CIRCULATION PIPING SYSTEM AND SYSTEM FOR SUPPLYING WATER CONTAINING CARBON DIOXIDE

Abstract

 A water heater that is a circulation pipe system includes a heat exchanger configured to heat water, a hot water storage tank configured to store the heated water, a circulation pipe through which water is circulated between the heat exchanger and the hot water storage tank, a hot water supply pipe through which the water stored in the hot water storage tank is supplied, a bubble injection device provided at an upstream side of a flow path communicating with the heat exchanger in the circulation pipe and configured to inject bubbles into the water, a carbon dioxide supply device connected to the bubble injection device and configured to supply bubbles containing carbon dioxide, and a controller. The controller is configured to control the bubble injection device, the heat exchanger, and the carbon dioxide supply device such that the bubbles containing the carbon dioxide are intermittently injected into the water.

Description

Technical Field

[0001] The present invention relates to a circulation pipe system and a carbon dioxide-containing water supply system that inhibit occurrence of scale adhering in a heat exchanger.

Background Art

[0002] Water heaters that supply hot water to a bathroom, a kitchen, and other places are generally classified to electric water heaters, gas water heaters (gas boilers), and oil water heaters, and any type of water heaters is provided with a heat exchanger for transmitting heat to water. In recent years, from the viewpoint of reducing carbon dioxide for energy saving or as global warming countermeasure, heat pump heat exchange type electric water heaters (heat pump water heaters) have drawn attention. The principle of a heat pump water heater is to transfer the heat of the atmosphere to a heat medium and boil water with the heat transferred to the heat medium. As the heat pump water heater uses the heat of the atmosphere, the heat pump water heater is able to use more heat energy than energy required for operation.

[0003] In the heat exchanger, to transfer heat to water, it is important to keep a heat transfer surface clean. If the heat transfer surface becomes dirty, the effective heat transfer surface area decreases, resulting in a decrease in heat transfer performance. Furthermore, if dirt accumulates on the heat transfer surface, a flow path in the heat exchanger becomes narrower, so that problems, such as an increase in the operation load of a pump for causing water to flow and clogging of the flow path, are concerned. In particular, when water containing a scale forming factor (mainly a hardness component such as calcium ion and magnesium ion) is supplied to the heat exchanger, scale is formed and adheres to the heat transfer surface of the heat exchanger, and thus problems, such as a decrease in the heat transfer performance, an increase in the operation load of the pump, and clogging of the heat exchanger flow path, are concerned.

[0004] The mechanism for the scale forming factor adhering as scale in the heat exchanger has not been fully clarified, but is that molecules of calcium carbonate or other substances are deposited at a high-temperature portion such as the heat transfer surface of the heat exchanger, and crystal growth of scale with the calcium carbonate as a nucleus proceeds. Calcium carbonate (CaCO₃), which is the main factor for scale, is present in water on the basis of equilibrium shown by the following formula (1).

[0005] Math. 1

[0006] Here, when carbon dioxide (CO₂) gas is supplied into water, carbon dioxide dissolved in water (dissolved CO₂) increases, the equilibrium in formula (1) shifts rightward such that dissolved CO₂ is reduced, and calcium carbonate turns into calcium hydrogen carbonate (Ca(HCO₃)₂) and dissolves. Consequently, by supplying carbon dioxide gas into water, an effect of inhibiting deposition of calcium carbonate molecules is expected.

[0007] For example, Patent Literature 1 discloses continuously supplying carbon dioxide gas from a gas cylinder to water flowing into a heat exchanger, as a scale removing device that inhibits adhesion of calcium carbonate molecules, by supplying carbon dioxide gas into water flowing into the heat exchanger.

Citation List

Patent Literature

[0008] Patent Literature 1: Japanese Unexamined Patent Application Publication JP 2010-223 525 A

Summary of Invention

Technical Problem

[0009] However, in the scale removing device disclosed in Patent Literature 1, as the gas cylinder is used, limitations are placed on a usage location, and maintenance such as replacement of the cylinder is required, so that there is a problem for the case of application to a domestic water heater. In addition, as bubbles containing carbon dioxide gas are continuously injected, bubbles (gas) are mixed into water, which is a heat medium, to decrease the heat transfer surface area, so that there is a problem in that the heat exchange efficiency is low.

[0010] The present invention has been made in view of the above-described problems, and a first object of the present invention is to provide a circulation pipe system that is able to inhibit adhesion of scale by introducing bubbles containing carbon dioxide into water flowing into a heat exchanger, without using a gas cylinder. In addition, a second object of the present invention is to provide a circulation pipe system and a carbon dioxide-containing water supply system that are able to inhibit a decrease in heat exchange efficiency.

Solution to Problem

[0011] A circulation pipe system according to an embodiment of the present invention includes a circulation pipe through which water is circulated between a first device and a second device, a bubble injection device configured to inject bubbles into the water, a carbon dioxide supply device connected to the bubble injection device and configured to supply carbon dioxide for generating the bubbles, and a controller configured to control the bubble injection device and the carbon dioxide supply device such that the bubbles containing the carbon dioxide are intermittently injected to the water circulating through the circulation pipe.

Advantageous Effects of Invention

[0012] According to an embodiment of the present invention, it is possible to provide a circulation pipe system that has few limitations on a usage location, does not require maintenance such as replacement of a gas cylinder, and is able to inhibit a reduction in heat exchange efficiency while inhibiting adhesion of scale to the heat exchanger on the circulation pipe.

Brief Description of Drawings

[0013] 

FIG. 1

is an example of a configuration diagram of a circulation pipe system according to Embodiment 1 of the present invention.

FIG. 2

is an example of a configuration diagram showing a bubble injection device and a carbon dioxide supply device of the circulation pipe system according to Embodiment 1 of the present invention.

FIG. 3

is a time chart illustrating pulsed bubbles in Embodiment 1 of the present invention.

FIG. 4

is an example of a configuration diagram illustrating an operation state of the circulation pipe system according to Embodiment 1 of the present invention.

FIG. 5

is an example of a configuration diagram illustrating an operation state of the circulation pipe system according to Embodiment 1 of the present invention.

FIGs. 6

are examples showing the bubble injection device of the circulation pipe system according to Embodiment 1 of the present invention.

FIG. 7

is an example of a configuration diagram of a circulation pipe system according to Embodiment 2 of the present invention.

FIG. 8

is an example of a configuration diagram of a circulation pipe system according to Embodiment 3 of the present invention.

FIG. 9

is an example of a configuration diagram of a carbon dioxide-containing water supply system according to Embodiment 4 of the present invention.

FIG. 10

is an example of a configuration diagram of the carbon dioxide-containing water supply system according to Embodiment 4 of the present invention.

FIG. 11

is an example of a configuration diagram of a carbon dioxide-containing water supply system according to Embodiment 5 of the present invention.

FIG. 12

is an example of a configuration diagram of the circulation pipe system according to Embodiment 2 of the present invention.

Description of Embodiments

[0014] Hereinafter, preferred Embodiments of a water heater of the present invention will be described with reference to the drawings. The present invention is not limited to Embodiments described below. In addition, the size and the shape of each component in the drawings are clearly represented for the sake of description and may be different from the actual size and shape.

