Patent Application
20060225459
1. Field of the Invention
The invention relates generally to an air conditioning system for a motor vehicle. More specifically, the invention relates to an accumulator of such a system having an improved efficiency.
2. Related Technology
Currently-used air conditioning systems experience efficiency losses, a generally poor response time, and a potential risk of compressor damage. Generally, efficiency losses occur when a working fluid fails to completely undergo a phase change during one of the various stages of the air conditioning cycle, as will be discussed below in more detail. Response time refers to the delay between the time that an air conditioner operator turns on the system and the time that the system effectively cools the air flowing into the vehicle passenger compartment. The response time may be undesirably lowered by various factors or system configurations, as will also be discussed in more detail below. Also, compressor damage may occur if the working fluid fails to undergo the desired phase changes at the desired times.
Air conditioning systems known in the art typically include a plurality of components connected to each other in series to circulate a working fluid, such as refrigerant. One such air conditioning system 100, which is shown in
During operation of the system 100, the compressor 102 receives and compresses a refrigerant. Due to the natural uncompressible properties of liquids, the refrigerant received by the compressor 102 is preferably in a substantially gaseous state. In fact, the compressor 102 may be inadvertently damaged or destroyed if a substantial amount of liquid is permitted to enter the compressor 102. The compressor 102 is typically a pump driven by a belt that is connected to the engine of the motor vehicle. Therefore, the moving components of the compressor 102 often require a form of lubrication during operation. A lubricant, such as oil, is therefore typically mixed with the working fluid to properly lubricate the working components. The refrigerant exits the compressor 102 as a relatively high-pressure gas 114.
From the compressor 102, the high temperature, high pressure gas 114 flows through the first conduit 112 and into the condenser 104, where it becomes cooled through a heat exchange process with a secondary fluid, such as air flowing across the exterior of the condenser 104. After being condensed, at least partially, the high pressure liquid refrigerant 118 flows along a second conduit 116 to the expansion device 106, which regulates the amount of refrigerant that is permitted to flow therethrough. The expansion device 106 lowers the pressure of the refrigerant and allows a liquid/gas mixture of refrigerant 122 to flow into the evaporator 108 via a third conduit 120.
In the evaporator 108, the low pressure, low temperature liquid/gas mixture flows into a plurality of parallel heat transfer tubes (not shown). Ambient air, or air from the passenger compartment to be recirculated, flows across the heat transfer tubes and the relatively cool refrigerant 122 absorbs heat from the relatively warm air and is evaporated. The air is then passed into the passenger compartment of the vehicle. Thus the temperature of the air entering the passenger compartment is controlled by the compressor and/or the expansion valve. However, the liquid/gas mixture of refrigerant 122 may be unevenly distributed among the heat transfer tubes, thereby causing the air to be unevenly cooled and the refrigerant 122 to be unevenly evaporated. Therefore, a liquid/gas mixture of refrigerant 126 will exit the evaporator 108 via the fourth conduit 124. While the refrigerant 126 is typically mostly in a gaseous state, a relatively small amount of liquid state refrigerant is mixed therein.
From the evaporator 108, the refrigerant 126 flows into the accumulator 110 where it is separated into liquid and gas states. More specifically, the accumulator 110 is a reservoir that causes the refrigerant to separate into a gas portion 126a, located in the top of the accumulator 110, and a liquid portion 126b, located in the bottom of the accumulator 110. A fifth conduit 128, which leads to the compressor 102, includes an end 130 located in the top portion of the accumulator 110 such that only the gas portion 126a of the refrigerant is able to flow therein. As discussed above, a lubricant is preferably delivered to the compressor 102 from the accumulator 110. Therefore, the fifth conduit 128 also includes a U-shaped portion 132 extending into the liquid portion 126b and having an oil bleed hole (not shown) that draws oil therein from the liquid portion 126b. Along with the oil, a relatively small amount of the liquid portion 126b of refrigerant is drawn through the oil bleed hole. This liquid portion 126b is therefore evaporated in the compressor 102, rather than in the evaporator 108, reducing the overall efficiency of the air conditioning system 100.
After exiting the accumulator 110, the gas phase refrigerant 134 flows into the compressor 102, where the above-described cycle begins again.
When the air conditioning system 100 shown in
It is therefore desirous to provide an accumulator having improved efficiency, an improved response time, and has a reduced risk of compressor damage.
In overcoming the limitations and drawbacks of the prior art, the present invention provides an improved air conditioning system. The system includes an accumulator defining an accumulator chamber for receiving a fluid and permitting the fluid to separate into a gas state portion and a liquid state portion. A conduit, which defines a passageway for carrying fluid, extends through the housing and across the accumulator chamber such as to permit heat transfer between the accumulator chamber and the fluid in the conduit. To further promote the heat transfer, the conduit may extend in a serpentine path through the accumulator.
The conduit additionally defines a vapor bleed hole that permits fluid exchange between the conduit and the accumulator chamber. More specifically, the vapor bleed hole is positioned so as to be located in a top portion of the accumulator chamber so that the gas phase portion in the accumulator is permitted to flow through the vapor bleed hole into the conduit.
With the present air conditioning system, the evaporator is positioned downstream from the accumulator such that refrigerant flows from the accumulator to the evaporator; thereby reducing the response time of the air conditioning system.
Because the fluid flowing through the conduit is at a pressure that is less than that of the fluid in the accumulator chamber, the fluid in the conduit is superheated by the fluid in the accumulator chamber, thereby further improving the efficiency of the system.
Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification.
