CROSS REFERENCE(S) TO RELATED APPLICATION(S)
BACKGROUND OF THE INVENTION
This application claims the priority benefit of U.S. Provisional Application 60/663,924, filed Mar. 21, 2005.
1. Field of the Invention
The present invention relates to refrigeration and air-conditioning apparatus. In particular the present invention relates to mobile refrigeration and air-conditioning apparatus utilizing a mini-centrifugal compressor with rotational power provided by a ratioed gear drive assembly.
2. Description of Related Art
The refrigeration industry has been working for the past few decades to find replacement refrigerants for the ozone depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) being phased out as a result of the Montreal Protocol. The solution for most refrigerant producers has been the commercialization of hydrofluorocarbon (HFC) refrigerants. The new HFC refrigerants, HFC-134a being the most widely used at this time, have zero ozone depletion potential and thus are not affected by the current regulatory phase out as a result of the Montreal Protocol.
Further environmental regulations may ultimately cause global phase out of certain HFC refrigerants. Currently, the automobile industry is facing regulations relating to global warming potential (GWP) for refrigerants used in mobile air-conditioning. Therefore, there is a great current need to identify new refrigerants with reduced global warming potential for the automobile air-conditioning market. Should the regulations be more broadly applied in the future, an even greater need will be felt for refrigerants that can be used in all areas of the refrigeration and air-conditioning industry.
Currently proposed replacement refrigerants for HFC-134a include HFC-152a, pure hydrocarbons such as butane or propane, or “natural” refrigerants such as CO2 or ammonia. Many of these suggested replacements are toxic, flammable, and/or have low energy efficiency. Therefore, new alternatives are constantly being sought.
A new approach to this problem of high GWP HFCs for the mobile air-conditioning market involves the use of new, low-pressure, low GWP refrigerants in an innovative type of vapor compression refrigeration or air-conditioning apparatus. Miniature scale centrifugal (mini-centrifugal) compressors would facilitate the use of these new low GWP refrigerants. However, the power requirements for such a system are not met in existing automobile designs.
Conventionally, in mobile or stationary air conditioning systems which are driven by internal combustion engines, power is transmitted from the engine to the air-conditioner compressor via a system of belts and pulleys. It is known that it is difficult to achieve the step up in rotational speed from normal engine rotation speeds to the rotational speed required to run a centrifugal compressor via only belts and pulleys without even greater loss of efficiency and reliability.
The use of a conventional belt and pulley system to transfer energy from an electric motor to the compressor of an open air cycle mobile air-conditioning system is described in U.S. Pat. No. 6,381,973. The compressor in this case is preferably a low speed compressor due to the limited (approximate 2×) speed ratio that can be obtained in such a system.
The use of a gear train connected to an electric motor to drive a large scale centrifugal compressor in an industrial chiller is disclosed in U.S. Pat. No. 5,924,847. This patent claims an alternative technology incorporating magnetic bearings in the compressor and a high-speed induction motor provides power to the compressor. The electrical power requirements for such a system do not make it practical for mobile or remote stationary cooling systems.
- BRIEF SUMMARY OF THE INVENTION
Therefore, it would be desirable to develop a system for cooling the air in the passenger compartment of an automobile, which is not dependent on the use of electric motors and belt and pulley systems for increasing the rotational energy to the compressor. It would also be desirable if such a system could meet the power requirements for mini-centrifugal compressors, so that low GWP refrigerants could be used in such a system.
The present invention relates to a means of supplying rotational power to a mini-centrifugal compressor for a refrigeration or air-conditioning apparatus.
In particular, the present invention relates to a refrigeration or air-conditioning apparatus comprising a compressor driven by a ratioed gear drive assembly coupled to an internal combustion engine. By making use of the present invention, the ratioed gear drive with optional ratioed belt drive provides the energy necessary with the required increase in rotational speed to provide optimum operation of the refrigeration or air-conditioning apparatus.