Embodiment 1

[0015] FIG. 1 is an example of a configuration diagram of a circulation pipe system according to Embodiment 1 of the present invention. The water heater 100 includes a hot water storage tank 14 that stores hot water (water), a degassing valve 12 through which gas stored in the hot water storage tank is discharged, an air heat exchanger 1, a fan 4 that sends air to the air heat exchanger 1, a compressor 3 that compresses refrigerant, a water heat exchanger 7, a pressure reducing unit 5 that reduces the pressure of the compressed refrigerant, a water pump 11 that sends water, a bubble injection device 10, a carbon dioxide supply device 8, and a controller 24. A refrigerant flow path 2 and a water flow path 6 are provided in the water heater 100. A hot water supply pipe 13 and a water supply pipe 15 are connected to the hot water storage tank 14. Water is supplied from the outside through the water supply pipe 15 to the hot water storage tank 14, and hot water stored in the hot water storage tank 14 flows through the hot water supply pipe 13 to the outside.

[0016] For example, carbon dioxide (CO₂) refrigerant flows in the refrigerant flow path 2. The flow direction of the refrigerant in the refrigerant flow path 2 is arrow directions in FIG. 1. On the refrigerant flow path 2, the air heat exchanger 1, the compressor 3, the water heat exchanger 7, and the pressure reducing unit 5 are provided in this order. The refrigerant flowing in the refrigerant flow path 2 exchanges heat with air that is supplied to the air heat exchanger 1 by driving the fan 4. Thus, the refrigerant flowing in the air heat exchanger 1 receives heat from the air to increase its temperature, and the air supplied to the air heat exchanger 1 rejects heat to the refrigerant to decrease its temperature. The refrigerant having received heat from the air to increase its temperature is supplied to the suction side of the compressor 3 and compressed in the compressor 3. The refrigerant having been compressed in the compressor 3 into high-temperature and high-pressure refrigerant exchanges heat with water flowing in the water flow path 6, through a heat transfer surface of the water heat exchanger 7. The refrigerant flowing out from the water heat exchanger 7 in the refrigerant flow path 2 is reduced in pressure at the pressure reducing unit 5 to have a low temperature, and is supplied to the air heat exchanger 1.

[0017] In the water flow path 6, water supplied by the water pump 11 flows. The flow direction of the water in the water flow path 6 is arrow directions in FIG. 1. On the water flow path 6, the hot water storage tank 14, the water pump 11, the bubble injection device 10, and the water heat exchanger 7 are provided in this order. In addition, the degassing valve 12 is provided to the hot water storage tank 14. Furthermore, the bubble injection device 10 is connected to the carbon dioxide supply device 8. The bubble injection device 10 only needs to be provided at the upstream (inlet) side of the water heat exchanger 7, and may be provided at the upstream side of the water pump 11. Water stored in the hot water storage tank 14 flows through the interior of the water flow path 6 into the water heat exchanger 7 and exchanges heat with the refrigerant, which is supplied from the air heat exchanger 1, in the water heat exchanger 7 to increase the temperature of the water. The temperature-increased water having flowed out from the water heat exchanger 7 returns to the hot water storage tank 14. An example of a counter flow water heat exchanger in which the flow direction of refrigerant and the flow direction of water are opposite to each other is shown in FIG. 1, but the present invention is not limited to this example, and a parallel flow water heat exchanger in which refrigerant and water flow in parallel may be used. In addition, an example in which water flows from the vertically lower side of the water heat exchanger toward the vertically upper side of the water heat exchanger is shown in FIG. 1, but the present invention is not limited to this example, and a water heat exchanger in which water flows from the vertically upper side of the water heat exchanger toward the vertically lower side of the water heat exchanger may be used.

[0018] The water heat exchanger 7 serves to heat water by exchanging heat between the refrigerant and the water. For example, a plate heat exchanger, a multi-tube heat exchanger, a double-tube heat exchanger, a micro channel heat exchanger, a boiler heat exchanger, or a twisted-tube heat exchanger may be used as the water heat exchanger 7.

[0019] The bubble injection device 10 is provided at the upstream (inlet) side of the water heat exchanger 7 and has a function to inject bubbles into the water flowing into the water heat exchanger 7. FIG. 3 shows a time chart illustrating pulsed bubbles, as an example in which bubbles are intermittently injected in the present invention. Here, pulsed bubbles refer to bubbles that are injected into water and have the injection amount fluctuating in a pulse waveform. In Embodiment 1, a pulsed bubble injection device is used as an example of the bubble injection device 10 that injects pulsed bubbles. The pulsed bubble injection device will be described later. The position of the pulsed bubble injection device described later only needs to be on the water flow path 6 at the upstream side of the water heat exchanger 7, and is not particularly limited.

[0020] FIG. 2 is an example of a configuration diagram showing the bubble injection device and the carbon dioxide supply device of the circulation pipe system according to Embodiment 1 of the present invention. The pulsed bubble injection device 10b includes a gas-liquid mixing unit 23, a negative pressure generating unit 22, and a first opening-closing valve 9. In the pulsed bubble injection device 10b, the gas-liquid mixing unit 23, the negative pressure generating unit 22, and the first opening-closing valve 9 are connected in this order. That is, the gas-liquid mixing unit 23, the negative pressure generating unit 22, and the first opening-closing valve 9 are connected such that the negative pressure generating unit 22 is connected to the gas-liquid mixing unit 23, the first opening-closing valve 9 is connected to the negative pressure generating unit 22, and the negative pressure generating unit 22 is provided between the gas-liquid mixing unit 23 and the first opening-closing valve 9. In addition, the first opening-closing valve 9 is connected to the carbon dioxide supply device 8 and provided between the negative pressure generating unit 22 and the carbon dioxide supply device 8.

[0021] FIGs. 6 are examples showing the bubble injection device of the circulation pipe system according to Embodiment 1 of the present invention. FIG. 6(a) shows a gas introduction pipe, FIG. 6(b) shows a diffuser pipe, diffused air balls, and a porous nozzle, FIG. 6(c) shows a spray nozzle, FIG. 6(d) shows an ejector, and FIG. 6(e) shows pressure-feeding. In FIGs. 6(a) to (e), a solid arrow indicates the flow direction of water, and a broken arrow indicates the flow direction of gas. In FIG. 6(b), the diffuser pipe, the diffused air balls, and the porous nozzle have shapes different from each other. The gas-liquid mixing unit 23 has the gas introduction pipe (see FIG. 6(a) that is able to introduce gas, in addition to a flow path communicating with the water flow path 6, and has a function to add gas to the water flowing into the water heat exchanger 7, to mix bubbles into the water. As one having such a function, for example, a gas introduction pipe that causes gas to flow into a liquid, a diffuser pipe that introduces gas into a liquid by dispersing the gas into the liquid, diffused air balls and a porous nozzle, a spray nozzle that mixes and sprays gas and a liquid, and an ejector that creates a mixed flow of gas and a liquid may be used (see FIGs. 6(a) to (d)). Next, an example of the present invention will be described with reference to an example in which an ejector is used as the gas-liquid mixing unit 23. Embodiment 1 will be described with an example in which gas containing carbon dioxide is sucked by an ejector and introduced to the gas-liquid mixing unit 23. Gas containing carbon dioxide may be pressed and introduced by a pressure pump or other similar device (see FIG. 6(e)).

