Patent Application
20110146337
1. Field of the Invention
The present invention relates to an air conditioning system. More specifically, the present invention relates to an air conditioning system with an energy recovery device that extracts work from expanding refrigerant moving from a high-pressure zone to a lower pressure zone of the air conditioning system.
2. Background Information
A typical vehicle air conditioner includes a compressor, a condenser, an expansion valve and an evaporator. A typical automobile air conditioner includes a compressor, a condenser, an expansion valve, and an evaporator. The compressor compresses a cool vapor-phase refrigerant (e.g., Freon, R134a) to heat the same, resulting in a hot, high-pressure vapor-phase refrigerant. This hot vapor-phase refrigerant runs through a condenser, typically a coil that dissipates heat. The condenser condenses the hot vapor-phase refrigerant into liquid refrigerant. The liquid refrigerant is throttled through the expansion valve, which evaporates the refrigerant to a cold, low-pressure saturated liquid-vapor-phase refrigerant. This cold saturated liquid-vapor-phase refrigerant runs through the evaporator, typically a coil that absorbs heat from the air fed to the passenger compartment.
Vehicle air conditioning systems are continuously being re-designed and modified in order to improve energy efficiency of such systems. In this regard, one proposal to improve energy efficiency of a vehicle air conditioning system is disclosed in U.S. Pat. No. 6,272,871. Generally, in this patent, the air conditioning system is provided with an energy recovery device that recovers energy generated during operation of the air conditioning system. Specifically, the air conditioning system utilizes a vane-type expander (similar to a vane type compressor, but operating in reverse) to extract energy from normal operation of the air conditioning system. In this air conditioning system, the vane-type expander is located between the condenser and the evaporator and extracts energy from the expansion of refrigerant from the liquid phase to the vapor-liquid phase, which is then fed to the evaporator to provide cooling to the passenger compartment of the vehicle.
It has been discovered that in an air conditioning systems that employs a vane-type expander as an energy recovery device, the rotor of the expander slows down or stops rotating under certain conditions, thereby losing momentum. Specifically, when the flow of high-pressure refrigerant the expander is stopped, vacuum or suction is produced between adjacent vanes moving from a lower volume area of the expander to a larger volume area of the expander. This suction effects the rotation of the expander and can act as a brake, slowing or stopping rotation of the expander, resulting in a phenomenon referred to as suction loss (energy loss resulting from suction). As a result, rotary momentum of the rotor of the expander is retarded causing a loss of energy and a loss of potential work produced from the energy recovery device.
In view of these operational limitations of the vane-type expander used as an energy recovery device, one aspect of the present invention is to utilize a jet-type expander to increase an amount of energy recovered. The jet-type expander will reduce and/or eliminate the suction loss that occurs in energy recovery devices that utilize a vane-type expander in an air conditioning system.
In view of the state of the known technology, another aspect of the present invention is to provide an air conditioning system that mainly comprises an evaporator, a compressor, a condenser, a valve and an energy recovery device. The compressor is fluidly connected to the evaporator to compress low-pressure refrigerant exiting the evaporator to high-pressure refrigerant. The condenser is fluidly connected to the compressor to receive the high pressure refrigerant and dissipate heat therefrom. The valve is configured to control flow of high pressure refrigerant exiting the condenser. The energy recovery device includes a movable expander having an inlet and an outlet. The inlet is fluidly connected to the valve to receive the high pressure refrigerant. The movable expander is configured and arranged to phase change the refrigerant from high pressure refrigerant at the inlet to low pressure refrigerant at the outlet. The energy recovery device is configured to extract work from movement of the movable expander due to the phase change of the refrigerant from the high pressure refrigerant to the low pressure refrigerant.
Referring now to the attached drawings which form a part of this original disclosure:
Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Referring initially to
As shown schematically in
The components of the air conditioning system 12 will now be described in more detail. The evaporator 16 is disposed in a low pressure line 24, while the condenser 20 and the valve 22 are disposed in a high-pressure line 26. The compressor 18 is disposed between the end of the low pressure line 24 and the beginning of the high-pressure line 26. The energy recovery device 14 is disposed between the end of the high-pressure line 26 and the beginning of the low pressure line 24. Thus, the outlet side of the energy recovery device 14, the low pressure line 24 with the evaporator 16, and the inlet side of the compressor 18 generally define a low-pressure zone of the air conditioning system 12. On the other hand, the outlet side of compressor 18, the high-pressure line 26 with the condenser 20 and the valve 22, and the inlet side of the energy recovery device 14 generally define a high-pressure zone of the air conditioning system 12.
The evaporator 16 is a conventional element of the air conditioning system 12 and serves to absorb heat outside the evaporator 16. The evaporator 16 can include a blower or fan which forces air past the evaporator 16 for improved heat transfer. Heat in the moving air is in turn absorbed by low-pressure refrigerant within the evaporator 16. Optimally, the refrigerant within the evaporator 16 is a vapor state, or a liquid-vapor state. The low-pressure line 24 fluidly connects the energy recovery device 14 to the evaporator 16 and also fluidly connects the evaporator 16 to the compressor 18.
