Patent Application
20150184906
The embodiments disclosed herein relate generally to a refrigeration system. More particularly, the embodiments relate to preventing refrigerant migration to a compressor in, for example, a transport refrigeration system during an Off cycle of the refrigeration system.
A transport refrigeration system may use a vapor-compression type refrigeration system to control the temperature of an internal space of a transport unit, such as a temperature controlled trailer unit or a truck. The vapor-compression type refrigeration system is generally a closed circuit. A refrigerant can be compressed by the compressor and circulated in the closed circuit to transfer heat from the internal space of the transport unit to the outside environment. During operation, a user may set a target temperature point, i.e. a setpoint, for the internal space. In an On cycle of the refrigeration system, the compressor of the refrigeration system can keep operating until the target temperature point is reached. At that point, the refrigeration system may enter into an Off cycle, in which the compressor of the refrigeration system stops. When the temperature of the internal space exceeds a permitted deviation range from the target temperature point, the compressor can start up from the Off cycle and resume running. The refrigeration system can repeat the On and Off cycles to maintain the temperature of the internal space within the permitted deviation range. The refrigeration system can also be configured to be in the off cycle in other situations. For example, the refrigeration system can be in the Off cycle overnight and back to the On-cycle during the daytime.
Embodiments to prevent Off Cycle fluid migration to a compressor of a refrigeration system are described. The embodiments described herein may allow fluid, such as oil, from a crankcase sump of the compressor to flow into an anti-fluid migration apparatus positioned in-line within a suction line of the refrigeration system, and accumulate in the anti-fluid migration apparatus. The accumulated oil in the anti-fluid migration apparatus may form a fluid barrier or seal to prevent Off cycle fluid (such as refrigerant) migration from other components of the refrigeration system to the compressor through the suction line.
In one embodiment, a method to prevent Off cycle refrigerant migration may include turning off the compressor of the refrigeration system; directing a lubricant from the compressor to accumulate in an anti-fluid migration apparatus positioned in-line along a suction line of the refrigeration system so that the lubricant accumulated in the anti-fluid migration apparatus forms a fluid barrier or seal to prevent fluid from flowing to the compressor through the suction line; turning on the compressor; and directing the lubricant accumulated in the anti-fluid migration apparatus to flow from the anti-fluid migration apparatus to the compressor through the suction line.
In some embodiments, the method may include preventing a fluid flow through a conduit connected between the anti-fluid migration apparatus and the crankcase sump during an Off cycle.
In another embodiment, a refrigeration system with an anti-fluid migration apparatus to prevent Off cycle fluid migration is also provided. In some embodiments, the refrigeration system may have a crankcase sump that is configured to contain oil with an oil level plane when the refrigeration system is in an Off cycle. The crankcase sump may have an opening that is positioned below a minimal oil level plane and a suction line connected to the crankcase sump. In some embodiments, the refrigeration system may include an anti-fluid migration apparatus that has a trap positioned in-line along the suction line and a conduit. The trap may have a flow passage, at least a section of which is positioned below the minimal oil level plane in the crankcase sump. The conduit may have a first end and a second end. The first end may be in fluid communication with the flow passage and the second end may be in fluid communication with the opening of the crankcase sump.
In some embodiments, the refrigeration system may have a flow control device positioned in-line along the conduit between the first end and the second end. In some embodiments, the flow control device may have an “open” state that generally allows oil (or any other types of fluid) in the crankcase sump to flow to the trap through the conduit, and an “off” state that generally prevents an oil flow between the crankcase sump to the trap through the flow control device. In some embodiments, the flow control device may be in the “open” state when the refrigeration is in an Off cycle, and in the “closed” state when the refrigeration system is in an On cycle. In some embodiments, the flow control device may be an orifice in the conduit.
In some embodiments, the trap of the anti-fluid migration apparatus may be a U-shaped section of the suction line.
In yet another embodiment, a transport refrigeration system with an anti-fluid migration apparatus is provided. The anti-fluid migration apparatus may include a trap that has a flow passage positioned in-line along a suction line of the refrigeration system. The anti-fluid migration apparatus may also include a conduit having a first end and a second end. The first end of the conduit may be in fluid communication with the flow passage of the trap. The second end of the conduit may be in fluid communication with a crankcase sump of the compressor. The trap may be configured to receive fluid flowing through the conduit, and allow the fluid to accumulate in the trap in order to form a fluid barrier or seal to prevent fluid migration from components of the refrigeration system to the compressor through the flow passage.
