Storage-type hot water supply system

Abstract

This invention provides a hot water storage system that can appropriately prevent the temperature distribution of the hot water in the storage tank from deviating significantly from the intended temperature distribution due to instant hot water operation. [Solution] The hot water storage type hot water supply system SY includes a first hot water circulation path C1 that enables instant hot water operation in which the hot water in the first return path 54 circulates back to the first outlet path 51 without passing through the hot water storage tank 1; a heat exchanger 3 through which the hot water in the first hot water circulation path C1 passes through the secondary side area 3b; a second hot water circulation path C2 for instant hot water heating that enables hot water circulation in which, when driven by a second pump P2, the hot water from the hot water storage tank 1 is supplied to the primary side area 3a of the heat exchanger 3 via the second outlet path 62 and then returned to the hot water storage tank 1 via the second return path 63; and a hot water flow rate changing means Vc that can change the hot water flow rate Qc of the second hot water circulation path C2.

Description

Technical Field

[0001] The present invention relates to a hot water storage type hot water supply system capable of instant hot water operation. Here, the "instant hot water operation" in this specification means that when the hot water supply terminal is in an open state, hot water at a predetermined temperature or higher can immediately flow out from this hot water supply terminal, and in the hot water flow path connected to the hot water supply terminal, it is an operation for circulating and retaining heated hot water at a predetermined temperature or higher.

Background Art

[0002] As an example of a hot water storage type hot water supply system, there is a hot water storage type hot water supply system SYe shown in Fig. 4(a). This hot water storage type hot water supply system SYe includes a hot water storage tank 1 capable of storing hot water heated using a heat pump 2 as a heat source. Further, it includes a hot water outlet path 51 for supplying the hot water in the hot water storage tank 1 to a desired hot water supply terminal 90, a water inlet path 50 for supplying unheated hot water supplied to the water inlet 50a to an intermediate position of the hot water storage tank 1 and the hot water outlet path 51, a return path 54e, and a hot water circulation path Ce for instant hot water. One end of the return path 54e is connected to a position Pc near the hot water supply terminal 90 in the hot water outlet path 51, and the other end is connected to the hot water storage tank 1, and a pump P1 for hot water circulation is provided.

[0003] The hot water circulation path Ce for instant hot water is the hot water circulation path shown by the thick line in Fig. 4(b). That is, this hot water circulation path Ce is a flow path capable of performing an operation (instant hot water operation) of circulating in a certain path so that when the hot water supply terminal 90 is in a closed state, the hot water discharged from the hot water storage tank 1 to the hot water outlet path 51 is returned to the hot water storage tank 1 via the return path 54e by driving the pump P1. If the instant hot water operation is being performed, when the hot water supply terminal 90 is in an open state, it is possible to immediately let the hot water (warm water) in the hot water circulation path Ce flow out from the hot water supply terminal 90.

[0004] However, in the above-mentioned prior art, as described below, there was still room for improvement.

[0005] In other words, in the hot water circulation path Ce for instant hot water, the hot water that has passed through the return path 54e is configured to be returned to the hot water storage tank 1. On the other hand, when hot water flows through the hot water circulation path Ce, heat is dissipated into the pipes and the outside air, so the temperature of the hot water that passes through the return path 54e and is returned to the hot water storage tank 1 is not only lower than the temperature of the hot water dispensed from the hot water storage tank 1, but also fluctuates due to the influence of the outside temperature and is not constant. Therefore, if such hot water is returned to the hot water storage tank 1, the temperature distribution (temperature stratification) of the hot water in the hot water storage tank 1 will be different from the distribution that was originally intended. This may make it difficult to dispense hot water at a temperature above a predetermined temperature from the hot water storage tank 1, potentially leading to insufficient heat during hot water supply. Furthermore, when a heat pump 2 is used as the heat source, the lower the temperature of the hot water supplied to the heat pump 2, the better the hot water heating efficiency. However, in the conventional technology described above, the temperature of the hot water supplied from the hot water storage tank 1 to the heat pump 2 and heated may be higher than the intended temperature, potentially leading to a decrease in hot water heating efficiency. Therefore, it is required that such issues be appropriately resolved. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-265212 [Patent Document 2] Japanese Patent Publication No. 2014-142112 [Overview of the project] [Problems that the invention aims to solve]

[0007] This invention was conceived under the circumstances described above, and its objective is to provide a hot water storage system that can appropriately prevent the temperature distribution of the hot water in the storage tank from deviating significantly from the intended temperature distribution due to instant hot water operation. [Means for solving the problem]

[0008] To solve the above problems, the present invention employs the following technical measures.

