Patent Application
20060196219
The invention relates to accumulators for air-conditioning systems and is particularly concerned with filters for accumulators.
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, valve, tube, or other restriction divides the system into high and low-pressure sides. The liquid on the high-pressure side passes through the restriction and expands at least partly to gas, hence the general term for the restriction is “expansion device”. Some systems operate in “transcritical” mode, in that the hot refrigerant is merely cooled in the 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 possible to evaporate all the liquid the compressor is capable of supplying to the evaporator. Further, excess refrigerant is typically added to the system during manufacture to compensate for unavoidable leakage during the working life of the system. However excess liquid refrigerant entering the compressor (known as “slugging”) causes system efficiency loss and can damage the compressor. Hence it is standard practice to include a reservoir, called a suction line accumulator or simply an accumulator, between the evaporator and the compressor to separate and store the excess liquid.
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. In current standard use many accumulators use a variation of a dome deflector (as shown in, for example, U.S. Pat. Nos. 4,474,035 and 4,111,005), usually because they are simplest and most cost-effective. However, there are some designs of accumulators that do not use deflectors.
Some accumulators are designed to reduce the pressure drop across the accumulator (an important system performance parameter).
Certain accumulators incorporate a desiccant. Some refrigerant systems are more susceptible to moisture ingression and damage than others, especially less modern systems. However, for most systems, it is necessary to remove any moisture. The accumulator is a convenient location to house a desiccating element. Typical modern desiccant containers for this purpose incorporate a porous fabric bag of some suitable shape, containing beads of desiccating material like alumino-silicate zeolite, and secured to some inner feature of the accumulator, such as a J-tube, for example, at a position where the beads will contact the liquid refrigerant.
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 an oil 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. Various different designs having various tubes, shapes, and configurations have been attempted to return this oil to circulation with the minimum amount of oil inventory left in the accumulator. One design incorporates a J-shaped outlet tube, or J-tube or U-tube, to carry the exiting gaseous refrigerant from the top of the accumulator down to the bottom and then back up to an outlet from the accumulator. A carefully sized orifice or hole at the bottom of this J-tube entrains the oil from the bottom of the liquid area into the stream of exiting gas. A different style replaces the J-tube with a plastic liner (sometimes referred to as a liner-style accumulator) to effect the oil return function.
Generally the oil return hole has a coarse filter around it to prevent detritus from clogging the hole. The filter on the oil return hole may prevent large particles from returning to the compressor, but only those particles large enough to settle out of the gas stream and into the reservoir will be filtered by the coarse filter. Particles small enough to remain entrained in the gas flow during passage through the accumulator would bypass the filter on the oil return hole.
As suggested above, one of the functions of an accumulator is to separate gaseous refrigerant and oil from liquid refrigerant. The combination of structures in each type of accumulator for performing such separation may be referred to as a separator or separation means. Some specific types of separators are described herein. Sometimes a deflector and/or other means are used to separate gaseous refrigerant from both liquid refrigerant and oil. Such means may also be referred to as a separator or separator means. Many different types and designs are possible, as is known to those skilled in the art.
Further, the functions of an accumulator, such as separating fluid as described above, and possibly adsorbing moisture from some or all of the fluid, may be referred to as processing of a fluid.
As compressors in mobile air-conditioning systems are becoming more sophisticated, they are also becoming susceptible to damage from particulate matter entering the compression chambers. Hence it would be desirable to be able to achieve 100% filtration of the refrigerant. In some cases, filtration is performed by filters on the high pressure side, generally incorporated into the expansion device (ie: an orifice tube and a thermal expansion valve). However, these filters are not fine enough for current requirements, nor do they stop particles that originate between the expansion device and the compressor inlet. It would be desirable to place a filter immediately before the compressor. However it is well known that the performance of air-conditioning systems deteriorates with decreasing conductance of the lines connecting the evaporator to the compressor, that is, with increasing suction line pressure drop. Hence installing a suction line filter decreases system performance.
