EP3306221A2

EP3306221A2 - Water heating system

Info

Publication number: EP3306221A2
Application number: EP17194192.5A
Authority: EP
Inventors: Masashi Maeno; Masatomo KOSAKA
Original assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Current assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Priority date: 2016-10-05
Filing date: 2017-09-29
Publication date: 2018-04-11
Also published as: EP3306221A3; JP2018059670A

Abstract

The present invention aims to provide a water heating system capable of reducing the frequency of maintenance of a heat exchanger required because of scale.

The present invention provides a heat exchanger (23) including a plurality of heat exchange units (31, 32) which are separated from each other in a predetermined direction and are connected to each other in series. The total cross-sectional area of a water flow channel of the first heat exchange unit (31) cut along a plane orthogonal to a direction in which water flows is smaller than a total cross-sectional area of a water flow channel of the second heat exchange unit (32) cut along a plane orthogonal to the direction in which water flows.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a water heating system.

Description of Related Art

In the related art, as a water heating system in which water is configured to turn into hot water due to heat exchange between a refrigerant and the water, for example, a heat pump-type water heating system is known.
The heat pump-type water heating system is configured to include a refrigerant unit that includes a refrigerant circulation line in which a refrigerant circulates, and a compressor, a vaporizer, and a heat exchanger which are provided in the refrigerant circulation line; and a hot water storage unit that includes a water flow channel which is connected to the heat exchanger and in which water or hot water flows, a pump which is provided in the water flow channel, a hot water storage tank which is connected to the water flow channel, and a water supply line which is configured to supply water from outside to a lower portion of the hot water storage tank.
In the water heating system having the above-described configuration, when water in the water flow channel is guided into the heat exchanger configuring the refrigerant unit, the temperature of the water rises and the water turns into hot water due to heat exchange between the refrigerant flowing inside the heat exchanger and the water. Then, the hot water is guided into the hot water storage tank.
As water flowing in the water flow channel, for example, tap water, underground water, or the like is employed. However, water, such as tap water, underground water, and the like, contains hardness components such as calcium and magnesium, and there are cases of a remarkably significant amount of the hardness components being contained, depending on the geographical zone.
When water containing a significant amount of such hardness components is supplied from outside of the water heating system to the inside of the hot water storage tank via the water supply line, and when the refrigerant and the water supplied through the water supply line are subjected to heat exchange inside the heat exchanger for a long period of time, there is a possibility that the hardness components will precipitate as scale on an exit side (a high-temperature part where the temperature of hot water is high) of the water flow channel inside the heat exchanger.
When such scale is deposited on a heat transfer surface or an inner circumferential surface of the water flow channel, the deposited scale hinders the flow of water, so that the pressure loss increases and the load on the pump increases. Accordingly, there is concern that the performance of the heat exchanger will prominently deteriorate.
Moreover, when the water flow channel is completely blocked by scale, the water heating system is no longer able to perform a water heating operation.
As a technology which can resolve such a problem, Patent Document 1 discloses a heat-pump water heater in which a heat exchanger can be divided into a high-temperature part (a part where the temperature of hot water is high) and a low-temperature part (a part where the temperature of water is not so high), and the high-temperature part is configured to be attachable and detachable.
In the heat-pump water heater having such a configuration, when scale grows in the high-temperature part, the high-temperature part in which scale has grown is replaced with a different high-temperature part to which no scale is adhering, or a water flow channel in only the high-temperature part is cleaned. Consequently, increase in load on a pump can be inhibited and blocking of the water flow channel because of scale can be inhibited.
When no water is supplied from outside to the inside of the hot water storage tank and water is caused to circulate in a closed loop, since water containing the aforementioned high-hardness components is not newly supplied from outside, scale is unlikely to be generated in the water flow channel provided in the high-temperature part of the heat exchanger.

[Patent Documents]

