Patent ID: 12222143

These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

DETAILED DESCRIPTION OF THE INVENTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of example and not limitation with reference to the Figures.

FIG.1illustrates a vapor compression system100in accordance with embodiments of the disclosure. The vapor compression system100may include many other conventional features not depicted for simplicity of the drawings. Vapor compression system100is directed to refrigeration systems and may include chiller systems, and systems having a multiple stage compressor arrangement. Persons of ordinary skill in this art will readily understand that embodiments and features of this invention are contemplated to include and apply to, not only single stage compressor/chillers, but also to multistage compression chillers.

As shown, vapor compression system100includes a compressor10, a first heat exchanger (e.g., condenser)20, an expansion valve (not shown), a second heat exchanger (e.g., evaporator or cooler)30, a heat recovery heat exchanger (e.g., vaporizer)40, a heater42, and a sump reservoir50. Additionally, vapor compression system100also includes a controlled bypass system60that includes a first flow path62that permits a working fluid (e.g., refrigerant) and a non-refrigerant mixture to flow through an orifice64under certain operating conditions, and a bypass valve66, which when actuated by a controller230under certain other operating conditions, opens the bypass valve66to allow the mixture to flow through a second flow path69(which may include one or more check valve68). The compressor10, first heat exchanger20, second heat exchanger30, heat recovery heat exchanger40, sump reservoir50, and the controlled bypass system60are serially connected to form a semi- or fully-hermetic, closed-loop refrigeration system.

Vapor compression system100may circulate a working fluid to control the temperature in a space such as a room, home, or building. The working fluid may be circulated to absorb and remove heat from the space and may subsequently reject the heat elsewhere. The working fluid may be a refrigerant or a mixture of refrigerant and a non-refrigerant or a blend thereof in gas, liquid or multiple phases. As used herein, the term “first phase” refers to a vapor refrigerant/oil mixture which may be further characterized as a high pressure or low pressure mixture. High pressure flow is represented as a solid line flow path. In addition, the term “second phase” refers to a liquid refrigerant/oil mixture which is generally characterized as a low pressure mixture. Low pressure flow is represented by as a dashed line flow path.

The non-refrigerant may be a lubricant to lubricate mechanical components of the compressor10. Typically, the non-refrigerant is oil. Accordingly, in the present specification, the non-refrigerant in a liquid phase will be referred to as oil, but embodiments of the invention encompass any other type of non-refrigerant capable of performing the required lubricating functions. As shown in theFIG.1, the non-refrigerant is generally characterized as a low pressure fluid and is represented as a dashed line flow path from the outlet port130of the sump reservoir50to the inlet port136of the compressor10.

An exemplary compressor10is a screw compressor having a motor (not shown) with the capability to operate at varying speeds (e.g., VSD capability) and thus, the ability to operate under varying load conditions. Alternative compressors10are centrifugal compressors, scroll compressors, or reciprocating compressors. A first heat exchanger20has a vapor inlet port114downstream of compressor discharge port112. In operation, the compressor10compresses the working fluid to drive a recirculating flow of the working fluid through the vapor compression system100.

First heat exchanger20is a heater exchanger that removes heat from the first phase and transfers heat to a second heat transfer liquid (e.g., water or fluid mixture or air) running through the first heat exchanger20. The first heat exchanger20may include a float valve (not shown) which acts as an expansion device. Alternative implementations may include alternate expansion devices.

Downstream of the first heat exchanger20, is a second heat exchanger30. The second heat exchanger30is used to chill the second heat transfer liquid. For example, the working fluid passing through the second heat exchanger30may be in heat exchange relation with water to absorb heat from the water (to cool the water). As with the first heat exchanger20, the second heat exchanger30may represent any appropriate existing or yet-developed configuration. Additional second heat exchanger30ports cooperating with the heat recovery heat exchanger40and controlled bypass system60are discussed below.

An exemplary heat recovery heat exchanger40is comprised of a first portion40A which includes at least one conduit (e.g., one or more tubes or pipes) disposed within a shell referred to as the “second portion”40B. The first portion40A is in fluid communication with the compressor10, the controlled bypass60and the second heat exchanger30. The second portion40B is in fluid communication with the compressor10, the second heat exchanger30, and the sump reservoir50, each as described below.

