Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2000-03-30
2001-08-14
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S087000, C062S116000, C062S402000
Reexamination Certificate
active
06272871
ABSTRACT:
BACKGROUND
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.
An automobile air conditioner consumes much engine power, which negatively impacts the acceleration performance and fuel economy. Attempts have been made to improve the air conditioner's efficiency by capturing some of the energy released by the hot, high-pressure refrigerant during the expansion stage, and applying the recovered energy toward compressing the cool vapor-phase refrigerant.
When a high-pressure, liquid refrigerant is throttled through an expansion valve or an orifice, it is transformed into a cold low-pressure saturated liquid-vapor-phase refrigerant, which is known as a “refrigeration effect.” The throttling process itself does not fundamentally change the enthalpy (energy) content of the liquid-phase refrigerant. The liquid-phase to saturated liquid-vapor phase transformation, however, creates a boiling effect that liberates much kinetic energy, lowering the temperature of the refrigerant. The refrigerant's pressure drop from the high side to the low side and its subsequent expansion during cavitation (liquid-phase to saturated liquid-vapor-phase) provides excellent opportunity to extract mechanical work. Further, extracting work from the refrigerant will enhance the refrigeration cycle performance, since the energy content of the refrigerant is reduced. It would be desirable to capture this kinetic energy as much as possible.
In this regard, Japanese Patent publication Nos. 11-063707, 4-340062, and 61-96370, for example, disclose substituting the expansion valve with an expansion machine to capture part of the kinetic energy liberated during the throttling process. The expansion machine is essentially a motor driven by the hot, high-pressure liquid-phase refrigerant as it evaporates to a cold, low-pressure saturated vapor-phase refrigerant. The motor in turn is connected to a supercharger or compressor that can partially compress all or some of the cool vapor-phase refrigerant exiting from the evaporator, upstream of the compressor. The compressed refrigerant is fed through the compressor or fed to the condenser. Ideally, this should reduce the energy required to compress the refrigerant, thus making the air conditioner more efficient.
The present inventor has discovered that work can be best captured when the refrigerant is undergoing transformation from a liquid phase (or saturated liquid-vapor phase) to a saturated liquid-vapor phase having a higher vapor content, which occurs in a “high cavitation” region. Keeping the refrigerant in a high cavitation region within the motor, however, is difficult. The present inventor has discovered a way of maintaining the location of the high-cavitation region as the refrigerant is passed through an energy recovery device.
SUMMARY
The present invention thus relates to an air conditioner or air conditioning system with an energy recovery device, and a method thereof. The air conditioner comprises an evaporator, a main compressor, a condenser, and an energy recovery device. The evaporator receives a cold refrigerant and evaporates the refrigerant. The main compressor is connected to the evaporator so that the compressor can receive the evaporated refrigerant from the evaporator and compress the refrigerant. The condenser is connected to the compressor so that the condenser can receive the compressed refrigerant from the compressor. The energy recovery device is connected to the condenser and the evaporator so that the compressed refrigerant is passed through the energy recovery device and directed into the evaporator.
According to one aspect of the invention, the energy recovery device includes a motor and a regulator. The motor is located downstream of the condenser and upstream of the evaporator. The regulator maintains the refrigerant in a high cavitation region, while maintaining within a predetermined refrigerant pressure range in the motor, and expands the compressed and condensed refrigerant to a first saturated liquid-vapor phase. The regulator releases the refrigerant to the evaporator in the first saturated liquid-vapor phase.
According to another aspect of the invention, a method of recovering energy from an air conditioner comprises flowing compressed refrigerant into the motor, detecting the pressure of the refrigerant downstream of the motor, and opening and closing the valve based on the detected pressure of the refrigerant downstream of the motor to regulate the refrigerant flowing into the motor and maintain the refrigerant in a high cavitation region, while maintaining within a predetermined refrigerant pressure range in the motor. This enables the refrigerant to expand to the first saturated liquid-vapor phase in the motor to optimize energy recovery.
According to another aspect of the invention, a method of recovering energy from an air conditioner comprises condensing a compressed refrigerant to a saturated liquid-vapor phase (instead of a liquid phase), passing the saturated liquid-vapor-phase refrigerant through an energy recovery device, which includes a motor, regulating the flow of the refrigerant through the motor and maintaining the refrigerant in a high cavitation region, while maintaining within a predetermined refrigerant pressure range in the motor, to expand, in the motor, the saturated liquid-vapor-phase refrigerant to the first saturated liquid-vapor phase, which has a higher vapor content than the refrigerant released from the condenser, to optimize energy recovery.
The regulator can comprise a valve and a controller. The valve can be located adjacent the motor, either immediately upstream or downstream of the motor. The valve opens and closes (modulates or pulsates) to regulate the flow of refrigerant through the motor. The controller controls the opening and closing of the valve based on the pressure of the refrigerant downstream of the motor and upstream of the evaporator to regulate the refrigerant flowing into the motor and maintain the refrigerant in the high cavitation region, while maintaining within the predetermined refrigerant pressure range in the motor. The refrigerant is expanded to the saturated liquid-vapor phase in the motor, before the refrigerant exits the motor, to optimize energy recovery.
The controller includes a pressure sensor or a pressure switch located downstream of the motor and upstream of the evaporator. In one embodiment, the valve is located immediately upstream of the motor. In this instance, the valve passes the compressed refrigerant when the valve is opened. In another embodiment, the valve is located immediately downstream of the motor, and the energy recovery device further includes an orifice immediately upstream of the motor to limit the flow of liquid refrigerant, when the solenoid valve is open.
The controller can include a temperature sensor located immediately downstream of the evaporator. If a pressure switch is used, the controller can include a power relay to open and close the valve.
The energy recovery device can further include a booster compressor positioned either upstream or downstream of the main compressor, the motor being configured to drive the booster compressor to enhance efficiency. In another embodiment, the motor can be integrally built with the main compressor, the motor further driving the main compressor to aid in compressing the refrigerant. I
Foley & Lardner
Nissan Technical Center North America
Tanner Harry B.
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