[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2004-144445

SUMMARY OF THE INVENTION

The technology disclosed in the aforementioned Patent Document 1 is a technology for improving the efficiency of maintenance of the heat exchanger after scale adheres to or grows in the water flow channel on a high-temperature side in the heat exchanger.
Therefore, in the technology disclosed in Patent Document 1, preventing scale from adhering to the water flow channel in the high-temperature part of the heat exchanger is not considered.
Therefore, when employing the technology disclosed in Patent Document 1, there is a need to regularly perform processing of replacing the high-temperature part or cleaning the water flow channel to which scale adheres in the high-temperature part, at the stage in which a certain amount of scale has adhered thereto, thereby leading to a problem in that the frequency of maintenance of the heat exchanger increases.
The present invention aims to provide a water heating system capable of reducing the frequency of maintenance of a heat exchanger required because of scale.
In order to solve the problem, according to an aspect of the present invention, there is provided a water heating system including a refrigerant unit that includes a refrigerant circulation line in which a refrigerant circulates, a vaporizer which is provided in the refrigerant circulation line, is configured to vaporize the liquid refrigerant decompressed by an expansion valve, and is configured to generate refrigerant gas, a compressor which is provided in the refrigerant circulation line, and is configured to compress the refrigerant gas guided out from the vaporizer, and a heat exchanger which is provided in the refrigerant circulation line, is configured to perform heat exchange between the refrigerant gas guided out from the compressor and water, and is configured to turn the water into hot water; and a hot water storage unit that includes a hot water storage tank which stores the hot water, a water guide-in line which is configured to guide the water stored in a lower portion inside the hot water storage tank into the heat exchanger through one end of the heat exchanger, a hot water guide-in line which is connected to the other end of the heat exchanger and is configured to guide the hot water to an upper portion of the hot water storage tank, and a water supply line which is configured to supply water from outside to the lower portion inside the hot water storage tank. The heat exchanger has a plurality of heat exchange units which are separated from each other in a predetermined direction and are connected to each other in series. The plurality of heat exchange units each include at least one water flow channel in which the water flows. The plurality of heat exchange units include at least a first heat exchange unit configuring the other end of the heat exchanger, and a second heat exchange unit being disposed in the vicinity of the first heat exchange unit in a direction in which the water flows. A total cross-sectional area of the water flow channel of the first heat exchange unit cut along a plane orthogonal to the direction in which the water flows is smaller than a total cross-sectional area of the water flow channel of the second heat exchange unit cut along a plane orthogonal to the direction in which the water flows.
According to the present invention, when the total cross-sectional area of the water flow channel of the first heat exchange unit cut along a plane orthogonal to the direction in which the water flows is smaller than the total cross-sectional area of the water flow channel of the second heat exchange unit cut along a plane orthogonal to the direction in which the water flows, the flow rate of hot water (water) flowing in the water flow channel of the first heat exchange unit in which the temperature of hot water is high such that scale is likely to be generated becomes higher than the flow rate of water (low-temperature hot water) flowing in the water flow channel of the second heat exchange unit. Therefore, it is possible to inhibit scale from being deposited in the water flow channel of the first heat exchange unit.
Accordingly, the water flow channel of the first heat exchange unit can be retained in an environment in which scale is unlikely to grow. Thus, it is possible to reduce the frequency of maintenance of the heat exchanger required because of scale.
In addition, in the water heating system according to the aspect of the present invention, the diameter of the water flow channel of the first heat exchange unit may be smaller than the diameter of the water flow channel of the second heat exchange unit.
In such a configuration, the total cross-sectional area of the water flow channel of the first heat exchange unit cut along a plane orthogonal to the direction in which the water flows can be smaller than the total cross-sectional area of the water flow channel of the second heat exchange unit cut along a plane orthogonal to the direction in which the water flows.
Accordingly, the flow rate of hot water flowing in the water flow channel of the first heat exchange unit becomes higher than the flow rate of water flowing in the water flow channel of the second heat exchange unit. Thus, it is possible to inhibit scale from growing in the water flow channel of the first heat exchange unit.
In addition, in the water heating system according to the aspect of the present invention, the number of water flow channels of the first heat exchange unit may be less than the number of water flow channels of the second heat exchange unit.
In such a configuration, the total cross-sectional area of the water flow channel of the first heat exchange unit cut along a plane orthogonal to the direction in which the water flows can be smaller than the total cross-sectional area of the water flow channel of the second heat exchange unit cut along a plane orthogonal to the direction in which the water flows.
Accordingly, the flow rate of hot water flowing in the water flow channel of the first heat exchange unit becomes higher than the flow rate of water flowing in the water flow channel of the second heat exchange unit. Thus, it is possible to inhibit scale from growing in the water flow channel of the first heat exchange unit.
In addition, in the water heating system according to the aspect of the present invention, the heat exchanger may be divided into two units and may be configured to include the first heat exchange unit and the second heat exchange unit. The flow rate of the water flowing in the water flow channel of the first heat exchange unit may range from 1.5 times to 3.0 times a flow rate of the water flowing in the water flow channel of the second heat exchange unit.
In this manner, in a case where the heat exchanger is configured to include the first heat exchange unit disposed on a high-temperature side (side on which the temperature of hot water (water) is higher than that in the second heat exchange unit) and the second heat exchange unit, when the flow rate of water flowing in the water flow channel of the first heat exchange unit is lower than 1.5 times the flow rate of water flowing in the water flow channel of the second heat exchange unit, there is concern that an effect of washing away the scale will deteriorate.
Meanwhile, when the flow rate of water flowing in the water flow channel of the first heat exchange unit is higher than 3.0 times the flow rate of water flowing in the water flow channel of the second heat exchange unit, there is concern that the total value of the pressure loss caused due to the lengths of the first and second heat exchange units will increase.
Therefore, when the flow rate of water flowing in the water flow channel of the first heat exchange unit ranges from 1.5 times to 3.0 times the flow rate of water flowing in the water flow channel of the second heat exchange unit, an increase in the total value of the pressure loss of the first and second heat exchange units is inhibited, and it is possible to inhibit scale from growing in the water flow channel of the first heat exchange unit.
In addition, in the water heating system according to the aspect of the present invention, a length of the first heat exchange unit in the predetermined direction may be equal to or shorter than 0.5 times a length of the heat exchanger that is the sum total of a length of the second heat exchange unit in the predetermined direction and the length of the first heat exchange unit.
In this manner, in a case of being divided into two and having the first and second heat exchange units, when the length of the first heat exchange unit in the predetermined direction is longer than 0.5 times the length of the second heat exchange unit in the predetermined direction, the length of the water flow channel of the first heat exchange unit is lengthened, so that the pressure loss in the first heat exchange unit increases. Thus, there is concern that the total pressure loss of the first and second heat exchange units will increase.
Therefore, when the length of the first heat exchange unit is equal to or shorter than 0.5 times the length of the second heat exchange unit, the pressure loss in the first heat exchange unit is reduced, and it is possible to sufficiently inhibit scale from growing in the water flow channel of the first heat exchange unit.
According to another aspect of the present invention, there is provided a water heating system including a refrigerant unit that includes a refrigerant circulation line in which a refrigerant circulates, a vaporizer which is provided in the refrigerant circulation line, is configured to vaporize the liquid refrigerant decompressed by an expansion valve, and is configured to generate refrigerant gas, a compressor which is provided in the refrigerant circulation line, and is configured to compress the refrigerant gas guided out from the vaporizer, and a first heat exchanger which is provided in the refrigerant circulation line, is configured to perform heat exchange between the refrigerant gas guided out from the compressor and first water, and is configured to turn the first water into first hot water; a water circulation unit that includes a water circulation line which is configured to be a closed loop such that the first water circulates, and is configured to cause the first water to circulate in the first heat exchanger, and a second heat exchanger which is provided in the water circulation line, is configured to perform heat exchange between the first hot water and second water, and is configured to turn the second water into second hot water; and a hot water storage unit that includes a hot water storage tank which stores the second hot water, a water guide-in line which is configured to guide the second water stored in a lower portion inside the hot water storage tank into the second heat exchanger through one end of the second heat exchanger, a hot water guide-in line which is connected to the other end of the second heat exchanger and is configured to guide the second hot water to an upper portion inside the hot water storage tank, and a water supply line which is configured to supply the second water from outside to the lower portion inside the hot water storage tank. The second heat exchanger has a plurality of heat exchange units which are separated from each other in a predetermined direction and are connected to each other in series. The plurality of heat exchange units each include at least one water flow channel in which the second water flows. The plurality of heat exchange units include at least a first heat exchange unit configuring the other end of the second heat exchanger, and a second heat exchange unit being disposed in the vicinity of the first heat exchange unit in a direction in which the second water flows. The total cross-sectional area of the water flow channel of the first heat exchange unit cut along a plane orthogonal to the direction in which the second water flows is smaller than a total cross-sectional area of the water flow channel of the second heat exchange unit cut along a plane orthogonal to the direction in which the second water flows.
According to the present invention, when the total cross-sectional area of the water flow channel of the first heat exchange unit cut along a plane orthogonal to the direction in which the second water flows is smaller than the total cross-sectional area of the water flow channel of the second heat exchange unit cut along a plane orthogonal to the direction in which the second water flows, the flow rate of the second hot water (the second water) flowing in the water flow channel of the first heat exchange unit in which the temperature of the second hot water is high such that scale is likely to be generated can be higher than the flow rate of the second water flowing in the water flow channel of the second heat exchange unit.
Accordingly, scale can be inhibited from being deposited in the water flow channel of the first heat exchange unit. Thus, it is possible to reduce the frequency of maintenance of the heat exchanger required because of scale.
In addition, in the water heating system according to the aspect of the present invention, the diameter of the water flow channel of the first heat exchange unit may be smaller than the diameter of the water flow channel of the second heat exchange unit.
In such a configuration, the total cross-sectional area of the water flow channel of the first heat exchange unit cut along a plane orthogonal to the direction in which the second water flows becomes smaller than the total cross-sectional area of the water flow channel of the second heat exchange unit cut along a plane orthogonal to the direction in which the second water flows. Thus, the second water (the second hot water) flowing in the water flow channel of the second heat exchange unit is unlikely to flow in the water flow channel of the first heat exchange unit.
Accordingly, the flow rate of the second hot water flowing in the water flow channel of the first heat exchange unit can be higher than the flow rate of the second water flowing in the water flow channel of the second heat exchange unit. Thus, it is possible to inhibit scale from growing in the water flow channel of the first heat exchange unit, due to the flow rate of the second hot water flowing in the water flow channel of the first heat exchange unit.
In addition, in the water heating system according to the aspect of the present invention, the number of water flow channels of the first heat exchange unit may be less than the number of water flow channels of the second heat exchange unit.
In such a configuration, the total cross-sectional area of the water flow channel of the first heat exchange unit cut along a plane orthogonal to the direction in which the second water flows becomes smaller than the total cross-sectional area of the water flow channel of the second heat exchange unit cut along a plane orthogonal to the direction in which the second water flows. Thus, the second water (the second hot water) flowing in the water flow channel of the second heat exchange unit is unlikely to flow in the water flow channel of the first heat exchange unit.
Accordingly, the flow rate of the second hot water flowing in the water flow channel of the first heat exchange unit can be higher than the flow rate of the second water flowing in the water flow channel of the second heat exchange unit. Thus, it is possible to inhibit scale from growing in the water flow channel of the first heat exchange unit, due to the flow rate of the second hot water flowing in the water flow channel of the first heat exchange unit.
According to the present invention, it is possible to reduce the frequency of maintenance of a heat exchanger required because of scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram showing a schematic configuration of a water heating system according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view cut along line C₁-C₂ in a first heat exchange unit configuring a heat exchanger shown in FIG. 1.
FIG. 3 is a cross-sectional view cut along line D₁-D₂ in a second heat exchange unit configuring the heat exchanger shown in FIG. 1.
FIG. 4 is a system diagram showing a schematic configuration of a water heating system according to a modification example of the first embodiment of the present invention.
FIG. 5 is a cross-sectional view (Alternative 1) showing an alternative example of the first heat exchange unit.
FIG. 6 is a cross-sectional view (Alternative 1) showing an alternative example of the second heat exchange unit.
FIG. 7 is a cross-sectional view (Alternative 2) showing another alternative example of the first heat exchange unit.
FIG. 8 is a cross-sectional view (Alternative 2) showing another alternative example of the second heat exchange unit.
FIG. 9 is a system diagram showing a schematic configuration of a water heating system according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments in which the present invention is applied will be described in detail, with reference to the drawings. The drawings in the descriptions below are used for describing the configurations of the embodiments of the present invention. There are cases where the sizes, the thicknesses, the dimensions, and the like of the respective shown units and portions are different due to dimensional relationships in an actual water heating system.

