Vacuum water heater

Abstract

To provide a vacuum type water warmer which can adjust a sub-cool degree on a surface of a heating device of the vacuum type water warmer to reduce noise during operation start.SOLUTION: A vacuum type water warmer 1 includes: a sealed vessel 2 in which a pressure is kept lower than the atmospheric pressure and heat medium water W is enclosed; a heating device 3 which is sunk in the heat medium water W and heats the heat medium water W to evaporate the heat medium water W; a heat exchanger 5 which is disposed in a decompression space 4 above the heat medium water W and heats water H circulating therein by indirect heat exchange with steam of the heat medium water W; and a shield plate 8 which covers the heating device 3 and has a heat medium water inlet 6 at the lower side and a steam discharge port 7, which is open to an area above a water surface of the heat medium water W, at the upper side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vacuum type water heater, and more particularly to a vacuum type water heater having a sound-absorbing structure. [Background technology]

[0002] Conventionally, a vacuum water heater is known that heats heat transfer water sealed in a sealed container under reduced pressure and in a nearly vacuum state, boils it at a low temperature of 100°C or less, and uses the steam as a heat source to heat water and generate hot water.

[0003] Figure 8 shows a typical conventional vacuum water heater. The vacuum water heater 100 shown in Figure 8 includes a sealed container 101, heat transfer water W sealed in the sealed container 101, a combustion chamber 102 that is submerged in the heat transfer water W and forms a heating device for heating the heat transfer water, a combustion burner 103 that radiates a flame into the combustion chamber 102, a reduced pressure space 104 formed above the heat transfer water W, a heat exchanger 105 disposed in the reduced pressure space 104, and a group of water tubes 106 that penetrate the combustion chamber 102. The pressure inside the sealed container 101 is reduced to below atmospheric pressure by an automatic air extraction device (not shown) to create a near-vacuum state. In this state, the combustion burner 103 heats the combustion chamber 102, boils the heat transfer water W, and generates steam in the reduced pressure space 104 that has the same temperature as the heat transfer water W at that time. The steam condenses on the surface of the heat exchanger 105, heating water H1 in the heat exchanger 105 and producing hot water H2.

[0004] In this type of vacuum water heater, subcooled boiling occurs during low-pressure heating when the heat transfer water temperature is relatively low at the start of operation, and the boiling steam suddenly condenses and disappears as it rises to the water surface. When the boiling steam suddenly disappears, it generates a high-level impact sound similar to a metallic crackling sound, which is thought to be caused by pressure waves when liquid-liquid collision occurs. This impact sound is transmitted to the wall of the sealed container 2, generating an unpleasant noise. This noise tends to become louder the lower the temperature of the heat transfer water W. This is because the lower the temperature, the larger the specific volume of saturated steam, making it more likely to cause sudden condensation, and the greater the degree of subcooling (the difference between the saturated temperature on the surface of the combustion chamber and the temperature of the heat transfer water around the combustion chamber). Normally, in a sealed container that has been decompressed to near vacuum, this impact sound almost disappears once the heat transfer water temperature reaches 65°C or higher, so it is difficult to think of how to heat a container without generating noise at low temperatures. machine The challenge for the vacuum water heater was whether it could be completed.

[0005] To solve this problem, a sound-absorbing structure is known in which the bottom wall and side wall of the sealed container have a double structure to absorb the generated impact noise (Patent Document 1).

[0006] Also known is a noise-absorbing structure in which a baffle plate having a bubble flow opening and a condensed water inlet opening is provided in the heat transfer liquid to control the flow of steam bubbles generated by boiling of the heat transfer liquid and the flow of condensed water from the steam that has absorbed heat in a heat exchanger, thereby silencing noise (Patent Document 2).

