Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2001-01-05
2001-12-11
Tapolcai, William E. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S129000
Reexamination Certificate
active
06327868
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a freezing cycle in which a coolant compressed by a compressor reaches a point equal to or higher than the critical point, having a structure for protecting the various components employed in the freezing cycle when the level of the high-side pressure becomes abnormally high.
BACKGROUND ART
Among the supercritical coolants such as ethylene (C2H4), diborane (B2H6), ethane (C2H5), nitrogen oxide (N2O) and carbon dioxide (CO2) that may be used in the supercritical steam compression cycle disclosed in Japanese Examined Patent Publication No. H 7-18602 comprising, at least, a compressor, the cooling device, a means for constriction and an evaporator, carbon dioxide (CO2) is the primary coolant that is mainly utilized.
This supercritical steam compression cycle is one of the non-freon freezing cycle proposed as replacements for freon freezing cycles, and freezing cycles that use carbon dioxide in particular, are considered promising replacements for freon freezing cycles.
However, since carbon dioxide has a low critical point of approximately 31.1° C., the external air temperature may exceed the critical point, especially during summer. In addition, during a freezing cycle operation, too, the high-pressure line (extending from the compressor to the means for constriction) in the freezing cycle naturally constitutes a supercritical area, and the pressure in the supercritical area where the temperature exceeds the critical point, which is determined by the density and the temperature, may exceed 20 MPa if the temperature is very high.
As described above, while it is necessary to ensure that all the components conform to specifications for withstanding super-high pressures in the freezing cycle in which the operating pressure is extremely high compared to that in a freon freezing cycle, there is a problem in that an improvement in the pressure withstanding performance will result in increases in the weight and production cost of the product. In other words, while it is desirable to use aluminum to constitute the components to achieve a reduction in the weight, the operating pressure in a heat exchanger or the like, in particular, cannot exceed 20 MPa at present in consideration of the pressure withstanding performance determined in conjunction with the heat exchanging capability and the strength.
Accordingly, a safety mechanism that discharges the coolant into the atmosphere when the high-side pressure exceeds a specific level may be provided. However, there is a problem in that the coolant released into the atmosphere must be replenished.
Addressing the problems discussed above, an object of the present invention is to provide a freezing cycle in which the high-side pressure can be reduced without having to release the coolant into the atmosphere in the event of a high-side pressure abnormality and the coolant is released into the atmosphere only in the event of a low-side pressure abnormality.
SUMMARY OF THE INVENTION
Accordingly, the freezing cycle according to the present invention, which comprises, at least, a compressor that compresses a gas-phase coolant to achieve a supercritical pressure, a radiator that cools the gas-phase coolant compressed by the compressor, a means for constriction that lowers the pressure of the cooled gas-phase coolant down to a range in which liquid-phase coolant is present and an evaporator that evaporates the liquid-phase coolant obtained through the means for constriction, having a high-pressure line extending from the compressor to the means for constriction and a low-pressure line extending from the means for constriction to the compressor, is further provided with a first means for safety that communicates between the high-pressure line and the low-pressure line if the pressure in the high-pressure line reaches a first pressure and a second means for safety provided at the low-pressure line, that opens the low-pressure line to the atmosphere if the pressure in the low-pressure line reaches a second pressure.
Thus, according to the present invention, in which the first means for safety is provided between the high-pressure line and the low-pressure line to leak the high-pressure coolant in the high-pressure line toward the low-pressure side by opening a first valve if an abnormality occurs in the freezing cycle and the high-side pressure reaches a level equal to or higher than the first pressure, the increase in the pressure in the high-pressure line is absorbed in the low-pressure line to reduce the pressure in the high-pressure line, thus preventing the high-side pressure from rising without having to release the coolant. In addition, the coolant is released into the atmosphere by the second means for safety only if the pressure in the low-pressure line reaches a level equal to or higher than the second pressure due to an abnormal increase in the pressure in the low-pressure line caused by an inflow of a high-side pressure from the high-pressure line or an abnormality in the freezing cycle itself, since the safety of the individual components in the low-pressure line will no longer be assured. Consequently, since if the release of coolant from the freezing cycle is minimized, wasteful loss of coolant is prevented.
In addition, the freezing cycle further comprises a first heat exchanger located between the radiator and the means for constriction and a second heat exchanger located between the evaporator and the compressor, and is also provided with an internal heat exchanger which engages in heat exchange between the first heat exchanger and the second heat exchanger, with the first means for safety provided between the first heat exchanger and the second heat exchanger and the second means for safety provided between the second heat exchanger and the atmosphere.
Furthermore, the second means for safety may be provided inside the compressor to open the intake side of the compressor to the atmosphere if the pressure on the intake side of the compressor reaches the second pressure, or the first means for safety may be provided inside the compressor to communicate between the outlet side and the intake side of the compressor if the pressure on the outlet side of the compressor reaches a level equal to or higher than the first pressure.
Alternatively, in a freezing cycle which comprises, at least, a compressor that compresses a gas-phase coolant to achieve a supercritical pressure, a radiator that cools the gas-phase coolant having been compressed by the compressor, a means for oil separation that is provided on the downstream side relative to the radiator and separates oil from the cooled coolant, a first means for constriction that lowers the pressure of the gas-phase coolant having undergone the oil separation at the means for oil separation down to a range in which a liquid-phase coolant is present, a means for gas/liquid separation that separates the coolant that has been set in a gas/liquid mixed state by the first means for constriction into a gas-phase component and a liquid-phase component, a second means for constriction that further reduces the pressure of the liquid-phase coolant resulting from the separation at the means for gas/liquid separation and an evaporator that evaporates the liquid-phase coolant with its pressure having been lowered by the second means for constriction, having a high-pressure line extending from the compressor to the first means for constriction, an intermediate-pressure line extending from the first means for constriction to the second means for constriction and a low-pressure line extending from the second means for constriction to the compressor, the first means for safety is provided between the means for oil separation and the means for gas/liquid separation to communicate between the high-pressure line and the intermediate-pressure line at the first pressure and the second means for safety is provided between the means for gas/liquid separation and the atmosphere to communicate between the intermediate-pressure line and the atmosphere when the pressure reach
Furuya Shunichi
Tanda Kiyoshi
Ali Mohammad M.
Tapolcai William E.
Wenderoth , Lind & Ponack, L.L.P.
Zexel Valeo Climate Control Corporation
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