[0009] The hot water storage system provided by the present invention comprises a hot water storage tank capable of storing hot water heated using a heat source, a first hot water outlet for supplying hot water from the hot water storage tank to a hot water supply terminal, a first return outlet and a first hot water circulation path for instant hot water, one end of which is connected to the first hot water outlet near the hot water supply terminal, and the first pump for hot water circulation, which is capable of causing the hot water from the first hot water outlet to flow into the first return outlet by the drive of the first pump, wherein the first hot water circulation path is capable of instant hot water operation in which the hot water from the first return outlet returns to the first hot water outlet without passing through the hot water storage tank The invention further comprises a heat exchanger to which hot water is supplied from a tank to a primary side region via a second outlet channel, and which is capable of heating the hot water in the first hot water circulation path that flows to a secondary side region using the supplied hot water; a second return channel for returning the hot water that has passed through the primary side region of the heat exchanger back to the hot water storage tank, and a second pump for hot water circulation, wherein the hot water in the hot water storage tank is supplied to the primary side region of the heat exchanger via the second outlet channel and then returned to the hot water storage tank via the second return channel by the drive of the second pump, and a hot water flow rate changing means that can change the hot water flow rate Qc of the second hot water circulation path.

[0010] This configuration yields the following effects: In other words, the first hot water circulation path for instant hot water is configured such that the hot water that flows from the first outlet path to the first return path returns to the first outlet path without passing through the hot water storage tank. This hot water can be heated using the hot water and heat exchanger in the second hot water circulation path for instant hot water heating. Therefore, during instant hot water operation, the hot water in the first hot water circulation path is maintained at a predetermined temperature or higher, and when the hot water supply terminal is opened, hot water at that temperature can be immediately discharged from the hot water supply terminal. According to the present invention, although the hot water in the first hot water circulation path for instant hot water circulates without passing through the hot water storage tank, this does not impair the instant hot water function. On the other hand, the hot water in the second hot water circulation path for instant heating, after passing through the primary side of the heat exchanger, is returned to the hot water storage tank via the second return path. If the temperature of this hot water fluctuates significantly, the temperature distribution of the hot water in the storage tank may differ from the intended distribution. However, according to the present invention, the flow rate of the hot water in the second hot water circulation path can be changed using the hot water flow rate changing means. This makes it possible to adjust and stabilize the temperature of the hot water that is returned to the hot water storage tank after passing through the primary side of the heat exchanger. (When the flow rate of hot water in the primary side of the heat exchanger is low, the influence of the hot water on the low-temperature side (heated side), which is the secondary side, becomes greater, and the temperature drop of the hot water after passing through the heat exchanger becomes larger. Conversely, when the flow rate of hot water in the primary side is high, the temperature drop of the hot water after passing through the heat exchanger becomes smaller.) Therefore, it is possible to appropriately prevent the temperature distribution of the hot water in the hot water storage tank from deviating significantly from the intended state due to the return of hot water to the storage tank. As a result, it is possible to appropriately resolve problems such as difficulty in dispensing hot water above a predetermined temperature from the storage tank due to an inappropriate temperature distribution of hot water in the storage tank, or problems where the temperature of the hot water supplied from the storage tank to the heat source for heating becomes higher than the intended temperature, resulting in low hot water heating efficiency.

[0011] In the present invention, preferably, the first hot water circulation path includes a bypass path connected in parallel to the heat exchanger so as to avoid supplying hot water to the heat exchanger, and a flow rate ratio changing means that can change the ratio between the hot water flow rate Qa in the secondary side region of the heat exchanger and the hot water flow rate Qb in the bypass path during the instant hot water operation.

[0012] With this configuration, during instant hot water operation when hot water is circulated in the first hot water circulation path, the total hot water flow rate in the first hot water circulation path remains constant, while the hot water flow rate Qa in the secondary side region of the heat exchanger can be changed to appropriately and rationally adjust the hot water temperature in the first hot water circulation path.

