JPS63251751A - Devices for fluid heating - Google Patents

Abstract

PURPOSE:To improve the efficiency of thermal conduction without increasing incomplete combustion constituents by fins by a method wherein a first thermal conducting pipe, a radiator and a second thermal conducting pipe are arranged in sequence in a flowing direction of combustion gas and each of fin heights in the first thermal conducting pipe and the second thermal conducting pipe is specified. CONSTITUTION:A device 11 for heating fluid has a casing 12 connected to a discharging port. The interior of the casing 12 is constituted by a lower mixing chamber 14 and an upper combustion chamber 15 partitioned with a burner plate 13 arranged below. A plurality of first thermal conducting pipes 16 are laterally arranged in parallel to each other near upper part of the burner plate 13, and the first thermal conducting pipes 16 are composed of a radiator 18 having aeration characteristics at their upper portions for use in performing an efficient recovery of radiation heat from the radiator 18. A plurality of second thermal conducting pipes 19 are arranged at the upper part of the radiator 18 and the second thermal conducting pipes 19 may efficiently recover heat of combustion gas of which temperature is slightly decreased after passing through the radiator 18. The first thermal conducting pipes 16 have no fins or have a fin height of less than about 3mm and the second thermal conducting pipes 19 have a fin height of over about 3mm and less than about 20mm.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a device for heating a fluid used in water heaters, bathtubs, hot water boilers, and the like.

"Prior Art and its Problems" Conventional fluid heating devices used in water heaters, bathtubs, hot water boilers, etc. have a combustion means such as a burner installed at one end of the casing, and the inside of the casing is is the combustion chamber and the flow path for the combustion gas, and heat transfer tubes are arranged in a multi-stage structure along the flow path of the combustion gas.The heat transfer tubes are heated by contact with the combustion gas, which uses so-called convection heat transfer. That's what I did.

In response to this, there is a special fluid heating device that heats the fluid flowing inside the heat transfer tube by downsizing the combustion chamber and effectively utilizing combustion heat, and using radiant heat transfer in addition to convective heat transfer. It was proposed by the present applicant as Application No. 1983-223980. This fluid heating device is constructed by snow-proofing a first heat exchanger tube, an air-permeable radiator, and a second heat exchanger tube in order in the flow direction of the combustion gas formed by the combustion means.

In this fluid heating device, the heat exchanger tube is irradiated with the radiant heat of the radiator that becomes incandescent by the combustion gas, and the heat exchanger tube is efficiently heated by convective heat transfer from the combustion gas and radiant heat transfer from the radiator. . Furthermore, when the first heat transfer tube is placed close to the combustion means, incompletely combusted components such as CO are generated due to the sudden temperature drop, but these incompletely combusted components are completely combusted when they pass through the high-temperature radiator. , the first heat exchanger tube can be placed close to the combustion means, thereby making it possible to make the device more compact.

By the way, in order to further improve the heat transfer efficiency in the above fluid heating device, it is possible to provide fins on the outer periphery of the heat transfer tube to increase the contact area with the combustion gas and improve convective heat transfer. desired. However, when fins are provided around the outer periphery of the heat transfer tube, there is a possibility that the fins may become overheated and thermally deformed, or the fins may lower the temperature of the gas, increasing incomplete combustion components such as CO. An important issue has been how to provide the fins.

``Object of the Invention'' The object of the present invention is to provide a fluid heating device in which a first heat transfer tube, a ventilated radiator, and a second heat transfer tube are sequentially arranged in the flow direction of combustion gas. By providing the fins in a predetermined manner, the purpose is to improve heat transfer efficiency without causing thermal deformation of the fins or heat loss i, and without causing an increase in incomplete combustion components due to the fins.

"Structure of the Invention" A device for heating a fluid according to the present invention includes a first heat exchanger tube, a ventilated radiator, and a second heat exchanger tube arranged in this order in the flow direction of the combustion gas formed by the combustion means. It's been done,
The first heat exchanger tube has no fins or has a fin height of 3 m.
m or less, and the second heat exchanger tube has a fin height of about 3 mm.
It is characterized by being considered super.

