EP3130867B1

EP3130867B1 - Heat pump type water heater system

Info

Publication number: EP3130867B1
Application number: EP15180480.4A
Authority: EP
Inventors: Jose Acedo Navarrete; Ruben Martinez; Javier Vicente Ortiz de Guinea; Loreto Ganuza; Iker Altuzarra; Illan Arribas
Original assignee: Vaillant GmbH
Current assignee: Vaillant GmbH
Priority date: 2015-08-11
Filing date: 2015-08-11
Publication date: 2018-11-07
Anticipated expiration: 2035-08-11
Also published as: ES2709011T3; EP3130867A1

Description

FIELD OF THE INVENTION

The present invention relates to a heat pump type water heater system that heats water in a water tank by a heat pump unit and supplies the heated water from the water tank.

BACKGROUND OF THE INVENTION

Fig. 3 discloses a conventional heat pump type water heater system. The system has a casing enclosing a refrigerant circuit and a water tank 97 disposed below the casing. The refrigerant circuit includes a compressor 91 compressing refrigerant to obtain refrigerant of high temperature and high pressure, a water/refrigerant heat exchanger 92 (condenser) condensing the refrigerant of high temperature and high pressure to release heat from the refrigerant to the water to be entering the water tank 97, an expansion valve (now shown) depressurizing the highpressure refrigerant that is condensed by the water/refrigerant heat exchanger 92, and an air/refrigerant heat exchanger 93 (evaporator) evaporating the refrigerant that is depressurized by the expansion valve to absorb heat from air that is supplied via a fan 94. An electronic board 95 is also enclosed in the casing for controlling active components, such as the compressor 91 and the fan 94. European patent application publications EP2672190A1 and EP2860469A1 each discloses a heat pump system employing a water container in heat exchange with a water/refrigerant heat exchanger of the heat pump for producing sanitary hot water.
In such a heat pump type water heater system, depending on the water quality, scale can be built up in the water tank, water pipes, and the water/refrigerant heat exchanger, which may lead to degradation of performance. This is particularly significant for the water/refrigerant heat exchanger, because the water passage of the water/refrigerant heat exchanger has a quite small sectional area, and scale deposition in the water passage can cause pressure drops, heat flux reduction, or even water flow blocking.