[0013] In the present invention, preferably, during the instant hot water operation, the ratio of the hot water flow rate Qa in the secondary side region of the heat exchanger to the hot water flow rate Qb in the bypass channel is set to 1:0 when the hot water in the first hot water circulation path is below a predetermined temperature range, and to 0:1 when it exceeds the predetermined temperature range.

[0014] With this configuration, control is performed to keep the water temperature in the first hot water circulation path within a predetermined temperature range during instant hot water operation, thereby optimizing the instant hot water temperature. Furthermore, when the water temperature in the first hot water circulation path is below the predetermined temperature range and it is necessary to heat the water in the first hot water circulation path, the amount of water heating using the heat exchanger can be increased to the maximum extent, thereby shortening the time required to raise the water temperature to the predetermined temperature range. When the water temperature in the first hot water circulation path exceeds the predetermined temperature range and it is not necessary to heat the water in the first hot water circulation path, water is not supplied to the secondary side of the heat exchanger, thus avoiding the problem of the water temperature in the primary side of the heat exchanger (the water temperature in the second hot water circulation path) dropping unnecessarily.

[0015] In the present invention, preferably, a temperature detection means capable of detecting the hot water temperature T2 of the second return path and the hot water storage temperature T3 around the connection point of the second return path in the hot water storage tank, and a control means that, when the instant hot water operation is in progress and hot water circulation is being performed in the second hot water circulation path, reduces the hot water flow rate Qc of the second hot water circulation path when the hot water temperature T2 is higher than the hot water storage temperature T3, and increases the hot water flow rate Qc of the second hot water circulation path when the hot water temperature T2 is lower than the hot water storage temperature T3, thereby performing control to bring the hot water temperature T2 closer to the hot water temperature T3.

[0016] With this configuration, during instant hot water operation, when the heat exchanger is used to heat the hot water in the first hot water circulation path, the hot water temperature T2 in the second return path is set to a temperature close to the hot water temperature T3 around the connection point of the second return path in the hot water storage tank. Therefore, large fluctuations in the hot water temperature distribution in the hot water storage tank caused by the return of the hot water in the second return path to the hot water storage tank are more effectively prevented.

[0017] In the present invention, preferably, a plurality of hot water temperature detection sensors are provided at intervals in the vertical direction of the hot water storage tank, the upper and lower parts of the hot water storage tank are connected by piping to the heat source, and the hot water storage operation to the hot water storage tank is configured such that hot water heated by being sent from the lower part of the hot water storage tank to the heat source is returned to the upper part of the hot water storage tank, the first and second outlet passages are both connected to the upper part of the hot water storage tank, and the second return passage is provided at a position in the hot water storage tank lower than the connection part to the first and second outlet passages, so as to return the hot water to an area whose temperature is detected by any of the plurality of hot water temperature detection sensors.

[0018] With this configuration, the temperature distribution of the hot water in the hot water storage tank is basically as follows: The upper side is the high-temperature side and the lower side is the low-temperature side, and it is possible to let high-temperature hot water flow out from the upper part of the hot water storage tank into the first and second hot water outlet paths. Also, when the hot water that has flowed out into the second hot water outlet path (the second hot water circulation path) passes through the heat exchanger and its temperature drops, and then returns to the hot water storage tank from the second return path, it is returned to a position lower than the connection part between the first and second hot water outlet paths and the hot water storage tank. Therefore, it is further appropriately prevented that the temperature distribution of the hot water in the hot water storage tank is greatly disturbed. Furthermore, although the plurality of hot water storage temperature detection sensors are useful for grasping the temperature distribution and heat quantity of the hot water in the hot water storage tank, the second return path is provided so as to return the hot water to the region where the temperature is detected by any one of the plurality of hot water storage temperature detection sensors. For this reason, if the hot water temperature of the second return path is controlled to be close to the hot water storage temperature of the said region, it is possible to prevent the temperature distribution of the hot water in the hot water storage tank from being greatly disturbed, and the facilitation of the said control can be achieved.

[0019] Other features and advantages of the present invention will become clearer from the following description of the embodiments of the invention with reference to the accompanying drawings.

