US20240230116A1

US20240230116A1 - Dual function water heater and air-conditioning unit

Info

Publication number: US20240230116A1
Application number: US18/292,005
Authority: US
Inventors: Gordon MCRAE
Original assignee: Vaviri Pty Ltd
Current assignee: Vaviri Pty Ltd
Priority date: 2021-07-23
Filing date: 2022-07-22
Publication date: 2024-07-11
Also published as: WO2023004443A1; CN118019947A; AU2022314083A1; EP4374113A1

Abstract

A dual function water heater and air-conditioning unit including air-conditioner and water heater subassemblies. In the operational cycle illustrated, the unit heats the water in a geyser and operates an air-conditioner in cooling mode. The geyser heat exchanger acts as a condenser in which the refrigerant transitions from a vapor phase to a liquid phase. The liquid refrigerant is conveyed to an interior unit expansion valve where the liquid refrigerant is flash evaporated and conveyed to the interior unit heat exchanger operating as an evaporator, in which adiabatic cooling of the refrigerant causes extraction of heat from air flowing over the interior unit heat exchanger tubes. The extracted heat is transferred to the refrigerant, causing evaporation of the liquid refrigerant to a gaseous refrigerant, which is directed, from the internal unit heat exchanger to the compressor, for repetition of the cycle.

Description

FIELD

This invention relates to a dual function water heater and air-conditioning unit.

BACKGROUND

The dual function unit of the invention is essentially a “heat harvesting” system that “harvests” heat from either or both the ambient environment, the warm air output of an air-conditioner and a water heater (typically a domestic-type water heater used for purposes of heating water for bathing, showering or dishwashing, in South Africa commonly referred to as a “geyser”.

SUMMARY OF THE INVENTION

Summary

According to the invention a dual function water heater and air-conditioning unit comprises an air-conditioner subassembly and a water heater subassembly interconnected for circulation of a refrigerant within a fluidic circuit configured as a vapor compression refrigeration circuit:

- the air-conditioner subassembly comprising an interior air-conditioning unit configured for installation within a building and an exterior air-conditioning unit configured for installation outside the building;
- the interior air-conditioning unit including a first heat exchanger interconnected in-circuit in the refrigeration circuit;
- the exterior air-conditioning unit including a second heat exchanger interconnected in-circuit in the refrigeration circuit;
- the water heater subassembly including a water tank and a third heat exchanger interconnected in-circuit in the refrigeration circuit and configured for location within the water tank;
- the first and second heat exchangers each including outlet tubes and first and second inlet tubes in-circuit in the refrigeration circuit;
- the third heat exchanger including inlet and outlet tubes in-circuit in the refrigeration circuit;
- the first refrigerant inlet tube of each of the first and second heat exchangers having an expansion valve installed in the refrigeration circuit upstream of the heat exchanger;
- the second refrigerant inlet tube of each heat exchanger having no expansion valve;
- the refrigeration circuit including a plurality of control valves settable to direct the refrigerant within the refrigeration circuit;
- the control valves being settable such that:
  - at least one of the first or second heat exchangers is configured to operate as an evaporator, in which setting of the control valves, refrigerant is introduced into the heat exchanger through the expansion valve installed in the first inlet tube of that heat exchanger;
- at least one of the first or second heat exchangers may be configured to operate as a condenser, in which setting of the control valves, refrigerant is introduced into the heat exchanger through the second inlet tube of that heat exchanger; and
- the third heat exchanger may be configured to operate as a water heater within the water tank, in which setting of the control valves, the third heat exchanger is configured to operate as a condenser.

The control valves are preferably settable such that the dual function water heater and air-conditioning unit is configured to operate in one of a plurality of modes of operation selected from:

- a first mode of operation—water heating only;
- a second mode of operation—water heating and air conditioner cooling;
- a third mode of operation—air-conditioning cooling only; and
- a fourth mode of operation—air-conditioning heating only.

In this form of the invention, in the first mode of operation—water heating only—the control valves are set such that;

- the first heat exchanger is switched out of the refrigeration circuit and no refrigerant is supplied to the first heat exchanger;
- the third heat exchanger is configured to operate as a condenser, in which setting of the control valves, refrigerant is introduced from the compressor into the third heat exchanger by way of the third heat exchanger inlet tube; and
- the second heat exchanger is configured to operate as an evaporator, in which setting of the control valves, refrigerant is supplied to the second heat exchanger from the third heat exchanger outlet tube through the first inlet tube of the second heat exchanger, by way of the expansion valve of the second heat exchanger.

In this form of the invention, in the second mode of operation—water heating and air conditioner cooling—the control valves are set such that;

- the second heat exchanger is switched out of the refrigeration circuit and no refrigerant is supplied to the second heat exchanger;
- the third heat exchanger is configured to operate as a condenser, in which setting of the control valves, refrigerant is introduced from the compressor into the third heat exchanger by way of the third heat exchanger inlet tube; and
- the first heat exchanger is configured to operate as an evaporator, in which setting of the control valves, refrigerant is supplied to the first heat exchanger from the third heat exchanger outlet tube through the first inlet tube of the first heat exchanger, by way of the expansion valve of the first heat exchanger.

In this form of the invention, in the third mode of operation—air-conditioning cooling only—the control valves are set such that;

- the third heat exchanger is switched out of the refrigeration circuit and no refrigerant is supplied to the third heat exchanger;
- the second heat exchanger is configured to operate as a condenser, in which setting of the control valves, refrigerant is introduced from the compressor into the second heat exchanger by way of the second inlet tube of the second heat exchanger; and
- the first heat exchanger is configured to operate as an evaporator, in which setting of the control valves, refrigerant is supplied to the first heat exchanger from the second heat exchanger outlet tube through the first inlet tube of the first heat exchanger, by way of the expansion valve of the first heat exchanger.