SUMMARY OF THE INVENTION

It is an object of present invention to provide a heat pump type water heater system that has a descaling mode for avoidance of formation of scales in the water/refrigerant heat exchanger.
According to the present invention there is provided a heat pump type water heater system including a refrigerant circuit having a water/refrigerant heat exchanger for condensing a refrigerant to release heat from the refrigerant to water passing through the water/refrigerant heat exchanger; a water tank that stores water capable of passing through the water/refrigerant heat exchanger to obtain heat from the refrigerant when the refrigerant circuit is working; and a cold water reservoir that stores cold water capable of passing through the water/refrigerant heat exchanger when the refrigerant circuit is not working. The system further includes a divert valve combinations connected with the water/refrigerant heat exchanger, a circulation pump connected with the divert valve combinations, a first incoming line and a first outgoing line connected between the divert valve combinations and the water tank, and a second incoming line and a second outgoing line connected between the divert valve combinations and the cold water reservoir. Moreover, a controller is configured to operate the divert valve combinations and the circulation pump to work in a heating mode that water within the water tank passes through the water/refrigerant heat exchanger to obtain heat when the refrigerant circuit is working, and configured to operate the divert valve combinations and the circulation pump to work in a descaling mode that cold water within the cold water reservoir passes through the water/refrigerant heat exchanger to remove scales formed in the water/refrigerant heat exchanger when the refrigerant circuit is not working. In this way, cold water from the cold water reservoir in addition to the water tank passes through the water/refrigerant heat exchanger when the refrigerant circuit is not working to avoid formation of scales and/or remove scales existing in the water/refrigerant heat exchanger.
In one embodiment, the system is operable to work in a heating mode that water within the water tank passes through the water/refrigerant heat exchanger to obtain heat when the refrigerant circuit is working, and operable to work in a descaling mode that cold water within the cold water reservoir passes through the water/refrigerant heat exchanger to remove scales formed in the water/refrigerant heat exchanger when the refrigerant circuit is not working.
Moreover, the system includes a divert valve combinations connected with the water/refrigerant heat exchanger, a circulation pump connected with the divert valve combinations, a first incoming line and a first outgoing line connected between the divert valve combinations and the water tank, and a second incoming line and a second outgoing line connected between the divert valve combinations and the cold water reservoir.
Preferably, the divert valve combinations includes a first three way valve, a second three way valve, and a third three way valve sequentially connected, and a fourth three way valve; wherein the third three way valve and the fourth three way valve are connected to the water/refrigerant heat exchanger respectively.
Preferably, the first outgoing line is connected to one port of the first three way valve, and the second outgoing line is connected to another port of the first three way valve; wherein the first incoming line is connected to one port of the fourth three way valve, and the second incoming line is connected to one port of the third three way valve.
When the system is working in the heating mode, water within the water tank is extracted via the first outgoing line and sequentially passes through the first, the second, and the third three way valves, and enters the water/refrigerant heat exchanger for obtaining heat, then the heated water passes through the fourth three way valve and returns into the water tank via the first incoming line; when the system is working in the descaling mode, cold water within the cold water reservoir is extracted via the second outgoing line and sequentially passes through the first, the second, and the fourth three way valves, and enters the water/refrigerant heat exchanger for removing scales therein, then the cold water passes through the third three way valve and returns into the cold water reservoir via the second incoming line.
In a preferred embodiment, the circulation pump works at a maximum output when the system is working in the descaling mode. On one hand, high rates of water flow is positive to the scale removal, and on the other hand, at the time the system being switched from the heating mode to the descaling mode, the water/refrigerant heat exchanger is still hot, therefore, water flow fast passing through the water/refrigerant heat exchanger can avoid temperature increasing of cold water returning to the cold water reservoir.
The system further includes a temperature sensor positioned in a lower zone of the water tank; wherein when the temperature sensor detects that the temperature of water within the water tank is equal to or larger than a predetermined threshold, the system will be switched from the heating mode to the descaling mode. This is because scale components are more likely to be generated in water at a high temperature. Therefore, when the temperature of hot water in the tan reaches the predetermined threshold, the descaling mode is needed to avoid the formation of the scales therein, and in the meantime, the water flow can remove existing scales.
Generally, the volume of the cold water reservoir (Vreservoir) equals the sum of the volumes (Vtotal) of the water/refrigerant heat exchanger, the circulation pump, and water pipes connected in the divert valve combinations and between the divert valve combinations and the water/refrigerant heat exchanger. However, in some cases, for example in regions where tap water has a very high hardness, Vreservoir can be defined as larger than Vtotal.