The compressor 18 is fluidly connected to the evaporator 16 to compress low-pressure refrigerant exiting the evaporator 16 to high-pressure refrigerant that is directed to the condenser 20. In other words, the low-pressure refrigerant exiting the evaporator 16 is directed to the compressor 18 via the low-pressure line 24. The compressor 18 preferably compresses the refrigerant in a conventional manner into high-pressure refrigerant in the vapor state. The high-pressure refrigerant compressed by the compressor 18 exits the compressor 18 via the high-pressure line 26. Thus, the high-pressure line 26 is further fluidly connected to the condenser 20 in a conventional manner.
As mentioned above, the condenser 20 is fluidly connected to the compressor 18 to receive the high pressure refrigerant and dissipate heat therefrom. The condenser 20 can include a blower or fan that forces air past the condenser 20 for improved heat transfer. Hence, the high-pressure refrigerant within the condenser 20 is cooled by airflow in a conventional manner. The cooled high-pressure refrigerant is then directed to the valve 22 via the high-pressure line 26, in a conventional manner. By opening and closing the valve 22, the valve 22 effectively controls the flow of high pressure refrigerant exiting the condenser 20 to the energy recovery device 14.
The air conditioning system 12 further includes a control unit 30 for controlling the opening and closing of the valve 22. A conventional user interface 32 is provided for allowing the user to input the desired settings that the control unit 30 uses to operate the components of the air conditioning system 12. The control unit 30 preferably includes a microcomputer with an air conditioning control program that controls air conditioning system 12 in accordance with the air conditioning control program. The control unit 30 also preferably includes other conventional components such as an input interface circuit, an output interface circuit, and storage devices such as a ROM (Read Only Memory) device and a RAM (Random Access Memory) device. It will be apparent to those skilled in the art from this disclosure that the precise structure and algorithms for the control unit 30 can be any combination of hardware and software that will carry out the functions of the air conditioning system 12 as needed and/or desired. A primary purpose of the control unit 30 is to provide a cold evaporator temperature that is above the freezing point of water, while ensuring that the refrigerant entering the compressor 18 is in the vapor phase. This facilitates good compression behavior at the compressor 18 and A/C cooling performance.
Turning now to
As seen in
In this illustrated embodiment, the housing 40 of the energy recovery device 14 has an expansion chamber 50 that houses the movable expanders 46 that are supported on the rotatable shaft 42 for rotation about a center rotational axis A of the rotatable shaft 42. The housing 40 of the energy recovery device 14 is further provided with a high-pressure receiving port 52 and a low-pressure discharge port 54. The high pressure receiving port 52 is fluidly connected to the high-pressure line 26, while the low-pressure discharge port 54 is fluidly connected to the low-pressure line 24. The low-pressure discharge port 54 forms a low pressure refrigerant outlet of the expansion chamber 50, which is connected to the evaporator 16 via the low-pressure line 24. Thus, basically, the high pressure refrigerant moves to the movable expanders 46 through the center of the rotatable shaft 42. The movable expanders 46 are disposed in a low pressure vapor filled volume of expansion chamber 50. The movable expanders 46 are also oriented so that when refrigerant mass is expelled from the movable expanders 46, they will impart a net torque on the rotatable shaft 42. The refrigerant in the expansion chamber 50 (low pressure cavity) escapes to the evaporator 16 due to the low pressure created at the suction side of the compressor 18. With the assistance of gravity, the liquid is taken from this volume so that the movable expanders 46 can move freely in a vapor volume of the expansion chamber 50.
As seen in
The rotatable shaft 42 has a main fluid channel or passage 60 and a pair of branch fluid channels or passages 62. The main fluid channel 60 is in fluid communication with the high pressure receiving port 52 for receiving the high pressure refrigerant. The branch fluid channels 62 are in fluid communication with the main fluid channel 60. The branch fluid channels 62 extend extending in a radial direction from the main fluid channel 60 for conveying the high pressure refrigerant to the extension members 44. In particular, in this embodiment, each of the extension members 44 has a fluid channel 64 that is in fluid communication with one of the branch fluid channels 62 for conveying the high pressure refrigerant to a corresponding one of the movable expanders 46.
Now the movable expanders 46 of the illustrated embodiment will now be discussed in more detail. Basically, the movable expanders 46 are operatively connected to the rotatable shaft 42 by the extension members 44 such that the rotatable shaft 42, the extension members 44 and the movable expanders 46 rotate together as a unit with respect to the housing 40. While only two of the movable expanders 46 are shown, it will be apparent from this disclosure that only one movable expander 46 can be used if needed and/or desired. Likewise, it will be apparent from this disclosure that more than two of the movable expander 46 can be used if needed and/or desired. As mentioned above, the extension members 44 extend from the rotatable shaft 42 to a corresponding one of the movable expanders 46 so that the movable expanders 46 rotate the rotatable shaft 42 as high pressure (liquid/vapor) refrigerant changes to low pressure refrigerant en route to the evaporator 16.
