EP2859242A1

EP2859242A1 - An ejector

Info

Publication number: EP2859242A1
Application number: EP13803928.4A
Authority: EP
Inventors: Michael Dennis
Original assignee: Endless Solar Corp Ltd
Current assignee: Endless Solar Corp Ltd
Priority date: 2012-06-12
Filing date: 2013-04-16
Publication date: 2015-04-15
Also published as: IN2014MN02493A; CN104379941A; EP2859242A4; WO2013185164A1; US20150152885A1; BR112014030967A2; JP2015521703A; AU2013273913A1

Abstract

The present disclosure provides an ejector that comprises a housing portion and first and second fluid inlets. The ejector further comprises a fluid outlet and a fluid nozzle that is positioned in the housing and coupled to the first fluid inlet. The fluid nozzle is arranged such that a first fluid that is received by the first inlet at a first pressure PI has a second pressure P2 after passing through the fluid nozzle. The pressure P2 lower that the pressure PI. The ejector also comprises a mixing region that is arranged such that the first fluid when passing through the mixing region draws a second fluid from the second fluid inlet such that the first and second fluids mix. The ejector has an ejector diffuser region that has a cross-sectional area that increases in diameter in a direction towards the fluid outlet and is arranged such that the mixture of the first and second fluid exits the ejector through the fluid outlet with a third pressure. The ejector is arranged such that a position of an outlet of the fluid nozzle relative to the mixing region is adjusted dependent on PI, P2 and/or P3.

Description

AN EJECTOR

Field of the Invention

The present invention relates to an ejector, such as an ejector for a solar cooling system.

Background of the Invention

The operation of conventional cooling systems, such as air conditioning and refrigeration units, requires a

considerable amount of electrical energy. The electrical energy is often generated using power stations that burn fossil fuel and consequently emit undesirable pollutants and greenhouse gases.

Photovoltaic solar panels may be used to convert sunlight into electrical energy that can be used to operate an electric motor that drives a gas compressor of a cooling system. This may reduce the need for fossil fuels, but the efficiency is relatively low and the capital cost is relatively high.

Cooling systems that are operated using thermal solar energy and have ejectors instead of corresponding

conventional electrical components are an alternative. However, an ejector is designed for predetermined

operation conditions (such as temperatures and pressures of fluids) at which the ejector operates most efficiently. Consequently, the ejector efficiency is reduced if the ejector is not operated at the predetermined operation conditions . Summary of the Invention The present invention provides in a first aspect an ejector comprising:

a housing portion;

a first fluid inlet and a second fluid inlet;

a fluid nozzle positioned in the housing portion and coupled to the first fluid inlet, the fluid nozzle being arranged such that a first fluid that has a fluid inlet pressure PI and is received by the first fluid inlet has a fluid nozzle exit pressure after passing through the fluid nozzle, the fluid nozzle exit pressure being lower than PI;

a mixing region arranged such that the first fluid when passing through the mixing region draws a second fluid from the second fluid inlet such that the first and second fluids mix; and

a fluid outlet through which a mixture of the first and second fluids exits the ejector;

wherein the ejector is arranged such that a position of an outlet of the fluid nozzle relative to the mixing region is adjusted dependent on PI and/or a pressure of the mixed first and second fluids.

The ejector may be arranged such that a position of the outlet of the fluid nozzle relative to the mixing region is self-adjusted dependent on PI and/or a pressure of the mixed first and second fluids. For example, the ejector may comprise a passive structure that is arranged for self-adjusting of the position of the outlet of the fluid nozzle. Alternatively, the ejector may also comprise an actuator that is arranged to adjust a position of the outlet of the fluid nozzle dependent on PI and/or a pressure of the mixed first and second fluids.

In one specific embodiment the ejector is arranged such that the first fluid has a second pressure P2 after passing through the fluid nozzle, P2 being lower than PI, and the mixture of the first and second fluid exits the ejector with a third pressure P3;

wherein the ejector is arranged such that the position of the outlet of the fluid nozzle relative to the mixing region is adjusted dependent on PI, P2 and/or P3. The ejector typically comprises an ejector diffuser having an interior portion with a cross-sectional area that increases in diameter in a direction towards the fluid outlet and is arranged such that the mixture of the first and second fluid exits the ejector through the fluid outlet with the third pressure P3.

