COOLING SYSTEM WITH MULTIPLE STEAM JECTORS CONNECTED TO MULTIPLE FLOW DROPPERS

Description

[0001] The invention relates to refrigeration systems and more specifically to a refrigeration system that includes a steam ejector and a flow trap.

[0002] Commercial refrigeration systems (CRSs) represent a significant part of a power load in super markets. Steam ejectors are convergent-divergent devices that provide a pressure lift without requiring power and thereby are used to increase CRS efficiency. In order to satisfy different load conditions, parallel multi-ejectors configurations (with a same or different sizes) may be installed in a CRS. However, when multiple ejectors operate at the same time, there may be risks of unstable operations, for example, reverse flow (RF), due to different operating characteristics and output capacities among the ejectors. JP H10 89814 A discloses a refrigeration system according to the preamble of claim 1.

[0003] The present invention which is defined in claim 1 provides a refrigeration system comprising: a steam ejector with an ejector outlet; and a passive flow trap connected to the ejector outlet. The passive flow trap includes an inlet-side drop, a center bend, and an outlet-side rise, thereby defining a U shape, and the inlet-side drop is larger than the outlet-side rise.

[0004] The system may include a separator connected to an outlet-side of the passive flow trap.

[0005] Optionally, the passive flow trap is connected to a lower portion of the separator that is configured to store liquid refrigerant.

[0006] Optionally, the system comprises one or more additional steam ejectors, each of which including one of one or more additional ejector outlets; and one or more additional passive flow traps, one of which connected to each of the one or more additional ejector outlets.

[0007] Each of the one or more additional passive flow traps may include an inlet-side drop, a center bend, and an outlet-side rise, thereby defining a U shape.

[0008] For at least two of the passive flow trap and one or more additional passive flow traps, the outlet-side rise may be the same.

[0009] For each of the passive flow trap and one or more additional passive flow traps, the outlet-side rise may be the same.

[0010] For each of the passive flow trap and one or more additional passive flow traps, the outlet-side rise may be different.

[0011] Optionally, the system includes a separator connected to an outlet-side of each of the passive flow trap and one or more additional passive flow traps.

[0012] The passive flow trap and one or more additional passive flow traps may be connected to a lower portion of the separator that is configured to store liquid refrigerant.

[0013] The system may include an evaporator, wherein each of the steam ejector and one or more additional steam ejectors includes one of a plurality of ejector first-inlets, each of the plurality of ejector first-inlets is connected to the evaporator.

[0014] The system may include a plurality of shut-off valves, wherein each of a plurality of shut off valves is connected between the evaporator and one of the plurality of ejector first-inlets.

[0015] The separator may include a first outlet connected to an expansion device.

[0016] Optionally, the system includes a gas cooler, wherein each of the steam ejector and one or more additional steam ejectors includes one of a plurality of ejector second-inlets, each of the plurality of ejector second-inlets is connected to the gas cooler.

[0017] The system may include a compressor, wherein the separator includes a second outlet connected to the compressor.

[0018] A second aspect of the invention provides a method of directing flow in a refrigerant system comprising: directing a two phase flow from each of a plurality of steam ejectors into one of a plurality of passive flow traps; directing the two phase flow from each of the plurality of passive flow traps into a separator; and preventing backflow from the separator from reaching each of the plurality of steam ejectors with one of the plurality of passive flow traps. Each of the plurality of passive flow traps includes an inlet-side drop, a center bend, and an outlet-side rise, thereby defining a U shape, and for at least one of the plurality of passive flow traps, the inlet-side drop is larger than the outlet-side rise.

[0019] .

[0020] The present invention is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements. FIG. 1 is a schematic illustration of a refrigerant system according to an embodiment of the present invention; and FIG. 2 is a flow diagram showing a process of directing flow in a refrigerant system according to an embodiment.

[0021] Turning to FIG. 1, the disclosed embodiments provide a configuration for a refrigeration system (system) 100 with a plurality of steam ejectors 110, wherein backflow from a separator 125 may be minimized. The plurality of steam ejectors 110 are illustrated as including three ejectors 110a-110c each with one of a plurality of ejector outlets 115 so that three outlets 115a-115c are illustrated. Each of the ejector outlets 115 is connected to one of a plurality of passive flow traps 118 so that three passive flow traps 118a-118c are illustrated. Though sets of three features are illustrated and disclosed herein, such as three steam ejectors 110 and passive flow traps 118, the disclosure is not intended to limit the scope of a number of features that may fall within the scope of the invention and appended claims.

[0022] Each of the passive flow traps 118 includes an inlet-side drop (relative to gravity) 120, a center bend 122 and an outlet-side rise (relative to gravity) 124 so as to define a U shape. Accordingly, three inlet-side drops 120a-120c, three center bends 122a-122c and three outlet-side rises 124a-124c are illustrated. A separator 125 is connected the outlet-side rise 124 of each of the passive flow traps 118. More specifically, the passive flow traps 118 are connected to a lower portion 130 of the separator 125 that normally contains accumulated liquid refrigerant 135.

[0023] A height span of each of the outlet-side rises 124a-124c can be a same distance or a different distance for each of the plurality of steam ejectors 110. There will typically be at least some liquid stored in one of the passive flow traps 118 if outlet pressure of the respective one of the steam ejectors 110 is lower than pressure at the separator 125. Such fluid in the traps 118 prevents backflow. That is, in such situation, the passive flow traps 118 each functions as a pressure buffer to avoid reverse flow from the separator 125. According to hydrostatic pressure theory, the static pressure provided by the U-shape could be estimated by p=ρgh, where ρ, g and h are density of liquid refrigerant, gravitational constant and height of outlet-side rise, respectively. As long as the pressure difference between ejector outlet and separator is lower than this value, the reverse flow may be avoided.

