The present disclosure relates to refrigeration. More particularly, it relates to ejector refrigeration systems.
Earlier proposals for ejector refrigeration systems are found in U.S. Pat. Nos. 1,836,318 and 3,277,660.
From the separator, the flowpath branches into a first branch 61 completing the primary loop 60 to return to the compressor and a second branch 63 forming a portion of a secondary loop 62. The secondary loop 62 of the refrigerant circuit 27 includes a heat exchanger 64 (in a normal operational mode being a heat absorption heat exchanger (e.g., evaporator)). The evaporator 64 includes an inlet 66 and an outlet 68 along the secondary loop 62. An expansion device 70 is positioned in a line 72 which extends between the separator liquid outlet 52 and the evaporator inlet 66. An ejector secondary inlet line 74 extends from the evaporator outlet 68 to the ejector secondary inlet 42.
In the normal mode of operation, gaseous refrigerant is drawn by the compressor 22 through the suction line 56 and inlet 24 and compressed and discharged from the discharge port 26 into the discharge line 28. In the heat rejection heat exchanger, the refrigerant loses/rejects heat to a heat transfer fluid (e.g., fan-forced air or water or other fluid). Cooled refrigerant exits the heat rejection heat exchanger via the outlet 34 and enters the ejector primary inlet 40 via the line 36.
The exemplary ejector 38 (
Use of an ejector serves to recover pressure/work. Work recovered from the expansion process is used to compress the gaseous refrigerant prior to entering the compressor. Accordingly, the pressure ratio of the compressor (and thus the power consumption) may be reduced for a given desired evaporator pressure. The quality of refrigerant entering the evaporator may also be reduced. Thus, the refrigeration effect per unit mass flow may be increased (relative to the non-ejector system). The distribution of fluid entering the evaporator is improved (thereby improving evaporator performance). Because the evaporator does not directly feed the compressor, the evaporator is not required to produce superheated refrigerant outflow. The use of an ejector cycle may thus allow reduction or elimination of the superheated zone of the evaporator. This may allow the evaporator to operate in a two-phase state which provides a higher heat transfer performance (e.g., facilitating reduction in the evaporator size for a given capability).
The exemplary ejector may be a fixed geometry ejector or may be a controllable ejector.
A further variation is shown in Ozaki et al. JP2003-074992A, published Mar. 12, 2003. Ozaki et al shows a bypass flowpath from upstream of the motive nozzle to downstream of the expansion device. An alternative bypass destination is to the separator in the absence of an expansion device.
One aspect of the disclosure involves a vapor compression system comprising: a compressor; a first heat exchanger; a second heat exchanger; an ejector comprising; a separator; and an expansion device. The ejector comprises: a motive flow inlet; a secondary flow inlet; and an outlet. The separator has: an inlet; a liquid outlet; and a vapor outlet.
A plurality of conduits are positioned to define a first flowpath sequentially through: the compressor; the first heat exchanger; the ejector from the motive flow inlet through the ejector outlet; and the separator, and then branching into: a first branch returning to the compressor; and a second branch passing through the expansion device and second heat exchanger to the secondary flow inlet. The plurality of conduits are positioned to define a bypass flowpath bypassing the motive nozzle and rejoining the first flowpath at essentially separator pressure but away from the separator.
In one or more embodiments of the other embodiments, the plurality of conduits are positioned so that the bypass flowpath rejoins the first flowpath upstream of the separator inlet.
In one or more embodiments of the other embodiments, the plurality of conduits are positioned so that the bypass flowpath rejoins the first flowpath upstream of the separator inlet by at a distance equal to four times to one hundred times an effective diameter of a flowpath entering the separator.
In one or more embodiments of the other embodiments, the plurality of conduits are positioned so that the bypass flowpath rejoins the second branch downstream of the separator liquid outlet and upstream of the expansion device.
In one or more embodiments of the other embodiments, the plurality of conduits are positioned so that the bypass flowpath rejoins the first branch downstream of the separator vapor outlet and upstream of the compressor inlet.
In one or more embodiments of the other embodiments, the ejector comprises a control needle movable between a first position and a second position.
In one or more embodiments of the other embodiments, a pressure regulator is disposed along the bypass flowpath.
In one or more embodiments of the other embodiments, the pressure regulator is a variable orifice expansion valve.
In one or more embodiments of the other embodiments, a variable orifice electronic expansion valve is disposed along the bypass flowpath.
In one or more embodiments of the other embodiments, a bistatic on-off valve is disposed along the bypass flowpath.
In one or more embodiments of the other embodiments, a controller is configured over at least a portion of an operating regime for pulse width modulated operation of the bistatic on-off valve.
In one or more embodiments of the other embodiments, a controller is configured to, over at least a portion of an operating regime: with increasing total flow through the heat rejection heat exchanger, increasing a fraction of the total flow passed along the bypass flowpath.
In one or more embodiments of the other embodiments, the controller is configured to: over said portion, increase the flow along the bypass flowpath responsive to increased high side pressure.
In one or more embodiments of the other embodiments, the controller is configured to: over said portion, increase a fraction of the total flow passed along the bypass flowpath so as to reduce a compressor temperature.
In one or more embodiments of the other embodiments, a refrigerant charge comprises at least 50% by weight carbon dioxide.
Another aspect of the disclosure involves a method for operating the vapor compression system. The method comprises, over at least a portion of an operating regime: with increasing total flow through the heat rejection heat exchanger, increasing a fraction of the total flow passed along the bypass flowpath.