In this form of the invention, in the fourth mode of operation—air-conditioning heating only—the control valves are set such that;

- the third heat exchanger is switched out of the refrigeration circuit and no refrigerant is supplied to the third heat exchanger;
- the first heat exchanger is configured to operate as a condenser, in which setting of the control valves, refrigerant is introduced from the compressor into the first heat exchanger by way of the second inlet tube of the first heat exchanger; and
- the second heat exchanger is configured to operate as an evaporator, in which setting of the control valves, refrigerant is supplied to the second heat exchanger from the second heat exchanger outlet tube through the first inlet tube of the second heat exchanger, by way of the expansion valve of the second heat exchanger.

The water tank heater may conveniently be the water tank of a water heater or geyser, which could be a horizontal or a vertical geyser.
In this embodiment of the invention, the third heat exchanger (the water heater heat exchanger) may be configured as a direct-heating immersion heating element comprising a finned tube heat exchanger that may be installed within the interior of the geyser for direct heat transfer from the heat exchanger to the water within the geyser.
In this embodiment of the invention, further, the third heat exchanger (the water heater heat exchanger) may be configured to conform in shape, size, general form factor and physical connection equipment to current standardized electric water heater elements, such that the water heater heat exchanger may be retrofitted into a conventional electric geyser in place of the conventional electrical element.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described with reference to the accompanying drawings in which:

FIGS. 1 to 4 are simplified circuit diagrams (in block diagram form) of the components of the dual function unit of the invention illustrating the unit switched, in each case, to one of four modes of operation—each Figure illustrates only the refrigeration circuit circuitry relevant to that mode of operation:

FIG. 1 illustrates the unit switched to a first mode or cycle of operation: CYCLE 1—WATER HEATING ONLY;

FIG. 2 illustrates the unit switched to a second mode or cycle of operation: CYCLE 2—WATER HEATING AND AIR CONDITIONER COOLING;

FIG. 3 illustrates the unit switched to a third mode or cycle of operation: CYCLE 3 AIR-CONDITIONING COOLING ONLY;

FIG. 4 illustrates the unit switched to a fourth mode or cycle of operation: CYCLE 4—AIR-CONDITIONING HEATING ONLY;

FIG. 5 is a diagrammatic illustration of a conventional horizontal domestic water heater or geyser illustrating fitment of the water heating heat exchanger of the invention to such a conventional horizontal geyser;

FIG. 6 is a diagrammatic illustration of a conventional vertical domestic water heater or geyser illustrating fitment of a pair of water heating heat exchangers according to the invention to such a conventional vertical geyser;

FIG. 7 is a diagrammatic isometric view of one embodiment of a finned tube water heating heat exchanger according to the invention;

FIG. 8 is a diagrammatic side elevation of the finned tube water heating heat exchanger of FIG. 7 ;

FIG. 9 is a diagrammatic side elevation of a further embodiment of a finned tube water heating heat exchanger according to the invention;

FIG. 10 is a diagrammatic end elevation of the geyser mounting plate of the heat exchanger of FIG. 9 ;

FIG. 11 is a diagrammatic sectional elevation on a line 11-11 in FIG. 9 ;

FIG. 12 is a diagrammatic side elevation of a punched fin for the heat exchangers of FIGS. 7 and 9 ; and

FIG. 13 is a diagrammatic part-section side elevation on the heat exchanger tube arrangement (FIGS. 7 and 9 ), illustrating the arrangement of the heat exchanger tubes and punched fins.