(First Embodiment)

FIG. 1 is a system diagram showing a schematic configuration of a water heating system according to a first embodiment of the present invention. In FIG. 1, as an example of the water heating system of the first embodiment, a heat pump-type water heating system is shown.
In FIG. 1, "A" indicates a direction (hereinafter, will be referred to as "A-direction") in which a refrigerant moves inside a heat exchanger 23, "B" indicates a direction (hereinafter, will be referred to as "B-direction") in which water moves inside the heat exchanger 23, and "X" indicates a predetermined direction (hereinafter, will be referred to as "X-direction") in which first and second heat exchange units 31, 32 are disposed.
With reference to FIG. 1, a water heating system 10 of the first embodiment has a refrigerant unit 11 and a hot water storage unit 12.
The refrigerant unit 11 has a refrigerant circulation line 15, an expansion valve 17, a vaporizer 18, a compressor 21, the heat exchanger 23, and valves 25, 26.
One end of the refrigerant circulation line 15 is connected to one end 23A of the heat exchanger 23, and the other end thereof is connected to the other end 23B of the heat exchanger 23. The refrigerant circulation line 15 is a line for causing the refrigerant (for example, CO₂) to circulate.
The expansion valve 17 is provided in the refrigerant circulation line 15. The expansion valve 17 is disposed on the downstream side of the heat exchanger 23 when seen based on a flowing direction of the refrigerant. A low-temperature/high-pressure liquid refrigerant guided out from the heat exchanger 23 is supplied to the expansion valve 17. In the expansion valve 17, the low-temperature/high-pressure liquid refrigerant is decompressed, and a low-temperature/low-pressure liquid refrigerant is generated.
The vaporizer 18 is provided in the refrigerant circulation line 15. The vaporizer 18 is disposed on the downstream side of the expansion valve 17 when seen based on the flowing direction of the refrigerant. In the vaporizer 18, the low-temperature/low-pressure liquid refrigerant which has passed through the expansion valve 17 is vaporized, and a low-temperature/low-pressure gas refrigerant is generated.
The compressor 21 is provided in the refrigerant circulation line 15. The compressor 21 is disposed between the vaporizer 18 and the other end 23B of the heat exchanger 23.
The compressor 21 is configured to cause the low-temperature/low-pressure gas refrigerant guided out from the vaporizer 18 to be compressed and to rise in temperature, thereby generating a high-temperature/high-pressure gas refrigerant. The high-temperature/high-pressure gas refrigerant is guided into the heat exchanger 23 from the other end 23B side of the heat exchanger 23.
The heat exchanger 23 has a heat exchanger main body 30 including the first and second heat exchange units 31, 32; a first connection supply line 35; valves 36, 37, 42, 43; and a second connection supply line 41.
The heat exchanger main body 30 is divided into the first heat exchange unit 31 and the second heat exchange unit 32 in the X-direction (the predetermined direction). The first heat exchange unit 31 configures the other end 23B of the heat exchanger 23.
FIG. 2 is a cross-sectional view cut along line C₁-C₂ in the first heat exchange unit configuring the heat exchanger shown in FIG. 1. FIG. 2 shows a cross section of a tube-type heat exchanger as an example of the first heat exchange unit 31. In FIG. 2, the same reference signs are applied to configuration parts the same as in the structure shown in FIG. 1.
Subsequently, with reference to FIGS. 1 and 2, the first heat exchange unit 31 will be described. The first heat exchange unit 31 configures the other end 23B and has a tube 45 and plates 46.
One end of the tube 45 is connected to the second connection supply line 41, and the other end (an end disposed on the other end 23B side) thereof is connected to one end of a hot water guide-out line 68 (will be described below). The tube 45 defines a water flow channel 47.
In the water flow channel 47, low-temperature hot water (water) supplied from the second heat exchange unit 32 via the second connection supply line 41 flows in the B-direction. A diameter R₁ (in this case, the bore diameter, corresponding to the inner diameter of the tube 45) of the water flow channel 47 is uniform in size in the X-direction.
A plurality of plates 46 are disposed at predetermined intervals so as to be orthogonal to an extending direction of the tube 45. The plurality of plates 46 support the tube 45 and define spaces for accommodating the refrigerant (specifically, the high-temperature/high-pressure gas refrigerant guided out from the compressor 21).
In the first heat exchange unit 31 having the above-described configuration, low-temperature hot water (water) guided out from the second heat exchange unit 32 and a high-temperature/high-pressure gas refrigerant guided out from the compressor 21 are subjected to heat exchange, so that the temperature of the hot water becomes high (for example, a temperature equal to or higher than 60°C). In the first heat exchange unit 31, the high-temperature hot water is guided into an upper portion of a hot water storage tank 56 via a hot water guide-in line 66.
FIG. 3 is a cross-sectional view cut along line D₁-D₂ in the second heat exchange unit configuring the heat exchanger shown in FIG. 1. FIG. 3 shows a cross section of the tube-type heat exchanger as an example of the second heat exchange unit 32. In FIG. 3, the same reference signs are applied to configuration parts the same as in the structure shown in FIG. 1.
Subsequently, with reference to FIGS. 1 and 3, the second heat exchange unit 32 will be described. The second heat exchange unit 32 configures the one end 23A and has a tube 51 and plates 52.
One end (an end disposed on the one end 23A side) of the tube 51 is connected to a water guide-in line 61, and the other end thereof is connected to the second connection supply line 41. The tube 51 defines a water flow channel 53.
Water guided out from a lower portion (for example, the bottom) of the hot water storage tank 56 is supplied to the water flow channel 53 via the second connection supply line 41. A diameter R₂ (in this case, the bore diameter, corresponding to the inner diameter of the tube 51) of the water flow channel 53 is uniform in size in the X-direction.
Water is supplied to the lower portion of the hot water storage tank 56 from outside of the water heating system 10 via a water supply line 58 (will be described below). There are cases where the water contains many hardness components such as calcium and magnesium. When the temperature of the water rises to 60°C or higher, the hardness components cause scale.
A plurality of plates 52 are disposed at predetermined intervals so as to be orthogonal to an extending direction of the tube 51. The plurality of plates 52 support the tube 51 and define spaces for accommodating the refrigerant (specifically, the gas refrigerant supplied via the first heat exchange unit 31).
In the second heat exchange unit 32 having the above-described configuration, water (for example, approximately 20°C) guided out from the hot water storage tank 56 and the gas refrigerant which has passed through the first heat exchange unit 31 are subjected to heat exchange, so that water is heated and is configured to turn into low-temperature hot water (water) (for example, a temperature ranging from 20°C to less than 60°C).
Then, the low-temperature hot water (water) is guided into the tube 45 shown in FIG. 2, via the second connection supply line 41.
In the heat exchanger main body 30 having the above-described configuration, the diameter R₁ of the water flow channel 47 of the first heat exchange unit 31 is configured to be smaller than the diameter R₂ of the water flow channel 53 of the second heat exchange unit 32.
In this manner, when the diameter R₁ of the water flow channel 47 of the first heat exchange unit 31 is smaller than the diameter R₂ of the water flow channel 53 of the second heat exchange unit 32, a cross-sectional area of the water flow channel 47 of the first heat exchange unit 31 cut along a plane orthogonal to the B-direction can be smaller than a cross-sectional area of the water flow channel 53 of the second heat exchange unit 32 cut along a plane orthogonal to the B-direction.
Accordingly, the flow rate of hot water (water) flowing in the water flow channel 47 of the first heat exchange unit 31 in which the temperature of hot water is high such that scale is likely to be generated becomes higher than the flow rate of water (low-temperature hot water) flowing in the water flow channel 53 of the second heat exchange unit 32. Therefore, in an early stage in which scale is generated in the water flow channel 47 of the first heat exchange unit 31, it is possible to wash the scale out of the first heat exchange unit 31 by utilizing the flow rate of the hot water.
Therefore, the water flow channel 47 of the first heat exchange unit 31 can be retained in an environment in which scale is unlikely to grow. Thus, it is possible to reduce the frequency of maintenance of the heat exchanger 23 required because of scale.
For example, it is advisable to set the sizes of the diameter R₁ of the water flow channel 47 and the diameter R₂ of the water flow channel 53 such that, for example, shear stress becomes equal to or greater than 30 MPa in regard to the flow rate of hot water (water) flowing in the water flow channel 47 of the first heat exchange unit 31. Thus, when such a condition is satisfied, it is possible to further reduce the frequency of maintenance of the heat exchanger 23 required because of scale.
One end of the first connection supply line 35 is connected to the first heat exchange unit 31, and the other end thereof is connected to the second heat exchange unit 32. Refrigerant gas supplied via the first heat exchange unit 31 is guided out to the first connection supply line 35. The refrigerant gas is guided into the second heat exchange unit 32 via the first connection supply line 35.
The valve 36 is provided in the first connection supply line 35 which is disposed on the first heat exchange unit 31 side. The valve 37 is provided in the first connection supply line 35 which is disposed between the valve 36 and the second heat exchange unit 32.
The valves 36, 37 are valves used when performing maintenance of the heat exchanger 23.