The ejector may comprise a converging region that is provided in addition to the mixing region and that is positioned such that the mixed first and second fluids converge before exiting the ejector, the converging region having a cross-sectional area that reduces in diameter in a direction towards the outlet of the ejector.

Alternatively, the mixing region may be provided in the form of a converging region and may be arranged such that the first and second fluids converge during or after mixing and before exiting the ejector, the converging region having a cross-sectional area that reduces in diameter in a direction towards the outlet of the ejector.

The ejector is typically arranged such that the outlet of the fluid nozzle, and typically the entire fluid nozzle, moves towards or away from the converging region if the pressure of the mixed first and second fluids (such as P2 or P3) changes relative to another pressure within the ejector .

The ejector is typically arranged such that the outlet of the fluid nozzle, and typically the entire fluid nozzle, moves away from the converging region if P2 increases and towards or into the converging region of P3 increases .

Embodiments of the present invention have significant practical advantages. An ideal position of the fluid nozzle is dependent on PI, P2 and/or P3. Consequently, the adjusting of the relative position of the fluid nozzle may increase the ejector's efficiency.

In one embodiment a length by which the relative position of the ejector is adjusted is largely proportional to a change in pressure of the mixed first and second fluids (such as P2 or P3) relative to another pressure in the ejector .

The ejector may comprise a conduit that is arranged such that a portion at or near the fluid nozzle of the ejector has a pressure that is proportional to, or substantially equals, a pressure of the mixed first and second fluids and wherein the ejector is arranged such that that portion is isolated form unmixed first and second fluids.

In one specific embodiment the ejector comprises a conduit that is arranged such that a portion at or near the fluid nozzle of the ejector has a pressure that is proportional to, or substantially equals, the pressure P2 or P3 and wherein the ejector is arranged such that that portion is isolated form unmixed first and second fluids.

The ejector may comprise a diaphragm. The diaphragm may seal at least a portion around the fluid nozzle. The ejector may be arranged such that the fluid nozzle or a portion thereof moves until the diaphragm and/or another portion of the ejector provides a sufficient reaction force for locating the fluid nozzle in an adjusted position .

The diaphragm may surround the fluid nozzle or may alternatively only be positioned around a portion of the fluid nozzle. The diaphragm typically comprises a suitable polymeric material, such as a rubber material.

Alternatively, the ejector may comprise a moveable wall portion, such as a moveable wall portion that is rigid and may be coupled to a spring. The moveable wall portion may be coupled directly or indirectly to the fluid nozzle such that the fluid nozzle or a portion thereof moves with the moveable wall portion until the spring provides a

sufficient reaction force for locating the fluid nozzle in an adjusted position. The conduit may be arranged such that a side portion of the diaphragm or the moveable wall portion is exposed to a pressure that is proportional to, or approximately equals, the pressure of the mixed first and second fluids, wherein the ejector may be arranged such that an increase in the pressure of the mixed first and second fluids relative to another pressure within the ejector results in a movement of the nozzle or portion thereof relative to the mixing region of the ejector.

The ejector typically is arranged such that an increase in the pressure of the mixed first and second fluids relative to P3 results in a movement of the nozzle or portion thereof away from the mixing region of the ejector.

Further, the ejector typically is arranged such that an decrease in the pressure of the mixed first and second fluids relative to P3 results in a movement of the nozzle or portion thereof into or towards the mixing region of the ejector.

The present invention also provides a method of operating an ejector, the method comprising:

receiving a first fluid having a first pressure;

receiving a second fluid;

directing the first fluid through a fluid nozzle of an ejector such that the pressure of the first fluid is reduced to a second pressure that is lower than the first pressure;

drawing the second fluid such that the second fluid mixes with the first fluid in a mixing region; and

adjusting a position of an outlet of the fluid nozzle relative to the mixing region of the ejector dependent on the first, the second and/or an ejector exit pressure.

