Storage-type hot water supply system

Abstract

To provide a hot water storage type water heater which can prevent a freeze of a heating bypass pipe by an inexpensive constitution, and can maintain the inside of the hot water storage type water heater at safe pressure by discharging comparatively-low temperature hot water from a pressure release valve 38.SOLUTION: A hot water storage type water heater comprises: a hot water storage tank 2 for storing hot water; heating means 16 for heating hot water in the hot water storage tank 2; a heating going-pipe 17 for sending the hot water to the heating means 16 from a lower part of the hot water storage tank 2; a circulation pump 20 arranged in the middle of the heating going-pipe 17; a heating return pipe 18 for sending the hot water which is heated by the heating means 16 to an upper part of the hot water storage tank 2; a heating bypass path which is branched from the heating return pipe 18, and merged with a water supply pipe 4; a heating bypass valve 22 for switching a flow of the hot water to the heating bypass path from the heating return pipe 18; and a pressure release valve 38 for releasing pressure to the outside of the hot water storage type water heater when the pressure in the hot water storage type water heater exceeds prescribed pressure. The pressure release valve 38 is arranged in the heating bypass path.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This invention relates to a storage - type water supply apparatus having heating means.

Background Art

[0002] Conventionally, in this type of storage - type water supply apparatus, a storage tank and heating means are provided, and a heating forward pipe for sending water from the lower part of the storage tank to the heating means and a heating return pipe for sending water from the heating means to the storage tank are used to connect the storage tank and the heating means to form a heating circulation circuit. A circulation pump provided in the heating circulation circuit circulates the hot water in the storage tank and the heating means to heat the water in the storage tank. The hot water boiled in the boiling - up operation is stored in the storage tank, and hot water at a set temperature is supplied while mixing the high - temperature water and the supply water in the storage tank sequentially to achieve economical water supply.

[0003] Also, there is a storage - type water supply apparatus in which a heating bypass pipe branched from the heating return pipe is connected to the water supply pipe, and a bypass circulation path passing through the heating bypass pipe shares a part of the water supply path of the water supply pipe. In order to prevent freezing of the water supply pipe and the heating bypass pipe, an anti - freezing operation is known in which hot water is circulated to the heating bypass pipe side during the boiling - up operation and flows into the lower part of the storage tank (for example, Patent Document 1).

[0004] Also, by disposing a pressure - relief valve that opens when the pressure in the storage - type water supply apparatus exceeds a predetermined pressure at a position where cold water flows, when discharging the pressure outside the storage - type water supply apparatus, cold water is discharged, and it has been known to prevent the high - temperature water stored in the storage tank from being discharged outside the storage - type water supply apparatus (for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] However, as described in Patent Document 1, when high-temperature water heated by a heat pump heating means is circulated to the heating bypass pipe side and flows into the bottom of the hot water storage tank for freeze prevention during the boiling operation, the accumulation of high-temperature water at the bottom of the hot water storage tank causes the inlet water temperature to rise, resulting in a decrease in boiling efficiency.

[0007] Furthermore, while it is possible to prevent the discharge of high-temperature water from the hot water storage tank by arranging a pressure relief valve in the water supply pipe as in Patent Document 2, in a hot water storage type hot water supply system equipped with a heating bypass pipe, when the pressure is released by the pressure relief valve during the boiling operation, no hot water flow occurs in the heating bypass pipe, and there is a problem that it may freeze unless an anti-freeze operation as in Patent Document 1 is performed. [Means for solving the problem]

