Abstract:
In order to magnify capacity control of a refrigeration cycle for an increased efficiency and achievement of compactness, the refrigeration cycle includes a compressor, a four-way valve, a heat exchanger on a side of a heat source, a liquid receiver, a heat exchanger on a side of use, and an electronic expansion valve, all of which are connected other by pipes, and comprises a refrigerant circulating in the refrigeration cycle and being a non-azeotropic refrigerant, a second liquid receiver for taking out a refrigerant vapor from an upper portion of the liquid receiver to condense and store the refrigerant, and a pipe connecting the second liquid receiver to the liquid receiver via a shut-off valve.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a refrigeration cycle using a non-azeotropic refrigerant, and more particularly, to a refrigeration cycle suitable for a decrease in capacity and an increase in operation efficiency by changing the composition of a refrigerant circulating in the refrigeration cycle at low load.  
         PRIOR ART  
         [0002]    Conventionally, in order to exhibit a capacity conformed to load, a compressor is inverter-driven to change the mass flow rate of a refrigerant circulating in a refrigeration cycle. Another system, in which a non-azeotropic refrigerant is used as a refrigerant and a distiller is used to change the composition of the refrigerant for production of a capacity suitable for load at all times, is known and disclosed in, for example, Japanese Patent Unexamined Publication No. 9-196481.  
           [0003]    In the above-described prior art, the system adapted for capacity control through inverter-driving is difficult to operate at very low and very high speeds of compressor, so that it cannot but entail upper and lower limits in inverter frequency. Therefore, capacity control is effected by making the compressor on/off particularly at low load, thus leading to a poor efficiency. Also, with the system using a distiller, the distiller and a separation circuit thereof are large in scale to make it difficult for the system to be rendered compact in size.  
         BRIEF SUMMARY OF THE INVENTION  
         [0004]    An object of the present invention is to magnify capacity control for an increased efficiency and achievement of compactness. Another object of the present invention is to magnify the capacity on a side of low load to afford an energy-saving operation for a reduction in annual power consumption and adaptation to environment, such as prevention of destruction of ozone layer and an increase in recycle efficiency.  
           [0005]    In order to solve the above problems, the present invention provides a refrigeration cycle composed of a compressor, a four-way valve, a heat exchanger on the heat source side, a liquid receiver, a heat exchanger on the use side, and an electronic expansion valve, which are connected by piping, the refrigeration cycle comprising a refrigerant being a non-azeotropic refrigerant to circulate therein, a second liquid receiver for taking out a refrigerant vapor from an upper portion of the liquid receiver to condense and store the refrigerant, and a pipe for connecting the second liquid receiver to the liquid receiver via a shut-off valve.  
           [0006]    Thus, the use of a non-azeotropic refrigerant (for example, a HFC refrigerant mixture such as R407C having an ozone layer destruction coefficient of zero) results in that the refrigerant vapor in the liquid receiver contains much low boiling point refrigerant in composition and an amount of the refrigerant stored in the second liquid receiver and containing an abundant amount of low boiling point refrigerant can be changed by the opening and closing actions of the shut-off valve, so that the capacity of an air conditioner can be controlled by changing the composition ratio of a refrigerant circulating in the refrigeration cycle, and also a refrigerant rectifying column can be dispensed with which serves as separating components of the refrigerant mixture depending upon differences in boiling point among the respective component and which is liable to become large-sized, complicated, and expensive. Therefore, the number of on/off operations of an associated compressor can be decreased by increasing the capacity control range without hindering the compactness of an air conditioner, so that the air conditioner can be enhanced in efficiency and comfort.  
           [0007]    Also, the present invention provides a refrigeration cycle having a compressor, a heat exchanger on a side of a heat source, an electronic expansion valve, and a heat exchanger on a side of use, and using a non-azeotropic refrigerant as a circulating refrigerant, the refrigeration cycle comprising a liquid receiver provided between the heat exchanger on the heat source side and the heat exchanger on the side of sue, and a second liquid receiver connected to an upper portion of the liquid receiver through a pipe, and wherein a refrigerant vapor, in which a low boiling point refrigerant is rich, is taken out from the liquid receiver, and the taken-out refrigerant is condensed and stored or returned to the refrigeration cycle, whereby the refrigerant circulating in the refrigeration cycle is changed in composition.  