[0007] Furthermore, a pressure-reducing heater is also known in which a guide member for guiding boiling steam is provided on the inside of the side wall of the sealed container, and the boiling steam that rises between the side wall and the heating device is guided toward the heating device, thereby suppressing noise generation (Patent Document 3). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 8-219402 [Patent Document 2] Japanese Patent Application Publication No. 8-189605 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-69569 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the sound deadening structure of Patent Document 1 was insufficient in its noise suppression effect against impact noise generated near the water surface. Furthermore, while Patent Documents 2 and 3 are effective in reducing impact noise caused by the rapid condensation of boiling steam generated near the surface of the heat transfer water, they are unable to suppress impact noise caused by the rapid condensation of steam generated during subcooled boiling on the surface of the combustion chamber that constitutes the heating device.

[0010] SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide a vacuum water heater that can adjust the degree of subcooling on the surface of the heating device of the vacuum water heater and suppress noise at the start of operation. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, a vacuum water heater according to one embodiment of the present invention comprises an airtight container whose interior is maintained at a pressure lower than atmospheric pressure and in which heat transfer water is sealed; a heating device that is submerged in the heat transfer water and heats and evaporates the heat transfer water; a heat exchanger that is positioned in a reduced pressure space above the heat transfer water and heats the water circulating inside by indirect heat exchange with the steam from the heat transfer water; and a shielding plate that covers the heating device and has a heat transfer water inlet on its lower side and a steam outlet on its upper side that opens above the surface of the heat transfer water.

[0012] The heating device may further include a first temperature detector that detects the temperature of the heat transfer water inside the shielding plate, a second temperature detector that detects the temperature of the heat transfer water outside the shielding plate, and a control unit that calculates the temperature difference between the temperature detected by the first temperature detector and the temperature detected by the second temperature detector and controls the heating device so that the temperature difference becomes a set temperature.

[0013] The heat transfer apparatus may have a combustion chamber and a group of water tubes that vertically penetrate the combustion chamber, and upper portions of the water tubes of the group of water tubes may be positioned above the surface of the heat transfer water.

[0014] The surface of the heat transfer water may be located between the heating device and the shielding plate.

[0015] The steam discharge port may be disposed at a position that avoids being located vertically below the heat exchanger.

[0016] The shielding plates may have a multi-layer structure, and the heat transfer water may be allowed to flow between the shielding plates.

[0017] The water pipe may have a double pipe structure. [Effects of the Invention]

[0018] According to the present invention, the degree of subcooling on the surface of the heating device can be adjusted, and the boiling steam generated on the surface of the heating device can be released into the reduced pressure space without coming into contact with the surrounding cold heat transfer water, thereby reducing the sudden condensation of the boiling steam and the noise when operation starts. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a longitudinal sectional front view showing a vacuum type water heater according to a first embodiment of the present invention together with a partially enlarged view. [Figure 2] FIG. 6 is a longitudinal sectional front view showing a vacuum type water heater according to a second embodiment of the present invention together with a partially enlarged view. [Figure 3] FIG. 10 is a partially enlarged vertical sectional top view of a vacuum type water heater according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a longitudinal sectional front view showing a vacuum type water heater according to a fourth embodiment of the present invention together with a partially enlarged view. [Figure 5] FIG. 5 is a vertical cross-sectional side view of FIG. 4 taken along the line VV. [Figure 6] FIG. 10 is a vertical sectional top view of a vacuum type water heater according to a fifth embodiment of the present invention. [Figure 7]FIG. 7 is a vertical cross-sectional side view taken along line VII-VII of FIG. 6. [Figure 8] FIG. 1 is a longitudinal sectional front view of a conventional vacuum water heater. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vacuum water heater according to an embodiment of the present invention will be described with reference to the drawings. In the following description, the same or similar components are designated by the same reference numerals throughout the drawings and embodiments.

[0021] Referring to Figure 1, the vacuum water heater 1 of the first embodiment comprises an airtight container 2 whose interior is maintained at a pressure lower than atmospheric pressure and in which heat transfer water W is sealed, a heating device 3 that is submerged in the heat transfer water W and heats and evaporates the heat transfer water W, a heat exchanger 5 that is arranged in a reduced pressure space 4 above the heat transfer water W and heats water H circulating inside by indirect heat exchange with the steam of the heat transfer water W, and a shielding plate 8 that covers the heating device 3 and has a heat transfer water inlet 6 on its lower side and a steam outlet 7 on its upper side that opens above the water surface of the heat transfer water W.