DETAILED DESCRIPTION

Vapor-compression refrigeration, in which a refrigerant is circulated through a refrigeration circuit, is widely used in air-conditioning and refrigeration as well as in heat pumps. The refrigerant used depends on the application, but in each case, the refrigerant is a working fluid that undergoes successive first-order phase transitions during the refrigeration cycle. First-order phase transitions are substantially constant temperature processes in which large amounts of energy are absorbed or released as latent heat while the temperature remains substantially constant. These systems exploit the enthalpy of vaporization to add heat to a medium to be conditioned, such as air in an air-conditioning system or water in a water heater heat pump and, in the reverse, the enthalpy of condensation to extract heat from the medium.
It is appreciated that heat transfer is an additive process—heat always transfers additively to a cooler medium from a warmer medium, even during cooling processes. This notwithstanding, cooling processes will sometimes be referred to in this specification using terminology such as heat “extraction” or “absorption”. This is done for ease of reference.
Vapor-compression refrigeration requires four basic components: a compressor, a condenser, a thermal expansion valve and an evaporator.
Circulating refrigerant exiting the evaporator enters the compressor in gaseous state where the refrigerant is compressed and simultaneously heated adiabatically by compression.
The superheated gas then passes through the condenser in which the gaseous refrigerant phase transitions from a gas through vapor to a liquid phase. The process of condensation expedites the release of large quantities of latent heat, which is transferred to an external, heat extracting medium. In some systems, a water heater heat pump for example, the heat extracting medium is the water to be heated and the latent heat is transferred, by the heat exchanger to heat up the water in the water heater. However, in some systems, such as in most air-conditioning systems, the heat-extracting medium is a vented airflow that is simply discharged to atmosphere. It will be appreciated that this constitutes an egregious waste of energy.
The condensed liquid refrigerant is next routed through an expansion valve where the liquid undergoes an abrupt reduction in pressure, resulting in adiabatic flash evaporation of the refrigerant and adiabatic cooling that creates an auto-refrigeration effect.
The cold (refrigerated) refrigerant liquid and vapor mixture are then routed through the evaporator in which heat must be extracted from (or rather contributed by) the surrounding medium to replace the latent heat of condensation lost in the process of evaporation. Heat is transferred to the refrigerant which causes continuing evaporation of the liquid refrigerant, returning it to a gaseous state. In air-conditioning systems, the surrounding medium is air that is to be cooled prior to the cooled air being vented into a space or room to be cooled. However, in some systems, such as a water heater heat pump for example, the heat-contributing surrounding medium is a vented airflow that is simply discharged to waste (typically to atmosphere) as wasted cooled air, once again constituting a waste of energy.
To complete the refrigeration cycle, the refrigerant gas from the evaporator is routed back in the compressor to repeat the cycle.
The dual function water heater and air-conditioning unit 10 of the invention is illustrated in the drawings. The unit 10 comprises a water heater subassembly 12 interconnected with an air-conditioner subassembly 14.
The air-conditioner subassembly 14 is similar in many respects to a split system air conditioner system in that it comprises an interior air-conditioner unit 14.1 configured for installation within a building (not shown) and an exterior air-conditioner unit 14.2 configured for installation externally of the building.
First and second interconnected finned coil tube heat exchangers 16, 18 are installed within the interior (14.1) and exterior (14.2) air-conditioning units, respectively. The first heat exchanger 16 (this is the first heat exchanger mentioned in the Claims and the Summary of the Invention) is located in the interior air-conditioner unit 14.1 and the second heat exchanger 18 (this is the second heat exchanger mentioned in the Claims and the Summary of the invention) is located in the exterior air-conditioner unit 14.2.
The water heater subassembly 12 includes a conventional horizontal tank water heater or geyser 20.
FIGS. 1 to 4 illustrate (diagrammatically) a water heater subassembly 12 incorporating a horizontal geyser 20.
The dual function water heater and air-conditioning unit 10 can be used in conjunction with vertical geysers. A vertical geyser 120 configured for integration with the dual function unit 10 is illustrated in and described with reference to FIG. 6 .
In both cases, the water heater subassembly 12 makes use of a water heater heat exchanger 22 (this is the third heat exchanger mentioned in the Claims and the Summary of the invention) that, in the preferred form of the invention is a finned tube heat exchanger.
The finned tube heat exchanger 22 is a direct-heating immersion heater that is installed within the interior of the geyser 20, for immersion within the water in the geyser 20 and for direct heat transfer from the heat exchanger 22 to the water in the geyser 20.
The water heater heat exchanger 22 is preferably standardized to conform, in shape, size, general form factor and physical connection equipment, to current, standardized electric water heater elements. In this regard, the replaceable components, particularly electric water heater elements, of existing electric water heaters have been largely standardized. In the case of electric heater elements, the elements have been standardized to conform to small range of standard sizes, form factors and physical and electrical connections. This is to facilitate easy replacement of the elements as replaceable components. Standardization of the water heater heat exchanger 22 to conform to the shape, size and form factor of electric water heater elements, enables retrofitting of the water heater heat exchanger 22 into conventional electric geysers in the place of the electrical element of such a conventional electric geyser.
The interior air-conditioner unit 14.1 can be configured similarly to the shape and configuration of the interior unit of a currently available split system air conditioner. Users of the interior air-conditioner unit 14.1 should be immediately familiar with the operation of the unit 14.1, which includes an exterior housing, a manually variable speed fan located within air-conditioner ducting within the housing (not shown). The fan is configured to direct ambient air (typically from a source outside of the building space served by the interior air-conditioner unit 14.1) over the finned tube heat exchanger coil of the interior unit heat exchanger 16 and, through a variable direction grille into the building space served by the interior air-conditioner unit 14.1. The operating controls of the interior unit 14.1 are relatively conventional and similar to existing split system air-conditioner interior units and, as will be seen below, the interior unit 14.1 can operate as an air-conditioner in heating or cooling mode.
The exterior air-conditioner unit 14.2, like a conventional split system air-conditioner, is configured for installation externally of the building served by the interior air-conditioner unit 14.1 and, like the interior air-conditioner unit 14.1, can be configured similarly to the shape and configuration of the exterior unit of a currently available split system air conditioner. The exterior air-conditioner unit 14.2 includes an exterior housing, and an automatically variable stepped speed fan located within air-conditioner ducting within the housing (not shown). The fan draws ambient air from the outside of the building, over the finned tube heat exchanger coil of the exterior unit heat exchanger 18, from where the air is simply vented to atmosphere.
The dual function water heater and air conditioning unit 10 includes an integrated refrigerant fluid flow circuit within which at least the 4 variations of the refrigeration cycle described below can be operated. The various components of the refrigeration circuit will be described with reference to the drawings in what follows.
As indicated above, FIGS. 1 to 4 are simplified circuit diagrams (in block diagram form) of the components of the dual function water heater and air conditioner unit 10.
FIGS. 1 to 4 are simplified circuit-and block diagrams illustrating the components and operation of the dual function unit 10. Each of FIGS. 1 to 4 illustrates one of four modes of operation and in each case, each Figure illustrates only the refrigeration circuit circuitry relevant to that mode of operation. Having regard to FIGS. 1 to 4 , the refrigeration circuit circuitry includes, in addition to the componentry already described:

- housed within the exterior air-conditioner unit 14.2 housing:
  - a compressor 30;
  - control valves that are settable to direct the refrigerant within the refrigeration circuit, including a plurality of check valves 32, a first diverting manifold 34 and a second diverting manifold 36;
  - an exterior unit expansion valve 38; and
  - a suction diverting manifold 40;
- housed within the interior air-conditioner unit 14.1 housing:
  - an interior unit expansion valve 42; and
- extending between the various components described above, interconnecting fluid lines that interconnect the components described above hydraulically/pneumatically to complete the refrigeration circuit—the various fluid lines are described in more detail with reference to each mode of operation of the dual function water heater and air conditioner unit 10.

The dual function water heater and air-conditioning unit 10 further includes a liquid accumulator 24 and a sight glass 26, the liquid accumulator being installed to receive the liquid feed from any one of the three heat exchangers 16, 18, 22 to ensure storage of sufficient liquid to feed the expansion valves 38, 42 in the exterior air-conditioner unit 14.2 and interior air-conditioner unit 14.1.

