阅读说明：本技术 喷射器制冷回路 (Ejector refrigeration circuit ) 是由 S·赫尔曼 于 2020-12-18 设计创作，主要内容包括：喷射器制冷回路(1)包括：两相回路(2),其包括：排热热交换器(12),其包括入口(12a)和出口(12b)；和喷射器(14),其包括高压入口(14a)、低压入口(14b)和出口(14c)；其中喷射器高压入口(14a)联接至排热热交换器出口(12b)；和蒸发器(18),其包括入口(18a)和出口(18b)；其中,蒸发器(18)的出口(18b)联接至喷射器(14)的低压入口(14b)；且其中喷射器制冷回路(1)还包括蒸气质量传感器(20),该蒸气质量传感器(20)位于排热热交换器(12)的出口(12b)处。(An ejector refrigeration circuit (1) comprises: a two-phase circuit (2) comprising: a heat rejection heat exchanger (12) comprising an inlet (12a) and an outlet (12 b); and an ejector (14) comprising a high pressure inlet (14a), a low pressure inlet (14b) and an outlet (14 c); wherein the ejector high pressure inlet (14a) is coupled to the heat rejecting heat exchanger outlet (12 b); and an evaporator (18) comprising an inlet (18a) and an outlet (18 b); wherein an outlet (18b) of the evaporator (18) is coupled to a low pressure inlet (14b) of the ejector (14); and wherein the ejector refrigeration circuit (1) further comprises a vapor quality sensor (20), the vapor quality sensor (20) being located at the outlet (12b) of the heat rejecting heat exchanger (12).)

1. An ejector refrigeration circuit comprising:

a two-phase loop comprising: a heat rejection heat exchanger comprising an inlet and an outlet; and an ejector comprising a high pressure inlet, a low pressure inlet and an outlet, wherein the ejector high pressure inlet is coupled to the heat rejection heat exchanger outlet; and

an evaporator comprising an inlet and an outlet, wherein the outlet of the evaporator is coupled to the low pressure inlet of the ejector; and is

Wherein the ejector refrigeration circuit further comprises a vapor quality sensor located at an outlet of the heat rejecting heat exchanger.

2. The ejector refrigeration circuit of claim 1, wherein said vapor quality sensor is an optical sensor, such as a camera or a microscope.

3. The ejector refrigeration circuit of claim 1, wherein said vapor quality sensor is a dielectric sensor, such as a capacitive probe.

4. The ejector refrigeration circuit of claim 1, wherein said vapor quality sensor is a wire mesh sensor, or a resistance sensor or an electrical impedance sensor.

5. The ejector refrigeration circuit of any of claims 1 to 4, further comprising a controller configured to receive a signal from said vapor quality sensor, wherein said controller is configured to adjust the capacity of said ejector based on the received signal to ensure a desired pressure rise through the low pressure inlet of said ejector is achieved.

6. The ejector refrigeration circuit of claim 5, wherein the desired pressure rise at the low pressure inlet of said ejector is between 1 and 2 bar.

7. The ejector refrigeration circuit of any preceding claim, comprising a plurality of ejectors connected in parallel.

8. An ejector refrigeration circuit as claimed in any preceding claim wherein the or each ejector is a variable geometry ejector having one or more controllable parameters.

9. The ejector refrigeration circuit of claim 8, wherein said one or more controllable parameters are modified using one or more actuators controlled by said controller.

10. The ejector refrigeration circuit of any one of claims 1 to 7 wherein each of a plurality of ejectors is a non-variable ejector, each having a flow valve upstream of said high pressure inlet.

11. The ejector refrigeration circuit of claim 10, wherein said controller is configured to control flow through one or more of said flow valves.

12. A method of operating an ejector refrigeration circuit, the ejector refrigeration circuit comprising:

a controller;

a two-phase circuit comprising a heat rejection heat exchanger having an inlet and an outlet, and an ejector comprising a high pressure inlet, a low pressure inlet, and an outlet, wherein the ejector high pressure inlet is coupled to the heat rejection heat exchanger outlet;

an evaporator comprising an inlet and an outlet, wherein the outlet of the evaporator is coupled to the low pressure inlet of the ejector, an

A vapor quality sensor located at an outlet of the heat rejection heat exchanger,

wherein the method comprises monitoring vapor quality in the two-phase loop;

providing a signal indicative of vapor quality to the controller; and

the controller adjusts the capacity of the ejector in response to a signal indicative of vapor quality in the two-phase circuit.