In the present invention, the first heat transfer tube is sandwiched between the combustion means and the radiator, and receives high temperature (for example, 1500
They are directly exposed to combustion gas (~1600℃) and are exposed to intense radiant heat from radiators. In terms of heat transfer efficiency,
Generally, it is desired that the tube be equipped with fins and have a high fin height, but if the fin height is too high, the heat transfer resistance of the fins will cause problems even though low-temperature fluid such as water is flowing inside the tube. The heat received by the fluid in the pipe cannot keep up, and the outer peripheral edge of the fin becomes overheated, eventually leading to thermal deformation. Therefore, in the present invention, thermal deformation of the fins is prevented by providing the first heat exchanger tube without fins or with a fin height of 3 mm or less. By the way, the fin height of the first heat exchanger tube is 2
It is generally preferable that the thickness be less than mm.

Furthermore, if a finned tube with a fin height of 5 mm or more is used as the first heat transfer tube, the amount of combustion gas that contacts the low-temperature fins and rapidly decreases in temperature increases, causing the first heat transfer to increase. The CO concentration due to incomplete combustion increases in the combustion gas flowing through the heat tube tl, and this flows downstream without being sufficiently oxidized, resulting in an increase in the amount of CO in the exhaust gas.

However, by making the first heat transfer tube without fins or having a fin height of 3 mm or less, the temperature of the combustion gas flowing through the first heat transfer tube #i is maintained sufficiently high, and as a result, the amount of CO in the exhaust gas is almost eliminated.

Further, when the first heat exchanger tube has fins, it is particularly preferable that the 2-inch interval between adjacent fins at the outer peripheral edge of the fin (the interval excluding the wall thickness of the fin) is equal to or less than the fin height. Thereby, the radiant heat from the m enclosure can be efficiently received.

In other words, the radiant heat from the radiator is irradiated onto the outer circumferential surface of the heat transfer tube body and both sides of the fins, but not all of the heat is received as is, and a considerable percentage is diffusely reflected.However, as mentioned above, When the spacing between the fins is set below the fin height, most of the diffusely reflected radiant heat is captured again by the nearby fin surfaces and the outer peripheral surface of the heat exchanger tube body, and as a whole, most of the radiation emitted from the radiator is absorbed by this radiant heat. It will be absorbed by the first heat exchanger tube.

On the other hand, the temperature of the combustion gas decreases by 100 to 150 degrees Celsius by passing through the radiator arrangement area, but it is still sufficiently hot (
In order to efficiently recover heat, the second heat exchanger tube is provided with fins, and the fin height is more than 3 mm, preferably 5 mm or more.

However, although the temperature in the second heat exchanger tube area is lower than that in the first heat exchanger tube area, the temperature is still quite high, so there is a risk of overheating of the outer edge of the fin, which may lead to thermal deformation. . For this reason, it is preferable that the fin height of the second heat exchanger tube be 20 mm or less.

In a more preferred embodiment of the present invention, in the second heat exchanger tube, the side closest to the radiator has a fin height of 5 to I.
Omm, and the side farthest from the radiator has a fin height of 10~
The length shall be 20 mm.

The material for both the first and second heat transfer tubes is preferably a metal material such as copper or stainless steel, but any appropriate ceramic material such as reaction sintered SiC may also be used.

In the present invention, a combustion means such as a burner is generally arranged at the end of the casing on the upstream side of the combustion gas flow path, resulting in an overall compact fluid heating device. Although a diffuse combustion type burner can be used as the burner, it is more preferable to use a premix burner that mixes combustion air and fuel gas in advance and blows out this mixed gas from a burner plate to burn it. , high surface load, and high combustion chamber load.