The second connection supply line 41 couples the tube 45 shown in FIG. 2 and the tube 51 shown in FIG. 3 together. It is advisable that the inner diameter of the second connection supply line 41 is equal to the inner diameter of the tube 51 (in other words, the diameter of the water flow channel 53).
In this manner, when the inner diameter of the second connection supply line 41 and the inner diameter of the tube 51 are equal to each other, the flow rate of hot water (water) is prevented from being high inside the second connection supply line 41. Therefore, the flow rate of the hot water (water) can become rapidly high inside the first heat exchange unit 31. Accordingly, scale generated inside the water flow channel 47 is unlikely to remain. Thus, it is possible to reduce the frequency of maintenance of the heat exchanger 23 required because of scale.
The valve 42 is provided in the second connection supply line 41 which is disposed on the first heat exchange unit 31 side. The valve 43 is provided in the second connection supply line 41 which is disposed between the valve 42 and the second heat exchange unit 32.
The valves 42, 43 are valves used when performing maintenance of the heat exchanger 23.
With reference to FIG. 1, the hot water storage unit 12 has the hot water storage tank 56, the water supply line 58, the water guide-in line 61, a pump 63, valves 64, 65, the hot water guide-in line 66, and the hot water guide-out line 68.
The hot water storage tank 56 stores hot water in the upper portion thereof and stores water in the lower portion thereof.
The water supply line 58 is a line for supplying water to the lower portion of the hot water storage tank 56 from outside of the water heating system 10. There are cases where the water contains many hardness components such as calcium and magnesium.
One end of the water guide-in line 61 is connected to the lower portion inside the hot water storage tank 56, and the other end thereof is connected to one end of the tube 51. The water guide-in line 61 is configured to supply water stored in the lower portion inside the hot water storage tank 56 to the water flow channel 53 shown in FIG. 3.
The pump 63 is provided in the water guide-in line 61. The pump 63 feeds the water stored in the lower portion inside the hot water storage tank 56 to the water flow channel 53.
The valve 64 is provided in the water guide-in line 61 which is disposed between the pump 63 and the second heat exchange unit 32. The valve 65 is provided in the water guide-in line 61 which is disposed between the hot water storage tank 56 and the second heat exchange unit 32. The valves 64, 65 are used when performing maintenance of the heat exchanger 23.
One end of the hot water guide-in line 66 is connected to the other end of the tube 45 shown in FIG. 2, and the other end thereof is connected to the upper portion of the hot water storage tank 56 (for example, the upper end). The hot water guide-in line 66 is configured to guide high-temperature hot water guided out from the tube 45 into the upper portion of the hot water storage tank 56.
One end of the hot water guide-out line 68 is connected to the upper portion of the hot water storage tank 56 (for example, the upper end), and the other end thereof is connected to a usage target (not shown). The hot water guide-out line 68 is configured to supply hot water stored inside the hot water storage tank 56 to the usage target (not shown).
According to the water heating system 10 of the first embodiment, when the diameter R₁ of the water flow channel 47 of the first heat exchange unit 31 is smaller than the diameter R₂ of the water flow channel 53 of the second heat exchange unit 32, a cross-sectional area of the water flow channel 47 of the first heat exchange unit 31 cut along a plane orthogonal to the B-direction can be smaller than a cross-sectional area of the water flow channel 53 of the second heat exchange unit 32 cut along a plane orthogonal to the B-direction.
Accordingly, the flow rate of hot water (water) flowing in the water flow channel 47 of the first heat exchange unit 31 in which the temperature of hot water is high such that scale is likely to be generated becomes higher than the flow rate of water (low-temperature hot water) flowing in the water flow channel 53 of the second heat exchange unit 32. Therefore, it is possible to inhibit scale from being deposited in the water flow channel 47 of the first heat exchange unit 31.
Therefore, the water flow channel 47 of the first heat exchange unit 31 can be retained in an environment in which scale is unlikely to grow. Thus, it is possible to reduce the frequency of maintenance of the heat exchanger 23 required because of scale.
In addition, when the heat exchanger main body 30 is divided into two heat exchange units (specifically, the first and second heat exchange units 31, 32), for example, the flow rate of water flowing in the water flow channel 47 of the first heat exchange unit 31 may range from 1.5 times to 3.0 times the flow rate of water (hot water) flowing in the water flow channel 53 of the second heat exchange unit 32.
When the flow rate of water flowing in the water flow channel 47 of the first heat exchange unit 31 is lower than 1.5 times the flow rate of water flowing in the water flow channel 53 of the second heat exchange unit 32, there is concern that an effect of washing away the scale will deteriorate.
Meanwhile, when the flow rate of water flowing in the water flow channel 47 of the first heat exchange unit 31 is higher than 3.0 times the flow rate of water flowing in the water flow channel 53 of the second heat exchange unit 32, there is concern that the total value of the pressure loss caused due to lengths L₁, L₂ of the first and second heat exchange units 31, 32 will increase.
Therefore, when the flow rate of water flowing in the water flow channel of the first heat exchange unit ranges from 1.5 times to 3.0 times the flow rate of water flowing in the water flow channel of the second heat exchange unit, the total value of the pressure loss of the first and second heat exchange units is inhibited from increasing, and it is possible to inhibit scale from growing in the water flow channel of the first heat exchange unit.
Moreover, when the heat exchanger main body 30 is divided into two heat exchange units (specifically, the first and second heat exchange units 31, 32), for example, it is advisable that the length L₁ of the first heat exchange unit 31 in the X-direction is equal to or shorter than 0.5 times the length L₂ of the second heat exchange unit 32 in the X-direction.
When the length L₁ of the first heat exchange unit 31 in the X-direction is longer than 0.5 times the length L₂ of the second heat exchange unit 32 in the X-direction, the length of the water flow channel 53 of the second heat exchange unit 32 is lengthened. Accordingly, the length of the water flow channel 47 of the first heat exchange unit 31 is lengthened, so that the pressure loss in the first heat exchange unit 31 increases. Thus, there is concern that the total pressure loss of the first and second heat exchange units 31, 32 will increase.
Therefore, when the length L₁ of the first heat exchange unit 31 is equal to or shorter than 0.5 times the length L₂ of the second heat exchange unit 32, the pressure loss in the first heat exchange unit 31 is reduced, and it is possible to sufficiently inhibit scale from growing in the water flow channel 47 of the first heat exchange unit 31.
In the first embodiment, as an example, descriptions are given of an exemplary case where the tubes 45, 51 are provided only one each, and the water flow channels 47, 53 are provided one each. However, the same numbers of tubes 45, 51 may be provided, and the same numbers of water flow channels 47, 53 may be provided.
In this case, it is advisable to have a configuration such that the total cross-sectional area of a plurality of water flow channels 47 of the first heat exchange unit 31 cut along a plane orthogonal to the B-direction becomes smaller than the total cross-sectional area of a plurality of water flow channels 53 of the second heat exchange unit 32 cut along a plane orthogonal to the B-direction.
In such a configuration, the flow rate of hot water (water) flowing in the plurality of water flow channels 47 becomes higher than the flow rate of water (low-temperature hot water) flowing in the plurality of water flow channels 53. Thus, it is possible to inhibit scale from being deposited in the plurality of water flow channels 47. Accordingly, it is possible to reduce the frequency of maintenance of the heat exchanger 23 required because of scale.
Moreover, for example, the number of water flow channels 47 of the first heat exchange unit 31 may be less than the number of water flow channels 53 of the second heat exchange unit 32.
Even in such a case, the total cross-sectional area of the water flow channels 47 of the first heat exchange unit 31 cut along a plane orthogonal to the B-direction becomes smaller than the total cross-sectional area of the water flow channels 53 of the second heat exchange unit 32 cut along a plane orthogonal to the B-direction.
Accordingly, water (hot water) flowing inside the water flow channel 53 of the second heat exchange unit 32 is unlikely to flow inside the water flow channel 47 of the first heat exchange unit 31, and the flow rate of hot water flowing inside the water flow channels 47 of the first heat exchange unit 31 can be higher than the flow rate of water flowing inside the water flow channels 53 of the second heat exchange unit 32. Therefore, it is possible to inhibit scale from growing inside the water flow channels 47 of the first heat exchange unit 31.
FIG. 4 is a system diagram showing a schematic configuration of a water heating system according to a modification example of the first embodiment of the present invention. In FIG. 4, the same reference signs are applied to configuration parts the same as in the structure shown in FIG. 1.
With reference to FIG. 4, a water heating system 70 of the modification example of the first embodiment has a configuration similar to that of the water heating system 10, except for having a refrigerant unit 71 in place of the refrigerant unit 11 configuring the water heating system 10 of the first embodiment.
The refrigerant unit 71 has a configuration similar to that of the refrigerant unit 11, except for having a heat exchanger 73 in place of the heat exchanger 23 configuring the refrigerant unit 11 described in the first embodiment.