[0022] The ejector is provided with a narrow portion on the water flow path 6, and the flow rate of the water flowing in the water flow path 6 is increased at this portion. It is possible to suck gas from the gas introduction pipe due to a pressure reduction phenomenon (normally, called Bernoulli theorem) occurring at the narrow portion, so that it is possible to inject bubbles into water flowing in the water flow path 6. In Embodiment 1, an example in which the ejector is disposed such that the direction of water flowing in the ejector is horizontal is shown, but the present invention is not limited to this example, and water may flow in the ejector in the vertical direction. When a primary side at which water flows into the ejector is set at the vertically upper side, and a secondary side at which the water flows out from the ejector is set at the vertically lower side, it is possible to increase the pressure difference between the primary side and the secondary side, so that it is possible to enhance the pressure reduction phenomenon occurring at the narrow portion to increase the amount of gas sucked from the gas introduction pipe. That is, the amount of gas sucked with the same power is large, so that it is possible to increase operation efficiency (save energy).

[0023] As shown in FIG. 2, the gas-liquid mixing unit 23 is connected to the carbon dioxide supply device 8 via the negative pressure generating unit 22 and the first opening-closing valve 9. Thus, gas sucked by the gas-liquid mixing unit 23 is gas having a high concentration of carbon dioxide supplied from the carbon dioxide supply device 8 (described in detail later). Thus, it is possible to inject bubbles having a high carbon dioxide concentration into the water flowing in the water flow path 6. A check valve may be provided between the gas-liquid mixing unit 23 and the negative pressure generating unit 22 such that the flow direction of gas is from the negative pressure generating unit 22 to the gas-liquid mixing unit 23.

[0024] The negative pressure generating unit 22, which is provided between the gas-liquid mixing unit 23 and the first opening-closing valve 9, has a certain volume space.

[0025] The first opening-closing valve 9 has a function to provide or block communication between the negative pressure generating unit 22 and the carbon dioxide supply device 8 by opening or closing. As one having such a function, for example, a solenoid valve may be used. In addition, the first opening-closing valve 9 is connected to the controller 24, and it is possible to control opening or closing of this valve by the controller 24.

[0026] The carbon dioxide supply device 8 includes a carbon dioxide concentration unit 18, a suction pipe 21, a second opening-closing valve 19, an air-sending pump 20, a discharge pipe 16, and a third opening-closing valve 17. The carbon dioxide supply device 8 is connected to the pulsed bubble injection device 10b and has a function to supply gas having a high carbon dioxide concentration to the pulsed bubble injection device 10b. Thus, it is possible to inject bubbles having a high carbon dioxide concentration into the water flowing in the water flow path 6, by using the carbon dioxide supply device 8 and the pulsed bubble injection device 10b.

[0027] The carbon dioxide concentration unit 18 is provided with an adsorbent that adsorbs carbon dioxide and that is included in the carbon dioxide concentration unit 18, and has a function to concentrate carbon dioxide by adsorption. As an adsorbent having such a function, for example, zeolite, molecular sieve, alumina, activated carbon, solid amine, or other material may be used. The second opening-closing valve 19 and the air-sending pump 20 are connected to the carbon dioxide concentration unit 18 via the suction pipe 21, and the third opening-closing valve 17 is connected to the carbon dioxide concentration unit 18 via the discharge pipe 16. The second opening-closing valve 19 and the air-sending pump 20 only need to be provided on the suction pipe 21, but are more preferably disposed such that the second opening-closing valve 19 is provided between the carbon dioxide concentration unit 18 and the air-sending pump 20.

[0028] The suction pipe 21 has one end connected to the carbon dioxide concentration unit 18 and another end opening to the atmosphere. In addition, as described above, the second opening-closing valve 19 and the air-sending pump 20 are provided on the suction pipe 21. The suction pipe 21 has a function to pass air sent from the atmosphere to the carbon dioxide concentration unit 18 by the air-sending pump 20.

[0029] The second opening-closing valve 19 is provided on the suction pipe 21 and has a function to provide or block communication between the carbon dioxide concentration unit 18 and the atmosphere by opening or closing. As one having such a function, for example, a solenoid valve may be used as the second opening-closing valve 19. The second opening-closing valve 19 is connected to the controller 24, and it is possible to control opening or closing of this valve by the controller 24. The second opening-closing valve 19 only needs to be provided on the suction pipe 21, and the position of the second opening-closing valve 19 is not limited to the illustrated position (a position between the carbon dioxide concentration unit 18 and the air-sending pump 20).

[0030] The discharge pipe 16 has one end connected to the carbon dioxide concentration unit 18 and another end opening to the atmosphere. The discharge pipe 16 has a function to discharge air sent to the carbon dioxide concentration unit 18 by the air-sending pump 20, to the atmosphere.

[0031] The third opening-closing valve 17 is provided on the discharge pipe 16 and has a function to provide or block communication between the carbon dioxide concentration unit 18 and the atmosphere by opening or closing. As one having such a function, for example, a solenoid valve may be used as the third opening-closing valve 17. The third opening-closing valve 17 is connected to the controller 24, and it is possible to control opening or closing of this valve by the controller 24.

[0032] The air-sending pump 20 is provided on the suction pipe 21 and has a function to pass air in the atmosphere through the suction pipe 21, the carbon dioxide concentration unit 18, and the discharge pipe 16 in this order. The position at which the air-sending pump 20 is connected may not be on the suction pipe 21 and may be on the discharge pipe 16. The air-sending pump 20 is connected to the controller 24, and it is possible to control activation and deactivation of the air-sending pump 20 by the controller 24.

[0033] The carbon dioxide concentration unit 18 and the suction pipe 21 are connected to each other at a position close to the first opening-closing valve 9 (shown in the vertically lower side in the drawing), and the carbon dioxide concentration unit 18 and the discharge pipe 16 are connected to each other at a position far from the first opening-closing valve 9 (shown in the vertically upper side in the drawing). That is, the position at which the carbon dioxide concentration unit 18 and the suction pipe 21 are connected to each other is closer to the first opening-closing valve 9 than is the position at which the carbon dioxide concentration unit 18 and the discharge pipe 16 are connected to each other.

[0034] As described above, the first opening-closing valve 9, the second opening-closing valve 19, the third opening-closing valve 17, and the air-sending pump 20 are connected to the controller 24. Opening and closing of the first opening-closing valve 9, the second opening-closing valve 19, the third opening-closing valve 17, and the air-sending pump 20, and activation and deactivation of the air-sending pump 20 are controlled by the controller 24 such that these devices operate in conjunction with each other.

[0035]  FIGs. 4 and 5 are each an example of a configuration diagram illustrating an operation state of the circulation pipe system according to Embodiment 1 of the present invention. In FIGs. 4 and 5, each solid arrow indicates the flow direction of water, and each broken arrow indicates the flow direction of gas. In the case of a state where the first opening-closing valve 9 is closed by control of the controller 24, the second opening-closing valve 19 and the third opening-closing valve 17 are opened, and the air-sending pump 20 is turned on (hereinafter, valve operation state A). FIG. 4 represents the valve operation state A. In FIG. 4, opened and closed states of the opening-closing valves are indicated by o (opened) and c (closed) given after the reference signs. At this time, the atmosphere and the carbon dioxide concentration unit 18 communicate with each other, and air flows from the atmosphere to the carbon dioxide concentration unit 18. On the other hand, in the case of a state where the first opening-closing valve 9 is opened, the second opening-closing valve 19 and the third opening-closing valve 17 are closed, and the air-sending pump 20 is turned off (hereinafter, valve operation state B). FIG. 5 represents the valve operation state B. In FIG. 5, opened and closed states of the opening-closing valves are indicated by o (opened) and c (closed) given after the reference signs. At this time, communication between the atmosphere and the carbon dioxide concentration unit 18 is blocked, and the air-sending pump 20 is deactivated, so that air does not flow from the atmosphere to the carbon dioxide concentration unit 18.