Brief Explanation of Drawings

[0020] [Figure 1] (a) is a schematic explanatory diagram showing an example of a hot water storage type hot water supply system according to the present invention, and (b) is a schematic explanatory diagram showing an operation example of the hot water storage type hot water supply system shown in (a). [Figure 2] It is a schematic explanatory diagram of the main part showing another operation example of the hot water storage type hot water supply system shown in Fig. 1. [Figure 3] It is a flowchart showing an example of an operation control procedure executed in the hot water storage type hot water supply system shown in Fig. 1. [Figure 4] (a) is a schematic explanatory diagram showing an example of the prior art, and (b) is a schematic explanatory diagram showing an operation example of (a).

Embodiments for Carrying Out the Invention

[0021] (a) is a schematic explanatory diagram showing an example of the prior art, and (b) is a schematic explanatory diagram showing an operation example of (a). Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings. For ease of understanding, elements in Figure 1 that are identical or similar to those in the prior art shown in Figure 4 are appropriately denoted by the same reference numerals.

[0022] The hot water storage system SY shown in Figure 1 comprises a hot water storage tank 1, a heat pump 2 for heating the hot water in the storage tank 1, a first hot water circulation path C1 for instant hot water, a second hot water circulation path C2 for instant hot water heating, a heat exchanger 3, a control unit 4, and various valves, sensors, and pumps, which will be described later. The main parts of the hot water storage system SY, excluding the heat pump 2, are housed and protected within an outer casing 19.

[0023] The heat pump 2 is an example of a "heat source" as defined in this invention, and is capable of heating the hot water sent from the hot water storage tank 1. More specifically, the heat pump 2 is a conventionally known vapor compression type (gas liquefaction type) heat pump that uses a refrigerant such as CO2. The lower and upper parts of the hot water storage tank 1 are connected to the heat pump 2 via piping sections 20 and 21 equipped with a pump P3. When the pump P3 is driven, hot water is sent from the lower part of the hot water storage tank 1 to the heat pump 2 via piping section 20 and heated, and this heated hot water flows into the upper part of the hot water storage tank 1 via piping section 21. Therefore, the temperature distribution of the hot water in the hot water storage tank 1 is basically such that the upper side is the high-temperature side and the lower side is the low-temperature side.

[0024] Multiple hot water temperature sensors Sa are installed on the side wall of the hot water storage tank 1, spaced apart in the vertical direction, to detect the temperature of the hot water inside the tank. By utilizing these multiple hot water temperature sensors Sa, the control unit 4 can grasp the temperature distribution of the hot water inside the tank 1 and make decisions regarding the amount of heat stored.

[0025] The lower and upper parts of the hot water storage tank 1 are also connected to an internal water inlet channel 50 and a first hot water outlet channel 51. The internal water inlet channel 50 is a hot and cold water channel that allows water supplied from a water supply pipe (not shown), such as a water pipe, to flow into the lower part of the hot water storage tank 1, and is equipped with a pressure reducing valve Vh and an on / off valve Ve. The first hot water outlet channel 51 is a hot water channel for guiding the hot water discharged from the top of the hot water storage tank 1 to a desired hot water supply terminal 90, and has an internal hot water outlet channel 51a leading from the hot water storage tank 1 to the outlet 51c, and an external hot water outlet channel 51b leading from the outlet 51c to the hot water supply terminal 90. An auxiliary channel 52, branched from the internal inlet channel 50, is connected to a point Pa midway through the first hot water outlet channel 51. This allows for the mixing of unheated hot water from the inlet 50a with the hot water flowing from the storage tank 1 into the first hot water outlet channel 51. This mixing ratio can be controlled using two flow control valves Vd and Vf, which makes it possible to set the hot water temperature supplied to the hot water terminal 90 to a desired target temperature or a temperature close to it. Furthermore, as a means of preventing high-temperature hot water from being discharged to the hot water terminal 90, an additional auxiliary flow path 53 is provided, which branches off from the internal inlet passage 50, has one end connected to a position Pb close to the outlet 51c of the first outlet passage 51, and is equipped with an on / off valve Vg.

[0026] The first and second hot water circulation paths C1 and C2 for instant hot water and instant hot water heating are the hot water flow paths shown by thick lines (thick arrows in the case of the hot water storage tank 1) in Figure 1(b), and are capable of supplying hot water to the heat exchanger 3. More specifically, the heat exchanger 3 is a liquid-liquid heat exchanger, and hot water from the first and second hot water circulation paths C1 and C2 pass through its secondary side region 3b (heated side) and primary side region 3a (heating side), and the hot water from the second hot water circulation path C2 can be used to heat the hot water from the first hot water circulation path C1.