The pressure drop across a filter relates most strongly to the restriction in open area, due to both the area occluded by the solid components forming the matrix that provides the filter pores, and to the area occluded should the pores become clogged by detritus removed from the flow by the filter. Hence there is a need for a filter with a relatively large open area to reduce the negative impact upon system performance. As suggested above, historically, only small filters with a small open area have been installed in fittings, connections, or ports of components (for example on the compressor inlet port), because adding another, separate component to the system would cause an undesirable cost and increase complexity, especially if the component is a large filter in a canister. Accordingly, it would be desirable to have 100% filtration of the suction line that does not impede flow greatly and does not add excessive cost, complexity, or components.
According to one aspect, the invention provides an accumulator for an air conditioner or HVAC system comprising a filter for filtering substantially separated gaseous refrigerant and oil. The filter is adapted to ensure that any fluid exiting the accumulator has been filtered, without greatly impeding flow or adding excessive cost, complexity or components.
Embodiments of the invention may be used in vehicles.
According to another aspect, the invention provides an accumulator for an air conditioning system for processing a fluid, the fluid comprising gaseous refrigerant, liquid refrigerant and oil, the accumulator comprising a separator means for substantially separating the gaseous refrigerant and the oil from the liquid refrigerant, and a filter for filtering the substantially separated gaseous refrigerant and the oil, whereby the filter is adapted to ensure that all fluid exiting the accumulator has been filtered.
According to yet another aspect, the invention provides an accumulator for an air conditioning system for processing a fluid, the fluid comprising gaseous refrigerant, liquid refrigerant and oil, the accumulator comprising a separator means for substantially separating the gaseous refrigerant from remaining fluid, wherein the remaining fluid comprises oil and liquid refrigerant; a first filter for separately filtering the separated gaseous refrigerant; and a second filter for filtering the oil; wherein the first filter and the second filter ensure that all fluid exiting the accumulator has been filtered.
Different embodiments of the present invention may permit some of the following benefits:
providing filtration of 100% of the refrigerant exiting the accumulator;
providing separate filtration of gaseous refrigerant from liquid refrigerant;
providing filters which are relatively easy to secure within an accumulator;
providing filters that may be easily inserted by hand, if necessary;
overcoming a problem if a filter is used downstream from an oil bleed hole in a liner-style accumulator; historically, in such cases, particles that are removed by the filter may fall off the filter and collect around the oil bleed hole, thereby clogging the oil bleed hole; however, in certain embodiments of a liner-style accumulator described herein, particles falling from a filter located downstream from the oil bleed hole would not collect around the oil bleed hole and therefore would not prevent flow through it;
similar to the previously mentioned benefit, embodiments herein where the filter is located in an outlet tube, downstream from the oil bleed hole, may be “self-cleaning” filters; as refrigerant passes through the filter, particles are left on the underside of the filter; normal vibrations during operation may cause small particles to fall off the filter; because of the nature of the liner-style accumulator described herein, such particles would have no opportunity to plug the oil bleed hole;
providing filters that are easily manufactured;
providing filters with minimal effect on accumulator function, size, assembly, installation, cost, or complexity;
providing filters with a large surface area to provide minimal pressure drop, as flow through the filter can be distributed over the surface area of the filter.
Preferred embodiments of the invention will now be described with reference to the attached drawings in which:
a is a vertical sectional view of
b is a perspective view of
c is a partially exploded, sectional view of a portion of the accumulator of
d is a magnified view of the circled portion of
e is an exploded view of a portion of the accumulator of
a is a vertical sectional view of the accumulator of
b and 4c are perspective views of the filter of
a is a vertical sectional view of the accumulator of
b and 5c are perspective views of the filter of
a is a vertical sectional view of the accumulator of
b is a view looking down on the accumulator of
c is a perspective view of the deflector of
a is a vertical sectional view of the accumulator of
b is a partially exploded view of a portion of the accumulator of
c is a cross-sectional view along line 8c-8c of
d is a perspective view of the filter apparatus of
e is a magnified view of the circled portion of
a is a vertical sectional view of an accumulator in accordance with another embodiment of the present invention;
b is a perspective view of a portion of the accumulator of
c is a cross-sectional view looking up along line 9c-9c of
a is an exploded view of a J-tube style accumulator, in accordance with another embodiment of the present invention;
b is a partially exploded view of part of the accumulator of
c is a perspective view of the filter body separated from the cap of the accumulator of
d is a perspective view of the filter engaged over a part of the J-tube of
e is a perspective view of the assembled accumulator of
a is a perspective view of a reverse flow liner-style accumulator, in accordance with another embodiment of the present invention;
b is a vertical sectional view (except for the filter body) of the accumulator of
c is a different vertical sectional view of the accumulator of
A representative accumulator 10 is shown in
An outer container 14 of the accumulator 10 may be referred to as a can 14. The can 14 has a generally cylindrical shape, closed on its bottom end. A top portion 16 of the accumulator 10 is hermetically sealed to the can 14. The top portion 16 as shown in
The liner 12 sits within the can 14. The liner 12 is generally cylindrical. The circumference of the liner 12 is generally concentric with the circumference of the can 14. A bottom portion of the liner 12 curves inward and upward, to form a generally circular stop 24 (see
An outlet tube 34 extends through most of the height of the liner 12.