In a preferred embodiment, the water tank and the cold water reservoir are disposed in a same water container, and the cold water reservoir locates below and is usually isolated with the water tank; wherein a pressure valve is disposed between the water tank and the cold water reservoir to automatically open a water path therebetween when water within the water tank is extracted for sanitary usages.
Preferably, the temperature of cold water within the cold water reservoir is generally much smaller than that of water within the water tank.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a diagram showing the configuration of a heat pump type water heater system in accordance with one embodiment of present invention; wherein some components, such as a compressor, an expansion valve, and an evaporator are hidden in order to show a divert valve combinations, and the system is working in a heating mode;
Fig. 2 is a diagram similar to Fig. 1, wherein the system is working in a descaling mode;
Fig. 3 is a diagram showing the configuration of a heat pump type water heater system in the state of art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawing figures to describe the preferred embodiments of the present invention in detail. However, the embodiments can not be used to restrict the present invention. Changes such as structure, method and function obviously made to those of ordinary skill in the art are also protected by the present invention.
Referring to Fig. 1, in one embodiment of present invention, a heat pump type water heater system 100 can stand on the floor with a water container 60 located below a casing enclosing a refrigerant circuit therein. The casing is composed by top, side, and bottom walls, and an air inlet and an air outlet are defined in the top wall for respectively introducing and exhausting air therethrough. The water container 60 has an upper portion defined as a water tank 61 and a lower portion defined as a cold water reservoir 62. The configuration of the refrigerant circuit and the structures of the water tank 61 and cold water reservoir 62 will be described in details hereinafter.
The refrigerant circuit typically has a compressor (not shown), a water/refrigerant heat exchanger (condenser) 10, an expansion valve (now shown), and an air/refrigerant heat exchanger (evaporator, not shown) 23. These components are generally serially connected via conduits are well known in the art. During operation of the refrigerant circuit, the compressor acts on relatively cool gaseous refrigerant to raise the temperature and pressure of the refrigerant. From the compressor, the high temperature, high pressure gaseous refrigerant flows into the water/refrigerant heat exchanger 10 where it is cooled and exits the water/refrigerant heat exchanger 10 as a high pressure liquid refrigerant. The water/refrigerant heat exchanger 10 is a plate type heat exchanger using metal plates to transfer heat between the two fluids, and it performs as a heat source for the water tank 61. The water/refrigerant heat exchanger 10 typically has two passages respectively for water and refrigerant. Water extracted from the water tank 61 can pass through the water/refrigerant heat exchanger 10 to be heated by the refrigerant in a non-contact way, and then the heated water flows back and is stored within the tank 61.
The high pressure liquid refrigerant then flows to the expansion device, which controls the amount of refrigerant entering into the air/refrigerant heat exchanger. The air/refrigerant heat exchanger can take form of a finned tube heat exchanger typically having copper tube coils that are accompanied by aluminum fins for purpose of maximizing heat transfer between the refrigerant and air mediums. A centrifugal fan (not shown) is disposed adjacent to the air/refrigerant heat exchanger for being operable to generate forced air passing through tube coils and fins of the air/refrigerant heat exchanger. In the air/refrigerant heat exchanger, the low temperature refrigerant absorbs heat from air blown over the tube coils and the fins, and exits the appliance via the air outlet. The suction of the compressor then draws the gaseous refrigerant back to the compressor where the cycle begins again.
A divert valve combinations is disposed in the casing and connected with the water/refrigerant heat exchanger 10, and a circulation pump 50 is connected with the divert valve combinations. In this embodiment, the divert valve combinations includes a first three way valve 31, a second three way valve 32, and a third three way valve 33 sequentially connected, and a fourth three way valve 34. The third three way valve 33 and the fourth three way valve 34 are connected to the water/refrigerant heat exchanger 10 respectively to in fluid communication with the water passage therein. A number of water pipes are connected among the four three way valves 31, 32, 33, 34 and between the third, the fourth three way valves 33, 34 and the water/refrigerant heat exchanger 10. The circulation pump 50 is connected between the first and the second three way valves 31, 32.
A first outgoing line 41 has one end connected to one port of the first three way valve 31 and the other end located inside and at a lower portion of the water tank 61. A first incoming line 42 has one end connected to one port of the fourth three way valve 34 and the other end located inside and at an upper portion of the water tank 61. A second outgoing line 43 has one end connected to another port of the first three way valve 31 and the other end located inside and at a lower portion of the cold water reservoir 62. A second incoming line 44 has one end connected one port of the third three way valve 33 and the other end located inside and at an upper portion of the cold water reservoir 62.