[0027] The first hot water circulation path C1 for instant hot water includes a first outlet path 51, a first return path 54, and a first pump P1 for hot water circulation. The first return path 54 is a hot water flow path in which one end is connected to a position Pc closer to the hot water supply terminal 90 of the first outlet path 51, and the other end is connected to a position Pd further upstream of the first outlet path 51. It has an external flow path 54b and an internal flow path 54a connected via a hot water return port 54c. The first pump P1 for hot water circulation is provided in this first return path 54. The secondary side region 3b of the heat exchanger 3 constitutes a part of the first return path 54.

[0028] In this first hot water circulation path C1, when the first pump P1 is driven with the hot water supply terminal 90 closed, it is possible to circulate the hot water flowing from the hot water storage tank 1 to the first hot water outlet path 51, allowing it to flow into the first return path 54, pass through the secondary side area 3b of the heat exchanger 3, and then return it to the upstream side of the first hot water outlet path 51 (instant hot water operation). During this instant hot water operation, when the hot water supply terminal 90 is opened, the hot water in the first hot water circulation path C1 (hot water controlled to a predetermined temperature range as described later) is immediately dispensed from the hot water supply terminal 90.

[0029] The first hot and cold water circulation path C1 (first return path 54) is further provided with a bypass path 55 connected in parallel to the heat exchanger 3 and capable of avoiding the supply of hot and cold water to the heat exchanger 3, as well as two flow control valves Va and Vb that can change the ratio of the hot and cold water flow rate Qa in the secondary side region 3b of the heat exchanger 3 and the hot and cold water flow rate Qb in the bypass path 55 to a desired ratio. The flow control valves Va and Vb correspond to specific examples of the "flow rate ratio changing means" as defined in the present invention. In the first hot and cold water circulation path C1, when the flow control valve Va is fully open and the flow control valve Vb is fully closed (the ratio of hot and cold water flow rates Qa and Qb is 1:0), hot and cold water flows through the path shown by the thick line in Figure 1(b). Conversely, when the flow control valve Va is fully closed and the flow control valve Vb is fully open (the ratio of hot and cold water flow rates Qa and Qb is 0:1), hot and cold water flows through the first hot and cold water circulation path C1 through the path shown by the thick line in Figure 2.

[0030] The second hot water circulation path C2 for instant hot water heating includes a second hot water outlet path 62, a second return path 63, and a hot water circulation path. It is equipped with a second pump P2 for circulation and a flow control valve Vc. The primary side region 3a of the heat exchanger 3 constitutes part of the second hot water circulation path C2. The second outlet passage 62 is a hot water passage for supplying hot water discharged from the upper part of the hot water storage tank 1 to the primary side region 3a of the heat exchanger 3. The second return passage 63 is a hot water passage for returning the hot water that has passed through the primary side region 3a of the heat exchanger 3 back to the hot water storage tank 1. The connection point Na between one end (terminus) of this second return passage 63 and the hot water storage tank 1 is slightly lower in height than the connection points Nb between the first and second outlet passages 51 and 62 and the hot water storage tank 1, respectively, and is provided to return the hot water to the region where temperature detection is performed by the upper hot water temperature detection sensor Sa' among the multiple hot water temperature detection sensors Sa.

[0031] In this second hot water circulation path C2, when the second pump P2 is driven, the hot water from the hot water storage tank 1 is supplied to the primary side region 3a of the heat exchanger 3 via the second outlet path 62 and then returned to the hot water storage tank 1 via the second return path 63. The hot water flow rate Qc (corresponding to the hot water flow rate in the primary side region 3a of the heat exchanger 3) can be changed using a flow rate adjustment valve Vc. The flow rate adjustment valve Vc corresponds to a specific example of the "hot water flow rate changing means" as described in this invention.

[0032] The control unit 4 is configured, for example, using a microcomputer, and corresponds to an example of a "control means" as defined in this invention. It performs operational control and data processing for each part of the hot water storage system SY. However, the details will be described later. Furthermore, the control unit 4 is connected to a remote control 4A, which is installed in the bathroom or kitchen. The remote control 4A includes an operation unit 40 equipped with operation switches and a display unit 41 capable of displaying data, allowing the user to set the target hot water temperature and other settings using the operation unit 40. In Figure 1, the symbols Sb to Se indicate temperature sensors for detecting water temperature, and the symbols Sg and Sh indicate flow sensors for detecting water flow rate. Temperature sensors Sb and Sa' correspond to specific examples of the "temperature detection means" as defined in this invention.