[0008] According to the present invention, a hot water storage type hot water supply system includes a hot water storage tank for storing hot water, a heating means for heating the hot water in the hot water storage tank, a hot water outlet pipe connected to the upper part of the hot water storage tank, a water supply pipe connected to the lower part of the hot water storage tank, a water supply bypass pipe branching off from the water supply pipe and joining with the hot water outlet pipe, a hot water supply pipe that mixes the high-temperature water in the hot water outlet pipe with the water supply from the water supply bypass pipe and sends the hot water to the destination, a heating supply pipe that sends the hot water from the lower part of the hot water storage tank to the heating means, and the heating means The hot water supply system includes a circulation pump installed in the middle of the heat supply pipe, a heating return pipe that sends the hot water heated by the heating means to the top of the hot water storage tank, a heating bypass path that branches off from the heating return pipe and merges with the water supply pipe, a heating bypass valve that switches the flow of the hot water from the heating return pipe to the heating bypass path, and a pressure relief valve that releases pressure to the outside of the hot water supply system when the pressure inside the hot water storage system exceeds a predetermined pressure, the pressure relief valve being installed in the heating bypass path.

[0009] Furthermore, the pressure relief valve is positioned closer to the inlet branching point where the heating bypass path branches off from the heating return pipe than to the outlet branching point where the heating bypass path merges with the water supply pipe. [Effects of the Invention]

[0010] According to this invention, it is possible to prevent the heating bypass pipe from freezing with an inexpensive configuration, and to maintain a safe pressure inside the hot water storage system by discharging relatively low-temperature hot water from the pressure relief valve. [Brief explanation of the drawing]

[0011] [Figure 1] A schematic diagram showing an embodiment of this invention. [Figure 2] A flowchart illustrating the operation of the water heating mechanism of this invention. [Figure 3] A schematic diagram showing the arrangement of the pressure relief valve in this embodiment of the invention. [Modes for carrying out the invention]

[0012] Next, a storage-type hot water supply system according to one embodiment of this invention will be described based on the drawings. 1 is a hot water storage tank unit, which includes a hot water storage tank 2 for storing hot water, a hot water outlet pipe 3 connected to the top of the hot water storage tank 2, a water supply pipe 4 connected to the bottom of the hot water storage tank 2, a hot water mixing valve 6 for mixing high-temperature water from the hot water outlet pipe 3 and low-temperature water from a water supply bypass pipe 5 branched from the water supply pipe 4, and a hot water temperature sensor 8 and a hot water flow sensor 9 for detecting the hot water flow rate, which are installed in the hot water supply pipe 7 connected downstream of the hot water mixing valve 6.

[0013] 10 is a heat pump unit, comprising a heat pump type heating means 16 consisting of a compressor 11, a water refrigerant heat exchanger 12 as a condenser, an electronic expansion valve 13, and an outdoor fan 14, and an air heat exchanger 15 as an evaporator that exchanges heat with air; a circulation pump 20 that circulates the hot water in the hot water storage tank 2 to the heating means 16 via a heating circulation circuit 19 consisting of a heating supply pipe 17 and a heating return pipe 18; and a heat pump control unit 21 that controls the driving of these. Carbon dioxide is used as the refrigerant in the heating means 16, forming a supercritical heat pump cycle. Furthermore, because carbon dioxide is used as the refrigerant, it is possible to heat low-temperature water to a high temperature of approximately 90°C without an electric heater.

[0014] Here, the water-refrigerant heat exchanger 12 employs a counterflow system in which the refrigerant and the hot water in the storage tank 2, which is the water to be heated, flow in opposite directions. In a supercritical heat pump cycle, the refrigerant remains in a supercritical state and condenses during heat exchange, so the water to be heated can be efficiently heated to a high temperature. By controlling the expansion valve 13 or compressor 11 so that the temperature difference between the inlet temperature of the water to be heated and the outlet temperature of the refrigerant remains constant, it is possible to heat the water to be heated with a very good COP (energy efficiency) when the inlet temperature of the water to be heated and the water-refrigerant heat exchanger 12 is at a low temperature of about 5 to 20°C.

[0015] Furthermore, a heating bypass valve 22 is provided in the heating return pipe 18. When preventing freezing, the heating bypass valve 22 is switched to communicate with the heating bypass pipe 23, which is a heating bypass path connected to the water supply pipe 4 at the bottom of the hot water storage tank 2. This prevents freezing by creating a short-circuit circulation using the lower part of the hot water storage tank 2. The heating bypass valve 22 is located at the branching point from the heating return pipe 18 to the heating bypass pipe 23.