The heat exchanger 73 has a configuration similar to that of the heat exchanger 23 described in the first embodiment, except for including a heat exchanger main body 75 which is divided into three in the X-direction and has first to third heat exchange units 76 to 78, and having two structures each of which is constituted by the first connection supply line 35, the valves 36, 37, 42, 43, and the second connection supply line 41.
The first to third heat exchange units 76 to 78 are arranged in the X-direction in a state of being separated from one another. The first heat exchange unit 76 has the water flow channel 47 shown in FIG. 2.
The second heat exchange unit 77 is disposed between the first heat exchange unit 76 and the third heat exchange unit 78. The second heat exchange unit 77 has the water flow channel 53 shown in FIG. 3.
The third heat exchange unit 78 is connected to the refrigerant circulation line 15 and the water guide-in line 61. The third heat exchange unit 78 has a configuration similar to that of the second heat exchange unit 77.
Water guided into the third heat exchange unit 78 is supplied to the third heat exchange unit 78 via the second heat exchange unit 77. The refrigerant supplied to the third heat exchange unit 78 is supplied to the first heat exchange unit 76 via the second heat exchange unit 77.
The structures each of which is constituted by the first connection supply line 35, the valves 36, 37, 42, 43, and the second connection supply line 41 are each provided between the first heat exchange unit 76 and the second heat exchange unit 77, and between the second heat exchange unit 77 and the third heat exchange unit 78.
One of two structures connects the first heat exchange unit 76 and the second heat exchange unit 77, and the other connects the second heat exchange unit 77 and the third heat exchange unit 78.
The first to third heat exchange units 76 to 78 disposed in the X-direction are connected in series by the two structures.
As in the heat exchanger 73 described above, the heat exchanger main body 75 may be divided into three. The water heating system 70 of the modification example of the first embodiment having such a configuration can attain an effect similar to that of the water heating system 10 of the first embodiment.
In addition, in FIG. 4, as an example, descriptions are given of an exemplary case where the heat exchanger main body 75 is divided into three. However, the heat exchanger main body 75 may be divided into four or more, as necessary. That is, the configuration is acceptable as long as the heat exchanger main body 75 is divided into at least two (at least a high-temperature side and a low-temperature side) or more.
FIG. 5 is a cross-sectional view showing an alternative example of the first heat exchange unit. FIG. 6 is a cross-sectional view showing an alternative example of the second heat exchange unit. In FIGS. 5 and 6, first and second heat exchange units 81, 91 are shown of an exemplary case where a layered plate-type heat exchanger is employed. In addition, in FIG. 6, the same reference signs are applied to configuration parts the same as in the structure shown in FIG. 5.
In FIGS. 2 and 3 described above, the first and second heat exchange units 31, 32 are described of an exemplary case where the tube-type heat exchanger is employed. However, for example, the layered plate-type heat exchanger having the first and second heat exchange units 81, 91 shown in FIGS. 5 and 6 may be employed.
Here, with reference to FIGS. 5 and 6, the first and second heat exchange units 81, 91 will be described in order.
The first heat exchange unit 81 has a three-layer configuration in which a first plate 85 and a second plate 86 are alternately layered on a base plate 83 in this order. The first heat exchange unit 81 has refrigerant flow channels 87 and water flow channels 88.
In each of the first plates 85, recessed portions 85A extending in the predetermined direction (the X-direction shown in FIG. 1) are disposed at predetermined intervals in a direction orthogonal to the predetermined direction. The first plates 85 are disposed on the base plate 83 such that the recessed portions 85A face the base plate 83. The refrigerant flow channels 87 are defined by the top surface of the base plate 83 and the recessed portions 85A and function as flow channels in which the refrigerant flows.
In the second plate 86, recessed portions 86A extending in the predetermined direction (the X-direction shown in FIG. 1) are disposed at predetermined intervals in the direction orthogonal to the predetermined direction. The second plate 86 is disposed on the first plate 85 such that the recessed portions 86A face the first plate 85.
The water flow channels 88 are defined by the top surface of the first plate 85 and the recessed portions 86A and function as water flow channels in which water flows.
The second heat exchange unit 91 has a three-layer configuration in which a first plate 92 and a second plate 93 are alternately layered on the base plate 83 in this order. The second heat exchange unit 91 has refrigerant flow channels 95 and water flow channels 96.
The first plates 92 have configurations similar to those of the first plates 85 described above. The first plates 92 are disposed on the base plate 83 such that a plurality of recessed portions 85A face the base plate 83. The refrigerant flow channels 95 are defined by the top surface of the base plate 83 and the recessed portions 85A, and the refrigerant flows therein.
In the second plate 93, recessed portions 93A extending in the predetermined direction (the X-direction shown in FIG. 1) are disposed at predetermined intervals in the direction orthogonal to the predetermined direction. The second plate 93 is disposed on the first plate 92 such that the recessed portions 93A face the top surface of the first plate 92.
The water flow channels 96 are defined by the top surface of the first plate 92 and the recessed portions 93A, and water flows therein.
In the first and second heat exchange units 81, 91 described above, for example, it is advisable that the recessed portions 85A, 93A are the same as one other in width and depth and the recessed portion 86A has a width and a depth smaller than the widths and the depths of the recessed portions 85A, 93A.
In such a configuration, the total value of the cross-sectional areas of a plurality of water flow channels 88 when cut along a plane orthogonal to the predetermined direction (the X-direction shown in FIG. 1) can be smaller than the total value of the cross-sectional areas of a plurality of water flow channels 96 when cut along a plane orthogonal to the predetermined direction (the X-direction shown in FIG. 1).
Accordingly, the flow rate of hot water (water) flowing in the plurality of water flow channels 88 can be higher than the flow rate of water flowing inside the plurality of water flow channels 96. Therefore, it is possible to inhibit scale from growing inside the water flow channels 88 of the first heat exchange unit 81.
FIG. 7 is a cross-sectional view showing another alternative example of the first heat exchange unit. In FIG. 7, the same reference signs are applied to configuration parts the same as in the structures shown in FIGS. 5 and 6.
FIG. 8 is a cross-sectional view showing another alternative example of the second heat exchange unit. In FIG. 8, the same reference signs are applied to configuration parts the same as in the structures shown in FIGS. 5 to 7. In FIGS. 7 and 8, first and second heat exchange units 100, 105 are shown in exemplary cases in which the layered plate-type heat exchanger is employed.
Here, with reference to FIGS. 7 and 8, the first and second heat exchange units 100, 105 will be described in order.
The first heat exchange unit 100 has a three-layer configuration in which the first plate 85 and a second plate 101 are alternately layered on the base plate 83 in this order. The first heat exchange unit 100 has the refrigerant flow channels 87 and water flow channels 102.
In the second plate 101, recessed portions 101A extending in the predetermined direction (the X-direction shown in FIG. 1) are disposed at predetermined intervals in the direction orthogonal to the predetermined direction. The second plate 101 is disposed on the first plate 85 such that the recessed portions 101A face the first plate 85.
The water flow channels 102 are defined by the top surface of the first plate 85 and the recessed portions 101A and function as water flow channels in which water flows.
The second heat exchange unit 105 has a five-layered configuration in which a first plate 106 and a second plate 107 are alternately layered on the base plate 83 in this order. The second heat exchange unit 105 has refrigerant flow channels 108 and water flow channels 109.
The first plates 106 have configurations similar to those of the first plates 85 described above. The first plates 106 are disposed on the base plate 83 such that the plurality of recessed portions 85A face the base plate 83. The refrigerant flow channels 108 are defined by the top surface of the base plate 83 and the recessed portions 85A, and the refrigerant flows therein.
In the second plates 107, recessed portions 107A extending in the predetermined direction (the X-direction shown in FIG. 1) are disposed at predetermined intervals in the direction orthogonal to the predetermined direction. Each of the second plates 107 is disposed on the first plate 106 such that the recessed portions 107A face the top surface of the first plate 106.
The water flow channels 109 are defined by the top surface of the first plate 106 and the recessed portions 107A, and water flows therein.
In the first and second heat exchange units 100, 105 described above, for example, it is advisable that the recessed portions 85A, 101A, 107A are the same as one another in width and depth.
In such a configuration, the total value of the cross-sectional areas of a plurality of water flow channels 102 when cut along a plane orthogonal to the predetermined direction (the X-direction shown in FIG. 1) can be smaller than the total value of the cross-sectional areas of a plurality of water flow channels 109 when cut along a plane orthogonal to the predetermined direction (the X-direction shown in FIG. 1).
Accordingly, the flow rate of hot water (water) flowing in the plurality of water flow channels 102 can be higher than the flow rate of water flowing inside the plurality of water flow channels 109. Therefore, it is possible to inhibit scale from growing inside the water flow channels 109 of the first heat exchange unit 100.