The number of the first heat exchanger tube and the second heat exchanger tube may be only one each, but it is generally preferable that each of the first heat exchanger tube and the second heat exchanger tube consists of a plurality of tubes to constitute a heat exchanger tube group.

The first heat exchanger tube group and the second heat exchanger tube group may each be divided into a plurality of tubes to form independent flow paths for the number of tanks, but for example, the ends of the tubes may be separated from each other on the outside or inside of the casing. It is preferable to adopt one that forms sequentially connected flow paths. In this case, the heat exchanger tubes are not only placed inside the casing so as to be in contact with the combustion gas, but also some heat exchanger tubes are placed outside in the cage jig. The outer wall of the casing may be arranged so that it is in contact with the outer wall of the casing, so that heat exchange is performed from the outer wall of the casing and the casing is also cooled.

In general, as the radiator, ceramics such as silicon carbide, enriched silicon, enriched aluminum, cordierite, mullite, lithium aluminum silicate, aluminum titanate, etc. are preferable in order to generate effective radiant heat at high temperatures. .

A ventilable radiator is used for such a radiator in order not to obstruct the flow of combustion gas and to ensure a wide contact area with the combustion gas. Specifically, examples include those in which the radiator itself has air permeability, such as honeycomb bodies, three-dimensional mesh bodies, open-cell foam bodies, mesh laminates, and visible woven fabric bodies. Among these, plate-shaped honeycomb bodies are particularly suitable. A plate-shaped honeycomb body, preferably a honeycomb body, has a large number of parallel cells penetrating the plate surface from the front and back, and the cell shape can be appropriately selected from square, rectangle, hexagon, etc. In addition, the plate-shaped honeycomb plate may be formed by laminating a large number of corrugated plates or corrugated plates and flat plates, and even if the radiator itself does not have air permeability, individual The radiators may be arranged at a predetermined distance from each other to form a ventilated radiator as a whole. In this case, a large number of ceramic rods are arranged parallel to each other and in a staggered pattern. Examples include those arranged in the form of a louver, or those arranged in a louver shape with a large number of narrow ceramic width plates.

Embodiments of the Invention In the following, embodiments of a device for heating a fluid according to the present invention will be described.

1 and 2 show a first embodiment of the device according to the invention. This fluid heating device 11 has a casing 12 whose upper part is connected to an exhaust port (not shown), and inside this casing 12, with a burner plate 13 disposed below as a boundary, a mixing chamber is located on the lower side. 14, the upper side is configured as a combustion chamber 15. burner plate 1
3 is formed into a planar shape having a large number of flame holes in the vertical direction of the casing 12, and blows out a premixture made of fuel gas and air in the mixing chamber 14 from the flame holes to generate a planar flame. Form. Note that a fan for supplying combustion air to the premixing chamber 14, a fuel gas nozzle for supplying fuel gas, and an ignition means for flame formation are not shown. After forming such a flame, the generated combustion gas flows into the combustion chamber 15.
flows from the bottom to the top.

A plurality of first heat exchanger tubes 16 are horizontally arranged in parallel with each other at a position close to the upper part of the burner plate 13 . The first heat transfer tube 16 efficiently recovers the convection heat of the combustion gas and the radiant heat from the radiator. The first heat exchanger tubes 16 are arranged in one or more stages (two stages in this embodiment) in the vertical direction, and in the case of multiple stages, the upper and lower heat exchanger tubes 16 are arranged in a staggered arrangement, for example, so that they do not overlap as much as possible. Among the first heat exchanger tubes 16, the distance from the underline of the lowest heat exchanger tube to the upper surface of the burner plate 13 is preferably 100 mm or less, preferably 5 to 50 mm.