13. The method of claim 12, wherein the injector is a variable geometry injector having one or more controllable parameters, wherein the controller adjusts the one or more controllable parameters using one or more actuators to adjust the volume of the injector.

14. The method of claim 12 or 13, wherein the ejector refrigeration circuit comprises a plurality of ejectors connected in parallel.

15. The method of claim 14, wherein each of the plurality of injectors is a non-variable injector, each having a respective flow valve upstream of a high pressure inlet of the injector, wherein the controller controls flow through the one or more flow valves to regulate the entirety.

Technical Field

The present invention relates to an ejector refrigeration circuit, and more particularly to an ejector refrigeration circuit including a sensor for measuring the quality of the vapor.

Background

In a refrigeration circuit, an ejector may be used as an expansion device for the refrigerant. A typical refrigeration circuit includes a compressor to increase the pressure of the refrigerant, which is typically in a vapor phase. The refrigeration circuit also includes a heat rejection heat exchanger/condenser for condensing the refrigerant thereto to a liquid prior to passing it through the expansion device and the heat absorption heat exchanger.

An ejector may be employed between the outlet of the condenser and the inlet of the evaporator. The ejector includes a primary high pressure inlet, a secondary low pressure inlet, and an outlet. When an ejector is used as part of the refrigeration circuit, cooled refrigerant from the condenser may enter the ejector at the high pressure inlet and expand to a lower pressure at the outlet of the ejector.

At the outlet of the ejector, the refrigerant flow will typically be both in the liquid and vapor phase. The gaseous phase will be sent back to the compressor, while the liquid phase will be fed through another expansion valve, and then the evaporator. The fluid leaving the evaporator then flows to the low pressure inlet of the ejector. Due to the pressure difference between the high pressure inlet and outlet of the ejector, liquid refrigerant is drawn through the expansion valve and the evaporator.

For the system to operate effectively, the pressure differential between the high pressure inlet and outlet of the ejector must be sufficient to draw refrigerant fluid through the evaporator at the desired pressure.

If the pressure differential drops below a certain level, the pressure rise through the low pressure inlet of the ejector will also drop, or in some cases decrease to zero. The reduction in pressure rise at the low pressure inlet results in a reduction in refrigerant drawn through the evaporator, which reduces the operating efficiency of the refrigerant circuit.

Therefore, it is desirable to ensure a constant flow through the evaporator by maintaining a desired level of pressure drop in the ejector.

WO 2016/180487 discloses an ejector refrigerant circuit comprising a compressor, a heat rejecting heat exchanger/condenser, an ejector circuit and an evaporator. To ensure a constant flow of refrigerant through the evaporator, a liquid pump is provided between the ejector and the evaporator. The refrigerant circuit also includes a bypass line to allow refrigerant to bypass the pump when not needed.

In operation, if the pressure drop in the ejector is not large enough to cause suction of refrigerant through the evaporator, the liquid pump is operated to increase the pressure of the fluid through the evaporator and the mass flow of refrigerant.

If the pressure drop in the ejector is sufficient to cause suction through the evaporator, the bypass valve is opened and refrigerant will flow directly to the evaporator bypassing the liquid pump.

Disclosure of Invention

Viewed from a first aspect, there is provided an ejector refrigeration circuit comprising: a two-phase loop comprising: a heat rejection heat exchanger comprising an inlet and an outlet, and an ejector comprising a high pressure inlet, a low pressure inlet and an outlet, wherein the ejector high pressure inlet is connected to the heat rejection heat exchanger outlet; an evaporator comprising an inlet and an outlet, wherein the outlet of the evaporator is connected to the low pressure inlet of the ejector; and wherein the ejector refrigeration circuit further comprises a vapor quality sensor located at an outlet of the heat rejecting heat exchanger.