BRIEF DESCRIPTION OF THE DRAWING(S)
Moreover, The power requirements for a mini-centrifugal compressor are not easily met in the present design for automobile engines. The electrical power available in current automobile design is about 14 volts. A mini-centrifugal compressor requires electrical power of about 50 volts. The present invention allows the use of the mini-centrifugal compressor by utilizing a ratioed gear drive from an internal combustion engine crankshaft to provide rotational power to the mini-centrifugal compressor impeller shaft as described above with respect to FIG. 1
The present invention may be better understood with reference to the following figures, wherein:
FIG. 1 is a diagram of one embodiment of a compressor powered by a ratioed gear drive assembly coupled to an internal combustion engine via a ratioed belt drive, as incorporated in a refrigeration or air-conditioning apparatus.
FIG. 2 is a diagram of a second embodiment of a compressor coupled to a ratioed gear drive assembly via a coupling device, which is coupled to an internal combustion engine via a ratioed belt drive, as incorporated in a refrigeration or air-conditioning apparatus.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 3 is a diagram of a ratioed gear drive assembly showing two gear sets, which can be used instead of the gear drive assembly used in either FIG. 1 or FIG. 2.
According to the present invention, there is provided a cooling apparatus, which could be either a refrigeration or air-conditioning apparatus. Such an apparatus is shown in FIG. 1. Vapor-compression refrigeration and air conditioning systems include an evaporator, a compressor, a condenser, and an expansion device. A vapor-compression cycle re-uses refrigerant in multiple steps producing a cooling effect in one step and a heating effect in a different step. Such a system generally includes an evaporator, a compressor, a condenser and an expansion device as will be described below in detail with respect to FIG. 1. With reference to FIG. 1, gaseous refrigerant from an evaporator (42) flows through a pipeline (63) to a compressor, which may be a centrifugal compressor, and more preferably, a mini-centrifugal compressor, mini-centrifugal compressor where it enters at the suction of a first stage housing, having an impeller (11) therein, and is discharged from the first stage housing to the suction of a second stage housing having a second impeller (12) therein. The compressed refrigerant gas output from the second stage housing flows through a pipeline (61) from the compressor to a condenser (41). A pressure regulating valve (51) in pipeline (61) allows recycle of the refrigerant flow back to the compressor via a pipeline (63) providing the ability to control the pressure of the refrigerant reaching the condenser (41) and if necessary to prevent compressor surge. The compressed refrigerant is condensed in the condenser, thus giving off heat. The liquid refrigerant flows through an expansion device (52) via a pipeline (62) to the evaporator (42), which is located in the passenger compartment. In the evaporator, the liquid refrigerant is vaporized providing cooling and the cycle then repeats. The expansion device (52) may be an expansion valve, a capillary tube or an orifice tube.
The compressor of the present invention is driven by a ratioed gear drive assembly coupled to an internal combustion engine. This is accomplished as shown in FIG. 1 as follows. An engine crankshaft (73) drives a belt (33) via a first pulley (31). Said belt also turns a second pulley (32) that is attached to a ratioed gear drive assembly (80) comprising a clutch (81) and at least 1 gear set (82). This gear drive assembly provides the rotational power to the rotating shaft (71) of the mini-centrifugal compressor. In a preferred embodiment, the belt and pulley system may be a ratioed belt drive providing some increase in rotational speed from the engine. Ratioed gear drive assemblies and ratioed belt drives, as described herein, are available commercially.
In order to facilitate the common drive of the gear drive and the compressor, the gear drive and the compressor may share a common rotating shaft. Alternatively, there may be separate rotating shafts as illustrated in FIG. 2.
Reference is now made to FIG. 2, wherein an alternative configuration is shown. The compressor rotating shaft (71) may be separate from a ratioed gear assembly shaft (72) and the two shafts may be joined by a coupling device (21). This coupling device (21) may be a rotary magnetic coupling device. Magnetic couplings are used to transmit rotational motion without direct contact. Rotary couplings are principally used to eliminate the use of seals in rotating machines. Use of magnetic couplers improves the reliability and safety aspects of such machines because seals are prone to deterioration over time and cause leaks.
