Patent Application
20060144060
1. Field of the Invention
This invention relates to refrigeration systems, and more particularly to heat pump and air conditioning units that include an automatic defrost cycle.
2. Description of the Related Art
In
The warm liquid refrigerant leaves the condenser and then flows through a bypass valve and into a main liquid line. The main liquid line delivers the warm liquid refrigerant through a second expansion valve, where it expands and vaporizes and gains latent heat from the outside air. The cool vapor refrigerant vapor from the outdoor coils then travels through the reversing valve and returns to the compressor where the cycle begins again.
It is well known that heat pumps can operate in both a cooling mode and a heating mode. For example,
It is well known that during cold weather, ice and frost builds up on the evaporator on a heat pump when operating in a heating mode. If the build up of ice and frost continues and is not removed from the evaporator, the efficiency of the heat pump is gradually reduced.
Heat pumps used in the prior art have a defrost cycle that removes ice and frost on the evaporator by reversing the direction of the hot vapor refrigerant through the coils similar to the flow of refrigerant shown in
One important drawback with ‘hot gas defrost systems’ is that the unit's primary heating cycle must be reversed during the defrost cycle. When this occurs, not only is heat no longer added to the building, but heat from the warm air located inside the building is transmitted outside the building. In order to overcome the lost of heat from the building during the defrost cycle some buildings have secondary heating units. Unfortunately, these secondary heating units add to the overall cost of the heating and cooling systems.
It is an object of the present invention to provide a heat exchange system for a heat pump or combination heat pump/air conditioning unit that automatically defrosts the system's outdoor coils during use.
It is another object of the present invention to provide such a heat exchange system that continues to supply heat to the building as the outdoor coils are defrosted.
These and other objects of the invention are met by a heat exchanger liquid refrigerant defrost system disclosed herein specifically designed to defrost the coils used on an outdoor heat exchanger used on a building ‘heat only’ type heat pump unit (called a ‘heat pump’, herein after) or combination heat pump/air condition unit. The system is specifically designed to be used with most or all of the inside components commonly used on a standard heat pump or combination heat pump/air conditioning unit so that the system may be easily retrofitted on existing units or easily incorporated into new systems with a minimal number of new components.
The system includes an outdoor heat exchanger containing at least two coil subsystems. Each coil subsystem is connected to a main liquid line that connects to an indoor heat exchange coil system. Each coil subsystem includes an inlet tubing section that extends between the main liquid line to a t-joint connected to a first end tube section. Disposed on the inlet tubing section is a bypass solenoid. Disposed in the first end tube section is a suction line solenoid. The distal end of the first end tube section connects to an outdoor refrigerant transfer line which extends into the building and connects to a suction accumulator when used with a heat pump unit or connects to a reversing valve when used on a combination heat pump/air conditioning unit.
Each coil subsystem winds back and forth inside the outside heat exchanger's outer housing and terminates at a second end tube section. Disposed in the second end tube section is a metering device and bypass check valve. The distal end of the second end tube section connects to a secondary liquid line that extends between all of the coil subsystems located in the outer housing. The opposite end of the secondary liquid line connects to the indoor unit's liquid line. Located near the distal end of the secondary liquid line is a liquid restrictor valve.
When the system is used in a combination heat pump/air conditioning unit, a secondary conduit with a second bypass check valve disposed therein is placed between the distal end of the secondary liquid line and the main liquid line and parallel to the liquid restrictor valve.
During use, the bypass solenoid and the suction line solenoid, the metering device, the bypass check valve, the liquid restrictor valve, and the secondary check valve operate in a coordinated manner so that the flow of warm liquid refrigerant through the coil subsystems in the outdoor heat exchanger is optimized to exchange heat. In the preferred embodiment, the bypass solenoid and the suction line solenoid are electrical units controlled by a central control unit. The metering device, which is located side-by-side to the first bypass check valve in the secondary tube section, is used to change the state of the refrigerant from a warm liquid flowing through said second tube section to a vapor. When the coil subsystem operates in defrost mode, warm liquid refrigerant flows through the first bypass check valve and directly into the secondary tube section. During operation, the restrictor valve disposed in the secondary liquid line selectively opens or closes in a direction opposite to the bypass solenoid. The restrictor valve too may be an electrical valve and controlled by the central control unit. Alternatively, the restrictor valve may be a mechanical valve or a pneumatic valve.
When defrosting on one or more of the coil subsystems is necessary, the control unit selectively controls the operation of the bypass solenoid and the suction line solenoid so that the coil subsystems are individually and sequentially defrosted one or two at a time while the other coil subsystems continue to exchange heat. When all of the coils subsystems have been defrosted, all of the coil subsystems may resume normal operating mode and exchange heat or begin another defrost cycle again.
During the heat mode, warm liquid refrigerant is delivered to all of the coil subsystems in the outdoor heat exchanger. The warm liquid refrigerant travels through a metering device and evaporates, inside the coil subsystems thus gaining latent heat from the outside air.
When the unit is switched to defrost mode, the positions of the solenoids and valves are altered so that warm liquid refrigerant is only directly transmitted to the coil subsystem(s) to be defrosted. When the warm liquid refrigerant leaves the defrosted coil subsystem(s), it is delivered to the other coil subsystems where it evaporates and gains the latent heat from the outside air.
