Patent Application
20060196223
The invention relates to suction accumulators for refrigeration or air/conditioning system use.
Closed-loop refrigeration systems conventionally employ a compressor that is meant to draw in gaseous refrigerant at relatively low pressure and discharge hot refrigerant at relatively high pressure. The hot refrigerant condenses into liquid as it is cooled in a condenser. A small orifice or valve divides the system into high and low-pressure sides. The liquid on the high-pressure side passes through the orifice or valve and turns into a gas in the evaporator as it picks up heat. (Some systems operate in “transcritical” mode, in that the hot refrigerant is merely cooled in a high side heat exchanger, now termed a “gas cooler”, and turns to gas plus liquid as it passes through the expansion device.) At low heat loads, it is not desirable or possible to evaporate all the liquid in the evaporator. However, excess liquid refrigerant entering the compressor (known as “slugging”) causes system efficiency loss and can cause damage to the compressor. Hence it is standard practice to include a reservoir between the evaporator and the compressor to separate and store the excess liquid. It is also a reservoir for excess refrigerant, which is typically added to the system during manufacture to compensate for unavoidable leakage during the working life of the system. This reservoir is called a suction line accumulator, or simply an accumulator.
An accumulator is typically a metal can, welded together, and often has fittings attached for a switch, transducer and/or charge port. One or more inlet tubes and an outlet tube pierce the top, sides, or occasionally the bottom, or attach to fittings provided for that purpose. The refrigerant flowing into a typical accumulator will impinge upon a deflector or baffle intended to reduce the likelihood of liquid flowing out the exit, generally by removing kinetic energy from the liquid so it settles quietly into the reservoir area without churning or splashing.
A consequence of using a suction line accumulator is that compressor oil can become trapped within it. Compressor oil is circulated with the refrigerant in most systems in current usage. Even if a separator is used, a small amount of oil escapes into the system. This oil will find its way into the accumulator, and while liquid refrigerant may be expected to evaporate and return to circulation as needed, the oil does not evaporate. Some means must be provided to return this oil to circulation. A known practice is to use a J-shaped outlet tube to carry the exiting gaseous refrigerant from the top of the accumulator down to the bottom and then back up to the outlet from the accumulator. A carefully sized orifice at the bottom of this “J-tube” entrains the oil from the bottom of the liquid area into the stream of exiting gas. Generally, the orifice has a filter around it, and the filter may extend into a sump formed in the bottom of the accumulator to collect the oil-rich liquid. The. J-tube also typically has a hole near the top, which prevents the liquid from siphoning or flowing out of the accumulator reservoir when the system is switched off. The size of the hole is a balance between breaking any siphon and reducing the effectiveness of oil pickup.
A recent development in accumulator design is to incorporate a plastic liner in the accumulator to assist with the oil pick up function (as shown, for example, in U.S. Pat. No. 06,612,128, U.S. Pat. No. 06,463,757). However, existing designs and literature do not teach how to optimize or improve the oil entraining function, especially for those cases where the refrigerant flow is the reverse of the flow in most previous accumulators using liners.
While previous accumulator designs have sought to return oil to the compressor, the previous designs do not appear to have considered improving the rate at which oil is returned to the compressor. As well, it would also be desirable to increase the amount of oil returned to the compressor and reduce the amount of liquid refrigerant flowing to the compressor.
According to one embodiment of the present invention relating to a liner-style accumulator, one or more vanes may protrude from an outer surface of the liner, from or near an oil bleed orifice and extend upward towards an outlet. The vanes provide a path or channel for the oil exiting the oil bleed orifice to follow towards the outlet of the accumulator. Gaseous refrigerant with metered liquid will then exit the accumulator through the outlet.
Embodiments of the accumulators and related designs described herein may be used in air conditioning systems within vehicles. Embodiments of the accumulators and related designs described herein could also be used in stationary commercial or industrial air conditioning systems.
According to a further aspect, the invention provides an accumulator for an air conditioning system comprising an outlet, a passage for oil to travel towards the outlet, an orifice to allow oil to enter the passage, and one or more oil vanes projecting from a surface of the passage, but not projecting across the passage, the one or more oil vanes extending from or near the orifice towards the outlet.
According to a further aspect, the invention provides an accumulator for an air conditioning system comprising an outlet, a passage for oil to travel towards the outlet, an orifice to allow oil to enter the passage, and one or more indentations formed within a surface of the passage, the one or more indentations extending from or near the orifice towards the outlet.
Advantageously, different embodiments of the present invention may provide some of the following: an accumulator having a liner, where the liner has vanes to help direct oil to an outlet which may allow for the size of an oil bleed orifice to be reduced, which thereby reduces the amount of liquid refrigerant entering the compressor, which thereby improves system performance; an accumulator which more efficiently returns oil to the compressor; an accumulator which returns oil to the compressor at a more predictable rate; an accumulator which returns more oil to the compressor with proportionally less liquid refrigerant; an accumulator providing improved performance; an accumulator which is more cost-effective.