The step of adjusting a position of an outlet of the fluid nozzle relative to the mixing region of the ejector may comprise self-adjusting a position of an outlet of the fluid nozzle.

The mixing region may comprise, or may be provided in the form of, the converging region.

The invention will be more fully understood from the following description of specific embodiments of the invention. The description is provided with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 shows a schematic cross-sectional representation of an ejector in accordance with an embodiment of the present invention;

Figures 2 and 3 show perspective side views of the ejector in accordance with an embodiment of the present invention;

Figure 4 is a flow chart illustrating a method of

operating an ejector in accordance with an embodiment of the present invention; and

Figure 5 illustrates the operation of a heat pump

including the ejector in accordance with a specific embodiment of the present invention.

Detailed Description of Specific Embodiments Referring initially to Figure 1 to 3, an ejector 100 in accordance with an embodiment of the present invention is now described. The ejector 100 may be operated to drive a heat pump of a refrigeration cycle, in which case the ejector 100 may be used in place of a conventional electric compressor, which will be described in more details further below with reference to Figure 5.

The ejector 100 has a body 102 that is generally

cylindrical. The body 102 comprises a nozzle housing 104 and a diffuser portion 106. A fluid nozzle 108 is

positioned in the nozzle housing 104. The body 102 also comprises a mixing region that is provided in the form of a converging region 110 and has a cross-sectional area that reduces in a direction away from the nozzle 108 and along an axis of the ejector 100. The diffuser portion 106 further comprises a diverging region 118 that has a cross- sectional area that increases in a direction away from the nozzle 108 and along an axis of the ejector 100. The ejector 100 has a first inlet 114 for receiving a first fluid such as a refrigerant. Further, the ejector 100 has a second inlet 116 for receiving a second fluid that may also be a refrigerant. However, a person skilled in the art will appreciate that the first and second fluids may be of various different types. For example, the first and/or the second fluids may alternatively be air, water, water vapour or refrigerant vapour or any other suitable fluid. The first fluid 114 has a pressure PI before penetrating through the nozzle 108. The nozzle 108 has a diverging region 109 through which the first fluid exits the nozzle 108 and that results in an expansion of the first fluid, which further expands a converging region 110 in which it has a reduced pressure P2 (and the velocity of the first fluid is increased) . In operation of the ejector 100 the pressure P2 is sufficiently low such that the second fluid is drawn through the second inlet

116 into the mixing region of the converging region 110 to mix with the first fluid. The mixture of the first and second fluids penetrates through the converging region 110, a cylindrical region 112, the diffusing region 118 and then exits the ejector 100 with a pressure P3.

Consequently, the ejector 100 functions as a pump or compressor that increases the pressure of the second fluid.

The efficiency with which the ejector 100 pumps the second fluid depends on various operation parameters including the differences between the pressures PI, P2 and P3 for a given design of the ejector 100. For example, for larger P3 relative to PI, the nozzle 108 should be positioned further within the converging region 110 than for smaller P3.

The nozzle 108 is movable along an axis of the ejector 100 such that positioning of the nozzle 108 as a function of P3, P2 and PI is possible. The nozzle 108 has in this embodiment a holder 121 in which the nozzle 108 slides along the axis of the ejector 100. The ejector 100 also comprises a diaphragm 119 that surrounds the nozzle 108 and seals the nozzle 108. Further, the ejector 100 comprises a conduit 122 that connects an end-portion of the diffuser region 118 with a volume 123 behind the diaphragm 119. Consequently, the volume 123 has a pressure that is in this embodiment proportional to or is substantially equal to the pressure P3 such that the pressure within the volume 123 pushes on the diaphragm 119 and on the nozzle 108 to move the nozzle 108 to a position at which the diaphragm 119 is sufficiently expanded such that the diaphragm 119 provides a sufficient reaction force and the nozzle is located in an adjustment position. The diaphragm 119 is proportioned and arranged such that the adjustment position enables substantially ideal or at least improved operating condition dependent on P3 relative to other pressures of the ejector.