[0036] When the valve operation state A is brought about, gas in the negative pressure generating unit 22 is sucked due to the pressure reduction phenomenon of the gas-liquid mixing unit 23. When this state is maintained, as the gas in the negative pressure generating unit 22 reduces, the pressure in the negative pressure generating unit 22 gradually falls to bring about a negative pressure state (a state where the pressure is not higher than the atmospheric pressure). At this time, the difference in internal pressure between the carbon dioxide supply device 8 and the negative pressure generating unit 22 is great. In this state, when the first opening-closing valve 9 is opened, that is, when the a switch is made from the valve operation state A to the valve operation state B, the carbon dioxide concentration unit 18 and the pulsed bubble injection device 10b communicate with each other, and thus a great pressure difference is instantaneously created between the carbon dioxide supply device 8 and the negative pressure generating unit 22. As a result, it is possible to supply gas having a high carbon dioxide concentration from the carbon dioxide concentration unit 18 (carbon dioxide supply device 8) to the pulsed bubble injection device 10b (negative pressure generating unit 22) all at once. The gas supplied to the negative pressure generating unit 22 is instantaneously sucked due to the pressure reduction phenomenon of the gas-liquid mixing unit 23. Because of this operation, it is possible to inject pulsed bubbles into the water flowing in the water flow path 6, due to the great pressure difference created instantaneously, by instantaneously opening the first opening-closing valve 9.

[0037] FIG. 3 is a time chart illustrating pulsed bubbles in Embodiment 1 of the present invention. The vertical axis indicates an amount of bubbles injected, and the horizontal axis indicates an operation time of the water heater 100. As gas having a high carbon dioxide concentration is supplied from the carbon dioxide supply device 8 to the negative pressure generating unit 22 all at once and instantaneously sucked into the gas-liquid mixing unit 23 by making a switch to the valve operation state B after the valve operation state A is continued as described above, it is possible to make steep a gradient a of a pulse waveform of the amount of bubbles injected to the water flow path 6. Furthermore, in Embodiment 1, the first opening-closing valve 9, the second opening-closing valve 19, the third opening-closing valve 17, and the air-sending pump 20 are controlled by the controller 24 such that an operation time t1 for the valve operation state A is, for example, 1 to 30 minutes and an operation time t2 for the valve operation state B is, for example, about 5 to 20 seconds. Control is performed by the controller 24 such that the ratio (t1/t2) of the operation times for the valve operation state A and the valve operation state B is in a range of, for example, 3 < (t1/t2) < 360, preferably 5 < (t1/t2) < 180, and further preferably 10 < (t1/t2) < 40.

[0038] Specifically, control is performed by the controller 24 such that duration of the valve operation state B is 5 to 20 seconds and duration of the valve operation state A is longer than three times and shorter than 360 times the duration of the valve operation state B, control is preferably performed by the controller 24 such that the duration of the valve operation state A is longer than 5 times and shorter than 180 times the duration of the valve operation state B, and control is further preferably performed by the controller 24 such that the duration of the valve operation state A is longer than 10 times and shorter than 40 times the duration of the valve operation state B. By operating the valve operation state as described above, the injection amount of bubbles having a high carbon dioxide concentration into the water flow path 6 changes in a pulse waveform as shown in FIG. 3, so that it is possible to inject pulsed bubbles having a high carbon dioxide concentration into the water flow path 6. As a result, it is possible to intermittently inject bubbles having a high carbon dioxide concentration to the water flow path 6, by the controller 24.

[0039] When pulsed bubbles having a high carbon dioxide concentration are injected into the water flowing in the water flow path 6, part of carbon dioxide that is the bubble component dissolves into the water. The carbon dioxide having dissolved into the water causes the equilibrium in the above formula (1) to shift rightward to dissolve calcium carbonate (CaCO₃), which is the main factor for scale, into calcium hydrogen carbonate (Ca(HCO₃)₂). That is, the effect of inhibiting deposition of scale is obtained.

[0040] Furthermore, as it is possible to use the great pressure difference created instantaneously between the carbon dioxide supply device 8 and the negative pressure generating unit 22, it is possible to inject pulsed bubbles having a large bubble diameter of 1 mm or greater into the water flow path 6. By injecting pulsed bubbles having a large bubble diameter, when bubbles having a bubble diameter of 100 µm or less called microbubbles have adhered to the heat transfer surface of the heat exchanger, it is possible to obtain an effect that pulsed bubbles having a large bubble diameter and microbubbles adhering to the heat transfer surface unite with each other to detach the microbubbles from the heat transfer surface. That is, it is possible to inhibit a decrease in the heat transfer surface area due to adhesion of microbubbles to the heat transfer surface, and thus it is possible to inhibit a decrease in heat exchange efficiency. The inventors of the present application observed a phenomenon that pulsed bubbles having a large bubble diameter unite with small bubbles of 100 µm or less adhering to the heat transfer surface of the heat exchanger to detach the small bubbles from the heat transfer surface.

[0041] Here, operation of the water heater 100 will be specifically described. By control of the controller 24, in the valve operation state A, that is, in a state where the first opening-closing valve 9 was closed, the second opening-closing valve 19 and the third opening-closing valve 17 were opened, and the air-sending pump 20 was activated, operation of the water heater 100 was started. In the valve operation state A, the flow rate of water flowing in the water flow path 6 of the water heater 100 was set to about 18 to 20 L/min. As an example, the volume space (capacity) of the negative pressure generating unit 22 was set to about 100 cm³, the capacity of the carbon dioxide concentration unit 18 was set to about 150 cm³, and the carbon dioxide concentration unit 18 was filled with about 100 g of zeolite as a carbon dioxide adsorbent, and the water heater 100 was operated. When operation was started, a pressure reduction phenomenon of the gas-liquid mixing unit 23 occurred due to the flow rate of the water flowing in the water flow path 6, gas remaining in the negative pressure generating unit 22 in the initial state was sucked and injected into the water flow path 6. A steady state was gradually reached, and water containing no gas (bubbles) flowed in the water flow path 6. The gauge pressure of the negative pressure generating unit 22 had been shown as a negative pressure. This state was continued for 5 minutes (t1), and the water flowing in the water flow path 6 was heated by the water heat exchanger 7. At this time, the atmosphere was caused to flow to the carbon dioxide concentration unit 18 by the air-sending pump 20, and carbon dioxide was adsorbed by the adsorbent in the carbon dioxide concentration unit 18.

[0042] Subsequently, a switch was made to the valve operation state B by control of the controller 24. At this time, pulsed bubbles having a high carbon dioxide concertation were injected into the water flow path 6 all at once due to the pressure difference between the carbon dioxide concentration unit 18 and the negative pressure generating unit 22. This state was continued for 5 seconds (t2).

