Refrigeration – Reversible – i.e. – heat pump
Reexamination Certificate
1999-10-22
2001-05-08
McDermott, Corrine (Department: 3744)
Refrigeration
Reversible, i.e., heat pump
Reexamination Certificate
active
06227003
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to an improved reverse-cycle heat pump system, and more specifically, to a reverse-cycle heat pump system comprising components that render the system more efficient in cooling during operation in the cooling mode.
Conventional reverse-cycle heat pump refrigeration systems comprise two reversible heat exchangers. One heat exchanger is placed in the space to be heated or cooled and the other heat exchanger is placed outside that space. In the heating mode, the inside heat exchanger functions as the condenser while the outside heat exchanger functions as the evaporator. In cooling mode, the roles are reversed (i.e. the inside heat exchanger functions as the evaporator and the outside heat exchanger functions as the condenser). The heat exchangers are connected to one another by a series of conduits or circuits through which refrigerant is pumped via a motorized compressor. A four-way valve is disposed within the series conduits and functions to direct the flow of refrigerant from the compressor to the appropriate heat exchanger. While the direction of refrigerant through the compressor always flows in one direction, the flow of refrigerant may change direction throughout the rest of the system depending upon whether the system is operating in the heating mode or cooling mode.
In heating mode, the compressor pumps hot, high-pressure refrigerant gas to the indoor heat exchanger, or “condenser,” where the gas is condensed into a high pressure liquid as it gives off latent heat of condensation into the conditioned area. The high-pressure liquid then flows out of the condenser through a conduit or series of conduits and enters the outdoor exchanger, or “evaporator,” as a low pressure liquid, wherein it absorbs latent heat from the outside and vaporizes. Low pressure refrigerant gas then exits the evaporator and returns to the compressor to begin the cycle again. Heating of the conditioned space is further aided by a fan positioned behind the condenser to blow heated air therein. A fan disposed behind the evaporator aids in drawing in heat from the outside into the system.
In cooling mode, the compressor pumps hot, high-pressure refrigerant gas in the reverse direction to the outdoor heat exchanger (i.e. “condenser”) where the refrigerant gas is condensed into a high pressure liquid as it gives off latent heat of condensation to the outside. The resulting high-pressure refrigerant liquid then flows out of the condenser through a conduit or series of conduits and enters the indoor heat exchanger (i.e. “evaporator”) wherein it absorbs latent heat from the area to be conditioned and consequently vaporizes. Cooling of the conditioned space is further aided by a fan positioned behind the evaporator to blow cooled air therein. A fan disposed behind the condenser aids in removing heat from the interior of the system.
A major disadvantage inherent in reverse cycle heat pumps is that the efficiency of the system in cooling mode is about 60% compared to that of the heating mode. The reason for this inefficiency is that it takes a much greater pressure drop on the condenser side of the system to dissipate the heat therefrom than it does to absorb heat from the evaporator side. Thus, in heating mode, a greater refrigerant charge is therefore necessary to heat a desired area; however, in the cooling mode, it is more difficult to dissipate the heat generated within the condenser to the outside, where temperatures are presumably already over 80° F. Stated another way, there is generally more refrigerant within the system than needed to cool the inside air or water in a given area. Moreover, this higher refrigerant charge will tend to generate more heat within the heat pump system, thereby diminishing the cooling effect of the evaporator.
Prior art reverse cycle heat pump systems attempt to improve cooling mode efficiency by employing complex double heat exchangers with check valves. Such devices add a significant monetary cost to the product. It is therefore desirable to have a reverse-cycle heat pump system that accomplishes greater cooling efficiency in cooling mode without compromising the heating efficiency in heating mode, whereby the heat pump system employs components of minimal complexity and cost.
SUMMARY
The present invention, in certain aspects, is directed to an improved reverse cycle heat pump refrigeration system that employs components that improve the cooling efficiency of the system. In particular, the present invention, in certain embodiments, comprises (a) a compressor and (b) a first heat exchanger and a second heat exchanger, wherein each of the heat exchangers is adapted to function interchangeably as an evaporator and a condenser, depending upon whether the system is operating in cooling mode or heating mode. The heat exchangers are disposed within the system such that in cooling mode, the first heat exchanger functions as a evaporator and the second heat exchanger functions as an condenser, and wherein in heating mode, the first heat exchanger functions as an condenser while the second heat exchanger functions as a evaporator. The system further includes (c) at least one first conduit in communication with the compressor and each of the heat exchangers, the conduit being adapted for carrying refrigerant through the system to each of the heat exchangers, wherein the conduit also includes a return conduit for carrying refrigerant gas back to the compressor, (d) a valve in communication with the one or more conduits and configured to reverse the flow of refrigerant from the compressor to the heat exchangers depending upon whether the system is operating in a cooling mode or a heating mode and (e) a second conduit connecting the heat exchangers. The second conduit includes (i) a refrigerant metering device disposed near the second heat exchanger, and (ii) a coiled section disposed near the first heat exchanger, wherein the coiled section is adapted for containing any excess refrigerant liquid that may back up from the first heat exchanger therein when the system is operating in cooling mode (i.e. the first heat exchanger is functioning as an evaporator). Specifically, the coiled section is positioned near the refrigerant-entry end of the evaporator in cooling mode.
The inventive system is thereby designed such that when the system is operating in heating mode, the valve is activated to direct refrigerant pumped from the compressor through one or more conduits to the second heat exchanger where the refrigerant gas is condensed into liquid, through the second conduit to the first heat exchanger where the liquid is vaporized into gas, and back to the compressor via the return conduit. In cooling mode, the inventive system is designed such that the valve is activated to direct refrigerant pumped from the compressor through the one or more conduits to the first heat exchanger where the refrigerant gas is condensed into liquid, through the second conduit to the second heat exchanger where the liquid is vaporized into gas, and back to the compressor via the return conduit.
In certain aspects of the invention, the second conduit further includes a reverse direction filter dryer disposed between the metering device and coiled section of the second conduit. Preferably, the metering device of the second conduit is an orifice coupler connected to, and in communication with, the second conduit. The coiled section of the second conduit has a refrigerant carrying capacity substantially equivalent to the refrigerant carrying capacity of the first heat exchanger.
The present invention is also directed to the inventive conduit assembly for installation on a reverse-cycle heat pump refrigeration system and comprises a conduit or tubing having a first end for installation into a first heat exchanger of a reverse-cycle heat pump refrigeration system and a second end for installation into a second heat exchanger of the reverse-cycle heat pump refrigeration system, wherein the second heat exchanger is configured to function as an evaporator
Barrow Laura G.
Jiang Chen-Wen
McDermott Corrine
LandOfFree
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