In some embodiments, the conduit may be equipped with a flow control device that is positioned in-line between the two ends of the conduit. The flow control device may have an “open” state that generally allows oil in a crankcase sump of the refrigeration system to flow to the trap through the conduit, and an “off” state that generally prevents oil flow between the crankcase sump to the trap through the conduit. In some embodiments, the flow control device is in the “open” state when the refrigeration is in an Off cycle, and in the “closed” state when the refrigeration system is in an On cycle.
Referring now to the drawings in which like reference numbers represent corresponding parts throughout.
The embodiments described herein relate to preventing refrigerant migration to a compressor in a transport refrigeration system during an Off cycle of the refrigeration system.
In a refrigeration system, a lubricant, such as mineral or synthetic oil, is generally used to lubricate moving parts of the compressor. During an Off cycle of a refrigeration system, particularly during a long Off cycle (e.g. over 4 hours), a fluid such as a refrigerant in a vapor state may be driven into a crankcase sump of a compressor from other components of the refrigeration system, such as an accumulator. This fluid is driven into the crankcase sump at least due to the vapor pressure of the refrigerant being greater than that of a lubricant. In these embodiments, the refrigerant is in a liquid form when the refrigerant is in the crankcase sump.
The refrigerant migrated into the crankcase sump may dilute the lubricant in the crankcase sump and consequentially reduce the effectiveness of the lubricant. In some cases, it has been observed that the liquid refrigerant can completely fill the crankcase of the compressor during an Off cycle of the compressor. If the compressor starts up with an excessive amount of liquid refrigerant in the crankcase sump, the load on bearings and/or an Oldham coupling, as well as any moving parts of the compressor may increase. In some cases, the lubricant in the crankcase sump and the liquid refrigerant migrated into the crankcase sump may form two separated liquid layers during an Off cycle. In some cases, oil floats on the liquid refrigerant because the oil density may be less than the density of the refrigerant, and during startup the oil will be pumped out of the compressor. If the compressor starts up under such a condition, the lubricant inside the crankcase sump may drop below the minimal level required for the compressor to work properly after start up. This may cause bearings/Oldham coupling fractures and wear on the moving parts of the compressor.
In the following description of the illustrated embodiments, a method to prevent fluid migration, particularly prevent Off cycle refrigerant migration to a compressor from other components of a refrigeration system is described. In an Off cycle of the refrigeration system, the method described herein can direct a lubricant in the crankcase sump of the compressor to an anti-fluid migration apparatus to form a fluid barrier or seal in the suction line to prevent refrigerant migration. Further, during start up, the method described herein can direct the lubricant accumulated in the anti-fluid migration apparatus during the Off cycle to the compressor to provide lubrication to the compressor.
Moreover, an anti-fluid migration apparatus and a refrigeration system with an anti-fluid migration apparatus to prevent fluid migration, particularly prevent Off cycle refrigerant migration to a compressor from other components of a refrigeration system are described. The anti-fluid migration apparatus may generally have a trap and a conduit that allows oil (or other types of fluid) in the crankcase sump to flow from the crankcase sump to the trap during an Off cycle. The trap may be positioned in-line along a suction line of the refrigeration system, so that the oil flowing to the trap may form a fluid barrier or seal in the trap to prevent Off cycle refrigerant migration through the suction line. The oil in the trap may be directed to the compressor during start up to provide lubrication to the compressor.