In the water container 60, the cold water reservoir 62 locates below the water tank 61 and they are usually isolated. The cold water reservoir 62 is connected with a tap water for introducing cold water at an environment temperature, generally within 10-15 °C . The boundary between the water tank 61 and the cold water reservoir 62 can be heat insulated to avoid a heat transfer therebetween. The term "cold water" may be defined as the water within the reservoir 62 having a temperature that is generally much smaller than a temperature of water within the water tank 61. Because the temperature of water within water tank 61 can be heated to and kept at a quite high value, such as within 55-65 °C. A pressure valve 63 is disposed at the boundary between the water tank 61 and the cold water reservoir 62 to automatically open a water path therebetween when water within the water tank 61 is extracted for sanitary usages, like drinking, washing, showing, and etc. In a preferred embodiment, the pressure valve 63 is a mechanical check valve that can sense pressure difference between the water tank 61 and the cold water reservoir 62. When water in the water tank 61 is extracted, a pressure difference occurs, and the pressure valve 63 is open by itself, then cold water in the reservoir 62 enters the water tank 61, meanwhile, fresh water is introduced into the reservoir 62 from tap water.
A temperature sensor 70 is positioned in a lower zone, preferably bottom of the water tank 61 to detect the temperature of whole water within the water tank 61. An electronic board 20 is disposed in the casing and electrically connected with the four three way valves 31, 32, 33, 34, the circulation pump 50, the temperature sensor 70, and components like the compressor and the fan for controlling the operation of the refrigerant circuit and switching working modes of the system 100.
Referring to Fig. 1, the heat pump type water heater 100 can work in a heating mode when the refrigerant circuit is running. In this mode, water within the water tank 61 is extracted via the first outgoing line 41 under the operation of the circulation pump 50. As indicated by arrows in Fig. 1, the four three way valves 31, 32, 33, 34 are controlled by the electronic board 20 to open corresponding ports thereof, thereby leading water flow to sequentially pass through the first, the second, and the third three way valves 31, 32, 33 and enters the water/refrigerant heat exchanger 10 for obtaining heat from the refrigerant, then the heated water passes through the fourth three way valve 34 and returns into the water tank 61 via the first incoming line 42.
The temperature sensor 70 monitors the temperature of water within the water tank 61, and when the temperature value is equal to or larger than a predetermined threshold, like 65°C, the system will be switched from the heating mode to a descaling mode. This is because scale components are more likely to be generated in water at a high temperature, that is, when the water is heated to a high value, scales are more easily built up in the water/refrigerant heat exchanger 10 and degrade the heat exchanging performance. Therefore, in descaling mode, cold water can be introduced into the water/refrigerant heat exchanger 10 to avoid the formation of the scales therein, and in the meantime, the water flow can remove existing scales.
Referring to Fig. 2, when the heat pump type water heater 100 is work in the descaling mode, the refrigerant circuit does not work anymore. In this mode, cold water within the cold water reservoir 62 is extracted via the second outgoing line 43 under the operation of the circulation pump 50. As indicated by arrows in Fig. 2, the four three way valves 31, 32, 33, 34 are controlled by the electronic board 20 to open corresponding ports thereof, thereby leading water flow to sequentially pass through the first, the second, and the fourth three way valves 31, 32, 34, and enters the water/refrigerant heat exchanger 10 for removing scales therein, then the cold water passes through the third three way valve 33 and returns into the cold water reservoir 62 via the second incoming line 44. In a preferred embodiment, the circulation pump 50 can work at a maximum output at the descaling mode. On one hand, high rates of water flow is positive to the scale removal, and on the other hand, at the time the system being switched from the heating mode to the descaling mode, the water/refrigerant heat exchanger 10 is still hot, therefore, water flow fast passing through the water/refrigerant heat exchanger 10 can avoid temperature increasing of cold water returning to the cold water reservoir 62.
The volume of the cold water reservoir 62 (Vreservoir) is generally equal to the sum of the volumes (Vtotal) of the water/refrigerant heat exchanger 10, the circulation pump 50, and water pipes connected in the divert valve combinations and between the divert valve combinations and the water/refrigerant heat exchanger 10. Nevertheless, it could happen that the system works with water having high hardness and more scales can be built up. In this case, an extra volume of cold water is needed to assure the scale removal. Accordingly, Vreservoir can be larger than Vtotal in regions where tap water has a very high hardness.
As a result, the system can work in the descaling mode that cold water from the cold water reservoir in addition to the water tank passes through the water/refrigerant heat exchanger when the refrigerant circuit is not working for avoidance of formation of scales and/or removing scales existing in the water/refrigerant heat exchanger.
It would be apparent to those skilled in the art that, the cold water reservoir can be separated from the water tank and in such case the water tank is supplied water directly from tap water. In addition, the divert valve combinations may employ more or less divert valves including not only three way valves but also four way valves.
It is to be understood, however, that even though numerous, characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosed is illustrative only, and changes may be made in detail, especially in matters of number, shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broadest general meaning of the terms in which the appended claims are expressed.