[0016] Also, when circulating warm water that is not sufficiently heated at the initial stage of heating by the heating means 16, the hot water is not returned to the upper part of the hot water storage tank 2, but is returned to the lower part of the hot water storage tank 2 through a bypass circulation path via the heating bypass pipe 23. When circulating the sufficiently heated hot water thereafter, the heating bypass valve 22 is switched to the upper side of the hot water storage tank 2.

[0017] 24 is a control device composed of a microcomputer or the like, which controls the heat pump control unit 21 to perform temperature control of hot water supply such as boiling-up operation and boiling-up additional operation of the hot water storage tank 2 by the heating circulation circuit 19, and operation control such as hot water filling and reheating of the bathtub, and heat preservation.

[0018] Also, the control device 24 is provided with heating bypass valve control means 25 for controlling the opening degree of the heating bypass valve 22. Specifically, the heating bypass valve control means 25 switches the heating bypass valve 22 to the heating bypass pipe 23 side and is in a first state where it is switched to communicate with the water supply pipe 4 at the lower part of the hot water storage tank 2, and a second state where the heating bypass valve 22 is communicated with the upper side of the hot water storage tank 2.

[0019] Also, the control device 24 is provided with rotation speed control means 26 for controlling the rotation speed of the circulation pump and boiling-up operation control means 27 for controlling the boiling-up operation described later.

[0020] At the start of this boiling operation, the refrigerant in the heating means 16 is not sufficiently heated, and thus the water at the bottom of the hot water storage tank 2 flowing in from the heating forward pipe 17 cannot be boiled to the boiling target temperature. Therefore, the rotation speed control means 26 sets the rotation speed of the circulation pump 20 to less than a predetermined rotation speed (less than this predetermined rotation speed is referred to as a low rotation state and will be denoted as a low rotation state in the following text). The boiling operation control means 27 drives the circulation pump 20 to perform the boiling operation. When the elapsed time from the start of the boiling operation, which is the end condition of the low rotation state, is a predetermined time or more, or when the outlet temperature sensor 35 in the middle of the heating return pipe 18 reaches a predetermined temperature or more, the rotation speed control means 26 sets the rotation speed of the circulation pump 20 to the predetermined boiling rotation speed and performs the boiling operation. Also, the predetermined rotation speed here is higher than that in the low rotation state, lower than the predetermined boiling rotation speed, and is a rotation speed at which at least the circulation of the boiling operation does not stop due to the influence of the water supply pressure by hot water supply.

[0021] Also, similarly to the above, at the start of the boiling operation, the refrigerant in the heating means 16 is not sufficiently heated, and thus the water at the bottom of the hot water storage tank 2 flowing in from the heating forward pipe 17 cannot be boiled to the boiling target temperature. Therefore, the heating bypass valve control means 25 sets the heating bypass valve 22 to the first state and then performs boiling, returning the boiled hot water to the bottom of the hot water storage tank 2. After that, when the above end condition of the low rotation state is reached, the heating bypass valve 22 is set to the second state to perform the boiling operation.

[0022] Furthermore, the remote controller 28 has a temperature setting switch 29 for setting the hot water supply set temperature, a water filling switch 30 for instructing water filling to the bathtub, and a 31 for setting the water filling amount. Further, it is provided with a remote control unit 33 composed of a dot matrix type fluorescent display tube as the display unit 32 and a microcomputer that controls this display unit 32 and communicates with the control device 24.