[0033] Next, an example of the operation control procedure by the control unit 4 of the aforementioned hot water storage system SY will be explained with reference to the flowchart in Figure 3, and its operation will also be described. In addition to the instant hot water supply system SY, a normal hot water supply operation (where hot water is supplied at the target temperature when the hot water supply terminal 90 is open, without the instant hot water supply operation being performed) is also possible. However, the following describes the case in which the instant hot water supply operation is performed.

[0034] First, when the remote control 4A is used and a predetermined operation is performed to start instant hot water operation, assuming that the hot water terminal 90 is closed and the flow rate detected by the flow sensor Sg is zero, the first pump P1 is started to drive and instant hot water operation begins (S1:YES, S2:YES, S3). In this instant hot water operation, as described above, hot water circulates in the first hot water circulation path C1. In addition to the predetermined operation being performed, conditions for starting instant hot water operation can also be applied, such as the hot water temperature detected using the temperature sensor Sc falling below a predetermined temperature (the temperature at which instant hot water operation is required). When instant hot water operation is started, the control unit 4 determines whether the water temperature Ta of the first hot water circulation path C1 is within a predetermined temperature range based on temperature detection by temperature sensors Sc and Sd (S4). Here, the predetermined temperature range is, for example, approximately the same as the target hot water supply temperature.

[0035] It is unlikely that the water temperature Ta of the first water circulation path C1 will fall within the predetermined temperature range from the start of the instant hot water operation. However, contrary to this, if the water temperature Ta is within the predetermined temperature range and that state is maintained, and the hot water terminal 90 is opened, or if an operation to terminate the instant hot water operation is performed using the remote control 4A, the first pump P1 will stop at that point, and the instant hot water operation will end (S4:YES, S5:YES, S6).

[0036] Unlike the above, when instant hot water operation is started, if the water temperature Ta of the first hot water circulation path C1 is not within the predetermined temperature range and is below the predetermined temperature range, the flow control valve Va on the heat exchanger 3 side is fully opened, the flow control valve Vb on the bypass flow path 55 side is fully closed, and the second pump P2 is started to drive (S4: NO, S7: YES, S8, S9). As a result, instant hot water heating operation is started in which hot water flows through the second hot water circulation path C2, and it is possible to heat the hot water in the first hot water circulation path C1 using the hot water in the second hot water circulation path C2 and the heat exchanger 3. During this heating, the ratio of the hot water flow rate Qa in the secondary side region 3b of the heat exchanger 3 to the hot water flow rate Qb in the bypass flow path 55 is set to 1:0, so the heating efficiency for the hot water in the first hot water circulation path C1 is increased, and it is possible to raise the water temperature to the predetermined temperature range in a short time.

[0037] On the other hand, when the instant hot water heating operation is started, the hot water that has passed through the primary side region 3a of the heat exchanger 3 and experienced a temperature drop is returned to the hot water storage tank 1 from the connection point Na via the second return passage 63. In response to this, according to this embodiment, control is performed to bring the hot water temperature T2 in the second return passage 63, detected by the temperature sensor Sb, closer to the hot water temperature T3 near the connection point Na inside the hot water storage tank 1, detected by the temperature sensor Sa' (S10). This control uses a flow control valve Vc to change the hot water flow rate Qc of the second hot water circulation path C2 (the hot water flow rate in the primary side region 3a of the heat exchanger 3). When the hot water temperature T2 of the second return path 63 is higher than the hot water storage temperature T3, the hot water flow rate Qc of the second hot water circulation path C2 is reduced. This increases the reduction in hot water temperature in the primary side region 3a of the heat exchanger 3, allowing the hot water temperature T2 to be lowered and brought closer to the hot water storage temperature T3. Conversely, when the hot water temperature T2 of the second return path 63 is lower than the hot water storage temperature T3, the hot water flow rate Qc of the second hot water circulation path C2 is increased. This prevents the hot water temperature from decreasing significantly in the primary side region 3a of the heat exchanger 3, bringing the hot water temperature T2 closer to the hot water storage temperature T3.

