HK1135760B

HK1135760B - Refrigerant system with pulse width modulation control in combination with expansion device control

Info

Publication number: HK1135760B
Application number: HK10102503.4A
Authority: HK
Inventors: Alexander Lifson; Michael F. Taras; Mark A. Lifson
Original assignee: Carrier Corporation
Filing date: 2006-11-07
Publication date: 2013-11-08

Description

Refrigeration system having a pulse width modulation control in combination with an expansion device control

[ technical field ] A method for producing a semiconductor device

The present invention relates to a refrigeration system (regenerative system) in which the capacity of the refrigeration system is regulated by a pulse width modulation control and the main expansion device of the refrigeration system is used to limit or eliminate refrigerant flow exchange between the evaporator and the condenser when the pulse width modulation control is preventing compression of the refrigerant or at least partially blocking the flow of refrigerant into the compressor.

[ background of the invention ]

One method known in the art for supporting the capacity modulation provided by a refrigerant system is to use a pulse width modulation control. It is known in the art to use a pulse width modulation control to rapidly cycle a valve between open and closed positions to control the flow of refrigerant through a refrigerant system to regulate capacity. Thus, by limiting the refrigerant flow through the refrigeration system, the capacity can be reduced below the full load capacity of the refrigerant system. There are many ways to apply pulse width modulation control techniques to various components to reduce refrigerant system capacity. For example, a valve located at the compressor suction port can be cycled in a pulse width modulation manner or the compression element itself can be engaged and disengaged at a certain rate.

One problem that arises with the prior art use of pulse width modulation controllers is: while this technique does provide control over the capacity of the refrigerant system, there is a possibility of undesirably large fluctuations in suction and discharge system pressures (e.g., between the "open" and "closed" positions of the pulse width modulation valve). Such pressure fluctuations are undesirable and make it difficult to control the operation of various system components. Also in a conditioned environment, this may make it more difficult to maintain constant parameters such as temperature and humidity. Furthermore, the operation of the overall system may become less efficient due to irreversible losses associated with these pressure fluctuations.

On the other hand, if the pulse width modulated valve is cycled frequently to minimize pressure fluctuations, there are additional cycling losses associated with switching certain system components from a state where the valve is open to a state where the valve is in a closed position. Furthermore, the chance of valve failure is increased due to this large number of cycles.

As mentioned above, there is another known solution using pulse width modulation for engaging and disengaging the compression elements of a scroll compressor. This is achieved by rapidly changing the refrigerant pressure in the back pressure chamber of the scroll compressor. When the pressure in the back pressure chamber is low, then the components of the scroll compressor are allowed to move out of contact with each other and there will be no effective compression of the refrigerant. On the other hand, when the pressure in the back pressure chamber is high, the scroll elements match each other and provide full compression of the refrigerant flowing through the compressor. The above-described problems of suction and/or relief pressure fluctuations associated with this control may be undesirable and cause problems with normal system operation.

In another controller for an HVAC & R system, a pulse width modulation controller can be provided for pulse width modulation of the scroll elements by separating the scroll elements in a pulse width modulated manner and returning them to contact with each other, during which the controller will monitor the pressure or temperature on the suction port (low pressure) side and adjust the duty cycle of the pulse width modulation accordingly. However, the disclosed controller does not specifically seek to minimize fluctuations associated with discomfort and loss of efficiency of the conditioned space, while it does not control the suction pulse width modulation valve, and also does not monitor the discharge (high pressure) side environment of the system.

It is known in the art to include an isolation valve between the evaporator and the condenser to block flow between the two components when the isolation valve is used in conjunction with pulse width modulation of the scroll element. In this case, the isolation valve is normally closed when the compressor is not compressing refrigerant. This solution requires the inclusion of a separate additional isolation valve in conjunction with the pulse width modulated compressor requirements, thereby increasing the overall cost of the refrigerant system.

[ summary of the invention ]

In a disclosed embodiment of the invention, the compressor is provided with a pulse width modulation control. In one embodiment, the suction modulation valve is controlled in a pulse width modulation manner to control the flow of refrigerant to the compressor. In a second embodiment, the pressure of the back pressure chamber of the scroll compressor is varied in a pulse width modulated manner to engage or disengage the scroll elements. For both embodiments, the expansion device located between the condenser and the evaporator is preferably an electronic expansion device capable of rapid cycling between an open position and a closed position. When the compressor is in the "off" position due to the pulse width modulation control, the expansion device is also significantly closed. When the compressor is in the "on" position due to the pulse width modulation control, the expansion device is also significantly opened. In this way, the refrigerant flow between the condenser and the evaporator is immediately cut off. Thus, the above-described problem of pressure fluctuations can be solved without the need to have an isolation valve. Note that in the context of the present invention, the "closed" position of the compressor refers to the situation when the scroll members are separated from each other and little or no compression occurs. Likewise, the "open" position refers to a condition in which the compressor elements are engaged and the scroll compressor is compressing refrigerant and moving it from the evaporator to the condenser.