The nozzle holder 121 is provided with facility for damping the motion of the nozzle 108 such that the nozzle 108 does not change position with rapid fluctuations in pressures PI, P2 or P3. Rapid fluctuations in pressure may arise from pressure waves or shock waves in the ejector. Damping may be provided by friction within the nozzle holder 121. This friction could be provided by including a flexible ring 130 inside the nozzle holder 121.

A person skilled in the art will appreciate that the ejector 100 may alternatively be provided in different forms. For example, the diaphragm 119 may only partially surround the nozzle 108 and a remaining portion may be solid. Further, the diaphragm 119 may be positioned at another position than indicated in Figure 1. For example, the diaphragm 119 may be located further within the ejector 100 and along the nozzle 108. Further, the diaphragm 119 may be replaced with a suitable spring mechanism (including for example a compression or

expansion spring) that is arranged to provide the reaction force for locating the nozzle in an adjustment position. In this case the ejector 100 may or may not comprise the diaphragm 119 and the pressure P3 may push against a rigid wall (not shown) that is attached to the movable nozzle 108 to move the nozzle 108 until the spring mechanism provides a sufficient reaction force. In addition, the holder 116 may be provided in any suitable form or may not be present. For example, the diaphragm 119 or the rigid wall may be arranged hold the nozzle 108. Further, an end of the conduit 122 may be positioned near the outlet of the nozzle 108 in the converging region 110 or in the cylindrical region 112. Further, the ejector 100 may not necessarily comprise a converging region. For example, the mixing region may be incorporated in the diffusing region 118. In a further variation the ejector may comprise an actuator that is arranged to adjust the position of the fluid nozzle 108 as a function of PI, P2 or P3. For example, the ejector may comprise a pressure sensor that senses a change in PI, P2 or P3 and generates an output signal that is used to control the actuator.

The diaphragm 119 is formed from a suitable polymeric material that has a suitable flexibility, such as a suitable rubber or a thin metallic material.

As mentioned above, first and second fluids may for example be refrigerants, examples of which include hydrofluorocarbons , hydrocarbons, carbon dioxide, ammonia, alcohols and water.

Figure 4 illustrates a method of operating an ejector in accordance with an embodiment of the present invention. Method 400 comprises steps 402 and 404 of receiving first and second fluids. The method 400 also includes directing the first fluid through a nozzle of an ejector such that the pressure of the first fluid is reduced to a second pressure that is lower than the first pressure. The method 400 further includes drawing the second fluid such that the second fluid mixes with the first fluid that exited an outlet of the nozzle (step 408) adjusting a position of the outlet of the nozzle relative to a mixing region of the ejector dependent on the first pressure and/or the a pressure of the mixed first and second fluids to improve the efficiency of the ejector (step 410) . Step 408 may comprise self-adjusting the position of the outlet of the fluid nozzle.

Turning now to Figure 5, the operation of the ejector 100 in a heat pump refrigeration cycle is described in more detail . The heat pump refrigeration cycle 500 comprises in this example high and low temperature sub cycles (510 and 512 respectively) . In the high temperature sub cycle 510, heat that is transferred to the ejector 100 from the heat source (such as a solar collector 504) through a vapour generator 514 causing vaporisation of the ejector cycle working fluid in the generator 514 at a temperature slightly above the saturation temperature of the

refrigerant. Vapour then flows to the ejector 100 where it is accelerated (and reduced in pressure) by the nozzle of the ejector 100.

A pump 516 may be required to generate a pressure

difference for the ejector 100 to operate, but since liquid is being compressed, the power consumption is relatively small. The fluids form generator 514 and evaporator 518 then mix in the ejector 100 and the resultant fluid mixture undergoes a compression shock. Thus, thermal compression replaces the electrical compressor in a conventional heat pump. Further compression takes place in the diffusing region of the ejector 100 such that a subsonic stream emerging from the ejector 100 then flows into the

condenser 520. As a position of the outlet of the nozzle 108 of the ejector 100 is adjusted (such as self

adjusted) , the ejector 100 provides for increased

efficiency if operation pressures change.