(Second Embodiment)

FIG. 9 is a system diagram showing a schematic configuration of a water heating system according to a second embodiment of the present invention. In FIG. 9, the same reference signs are applied to configuration parts the same as in the water heating system 10 of the first embodiment shown in FIG. 1.
With reference to FIG. 9, a water heating system 120 of the second embodiment has a refrigerant unit 121, a water circulation unit 122, and the hot water storage unit 12.
The refrigerant unit 121 has the refrigerant circulation line 15, the expansion valve 17, the vaporizer 18, the compressor 21, and a first heat exchanger 125.
One end of the refrigerant circulation line 15 is connected to one end of the first heat exchanger 125, and the other end thereof is connected to the other end of the first heat exchanger 125.
The first heat exchanger 125 is configured to perform heat exchange between a refrigerant (for example, CO₂) flowing in the refrigerant circulation line 15 and first water circulating inside the water circulation unit 122 and is configured to turn the first water into first hot water.
The water circulation unit 122 has a water circulation line 127, the valves 25, 26, a second heat exchanger 128, and a pump 129.
The water circulation line 127 is a line configured to be a closed loop and to cause the first water to circulate. The water circulation line 127 connects the first heat exchanger 125 and the second heat exchanger 128. The water circulation line 127 is configured to cause the first water to circulate in the first and second heat exchangers 125, 128.
As described above, when the water circulation line 127 in which the first water circulates is caused to be the closed loop, water containing many hardness components such as calcium and magnesium is no longer supplied to the first heat exchanger 125 from outside of the water heating system 120. Therefore, scale is inhibited from growing on a high-temperature side inside the first heat exchanger 125. Therefore, there is no need for the first heat exchanger 125 to be divided into a plurality of units as in the heat exchanger 23 described in FIG. 1.
The first heat exchanger 125 is a heat exchanger requiring a frequency of maintenance lower than that of the second heat exchanger 128.
The valve 25 is provided in the water circulation line 127 which is positioned on an exit side (a side from which the first hot water is guided out) of the second heat exchanger 128. The valve 26 is provided in the water circulation line 127 which is positioned on an entrance side (a side into which the first water is guided) of the second heat exchanger 128.
The second heat exchanger 128 has a configuration similar to that of the heat exchanger 23 shown in FIG. 1. As the first and second heat exchange units 31, 32 configuring the second heat exchanger 128, for example, it is possible to employ heat exchange units having the structures shown in FIGS. 2, 3, and 5 to 8.
The second heat exchanger 128 is connected to the water guide-in line 61 and the hot water guide-in line 66 configuring the hot water storage unit 12. Accordingly, second water is supplied to the second heat exchanger 128 from the hot water storage tank 56.
The second heat exchanger 128 is configured to perform heat exchange between the first hot water guided out from the first heat exchanger 125 and the second water supplied via the water guide-in line 61 and is configured to turn the second water into second hot water. The second hot water is guided out from the first heat exchange unit 31, and then, the second hot water is guided into the upper portion of the hot water storage tank 56.
According to the water heating system 120 of the second embodiment, when the second heat exchanger 128 divided into a plurality of units (in the case of FIG. 9, two) is provided outside the refrigerant unit 121, it is possible to easily perform maintenance of the second heat exchanger 128.
In addition, the water heating system 120 of the second embodiment having the above-described configuration can attain an effect similar to that of the water heating system 10 of the first embodiment.
In the second embodiment, as an example of the second heat exchanger 128, descriptions are given of an exemplary case of being provided with the heat exchanger 23 shown in FIG. 1. However, in place thereof, the heat exchanger 73 shown in FIG. 7 may be employed.
In the second embodiment, the second heat exchanger 128 is acceptable as long as the heat exchanger main body 30 is divided into two or more parts.
Hereinabove, preferable embodiments of the present invention have been described in detail. The present invention is not limited to such particular embodiments, and various modifications and changes can be made within the scope of the gist of the present invention disclosed in claims.
Hereinafter, experimental examples will be described. The present invention is not limited to the details of Examples 1 to 4 described in the experimental examples.