The heat recovery heat exchanger40first portion40A receives a high pressure first phase via inlet port118from the first heat exchanger20. The at least one conduit isolates the high pressure first phase from the second phase in the second portion40B, such that the hot gas within the at least one conduit does not mix with the second phase within the second portion40B. As the high pressure first phase flows through the first portion40A, the first phase will immediately begin to be heated and boil and is useful as a supplemental heating source to the second phase that may collect in the second portion40B, discussed below. The first portion40A is also in fluid communication with an outlet120for discharging the high pressure first phase to the controlled bypass system60. The high pressure first phase flows through the controlled bypass system60where it is converted to a low pressure first phase and flows to the second heat exchanger30.

A controller (e.g., microprocessor based)230may control various operations of the vapor compression system100, including the compressor10, the heater42(which may be a multi-stage heater), and controlled bypass system60(including the bypass valve66), and may receive input from various sensors and user input devices. The controller230may have a memory configured to store at least one predetermined compressor operating load capacity limit or range, and a processor operably coupled to the memory. The controller230may be configured to be in communication with the controlled bypass system60and the compressor10. The controller230may be further configured to have stored therein, a predetermined compressor operating load capacity. The predetermined compressor operating load capacity may be a maximum or minimum operating load capacity limit or range. The controller230may be further configured to have a predetermined compressor operating load capacity limit or range such that the controller230actuates (opens) the normally closed bypass valve66under certain load operating conditions.

In one non-limiting embodiment, the controller230may be configured to receive a signal indicative of a compressor operating load capacity; to compare the compressor operating load capacity to at least one signal indicative of at least one of a predetermined compressor operating load capacity limit; and to actuate the bypass valve66if the operating load capacity is less than the at least one predetermined compressor operating load capacity limit.

In one non-limiting embodiment, when the operating load capacity of compressor10is equal to or greater than 25% of maximum operating load capacity, the bypass valve66remains closed causing the high pressure first phase to flow from the heat recovery heat exchanger40first portion40A along a first flow path62, and through a flow orifice64. It will be appreciated that in other embodiments the bypass valve66remains closed at an operating load capacity less than 25% of the maximum operating load capacity. The diameter of the flow orifice may vary. In one non-limiting embodiment, the orifice64has a diameter equal to or greater than 0.1875 inches and equal to or less than 0.3125 inches. The diameter of the orifice64aids in converting the working fluid from a high pressure first phase to a lower pressure first phase.

In another non-limiting embodiment, the controller230is configured to actuate (open) the bypass valve66upon receiving a signal from the compressor10that the operating load capacity of compressor10is less than 25% of maximum operating load capacity, allowing the high pressure first phase to flow via the first flow path62and a second flow path69. When the flow from the second flow path69converges with the flow from the first flow path62, the high pressure first phase is converted to a lower pressure first phase and enters the second heat exchanger30via inlet port122where it is in heat exchange relation with water as discussed above.

It should be apparent that the controlled bypass system60and controller230may have an alternate configuration or that the bypass valve may be normally open. For example, the controller230may be configured to actuate the bypass valve66upon receiving a fault signal (e.g., from compressor10) which may indicate a problem with the compressor10or other system failure. In this example, a fail-safe mode may enable low load operation.

In the second heat exchanger30, the working fluid continues to change phase. Some first phase will separate from the second phase and flow through outlet port124to the compressor10. Some second phase refrigerant flows through outlet port126entering the heat recovery heat exchanger second portion40B via inlet port128for separation.

In the heat recovery heat exchanger40, the low pressure second phase may separate into a vapor portion and an oil portion. The heat exchange between the first phase in the first portion40A and the second phase in the second portion40B further aids in vapor separation. The heat from the first portion40A will cause some liquid refrigerant to boil off, turning it to vapor. Vapor in the second portion40B will flow through an outlet port132and is returned to the compressor10via inlet port110. By configuring the heat recovery heat exchanger40to be in a heat exchange relation, the first portion40A provides supplemental heat to the second portion40B, thereby reducing the amount of heat that may otherwise be required to heat the second phase as discussed below.