The injector may operate effectively in transcritical conditions, but at subcritical conditions, the pressure rise of the injector may be reduced. To counteract this reduction in pressure rise, some prior art systems require a pump (as in WO 2016/180487) for maintaining the required pressure once the pressure drop falls below a certain level.

It has been found that a small amount of vapor in the system under subcritical conditions can increase the pressure rise of the ejector without the need for a pump. Thus, higher vapor quality results in increased injector efficiency. However, this results in an increase in the amount of vapor processed by the compressor. Thus, if the vapor quality increases too much, more compressors may be required, which may result in an overall decrease in the operating efficiency of the refrigeration circuit.

The optimum amount of vapor should be an amount sufficient to provide an increase in ejector pressure rise, thus eliminating the need for a pump, but without significantly affecting the operation of the compressor.

The refrigeration circuit typically uses temperature and pressure sensors to monitor the refrigerant and control the high pressure circuit accordingly. However, given that the flow in the high pressure circuit of the refrigeration circuit is two-phase, these sensors will not provide the necessary information to determine the vapor quality.

The proposed circuit solves this problem by providing a vapor quality sensor at the outlet of the heat rejecting heat exchanger. The values recorded by the vapor quality sensor may be used to control the injector, in particular the opening of the injector, to ensure that there is a significant pressure drop to produce a sufficient pressure rise at the low pressure inlet.

By ensuring that sufficient pressure rise is provided, the refrigerant flow through the expansion valve and/or evaporator can also be maintained at a desired level without the need for an additional pump. Thus, the ejector refrigeration circuit of the first aspect may not have an additional pump for maintaining ejector pressure conditions. In some examples, the only pressure boosting device within the refrigeration circuit may include an ejector (or ejectors as described below) and a compressor device of the circuit, which may be a multi-stage or parallel compression device.

The refrigeration circuit is simplified compared to conventional arrangements in view of the fact that a pump is no longer required. This in turn can result in reduced component costs and reduced maintenance time and costs, thereby reducing operational costs and improving work efficiency overall.

The ejector refrigeration circuit may further include a compressor having an inlet and an outlet and a flash tank including an inlet, a liquid outlet, and a gas outlet.

The ejector outlet may be coupled to an inlet of the flash tank. The flash tank gas outlet may be connected to an inlet of the compressor. An outlet of the compressor may be coupled to an inlet of the heat rejection heat exchanger.

The ejector refrigeration circuit may further comprise an expansion valve. An inlet of the evaporator may be coupled to a liquid outlet of the flash tank to a liquid outlet via an expansion valve. The inclusion of an expansion valve allows the system to control the amount of refrigerant released into the evaporator. This helps to ensure that the optimum amount of liquid is supplied to the evaporator and only vapour leaves the evaporator. Alternatively, the inlet of the evaporator may be directly coupled to the liquid outlet of the flash tank. Flow through the evaporator may be due to a pressure drop between the high pressure inlet and the outlet resulting in a pressure rise through the low pressure inlet of the ejector.

The vapor quality sensor may be an optical sensor, such as a camera or microscope. Alternatively, the vapor quality sensor may be a dielectric sensor, such as a capacitance probe. As a further alternative, the vapor quality sensor may be a wire mesh sensor, a resistance sensor, or an electrical impedance sensor. Multiple sensor types may optionally be included for redundancy and/or increased accuracy.

The ejector may be a variable geometry ejector having one or more controllable parameters. The one or more controllable parameters may include, for example, a high pressure inlet diameter, a low pressure inlet diameter, an outlet diameter, a throat diameter, a diffuser length, a mixing chamber diameter. One or more controllable parameters may be adjusted to vary the capacity of the injector.

One or more actuators and/or valves may be used to change one or more controllable parameters. The actuator may be electrically powered, such as a solenoid. Alternatively, the actuator may be pneumatic or hydraulic. The actuator may adjust one or more controllable parameters by moving a restrictor that adjusts the diameter of the inlet and outlet. Alternatively, the throat or diffuser length may be adjusted by an actuator. The injector may include a needle valve and a corresponding needle actuator disposed within the inlet. The needle actuator may move the tip of the needle valve into and out of the throat to change the diameter accordingly.