References are made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration of the embodiments in which the anti-fluid migration apparatus may be practiced. The term “Off cycle” generally means that the compressor of the refrigeration system is off, or is not pumping/circulating the refrigerant. The term “On cycle” or “in operation” generally means that the moving parts of the compressor are in motion, or is pumping/circulating the refrigerant. The term “in-line” generally means “in fluid communication” or connected. In particular, if a device is positioned in-line along a pipe, it means that a fluid flowing from first end to the second end of the pipe will generally flow through the device. If not specified, a flow control device or a valve generally has an “open” state that generally allows fluid flow through the flow control device or the valve, and a “closed” state that generally blocks the fluid flow through the flow control device or the valve. It is to be understood that the terms referring to the different types of fluids in the refrigeration system, for example, “liquid refrigerant,” “vapor refrigerant,” “oil” and “lubricant” are exemplary and not meant to be exclusive. The refrigeration system may contain any other suitable types of fluid. In addition, it is to be understood that the terms are only referred to the main components of the fluid. For example, oil may contain some refrigerant contents, and the liquid refrigerant may contain some oil. It is also to be understood that the terms used herein are for the purpose of describing the figures and embodiments and should not be regarding as limiting the scope of the present application.
Embodiments as described herein can be generally used in a temperature controlled semi-trailer truck 100 as illustrated in
It will be appreciated that the embodiments described herein are not limited to trucks and trailer units. The embodiments described herein may be used in any other suitable temperature controlled apparatuses. The refrigeration system may be a vapor-compressor type refrigeration system, or any other suitable refrigeration systems that use refrigerant. The embodiments described herein can also be generally used in any type of lubricated mechanical compressor.
Referring to
It should be noted that the compressor of the refrigeration system may also be turned off by other methods or in other situations. In some embodiments, the compressor may be turned off by manually cutting off power supply to the compressor. In some embodiments, the compressor may be turned off, for example at night, then be turned on during the daytime.
During the Off cycle, at 204, a lubricant in the crankcase sump of a compressor is generally directed to an anti-fluid migration apparatus that is positioned in-line along a suction line of the refrigeration system.
The anti-fluid migration apparatus may be positioned between an accumulator and an inlet of the compressor. In some embodiments, the anti-fluid migration apparatus may have a side conduit that is connected to the crankcase sump of the compressor. The conduit may have a valve. During an Off cycle, the valve may be in an “open” state that allows the lubricant in the crankcase sump to flow to the anti-fluid migration apparatus through the conduit. The lubricant flowing to the anti-fluid migration apparatus can accumulate in the anti-fluid migration apparatus and/or the suction line, and is able to form a fluid barrier or seal in the anti-fluid migration apparatus that prevent refrigerant migration in the suction line from, for example, the accumulator to the inlet of the compressor. (Not shown.)
At 205, the refrigeration system remains in the Off cycle and waits for the On cycle. The compressor can be turned on for example by using the temperature control circuit. As shown in
At 207, when the compressor starts up, the lubricant accumulated in the suction line and/or the anti-fluid migration apparatus is directed into the inlet of the compressor via the suction line. The lubricant getting into the compressor may lubricate the compressor.
During the On cycle, at 208, the lubricant is generally prevented from flowing between the crankcase sump and the anti-fluid migration apparatus through the conduit connecting the crankcase sump and the anti-fluid migration apparatus. This can be accomplished by setting the valve on the conduit to a “closed” position. (Not shown.) It should be noted that 208 may be performed in the Off cycle too. For example, 208 may be performed right after the anti-fluid migration apparatus is filled with the lubricant from the crankcase sump at 204.
The conduit 322 has two ends. A first end of the conduit 322 is connected to a side opening 340 of the trap 320 as shown in
To facilitate the connection of the conduit 322 to the crankcase sump 330 of the compressor 308, a valve 307 may be equipped to the crankcase sump opening 317 as shown in
When the refrigeration system 300 is in operation, a bottom 315 of the compressor 308 is typically installed on a flat surface that is generally parallel to the frame on which the refrigeration system 300 rests, such as the trailer frame 130 as shown in
The top surface of the oil level, L1(on) or L1(off) (as discussed below) in the crankcase sump 330 defines an oil level plane 310 that is generally parallel to the trailer frame on which the refrigeration system 300 rests. The opening 317 of the crankcase sump 330 is generally positioned below the oil level plane 310 of L1(on). In some embodiments, the opening 317 may be positioned below a minimal oil level in the crankcase sump 330 when the refrigeration system 300 is in operation. The minimal oil level may be the minimal amount of oil required for the compressor 308 to perform properly. As shown in
Referring now to
The trap 320 is a U-shaped section of the suction line 301 between the accumulator 305 and the inlet 350 of the compressor 308 as shown in both
As shown in
The flow control device 321 may generally have an “open” state that allows a fluid flow through the flow control device 321, and a “closed” state that generally blocks the fluid flow through the flow control device 321. In the embodiment as shown in
In operation, when the refrigeration system 300 is in an On cycle as shown in
When the refrigeration system 300 enters an Off cycle (as shown in
When the refrigeration system starts up from the Off Cycle as shown in
Generally, as shown in
The trap 320 may generally be positioned so that a top of the conduit 322 is just below the minimal oil level in the crankcase sump 330. The position of the trap 320 may also be configured to avoid excessive oil accumulation inside the trap 320.