According to one aspect of the present invention, there is provided a refrigeration system comprising:

a compressor for compressing refrigerant and delivering the refrigerant to a first heat exchanger, from which the refrigerant passes through an expansion device, into a second heat exchanger, and from which the refrigerant returns to the compressor; and

a pulse width modulation control for rapidly modulating the flow of refrigerant to the compressor between a high flow position and a low flow position, the pulse width modulation control further using pulse width modulation to substantially move the expansion device toward a closed position when the compressor is in the low flow position and to substantially move the expansion device toward an open position when the compressor is in the high flow position.

In the above refrigeration system, wherein the expansion device is an electronically controlled expansion device.

In the above refrigeration system, wherein a suction modulation valve is located between the second heat exchanger and the compressor, and the suction modulation valve is controlled to rapidly open and close to regulate the flow of refrigerant to the compressor between the high flow position and the low flow position.

In the above refrigeration system, wherein the compressor is a scroll compressor and has a back pressure chamber that rapidly cycles between high and low pressure conditions to vary the output of the compressor between the high and low flow positions.

In the above refrigeration system, wherein when the compressor is in the low flow position, the expansion device is moved to a fully closed position.

In the above refrigeration system, the pulse width modulation cycle time is between 2 and 30 seconds.

In the above refrigeration system, wherein the time that the expansion device is in said closed position is different from the time that the compressor is in said low flow position.

In the refrigeration system described above, the time difference between the time that the expansion device is in the closed position and the time that the compressor is in the low flow position is between 1 and 3 seconds.

In the above refrigeration system, wherein the time that the expansion device is in said closed position is delayed relative to the time that the compressor is in said low flow position, the time that the expansion device is in said open position is delayed relative to the time that the compressor is in said high flow position.

In the above refrigeration system, wherein the delay is between 1 and 3 seconds.

In the refrigerant system as set forth above, wherein vibration on at least one component of said refrigerant system is monitored and said monitored vibration is used to adjust at least one operating parameter of at least one of a pulse width modulated expansion device and a pulse width modulated refrigerant flow to said compressor.

In the above refrigeration system, wherein the pressure fluctuation controller is provided for tightly maintaining at least one of the temperature and the humidity in the environment to be conditioned.

In the above refrigeration system, wherein the pulse width modulation of the expansion device and the pulse width modulation of the amount of refrigerant flowing to the compressor are provided for controlling and limiting pressure fluctuations in the first heat exchanger, the second heat exchanger, or both the first and second heat exchangers.

According to another aspect of the present invention, there is also provided a method of operating a refrigeration system, comprising:

providing a compressor for compressing refrigerant and delivering the refrigerant to a first heat exchanger, refrigerant passing from the first heat exchanger passing through an expansion device into a second heat exchanger, refrigerant passing from the second heat exchanger returning to the compressor; and

the flow of compressed refrigerant to the compressor is controlled between a high flow position and a low flow position by using pulse width modulation for rapidly modulating the flow of refrigerant to the compressor between the high flow position and the low flow position, and also pulse width modulation is used to significantly move the expansion device toward a closed position when the compressor is in the low flow position and to significantly move the expansion device toward an open position when the compressor is in the high flow position.

In the above method, wherein a suction modulation valve is located between the second heat exchanger and the compressor, and the suction modulation valve is controlled to rapidly open and close to regulate the flow of refrigerant to the compressor between high and low flow positions.

In the above method wherein the compressor is a scroll compressor and has a back pressure chamber that rapidly cycles under high and low pressure conditions to vary the output of the compressor between the high and low flow positions.

In the method above, wherein the expansion device is moved to a fully closed position when the compressor is in the low flow position.

In the above method, the pulse width modulation cycle time is between 2 and 30 seconds.

In the method above, wherein the time that the expansion device is in the closed position is different than the time that the compressor is in the low flow position.

In the method above, the time difference between when the expansion device is in the closed position and when the compressor is in the low flow position is between 1 and 3 seconds.

In the method above, wherein the time that the expansion device is in said closed position is delayed relative to the time that the compressor is in said low flow position, the time that the expansion device is in said open position is delayed relative to the time that the compressor is in said high flow position.

