fin and the secondary heat exchange a heat transfer pipe connected to the vessel and having a downstream end connected to the hot water discharge pipe;
The heat transfer tubes include a large diameter tube which penetrates each of the fins in the first casing in a meandering manner and whose upstream end is connected to the secondary heat exchanger via a connecting pipe, and a small-diameter pipe arranged outside the first casing and connected to the large-diameter pipe, the downstream end of which is connected to a tapping pipe;
The secondary heat exchanger includes a plurality of pairs of pair plates, each pair of which is formed by combining two heat transfer plates to form an internal flow path between the two heat transfer plates, arranged side by side in the thickness direction in the second casing. An exhaust passage through which the combustion exhaust passes is formed between the pair plates, and both ends of each of the internal passages are communicated with one end of which is connected to a water supply pipe , and the other end of which is connected to the connection pipe. each forming a connected outflow path ,
Each of the heat transfer plates is provided with a plurality of ridges extending linearly at a predetermined angle with respect to the passage direction of the combustion exhaust, and the exhaust passage is formed between the ridges. along with forming
At least a downstream end portion of at least some of the ridges in the passage direction is formed with a wide portion that narrows the exhaust passage between the adjacent ridges compared to the upstream side in the passage direction. A water heater characterized by: 2. The water heater according to claim 1, wherein the wide portion is formed in a tapered shape in which the width of the ridge is gradually widened from an upstream end to a downstream end in the passage direction. .

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