At the condenser 520, heat is rejected from the working fluid (refrigerant) to the surroundings, resulting in a condensed refrigerant liquid at the condenser 520 exit. Liquid refrigerant leaving the condenser 520 is then divided into two streams; one enters the evaporator 518 after a pressure reduction through the expansion valve 522, the other is routed back into the generator 514 after undergoing a pressure increase through the refrigerant pump 516. The refrigerant fluid is evaporated in the evaporator 518, absorbing heat from the environment that is being cooled, and then it is entrained back into the ejector 100 completing the cycle.

There are a number of means to model the performance of an ejector. Modelling may be based on thermodynamic

compressible flow theory with minor corrections for non- ideal behaviour, or numerically derived using

computational fluid dynamics and/or finite element analysis. Modelling may be aided with reference to: Eames, IW, Aphornratana, S & Haider, H 1995, ^ΛΑ theoretical and experimental study of a small-scale steam jet refrigerator' , International Journal of Refrigeration, vol.18, no.6, pp. 378-86.

Huang B., Petrenko V., Chang J, Lin C, Hu S . , ^ΛΑ combined cycle refrigeration system using ejector cooling cycle as bottoming cycle', International Journal of Refrigeration 24 (2001) 391-399.

Zhu C, Wen L., Shock Circle method for ejector performance evaluation, Energy Conversion and

Management, Vol 48, pp 2533-2541, 2007.

Eames I., ^ΛΑ new prescription for the design of supersonic jet pumps: the constant rate of momentum change method' , Applied Thermal Engineering, Vol 22, ppl21-131, 2002.

Although the invention has been described with reference to particular examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. For example, it will be appreciated by a person skilled in the art that the ejector may be used for systems in which the inlet and exit fluids are air, water or any other type of suitable fluid. Further, at least one of the inlet fluids may be a gaseous medium and the exit fluid may be a liquid. Alternatively, the at least one of the inlet fluids may be a liquid medium and the exit fluid may be a gaseous medium.

The reference that is being made to prior art publications does not constitute that these prior art publications are part of the common general knowledge of a person skilled in the art in Australia or in another country.

Claims

The Claims :

1. An ejector comprising:

a housing portion;

a first fluid inlet and a second fluid inlet;

2. The ejector of claim 1 wherein the ejector is arranged such that the position of an outlet of the fluid nozzle relative to the mixing region is self-adj usted dependent on PI and/or a pressure of the mixed first and second fluids.

3. The ejector of claim 2 comprising a passive structure that is arranged for self-adjusting of the position of the outlet of the fluid nozzle.

4. The ejector of claim 1 comprising an actuator that is arranged to adjust a position of the outlet of the fluid nozzle dependent on PI and/or a pressure of the mixed first and second fluids.

5. The ejector of any one of the preceding claims wherein the first fluid has a second pressure P2 after passing through the fluid nozzle, P2 being lower than PI, and the mixture of the first and second fluid exits the ejector with a third pressure P3;

wherein the ejector is arranged such that the position of the outlet of the fluid nozzle relative to the mixing region is adjusting dependent on PI, P2 and/or P3.

6. The ejector of any one of the preceding claims comprising an ejector diffuser having an interior portion with a cross-sectional area that increases in diameter in a direction towards the fluid outlet and is arranged such that the mixture of the first and second fluid exits the ejector through the fluid outlet with the third pressure P3.

7. The ejector of any one of the preceding claims comprising a converging region that is provided in addition to the mixing region and that is positioned such that the mixed first and second fluids converge before exiting the ejector, the converging region having a cross- sectional area that reduces in diameter in a direction towards the outlet of the ejector.

8. The ejector of any one of claims 1 to 6 wherein the mixing region is provided in the form of a converging region and is arranged such that that the first and second fluids converge during or after mixing and before exiting the ejector the converging region having a cross-sectional area that reduces in diameter in a direction towards the outlet of the ejector.