[0038] When the aforementioned control is executed, the problem of the temperature distribution (temperature stratification) of the hot water in the hot water storage tank 1 becoming inappropriate and differing from the intended temperature distribution due to the hot water being returned to the hot water storage tank 1 via the second return passage 63 is resolved. Unlike this embodiment, if the temperature distribution of the hot water in the hot water storage tank 1 becomes inappropriate, there is a risk of problems such as difficulty in dispensing hot water above a predetermined temperature from the hot water storage tank 1, or the hot water temperature supplied from the hot water storage tank 1 to the heat pump 2 becoming too high, resulting in a decrease in the heating efficiency of the hot water by the heat pump 2. In contrast, this embodiment can appropriately resolve such risks. The operation control described in step S10 continues to be performed while the second pump P2 is running and instant hot water heating is being carried out.

[0039] Subsequently, if the water temperature Ta of the first water circulation path C1 falls within the predetermined temperature range, control is performed to maintain the water temperature Ta within the predetermined temperature range (S11:YES, S12). In this control, instead of maintaining the two flow control valves Va and Vb in the fully open or fully closed state described above, the water flow rates Qa and Qb passing through the secondary side area 3b of the heat exchanger 3 and the bypass flow path 55, respectively, are finely controlled. More specifically, when the water temperature Ta is high, the flow control valves Va and Vb are controlled to reduce the water flow rate Qa in the secondary side area 3b of the heat exchanger 3 and increase the water flow rate Qb in the bypass flow path 55 by the same amount. When the water temperature Ta is low, the opposite is done. With this control, maintaining the water temperature Ta of the first water circulation path C1 within the predetermined temperature range can be easily and appropriately achieved using the two flow control valves Va and Vb. If the hot water terminal 90 is opened or the remote control 4A is used to terminate the instant hot water operation while the aforementioned control is being executed, the first and second pumps P1 and P2 will stop at that point and the instant hot water operation will end (S13: YES, S14).

[0040] On the other hand, unlike above, if the water temperature Ta of the first hot water circulation path C1 exceeds a predetermined temperature range at the start of instant hot water operation, the flow control valve Va on the heat exchanger 3 side is fully closed, and the flow control valve Vb on the bypass flow path 55 side is fully open (S4:NO, S7:NO, S15). In other words, the ratio of the water flow rate Qa in the secondary side region 3b of the heat exchanger 3 to the water flow rate Qb in the bypass flow path 55 is set to 0:1. At the start of instant hot water operation, the water temperature of the water that flows out from the hot water storage tank 1 to the first hot water outlet path 51 may be higher than the predetermined temperature range, and in this case, it is not necessary to heat the water in the first hot water circulation path C1. The above operation is rational because it avoids supplying water to the heat exchanger 3 when such heating is not necessary. Unnecessary heat exchange between the water in the primary side region 3a and the secondary side region 3b of the heat exchanger 3 is also appropriately avoided. If, as a result of the operation in step S15 described above, the water temperature Ta of the first water circulation path C1 falls within a predetermined temperature range (S11: YES), then the process proceeds to step S12 described above.

[0041] The present invention is not limited to the embodiments described above. The specific configuration of each part of the hot water storage system according to the present invention can be modified in various ways within the scope intended by the present invention.

[0042] In the above-described embodiment, a flow control valve Vc is used as a means for changing the hot and cold water flow rate, but the present invention is not limited thereto. When the second pump P2 has a variable hot and cold water discharge flow rate, it is possible to change the hot and cold water flow rate Qc of the second hot and cold water circulation path C2 by controlling the driving speed of the second pump P2, and this second pump P2 corresponds to the means for changing the hot and cold water flow rate. Furthermore, the means for changing the flow rate ratio in this invention is not limited to two flow control valves Va and Vb, but may consist of, for example, only one of them, or it may even be a directional switching valve provided at the branching point between the path directing hot and cold water towards the heat exchanger 3 and the path directing hot and cold water towards the bypass flow path 55. The specific size and shape of the hot water storage tank, as well as the specific types of the first and second pumps, are not limited. Instead of a heat pump, other devices and equipment can be used as the heat source, such as a gas engine system or fuel cell unit equipped with a heat exchanger capable of heating hot water. [Explanation of symbols]