The refrigeration circuit may include a plurality of ejectors. The number of ejectors depends on the desired level of expansion of the refrigerant. The required level of expansion can be determined by pressure and temperature sensors and a steam quality sensor. This may be the set output of the entire ejector refrigeration circuit.

Multiple ejectors may also provide one or more redundancies. Given the location of the injector in the circuit, if it fails, the entire circuit will also fail. The ejector refrigeration circuit may include one or more branch flow paths upstream of each inlet of each ejector of the plurality of ejectors. Each of the one or more branch flow paths may divert from the high-pressure circuit flow path at a branch point. Alternatively, each of the one or more branch flow paths may be directly connected to an outlet of the heat rejecting heat exchanger.

In the event that one of the plurality of injectors becomes clogged or otherwise fails by another device, the valve may prevent flow to the failed injector and may divert it to one of the other plurality of injectors that is still operational.

This can help ensure that the ejector refrigeration circuit remains operational at all times.

The plurality of ejectors may be connected in parallel such that each high pressure inlet is connected to an outlet of the heat rejecting heat exchanger, respectively.

Each of the plurality of injectors may be a variable geometry injector. Each of the plurality of injectors may be configured to have a different capacity. This will result in a different pressure drop, and therefore a different pressure rise, across each ejector and thus provide a greater range for modifying the operating efficiency of the ejector.

Each of the plurality of injectors may be a non-variable injector. Each of the non-variable ejectors may be connected in parallel. Each of the plurality of injectors may be configured with a separate flow valve that may control flow to the high pressure inlet of the respective injector. The capacity of the plurality of injectors may be modified by limiting the flow through the valve for one or more of the plurality of injectors. The use of valves and multiple injectors allows for capacity modification using a non-variable injector.

Non-variable ejectors are advantageous because they do not include moving parts. Therefore, they are less prone to failure and require less maintenance. However, they provide a smaller range for modifying the capacity than variable geometry injectors. Furthermore, the capacity of a non-variable injector can only be adjusted by the presence of an additional injector, whereas the capacity of a variable geometry injector can easily be modified by a single injector.

The ejector refrigeration circuit may include a controller. The controller may receive a signal from the vapor quality sensor. The controller may control a parameter of the variable geometry injector based on a signal from the vapor quality sensor. The controller may be configured to adjust parameters of the variable geometry ejector to ensure a sufficient pressure drop across the ejector to provide sufficient suction through the evaporator.

Alternatively, the controller may be configured to restrict flow through one or more valves of the high pressure inlet on each of the plurality of non-variable ejectors. This may control the flow to each injector and serve to divert fluid away from a potentially malfunctioning injector. Also, each injector non-variable injector may be provided with different parameters. Thus, the control may take into account the expansion demand and adjust the flow rates to each other accordingly.

A single controller may be configured to control parameters of each of the plurality of variable geometry injectors. Alternatively, each of the plurality of variable geometry injectors may be controlled by a separate controller. Each individual controller may be controlled by a central processor. As a further alternative, a single controller may be configured to control all of the valves of each of the plurality of non-variable injectors, or a separate controller may be configured to control each of the valves.

The ejector refrigeration system may also include one or more temperature sensors and one or more pressure sensors. In addition to, or instead of, the vapor quality sensor, a temperature sensor and/or a pressure sensor may provide useful information.

The controller may be configured to further receive signals from the one or more temperature sensors and the one or more pressure sensors and modify a parameter of the variable geometry injector based on the signals.

The controller may also control the operation of other components of the ejector refrigeration circuit, such as the compressor and the expansion valve. For example, the controller may control the operation of the compressor based on a signal from the pressure sensor. In particular, the compressor unit may comprise a plurality of compressors. In the event that high compression is required, all of the multiple compressors within the compressor unit may be active. Alternatively, if only low compression is required, only a small number of compressors may be activated.

In some cases, the circuit between the condenser outlet and the ejector may be single phase, with only liquid present. In this case, the pressure sensor and the temperature sensor may be sufficient to provide the necessary information to optimize the parameters of the variable geometry injector. The single-phase circuit may also be applied to circuits where only vapor is present.