[0043] Subsequently, the water heater 100 was operated while the valve operation state A and the valve operation state B were repeated and pulsed bubbles were injected into the water flowing in the water flow path 6. As a result, a decrease in COP (Coefficient of Performance), which is one index representing heat exchange efficiency, was equal to or lower than 5%. As described above, it was possible to control the amount of pulsed bubbles flowing into the heat exchanger, and the effect of inhibiting a decrease in heat exchange efficiency was obtained while the effect of inhibiting deposition of scale was obtained.

[0044]  As described above, according to Embodiment 1, when the first opening-closing valve 9 is opened, it is possible to supply gas having a high carbon dioxide concertation from the carbon dioxide concentration unit 18 of the carbon dioxide supply device 8 to the negative pressure generating unit 22 of the bubble injection device 10 all at once due to a great pressure difference created instantaneously. Then, by controlling the valve operation state A and the valve operation state B as described above, it is possible to obtain the effect of inhibiting adhesion of scale while inhibiting a decrease in efficiency of heat exchange by controlling the amount of high-carbon-dioxide bubbles flowing into the heat exchanger.

[0045] Generally, when heat is exchanged between refrigerant and water in a water heat exchanger, heat from the refrigerant, serving as a heat medium, is transmitted to the water to heat the water. When bubbles (gas) is mixed into the water, which is the heat medium, the heat transfer surface area decreases, depending on the volume of the mixed bubbles, and thus the heat exchange efficiency decreases. Consequently, when bubbles are steadily (continuously) mixed into the water serving as a heat medium, a decrease in heat exchange efficiency becomes significant. In addition, the difference in heat capacity between the water and the gas (bubbles) is considered as one factor for a decrease in heat exchange efficiency. Furthermore, the inventors of the present application observed a phenomenon that when small bubbles (100 µm or less) called microbubbles are mixed into a heat exchanger, the microbubbles easily adhere (are likely to adhere) to the heat transfer surface of the heat exchanger. The microbubbles adhering to the heat transfer surface directly decrease the heat transfer surface area that is effective for heat exchange, and thus become one factor for a decrease in heat exchange efficiency.

[0046] In the water heater 100 including the bubble injection device 10 of Embodiment 1, as bubbles injected are the above-described pulsed bubbles, it is possible to intermittently cause bubbles to flow into the water flow path 6, and thus it is possible to control the amount of bubbles flowing into the water heat exchanger 7. Thus, it is possible to obtain the effect of inhibiting a decrease in heat exchange efficiency while obtaining the effect of inhibiting adhesion of scale due to injection of bubbles into the water heat exchanger 7.

[0047]  Furthermore, as it is possible to use a great pressure difference obtained instantaneously, it is possible to inject pulsed bubbles having a bubble diameter of 1 mm or greater into the water flow path 6. As it is possible to inject pulsed bubbles having a large bubble diameter, even when the above-described microbubbles have adhered to the heat transfer surface of the water heat exchanger 7, pulsed bubbles having a large bubble diameter unite with the microbubbles adhering to the heat transfer surface, and thus it is possible to obtain the effect of detaching the microbubbles from the heat transfer surface. That is, according to Embodiment 1, it is possible to inhibit a decrease in heat transfer surface area due to adhesion of microbubbles, and thus it is possible to further enhance the effect of inhibiting a decrease in heat exchange efficiency.

[0048] Furthermore, according to Embodiment 1, as it is possible to supply carbon dioxide without using a gas cylinder, an effect can be obtained that few limitations are placed on a usage location and maintenance such as replacement of a cylinder is unnecessary. The carbon dioxide concertation in the atmosphere is about 0.04%, and it is possible to supply gas having a high carbon dioxide concertation of about 50 to 96% into the water flow path 6 by the carbon dioxide concentration unit 18.

[0049] The position at which the carbon dioxide concentration unit 18 and the suction pipe 21 are connected to each other, and the position at which the carbon dioxide concentration unit 18 and the discharge pipe 16 are connected to each other are not particularly limited. However, as in Embodiment 1, the position at which the carbon dioxide concentration unit 18 and the suction pipe 21 are connected to each other is more preferably closer to the first opening-closing valve 9 than is the position at which the carbon dioxide concentration unit 18 and the discharge pipe 16 are connected to each other. When the suction pipe 21 and the discharge pipe 16 are provided in such a positional relationship, it is possible to cause air (atmosphere) flowing in the carbon dioxide concentration unit 18 to flow from a position close to the first opening-closing valve 9 toward a position far from the first opening-closing valve 9. As a result, it is possible to adsorb carbon dioxide from a position close to the first opening-closing valve 9 by the adsorbent provided in the carbon dioxide concentration unit 18. In other words, it is possible to make the amount of carbon dioxide adsorbed by the adsorbent at the position close to the first opening-closing valve 9, larger than or equal to the amount of carbon dioxide adsorbed by the adsorbent at a position far from the first opening-closing valve 9. Thus, in the valve operation state B, carbon dioxide adsorbed by the adsorbent close to the first opening-closing valve 9 is initially sucked (desorbed), and thus it is possible to more quickly supply bubbles having a high carbon dioxide concertation into the water flowing in the water flow path 6. Consequently, it is possible to dissolve carbon dioxide in the water flowing in the water flow path 6. Thus, it is possible to cause the equilibrium in the above formula (1) to shift rightward to dissolve calcium carbonate (CaCO₃), which is the main factor for scale, into calcium hydrogen carbonate (Ca(HCO₃)₂) more quickly. That is, the effect of inhibiting deposition of scale is higher.

[0050] In addition, a pump having a high feed pressure may be used as the air-sending pump 20. Regarding an opened-closed state of each valve at this time, in the case of a state where the first opening-closing valve 9 is closed, it is only required that the second opening-closing valve 19 is opened, and the third opening-closing valve 17 is semi-opened (its opening degree may be optionally determined between full opening and full closing). That is, when the air-sending pump 20 is activated and air is caused to flow to the carbon dioxide concentration unit 18, the pressure of flow in the discharge pipe 16 only needs to be lower than the pressure of flow in the suction pipe 21. At this time, it is possible to make the internal pressure of the carbon dioxide concentration unit 18 equal to or higher than the atmospheric pressure. By using the pump having a high feed pressure as described above, it is possible to increase the internal pressure of the carbon dioxide concentration unit 18 to further increase the pressure difference between the carbon dioxide concentration unit 18 and the negative pressure generating unit 22. Subsequently, by bringing about the above-described valve operation state B (in which the first opening-closing valve 9 is opened and both the second opening-closing valve 19 and the third opening-closing valve 17 are closed), it is possible to inject pulsed bubbles having a steeper gradient a in a pulse waveform into the water flowing in the water flow path 6. The advantageous effects obtained by causing pulsed bubbles to flow into the water flowing in the water flow path 6 are as described above.

[0051] Furthermore, it is possible to increase the rate of generation of large pulsed bubbles having a bubble diameter of 1 mm or greater. Thus, even when the above-described microbubbles adhere to the heat transfer surface of the water heat exchanger 7, it is possible to further enhance the effect that pulsed bubbles having a large bubble diameter and the microbubbles adhering to the heat transfer surface unite with each other, thereby detaching the microbubbles from the heat transfer surface. That is, it is possible to inhibit a decrease in the heat transfer surface area due to adhesion of microbubbles, and it is possible to further enhance the effect of inhibiting a decrease in heat exchange efficiency.