[0022] The heating device 3 includes a combustion chamber 9 and a group of water tubes 10 that vertically penetrate the combustion chamber 9. The combustion chamber 9 has a cylindrical portion 9a and a rectangular tubular portion 9b that is connected to the cylindrical portion 9a and through which the group of water tubes 10 penetrates, and is submerged in heat transfer water W. The combustion chamber 9 is not limited to a cylindrical shape, but can also be a rectangular parallelepiped (box-shaped). The bottom of the combustion chamber 9 is spaced apart from the bottom surface of the sealed container 2. A combustion burner 11 is attached to the combustion chamber 9 to form a furnace. The combustion burner 11 radiates a combustion flame into the combustion chamber 9 to heat the interior of the combustion chamber 9. A smoke chamber 12 is provided in communication with the combustion chamber 9, and a flue 13 extends from the smoke chamber 12. Combustion gas G generated in the combustion chamber 9 is discharged from the smoke chamber 12 through the flue 13.

[0023] The shielding plate 8 covers the heating device 3, thereby forming a first heating range 14 with a jacket structure around the heating device 3, into which the heat transfer water W enters. In this embodiment, the shielding plate 8 is formed in a cylindrical shape that covers the periphery of the cylindrical portion 9a of the combustion chamber 9, and the first heating range 14 is formed between the combustion chamber 9 and the shielding plate 8. The heat transfer water inlet 6 is provided so as to open at the bottom of the first heating range 14, and the steam outlet 7 is provided so as to protrude in the shape of a cylinder or a square tube at the top of the first heating range 14, with its upper end projecting above the heat transfer water W.

[0024] The heat transfer water W in the first heating range 14 is heated by the combustion burner 11 and generates boiling steam on the outer surface of the combustion chamber 9. However, because it is covered by the shielding plate 8, the degree of subcooling (the difference between the saturation temperature of the heat transfer water W on the combustion chamber surface and the temperature of the surrounding heat transfer water) is small, and sudden condensation of the steam is suppressed. Even if an impact sound due to sudden condensation of the steam is generated, the unpleasant noise is reduced because it is covered by the shielding plate 8. The steam generated in the first heating range 14 is then released into the reduced pressure space 4 from the steam release port 7. Because the steam temperature in the reduced pressure space 4 is lower than the steam temperature generated in the first heating range 14, the steam released into the reduced pressure space 4 is cooled and condensed. However, because the heat quantity per unit volume of steam is smaller than that of liquid, condensation occurs more slowly than when cooled by heat transfer water of the same temperature, and the impact sound can also be reduced.

[0025] When the temperature of the heat transfer water in the first heating range 14 becomes high, subcooled boiling also occurs on the outer surface of the shielding plate 8 in the second heating range 15 outside the shielding plate 8. Therefore, the heat transfer water temperature in the first heating range 14 and the heat transfer water temperature in the second heating range 15 are measured, and the heat transfer water temperature is adjusted based on these measured values ​​to a preset subcooling degree (here, the difference between the saturated temperature on the outer surface of the shielding plate 8 and the heat transfer water temperature around the outer periphery of the shielding plate 8) while heating until the heat transfer water temperature reaches 65°C or higher. Opportunity Perform a rotation.

[0026] Specifically, the system includes a first temperature detector 16 that detects the temperature of the heat transfer water inside the shielding plate 8, a second temperature detector 17 that detects the temperature of the heat transfer water outside the shielding plate 8, and a control unit 18 that calculates a temperature difference ΔT between the temperature detected by the first temperature detector 6 and the temperature detected by the second temperature detector 17 and controls the heating device 3 so that the temperature difference ΔT becomes a preset temperature. In this embodiment, the control unit 18 controls the amount of fuel supplied to the combustion burner 11 and the amount of air blown by the blower fan 19, thereby controlling the combustion amount of the combustion burner 11.