In the above method, wherein the delay is between 1 and 3 seconds.

In the method above, wherein vibration on at least one component in the refrigerant system is monitored, and the monitored vibration is used to adjust at least one operating parameter of at least one of the pulse width modulated expansion device and the pulse width modulated refrigerant flow to the compressor.

In the above method, wherein the pressure fluctuation controller is provided to tightly maintain at least one of temperature and humidity in the environment to be conditioned.

In the above method, wherein the pulse width modulation of the expansion device and the pulse width modulation of the amount of refrigerant flowing to the compressor are provided for controlling and limiting pressure fluctuations in the first heat exchanger, the second heat exchanger, or both the first and second heat exchangers.

According to still another aspect of the present invention, there is also provided a refrigeration system including:

the compressor is used for compressing refrigerant and conveying the refrigerant to the first heat exchanger, the refrigerant passing through the first heat exchanger passes through the expansion device and enters the second heat exchanger, and the refrigerant passing through the second heat exchanger returns to the compressor; and

a pulse width modulation control for controlling a suction modulation valve disposed between the second heat exchanger and the compressor and which is rapidly modulated between open and closed positions to regulate the flow of refrigerant to the compressor, and the control further employs pulse width modulation to move the expansion device substantially toward the closed position when the suction modulation valve is moved toward the closed position and to move the expansion device substantially toward the open position when the suction modulation valve is moved toward the open position.

a compressor for compressing refrigerant and delivering the refrigerant to a first heat exchanger, refrigerant passing from the first heat exchanger passing through an expansion device and into a second heat exchanger, refrigerant passing from the second heat exchanger returning to the compressor; and

the compressor is a scroll compressor and has a back pressure chamber that is rapidly cycled using a pulse width modulated controller to vary the output of the compressor between high and low flow positions under high and low pressure conditions, and the expansion device is also controlled by pulse width modulation, the expansion device being moved significantly toward a closed position when the compressor is in the low flow position and toward an open position when the compressor is in the high flow position. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

[ description of the drawings ]

Figure 1 shows a schematic diagram of a refrigeration system incorporating a first embodiment of the invention;

fig. 2 shows a compressor used in a second embodiment of the present invention;

FIG. 2A shows a refrigeration system having the compressor of FIG. 2;

FIG. 3 is a graph illustrating pressure fluctuations for a prior art system and a controller of the present invention.

[ detailed description ] embodiments

A refrigeration system 20 is shown in fig. 1, and the refrigeration system 20 includes a compressor 22, the compressor 22 compressing refrigerant and delivering it downstream to a heat exchanger 24. The heat exchanger 24 will function as a condenser when operating in the cooling air conditioning mode and is an outdoor heat exchanger. Although the invention is shown as an air conditioning system, it will be appreciated that the invention will also extend to heat pumps and other applications (e.g., refrigeration applications). Also, it should be understood that the basic refrigerant system illustrated in fig. 1 (as well as fig. 2A) may have various options and features to enhance its operation and control (including vapor injection, bypass unloading, various dehumidification configurations, tandem compressors, multi-circuit arrangements, variable speed components, etc.). All such system design variations are within the scope of the present invention and are equally protected by the present invention.

An expansion device 26 is located downstream of the heat exchanger 24. Expansion device 26 may be an electronic expansion valve that is capable of rapid cycling between open and closed positions to control the amount of refrigerant flowing through expansion device 26. Heat exchanger 28 is located downstream of expansion device 26. The heat exchanger 28 is an indoor heat exchanger and it operates in a cooling air conditioning mode to provide the function of an evaporator. The refrigerant flowing from the heat exchanger 28 passes through a suction modulation valve 30 and returns to the compressor 22. The controller 32 provides pulse width modulation control to both the suction modulation valve 30 and the electronic expansion valve 26. When the controller 32 determines that the refrigerant system 20 should operate in a reduced (partially unloaded) capacity mode, the suction modulation valve 30 is rapidly cycled between open and closed positions to control the amount of refrigerant flowing to the compressor. When such a controller is to be actuated, the control logic and timing, as well as the details of the controller and the design of the valve 30, are well known in the art. What is invented here is that the controller 32 synchronously controls the expansion valve 26 so that when the valve 30 is biased toward the closed position, it is significantly biased toward the closed position. In this way, the heat exchangers 24 and 28 may have substantially no flow exchange when the mass flow of refrigerant to the compressor is reduced.