However, as described above, if a small amount of vapor remains in the circuit after the condenser, the ejector efficiency increases. Due to the presence of vapor in the circuit, the pressure and temperature sensors are not sufficient to provide sufficient information and further vapor quality measurements need to be made.

The two-phase circuit between the condenser and the ejector may be a high-pressure circuit. The majority of the refrigerant in the high pressure two-phase loop may be liquid at high pressure flowing through the compressor and condenser.

The ejector refrigeration circuit may further comprise a low pressure, low temperature circuit having an evaporator. The low temperature and low pressure circuit may further comprise an expansion valve, which may be in addition to the ejector.

The evaporator may comprise one or more fans. The fan promotes airflow through the evaporator to increase the rate of heat absorption. The speed of the fan may be controlled by the controller and may depend on the output required by the ejector refrigeration circuit. The controller may be the same controller used to change the injectors, or it may be a separate controller.

The flash tank may include a liquid portion and a gaseous portion. The liquid portion and the gaseous portion may be separated by gravity. The flash tank gas outlet may be located near the top of the flash tank and may feed the compressor. The flash tank liquid outlet may be located near the bottom of the tank and feed an expansion valve and/or an evaporator.

When passing through the ejector, the resulting two-phase mixture may expand, resulting in a drop in pressure and temperature. In the present system, a small amount of steam is already present in the high-pressure circuit, which steam is fed to the ejector. However, once through the injector, a large proportion of vapor may be present. Feeding vapor to the evaporator along with the cryogenic liquid refrigerant may reduce the efficiency of the evaporator. This is due to the small surface area of contact between the liquid refrigerant and the evaporator coil surfaces. By including a flash tank, vapor and liquid refrigerant can be separated and a liquid outlet fed to the evaporator is located near the bottom of the flash tank ensuring that only liquid enters the evaporator. Thus, the efficiency of the refrigeration circuit is further improved by providing a flash tank.

In order to provide sufficient lift and suction through the evaporator, the required pressure drop across the ejector may be between 0.2 and 4 bar, optionally between 1 and 2 bar, optionally between 1.5 and 2 bar.

The ejector refrigeration circuit may be adapted for any type of refrigerant. The ejector refrigeration circuit may be adapted for use as a refrigerant with carbon dioxide. Alternative refrigerants for use in ejector refrigeration systems may include freons, CFCs, HCFCs and HFCs. The type of refrigerant selected will affect the performance of the ejector refrigeration cycle. The stability and flammability of each refrigerant may also vary, which may be an important consideration in selecting the refrigerant.

Ejector refrigeration circuits are used in a variety of refrigeration applications. These may include domestic and commercial refrigeration, such as refrigeration for storing food and beverages in homes and stores. Ejector refrigeration circuits can also be used in refrigeration and industrial refrigeration. Additionally, the ejector refrigeration circuit may be used for air conditioning.

Viewed from a second aspect, there is provided a method of operating an ejector refrigeration circuit comprising: a controller; a two-phase circuit comprising a heat rejection heat exchanger having an inlet and an outlet, and an ejector comprising a high pressure inlet, a low pressure inlet, and an outlet, wherein the ejector high pressure inlet is coupled to the heat rejection heat exchanger outlet; an evaporator comprising an inlet and an outlet, wherein the outlet of the evaporator is coupled to the low pressure inlet of the ejector, and a vapor quality sensor located at the outlet of the heat rejection heat exchanger, wherein the method comprises monitoring the vapor quality in the two-phase loop; providing a signal indicative of the vapor quality to a controller; and adjusting a capacity of the ejector in response to the signal indicative of the vapor quality in the two-phase circuit.

The method may be used with the ejector refrigeration circuit discussed above in relation to the first aspect, and the circuit may include any or all of the other optional features discussed above.

The ejector may be a variable geometry ejector. The one or more parameters adjusted in response to the signal indicative of vapor quality may be one or more parameters of a variable geometry injector.

Accordingly, the method may include the step of adjusting one or more parameters of the variable geometry injector. This may ensure that the required pressure drop is achieved to ensure a sufficient pressure rise at the low pressure outlet and thus a sufficient suction through the evaporator.