[0027] The inner surface of the shielding plate 8 can be considered to have the temperature of the first temperature detector 16, but the outer surface of the shielding plate 8 is always cooled by the heat transfer water W in the second heating range 15. Therefore, the temperature detected by the first temperature detector 16 plus a few degrees Celsius can be considered to be the temperature of the outer surface of the shielding plate 8, and by controlling the temperature difference ΔT, the degree of subcooling in the second heating range 15 can be controlled, and sudden condensation of steam generated by subcooled boiling can be suppressed, thereby reducing noise.

[0028] As a means for reducing noise and shortening warm-up time, as shown in Figure 2, the vacuum water heater 1 of the second embodiment is equipped with double shielding plates 8a, 8b. This forms a first heating area 14 between the combustion chamber 9 and the inner shielding plate 8a, into which the heat transfer water W enters. A second heating area 15 between the inner shielding plate 8a and the outer shielding plate 8b, into which the heat transfer water W enters, is formed. A third heating area 20 is formed outside the shielding plate 8b. Heat transfer water inlets 6a, 6b and steam outlets 7a, 7b are formed in the shielding plates 8a, 8b, respectively. The principle of noise reduction is the same as above, but because the shielding plates 8a, 8b have a double structure, the combustion area of ​​the combustion burner 11 can be increased, thereby shortening the warm-up time.

[0029] In the first and second embodiments, subcooled boiling also occurs inside the water tube 10a, but the water tube 10a is selected to have an inner diameter (for example, approximately 53 mm or less) that does not increase the degree of subcooling, and the upper end of the water tube 10a is arranged above the surface of the heat transfer water W, so that impact noise is suppressed for the same reason as the shielding plate 8 of the combustion chamber 9 described above.

[0030] However, if the degree of subcooling cannot be adjusted by selecting the inner diameter of the water tube 10a, the degree of subcooling can be adjusted by making the water tube 10a a double-pipe structure and placing heat transfer water W between the outer tube 10a1 and the inner tube 10a2, as shown in the third embodiment in Figure 3.

[0031] In the first embodiment described above, an example is shown in which the first heating range 14 is submerged in the heat transfer water W. However, as shown in the fourth embodiment in Figures 4 and 5, the surface of the heat transfer water W may be located between the upper surface of the combustion chamber 9 constituting the heating device 3 and the shielding plate 8, and the surface of the heat transfer water W may be located in the first heating range 14. In the fourth embodiment, since the surface of the heat transfer water W is lower than in the first embodiment, the length of the portion of the water pipe 10a that protrudes above the combustion chamber 9 can be made shorter than in the first embodiment, and the work of welding the water pipe 10a to the combustion chamber 9 can be made easier. Furthermore, in the fourth embodiment, the amount of heat transfer water W can be made smaller than in the first embodiment, and therefore the heating machine The drive can be completed faster.

[0032] During steady-state operation, the heat transfer water boils vigorously, and if this boiling water splashes onto the heat exchanger 5, it will hinder the condensation heat transfer of the water vapor. For this reason, the heat exchanger is generally placed at a certain distance from the surface of the heat transfer water W so as not to be affected by the boiling water, or the heat exchanger 5 is designed to be larger to take into account the reduction in heat transfer due to splashing of boiling water, and in either case the tube body (sealed container) will be larger.

[0033] Therefore, as shown in Figure 5, by arranging the steam discharge port 7 in a position that avoids being vertically below the heat exchanger 5, it is possible to prevent the heat transfer water W from scattering into the heat exchanger 5, and the sealed container 2 and the heat exchanger 5 can be designed compactly.

[0034] The present invention should not be construed as being limited to the above-described embodiment, and various modifications are possible within the scope of the invention.