[0023] Furthermore, the water-refrigerant heat exchanger 12 of the heating circulation circuit 19 is equipped with an inlet water temperature sensor 34 on the inlet side to detect the inlet water temperature, and an outlet temperature sensor 35 on the outlet side to detect the hot water temperature after heating. Multiple hot water temperature sensors 36 are provided in the hot water storage tank 2 to detect the temperature of the hot water stored in the tank 2, and the heating operation is terminated when the lower hot water temperature sensor 36 continuously detects the target heating temperature. In this embodiment, the heating operation is terminated when the hot water temperature sensor 36 continuously detects the target heating temperature, but the amount of hot water stored can be calculated from the hot water temperature detected by the hot water temperature sensor 36, and the heating operation may be terminated when the target amount of hot water stored is reached during the heating operation.

[0024] 37 is a pressure reducing valve installed in the water supply pipe 4.

[0025] 38 is a pressure relief valve installed in the heating bypass pipe 23, which releases pressure in the hot water storage tank 2 and the heating circulation circuit 19.

[0026] This pressure relief valve 38 is designed to open when the hot water in the hot water storage tank 2 and the heating circulation circuit 19 becomes hot during the heating operation, causing the pressure inside the hot water storage system to rise and exceed a predetermined pressure. When this pressure exceeds a predetermined level, the valve opens, and the hot water is discharged outside the hot water storage system along with the pressure.

[0027] Furthermore, 39 is a hot water supply valve that connects the hot water supply pipe 40 to the bathtub and supplies hot water to the bathtub, 41 is a bath temperature sensor that detects the temperature of the bath water supplied to the bath, and 42 is a bath flow sensor that detects the flow rate that has passed through the hot water supply pipe 40.

[0028] Next, I will explain the water heating operation. When the amount of heat stored in the hot water decreases or when there is a request to heat water during the nighttime hours, the heating bypass valve control means 25 sets the heating bypass valve 22 to a first state, communicating with the lower side of the hot water storage tank 1. The control device 24 drives the circulation pump 20 located in the middle of the piping connecting the hot water storage tank 2 and the heating means 16 to draw water up from the lower part of the hot water storage tank 2, heat it with the heating means 16, and return it to the lower part of the hot water storage tank 32. Then, when the aforementioned termination condition of low rotation state is reached, the control device 25 sets the heating bypass valve 22 to a second state, communicating with the upper side of the hot water storage tank 2, and continues the operation of returning the water to the upper part of the hot water storage tank 2, thereby gradually heating the water in the hot water storage tank 2 to a high temperature.

[0029] Next, the operation of the embodiment when hot water supply operation is performed during the water heating operation will be explained in detail based on the flowchart in Figure 2. When the amount of stored hot water decreases or there is a request to heat water during the nighttime hours, and the heating operation control means 27 starts heating water (S1 is Yes), the heating bypass valve control means 25 sets the heating bypass valve 22 to a first state in communication with the heating bypass pipe 23 side (S2), the rotation speed control means 26 sets the rotation speed of the circulation pump 20 to the low rotation state (less than a predetermined rotation speed) (S3), and the heating operation control means 27 drives the circulation pump 20.

[0030] Then, if the termination condition for the low rotation state is met (S4 is Yes), the heating bypass valve control means 25 sets the heating bypass valve 22 to a second state that communicates with the upper side of the hot water storage tank 2 (S5), the rotation speed control means 26 sets the rotation speed of the circulation pump 20 to a predetermined boiling rotation speed (S6), and the boiling operation control means 27 continues the boiling operation.

[0031] Subsequently, the lower hot water storage temperature sensor 36 continuously detects the target temperature for heating (S7 is Yes), and the heating operation is completed (S8).

[0032] During the heating operation, the water in the hot water storage unit becomes hot, and the pressure inside the hot water storage unit increases. Therefore, during the heating operation, the hot water is discharged from the pressure relief valve 38 along with the pressure.

[0033] Next, I will explain the hot water supply operation. When the hot water tap is opened, water is supplied from the water supply pipe 4, flows into the lower part of the hot water storage tank 2, and passes through the water supply bypass pipe 5. The hot water pushed out from the upper part of the hot water storage tank 2 and the water supplied from the water supply bypass pipe 5 are mixed by the hot water mixing valve 6, and the hot water is supplied from the hot water tap after being adjusted so that the set temperature of the hot water supply and the temperature detected by the hot water supply temperature sensor 8 are the same.