Cycle 1—Water Heating Only

In FIG. 1 the dual function water heater and air conditioning unit 10 is switched to a first mode or cycle: CYCLE 1—WATER HEATING ONLY.
The refrigeration circuit required for CYCLE 1—WATER HEATING ONLY operation, as illustrated in FIG. 1 , includes a number of components already described, including the water heater subassembly 12 and the components thereof as well as the exterior air-conditioner unit 14.2 and the components thereof.
In CYCLE 1 mode, circulating refrigerant enters the compressor 30 by means of a suction line 44 and exits the compressor 30 as a superheated refrigerant gas by means of a hot gas line 46 that directs the refrigerant to the first and second diverting manifolds 34, 36, which switches the fluid flow to a hot gas line 48 that directs the superheated refrigerant gas to an inlet 50 of the water heater heat exchanger 22.
Switched to this configuration, the water heater heat exchanger 22 acts as a condenser in which the gaseous refrigerant phase transitions from a gaseous phase to a liquid phase. Besides being superheated by compression, the condensation process expedites the release of large quantities of latent heat, which the finned tube water heater heat exchanger 22 transfers directly to the water in the geyser 20.
The refrigerant, now condensed to its liquid phase, exits the heat exchanger 22 by means of a heat exchanger outlet 52. A fluid line 54 conveys the refrigerant to a check valve 32.1 which directs the refrigerant to a liquid accumulator 24 and sight glass 26. The liquid refrigerant is conveyed by a liquid line 56 to the exterior unit expansion valve 38 where the liquid refrigerant is flash evaporated and conveyed to the exterior unit heat exchanger 18.
Switched to this configuration, the exterior unit heat exchanger 18 functions as an evaporator in which adiabatic cooling is used to effectively absorb heat from exterior atmosphere.
Having been through the evaporator constituted by the exterior unit heat exchanger 18, the refrigerant exits the external unit heat exchanger 18 as a cool, gas phase refrigerant by way of a suction line 58 that is directed by a second diverting manifold 36 and check valve 32.2 to the suction diverting manifold 40, from where the refrigerant is recirculated to the compressor 30 for repetition of the refrigerant cycle.

Cycle 2—Water Heating and Air Conditioner Cooling

In CYCLE 2 mode, as illustrated in FIG. 2 , the dual function water heater and air-conditioner unit 10 is switched to a second mode or cycle in which the unit 10 is used to heat the water in the geyser 20 and to operate the interior air-conditioner unit 14.1 as an air-conditioner unit in cooling mode.
In CYCLE 2 mode, the refrigerant enters the compressor 30 by means of the suction line 44 and exits the compressor by means of the hot gas line 46 that directs the superheated refrigerant gas to the first and second diverting manifolds 34, 36.
Similarly to CYCLE 1, the water heater heat exchanger 22 acts as a condenser in which the gaseous refrigerant phase transitions from a vapor phase to a liquid phase. In the transition, the latent heat of condensation is transferred, by the finned tube water heater heat exchanger 22 directly to the water in the geyser 20.
The condensed liquid refrigerant exits the heat exchanger 22 by means of the heat exchanger outlet 52, from where the liquid line 54 conveys the liquid refrigerant to the check valve 32.1 which directs the refrigerant to the liquid accumulator 24 and sight glass 26. The liquid refrigerant is conveyed by a liquid line 60 to the interior unit expansion valve 42 where the liquid refrigerant is flash evaporated and conveyed, by means of a line 62, to the interior unit heat exchanger 16.
The interior unit heat exchanger 16 operates as an evaporator within which adiabatic flash evaporation of the refrigerant and adiabatic cooling of the vaporizing refrigerant creates an auto-refrigeration effect.
In the evaporator constituted by the interior unit heat exchanger 16, the cold (refrigerated) refrigerant liquid and vapor mixture are routed through the evaporator in which heat is extracted from (or rather contributed by) the surrounding medium (the ambient air flowing over the heat exchanger tubes) to replace the latent heat of condensation lost in the process of evaporation. Heat is transferred to the refrigerant which causes continuing evaporation of the liquid refrigerant, returning it to a gaseous state.
Having been through the evaporator constituted by the interior exterior unit heat exchanger 16, the refrigerant exits the internal unit heat exchanger 16 as a cool, gas phase refrigerant by way of a suction line 64 that is directed by the first diverting manifold 34 and check valve 32.3 to the suction diverting manifold 40, from where the refrigerant is recirculated to the compressor 30 by way of the suction line 44 for repetition of the refrigerant cycle.

Cycle 3—Air-Conditioning Cooling Only

In CYCLE 3 mode, as illustrated in FIG. 3 , the dual function water heater and air-conditioner unit 10 is switched simply to operate the interior air-conditioner unit 14.1 as an air-conditioner unit in cooling mode.
In this mode, the circulating refrigerant enters the compressor 30 by means of the suction line 44 and exits the compressor as a superheated refrigerant gas by means of the hot gas line 46 that directs the superheated refrigerant gas to the first and second diverting manifolds 34, 36.
The diverting manifolds 34, 36 switch the fluid flow to a hot gas line 66 that directs the superheated refrigerant gas to a secondary inlet 68 of the exterior unit heat exchanger 18, bypassing the exterior unit expansion valve 38. The exterior unit heat exchanger 18 acts as a condenser in which the hot gaseous refrigerant phase transitions from a vapor phase to a hot liquid phase. In the transition, the latent heat of condensation is dumped as excess heat to the exterior atmosphere.
From the exterior unit heat exchanger 18, the hot liquid phase refrigerant is conveyed to a check valve 32.4 which directs the refrigerant to the liquid accumulator 24 and sight glass 26 by means of a liquid line 70. The liquid refrigerant is conveyed by fluid line 60 to the interior unit expansion valve 42 where the liquid refrigerant is flash evaporated and conveyed, by means of the fluid line 62, to the interior unit heat exchanger 16.
As in CYCLE 2, the interior unit heat exchanger 16 and the interior unit 14.1 operate as an air-conditioner in cooling mode.
From the interior unit heat exchanger 16, the refrigerant is directed, by way of the suction line 64 that is directed by the first diverting manifold 34 and check valve 32.3, to the suction diverting manifold 40, from where the refrigerant is recirculated to the compressor 30 by way of the suction line 44 for repetition of the refrigerant cycle.