The movable expanders 46 are aimed in a manner that generates complementary torque that will rotate the rotatable shaft 42 when high pressure refrigerant is expelled into the low pressure cavity of the expansion chamber 50. The refrigerant delivered to the low pressure cavity of the expansion chamber 50 will ultimately be removed through the low-pressure discharge port 54 by the suction function of the compressor 20 via the evaporator 16 in the flow path of the low-pressure line 24. Each of the movable expanders 46 has an inlet 72 and an outlet 74. The movable expanders 46 are fixed to the outer free ends of the extension members 44, respectively. Thus, the movable expanders 46 are spaced radially outward from a center rotational axis A of the rotatable shaft 42 by the extension members 44. The inlets 72 of the movable expanders 46 are in fluid communication with the fluid channels 64 of the extension members 44 for receiving the high pressure refrigerant. In other words, the fluid channels 64 of the extension members 44 provide the high pressure refrigerant from the branch fluid channels 62 of the rotatable shaft 42 to the inlets 72 of the movable expanders 46. The outlets 74 of the movable expanders 46 are configured and arranged to rotate the rotatable shaft 42 of the energy recovery device 14 in a first rotational direction about the center rotational axis A of the rotatable shaft 42 in response to the phase change of the refrigerant from the high pressure refrigerant at the inlets 72 to the low pressure refrigerant at the outlets 74.
The movable expanders 46 of the illustrated embodiment are preferably identical. Thus, the following description applies to both of the movable expanders 46 of the illustrated embodiment. The inlet 72 of each of the movable expanders 46 is fluidly connected to the valve 22 via the channels 60, 62 and 64, the high pressure receiving port 52 and the high-pressure line 26 to receive the high pressure refrigerant. The outlet 74 of each of the movable expanders 46 has a larger cross sectional area than a cross sectional area of the inlet 72 of each of the movable expanders 46. In the illustrated embodiment, the cross sectional areas of the outlets 74 of the movable expanders 46 are approximately 70 times than the cross sectional areas of the inlets 72 of the movable expanders 46. The cross sectional area ratio of the outlet 74 to the inlet 72 will depend on the refrigerant type and operating pressures. For Freon R134a, roughly a 70:1 ratio is desired, based on the density change of liquid refrigerant to a vapor at typical condenser and evaporator pressures. If the appropriate outlet/inlet cross sectional area ratio is contained in the design, a variety of nozzle shapes for the movable expanders 46 can give rise to a very high percentage of the ideal power recovery.
With the energy recovery device 14, the sizes and shapes of the movable expanders 46 are preferably designed to extend slightly beyond the maximum expected refrigerant expansion ratio. This arrangement enables the movable expanders 46 to contact the refrigerant during the entire expansion action. Since the high pressure refrigerant is carried internal to the mechanism, 100% of the refrigerant's expansion momentum change acts on the device. Due to the non-positive displacement nature of the energy recovery device 14, suction losses are not a concern. The nozzle structures of the movable expanders 46 are designed to impinge the expanding refrigerant in order to experience a net force from the momentum change. Ideally, the shape of the nozzles of the movable expanders 46 will direct all flow tangentially to the rotational path of the nozzles (essentially parabolic) of the movable expanders 46.
In the illustrated embodiment, each of the movable expanders 46 has a parabolic shape in longitudinal cross section between the inlet 72 and the outlet 74 of the movable expander 46. Thus, the movable expanders 46 constitute jet nozzles, which expel the refrigerant mass to rotate the rotatable shaft 42 of the energy recovery device 14. The shapes of the movable expanders 46 are preferably fashioned to direct expanding refrigerant tangentially to the center rotational axis A of the rotatable shaft 42. The size of the movable expanders 46 are preferably selected to contain the full expansion of the refrigerant as it changes pressure. In effect, this feature re-directs refrigerant flow throughout the expansion process by experiencing a net force directed opposite of the refrigerant flow direction. In the illustrated embodiment, while a parabolic shape is illustrated, it will be apparent from this disclosure that other conic shapes can be used if needed and or desired. In any event with respect to the shape of the movable expanders 46, the movable expanders 46 are configured and arranged to phase change the refrigerant from high pressure refrigerant at the inlet 72 to low pressure refrigerant at the outlet 74. Thus, the energy recovery device 14 is configured to extract work from movement of the movable expander 46 due to the phase change of the refrigerant from the high pressure refrigerant to the low pressure refrigerant. In particular, in this embodiment, the rotatable shaft 42 of the energy recovery device 14 extracts the work from the movement of the movable expanders 46.
While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