[0034] Next, we will explain the process of filling the bathtub with hot water. When the hot water filling switch 30 on the remote control 28 is pressed, the control device 24 opens the hot water filling valve 39, supplying water from the water supply pipe 4. The water flows into the lower part of the hot water storage tank 2 and through the water supply bypass pipe 5. The hot water pushed out from the upper part of the hot water storage tank 2 and the water supplied through the water supply bypass pipe 5 are mixed by the hot water mixing valve 6, and the water is adjusted so that the bath set temperature and the temperature detected by the bath temperature sensor 41 are the same. This water then flows into the bathtub, and the filling process begins. The bath flow sensor 42 detects the flow rate, and when the total accumulated flow rate reaches the set amount, the control device 24 closes the hot water filling valve 39 to complete the filling process.

[0035] Next, the detailed arrangement of the pressure relief valve 38 will be explained based on Figures 1 and 3. The point where the heating bypass valve 22 provided in the heating return pipe 18 branches off to the heating bypass pipe 23 is defined as the inlet side branching point a, and the point where the heating bypass pipe 23 merges with the water supply pipe 4 is defined as the outlet side merging point b.

[0036] A pressure relief valve 38 is positioned in the middle of the heating bypass pipe 23, with the inlet branching point a being upstream and the outlet confluence point b being downstream.

[0037] The flow of hot and cold water when a pressure relief valve 38 is located in the heating bypass pipe 23 will be explained. When the pressure inside the hot water storage system rises and the pressure relief valve 38 opens, if the heating bypass valve 22 is in the second state, no water flow occurs between the inlet branch position a and the pressure relief valve 38, but the water between the pressure relief valve 38 and the outlet confluence position b is discharged outside the hot water storage system along with the pressure.

[0038] Then, as the hot and cold water between the pressure relief valve 38 and the outlet confluence point b is discharged, water is first supplied from the water supply pipe 4 near the outlet confluence point b. At this time, if the pressure inside the hot water storage system exceeds a predetermined pressure, the water supplied from the water supply pipe 4 is discharged outside the hot water storage system along with the pressure. This water supply from the water supply pipe 4 continues until the pressure inside the hot water storage system falls below the predetermined pressure, preventing the pressure inside the hot water storage system from rising and generating a flow of hot and cold water in the heating bypass pipe 23.

[0039] Furthermore, when the hot water between the pressure relief valve 38 and the outlet confluence position b is discharged, and water is supplied from the water supply pipe 4 near the outlet confluence position b, the hot water inside the hot water storage tank 2 expands due to the high temperature inside the tank, and the hot water inside the tank is also discharged outside the hot water storage system along with the pressure via the water supply pipe 4. This supply of hot water inside the hot water storage tank 2 continues until the pressure inside the tank falls below a predetermined pressure, preventing damage to the hot water storage tank 2 and generating a flow of hot water in the heating bypass pipe 23.

[0040] In this way, since the pressure relief valve 38 is positioned in the middle of the heating bypass pipe 23, if the pressure inside the hot water storage system, including the hot water storage tank 2, exceeds a predetermined pressure, the pressure is discharged from the hot water storage system through the pressure relief valve 38 along with the relatively low-temperature hot water in the heating bypass pipe 23 and the water in the water supply pipe 4. As a result, high-temperature water is not discharged and lose heat, making it possible to provide a safe and low-cost hot water storage system.

[0041] Furthermore, during the heating operation, the temperature detected by the outlet temperature sensor 35 rises, so the heating bypass valve 22 does not switch to the heating bypass pipe 23 that flows into the lower part of the hot water storage tank 2. As a result, the hot water in the heating bypass pipe 23 does not move, and there is a possibility that it will freeze. However, because the pressure inside the hot water storage system also rises during the heating operation, the pressure relief valve 38 opens, causing a flow of hot water in the heating bypass pipe 23, which prevents freezing.