[0052] In the present specification, the example of the heat pump water heater has been mainly described, but it is needless to say that application to a circulation pipe system, such as an air-conditioning apparatus including a water heat exchanger (that is, a refrigeration cycle apparatus including a refrigerant circuit and a water circuit connected to a water heat exchanger), is possible. In addition, it is needless to say that, even with a configuration in which the carbon dioxide supply device 8 is not provided and the pulsed bubble injection device 10b is merely provided, it is possible to inject pulsed bubbles, and it is possible to obtain the effect of inhibiting a decrease in heat exchange efficiency while obtaining the effect of inhibiting adhesion of scale in the present invention.

Embodiment 2

[0053] FIG. 7 is an example of a configuration diagram of a circulation pipe system according to Embodiment 2. The basic configuration of the circulation pipe system according to Embodiment 2 is the same as that of the circulation pipe system according to Embodiment 1, and thus only the differences will be described. In FIG. 7, an example of the circulation pipe system according to Embodiment 2 is characterized in that, in the configuration of the circulation pipe system according to Embodiment 1, a temperature measuring unit 25 for measuring the temperature of the carbon dioxide concentration unit 18 is provided to be connected to the carbon dioxide concentration unit 18 and is connected to the controller 24. In the circulation pipe system having the above configuration, it is possible to estimate the amount of adsorption by an adsorbent that is provided in the carbon dioxide concentration unit 18 and adsorbs carbon dioxide, by measuring the temperature of the carbon dioxide concentration unit 18, thereby efficiently switching between the valve operation state A and the valve operation state B.

[0054]  When the adsorbent adsorbs and desorbs carbon dioxide, enthalpy change occurs. General adsorption involves heat generation, and general desorption involves heat reception. That is, it is possible to estimate the amount of adsorption of carbon dioxide by the adsorbent, by the temperature measuring unit 25 measuring the temperature of the carbon dioxide concentration unit 18. In the valve operation state A, carbon dioxide is adsorbed by the adsorbent in the carbon dioxide concentration unit 18, and the temperature of the carbon dioxide concentration unit 18 rises due to heat of adsorption. The temperature rise rate at this time is considered to depend on the rate of adsorption (amount of adsorption) of carbon dioxide. Thus, as the coverage ratio of the adsorbent increases to approach the adsorption saturation amount, the temperature rise rate decreases, and the temperature no longer rises when the adsorbent becomes saturated (when the valve operation state A is continued in a state where the adsorbent is saturated, the rate of adsorption and the rate of desorption are considered to be equal to each other, further adsorption hardly occurs, and thus the temperature gradually decreases due to natural cooling). The controller 24 may calculate a temperature rise rate from the temperature measured by the temperature measuring unit 25, and may make a switch from the valve operation state A to the valve operation state B during a period from the time when the temperature rise rate starts decreasing to the time when the temperature rise rate reaches zero.

[0055] On the other hand, in the valve operation state B, carbon dioxide is desorbed from the adsorbent in the carbon dioxide concentration unit 18 that has adsorbed carbon dioxide, and the temperature of the carbon dioxide concentration unit 18 decreases due to heat of desorption. The temperature decrease rate at this time is considered to depend on the rate of desorption (the amount of desorption) of carbon dioxide, and, as adsorbed carbon dioxide is desorbed to approach zero, the temperature decrease rate decreases and reaches zero soon. The controller 24 may calculate a temperature decrease rate from the temperature measured by the temperature measuring unit 25, and may make a switch from the valve operation state B to the valve operation state A during a period from the time when the temperature decrease rate starts decreasing to the time when the temperature decrease rate reaches zero.

[0056]  By the operation method as described above, it is possible to perform an adsorption process and a desorption process without waste, and it becomes possible to efficiently switch the valve operation states. It is needless to say that it is possible to optionally set the times of the valve operation state A and the valve operation state B on the basis of the filled amount of the adsorbent, the capacity of the carbon dioxide concentration unit 18, and the volume space of the negative pressure generating unit 22.

[0057] FIG. 12 is an example of a configuration diagram of the circulation pipe system according to Embodiment 2 of the present invention. As shown in FIG. 12, two temperature measuring units, a temperature measuring unit 25a that is present in the interior of the carbon dioxide concentration unit 18 filled with the adsorbent and that is connected in the vicinity of the discharge pipe 16 side, and a temperature measuring unit 25b that is present in the interior of the carbon dioxide concentration unit 18 filled with the adsorbent and that is connected in the vicinity of the suction pipe 21 side, may be connected. For example, in the case of the example of Embodiment 2, the temperature measuring unit 25a is connected in the adsorbent at the vertically upper side, and the temperature measuring unit 25b is connected in the adsorbent at the vertically lower side. When the temperature measuring units 25a and 25b are connected at such positions, it is possible to directly measure the temperature at the adsorbent rear stage close to the discharge pipe 16, and thus it is possible to more efficiently infer the saturation state of the adsorbent. As described in Embodiment 1, when the amount of carbon dioxide adsorbed by the adsorbent located close to the first opening-closing valve 9 is made constantly larger than or equal to the amount of carbon dioxide adsorbed by the adsorbent located far from the first opening-closing valve 9, heat of adsorption occurs from the adsorbent located close to the first opening-closing valve 9, and with approaching the adsorption saturation amount, heat of adsorption occurs in the adsorbent located far from the first opening-closing valve 9. Thus, the temperature measuring unit 25a only needs to measure heat of adsorption at the adsorbent rear stage, calculation by the controller 24 becomes unnecessary, and it is possible to make a switch from the valve operation state A to the valve operation state B at the time when temperature rise is detected.

[0058] Meanwhile, the temperature measuring unit 25b is able to directly measure the temperature at the adsorbent front stage, and thus it is possible to more efficiently infer the carbon dioxide desorption state at the adsorbent. As described in Embodiment 1, in the valve operation state B, carbon dioxide adsorbed by the adsorbent close to the first opening-closing valve 9 (at the adsorbent front stage in this case) is initially sucked (desorbed). When only heat of desorption at the adsorbent front stage is detected, calculation by the controller 24 is unnecessary, and it is possible to make a switch from the valve operation state B to the valve operation state A at the time when temperature decrease is detected.

[0059] Only the temperature measuring unit 25 may be connected, a switch may be made from the valve operation state A to the valve operation state B, and a switch from the valve operation state B to the valve operation state A may be controlled on the basis of time as described in Embodiment 1. That is, the first opening-closing valve 9, the second opening-closing valve 19, the third opening-closing valve 17, and the air-sending pump 20 are controlled by the controller 24 such that the operation time t2 is, for example, about 5 to 20 seconds, and a switch is made from the valve operation state B to the valve operation state A. By the operation method as described above, it is possible to efficiently perform an adsorption process and switch the valve operation states without needing calculation by the controller 24. It is needless to say that it is possible to optionally set the time of the valve operation state A on the basis of the filled amount of the adsorbent, the capacity of the carbon dioxide concentration unit 18, and the volume space of the negative pressure generating unit 22.

Embodiment 3

[0060] FIG. 8 is an example of a configuration diagram of a circulation pipe system according to Embodiment 3. The basic configuration of the circulation pipe system according to Embodiment 3 is the same as those of the circulation pipe systems according to Embodiment 1 and Embodiment 2, and thus only the differences will be described. In FIG. 8, an example of the circulation pipe system according to Embodiment 3 is characterized in that, in the configurations of the circulation pipe systems according to Embodiment 1 and Embodiment 2, a heating unit 26 for heating the carbon dioxide concentration unit 18 is provided and connected to the controller 24.