In this embodiment, the first heat exchanger tube 16 is comprised of a loaf-in tube. That is, as shown in FIG. 2, on the outer periphery of the first heat exchanger tube 16, a large number of loaf-ins 17 having a trapezoidal or square cross section are arranged at a predetermined pitch P! It is formed with It is preferable that the interval A (distance M obtained by subtracting the thickness of the peripheral part from the pitch P) at the outer peripheral line of the loaf-in 17 is equal to the height Ho of the fin, or is less than or equal to the height H0, and in this embodiment In the case of , the height Ho is 1.5 mm and the interval A or 1. It is said to be Omm. Roughly speaking, the long end of the loaf-in tube passes through a gradual part B where the height H gradually decreases, and becomes a thick straight pipe part C, and is connected to the casing 12 at this thick straight pipe part C. There is. Incidentally, in the present invention, the fin height H is not intended to be the value in the gradual part B or the thick straight pipe part C. In addition to the tube, a pair of tubes without the loaf-in 17 can also be used.

A radiator 18 is supported on the upper part of the first heat exchanger tube 16 . This radiator 18 has ventilation so that combustion gas can flow inside the radiator 18 and pass downstream,
Almost the entire tf2i of the cross section of the combustion gas flow path is covered. In this embodiment, the radiator 18 is composed of a ceramic honeycomb plate, but other materials such as a three-dimensional mesh, an open-cell foam, a mesh laminate, etc. can also be used. Due to this radiator 18, the first heat exchanger tube 16 receives radiant heat as well as convection heat of the combustion gas.

At the top of the radiator, a plurality of second heat transfer tubes 1 are installed.
9 is placed. This second heat transfer tube 19 effectively recovers the heat of the combustion gas that has passed through the radiator 18 and whose temperature has slightly decreased. A plate fin tube with heat transfer tubes passing through it is used. The plate fins 20 are cut out from each heat transfer tube so that the fin heights are the same in a concentric circle and form a smooth valley. The fin height H of the upper peripheral edge closest to is 5 to I Omm.
The fin height H of the upper peripheral edge furthest from the radiator 18 is 10 to 20 mm. However, the outer peripheral edge of the plate fin 20 does not necessarily have to be formed into a smooth valley, and may be formed into a simple rectangular shape with a straight peripheral edge, for example.

In this embodiment, the first heat exchanger tube 16 and the second heat exchanger tube 19 are actually connected in series to constitute one flow path as a whole.

Next, the operation of the fluid heating device 11 having the above configuration will be explained.

The premixture created in the mixing chamber 14 is transferred to the burner plate 1
When passing through the flame hole 3, it is formed into a flame by the ignition means, and is sent to the combustion chamber 15 as a high-temperature combustion gas of 1500 to 1600°C.

This combustion gas is guided to the M distribution area of the first heat exchanger tube 16,
Convective heat transfer transfers a portion of the thermal energy contained in the combustion gas to the fluid flowing in the first heat transfer tube 16, in particular to a liquid such as water. Roughly speaking, the combustion gas passes through the gap between the first heat exchanger tubes 16 and flows inside the radiator 18 while remaining at a high temperature, and also heats the radiator 18 to become incandescent. Thereby, the radiator 18 is maintained at a high temperature of, for example, 1000 to 1200°C, and mainly radiates and heats the first heat exchanger tube 16. Therefore, the liquid such as water flowing through the first heat transfer tube 16 receives heat by both convective heat transfer by the combustion gas and radiant heat transfer by the radiator.

In this case, the first heat transfer tube 16 is configured with a loaf-in tube with a loaf-in 17 having a height of 3 mm or less, and in this embodiment, L5 mm, so that the radiant heat from the radiator 18 is efficiently transferred by the loaf-in 17. Even if the loaf-in 17 is captured and exposed to high-temperature combustion gas and intense radiant heat, thermal deformation and thermal damage to the outer peripheral end tightening portion of the loaf-in 17 are prevented. Furthermore, since the first heat exchanger tube 16 is placed close to the burner plate 13, CO, etc. may be generated in the combustion chamber 15 due to incomplete combustion. With this configuration, the amount of combustion gas that contacts the fins and causes a sudden temperature drop is limited, and the temperature drop occurs smoothly, preventing the oxidation of CO from proceeding and an increase in residual CON in the combustion gas. can. Roughly speaking, by setting the interval between the loaf-ins 17 to be equal to or less than the fin height H0, radiant heat can be absorbed well and heat transfer efficiency can be improved.