The remaining second phase in the second portion40B of the heat recovery heat exchanger40will continue to undergo separation. Oil may separate from the refrigerant due to differences in specific gravities. In addition, a heater42may be applied to the second portion40B to further aide in separation. The heater42may also be in communication with controller230. For example, the heater42, configured with a thermal sensor, may be electrically coupled to the controller230and the second portion40B. The controller230may be further configured to determine at least one temperature limit or range of the second phase. If the measured temperature of the second phase in the second portion40B is less than or equal to a predetermined temperature limit or range, the heater42may turn on and apply heat until the measured temperature of the second phase is greater than or equal to another predetermined temperature limit or range. Because the thermal energy from the heat exchange provides some heating, the heater42may be used less, thereby increasing overall operating efficiencies.

The oil that collects in the second portion40B is discharged to the sump reservoir50. Oil in the sump reservoir50may be delivered to compressor10inlet port136via a pump (not shown) to lubricate mechanical components of the compressor10. After exiting the sump reservoir50through outlet port130, the oil may undergo filtration through a filtration system (not shown) before delivering the oil to compressor10. The sump reservoir50may also include a heating element (e.g., heater42) configured to heat the oil in the sump reservoir50to effectively evaporate any residual refrigerant from the oil and to keep the oil viscous, or to maintain a rich level of viscosity. In the present specification, “rich viscosity” refers to a level of viscosity necessary in oil provided to the compressor10or other parts to be lubricated that is sufficient to effectively lubricate the compressor10or other parts. In other words, the oil requires a certain minimum thickness or viscosity to be an effective lubricant.

Referring toFIG.2, a method for operating vapor compression system in accordance with the embodiments of the disclosure is shown.

The method begins with an operational vapor compression system100, such as a chiller system. The method begins at202with operating a compressor10to direct a working fluid (e.g., refrigerant) in a first phase through a first heat exchanger (e.g., condenser)20and a heat recovery heat exchanger40(e.g., vaporizer). The compressor10may include a screw compressor. The compressor10may also include single stage compressor/chiller, multi-stage compression chillers and single stage and/or multistage compressor chiller. The method may further include configuring the compressor to operate at variable speeds and loads. For example, the compressor10may having a motor (not shown) with the capability to operate at varying speeds (e.g., VSD capability) and thus, the ability to operate under varying load conditions. The “first phase” refers to a vapor refrigerant/oil mixture, while the “second phase” refers to a liquid refrigerant/oil mixture. In addition, the heat recovery heat exchanger40may have a first portion40A and a second portion40B.

The next step in the method204includes operating the heat recovery heat exchanger40to direct the working fluid in the first phase through a controlled bypass system60having at least one of an orifice64and a bypass valve66, to the second heat exchanger30. In this step, the first portion40A of heat recovery heat exchanger40receives a first phase from the first heat exchanger20through an inlet port118and directs the first phase through an outlet port120to the controlled bypass system60. The controlled bypass system60includes a first flow path62having an orifice64through which the first phase may flow; and a second flow path69having a normally closed bypass valve66which is in communication with a controller230configured to open bypass valve66under certain operating conditions.

Step206includes determining when the compression device10is operating below a predetermined operating capacity. In one non-limiting embodiment, the predetermined operating load capacity is 25% of maximum operating load capacity of the compressor10.

Step208includes operating the controller230to direct the working fluid in the first phase to a second heat exchanger30(e.g., evaporator or cooler) via a first flow path62when the compressor10operating load capacity is greater than a predetermined operating load capacity. In this step, when the compressor operating load capacity is greater than the predetermined operating load capacity, the controller230is configured to take no action, leaving the bypass valve66closed until it receives a signal (e.g., from compressor10) that a predetermined load operating limit has been reached. Until the predetermined load operating limit has been reached, the first phase will flow via the first flow path62and through orifice64to the second heat exchanger30.

Step210includes operating the controller230to direct the working fluid in the first phase to the second heat exchanger30by the first flow path62and a second flow path69. In this step, the controller230is in electrical communication with the bypass valve66and the compressor10. The controller230is configured to have stored therein at least one predetermined compressor10operating load limit or range. The controller230is further configured to actuate (open) the bypass valve66upon receiving a signal (e.g., from compressor10) that the load operating capacity of the compressor10is less than or equal to the predetermined load operating capacity. When the compressor10is operating at less than or equal to 25% of the maximum load operating capacity of the compressor10, the controller230operates to open bypass valve66, and the first phase is allowed to flow through the first flow path62and the second flow path69. It will be appreciated that in other embodiments the controller230operates to open the bypass valve66when the operating load capacity is greater than 25% of the maximum operating load capacity.

While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.