Claims

A heat pump type water heater system (100) comprising:
a refrigerant circuit having a water/refrigerant heat exchanger (10) for condensing a refrigerant to release heat from the refrigerant to water passing through the water/refrigerant heat exchanger;

a water tank (61) that stores water capable of passing through the water/refrigerant heat exchanger to obtain heat from the refrigerant when the refrigerant circuit is working; comprising

a cold water reservoir (62) that stores cold water capable of passing through the water/refrigerant heat exchanger when the refrigerant circuit is not working;

a divert valve combinations connected with the water/refrigerant heat exchanger (10), a circulation pump (50) connected with the divert valve combinations, a first incoming line (42) and a first outgoing line (41) connected between the divert valve combinations and the water tank (61), and a second incoming line (44) and a second outgoing line (43) connected between the divert valve combinations and the cold water reservoir (62); and

being configured to operate the divert valve combinations and the circulation pump (50) to work in a heating mode that water within the water tank (61) passes through the water/refrigerant heat exchanger to obtain heat when the refrigerant circuit is working, and characterized in that the heat pump type water heater system is further configured to operate the divert valve combinations and the circulation pump (50) to work in a descaling mode that cold water within the cold water reservoir (62) passes through the water/refrigerant heat exchanger to remove scales formed in the water/refrigerant heat exchanger when the refrigerant circuit is not working.
A heat pump type water heater system according to claim 1, wherein the divert valve combinations comprises a first three way valve (31), a second three way valve (32), and a third three way valve (33) sequentially connected, and a fourth three way valve (34); wherein the third three way valve and the fourth three way valve are connected to the water/refrigerant heat exchanger respectively.
A heat pump type water heater system according to claim 2, wherein the first outgoing line (41) is connected to one port of the first three way valve (31), and the second outgoing line (43) is connected to another port of the first three way valve (31); wherein the first incoming line (42) is connected to one port of the fourth three way valve (34), and the second incoming line (44) is connected to one port of the third three way valve (33).
A heat pump type water heater system according to claims 2 or 3, wherein when the system is working in the heating mode, water within the water tank (61) is extracted via the first outgoing line (41) and sequentially passes through the first, the second, and the third three way valves (31, 32, 33), and enters the water/refrigerant heat exchanger (10) for obtaining heat, then the heated water passes through the fourth three way valve (34) and returns into the water tank (61) via the first incoming line (42); wherein when the system is working in the descaling mode, cold water within the cold water reservoir (62) is extracted via the second outgoing line (43) and sequentially passes through the first, the second, and the fourth three way valves (31, 32, 34), and enters the water/refrigerant heat exchanger (10) for removing scales therein, then the cold water passes through the third three way valve (33) and returns into the cold water reservoir (62) via the second incoming line (44).
A heat pump type water heater system according to claims 1, further comprising a temperature sensor (70) positioned in a lower zone of the water tank (61).
A heat pump type water heater system according to claims 1, wherein the volume of the cold water reservoir (62) is equal to or larger than the sum of the volumes of the water/refrigerant heat exchanger (10), the circulation pump (50), and water pipes connected in the divert valve combinations and between the divert valve combinations and the water/refrigerant heat exchanger.
A heat pump type water heater system according to claims 1, wherein the water tank (61) and the cold water reservoir (62) are disposed in a same water container (60), and the cold water reservoir locates below and is usually isolated with the water tank; wherein a pressure valve (63) is disposed between the water tank (61) and the cold water reservoir (62) to automatically open a water path therebetween when water within the water tank is extracted for sanitary usages.
A heat pump type water heater system according to claims 1, wherein the temperature of cold water within the cold water reservoir (62) is generally much smaller than that of water within the water tank (61).