As shown in
If the orifice 423 is used, in some embodiments a small amount of oil may migrate from a crankcase sump 430 to a trap 420 when a compressor 408 is in operation, however the migrated oil may be sucked back into the compressor 408 through a suction line 401 and inlet 450. In some embodiments, the pressure difference between the pressure in the trap 420 and the pressure in the crankcase sump 430 may prevent an oil flow between the crankcase sump 430 and the trap 420 when the compressor 408 is in operation. During an Off Cycle, the oil 403 may flow to the trap 420 through the orifice 423 and accumulate in the trap 420 to act as a fluid barrier or seal until the compressor 408 resumes operation.
It is to be understood that components other than a crankcase sump of a refrigeration system can also provide a fluid that can accumulate in the trap and therefore prevent off cycle liquid migration. For example, in some embodiments, the refrigeration system may have an oil separator that includes an oil reservoir and is generally positioned downstream of a compressor in a suction line. The oil separator can be used to provide the oil to the trap and prevent off cycle liquid migration. It is also to be understood that some refrigeration systems may have multiple compressors. In a stationary multiple-compressor refrigeration system with a common manifold, the trap can be positioned upstream of the common manifold to prevent off cycle oil migration to one or more of the compressors.
It is appreciated the trap as described herein may be applicable to a refrigeration system with a suitable compressor, such as a reciprocating compressor, a scroll compressor and/or a screw compressor.
Any aspects 1-11 can be combined with any aspects 12-20. Any aspects 12-16 can be combined with any aspects 17-20.
a container of the refrigeration system configured to contain a fluid with a fluid level plane when the refrigeration system is in an Off cycle of the refrigeration system;
a refrigerant line;
a trap positioned in-line along the refrigerant line, the trap including a flow passage, at least a section of which is positioned lower than the fluid level plane in the container; and
a conduit in fluid communication with the flow passage and the container;
wherein the conduit is configured to allow fluid communication between the container and the flow passage of the trap when the refrigeration system is in an off cycle.
a flow control device positioned along the conduit.
wherein the flow control device has an “open” state that allows fluid communication between the container and the flow passage of the trap through the conduit, and an “off” state that prevents fluid communication between the container and flow passage of the trap through the flow control device.
a Schrader valve positioned between the container and the conduit, wherein the conduit is connected to the Schrader valve.
a refrigerant line;
a trap having a flow passage, the flow passage configured to be positioned in-line of the refrigerant line; and
a conduit in fluid communication with the flow passage of the trap and a crankcase of a compressor of the refrigeration system;
wherein the flow passage of the trap is configured to receive a fluid through the conduit, and allow the received fluid to accumulate in the trap so as to form a fluid barrier to prevent fluid migration through the flow passage of the trap.
during an Off cycle of the refrigeration system, directing a first fluid from a container of the refrigeration system to accumulate in a section of a refrigerant line of the refrigeration system; and
forming a fluid barrier in the section of the suction line with the first fluid accumulated in the section of the suction line to prevent a second fluid from flowing in the suction line.
during an On cycle of the refrigeration system, directing the first fluid accumulated in the section of the suction line to flow from the section of the suction line to the container through the suction line.
With regard to the foregoing description, it is to be understood that changes may be made in detail, especially in matters of the construction materials employed and the shape, size and arrangement of the parts without departing from the scope of the present invention. It is intended that the specification and depicted embodiment to be considered exemplary only, with a true scope and spirit of the invention being indicated by the broad meaning of the claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2013/054063 | 8/8/2013 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61681384 | Aug 2012 | US |