A desiccant cup 36 is shown near the bottom of the liner 12. The desiccant cup 36 contains desiccant 38. The desiccant cup may incorporate a filter or screen (not shown) to protect the oil bleed hole from clogging. The desiccant cup 36 has a central opening 40 (perhaps best seen in
In this embodiment, an upper portion of the outlet tube 34 extends into a filter housing 42. The filter housing 42 includes an upper portion 44 and a lower portion 46. A filter 50, as will be described in greater detail below, is housed within the filter housing 42 between the upper portion 44 and the lower portion 46.
A deflector 52 is shown in
As suggested above, in the embodiment of
There are many different ways to secure a filter within a filter housing. In this embodiment, as shown in
As suggested above, the periphery 74 of the filter 50 is snap fit between the upper portion 44 of the filter housing 42 and the lower portion 46 of the filter housing 42. However, there are an infinite number of different means possible for securing the filter 50 within a filter housing, as are well-known to those skilled in the art, including different techniques for snap fitting, gluing, ultra sonic welding, slip fitting, etc.
The filter 50, as shown in
As noted above, the top portion of the outlet tube 34 fits within the circular lower opening 65 of the lower portion 46 of the filter housing 42. The outlet tube 34 could also be manufactured integrally with the lower portion 46 of the filter housing 42.
The deflector 52 incorporates a number of passageways or chimneys 82. Each chimney 82 has a raised liquid protection barrier 83, to prevent liquid from entering the chimney 82.
In operation, when the accumulator 10 is completely assembled, refrigerant enters the inlet opening 20 and impinges upon the deflecting surface 56 of the deflector 52. The refrigerant is directed towards one of the semi-circular openings 62 and is then directed downward, inside the liner 12. Gaseous refrigerant moves back upward, through the chimneys 82 in the deflector 52, and then travels down the gap 32 between the can 14 and the liner 12 and then flows under the bottom of the liner 12 and into the outlet tube 34.
Liquid refrigerant flows through a somewhat different path. Liquid refrigerant (which also includes oil) after passing through the semi-circular openings 62 in the deflector 52, flows down the inside of the liner 12 to the desiccant cup 36. The liquid refrigerant and oil pass through the desiccant cup 36, with moisture within the fluid being adsorbed by the desiccant 38. In general, the liquid refrigerant remains on or near the floor of the liner 12 unless it passes through an oil bleed hole (not shown). The oil, in this embodiment, flows through the oil bleed (or oil return) hole (not shown) located at or near a low point in the liner 12. The oil that flows through the oil bleed hole becomes entrained in the flow of gaseous refrigerant and is carried up the outlet tube 34 with the gaseous refrigerant. The gaseous refrigerant with the entrained oil passes through the filter 50 and then up and out the outlet opening 22. Although a small amount of liquid refrigerant may pass through the oil bleed hole, the gaseous refrigerant remains substantially separated from the liquid refrigerant.
The path through the accumulator 10 taken by fluid flowing from the oil bleed hole to the outlet opening 22 may be referred to as an outlet passage. In the embodiment of
The flow of the fluid through the accumulator 10 determines whether one element is upstream or downstream from another element. For example, the outlet tube 34 is downstream from the gap 32. The oil return hole is upstream from the outlet tube 34.