The circuit may include a plurality of injectors. The controller may control operation of each of the plurality of injectors. Alternatively, the plurality of controllers may control each of the plurality of injectors.

The one or more controllers may adjust one or more parameters of the variable geometry ejector through a series of actuators. Each actuator may move a separate part of the ejector.

The ejector circuit may comprise a plurality of non-variable ejectors. Each of the plurality of non-variable ejectors may have a respective flow valve upstream of the high pressure inlet. The method may include limiting flow through one or more flow valves in response to a signal from a vapor quality sensor.

The method may include using carbon dioxide as the refrigerant. Alternatively, freon, CFC, HCFC or HFC may be used as the refrigerant.

Drawings

Exemplary embodiments of the invention are described below, by way of example only, and with reference to the accompanying drawings.

Fig. 1 shows a schematic diagram of an ejector refrigeration circuit.

Detailed Description

The ejector refrigeration circuit 1 shown in fig. 1 comprises a high-pressure two-phase circuit 2 and a low-pressure low-temperature circuit 3. The high-pressure two-phase circuit 2 comprises one or more compressors 10a,10b,10c forming a compressor unit, having an inlet 10d and an outlet 10 e.

An outlet 10e of a compressor 10a,10b,10c of the compressor unit is fluidly connected to an inlet 12a of a heat rejecting heat exchanger 12. The heat rejection heat exchanger may also be referred to as the condenser 12. The condenser 12 is fluidly connected to a high pressure inlet 14a of the ejector 14.

The ejector also includes a low pressure inlet 14b and an outlet 14 c. The outlet 14c of the ejector is fluidly connected to the inlet 16a of the flash tank 16. The flash tank 16 includes a liquid portion and a vapor portion, wherein the liquid portion and the vapor portion are separated by gravity due to the different densities of the fluids.

The flash tank 16 also includes a vapor outlet 16b near the top of the flash tank and a liquid outlet 16c near the bottom of the flash tank 16.

The vapor outlet 16b of the flash tank 16 is fluidly connected to the inlet 10d of the compressor unit 10a,10b,10 c. The liquid outlet 16c of the flash tank is fluidly connected to an inlet 18a of an evaporator 18 via an expansion valve 17. An outlet 18b of the evaporator 18 is fluidly connected to the low pressure inlet 14b of the ejector 14.

In operation, a refrigerant, such as carbon dioxide, is circulated through the ejector refrigeration circuit. A low pressure vapor line 24 delivers refrigerant in gaseous form to the compressor 18. The compressor 18 increases the pressure of the refrigerant and delivers it to the condenser 12.

The condenser 12 is configured to transfer heat from the refrigerant to the environment, reducing the temperature of the refrigerant in the process. This decrease in temperature causes the refrigerant to condense from a vapor to a liquid. In a conventional ejector refrigeration circuit, the refrigerant leaving the outlet 12b of the condenser 12 is a single phase liquid refrigerant. However, in the embodiment shown in fig. 1, the refrigerant leaving the outlet 12b of the condenser 12 is a two-phase refrigerant of liquid and vapor. Most refrigerants are liquids with a small amount of vapor remaining.

In the ejector refrigeration circuit 1 of fig. 1, the condenser comprises two fans configured to blow air across the condenser to enhance heat transfer from the refrigerant to the environment. It will be appreciated that there may be more or less than two fans.

The high pressure two phase line delivers the two phase fluid to the high pressure inlet 14a of the ejector 14, which is configured to expand the refrigerant to a lower pressure level.

In the ejector 14, the refrigerant enters through the high-pressure inlet 14a and enters the converging portion. It then passes through the throat at the outlet 14c of the ejector 14 and then through the diverging portion. The movement from the inlet portion, through the throat and then to the diverging portion increases the flow rate and decreases the pressure of the refrigerant. The pressure drop in the refrigerant between the inlet 14a and the outlet 14c of the ejector 14 draws the secondary flow through the low pressure inlet 14 b.

Low pressure two-phase refrigerant exits the ejector 14 through the outlet 14c and enters the flash tank 16 through the flash tank inlet 16 a. Within the flash tank 16, the refrigerant separates by gravity into a liquid portion in a lower portion of the flash tank 16 and a vapor portion in an upper portion of the flash tank 16.