Figure 2 shows another embodiment 301 wherein the compressor is a scroll compressor having a non-orbiting scroll member 304 and an orbiting scroll member 302. As is well known, the back pressure chamber 306 may receive pressurized fluid from a source 308 and pass it through a flow (e.g., solenoid) valve 310. The controller 312 controls the opening and closing of the flow valve 310 using a pulse width modulation method. By rapidly opening and closing the flow valve 310, the pressure in the backpressure chamber 306 cycles between a high value and a low value. When the back pressure chamber is tapped at high pressure, this pressure pushes the non-orbiting scroll 304 against the orbiting scroll 302, substantially eliminating any bypass leakage of compressed refrigerant through the compression elements. Thus, the refrigerant is compressed in the compressor and is passed through the entire system. When the valve 310 blocks the flow of high pressure refrigerant to the back pressure chamber 306, the lower pressure in the back pressure chamber 306 allows the scroll elements 304 and 302 to move away from each other, thereby creating a significant gap between the orbiting scroll 302 and the non-orbiting scroll 304, while creating little or no refrigerant compression in the compression chamber 301. This structure is schematically shown and is generally known in the art. Many variations of this concept, including pulse width modulation techniques applied to different compressor types, are known in the art and are within the scope of the present invention. The controller 312 is also in communication with the expansion device 26 in this embodiment and is shown in line 120 in fig. 2A, in a manner similar to the embodiment of fig. 1.

By controlling the expansion device 26 in conjunction with the suction modulation valve 30 of the embodiment of fig. 1 or in conjunction with the flow valve 310 of the embodiment of fig. 2, the potential overpressure surge problems of the prior art can be controlled and eliminated. FIG. 3 shows P_condAnd P_evapWhich correspond to fluctuating pressures in the condenser and evaporator without the pulse width modulation control of the expansion device 26. Furthermore, P'_condAnd P'_evapAre the pressures in the condenser and evaporator, respectively, in the case of a pulse width modulated control with an expansion device 26 provided by the present invention, which show a significant reduction in pulse amplitude.

As described above, the electronic expansion device 26 is cycled substantially between open and closed positions in a pulse width modulated manner with the associated opening and closing of the suction modulation valve 30 or valve 310 to reduce pressure fluctuations throughout the system and thereby improve operating efficiency and occupant comfort in the conditioned space. It should be noted that the open and closed positions for the expansion device 26 do not necessarily correspond to fully open and fully closed positions. For example, a partially closed position for electronic expansion device 26 may be targeted to reduce pressure fluctuations to an acceptable level. In addition, the synchronous operation of devices 26 and 30 (or 310) for flow control is valuable, although it may be beneficial to slightly delay the closing of the electronic expansion device 26, thereby allowing some refrigerant flow due to flow inertia to flow to the low pressure side of the refrigerant system. For the same reason, the cycle time interval for the expansion device 26 may be slightly different than the cycle time interval for the flow control device 30 or 310. In general, typical cycle times for the flow control devices 26 and 30 (or 310) may range from 5 seconds to 30 seconds. Typical time delays can be on the order of 2-3 seconds and are highly dependent on the size (or internal volume) of the refrigeration system.

It should also be noted that the open and closed positions of the suction modulation valve 30 (or 310) may not necessarily correspond to the most or least likely open or closed positions of the valve. Pressure fluctuations are particularly important on the high-pressure side of the refrigeration system (the condenser portion of the refrigeration system), where the pressure of the refrigerant at the higher pressure is higher than the pressure of the refrigerant on the low-pressure side, and thus the magnitude of the pressure fluctuations on the high-pressure side is generally higher than the magnitude of the pressure fluctuations on the low-pressure side (the evaporator portion of the refrigeration system). Pressure fluctuations are known to be detrimental to achieving the desired temperature and/or humidity control in a conditioned environment and must be reduced to acceptable levels. Desired temperature and/or humidity control in the conditioned environment can be achieved by reducing the pressure fluctuations described above. Another potential problem associated with pressure fluctuations in refrigerant systems is the introduction of undesirable, sometimes excessive, pressure fluctuations and vibration of various system components that often lead to component failure. High vibration levels can also produce undesirable noise. In this case, the reduction in vibration level can be achieved by coupled feedback taken from the operation of the valve 30 (or 310) and the electronic expansion valve 26. The feedback controller can establish the most appropriate operation of these components by means of the input from the vibration sensor 44. The vibration sensor 44 can be installed at a specific location in the refrigeration system. For example, a vibration sensor 44 can be mounted on the discharge line 42, and an electrical signal corresponding to the vibration level of the vibration sensor can be communicated to the controller 32 (or 312).