Preferred embodiments of the invention will now be described with reference to the attached drawings in which
a is a perspective view of a liner-style, side-in-side-out (SISO) accumulator (with some of the internal components shown in dotted outline) in accordance with an embodiment of the present invention;
b is a vertical sectional view of the accumulator of
c is an exploded view of the accumulator of
An embodiment of an accumulator 20 is shown in
Within the accumulator 20 depicted in
As shown in
In this embodiment, the liner ribs 54 and the oil vanes 56 extend longitudinally upward along the outer surface 46 of the liner 36. However, the liner ribs 54 and the oil vanes 56 could also extend upward in a helical fashion (not shown) or in another fashion.
The accumulator 20 is assembled as generally suggested by
The gas flow tube 28 is then inserted through the opening formed within the desiccant container 44. The outer diameter of the gas flow tube 28 is sized such that it is slightly smaller than the inner diameter of the opening formed within the desiccant container 44, but still forms a tight seal between the two surfaces.
The deflector 40, in this embodiment, is secured to the ceiling of the top canister 22.
The liner 36 is then placed within the bottom canister 24. There is a gap or passage between an inside surface of the bottom canister 24 and the outer surface 46 of the liner 36 defined (in this embodiment) by the extent to which the liner ribs 54 project from the outer surface 46.
The top canister 22 is secured to the bottom canister 24. The top canister 22 and the bottom canister 24 may be made of aluminum or steel, for example, and welded together to form a hermetic seal.
In this embodiment, the top of the liner 36 extends to the ceiling of the top canister 22. The hole 48 in the liner 36 is oriented in line with the inlet tube 28. The inlet tube 28 passes through the hole 48 in the liner 36 (or the inlet tube 28 is sealingly secured to the hole 48 in the liner 36).
In operation, fluid enters the accumulator 20 through the inlet tube 28. The fluid passes through the hole 48 in the liner 36. The arrows shown in
Meanwhile, the gas flows towards the gas flow tube 42. The gaseous refrigerant flows into the entrance of the gas flow tube 42 and then down the gas flow tube 42. After leaving the gas flow tube 42, the gaseous refrigerant then flows through the gap between the liner 36 and the bottom canister 24. Accordingly, the gas flows below the liner 36 and then up to the outlet fitting 30, whereupon, the gaseous refrigerant exits the accumulator though the outlet conduit (not shown). As the gaseous refrigerant flows past the oil bleed orifice 52 near the nadir of the liner 36, oil (and possibly some liquid refrigerant) passes through the oil bleed orifice 52 and is entrained within the flow of gaseous refrigerant. As well, the oil vanes 56 provide a direct path between the oil bleed orifice 52 and the outlet fitting 30. The oil vanes 56 improve the flow of oil from the oil bleed orifice 52 up the liner 36. When oil exits the oil bleed orifice 52 it is immediately contained in the oil vanes 56 and is channeled up the side of the liner 36 by the passing gaseous refrigerant. The channeling effect helps maintain a constant and predictable stream of oil from the oil bleed orifice 52 to the outlet fitting 30. Some oil is entrained in the gaseous refrigerant and some oil is pulled up along or between the oil vanes 56 through suction or is dragged by the flowing gaseous refrigerant. The oil vanes 56 also help increase the amount of oil exiting the accumulator and thereby allow a reduction in the size of the oil bleed orifice 52. This, in turn, limits the amount of liquid refrigerant that exits the oil bleed orifice 52 and therefore limits the amount of liquid refrigerant entering the compressor.
In the above-noted embodiment, the oil vanes 56 extend or protrude from the outer surface 46 of the liner 36. Alternately, the oil vanes 56 could instead protrude or extend inwardly from an inner surface of the bottom canister 24.
The embodiments described above relate to a side-in-side-out (SISO) liner-style accumulator. However, the principles described above could also be applied to accumulators having other configurations, such as a top-in-side-out (TISO) accumulator or indeed other configurations as well as non-liner style accumulators.
For example, the oil vanes described above could be applied to a J-tube (or U-tube) style accumulator (not shown). The J-tube incorporates an orifice which permits oil to enter the J-tube. In the case of a J-tube style accumulator, oil vanes project inside the J-tube and extend from or near the orifice to or near an outlet. The interior of the J-tube may be referred to as a “passage.” The embodiments mentioned above describe oil vanes projecting from a surface. In another embodiment, the relevant surface could incorporate indentations or depressions instead of oil vanes. In that case, oil would flow along or within or would be directed by the oil indentation(s), toward the outlet.
The embodiments described above relate to liner-style accumulators and J-tube-style accumulators. However, the principles described herein could also be applied to other styles of accumulators including trumpet tube-style accumulators (which have a J-tube with a return down to the bottom of the accumulator (not shown)) and pick-up tube-style accumulators (not shown). In such cases, oil vanes or indentations would project within a passage (a J-tube, or a trumpet tube, or a pick-up tube, or a centre tube, etc.) and extend advantageously, from or near an orifice in the passage (where oil enters the passage) towards an outlet in the accumulator.
Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. For example, in the embodiments described above, an orifice is described as being formed within a surface, and projections or indentations extend along a particular surface to or near an outlet. Instead of the oil vanes or indentations extending along a single surface, the oil vanes or indentations could extend along two or more adjacent surfaces. Similarly, the oil vanes or indentations could be formed within a surface adjacent to a surface having the orifice, instead of the same surface having the orifice. Accordingly, when the term “surface” is used herein, it is intended to cover all of the alternative embodiments described herein.