           [0008]    Further, in the above-described refrigeration cycle, the refrigerant vapor is preferably caused to make heat exchange with a refrigerant on a suction side of the compressor to thereby be condensed.  
           [0009]    Further, in the above-described refrigeration cycle, the second liquid receiver is desirably connected to the suction side of the compressor via a second shut-off valve and a pressure reducing mechanism.  
           [0010]    Further, the above-described refrigeration cycle desirably further comprises a heat exchanger for heat exchanging the refrigerant vapor with a refrigerant on the suction side of the compressor, a shut-off valve provided between the liquid receiver and the heat exchanger, and a pipe connecting the second liquid receiver to the suction side of the compressor via a pressure reducing mechanism.  
           [0011]    Further, the above-described refrigeration cycle desirably further comprises a heat exchanger for heat exchanging the refrigerant vapor with a refrigerant on the suction side of the compressor, a shut-off valve provided between the liquid receiver and the heat exchanger, a pipe connecting the second liquid receiver to the suction side of the compressor via a pressure reducing mechanism, and a pipe connecting the liquid receiver to the second liquid receiver.  
           [0012]    Further, the above-described refrigeration cycle desirably further comprises a heat exchanger for heat exchanging the refrigerant vapor with a refrigerant on the suction side of the compressor: and a check valve provided between the liquid receiver and the heat exchanger.  
           [0013]    Further, the present invention provides a refrigeration cycle including an outdoor unit provided with a compressor and a heat exchanger on a side of a heat source, and a plurality of indoor units, and using a non-azeotropic refrigerant as a circulating refrigerant, the refrigeration cycle comprising a liquid receiver provided between the heat exchanger on the heat source side and the indoor units, and a second liquid receiver connected to the liquid receiver via a pipe, and wherein a refrigerant vapor, in which a low boiling point refrigerant is rich, is taken out from the liquid receiver and the taken-out refrigerant is condensed and stored, whereby the refrigeration cycle is operated with a high ratio of a high boiling point refrigerant contained in the refrigerant circulating in the refrigeration cycle.  
           [0014]    Further, the present invention provides a refrigeration cycle including an outdoor unit provided with a compressor and a heat exchanger on a side of a heat source, and a plurality of indoor units, the refrigeration cycle comprising a refrigerant circulating in the refrigeration cycle, and being a non-azeotropic refrigerant, and a liquid receiver provided between the heat exchanger on the heat source side and the indoor units, and wherein a refrigerant vapor, in which a low boiling point refrigerant is rich, is taken out from the liquid receiver at low load, and the taken-out refrigerant is condensed and stored, whereby the number of times, in which the compressor is made off, is reduced. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a schematic diagram showing an embodiment of the present invention;  
         [0016]    [0016]FIG. 2 is a schematic diagram showing another embodiment of the present invention;  
         [0017]    [0017]FIG. 3 is a schematic diagram showing still another embodiment of the present invention;  
         [0018]    [0018]FIG. 4 is a schematic diagram showing a further embodiment of the present invention;  
         [0019]    [0019]FIG. 5 is a schematic diagram showing a still further embodiment of the present invention;  
         [0020]    [0020]FIG. 6 is a schematic diagram showing still another embodiment of the present invention; and  
         [0021]    [0021]FIG. 7 is a schematic diagram showing still another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]    Embodiments of the present invention will now be described in detail with reference to FIGS.  1  to  7 .  
