US20080250812A1

US20080250812A1 - Multi-Circuit Refrigerant System Utilizing Pulse Width Modulation Techniques

Info

Publication number: US20080250812A1
Application number: US12/088,954
Authority: US
Inventors: Alexander Lifson; Michael F. Taras
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2005-11-30
Filing date: 2005-11-30
Publication date: 2008-10-16
Also published as: HK1133067A1; EP1960717A4; CN101454620A; WO2007064320A1; EP1960717A1; CN101454620B

Abstract

A multi-circuit refrigerant system incorporates at least one component provided with a pulse width modulation control. This component can be controlled to adjust the capacity provided by the circuit incorporating the component. In this manner, the pulse width modulation component can be controlled to exactly tailor the capacity of that circuit to provide a total desired combined cooling capacity of the multiple circuits within the multi-circuit system configurations. In one embodiment, only one circuit in a multi-circuit refrigerant system incorporates a pulse width modulation controlled component. In another embodiment, a plurality of circuits are provided with pulse width modulation controlled components.

Description

BACKGROUND OF THE INVENTION

This application relates to multi-circuit refrigerant systems, wherein at least one component in one of the multiple circuits is provided with a pulse width modulation control to provide the ability to tailor capacity to environmental conditions and load requirements.
Refrigerant systems are utilized in many applications to condition an environment. In particular, air conditioning and heat pump units are employed to cool and/or heat air entering the environment. The cooling or heating load of the environment may vary with ambient conditions, occupancy level, other changes in sensible and latent load demands, and as the temperature and/or humidity set points are adjusted by an occupant of the environment.
Multi-circuit refrigerant systems are applied in the industry, wherein several independent circuits operate under a single control to provide various levels of sensible and latent capacity in response to the external load demands and wherein each circuit can independently function in one of several operational regimes.
Another optional feature available to a refrigerant system designer is the use of pulse width modulation controls. Pulse width modulation controls allow a component to be rapidly cycled on and off to control the capacity of the overall refrigerant system. As an example, it is known to rapidly open and close a valve to control the amount of refrigerant passing through the valve. Also, it is known to rapidly control other compressor components to vary the amount of refrigerant flow moved by the compressor.
However, multi-circuit refrigerant systems have not been provided with pulse width modulation controls.

SUMMARY OF THE INVENTION

In disclosed embodiments of this invention, multi-circuit refrigerant systems have at least one component in at least one of the circuits provided with a pulse width modulation control. The control can thus utilize the circuit having the pulse width modulation controlled component to fine-tune the overall system capacity.
In a disclosed embodiment, the pulse width modulation controlled component is a suction modulation valve controlling the amount of refrigerant passing to a compressor.
In other embodiments, multiple circuits are each provided with pulse width modulation controlled components. One of the components may be a suction modulation valve, and another component could be the compressor pump unit itself. Other components may be provided with the pulse width modulation control, as is also known.
By selectively switching the pulse width modulation controlled component on and off at a specified rate, the capacity provided by the circuit incorporating that component can be tailored to exactly meet desired overall system capacity requirements.
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.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first schematic.

FIG. 2 shows a second schematic.