[0024] As further illustrated, the system 100 includes an expansion device and an evaporator 140, illustrated schematically. Each of the plurality of steam ejectors 110 includes one of a plurality of ejector first-inlets 145 so that three of the ejector first-inlets 145a-145c are illustrated. Each of the ejector first-inlets 145 is connected to the evaporator 140. Further, each of a plurality of shut-off valves 150 is connected between the evaporator 140 and one of the ejector first-inlets 145, so that three shut-off valves 150a-150c are illustrated.

[0025] The system further includes a gas cooler 155 illustrated schematically. Each of the plurality of steam ejectors 110 includes one of a plurality of ejector second-inlets 160 so that three of the ejector second-inlets 160a-160c are illustrated. Each of the ejector second-inlets 160 is connected to the gas cooler 155. The separator 125 includes a first outlet 170 connected to the evaporator and a second outlet 175 connected to a compressor 180 of the system 100.

[0026] Turning to FIG. 2, a method is shown in a flow chart of directing flow in the system 100. As illustrated in block 510, the method includes directing a two phase flow from each of a plurality of steam ejectors 110 into one of a plurality of passive flow traps 118. As illustrated in block 520, the method includes directing the two phase flow from each of the plurality of passive flow traps 118 into a separator 125. As illustrated in block 530, the method includes preventing separator backflow from reaching each of the plurality of steam ejectors 110 with one of the plurality of passive flow traps 118.

[0027] The above disclosed embodiments provide a system 100 that mitigates a possibility of reverse flow from the separator 125 to the plurality of steam ejectors 110. The system 100 may increase an operating efficiency associated with utilizing a multi-ejector configuration while minimizing a risk of reverse flow.

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and / or groups thereof.

[0029] Those of skill in the art will appreciate that various example embodiments are shown and described herein, each having certain features in the particular embodiments, but the present invention is not thus limited. While various embodiments of the present invention have been described, it is to be understood that aspects of the present invention may include only some of the described embodiments. Accordingly, the present invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Claims

1. A refrigeration system (100) comprising: a steam ejector (110) with an ejector outlet (115); and a passive flow trap (118) connected to the ejector outlet (115), wherein the passive flow trap (118) includes an inlet-side drop (120), a center bend (122), and an outlet-side rise (124), thereby defining a U shape, characterised in that the inlet-side drop (120) is larger than the outlet-side rise (124).

2. The system of claim 1, comprising a separator (125) connected to an outlet-side of the passive flow trap (118).

3. The system of claim 2, wherein the passive flow trap (118) is connected to a lower portion of the separator (125) that is configured to store liquid refrigerant (135).

4. The system of claim 1, further comprising: one or more additional steam ejectors (110), each of which including one of one or more additional ejector outlets (115); and one or more additional passive flow traps (118), one of which connected to each of the one or more additional ejector outlets (115).

5. The system of claim 4, wherein each of the one or more additional passive flow traps (118) includes an inlet-side drop (120), a center bend (122), and an outlet-side rise (124), thereby defining a U shape.

6. The system of claim 5, wherein for at least two of the passive flow trap (118) and one or more additional passive flow traps (118), the outlet-side rise (124) is the same.

7. The system of claim 5, wherein for each of the passive flow trap (118) and one or more additional passive flow traps (118), the outlet-side rise is the same (124).

8. The system of claim 5, wherein for each of the passive flow trap (118) and one or more additional passive flow traps (118), the outlet-side rise (124) is different.

9. The system of claim 5, comprising a separator (125) connected to an outlet-side of each of the passive flow trap (118) and one or more additional passive flow traps (118), optionally wherein the passive flow trap (118) and one or more additional passive flow traps (118) are connected to a lower portion of the separator (125) that is configured to store liquid refrigerant (135).

10. The system of claim 9, including an evaporator (140), wherein each of the steam ejector (110) and one or more additional steam ejectors (110) includes one of a plurality of ejector first-inlets (145), each of the plurality of ejector first-inlets is connected to the evaporator (140).

11. The system of claim 10, including a plurality of shut-off valves (150), wherein each of a plurality of shut off valves is connected between the evaporator (140) and one of the plurality of ejector first-inlets (145).

12. The system of claim 11, wherein the separator (125) includes a first outlet (170) connected to an expansion device.

13. The system of claim 12, including a gas cooler (155), wherein each of the steam ejector (110) and one or more additional steam ejectors (110) includes one of a plurality of ejector second-inlets (160), each of the plurality of ejector second-inlets is connected to the gas cooler (155).

14. The system of claim 13, including a compressor (180), wherein the separator (125) includes a second outlet (175) connected to the compressor (180).

15. A method of directing flow in a refrigerant system comprising: directing a two phase flow from each of a plurality of steam ejectors (110) into one of a plurality of passive flow traps (118); directing the two phase flow from each of the plurality of passive flow traps (118) into a separator (125); and preventing backflow from the separator (125) from reaching each of the plurality of steam ejectors (110) with one of the plurality of passive flow traps (118), wherein each of the plurality of passive flow traps (118) includes an inlet-side drop (120), a center bend (122), and an outlet-side rise (124), thereby defining a U shape, and for at least one of the plurality of passive flow traps (118), the inlet-side drop (122) is larger than the outlet-side rise (124).