[0061]  In the circulation pipe system having the above configuration, it is possible to heat the carbon dioxide concentration unit 18 in the valve operation state B, and it is possible to promote desorption of carbon dioxide in the carbon dioxide concentration unit 18. As described in Embodiment 2, when carbon dioxide is desorbed, the temperature of the adsorbent decreases. Due to the temperature decrease, the carbon dioxide desorption rate decreases. In Embodiment 3, in the valve operation state B, it is possible to inhibit a decrease in the desorption rate by heating the carbon dioxide concentration unit 18 using the heating unit 26, and thus it is possible to inject pulsed bubbles having a steeper gradient a in a pulse waveform into the water flowing in the water flow path 6. The advantageous effects obtained by causing pulsed bubbles to flow into the water flowing in the water flow path 6 are as described in Embodiment 1.

Embodiment 4

[0062] FIG. 9 is an example of a configuration diagram of a carbon dioxide-containing water supply system according to Embodiment 4. The basic configuration of the carbon dioxide supply system according to Embodiment 4 is the same as those of the circulation pipe systems according to Embodiment 1, Embodiment 2, and Embodiment 3, and thus only differences will be described. In FIG. 9, an example of the carbon dioxide supply system according to Embodiment 4 is characterized in that, in the configurations of the circulation pipe systems according to Embodiment 1, Embodiment 2, and Embodiment 3, the bubble injection device 10, the carbon dioxide supply device 8, the controller 24, and a diluted water pipe 27 are provided at the hot water supply pipe 13 through which hot water accumulated (stored) in the hot water storage tank 14 flows to the outside.

[0063] Normally, operation is performed such that the temperature of hot water stored in a hot water supply tank is about 40 to 90°C, and, before the hot water flows to the outside, the hot water and tap water are mixed such that the temperature reaches the temperature desired at a use point, and the mixed water is caused to flow out (supplied) to an outside use point. Examples of the use point include a bath tub, a shower, a lavatory, a kitchen, and a floor heating. According to Embodiment 4, it is possible to supply carbon dioxide to hot water (supply water) to be supplied to the use point.

[0064]  As described in Embodiment 1, as the bubble injection device 10, for example, a gas introduction pipe that causes gas to flow into a liquid, a diffuser pipe that introduces gas into a liquid by dispersing the gas into the liquid, diffused air balls and a porous nozzle, a spray nozzle that mixes and sprays gas and a liquid, and an ejector that creates a mixed flow of gas and a liquid may be used. In Embodiment 4, an example of the present invention will be described with reference to an example in which an ejector is used as the gas-liquid mixing unit 23.

[0065] The bubble injection device 10 only needs to be provided on the hot water supply pipe 13, and may be provided at the upstream side or the downstream side of a portion where the hot water supply pipe 13 is joined to the diluted water pipe 27. According to Henry's law, when the bubble injection device 10 is provided at the downstream side at which the water temperature is lower, the advantageous effects of the present invention are higher than when the bubble injection device 10 is provided at the upstream side at which the water temperature is higher, as the amount of carbon dioxide (gas) dissolved increases. When the bubble injection device 10 is provided close to an outlet of a bath tub, a shower, a lavatory, a kitchen, a floor heating, or other points, which are use points, the operation state of the carbon dioxide supply system is selectable for each use point, and thus convenience is further enhanced. It is needless to say that the operation state (activation or deactivation) of the carbon dioxide supply system may be selected by using an external operation panel (not shown) of the carbon dioxide supply system.

[0066] FIG. 10 is an example of a configuration diagram of the carbon dioxide-containing water supply system according to Embodiment 4 of the present invention. As shown in FIG. 10, the bubble injection device 10 may be provided on the diluted water pipe 27. The temperature of tap water flowing in the diluted water pipe 27 is lower than the temperature of water flowing in the hot water supply pipe 13, and thus a more amount of carbon dioxide (gas) is able to dissolve according to Henry's law. Due to this configuration, the effect of inhibiting adhesion of scale as described in Embodiment 1 is higher.

[0067] In the carbon dioxide-containing water supply system of Embodiment 4, it is needless to say that the configurations of and the operation methods for the bubble injection device 10, the carbon dioxide supply device 8, and the controller 24 are preferably the same as those in Embodiment 1, Embodiment 2, and Embodiment 3.

[0068] In the carbon dioxide supply system having the above configuration, as it is possible to supply hot water containing carbon dioxide, improvement of health status, such as efficacy due to blood flow acceleration and efficacy directly to skin, which are obtained with carbonated spring, is possible in addition to the scale adhesion inhibition effect. Specifically, it is considered to be possible to improve shoulder stiffness, lower back pain, recovery from fatigue, feeling of cold, neuralgia, rheumatism, hemorrhoid, miliaria, rough skin, cracks, chaps, eczema, and pimples. In addition, in the case of use for bath water for a bath tub, comfortability at the time of bath such as warm bath effect is considered to improve.

Embodiment 5

[0069] FIG. 11 is an example of a configuration diagram of a carbon dioxide-containing water supply system according to Embodiment 5. The basic configuration of the carbon dioxide supply system according to Embodiment 5 is the same as those of Embodiment 1, Embodiment 2, Embodiment 3, and Embodiment 4, and thus only differences will be described. In FIG. 11, an example of the carbon dioxide supply system according to Embodiment 5 is characterized in that, in the configurations of the circulation pipe systems according to Embodiment 1, Embodiment 2, Embodiment 3, and Embodiment 4, a heating pipe 28, a reheating heat exchanger 29, circulation pumps 30 and 31, a reheating circulation pipe 32, and a bath tub 33 are provided.

[0070] In Embodiment 5, a water heating function to change water into hot water by heat supplied by a cooling energy cycle of the circulation pipe system and store the hot water in the hot water storage tank 14, a hot water supply function to supply hot water to the bath tub 33, and a reheating function to reheat bath water in the bath tub 33 are provided. The heating pipe 28 for supplying hot water to the reheating heat exchanger 29 and the circulation pump 30 for circulating hot water are provided to the hot water storage tank 14. The reheating circulation pipe 32 for reheating is connected to the reheating heat exchanger 29. The bubble injection device 10 for injecting bubbles is mounted on the reheating circulation pipe 32.

[0071] The position at which the bubble injection device 10 is mounted is not limited to this example, and the advantageous effects of Embodiment 5 are obtained even when the bubble injection device 10 is provided at the upstream or downstream side of the reheating heat exchanger 29. When the bubble injection device 10 is provided at the downstream side of the reheating heat exchanger 29, it is possible to reduce the secondary side pressure of the bubble injection device 10, and thus it is possible to more efficiently inject bubbles. In other words, it is possible to inject more bubbles at the same electric power (power saving operation).

[0072] A bath water heater is normally provided with a reheating function, to increase the temperature of bath water in the bath tub when the bath water has cooled to become unsuited for bath. Here, bath water is heated by a reheating heat exchanger.