Then, while the combustion gas passes through the radiator 18, its temperature decreases by about 100 to 150°C, and the temperature of the combustion gas decreases by about 100 to 150°C.
is guided to the M area. The radiator 1 is also used in the second heat exchanger tube 19.
Radiant heat is irradiated from radiator 8, but the temperature of the upper surface of radiator 11 is correspondingly lower than the temperature of the lower surface, so the amount of radiant heat is irradiated from radiator 18 to the first heat exchanger tube. Approximately 50 to 70% of the amount is irradiated to the second heat exchanger tube.
A will be given. Therefore, in the second heat transfer tube 19, convective heat transfer is mainly performed through contact with the combustion gas. Since the second heat exchanger tube 19 has a plate fin 20 having a higher fin height than the fin height of the first heat exchanger tube 16, it is possible to have a wider contact area with the combustion gas. , good convective heat transfer is achieved. In general, since the temperature of the combustion gas is lowered, thermal deformation at the peripheral edge of the fin is prevented even if the fin height is high. In the case of this embodiment, the fin height Hl of the upper peripheral edge closest to the radiator 18 is 5 to I Omm, and the fin height H of the upper peripheral edge farthest from the radiator 18 is 10 to 20 mm. Therefore, convective heat transfer efficiency can be increased as much as possible while preventing thermal deformation and thermal damage to the fins. In this way, after the fluid such as water passes through the first heat exchanger tube 16, it further passes through the second heat exchanger tube 191F! : Receives thermal energy in each passage, is heated to a predetermined temperature, and is extracted.

A second embodiment of the invention is shown in FIG. In this embodiment, the second heat exchanger tube 19 is configured as a high fin tube. That is, the second heat exchanger tube 1
9 has a large number of high fins 21 on its outer periphery. The high fins 21 have different fin heights between the upper and lower heat exchanger tubes, and the lower fin height H1 and the upper fin height H2 have a relationship of H,<H. In this example, ■, is 5 to 10 mm, and H,!
Even in this example where the distance is set to -20 mm, the heat of the combustion gas whose temperature has decreased after passing through the radiator 18 can be efficiently absorbed. The rest of the configuration is similar to the first embodiment, so the explanation will be omitted.

"Effects of the Invention" As explained above, according to the fluid heating device of the present invention, the first heat exchanger tube has no fins or has a fin height of 3.
Since the second heat transfer tube has a fin height of more than 3 mm, convective heat transfer is improved without causing thermal deformation of the fins, thermal damage, or an increase in incomplete combustion components such as CO. Heat transfer efficiency can be increased.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the fluid heating device according to the present invention, and FIG. 2 is a partially cutaway front view of one of the first heat transfer tubes 16 in FIG. , FIG. 3 is a sectional view showing another embodiment of the device for heating a fluid according to the present invention. In the figure, 11 is a fluid heating device, 12 is a casing, 1
3 is a burner plate, 14 is a mixing chamber, 15 is a combustion chamber,
16 is a first heat exchanger tube, 17 is a loaf-in, 18 is a radiator, 19 is a second heat exchanger tube, 20 is a plate fin, and 21 is a high fin.

Claims (2)

[Claims] (1) A device for heating a fluid in which a first heat transfer tube, a ventilated radiator, and a second heat transfer tube are arranged in this order in the flow direction of combustion gas formed by the combustion means, A device for heating a fluid, wherein the heat transfer tube has no fins or has a fin height of 3 mm or less, and the second heat transfer tube has a fin height of more than 3 mm. (2) The device for heating a fluid according to claim 1, wherein the second heat exchanger tube has a fin height of 20 mm or less.