FIG. 3 shows a feature of the FIG. 2 embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a refrigerant system 20 incorporating a first circuit 21 and a second circuit 22. Each circuit is provided with a compressor 24 compressing a refrigerant and delivering it downstream to a condenser 26, then to an expansion device 28. An evaporator 30 is positioned downstream of the expansion device 28. Refrigerant having passed through the evaporator 30 returns to the compressor 24.
The use of a multi-circuit refrigerant system is known in the prior art. The two circuits are controlled in combination with each other to adjust the amount of cooling and/or humidity removal provided into an environment to be conditioned. While various controls have been proposed in the prior art, there has been no simple control disclosed for fine-tuning the total capacity provided by the multiple circuits to exactly match desired capacity demands.
The FIG. 1 refrigerant system 20 does provide the ability to exactly tailor the overall capacity to a desired capacity by providing a suction modulation valve 32, which is controlled by a control 34 utilizing pulse width modulation techniques. Pulse width modulation techniques are known for various components within a refrigerant system. As an example, a prior United States patent by the assignee of this invention discloses pulse width modulation controls for a suction modulation valve, or other valves within a refrigerant system. However, as mentioned above, such controls have not been incorporated into a circuit in a multi-circuit refrigerant system.
The present invention provides greater control and the ability to exactly tailor a capacity, by allowing the combination of capacity delivered by the conventional circuit 21 and modulated capacity from the circuit 22. Thus, the control can exactly tailor the overall capacity provided by the refrigerant system 20.
FIG. 2 shows another embodiment 50 wherein there are multiple circuits 51 and 60. Each circuit is provided with a compressor 52, a condenser 54, an expansion device 56, and an evaporator 58. Circuit 51 is provided with a pulse width modulation control 59 for controlling the capacity provided by the compressor 52. As an example, it is known to rapidly open and close a valve to vary pressure forces holding two compressor components together, such as in a scroll compressor. By rapidly cycling this valve, the compressor components are allowed to move into and out of engagement with each other. When they are out of engagement with each other, little or no refrigerant is compressed and pumped into the refrigerant circuit, and thus the capacity is lowered.
The circuit 60 is similar to the circuit 22 in the FIG. 1 embodiment, and includes a suction modulation valve 62 provided with a pulse width modulation control 64.
The embodiment 50 of FIG. 2 preferably includes the circuits 51 and 60 having distinct component sizes such as, for example, the circuit 51 having twice the potential capacity of the circuit 60. In this manner, the two circuits can be utilized alone, or in combination to achieve a wide variety of capacity control. Moreover, the pulse width modulation techniques can be utilized to fine tune the capacity even further. While the FIG. 2 embodiment 50, as well as FIG. 1 embodiment 20, utilizes two distinct pulse width modulation control components, it would of course be within the scope of this invention to utilize multiple circuits having a similar component provided with a pulse width modulation control.
FIG. 3 shows an embodiment 301, schematically to illustrate how the scroll compressor can be modulated in a pulse width mode of operation. It is known that the orbiting scroll member 302 and the non-orbiting scroll member 304 may be biased together by a gas pressure force in a chamber 306. Opening and closing the valve 310 controls the pressure in the chamber 306. As shown, the valve 310 communicates via line 308 with another pressure source that is at different pressure than pressure in the chamber 306. When the pressure in the chamber 306 is reduced below a certain level the scroll members will separate from each and the amount of refrigerant pumped by the compressor is then reduced. When the pressure in the chamber 306 is increased above a certain level the scrolls will come into contact with each other and then the normal compression process will resume. The valve 310 can be controlled by a pulse width modulation control 312. Thus, by modulating the pressure in the chamber 306, the two scroll members 302 and 304 can be allowed to periodically move away from, and into contact with, each other. It should be noted that the schematic shown in FIG. 3 is presented for an illustration purpose only. For example, instead of allowing the scroll 304 to move axially in and out of contact with the scroll 302, the scroll 302 can be allowed to move axially while the scroll 304 remains essentially stationary in the axial direction. Also, the valve 310 can be located internal or external to the compressor.
With either embodiment, a control can be easily designed to achieve a desired capacity. Pulse width modulation is used to achieve an exact desired capacity. The use and design of an appropriate pulse width modulation control is known. However, when such a control is used in a multi-circuit system, it provides powerful benefits in exact tailoring of system operation. It should be noted that the present invention could be applied to different types of compressors including (but not limited to), for example, scroll, screw, rotary and reciprocating compressors. It can also be applied in a variety of systems including, for example, commercial air-conditioning or heat pump rooftop systems, commercial chiller systems, residential air conditioning or heat pump systems, supermarket refrigeration systems, and container or truck-trailer refrigeration systems.
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 refrigerant system comprising:

a plurality of circuits, with each of said circuits including a compressor, a condenser, an expansion device, and an evaporator; and

at least one of said circuits having at least one component provided with a pulse width modulation control.

2. The refrigerant system as set forth in claim 1, wherein at least one of said plurality of circuits does not include a component with a pulse width modulation control.

3. The refrigerant system as set forth in claim 2, wherein said at least one component is a suction modulation valve.

4. The refrigerant system as set forth in claim 1, wherein at least two circuits each have a component with a pulse width modulation control.

5. The refrigerant system as set forth in claim 1, wherein said at least one component is a suction modulation valve.

6. The refrigerant system as set forth in claim 1, wherein said control of said at least one component is controlled to change the capacity of said compressor.

7. The refrigerant system as set forth in claim 6, wherein said control allows two scroll members to move into and away from contact with each other to adjust capacity.

8. The refrigerant system as set forth in claim 1, wherein at least one of said compressors is selected from the group comprising a screw compressor, a scroll compressor, a reciprocating compressor and a rotary compressor.

9. The refrigerant system as set forth in claim 1, wherein said system is utilized as part of one of a commercial air conditioning or heat pump system, a rooftop system, a commercial chiller system, a residential air conditioning or heat pump system, a supermarket refrigeration system, a container refrigeration system and a truck-trailer refrigeration system.

10. A method of operating a multi-circuit refrigerant system comprising the steps of:

1) providing a plurality of circuits, with each of said circuits including a compressor, a condenser, an expansion device, and an evaporator; and

2) operating at least one component in at least one of said circuits with a pulse width modulation control.

11. The method as set forth in claim 10, wherein at least one of said compressors is selected from the group comprising a screw compressor, a scroll compressor, a reciprocating compressor and a rotary compressor.

12. The method as set forth in claim 10, wherein said system is utilized as part of one of a commercial air conditioning or heat pump system, a rooftop system, a commercial chiller system, a residential air conditioning or heat pump system, a supermarket refrigeration system, a container refrigeration system and a truck-trailer refrigeration system.

13. The method as set forth in claim 10, wherein at least one of said plurality of circuits does not include a component with a pulse width modulation control.

14. The method as set forth in claim 13, wherein said at least one component is a suction modulation valve.

15. The method as set forth in claim 10, wherein at least two circuits each have a component operational with a pulse width modulation control.

16. The method as set forth in claim 10, wherein said at least one component is a suction modulation valve.

17. The method as set forth in claim 10, wherein said control changes the capacity of said compressor.

18. The method as set forth in claim 17, wherein the pulse width modulation allows two scroll members to move into and away from contact with each other to adjust capacity.

19. The refrigerant system as set forth in claim 1, wherein each of said plurality of circuits has its own dedicated compressor, condenser, expansion device, and evaporator.

20. The method as set forth in claim 11, wherein each of said plurality of circuits is provided with its own compressor, condenser, expansion device and evaporator.