(Experimental Examples)

In the experimental examples, an examination was carried out, under the conditions that a length L (= L₁ + L₂) of the heat exchanger main body 30 in the X-direction before being divided as in FIG. 1 was set to 1, a flow rate S in the heat exchanger main body 30 before being divided was set to 1, and an entire pressure loss P in the heat exchanger main body 30 before being divided was set to 1 (Comparative Example), regarding the pressure loss of the first and second heat exchange units 31, 32; the total pressure loss of the first and second heat exchange units 31, 32; and the multiple of the flow rate of the first heat exchange unit with respect to the flow rate of the second heat exchange unit 32, when the lengths L₁, L₂ of the first and second heat exchange units 31, 32 and the flow rate in the second heat exchange unit 32 varied. In this case, the pressure loss was calculated with the flow rate which was squared and was proportional to the length.
In Examples 1 and 2, the length L₁ of the first heat exchange unit 31 was set to 0.5, and the length L₂ of the second heat exchange unit 32 was set to 0.5. In Example 3, the length L₁ of the first heat exchange unit 31 was set to 0.4, and the length L₂ of the second heat exchange unit 32 was set to 0.6. In Example 4, the length L₁ of the first heat exchange unit 31 was set to 0.3, and the length L₂ of the second heat exchange unit 32 was set to 0.7.
In addition, in Example 1, the flow rate of water flowing inside the second heat exchange unit 32 was set to 0.8 (80% of the flow rate of water flowing inside the heat exchanger main body of Comparative Example). In Example 2, the flow rate of water flowing inside the second heat exchange unit 32 was set to 0.7. In Example 3, the flow rate of water flowing inside the second heat exchange unit 32 was set to 0.6.
Table 1 shows the results of the experimental examples.
[Table 1]
With reference to Table 1, in Example 1, the flow rate in the first heat exchange unit 31 was 1.5 times the flow rate in the second heat exchange unit 32, and the total pressure loss was 1.04 being close to 1. According to the results, in Example 1, the flow rate in the first heat exchange unit 31 was a sufficient flow rate, and the result for the total pressure loss was also an extremely satisfactory value.
In Example 2, although the result for the total pressure loss was a value slightly higher than that in Example 1, the flow rate in the first heat exchange unit 31 was 3.0 times the flow rate in the second heat exchange unit 32, and satisfactory results were achieved.
In Example 3, result for the total pressure loss was 1.0, which was a value slightly lower than that in Example 2. The flow rate in the first heat exchange unit 31 was 2.33 times the flow rate in the second heat exchange unit 32, and satisfactory results were achieved.
In Example 4, the flow rate in the first heat exchange unit 31 was 3.0 times the flow rate in the second heat exchange unit 32, and the total pressure loss was 0.85 being lower than 1. According to the results, in Example 4, the flow rate in the first heat exchange unit 31 was a sufficient flow rate, and the result for the total pressure loss was also an extremely satisfactory value.
The length L₁ of the first heat exchange unit 31 in Example 4 was 0.3 times the length L of the heat exchanger main body 30. The location where scale precipitated was the first heat exchange unit 31 in which the temperature of water rose to 60°C or higher. Depending on the conditions of the entrance water temperature and the exit water temperature, the ratio of the length being 0.3 times the length L of the heat exchanger main body 30 could be realized.
According to the results of Examples 1 to 4, it was ascertained that the flow rate in the first heat exchange unit 31 can be sufficiently higher than (be 1.5 times or more than) the flow rate in the second heat exchange unit 32 when the length L₁ of the first heat exchange unit 31 is equal to or shorter than 0.5 times the entire length including the length L₂ of the second heat exchange unit 32, in a case where the heat exchanger main body 30 is divided into two units. In other words, it was ascertained that scale can be inhibited from growing in the first heat exchange unit 31.
In addition, according to the results of Examples 1 to 3, from the viewpoint of reducing the total pressure loss, it was possible to confirm that the flow rate of water flowing in the water flow channel of the first heat exchange unit 31 preferably ranges from 1.5 times to 3.0 times the flow rate of water flowing in the water flow channel of the second heat exchange unit 32.
While preferred embodiments of the invention have been described and shown above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.