Referring now to
During operation of the system 10, the compressor 12 receives and compresses a refrigerant that is in a substantially gaseous state. The compressor 12 indudes a pump (not shown) that is driven by a belt connected to the engine of the motor vehicle. To minimize friction between the moving parts of the compressor 12, a lubricant, such as oil, is typically mixed with the working fluid. The refrigerant exits the compressor 12 via a first conduit 22 as a relatively high-pressure gas 24.
From the compressor 12, the high temperature, high pressure gas 24 flows into the condenser 14 and is cooled into a high-pressure liquid through a heat exchange process with a secondary fluid. More specifically, in the condenser 14 shown in
The expansion device 16 regulates the amount of refrigerant that is permitted to flow therethrough and substantially lowers the pressure of the refrigerant. The expansion device 16 shown in
The low pressure, low temperature liquid/gas mixture 38 then enters the accumulator 18 via an inlet 40 and separates into a gas phase portion 42 and a liquid phase portion 44 within an accumulator chamber 46 defined by the accumulator housing 47. More specifically, the accumulator chamber 46 acts as a reservoir for the refrigerant such that the different densities of the respective portions 42, 44 cause the refrigerant to separate. Obviously, the liquid phase portion 44 settles in the bottom portion of the accumulator 18 and the gas phase portion 42 rises to the top portion of the accumulator.
The accumulator chamber 46 also acts as a reservoir for the oil that is used to lubricate the compressor 12. In the design shown in
The liquid phase portion 44 flows through an outlet 48 of the accumulator chamber 46 and into a fourth conduit 50 that leads to the evaporator 20 to undergo heat exchange with a secondary fluid that will subsequently be provided to the passenger compartment of the motor vehicle. More specifically, in the evaporator 120 the liquid phase portion 44 of the refrigerant flows through a first header 56, into a plurality of heat exchange tubes 58, through a second header 60, and into a fifth conduit 54. While the liquid phase portion 44 of the refrigerant flows through the heat exchange tubes 58, ambient air flows across the heat transfer tubes and subsequently into the passenger compartment of the motor vehicle. Therefore, the relatively cool refrigerant absorbs heat from the relatively warm ambient air, thereby cooling the air and the passenger compartment if desired.
Because the refrigerant entering the evaporator 20 is typically a single phase fluid, the refrigerant is evenly distributed among the heat exchange tubes and the air is evenly cooled. Therefore, the undesirable temperature gradients that are described above with respect to evaporators currently used in the art are minimized or eliminated.
Furthermore, during the initial start-up of the air conditioning system 10, the refrigerant flows along a relatively short path from the fluid reservoir (the accumulator 18) to the heat exchange portion (the evaporator 20). Therefore, the air conditioner system 10 shown in
Due to the natural properties of fluids, the liquid phase portion 44 of the refrigerant is able to absorb heat during evaporation without increasing in temperature. In other words, the heat energy absorbed by the refrigerant causes evaporation rather than a temperature increase. Therefore, an output flow 62 of refrigerant that exits the evaporator 108 does not have a significantly higher temperature than the liquid phase portion 44 that enters the evaporator 20. More specifically, a pressure drop in the refrigerant as it flows through the evaporator 20 causes the output flow 62 to have a lower temperature than the liquid phase portion 44 that enters the evaporator 20, despite the heat that the refrigerant absorbs from the air.
The output flow 62 is mostly in a gas state when flowing away from the evaporator 20. However, to ensure that the refrigerant is superheated, and to “pre-cool” the refrigerant located in the accumulator chamber 46, the fifth conduit 54 extends through the accumulator chamber 46. More specifically, the fifth conduit 54 extends through the housing 47 passing through both the liquid phase portion 44 and the gas phase portion 42. In the conduit 54, the output flow 62 is kept separated from the refrigerant within the accumulator chamber 46, but heat exchange is permitted to occur between the respective fluids 62, 44. To further promote the heat exchange, the fifth conduit 54 includes a serpentine portion 70 that coils through or extends back and forth across the accumulator chamber 46.
As mentioned above, the output flow 62 has a lower pressure, and thus any liquid present will have a lower temperature than the liquid phase portion 44 of the refrigerant. Due to its lower pressure, the output flow 62 has a lower saturation temperature than the liquid portion 44 in the accumulator chamber 46. Therefore, when the temperature of the output flow 62 is raised by heat exchange with the liquid portion 44 in the accumulator chamber 46, the output flow 62 becomes superheated. Therefore, the refrigerant flowing along the passageway 68 is substantially superheated. Additionally, the liquid phase portion 44 in the accumulator 118 is cooled by the output flow 62 before reaching the evaporator 120 and is therefore able to more-effectively cool the air flowing across the evaporator 20.
After the output flow 62 flows through the serpentine portion 70 of the fifth conduit 54, it flows past the vapor bleed hole 52. Because the output flow 62 is at a lower pressure than the gas phase portion 42 of the refrigerant located in the accumulator 18, the output flow 62 is substantially prevented from flowing out of the vapor bleed hole 52. Likewise, due to the pressure differential, the gas phase portion 42 flows through the vapor bleed hole 52, which is suitably sized to permit such a flow.
At this point in the cycle, the refrigerant flowing from the evaporator 20 is united with the refrigerant that entered the fifth conduit 54 via the vapor bleed hole 52 to form a compressor supply flow 72. Because the refrigerant flowing along the passageway 68 is mixed with the oil, it is not necessary to draw any of the liquid phase portion 44 directly into the fifth conduit 54 as described above with respect to known designs. Furthermore, because the refrigerant flowing into the vapor bleed hole 52 is all or mostly evaporated fluid, the compressor supply flow 72 is all or mostly evaporated fluid; thereby reducing the possibility of damage to the compressor 12.
It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.