The refrigerant in the vapor portion of the flash tank 16 exits via vapor outlet 16b and returns to the compressor units 10a,10b,10 c. At the same time, the refrigerant in the liquid portion exits the flash tank 16 through the liquid outlet 16c and is delivered to the expansion valve 17 and then enters the evaporator 18. Depending on the degree of expansion achieved by the ejector 14, the expansion valve 17 may not be necessary. In this case, a bypass line (not shown) may be used.

In the evaporator 18, heat is transferred from the environment to the liquid refrigerant. This heat causes the refrigerant to evaporate, removing heat from the environment. The resulting refrigerant vapor exits the evaporator 18 through the outlet 18b and is delivered to the low pressure inlet 14b of the ejector.

In operation, the pressure drop between the high pressure inlet 14a and the outlet 14c of the ejector causes refrigerant from the flash tank 16 to be drawn into the low pressure inlet 14b through the expansion valve 17 and the evaporator 18. Therefore, the pressure drop must be maintained at the required amount and, therefore, the efficiency of the ejector 14 must also be maintained at an optimum level.

In conventional systems, the refrigerant in the high pressure circuit 2 between the condenser 12 and the ejector 14 is a single phase liquid refrigerant. However, it has been shown that having a small amount of vapor in the refrigerant leaving the condenser can improve the efficiency of the ejector 14.

However, this must be balanced against the compressor capacity, as the more vapor present in the circuit, the more work the compressor will do. This may result in the need for more compressors, which increases the complexity of the refrigeration circuit and reduces overall operating efficiency.

Thus, there is an optimum amount of vapor, which results in a sufficient increase in ejector efficiency without significantly affecting the operation of the compressor.

Conventional ejector refrigerant circuits include pressure and temperature sensors sufficient for single-phase flow. However, given that the flow in the high pressure circuit 2 is two-phase, the pressure and temperature measurements themselves may not provide sufficient information to control the system accordingly.

The ejector refrigeration circuit 1 shown in fig. 1 comprises a vapor quality sensor 20 at the outlet 12b of the condenser 12. The vapor quality sensor 20 may be an optical sensor, such as a camera or microscope. Alternatively, the vapor quality sensor 20 may be a dielectric sensor such as a capacitance probe.

The ejector refrigeration circuit 1 further comprises a controller 22, the controller 22 being configured to receive a signal from the vapor quality sensor 20. The controller may also be configured to receive signals from pressure and temperature sensors (not shown).

Based on the signal received from the vapor quality sensor 20, the controller 22 is configured to adjust the capacity of the ejector 14 to maintain an optimal pressure drop to ensure the desired suction through the low pressure inlet 14b while keeping the amount of vapor to the compressor to a minimum.

The ejector 14 may be a variable geometry ejector that includes one or more actuators for adjusting one or more parameters of the ejector. The actuator is configured to be controlled by the controller 22 based on a signal from the steam quality sensor.

The ejector refrigeration circuit 1 may comprise a plurality of ejectors 14 according to the desired level of expansion. Multiple injectors 14 may be connected in parallel.

Each of the plurality of injectors may be a variable geometry injector, each having one or more actuators for adjusting one or more parameters. Controller 22 may configure each injector to have the same capacity. Alternatively, the controller 22 may configure each injector 14 to have a different capacity. The flow valve may be located upstream of the high pressure inlet 14a of each ejector 14. Controller 22 may be configured to limit flow through one or more valves according to a desired capacity of the injector.

In an alternative arrangement, each of the plurality of injectors 14 may be a non-variable injector, each having a flow valve upstream of the high pressure inlet 14 a.

The controller 22 may be configured to limit flow through one or more flow valves for each of the plurality of injectors 14. Rather than using a variable geometry injector, this approach may be used as an alternative to adjusting the capacity of the injector based on the signal received from the vapor quality sensor.

Thus, the ejector refrigeration circuit 1 ensures an optimum pressure drop to ensure adequate suction through the expansion valve and evaporator without the need for a pump as in conventional systems. This results in a simplified, more compact circuit, with lower maintenance costs.