The present invention thus solves the above-described problem of overpressure fluctuations on the high and low pressure sides of a refrigeration system without the need for any additional flow control devices or other additional hardware.

Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims

1. A refrigeration system comprising:

2. The refrigeration system of claim 1, wherein the expansion device is an electronically controlled expansion device.

3. The refrigeration system of claim 1, wherein a suction modulation valve is located between the second heat exchanger and the compressor, and the suction modulation valve is controlled to rapidly open and close to regulate the flow of refrigerant to the compressor between the high-flow and low-flow positions.

4. The refrigeration system of claim 1, wherein the compressor is a scroll compressor and has a back pressure chamber that rapidly cycles between high and low pressure conditions to vary the output of the compressor between the high and low flow positions.

5. The refrigeration system of claim 1, wherein the expansion device is moved to a fully closed position when the compressor is in the low flow position.

6. The refrigerant system as set forth in claim 1, wherein the pulse width modulation cycle time is between 2 and 30 seconds.

7. The refrigeration system of claim 1, wherein the expansion device is in the closed position for a time different than a time when the compressor is in the low flow position.

8. The refrigeration system of claim 7, wherein the time difference between the time the expansion device is in the closed position and the time the compressor is in the low flow position is between 1 and 3 seconds.

9. The refrigeration system of claim 1, wherein the time that the expansion device is in the closed position is delayed relative to the time that the compressor is in the low flow position, and the time that the expansion device is in the open position is delayed relative to the time that the compressor is in the high flow position.

10. The refrigeration system of claim 9, wherein the delay is between 1 and 3 seconds.

11. The refrigerant system as set forth in claim 1, wherein vibration on at least one component in the refrigerant system is monitored, and said monitored vibration is used to adjust at least one operating parameter of at least one of a pulse width modulated expansion device and a pulse width modulated refrigerant flow to said compressor.

12. The refrigeration system of claim 1, wherein a pressure fluctuation controller is provided for tightly maintaining at least one of temperature and humidity in the environment to be conditioned.

13. The refrigeration system of claim 1, wherein the pulse width modulation of the expansion device and the pulse width modulation of the amount of refrigerant flowing to the compressor are provided to control and limit pressure fluctuations in the first heat exchanger, the second heat exchanger, or both the first and second heat exchangers.

14. A method of operating a refrigeration system comprising:

15. The method of claim 14, wherein a suction modulation valve is located between the second heat exchanger and the compressor, and the suction modulation valve is controlled to rapidly open and close to regulate the flow of refrigerant to the compressor between high and low flow positions.

16. The method of claim 14, wherein the compressor is a scroll compressor and has a back pressure chamber that cycles rapidly under high and low pressure conditions to vary the output of the compressor between the high and low flow positions.

17. The method of claim 14, wherein the expansion device is moved to a fully closed position when the compressor is in the low flow position.

18. The method of claim 14, wherein the pulse width modulation cycle time is between 2 and 30 seconds.

19. The method of claim 14, wherein the time that the expansion device is in the closed position is different than the time that the compressor is in the low flow position.

20. The method of claim 19, wherein the time difference between the time the expansion device is in the closed position and the time the compressor is in the low flow position is between 1 and 3 seconds.

21. The method of claim 14, wherein the time that the expansion device is in the closed position is delayed relative to the time that the compressor is in the low flow position, and the time that the expansion device is in the open position is delayed relative to the time that the compressor is in the high flow position.

22. The method of claim 21, wherein the delay is between 1 to 3 seconds.

23. The method of claim 14, wherein vibration on at least one component in the refrigerant system is monitored, and the monitored vibration is used to adjust at least one operating parameter of at least one of a pulse width modulated expansion device and a pulse width modulated refrigerant flow to the compressor.

24. The method of claim 14, wherein the pressure fluctuation controller is provided to tightly maintain at least one of temperature and humidity in the environment to be conditioned.

25. The method of claim 14, wherein the pulse width modulation of the expansion device and the pulse width modulation of the amount of refrigerant flowing to the compressor are provided to control and limit pressure fluctuations in the first heat exchanger, the second heat exchanger, or both the first and second heat exchangers.

26. A refrigeration system comprising:

27. A refrigeration system comprising:

the compressor is a scroll compressor and has a back pressure chamber that is rapidly cycled using a pulse width modulated controller to vary the output of the compressor between high and low flow positions under high and low pressure conditions, and the expansion device is also controlled by pulse width modulation, the expansion device being moved significantly toward a closed position when the compressor is in the low flow position and toward an open position when the compressor is in the high flow position.