         [0023]    [0023]FIG. 1 shows an embodiment. In FIG. 1, the reference character A denotes an outdoor unit, and B an indoor unit. The reference numeral  10  denotes a compressor,  20  a four-way valve for switching the flow direction of a refrigerant according to the heating and cooling operations,  30  a heat exchanger on a heat source side,  40  a (first) liquid receiver,  50  a liquid connection pipe,  60  an electronic expansion valve in the indoor unit,  70  a heat exchanger on a use side,  80  a gas connection pipe,  130  a second liquid receiver for storing a condensate containing an abundant amount of a low boiling point liquid,  110  a pipe for directing a refrigerant vapor in the first liquid receiver  40  to a second liquid receiver  130 , and  150  a pipe for directing a liquid refrigerant in the second liquid receiver  130  to the first liquid receiver  40 , and connected from a lower portion of the liquid receiver  130  to the liquid receiver  40  via a shut-off valve  140 . The second liquid receiver  130  is installed above the first liquid receiver  40 . Arrows in the drawings indicate the direction, in which a refrigerant flows, solid lines indicating a cooling operation and broken lines indicating a heating operation.  
         [0024]    Since the refrigerant circulating in the refrigeration cycle is a non-azeotropic refrigerant, a refrigerant vapor accumulating in an upper portion of the first liquid receiver  40  has that composition, in which a low boiling point refrigerant is rich, due to the low boiling point refrigerant being more liable to vaporize than a high boiling point refrigerant. When the shut-off valve  140  is closed, the refrigerant vapor, in which the low boiling point refrigerant is rich, in the first liquid receiver  40  performs heat exchange with the outside air to be stored in the second liquid receiver  130 . As a result, the refrigerant circulating in the refrigeration cycle becomes lean in the low boiling point refrigerant and so circulates with a high ratio of the high boiling point refrigerant in composition.  
         [0025]    When the shut-off valve  140  is opened, due to the second liquid receiver  130  being installed above the first liquid receiver  40 , the liquid refrigerant in the second liquid receiver  130  returns to the first liquid receiver  40  through the pipe  150  under gravity. Therefore, the low boiling point refrigerant does not accumulate in the second liquid receiver  130 , and so the composition in the refrigeration cycle does not change.  
         [0026]    As described above, if a liquid refrigerant, in which the low boiling point refrigerant is rich, is stored in the second liquid receiver  130  at low load, a refrigerant of that composition, in which the high boiling point refrigerant is rich, circulates in the main refrigeration cycle. Therefore, the refrigeration cycle can be decreased in capacity and so the on/off operation of the compressor can be reduced for an increased in efficiency. Also, the shut-off valve  140  is opened at high load to permit a refrigerant, in which the low boiling point refrigerant is rich, to be returned to the main refrigeration cycle, so that the refrigerant circulating in the refrigeration cycle is restored with respect to composition to enable increasing the capacity.  
         [0027]    [0027]FIG. 2 shows a second embodiment, in which the reference numeral  120  denotes a heat exchanger for making heat exchange between the refrigerant vapor from the first liquid receiver  40  and a refrigerant sucked into the compressor  10 . The refrigerant vapor in the first liquid receiver  40  is liquefied by heat exchange with the outside air in the above-described embodiment, but it does not liquefy under the condition that the outside air is high in temperature. Hereupon, when the refrigerant vapor is caused to make heat exchange with a refrigerant on a suction side of the compressor where the refrigerant is always made low in temperature, the refrigerant is changed in composition independently of the outside air temperature to make the capacity variable.  
         [0028]    [0028]FIG. 3 shows still another embodiment, in which the pipe  150  communicated to the liquid in the second liquid receiver  130  is connected to the compressor suction side via the shut-off valve  140  and a capillary  180 .  
         [0029]    In the embodiment shown in FIG. 1 or  2 , gravity is used to remove the liquid refrigerant in the second liquid receiver  130 , so that there is imposed a restriction that a liquid level in the second liquid receiver  130  should be higher than that in the first liquid receiver  40 . In this embodiment, however, the liquid refrigerant stored in the second liquid receiver  130  is returned to the compressor suction side through the capillary by virtue of a pressure difference, and so the positional relationship between the first and second liquid receivers becomes free of any restrictions. While the pipe  150  connects to an suction pipe this side of the heat exchanger  120  in FIG. 3, it may be also connected to the suction pipe that side of the heat exchanger  120  and between the compressor  10  and the heat exchanger  120 .  