In one or more embodiments of the other embodiments, the increasing the fraction of the total flow passed along the bypass flowpath is responsive to increased sensed high side pressure.
In one or more embodiments of the other embodiments, a method for operating the vapor compression system comprises, over at least a portion of an operating regime: increasing a fraction of the total flow passed along the bypass flowpath so as to reduce a compressor temperature.
In one or more embodiments of the other embodiments, the increasing the fraction of the total flow passed along the bypass flowpath is responsive to increased sensed compressor discharge temperature.
The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
Like reference numbers and designations in the various drawings indicate like elements.
In some examples, the replacement ejector can have a motive nozzle cross-sectional area of 40% to 90% that of the baseline ejector, for example, 50% to 80%, or 70%. Addition of the bypass flowpath allows unloading the ejector if needed. For example, reasons for unloading the ejector can include relieving pressure of the high side components when the pressure relieved by fully withdrawing the control needle is insufficient (e.g., to prevent damage of the heat rejection heat exchanger), increasing efficiency (e.g., in some cases a more efficient operation of the ejector may occur with some bypass), or a combination including at least one of the foregoing.
In the illustrated embodiment, the bypass flowpath comprises a bypass line 204 extending from a first location 204 upstream of the motive nozzle along the primary flowpath/loop 60 to a second location 208. In the illustrated embodiment, the second location 208 is also along the primary loop/flowpath 60. More particularly, the exemplary location 208 is between the ejector outlet 44 and separator inlet 50.
A flow control device 210 is positioned to control flow along the bypass flowpath 200. Exemplary flow control devices include a valve (e.g., an electronically controlled valve), a mass flow controller, a pressure regulator, a flow orifice, or a combination including at least one of the foregoing. One example of an electronically controlled valve is a pulse width modulated (PWM) valve (e.g., on-off solenoid valve) under control of the controller 140. Exemplary pressure regulators are variable valves. Examples of such valves may be directly controlled via a pressure and/or a temperature sensor. For example, there may be direct control responsive to a pressure sensor 164 or 166 at the heat exchanger 30 or 64. If at the heat exchanger 30, the valve may be set up so that pressure increase causes corresponding increase in valve opening area to relieve that pressure at the heat rejection heat exchanger 30. If at the evaporator 64, control may be inverted. Namely, a decrease in pressure at the evaporator 64 may cause an opening of the valve 210. This may be useful to cause an increase in refrigerant flow delivered to the evaporator 64 and thus may cause an increase in evaporator temperature to avoid freezing while also reducing the pressure at the heat rejection heat exchanger 30. Other variable valves are pulse width modulated valves which may be controlled by the controller as noted above responsive to input from sensors at locations such as the heat exchangers.
A yet further variation might involve a non-PWM bi-static on-off valve. However, in some cases such embodiments may limit flexibility to control the refrigerant system (e.g., pressure and/or temperatures at selected regions of the system) which may be undesirable.
Numerous control variations are possible. For example, in reengineering a baseline system, control of the bypass may piggy back on some other control aspect. For example the baseline system's programming may include control of compressor speed. The bypass may be controlled directly as a function of compressor speed (and thus indirectly as a function of whatever parameters were used by the controller to determine that speed).
Relative to the Ozaki et al. embodiment bypassing to the separator, embodiments of the
In certain embodiments, the bypass and main flow may mix in a Y-fitting 250 (
Control may be otherwise similar to that mentioned above for
Relative to the Ozaki et al. embodiment bypassing to the separator, embodiments of the
Control may be otherwise similar to that mentioned above for
Some portion of the bypass refrigerant in
Other potential advantages of the
The controller may be programmed for allowing bypass to limit compressor temperature. This control may be in addition to control as discussed for the other systems. Control may be in response to a directly sensed temperature or a calculated temperature or a proxy thereof. For example, a discharge temperature sensor 152 may be coupled to the controller to provide discharge temperature data. Alternatively, the controller may be programmed to infer discharge temperature from other measurements (e.g., discharge and suction pressures from respective sensors 160 and 162 and suction temperature from sensor 150). The controller may be programmed to bypass refrigerant sufficiently to keep temperature at or below a threshold value. The threshold may be a set parameter, or the controller may be programmed to calculate a particular threshold for particular operating conditions. In one example of combined control, the controller may be programmed to bypass refrigerant if either the ejector flow or load exceeds a threshold (e.g., a pressure at the ejector (may be effectively measured by sensor 164 or a sensor closer to the ejector) or pressure difference across the ejector (e.g., may be measured between sensors 164 and 160 or sensors closer to the ejector) exceeds a threshold) or the compressor temperature (e.g., a discharge temperature from sensor 152) exceeds its threshold.
The
The use of “first”, “second”, and the like in the description and following claims is for differentiation within the claim only and does not necessarily indicate relative or absolute importance or temporal order. Similarly, the identification in a claim of one element as “first” (or the like) does not preclude such “first” element from identifying an element that is referred to as “second” (or the like) in another claim or in the description.
Where a measure is given in English units followed by a parenthetical containing SI or other units, the parenthetical's units are a conversion and should not imply a degree of precision not found in the English units.
One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when applied to an existing basic system, details of such configuration or its associated use may influence details of particular implementations. Other variations common to vapor compression systems may also be implemented such as suction line heat exchangers, economizers, and the like. Systems having additional compressors, heat exchangers, or the like may also be implemented. Accordingly, other embodiments are within the scope of the following claims.
Number | Date | Country | Kind |
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2015 1 0276827 | May 2015 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/US2016/034296 | 5/26/2016 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2016/191541 | 12/1/2016 | WO | A |
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