EXPLANATION OF REFERENCES

10, 70, 120 Water heating system
11, 71, 121 Refrigerant unit
12 Hot water storage unit
15 Refrigerant circulation line
17 Expansion valve
18 Vaporizer
21 Compressor
23, 73 Heat exchanger
23A One end
23B Other end
25, 26, 36, 37, 42, 43, 64, 65 Valve
30, 75 Heat exchanger main body
31, 81, 100 First heat exchange unit
32, 91, 105 Second heat exchange unit
35 First connection supply line
41 Second connection supply line
45, 51 Tube
46, 52 Plate
47, 53, 88, 96, 102, 109 Water flow channel
56 Hot water storage tank
58 Water supply line
61 Water guide-in line
63, 129 Pump
66 Hot water guide-in line
68 Hot water guide-out line
78 Third heat exchange unit
83 Base plate
85, 92, 106 First plate
85A, 86A, 93A, 96A, 101A Recessed portion
86, 93, 101, 107 Second plate
87, 95, 108 Refrigerant flow channel
122 Water circulation unit
125 First heat exchanger
127 Water circulation line
128 Second heat exchanger
A, B, X Direction
L₁, L₂ Length
R₁, R₂ Diameter

Claims

A water heating system (10, 70) comprising:
a refrigerant unit (11, 71) that includes
a refrigerant circulation line (15) in which a refrigerant circulates,

a vaporizer (18) which is provided in the refrigerant circulation line, is configured to vaporize the liquid refrigerant decompressed by an expansion valve (17), and is configured to generate refrigerant gas,

a compressor (21) which is provided in the refrigerant circulation line, and is configured to compress the refrigerant gas guided out from the vaporizer, and

a heat exchanger (23, 73) which is provided in the refrigerant circulation line, is configured to provide heat exchange between the refrigerant gas guided out from the compressor and water, and is configured to turn the water into hot water; and

a hot water storage unit (12) that includes
a hot water storage tank (56) which stores the hot water,

a water guide-in line (61) which is configured to guide the water stored in a lower portion inside the hot water storage tank into the heat exchanger through one end of the heat exchanger (23A),

a hot water guide-in line (66) which is connected to the other end of the heat exchanger (23B) and is configured to guide the hot water to an upper portion of the hot water storage tank, and

a water supply line (58) which is configured to supply water from outside to the lower portion inside the hot water storage tank,

wherein the heat exchanger has a plurality of heat exchange units (31, 32, 81, 91, 100, 105) which are separated from each other in a predetermined direction and are connected to each other in series,

wherein the plurality of heat exchange units each include at least one water flow channel (47,53, 88, 96, 102, 109) in which the water flows,

wherein the plurality of heat exchange units include at least a first heat exchange unit (31, 81, 100) configuring the other end of the heat exchanger, and a second heat exchange unit (32, 91, 105) being disposed in the vicinity of the first heat exchange unit in a direction in which the water flows, and

wherein a total cross-sectional area of the water flow channel of the first heat exchange unit cut along a plane orthogonal to the direction in which the water flows is smaller than a total cross-sectional area of the water flow channel of the second heat exchange unit cut along a plane orthogonal to the direction in which the water flows.
The water heating system (10, 70) according to claim 1,
wherein a diameter of the water flow channel of the first heat exchange unit (R₁) is smaller than a diameter of the water flow channel of the second heat exchange unit (R₂).
The water heating system according to claim 1 or 2,
wherein the number of water flow channels of the first heat exchange unit (47, 88, 102) is less than the number of water flow channels of the second heat exchange unit (53, 96, 109).
The water heating system (10, 70) according to any one of claims 1 to 3,
wherein the heat exchanger (23, 73) is divided into two units and is configured to include the first heat exchange unit (31, 81, 100)and the second heat exchange unit (32, 91, 105), and
wherein a flow rate of the water flowing in the water flow channel of the first heat exchange unit (47, 88, 102) ranges from 1.5 times to 3.0 times a flow rate of the water flowing in the water flow channel of the second heat exchange unit (53, 96, 109) .
The water heating system according to claim 4,
wherein a length (L₁) of the first heat exchange unit in the predetermined direction is equal to or shorter than 0.5 times a length of the heat exchanger that is a sum total of a length (L₂) of the second heat exchange unit in the predetermined direction and the length of the first heat exchange unit.
A water heating system (120) comprising:
a refrigerant unit (121) that includes
a refrigerant circulation line (15) in which a refrigerant circulates,

a vaporizer (18) which is provided in the refrigerant circulation line, is configured to vaporize the liquid refrigerant decompressed by an expansion valve, and is configured to generate refrigerant gas,

a compressor (21) which is provided in the refrigerant circulation line, and is configured to compress the refrigerant gas guided out from the vaporizer, and

a first heat exchanger (125) which is provided in the refrigerant circulation line, is configured to perform heat exchange between the refrigerant gas guided out from the compressor and first water, and is configured to turn the first water into first hot water;

a water circulation unit (122) that includes
a water circulation line (127) which is configured to be a closed loop such that the first water circulates, and to cause the first water to circulate in the first heat exchanger, and

a second heat exchanger (128) which is provided in the water circulation line, is configured to perform heat exchange between the first hot water and second water, and is configured to turn the second water into second hot water; and

a hot water storage unit (12) that includes
a hot water storage tank (56) which stores the second hot water,

a water guide-in line (61) which is configured to guide the second water stored in a lower portion inside the hot water storage tank into the second heat exchanger through one end of the second heat exchanger,

a hot water guide-in line (66) which is connected to an other end of the second heat exchanger (23B) and is configured to guide the second hot water to an upper portion inside the hot water storage tank, and

a water supply line (58) which is configured to supply the second water from outside to the lower portion inside the hot water storage tank,

wherein the second heat exchanger has a plurality of heat exchange units (31, 32) which are separated from each other in a predetermined direction and are connected to each other in series,

wherein the plurality of heat exchange units each include at least one water flow channel (47, 53) in which the second water flows,

wherein the plurality of heat exchange units include at least a first heat exchange unit (31) configuring the other end of the second heat exchanger, and a second heat exchange unit (32) being disposed in the vicinity of the first heat exchange unit in a direction in which the second water flows, and

wherein a total cross-sectional area of the water flow channel of the first heat exchange unit cut along a plane orthogonal to the direction in which the second water flows is smaller than a total cross-sectional area of the water flow channel of the second heat exchange unit cut along a plane orthogonal to the direction in which the second water flows.
The water heating system according to claim 6,
wherein a diameter (R₁) of the water flow channel of the first heat exchange unit is smaller than a diameter (R₂) of the water flow channel of the second heat exchange unit.
The water heating system according to claim 6 or 7,
wherein the number of water flow channels of the first heat exchange unit is less than the number of water flow channels of the second heat exchange unit.