[0042] Furthermore, because the pressure rise during the heating operation generates a flow of hot water in the heating bypass pipe 23, it is possible to prevent the heating bypass pipe 23 from freezing in an inexpensive configuration without circulating hot water in the lower part of the hot water storage tank 2 or heating the heating bypass pipe 23 using an electric heater or the like.

[0043] Furthermore, by providing a pressure relief valve 38 in the middle of the heating bypass valve 22, it becomes unnecessary to switch the heating bypass valve 22 to the heating bypass pipe 23 side during the heating operation. This prevents the temperature at the bottom of the hot water storage tank 2 from rising, thus suppressing a decrease in heating efficiency.

[0044] Next, we will describe the case where the pressure relief valve 38 is positioned closer to the inlet branch position a than to the outlet branch position b in a heated bypass pipe 23, with the inlet branch position a being upstream and the outlet confluence position b being downstream. Preferably, the closer it is to the inlet branch position a, the better.

[0045] Thus, the closer the pressure relief valve 38 is to the inlet branch position a, the longer the distance between the outlet junction position b in the heating bypass pipe 23 and the pressure relief valve 38 becomes. This increases the length of the hot water movement, generating a larger flow of hot water and preventing freezing from the pressure relief valve 38 to the outlet junction position b.

[0046] Furthermore, if the distance between the inlet-side branch position a and the pressure relief valve 38 is short, the high-temperature water is heated by passing through the heating bypass valve 22 during the boiling operation, and the resulting heat dissipation can prevent freezing near the inlet-side branch position a.

[0047] It should be noted that the present invention is not limited to the embodiments, and modifications are permitted without changing the essence of the invention. For example, in the embodiment, a pressure relief valve 38 is provided in the heating bypass pipe 23, but the pressure relief valve 38 may be provided directly without providing a heating bypass pipe 23 between the heating bypass valve 22 and the water supply pipe 4. [Explanation of symbols]

[0048] 2. Hot water storage tank 3. Hot water outlet pipe 4 Water supply pipe 5. Water supply bypass pipe 6. Hot water mixing valve 7. Hot water pipe 16 Heating means 19 Heating circulation circuit 20 Circulation pump 22. Heating bypass valve 23. Heating bypass tube (heating bypass path) 24 Control device 25 Heating bypass valve control means 26. Rotation speed control means 27. Water heating operation control means 38 Pressure relief valve a. Entrance side branching position b Exit side merging position

Claims

1. Storage-type hot water supply systems are A hot water storage tank for storing hot water, A heating means for heating the hot water in the hot water storage tank, A hot water outlet pipe connected to the top of the hot water storage tank, A water supply pipe connected to the lower part of the hot water storage tank, A water supply bypass pipe that branches off from the aforementioned water supply pipe and merges with the aforementioned hot water outlet pipe. A hot water supply pipe that mixes the high-temperature water from the hot water outlet pipe with the water supply from the water supply bypass pipe and sends the hot water to the hot water destination, A heating supply pipe that sends the hot water from the bottom of the hot water storage tank to the heating means, A circulation pump installed in the heating supply pipe, A heating return pipe that sends the hot water heated by the heating means to the top of the hot water storage tank, A heating bypass path that branches off from the heating return pipe and merges with the water supply pipe, A heating bypass valve that switches the flow of hot water from the heating return pipe to the heating bypass path, The hot water storage type water heater is equipped with a pressure relief valve that releases the pressure outside the hot water storage type water heater when the pressure inside the hot water storage type water heater exceeds a predetermined pressure. The hot water supply system is characterized in that the pressure relief valve is provided in the heating bypass path.

2. The hot water storage type hot water supply device according to claim 1, characterized in that the pressure relief valve is provided at a position closer to the inlet branch position where the heating bypass path branches off from the heating return pipe than to the outlet branch position where the heating bypass path joins the water supply pipe.

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