Another embodiment is shown in
Another embodiment is shown in
Another embodiment is shown in
While the embodiments of
Another embodiment is shown in
In this embodiment, the filters 106 are located upstream from where oil is entrained with the gaseous refrigerant. Accordingly, a separate filter (not shown) is located in or near the oil return (or oil bleed) hole (not shown) which filters the oil.
Another embodiment is shown in
The deflector 52 of this embodiment, as perhaps best shown in
As shown in
When the accumulator of the embodiment of
In operation, after the gaseous refrigerant flows through the chimneys 82 in the deflector 52, the refrigerant then flows down the gap 32 between the liner 12 (or the deflector 52) and the can 14. Accordingly, the gaseous refrigerant flows through the filter 116. In this embodiment, similar to the embodiment of
In the embodiment of
Another embodiment is shown in
The accumulator 130 of
A filter 146 is secured across an inner cross-section of the deflector 142. The filter 146 is advantageously secured at or near a bottom portion of the deflector 146, and in any event, below or upstream from the entrance 141 of the outlet tube 140. The filter 146 is generally flat, having a periphery 150 and support bars 152.
A hollow pick-up tube 154 is secured to the outlet tube 140, so that an inner passage of the pick-up tube communicates with the outlet tube 140. A hollow reservoir or filter holder 156 is secured to a lower end of the pick-up tube 154. The filter holder 156 has an inlet (not shown) having its own filter (not shown).
In operation, refrigerant and oil enter the accumulator 130 of
Another embodiment is shown in
In operation, fluid enters the accumulator 200 through the inlet opening 206, and hits the deflector 226, which helps to separate gaseous refrigerant from liquid refrigerant and oil. The liquid refrigerant and oil are directed towards the liner 212 and then flow downward due to gravity, through the desiccant cup 216 to the bottom of the liner 212.
The gaseous refrigerant, upon separating from the liquid fluid, flows through the mesh screen of the filter body 224 and then into and down the gas flow tube 222. The gas then flows into and up the gap 214 and then out the outlet opening 210. As gaseous refrigerant flows past the oil bleed hole, oil (and perhaps some liquid refrigerant) is entrained within the flow of gas. The oil is filtered prior to exiting the oil bleed hole.
Although the embodiments described above relate to certain liner-style accumulators, the concepts described herein could also be implemented in other types of liner-style accumulators as well as non-liner-style accumulators, including J-tube (or U-tube) style accumulators, among others. In the case of J-tube-style accumulators, a filter could be located in the inlet or outlet of a J-tube. Moreover, a filter could also be located in an inlet port or outlet port of an accumulator of any style.
An embodiment of a J-tube (or U-tube) style accumulator is shown in
b is a partially exploded view of the deflector 170, the filter body 164 and the J-tube 162. As shown in this view, the J-tube 162 has an oil bleed (or oil return) hole 180, advantageously located near a lower section of the J-tube 162. The oil bleed hole 180 may incorporate an oil bleed filter (not shown). In the embodiment shown in
c is an exploded perspective view of the filter body 164 separated from the filter cap 166. The filter body 164 has the top portion 190, ribs 192 and a mesh screen 194, secured to the ribs 192. The mesh screen 194 may be made of nylon, steel or any other suitable material. The filter body 164 and cap 166 may be made of a plastic material, such as nylon. The cap 166 may be shear fit and ultrasonically welded to the filter body 164 for a no-leak seal. Alternatively, the cap 166 may just be ultrasonically welded to the filter body 164 for a no-leak seal. The surface on the cap 166 that mates with the filter body 164 can have a joint detail (not shown) for the ultrasonic weld. One rib 192 of the filter body 164 may be wider than the other ribs 192 to hide the seam of the mesh screen (not shown).
d is a perspective view of a portion of the J-tube 162 engaged with the filter body 164. The inlet 174 of the J-tube 162 is inserted into the filter body 164 until it sits on several standoffs 196 which prevent over-insertion (or otherwise incorrect installation) of the J-tube and also prevents movement of the J-tube 162. The top 190 of the filter body 164 may be a solid section which may press up against a bottom or lower surface of the deflector 170. Alternatively, as suggested in
e is a perspective view of the assembled accumulator of
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 practised otherwise than as specifically described herein.
