Patent Application
20180372354
The present disclosure is directed to reversible HVAC systems and in particular to charge compensators.
HVAC systems can comprise an indoor heat exchanger, an outdoor heat exchanger, a compressor, an expansion device, and other components. Some HVAC systems may comprise a reversing valve, enabling the system to function both as a heat pump and as an air conditioner. During heating modes the indoor heat exchanger functions as a condenser and the outdoor heat exchanger functions as an evaporator. During cooling modes the roles of the heat exchangers are reversed. The indoor and outdoor heat exchangers are typically the same size, but not always. Different sized heat exchangers may be due to space constraints, material differences, or other reasons. The volume ratio of indoor to outdoor coils may lead to charge imbalances, leading to high pressure and other problems.
One possible embodiment under the present disclosure can comprise a compensator for an HVAC system operable in both a cooling mode and a heating mode, comprising: an inlet configured to be coupled to a liquid line of a heat exchanger; a tank configured to receive refrigerant from the liquid line when the HVAC system is in a heating mode; and a heater electrically coupled to the HVAC system, wherein when the HVAC system is in a cooling mode then the heater is turned on, wherein the heater is operable to cause refrigerant in the compensator to migrate out of the compensator.
Another possible embodiment under the present disclosure can comprise an HVAC system operable in both a heating mode and a cooling mode comprising: an indoor heat exchanger operable to receive a refrigerant and transfer heat between the refrigerant and another medium; a compressor operable to receive the refrigerant from the indoor heat exchanger when the HVAC system is in a cooling mode; an outdoor heat exchanger operable to receive the refrigerant from the compressor when the HVAC system is in a cooling mode, an outlet of the outdoor heat exchanger comprising a liquid line when the HVAC system is in a cooling mode; an expansion valve operable to receive the refrigerant from the outdoor heat exchanger and to direct the refrigerant toward the indoor heat exchanger when the HVAC system is in a cooling mode; and a compensator comprising: an inlet configured to be coupled to the liquid line of the outdoor heat exchanger; a tank configured to receive refrigerant from the liquid line when the HVAC system is in a heating mode; and a heater electrically coupled to the HVAC system, wherein when the HVAC system is in a cooling mode then the heater is turned on, wherein the heater is operable to cause refrigerant in the compensator to migrate out of the compensator.
Another possible embodiment under the present disclosure can comprise a method of alleviating charge imbalance in an HVAC system that is operable in both a cooling mode and a heating mode, comprising: circulating a refrigerant through an indoor heat exchanger, an outdoor heat exchanger, a compressor and an expansion device, wherein a compensator is coupled to a liquid line of the outdoor heat exchanger; allowing refrigerant to flow into the compensator when the HVAC system is in a heating mode; and heating the compensator when the HVAC system is in a cooling mode in order to cause the refrigerant to migrate out of the compensator.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
When aluminum components are used to replace copper ones in HVAC systems, the load carrying capacities of the components may change, leading to charge imbalance issues and high pressure. A typical HVAC system comprises both an indoor and an outdoor heat exchanger. Copper has historically been the preferred material for heat exchanger tubes. Aluminum is being used more and more frequently however. The move from copper to aluminum may be for environmental, cost, or other reasons. Typically, the same material is used for both the indoor and outdoor heat exchangers. Sometimes however, existing HVAC systems are repaired or updated by replacing a copper component with an aluminum one, or another material switch. When an aluminum coil replaces a copper coil an installer usually keeps the same physical size due to pre-existing space constraints. Because aluminum is weaker than copper, a similarly sized (same outside diameter) aluminum heat exchanger tube will have a smaller inner diameter than a copper tube. This is because the aluminum walls must be made thicker to provide an equivalent amount of strength. But this means that the aluminum coil can circulate less refrigerant than a similar copper coil. One consequence of combining, for example, an indoor aluminum coil with an outdoor copper coil can be a charge imbalance, i.e. the heating and cooling modes require different amounts of refrigerant. During heating operations there may be too much refrigerant passing through the indoor aluminum coil creating high pressure. The removal of refrigerant can help relieve the pressure. But when the system is switched to cooling mode the larger amount of refrigerant is needed to achieve greater heat transfer and provide sufficient cooling to the conditioned space. Similar problems can occur when space constraints force an indoor or outdoor coil to be smaller than the other, even if both coils are made of the same material.
Embodiments under the present disclosure can help solve the charge imbalance problems described above. A possible embodiment can be viewed referring to
During heating operations it may be desirable to remove refrigerant from the system 100. Compensator 170 comprises a connection to liquid line 133. During heating operations, high pressure drives an amount of refrigerant into compensator 170, relieving the pressure. During cooling operations, it is desired to retrieve the extra refrigerant within compensator 170 so that the cooling demand can be met. This is achieved by applying heat to compensator 170 via heater 172. Heater 172 can comprise a belly band heater similar to compressor crank case heaters, or another appropriate type of heater. Heater 172 can be coupled to a controller/processor/electronics 135 in the outdoor unit 160. Optionally, the heater 172 can be coupled to another controller/processor/server/electronics 180, such as a thermostat. When the controller 135 receives a command to begin cooling operations, then the heater 172 can receive a signal to turn on. Turning on heater 172 causes the temperature within compensator 170 to rise higher than the temperature of the indoor coil 110. Refrigerant migrates to cooler locations and refrigerant will therefore leave compensator 170. As refrigerant circulates in the system it will pass by the inlet to the compensator 170 and migrate toward the indoor coil 110 (because the indoor coil is lower temperature than the compensator). The preferred location for plumbing the compensator 170 into the refrigerant line is at the liquid line 133, or anywhere between the outdoor heat exchanger 130 and the expansion device 140.
A possible retrofit embodiment can be seen in
A preferred embodiment under the present disclosure comprises a retrofit solution. The teachings could also be implemented in newly-built systems. Solutions under the present disclosure will be particularly helpful when aluminum coils are used to replace copper coils in indoor units. Other embodiments under the present disclosure can be retrofit onto HVAC systems undergoing pressure or charge imbalance issues, even if both indoor and outdoor coils are built from the same materials. Even when copper coils replace copper coils, operating conditions may affect the new coil size or geometry, leading to possible charge imbalance issues. Sometimes an outdoor unit has to be replaced instead of the indoor unit. In these situations and others, the present disclosure can provide help in solving charge imbalances.
Embodiments under the present disclosure can comprise a variety of heat exchanger types, such as tube and fin, microchannel, and others. Other components such as expansion devices, compressors, reversing valves, and others, are not limited to one type of component but can take a variety of forms known to those skilled in the art.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