[0043] SY Storage-type Hot Water Supply System C1 First hot water circulation channel for instant hot water C2 Second hot water circulation path for instant hot water heating P1, P2: First and second pumps Sb,Sa' Temperature sensor (temperature detection means) Va, Vb flow control valve (means for changing the flow ratio) Vc flow control valve (means for changing the flow rate of hot and cold water) Na Second return path and connection to the hot water storage tank 1. Hot water storage tank 2. Heat pump (heat source) 3 Heat exchanger 3a Primary side region (of the heat exchanger) 3b Secondary side region (of the heat exchanger) 4. Control Unit (Control Means) 51 The first hot spring source 54 The first return route 55 Bypass channel 62 The second hot spring source 63 The second return route

Claims

1. A hot water storage tank capable of storing hot water heated using a heat source, This hot water storage tank has a first hot water outlet for supplying hot water to the hot water supply terminal, This first hot water outlet includes a first return outlet and a first pump for hot water circulation, one end of which is connected to the hot water terminal of the first outlet outlet, and the first pump is driven to cause the hot water from the first outlet outlet to flow into the first return outlet, and A storage-type hot water supply system equipped with, The first hot water circulation path is configured to enable instant hot water operation in which the hot water in the first return path circulates back to the first outlet path without passing through the hot water storage tank. A heat exchanger is provided which hot water is supplied from the hot water storage tank to the primary side region via a second hot water outlet, and which can use this supplied hot water to heat the hot water in the first hot water circulation path that flows to the secondary side region. This includes a second return path for returning the hot water that has passed through the primary side region of the heat exchanger back to the hot water storage tank, and a second pump for hot water circulation, wherein the second pump drives the hot water storage tank to be supplied to the primary side region of the heat exchanger via the second outlet path and then returned to the hot water storage tank via the second return path, and a second hot water circulation path for instant hot water heating is provided, This second hot water circulation path includes a means for changing the hot water flow rate Qc, A storage-type hot water supply system characterized by having an additional feature.

2. A hot water supply system with storage capacity according to claim 1, The first hot and cold water circulation path is, A bypass channel connected in parallel to the heat exchanger so as to avoid supplying hot water to the heat exchanger, During the instant hot water operation described above, a flow rate ratio changing means is provided that can change the ratio between the hot water flow rate Qa in the secondary side region of the heat exchanger and the hot water flow rate Qb in the bypass channel, A storage-type hot water supply system equipped with this feature.

3. A hot water supply system with storage capacity according to claim 2, A hot water storage system configured such that, during the instant hot water operation described above, the ratio of the hot water flow rate Qa in the secondary side region of the heat exchanger to the hot water flow rate Qb in the bypass channel is set to 1:0 when the hot water in the first hot water circulation path is below a predetermined temperature range, and to 0:1 when it exceeds the predetermined temperature range.

4. A hot water supply system with storage according to any one of claims 1 to 3, A temperature detection means capable of detecting the hot water temperature T2 of the second return path and the hot water temperature T3 of the hot water storage tank around the connection point of the second return path, When the instant hot water operation is in progress and hot water is being circulated in the second hot water circulation path, the control means performs control to bring the hot water temperature T2 closer to the hot water temperature T3 by decreasing the hot water flow rate Qc in the second hot water circulation path when the hot water temperature T2 is higher than the hot water storage temperature T3, and increasing the hot water flow rate Qc in the second hot water circulation path when the hot water temperature T2 is lower than the hot water storage temperature T3. A storage-type hot water supply system that also features [the following].

5. A hot water supply system with storage capacity according to claim 1, The system further includes a plurality of hot water temperature detection sensors arranged at intervals in the vertical direction of the hot water storage tank. The upper and lower parts of the hot water storage tank are connected by piping to the heat source, and the hot water storage operation in the hot water storage tank is performed by sending hot water heated from the lower part of the hot water storage tank to the heat source and storing it in the tank. It is configured to be performed in a manner that returns the water to the upper part of the hot water tank. Both the first and second hot water outlets are connected to the top of the hot water storage tank. A hot water supply system with a hot water storage system, wherein the second return path is located in the hot water storage tank at a lower position than the connection point with the first and second outlet paths, and returns the hot water to an area whose temperature is detected by one of the plurality of hot water storage temperature detection sensors.

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