[0073] Next, operation of injecting bubbles containing carbon dioxide to the reheating heat exchanger 29 and the reheating circulation pipe 32 connected to the reheating heat exchanger 29 will be described. In the case of reheating bath water in the bath tub 33, hot water is guided from the hot water storage tank 14 through the heating pipe 28 to the reheating heat exchanger 29 by the circulation pump 30. Meanwhile, the bath water in the bath tub 33 is sent through the reheating circulation pipe 32 to the reheating heat exchanger 29 by the circulation pump 31. In the reheating heat exchanger 29, heat is exchanged between the hot water from the hot water storage tank 14 and the bath water, and thus the hot water turns into low-temperature water due to the heat received by the bath water and is returned through the heating pipe 28 to the hot water storage tank. Meanwhile, the bath water receives the heat from the hot water to have a higher temperature and is returned through the reheating circulation pipe 32 to the bath tub 33. By repeating this operation, the temperature of the reheated bath water becomes suitable for bath.

[0074] In Embodiment 5, an example of a counter flow reheating heat exchanger in which the flow direction of hot water and the flow direction of bath water are opposite to each other is shown in FIG. 11, but the present invention is not limited to this example, and a parallel flow reheating heat exchanger in which hot water and bath water flow in parallel may be used. In addition, an example in which bath water flows from the vertically lower side of the reheating heat exchanger toward the vertically upper side of the reheating heat exchanger is shown in FIG. 11, but the present invention is not limited to this example, and a reheating heat exchanger in which bath water flows from the vertically upper side of the reheating heat exchanger toward the vertically lower side of the reheating heat exchanger may be used.

[0075] The reheating heat exchanger 29 serves to heat water by exchanging heat between the refrigerant and water. For example, a plate heat exchanger, a multi-tube heat exchanger, a double-tube heat exchanger, a micro channel heat exchanger, a boiler heat exchanger, or a twisted-tube heat exchanger may be used as the reheating heat exchanger 29. In this case, bubbles containing carbon dioxide are injected by the bubble injection device 10 provided on the reheating circulation pipe 32, so that it is possible to inject pulsed bubbles into the bath tub 33. Operation of the bubble injection device 10, the carbon dioxide supply device 8, and the controller 24 may be performed as described in Embodiment 1, Embodiment 2, and Embodiment 3.

[0076] In the carbon dioxide supply system having the above configuration, as it is possible to supply hot water containing carbon dioxide to the bath tub 33, improvement of health status, such as efficacy due to blood flow acceleration and efficacy directly to skin, which are obtained with carbonated spring, is possible. Specifically, it is considered to be possible to improve shoulder stiffness, lower back pain, recovery from fatigue, feeling of cold, neuralgia, rheumatism, hemorrhoid, miliaria, rough skin, cracks, chaps, eczema, and pimples. In addition, comfortability at the time of bath such as warm bath effect is also considered to improve. In Embodiment 5, it is possible to supply pulsed bubbles containing carbon dioxide to the bath tub 33 by using the reheating circulation pipe 32 during bath, and thus the above advantageous effects are higher. In addition, it is possible to intermittently supply (supply in a rhythmical manner) pulsed bubbles containing carbon dioxide, and thus it is considered to be possible to stimulate the sensitivity of a bather to improve comfortable feeling during bath.

Reference Signs List

[0077] 

1

air heat exchanger

2

refrigerant flow path

3

compressor

4

fan

5

pressure reducing unit

6

water flow path

7

water heat exchanger

8

carbon dioxide supply device

9

first opening-closing valve

10

bubble injection device

10b

pulsed bubble injection device

11

water pump

12

degassing valve

13

hot water supply pipe

14

hot water storage tank

15

water supply pipe

16

discharge pipe

17

third opening-closing valve

18

carbon dioxide concentration unit

19

second opening-closing valve

20

air-sending pump

21

suction pipe

22

negative pressure generating unit

23

gas-liquid mixing unit

24

controller

25

temperature measuring unit

25a

temperature measuring unit

25b

temperature measuring unit

26

heating unit

27

diluted water pipe

28

heating pipe

29

reheating heat exchanger

30

circulation pump

31

circulation pump

32

reheating circulation pipe

33

bath tub

100

water heater

Claims

1. A circulation pipe system, comprising:

- a circulation pipe through which water is circulated between a first device and a second device;

- a bubble injection device configured to inject bubbles into the water;

- a carbon dioxide supply device connected to the bubble injection device and configured to supply carbon dioxide for generating the bubbles; and

- a controller configured to control the bubble injection device and the carbon dioxide supply device such that the bubbles containing the carbon dioxide are intermittently injected to the water circulating through the circulation pipe.

2. The circulation pipe system of claim 1,
wherein the bubble injection device includes

- a negative pressure generating unit connected to the carbon dioxide supply device and configured to generate a negative pressure to the carbon dioxide supplied,

- a gas-liquid mixing unit configured to mix the carbon dioxide sucked into the negative pressure generating unit by use of the negative pressure, into the water, and

- a first opening-closing valve connected a point between the negative pressure generating unit and the carbon dioxide supply device, opening and closing of the first opening-closing valve being controlled by the controller.

3. The circulation pipe system of claim 1 or 2,
wherein the carbon dioxide supply device includes

- an air-sending pump configured to send air in an atmosphere,

- a carbon dioxide concentration unit configured to adsorb carbon dioxide contained in the air, as the carbon dioxide to be supplied,

- a second opening-closing valve connected a point between the carbon dioxide concentration unit and the air-sending pump, opening and closing of the second opening-closing valve being controlled by the controller,

- a discharge pipe for discharging the air sent to the carbon dioxide concentration unit, and

- a third opening-closing valve connected a point between the carbon dioxide concentration unit and the discharge pipe, opening and closing of the third opening-closing valve being controlled by the controller.

4. The circulation pipe system of claim 3,
wherein the controller is configured to perform control such that a first valve operation state and a second valve operation state are alternately repeated,
the first valve operation state being a state in which a first opening-closing valve is closed and the second opening-closing valve and the third opening-closing valve are opened,
the second valve operation state being a state in which the first opening-closing valve is opened and the second opening-closing valve and the third opening-closing valve are closed.

5. The circulation pipe system of claim 4,
wherein the controller is configured to perform control such that duration of the second valve operation state is 5 to 20 seconds and duration of the first valve operation state is longer than three times and shorter than 360 times the duration of the second valve operation state.

6. The circulation pipe system of claim 3,
further comprising a temperature measuring unit configured to measure a temperature of the carbon dioxide concentration unit,
wherein the controller is configured to control opening and closing of the third opening-closing valve on a basis of the temperature measured by the temperature measuring unit.

7. A carbon dioxide-containing water supply system, comprising the circulation pipe system of any one of claims 1 to 6,
wherein the first device comprises a heat exchanger configured to heat the water,
the second device comprises a hot water storage tank configured to store the water, and
the carbon dioxide-containing water supply system further comprises a hot water supply pipe through which the water stored in the hot water storage tank is supplied.

8. The carbon dioxide-containing water supply system of claim 7,
wherein the carbon dioxide supply device is configured to supply the carbon dioxide to the water to be supplied through the hot water supply pipe.

9. A carbon dioxide-containing water supply system, comprising:

- the circulation pipe system of claim 1; and

- a water pipe through which water is supplied,

wherein the bubble injection device is connected to the water pipe and is configured to inject the bubbles containing the carbon dioxide into the water pipe.

10. A carbon dioxide-containing water supply system, comprising:

- the circulation pipe system of claim 1; and

- a bath tub,

wherein the bubble injection device is connected to the bath tub and is configured to inject the bubbles containing the carbon dioxide into the bath tub.

Drawing