Cycle 4—Air-Conditioning Heating Only

In this mode of operation, circulating refrigerant enters the compressor 30 by means of the suction line 44 and exits the compressor 30 as a superheated refrigerant gas by means of the hot gas line 46 that directs the refrigerant gas to the diverting manifold 34.
The diverting manifold 34 switches the fluid flow to a hot gas line 72 that directs the superheated refrigerant gas to the inlet 76 of the interior unit heat exchanger 16, bypassing the interior unit expansion valve 42.
In this mode, the interior unit heat exchanger 16 acts as a condenser in which the hot gaseous refrigerant phase transitions from a vapor phase to a hot liquid phase in which the latent heat of condensation must be transferred to an external medium, which is provided by inflowing cold air.
In the interior unit 14.1, the manually variable speed fan is operated to direct cold air from the building space served by the interior air-conditioner unit 14.1 over the finned tube heat exchanger coil of the interior unit heat exchanger 16 and into the building space served by the interior air-conditioner unit 14.1. The heat exchanger tubes, heated by the latent heat of condensation of the refrigerant transitioning from gas to liquid, transfers refrigerant heat to the inflowing air to heat the building space served by the unit 14.1. In this mode (CYCLE 4), therefore, the interior unit 14.1 operates as an air-conditioner in heating mode.
From the interior unit heat exchanger 16, the liquid phase refrigerant is conveyed to a check valve 32.5 which directs the refrigerant to the liquid accumulator 24 and sight glass 26 by means of a liquid line 74. The refrigerant is conveyed by the liquid line 56 to the exterior unit expansion valve 38 where the liquid refrigerant is flash evaporated and conveyed to the exterior unit heat exchanger 18.
The exterior unit heat exchanger 18 functions as an evaporator in which adiabatic cooling is used to effectively absorb heat from exterior atmosphere. The refrigerant exits the external unit heat exchanger 18 as a cool, gas phase refrigerant by way of the suction line 58 that is directed by the second diverting manifold 36 and check valve 32.2 to the suction diverting manifold 40, from where the refrigerant is recirculated to the compressor 30 for repetition of the refrigerant cycle.