         [0030]    [0030]FIG. 4 shows still another embodiment. When the circulating refrigerant should not be changed in composition, the shut-off valve  140  is opened to remove the liquid refrigerant in the second liquid receiver  130  in the embodiment shown in FIG. 3. Consequently, the refrigerant vapor in the first liquid receiver  40  will bypass the compressor  10 . In the present embodiment, when the liquid refrigerant in the second liquid receiver  130  is to be removed, the shut-off valve  140  is closed to render an interior of the second liquid receiver  130  low in pressure, whereby the liquid refrigerant is vaporized. When the liquid refrigerant is to be stored in the second liquid receiver  130 , the shut-off valve  140  is opened to permit the refrigerant vapor in the first liquid receiver  40  to be liquefied by the heat exchanger  120 , and the resulting liquid refrigerant is stored in the second liquid receiver  130 . And the liquid refrigerant in the second liquid receiver  130  is communicated to the compressor suction side through the capillary  180 . However, the capillary  180  is made high in resistance so as to make the liquid accumulate in the second liquid receiver  130 . Also, when the shut-off valve  140  is opened, the low boiling point refrigerant is returned to the high pressure side through the compressor  10 , so that the refrigerant present in a path from the first liquid receiver to the compressor suction side and including an evaporator becomes rich in the high boiling point refrigerant. Therefore, the vaporizing pressure decreases and an amount of the refrigerant circulating in the refrigeration cycle decreases, whereby the capacity of the cycle can be further decreased.  
         [0031]    [0031]FIG. 5 shows a still another embodiment. In contrast to the embodiment shown in FIG. 4, a pipe for providing communication between the liquid in the first liquid receiver  40  and the liquid in the second liquid receiver  130  is provided with a shut-off valve  190  for communication. In the above-described embodiments shown in FIGS.  1  to  4 , since the refrigerant preserved in the second liquid receiver  130  varies greatly in amount, the first liquid receiver  40  must be enlarged by a magnitude conformed to the varying amount of the refrigerant. In this embodiment, when no change is to be made in composition, the shut-off valve  190  is opened to permit a surplus refrigerant to be accumulated in both of the first liquid receiver  40  and the second liquid receiver  130 , so that the first liquid receiver  40  need not be enlarged and so can be advantageously made small-sized.  
         [0032]    Also, when some change is to be made in composition, the shut-off valve  190  is closed to prevent the liquid refrigerants in the first liquid receiver  40  and the second liquid receiver  130  from mixing with each other, so that the refrigerant can be made variable in composition.  
         [0033]    [0033]FIG. 6 shows still another embodiment, in which a check valve  170  is provided on the pipe  110  to prevent any couterflow, and the refrigerant in the second liquid receiver  130  is caused to make heat exchange with the outside air even when the outside air is high in temperature, the liquid refrigerant therein being made to vaporize, whereby it is possible to prevent the low boiling point refrigerant from returning to the first liquid receiver  40 . Al-so, the check valve may be replaced by a shut-off valve.  
         [0034]    [0034]FIG. 7 shows still another embodiment, which is a system having a plurality of indoor units B and an expansion valve in the outdoor unit A. Since the provision of the plurality of indoor units involves a large fluctuation in load, it is desirable to further increase a range of capacity control. A further increased range of capacity control can be obtained not only by using an inverter to make the rotational speed of the compressor  10  variable, but also by making the refrigerant circulating in the refrigeration cycle variable in composition.  
         [0035]    Further, while the second liquid receiver is provided to store therein a refrigerant, in which the low boiling point refrigerant is rich, in the above-described embodiments, piping may be made to substantially store the refrigerant therein.