Because warm liquid refrigerant is first used to defrost a coil subsystem and then delivered to the remaining coil subsystems to undergo heat exchange, the amount of energy required to defrost the coil subsystems in the outside heat exchanger is lower than the amount of energy normally needed to defrost the single coil used in a standard outdoor unit. Also, because the other coil subsystems continue to exchange heat while one coil subsystem is defrosted, the heated air is continuously provided to the building thereby eliminated the need for a supplemental heat source.
FIGS. 4C-F are a series of diagrams that shows different coil subsystems being individually defrosted while the other coil subsystems continue to provide indoor heat.
Referring to the accompanying FIGS. 3A-E and FIGS. 4A-F, there is shown a heat exchanger liquid refrigerant defrost system 10 specifically designed to automatically defrost one or more coils systems on an outdoor heat exchanger used with a building's heat pump unit 1 or combination heat pump/air conditioning unit 2. While one coil subsystem 10 is defrosting, the other coils systems continue or operate normally and exchange heat for the building. The system 10 includes an outdoor heat exchanger 12 that replaces the outdoor heat exchanger commonly used with the standard heat pump unit or combination heat pump/air conditioning. The outdoor heat exchanger 12 is specifically designed to be used with existing indoor components (i.e. suction accumulator 76, compressor 80, reversing valve 90, indoor coil subsystem 85, second by-pass check valve 87, etc,) commonly used with the standard heat pump unit or combination heat pump/air conditioning unit thereby allowing it to be used with new units or retrofitted with existing units.
The heat exchanger 12 includes an outer housing 14 containing at least two interconnected yet separate coil subsystems. In the embodiment shown in the Figs, the outer housing 14 is a rigid structure with four coil subsystems 16, 17, 18, and 19 located therein. Referring to
Each coil subsystem 16-19 includes a main body section 26 winds back and forth inside the outer housing 14 and terminates at a second end tube section 28. Disposed in the second end tube section 28 is a metering device 30 and a first bypass check valve 50 aligned in a side-by-side manner. The distal end of the second end tube section 28 that extends beyond the metering device 30 and the first bypass check valve 50 connects to a secondary liquid line 35 that extends between all of the coil subsystems 16-19. The opposite end of the secondary liquid line 35 connects to the main liquid line 65 located below the last coil subsystem 19.
Located near the distal end of the secondary liquid line 35 is a liquid restrictor valve 60 which controls the flow of refrigerant there between. As shown in FIGS. 4A-F and
As shown in
Located inside the reversing valve 90 are two control gates 92, 94 that control the flow of cool vapor refrigerant 120 and hot gas refrigerant 130 there through. When cool vapor refrigerant 120 is delivered to the reversing valve 90 via the return conduit 86 the second control gate 94 is rotated so that the cool vapor refrigerant 120 is delivered to the suction accumulator 76. The first control gate 92 is also rotated so that hot gas refrigerant 130 delivered from the compressor 80 via line 82 is delivered to the outside refrigerant transit line 55. The outlet port on the suction accumulator 76 is connected to the inlet port on the compressor 80 to complete the circuit.
b and 7 shows the operation of the combination heat pump/air conditioning unit 2 operating in heating mode. FIGS. 3B-E and FIGS. 4B-F are a series of illustrations showing how one coil unit is defrosted while the remaining coil subsystems in a heat pump unit 1 or combination heat pump/air conditioning unit 2 continue to operate in a heating mode. It should be understood that while in the following description only one coil subsystem is defrosted, the control unit 100 could be programmed so that two or more coil subsystems could be simultaneously defrosted while the one or more of the coil subsystems continue to exchange heat. It should also be noted that while the coil subsystems are described as being defrosted sequentially from top to bottom, the order in which the coil subsystems in the outer housing are defrosting may vary in different applications.
The defrost cycle is triggered by a timer 105 connected to the control unit 100 or by sensors 110 attached to the coil subsystems 16, 17, 18, 19 that are activated when the coil subsystems 16-19 reach a specific temperature. When triggered, the control unit 100 automatically initiates the defrost cycle on one of the coil subsystems. Referring to
The above process of sequentially defrosting the individual coil subsystems is repeated until all of the coil subsystems 16-19 have been defrosted. The entire cycle may be continuously repeated or repeated when excess defrost has been detected or a specific amount of time has elapsed.
As mentioned above the restrictor valve may be an electrical valve controlled by the control unit 100 or a mechanical valve or pneumatic valve controlled by flow of refrigerant.
In summary, the above system 10 uses the flow of warm liquid refrigerant 140 through the coil subsystems 16-19 to selectively control defrosting of the coil subsystems one at a time. As the defrost process takes place in coil subsystem, the coil subsystems continue to exchange heat and warm the building. When the coil subsystem is defrosted, warm liquid refrigerant 140 is then directed to another coil subsystem. When all of the coils systems in the outer housing 12 are sequentially defrosted, the defrost cycle may begin again with the first coil subsystem. An important benefit of the system is the amount of energy required to defrost the coil subsystem is lower than the amount of energy need to defrost the coils in a standard outdoor units. Also, because the other coil subsystems continue to operated while one set of coil subsystem is defrosted, the heat is continuously provided to the building thereby eliminated the need for supplemental heating units.
In compliance with the statute, the invention described herein has been described in language more or less specific as to structural features. It should be understood, however, that the invention is not limited to the specific features shown, since the means and construction shown is comprised only of the preferred embodiments for putting the invention into effect. The invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the amended claims, appropriately interpreted in accordance with the doctrine of equivalents.