Water Heater Heat Exchanger

The invention includes a finned tube heat exchanger 22 that can be installed within the geyser tank 20.1 in the place of the electric water heater element conventionally used in a geyser such as this. The heat exchanger 22 is standardized to conform, in shape, size, general form factor and physical connection equipment, to current, standardized electric water heater elements. This allows replacement of the conventional electric element by the heat exchanger 22 of the invention by means of a simple retrofit. The electric element is removed and the heat exchanger 22 is simply connected in its place.
The conventional geyser 20, with the heat exchanger 22 installed therein can now be integrated with the dual function unit 10 described with reference to FIGS. 1 to 4 by connecting the heat exchanger 22 hydraulically/pneumatically into the refrigeration circuit described with reference to FIGS. 1 to 4 above, instead of connecting the geyser 20 into an electricity supply system.
In water heating mode (CYCLES 1 and 2), superheated refrigerant gas is supplied to the inlet 50 of the water heater heat exchanger 22. The water heater heat exchanger 22 acts as a condenser in which the gaseous refrigerant phase transitions from a vapor phase to a liquid phase, in the process releasing a large quantity of latent heat which the finned tube water heater heat exchanger 22 transfers directly to the water in the geyser 20. The refrigerant, condensed to a liquid phase, exits the heat exchanger 22 by means of the heat exchanger outlet 52 and recirculates to the refrigeration circuit.
The heat exchanger 22 is located in essentially the same location as the replaced electric element and the heat exchanger 22 is mounted to the geyser 20 using the connectors (other than electrical connectors) and the fastenings typically used for installation of the electric water heater element it replaces.
The finned tube portion 22.1 of the heat exchanger 22 is a direct-heating immersion heater that is similar in size and shape to the electric element replaced by the heat exchanger 22. The finned tube portion 22.1 of the heat exchanger 22 is installed within the interior of the geyser water tank 20.1 for immersion within the water in the tank 20.1 and for direct heat transfer from the heat exchanger 22 to the water in the tank 20.1 during the water heating cycles (CYCLES 1 and 2) described above.
To mount the heat exchanger 22 to a geyser 20, the heat exchanger 22 is provided with a mounting plate 22.2 standardized to conform to the shape, size and form factor of the mounting plates of electric elements replaced by the heat exchanger 22.
As can be seen from FIGS. 7 and 8 , the heat exchanger 22 is a finned tube heat exchanger in which the fins are constituted by a stack of evenly-spaced metal fin plates 22.9 secured to metal refrigerant tubes 22.6. The tubes 22.6 are interconnected in a tortuous path coil arrangement secured within header blocks 22.7, 22.8 which serve to interconnect the tubes 22.6 hydraulically/pneumatically to permit refrigerant to flow through the tubes 22.6 from the heat exchanger inlet tube 50 to the heat exchanger outlet tube 52.
FIGS. 9 to 13 illustrate a second embodiment of the heat exchanger 22. In these drawings, similar items are numbered with numbers corresponding to those used in FIGS. 7 and 8 , incremented by 100.
The embodiment of the heat exchanger 122 illustrated in FIGS. 9 to 11 is also a finned tube heat exchanger in which the fins are constituted by a stack of evenly-spaced metal fin plates 122.9 secured to metal refrigerant tubes 122.6. The tubes 122.6 are interconnected in a tortuous path coil arrangement in which the tubes 122.6, at the one end (the upper end in FIG. 9 ) are bent into a U-shape. At their other ends, the U-shaped tubes 122.6 are interconnected by means of short U-tubes 122.10 that are soldered onto the open ends of the U-shaped tubes 122.6. This serves to interconnect the tubes 122.6 hydraulically/pneumatically to permit refrigerant to flow through the tubes 122.6 from the heat exchanger inlet tube 150 to the heat exchanger outlet tube 152.
To mount the heat exchanger 122 to a geyser 20, the heat exchanger 122 is provided with a mounting plate 122.2 standardized to conform to the shape, size and form factor of the mounting plates of electric elements replaced by the heat exchanger 122. This drawing illustrates the mounting holes 122.13 by means of which the mounting plate 122.2 is mounted to the geyser 120.
In this embodiment, the heat exchanger 122 includes an electric heater element 22.11 in addition to the heat exchanger tubes 122.6. In cold climate environments, it is possible that the external ambient air temperature becomes so cold that the unit 10 will most likely fail to heat the water in the geyser 20 sufficiently. In these environments, the electric heater element 22.11 can be switched in-circuit to assist in heating the water in the geyser 20 to the desired pressure under control of the geyser thermostat. In the most basic implementation of this embodiment of the invention, the electric heater element 22.11 could simply be wired to the premises main electricity distribution board, where a circuit breaker or switch could be used to switch the electric water heater element in or out of circuit manually. Alternatively, the unit 10 could be supplied with an ambient air temperature sensor and the unit programmable logic could be programmed to switch the electric heater element 22.11 in-circuit to assist with water heating when the air temperature sensor registers an ambient air temperature below a predetermined temperature, which could be anything between −15° C. and −5° C. and preferably −10° C.
The heat exchanger 122 also includes a protector tube 122.12 that is secured to the heat exchanger mounting plate 122.2 by welding or the like. The protector tube extends about the outside of the tube and fin array of the heat exchanger 122 and serves to protect the tubes 122.6 and fins 122.9 against damage during transport, handling and installation.
In both embodiments of the heat exchanger 22 (FIGS. 7 and 8 ; FIGS. 9 to 11 ), the tubes 22.6, 122.6 and fin plates 22.9, 122.9 are preferably fabricated from copper, the thermal conductivity of which is well matched to the working fluids used in the refrigeration circuit and the water in the geyser 20, 120.
As can be seen from FIGS. 12 and 13 , the fin plates (numbered 22.9 for ease of reference) are made from thin copper plates 22.9.1. Tube mounting holes 22.9.2 are formed in the plate 22.9.1 to accommodate the refrigerant tubes 22.6, 122.6. The tube mounting holes 22.9.2 are formed by press-forming, cutting and flaring, to create a flared collar extending from the surface of the plate 22.9.1, the collar including a sleeve portion 22.9.3 and a flared abutment portion 22.9.4. The sleeve 22.9.3 serves as a spacer between adjacent fin plates 22.9 and the tube mounting hole 22.9.2 and the sleeve 22.9.3 are dimensioned to be a tight fit about the external surface of the surface of the refrigerant tube 22.6, 122.6 to facilitate conductive heat transfer between the tube and fin plate. The flared collar abutment 22.9.4 serves as a stop formation between adjacent fin plates 22.9. Horizontal geyser (typical—South Africa)
The geyser 20 illustrated in the diagrams of FIGS. 1 to 4 is essentially a conventional horizontal water heater or geyser, which is illustrated in more detail (but still diagrammatically) in FIG. 5 . The geyser 20 includes a thermally insulated water tank 20.1 that has a cold water inlet pipe 20.2 and a hot water outlet pipe 20.3, suitably configured for connection of the geyser 20 into domestic or other plumbing.
A finned tube heat exchanger 22 according to the invention is installed within the geyser tank 20.1 in the place of the electric water heater element conventionally used in a geyser such as this—a conventional horizontal geyser. The heat exchanger 22 is standardized to conform, in shape, size, general form factor and physical connection equipment, to current, standardized electric water heater elements. This allows replacement of the conventional electric element by the heat exchanger 22 of the invention by means of a simple retrofit. The electric element is removed and the heat exchanger 22 is simply connected in its place. Like the replaced electric element, the heat exchanger 22 is disposed horizontally within the geyser tank 20.1.
The conventional geyser 20, with the heat exchanger 22 installed therein can now be integrated with the dual function unit 10 described with reference to FIGS. 1 to 4 by connecting the heat exchanger 22 hydraulically/pneumatically into the refrigeration circuit described with reference to FIGS. 1 to 4 above, instead of connecting the geyser 20 into an electricity supply system.
In water heating mode (CYCLES 1 and 2), superheated refrigerant gas is supplied to the inlet 50 of the water heater heat exchanger 22. The water heater heat exchanger 22 acts as a condenser in which the gaseous refrigerant phase transitions from a vapor phase to a liquid phase, in the process releasing a large quantity of latent heat which the finned tube water heater heat exchanger 22 transfers directly to the water in the geyser 20. The refrigerant, condensed to a liquid phase, exits the heat exchanger 22 by means of the heat exchanger outlet 52 and recirculates to the refrigeration circuit.
The heat exchanger 22 is located in essentially the same location as the replaced electric element and the heat exchanger 22 is mounted to the geyser 20 using the connectors (other than electrical connectors) and the fastenings typically used for installation of the electric water heater element it replaces.
The finned tube portion 22.1 of the heat exchanger 22 is a direct-heating immersion heater similar to the electric element replaced by the heat exchanger 22. The finned tube portion 22.1 of the heat exchanger 22 is installed within the interior of the geyser water tank 20.1 for immersion within the water in the tank 20.1 and for direct heat transfer from the heat exchanger 22 to the water in the tank 20.1 during the water heating cycles (CYCLES 1 and 2) described above.

Vertical Geyser (Typical USA, Europe, Australia)

Conventional electric geysers of the vertical type typically use two electric heater elements located within the geyser tank, including a base element located closely adjacent the base of the geyser, where the cold water inlet is also located, and a demand element located relatively high up within the geyser tank, where the hot water outlet is also located. The heater element control circuit switches between the base element and the demand element with the demand element taking precedence. The base element normally carries the major heating load, and the demand element is simply switched in when the water temperature around the demand element drops below a predetermined temperature. The geyser is typically supplied with thermostats and thermostat-driven switches to monitor and control switching in and out of the heating elements.
When the water temperature around the demand element drops below a predetermined temperature, the demand element provides assistance heating to address instantaneous hot water demands on the geyser. In the USA, Europe and Australia, during base element heating only, a typical 200 L vertical geyser will produce an electrical load demand of 4.6 kW, switched between the demand and base element.
FIG. 6 illustrates a conventional vertical geyser 120 in which the electric heating elements have been replaced by heat exchangers 22 according to the invention. The geyser 120 includes a thermally insulated water tank 120.1 that has a cold water inlet pipe 120.2 located adjacent the base of the geyser 120 and a hot water outlet pipe 120.3 located relatively high up within the geyser tank 120.1, both inlets being suitably configured for connection of the geyser 120 into domestic or other plumbing.
The heat exchangers 22 replacing the electric elements are located in the same locations as the electric elements to constitute a base element (the lower heat exchanger 22.3) and a demand element (the upper heat exchanger 22.4).
Such a vertical geyser 120, with the heat exchangers 22 installed therein is integrated with the dual function unit 10 described with reference to FIGS. 1 to 4 by connecting the heat exchangers 22 in-circuit into the refrigeration circuit described with reference to FIGS. 1 to 4 above, instead of connecting the geyser 20 into an electricity supply system.
In the refrigeration circuit, in water heating mode (CYCLES 1 and 2), superheated refrigerant gas flows through the heat exchangers 22 as follows:

- superheated refrigerant gas is supplied to the inlet 150.1 of the demand element 22.4;
- the refrigerant flows through the demand element 22.4, operating as a condenser;
- the refrigerant exits the demand element 22.4 through the demand element outlet 152.1 into a connecting hot gas line 150/152;
- the hot gas line 150/152 conveys the refrigerant from the demand element 22.4 to the base element 22.3;
- the refrigerant is supplied to the inlet 152.2 of the base element 22.3;
- the refrigerant flows through the base element 22.3, operating as a condenser; and
- the refrigerant exits the base element 22.3 through the base element outlet 150.2 back into the refrigeration circuit.

Both heat exchangers 22.3 and 22.4 act as condensers, but the phase transition of the refrigerant from gaseous to liquid phase will adjust automatically to the temperature of the water in the geyser 120.

State 1|Low Demand

In this state:

- the temperature of the water in the geyser 120 is relatively stable at or near the preset hot water temperature;
- the heat demand of the water is relatively low;
- as a result, refrigerant heat discharge from the demand element 22.4 is relatively low; and
- as a further result, there is significant pass-through of hot gaseous refrigerant from the demand element 22.4 to the base element 22.3.

Most of the heating in this state is provided by the base element, in which the bulk of the phase transition of the refrigerant from gaseous to liquid phase occurs and which, as a result, generates the bulk of the latent heat of condensation.
Typical heating load distribution:

- base element>60%; demand element<40%.

STATE 2|High Demand

In the event of high hot water demand, hot water flows from the geyser outlet 120.3 and cold water flows into the geyser inlet 120.2, progressively displacing the hot water in the tank 120.1 with progressively rising cold water.
In the case of a high hot water demand, the inflowing cold water causes the water temperature around the demand element 22.4 to drop progressively lower.
As this happens, the phase transition of the refrigerant in the demand element 22.4 adjusts progressively and automatically in reaction to the changing water temperature. This occurs in the following manner as the refrigerant gas flows through the heat exchangers 22:

- superheated refrigerant gas is supplied to the inlet 150.1 of the demand element 22.4;
- the refrigerant flows through the demand element 22.4, operating as a condenser;
- as the water temperature around the demand element 22.4 reduces progressively, the heat demand of the water increases progressively;
- as a result, refrigerant heat discharge from the demand element 22.4 increases progressively with the progressive temperature decrease of the water;
- this results in the degree of phase transition (within the demand element 22.4) from hot gas to liquid phase of the refrigerant becoming progressively greater; and
- it results, further, in the pass-through of refrigerant in hot gaseous phase from the demand element 22.4 to the base element 22.3 decreasing progressively.

With the progressive decrease in water temperature in the geyser 120, the heating load, in this state, is transferred progressively to the base element. In a steady-state in which most of the water in the geyser 120 is relatively cold, the bulk of the phase transition of the refrigerant from gaseous to liquid phase occurs in the base element 22.3. As a result, the base element 22.3 generates the bulk of the latent heat of condensation.
Typical heating load distribution transitions progressively:

- from steady-state: base element>60%; demand element<40%;
- through interim state: base element>40%; demand element<60%;
- to steady-state: base element>60%; demand element<40%.

State 3|Instantaneous (Non-Sustained) Demand

In the event of a state of hot water demand, where the hot water demand is instantaneous but not sustained, typically the inflowing cold water introduces insufficient quantities of cold water into the geyser tank 120.1 to change the refrigerant cycle completely from that described with reference to State 1 (low demand) to State 2 (high demand).
In this state:

- the temperature of the water in the geyser 120 is initially relatively stable at or near the preset hot water temperature;
- as a result of the non-sustained, instantaneous water demand, a non-sustained water temperature differential develops between the water adjacent the demand element 22.4 and the water adjacent the base element 22.3;
- the heat demand of the water adjacent the base element 22.3 is relatively low;
- the heat demand of the water adjacent the demand element 22.4 is relatively high;
- refrigerant heat discharge from the demand element 22.4 is relatively high;
- the degree of phase transition (within the demand element 22.4) from hot gas to liquid phase of the refrigerant increases;
- most of the heating in this state is provided by the demand element 22.4, in which the bulk of the phase transition of the refrigerant from gaseous to liquid phase occurs and which, as a result, generates the bulk of the latent heat of condensation; and
- as the temperature of the water in the geyser 120 returns to the preset hot water temperature, the geyser and refrigeration circuit revert to State 1 (low demand).

Typical heating load distribution−instantaneous (non-sustained) demand:

- base element>40%; demand element<60%.

Because the dual function water heater and air conditioner unit 10 relies, for heating and cooling, on a free running electric motor and a compressor that imposes a relatively low load on the compressor motor, the electrical load imposed, by the unit 10, on the electricity supply system is relatively low and has a relatively low current draw. In fact, when the unit 10 operates in CYCLE 2—WATER HEATING AND AIR-CONDITIONING COOLING—water heating is essentially free, since the hot gaseous phase refrigerant exiting the interior unit heat exchanger 16 is applied directly to the water heater heat exchanger 22, in which the refrigerant is condensed and the latent heat of condensation is transferred, by the finned tube water heater heat exchanger 22 directly to the water in the geyser 20.
In most of the operating modes and cycles described in this specification, the dual function water heater and air conditioner unit 10 operates at a Coefficient of Performance (COP) of 3 or better—the COP of a heat pump or air-conditioning system is a ratio of useful heating or cooling compared to energy input—COP=Q/W, where Q (heat supplied or removed (heating or cooling)) is compared to W (required work—the energy input required).
Besides such power and cost saving benefits, the low power utilization of the dual function unit 10 makes it possible to operate the unit 10 on battery power, which is currently not possible with existing water heaters or geysers.
Further to enhance the battery compatibility of the dual function unit 10, the unit drive electronics could be configured to include a motor soft starter, a device commonly used with AC electrical motors temporarily to reduce the starting torque and electric current surge of the motor during start-up.