9. The ejector of claim 5 or any one of claims 6 to 8 when dependent on claim 5 wherein the ejector is arranged such that the outlet of the fluid nozzle moves away from the converging region if the pressure P2 increases relative to another pressure within the ejector.

10. The ejector of claim 5 or any one of claims 6 to 7 when dependent on claim 5 wherein the ejector is arranged such that the outlet of the fluid nozzle moves towards or into the converging region if the pressure P3 increases relative to another pressure within the ejector.

11. The ejector of claim 5 or any one of claims 6 to 9 when dependent of claim 5 wherein a length by which the relative position of the ejector is adjusted is largely proportional to a change in P2 relative to another pressure in the ejector.

12. The ejector of claim 5 or any one of claims 6 to 9 when dependent of claim 5 wherein a length by which the relative position of the ejector is adjusted is largely proportional to a change in P3 relative to another pressure in the ejector.

13. The ejector of any one of the preceding claims comprising a diaphragm that seals at least a portion around the fluid nozzle.

14. The ejector of claim 13 wherein the diaphragm is arranged such that the fluid nozzle or a portion thereof moves until the diaphragm or another portion of the ejector provides a sufficient reaction force for locating the fluid nozzle in an adjusted position.

15. The ejector of claim 13 or 14 wherein the diaphragm surrounds at least a portion of the fluid nozzle.

16. The ejector of any one of claims 13 to 15 wherein the diaphragm comprises a suitable polymeric material.

17. The ejector of any one of claims 1 to 12 comprising a moveable wall portion that is rigid.

18. The ejector of claim 17 wherein the moveable wall portion is coupled to a spring.

19. The ejector of any one claim 18 wherein the moveable wall portion is directly or indirectly coupled to the fluid nozzle such that the fluid nozzle or a portion thereof moves with the moveable wall portion until the spring provides a sufficient reaction force for locating the fluid nozzle in an adjusted position.

20. The ejector of any one of the preceding claims comprising a conduit that is arranged such that a portion at or near the fluid nozzle of the ejector has a pressure that is proportional to, or substantially equals, a pressure of the mixed first and second fluids and wherein the ejector is arranged such that that portion is isolated form unmixed first and second fluids.

21. The ejector of claim 20 when dependent on claim 5 wherein the conduit is arranged such that a portion at or near the fluid nozzle of the ejector has a pressure that is proportional to, or substantially equals, the pressure P2 and wherein the ejector is arranged such that that portion is isolated form unmixed first and second fluids.

22. The ejector of claim 21 wherein the conduit is arranged such that a side portion of a diaphragm or a moveable wall portion is exposed to a pressure that is proportional to, or approximately equals, P2 , wherein the ejector is arranged such that an increase in P2 relative to another pressure within the ejector results in a movement of the nozzle or portion thereof away from the mixing region of the ejector.

23. The ejector of claim 20 wherein the conduit is arranged such that a portion at or near the fluid nozzle of the ejector has a pressure that is proportional to, or substantially equals, the pressure P3 and wherein the ejector is arranged such that that portion is isolated form unmixed first and second fluids.

24. The ejector of claim 23 wherein the conduit is arranged such that a side portion of a diaphragm or a moveable wall portion is exposed to a pressure that is proportional to, or approximately equals, P3, wherein the ejector is arranged such that an increase in P3 relative to another pressure within the ejector results in a movement of the nozzle or portion thereof into or towards the mixing region of the ejector.

25. A method of operating an ejector, the method of operating an ejector, the method comprising:

receiving a first fluid having a first pressure;

receiving a second fluid;

26. The method of claim 25 wherein the step of adjusting a position of an outlet of the fluid nozzle relative to the mixing region of the ejector comprises self-adjusting a position of an outlet of the fluid nozzle.

27. The method of claim 25 or 26 wherein the mixing region comprises a converging region.

28. The method of claim 25 or 26 wherein the mixing region is provided in the form of a converging region.