[0035] For example, although the heating device is exemplified as a furnace equipped with a combustion burner, the furnace can be replaced with a fire-tube heating device that uses high-temperature exhaust gas emitted from an engine or the like as a heat source, or an electric heater can be used instead of the furnace. Fig. 6 is a longitudinal front view showing a fire-tube heating device 3 as a fifth embodiment, and Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 6. The fire-tube heating device 3 is composed of a fire-tube group 21 consisting of multiple fire tubes 21a through which high-temperature exhaust gas Ga emitted from an engine or the like passes, and this fire-tube group 21 is entirely covered by a shielding plate 8. The amount of heat input to the fire-tube heating device 3 can be controlled by adjusting the flow rate of the inflowing exhaust gas Ga using a control valve or the like (not shown).

[0036] Furthermore, in the above embodiment, a vacuum type hot water heater with a water tube structure and a combustion chamber is exemplified, but even in a vacuum type hot water heater with a furnace tube and smoke tube structure, the furnace tube that constitutes the heating device can be covered with a shielding plate.

[0037] In the above embodiment, the shielding plate has one heat transfer water inlet and one steam outlet each in the center, but their positions can be changed appropriately, taking into consideration areas where boiling is likely to occur (for example, areas close to the flame) and areas where steam is likely to accumulate (for example, upper areas close to the flame), and multiple outlets can also be provided. The steam outlet can also be provided in areas where steam is likely to accumulate, such as the corners between the shielding plate 8 and the sealed container 2. Alternatively, the steam outlet can be provided above the area where boiling is difficult, and the heat transfer water inlet can be provided below the area where boiling is likely to occur, to create a steam flow in the first heating range and promote heat absorption by the heating device.

[0038] In addition, in the above embodiment, the shielding plate has a double structure, but it may have a multi-layer structure such as a triple or quintuple structure. [Explanation of symbols]

[0039] 1 Vacuum water heater 2. Airtight containers 3 Heating device 4. Decompression space 5 Heat exchanger 6 Heat transfer water inlet 7, 7a, 7b Steam outlet 8, 8a, 8b shielding plate 9 Combustion chamber 10 Water pipe group 10a water pipe 11 Combustion burner 14 First heating range 15 Second heating range 16 First temperature detector 17 Second temperature detector 18 Control Unit 20 Third heating range W Heat transfer water

Claims

1. a sealed container whose interior is maintained at a pressure lower than atmospheric pressure and in which heat transfer water is sealed; a heating device that is submerged in the heat transfer water and heats and evaporates the heat transfer water; a heat exchanger disposed in a reduced pressure space above the heat transfer water, for heating water circulating therein by indirect heat exchange with steam of the heat transfer water; a shielding plate that covers the heating device and has a heat transfer water inlet on a lower side and a steam discharge port that opens above the water surface of the heat transfer water on an upper side; A vacuum water heater equipped with:

2. a first temperature detector for detecting the temperature of the heat transfer water inside the shielding plate; a second temperature detector for detecting the temperature of the heat transfer water outside the shielding plate; a control unit that calculates a temperature difference between the temperature detected by the first temperature detector and the temperature detected by the second temperature detector during a warm-up operation, and controls the heating device so that the temperature difference during the warm-up operation becomes a set temperature; The vacuum water heater according to claim 1 , further comprising:

3. the heating device has a combustion chamber and a group of water tubes that vertically penetrate the combustion chamber, An upper portion of the water tube of the water tube group is located above the water surface of the heat transfer water. The vacuum water heater according to claim 1.

4. The vacuum water heater according to claim 1 , wherein the surface of the heat transfer water is located between the heating device and the shielding plate.

5. 2. The vacuum water heater according to claim 1, wherein the steam outlet is disposed at a position that avoids being vertically below the heat exchanger.

6. 2. The vacuum water heater according to claim 1, wherein the shielding plates have a multi-layer structure, and the heat transfer water is allowed to flow between the shielding plates.

7. 4. The vacuum water heater according to claim 3, wherein the water pipe has a double pipe structure.

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