Claims

What is claimed is:

1-11. (canceled)

12. A dual function water heater and air-conditioning unit comprising an air-conditioner subassembly and a water heater subassembly interconnected for circulation of a refrigerant within a fluidic circuit configured as a vapour compression refrigeration circuit:

the air-conditioner subassembly comprising an interior air-conditioning unit configured for installation within a building and an exterior air-conditioning unit configured for installation outside the building;

the interior air-conditioning unit including a first heat exchanger interconnected in-circuit in the refrigeration circuit;

the exterior air-conditioning unit including a second heat exchanger interconnected in-circuit in the refrigeration circuit;

the water heater subassembly including a water tank and a third heat exchanger interconnected in-circuit in the refrigeration circuit and configured for location within the water tank;

the first and second heat exchangers each including outlet tubes and first and second inlet tubes in-circuit in the refrigeration circuit;

the third heat exchanger including inlet and outlet tubes in-circuit in the refrigeration circuit;

the first refrigerant inlet tube of each of the first and second heat exchangers having an expansion valve installed in the refrigeration circuit upstream of the heat exchanger;

the second refrigerant inlet tube of each heat exchanger having no expansion valve;

the refrigeration circuit including a plurality of control valves settable to direct the refrigerant within the refrigeration circuit;

the control valves being settable such that:

at least one of the first or second heat exchangers is configured to operate as an evaporator, in which setting of the control valves, refrigerant is introduced into the heat exchanger through the expansion valve installed in the first inlet tube of that heat exchanger;

at least one of the first or second heat exchangers may be configured to operate as a condenser, in which setting of the control valves, refrigerant is introduced into the heat exchanger through the second inlet tube of that heat exchanger; and

the third heat exchanger may be configured to operate as a water heater within the water tank, in which setting of the control valves, the third heat exchanger is configured to operate as a condenser.

13. The dual function water heater and air-conditioning unit of claim 12, in which the control valves are preferably settable such that the unit is configured to operate in one of a plurality of modes of operation selected from:

a first mode of operation—water heating only;

a second mode of operation—water heating and air conditioner cooling;

a third mode of operation—air-conditioning cooling only; and

a fourth mode of operation—air-conditioning heating only.

14. The dual function water heater and air-conditioning unit of claim 13, wherein, in the first mode of operation—water heating only—the control valves are set such that:

the first heat exchanger is switched out of the refrigeration circuit and no refrigerant is supplied to the first heat exchanger;

the third heat exchanger is configured to operate as a condenser, in which setting of the control valves, refrigerant is introduced from the compressor into the third heat exchanger by way of the third heat exchanger inlet tube; and

the second heat exchanger is configured to operate as an evaporator, in which setting of the control valves, refrigerant is supplied to the second heat exchanger from the third heat exchanger outlet tube through the first inlet tube of the second heat exchanger, by way of the expansion valve of the second heat exchanger.

15. The dual function water heater and air-conditioning unit of claim 13, wherein, in the second mode of operation—water heating and air conditioner cooling—the control valves are set such that;

the second heat exchanger is switched out of the refrigeration circuit and no refrigerant is supplied to the second heat exchanger;

the first heat exchanger is configured to operate as an evaporator, in which setting of the control valves, refrigerant is supplied to the first heat exchanger from the third heat exchanger outlet tube through the first inlet tube of the first heat exchanger, by way of the expansion valve of the first heat exchanger.

16. The dual function water heater and air-conditioning unit of claim 13, wherein, in the third mode of operation—air-conditioning cooling only—the control valves are set such that:

the third heat exchanger is switched out of the refrigeration circuit and no refrigerant is supplied to the third heat exchanger;

the second heat exchanger is configured to operate as a condenser, in which setting of the control valves, refrigerant is introduced from the compressor into the second heat exchanger by way of the second inlet tube of the second heat exchanger; and

the first heat exchanger is configured to operate as an evaporator, in which setting of the control valves, refrigerant is supplied to the first heat exchanger from the second heat exchanger outlet tube through the first inlet tube of the first heat exchanger, by way of the expansion valve of the first heat exchanger.

17. The dual function water heater and air-conditioning unit of claim 13, wherein, in the fourth mode of operation—air-conditioning heating only—the control valves are set such that:

the first heat exchanger is configured to operate as a condenser, in which setting of the control valves, refrigerant is introduced from the compressor into the first heat exchanger by way of the second inlet tube of the first heat exchanger; and

the second heat exchanger is configured to operate as an evaporator, in which setting of the control valves, refrigerant is supplied to the second heat exchanger from the second heat exchanger outlet tube through the first inlet tube of the second heat exchanger, by way of the expansion valve of the second heat exchanger.

18. The dual function water heater and air-conditioning unit of claim 13, in which the water tank is the water tank of a water heater/geyser.

19. The dual function water heater and air-conditioning unit of claim 13, including an electric heater element located in the water tank.

20. The dual function water heater and air-conditioning unit of claim 12, in which the third heat exchanger is configured as a direct-heating immersion heating element comprising a finned tube heat exchanger that is installed within the interior of the geyser for direct heat transfer from the heat exchanger to the water within the geyser.

21. The dual function water heater and air-conditioning unit of claim 20, in which the third heat exchanger includes a protector tube secured to the heat exchanger and configured to extend about the outside of the finned tubes of the heat exchanger.

22. The dual function water heater and air-conditioning unit of claim 20, in which the third heat exchanger is configured to conform in shape, size, general form factor and physical connection equipment to current standardised conventional electric water heater elements, such that the water heater heat exchanger is capable of being retrofitted into a conventional electric water heater in place of the conventional electrical element.

23. The dual function water heater and air-conditioning unit of claim 22, in which the third heat exchanger includes a protector tube secured to the heat exchanger to extend about the outside of the finned tubes of the heat exchanger.