Rotary magnetic couplers used in the present invention will preferably be of co-axial configuration. The two halves of the coupler are mounted co-axially with each other and nested one within the other. The outer member is connected to the gear assembly shaft and the inner member to the compressor rotating shaft. A cup-shaped stationary member, mounted to the compressor body resides between the driver (gear assembly shaft) and the follower (compressor rotating shaft) and separates the refrigerant fluid from the ambient environment and the gear assembly. Magnetic couplings of this type are available commercially.
Additionally, the coupling (21) shown in FIG. 2 may be joined by any other means of mechanical coupling that may be used to join rotating shafts.
As noted above with respect to the description of FIG. 1, the refrigeration or air-conditioning system of the present invention includes a compressor.
A seal may be required around the compressor rotating shaft in the event a common shaft is used or if there are separate shafts coupled by the optional mechanical coupling (21) of FIG. 2, to prevent refrigerant from leaking out and to prevent air from leaking into the compressor. The present invention may include the use of a compressor shaft seal for sealing the interior of the compressor from ambient air. As the refrigerants used with the mini-centrifugal compressor are low-pressure refrigerants, the seal may be required to prevent air from leaking into the compressor, in particular, and causing deterioration in cooling performance. The shaft seal may be one of several designs known in the art and of several materials of construction, including, but not limited to steel, ceramic, or carbon against steel.
There are various types of compressors that may be used in refrigeration applications. Compressors can be generally classified as reciprocating, rotary, jet, centrifugal, scroll, screw or axial-flow, depending on the mechanical means to compress the fluid, or as positive-displacement (e.g., reciprocating, scroll or screw) or dynamic (e.g., centrifugal or jet), depending on how the mechanical elements act on the fluid to be compressed. The present inventive apparatus preferably utilizes a centrifugal type compressor.
A centrifugal compressor uses rotating elements to accelerate the refrigerant radially, and typically includes an impeller and diffuser housed in a casing or housing. Centrifugal compressors usually take fluid in at an impeller eye, or central inlet of a circulating impeller, and accelerate it radially outward. Some static pressure rise occurs in the impeller, but most of the pressure rise occurs in the diffuser section of the casing, where velocity is converted to static pressure. Each impeller-diffuser set is a stage of the compressor. Centrifugal compressors are built with from 1 to 12 or more stages, depending on the final pressure desired and the volume of refrigerant to be handled. The present inventive apparatus utilizes a centrifugal compressor with at least one stage (one impeller), preferably 2 stages (2 impellers).
The pressure ratio, or compression ratio, of a compressor is the ratio of absolute discharge pressure to the absolute inlet pressure. Pressure delivered by a centrifugal compressor is practically constant over a relatively wide range of capacities.
Positive displacement compressors draw vapor into a chamber, and the chamber decreases in volume to compress the vapor. After being compressed, the vapor is forced from the chamber by further decreasing the volume of the chamber to zero or nearly zero. A positive displacement compressor can build up a pressure, which is limited only by the volumetric efficiency and the strength of the parts to withstand the pressure.
Unlike a positive displacement compressor, a centrifugal compressor depends entirely on the centrifugal force of the high-speed impeller to compress the vapor passing through the impeller. There is no positive displacement, but rather what is called dynamic-compression.
A multi-stage impeller system may be used in a centrifugal compressor to improve compressor efficiency thus requiring less power in use. For a two-stage system, in operation, the discharge of the first stage impeller goes to the suction intake of a second impeller. Both impellers may operate by use of a single shaft (or axle). Each stage can build up a compression ratio of about 4 to 1; that is, the absolute discharge pressure can be four times the absolute suction pressure. Several examples of two-stage centrifugal compressor systems, particularly for automotive applications, are described in U.S. Pat. 5,065,990 and U.S. Pat. 5,363,674, both incorporated herein by reference.
The pressure a centrifugal compressor can develop depends on the tip speed of the impeller. Tip speed is the speed of the impeller measured at its tip and is related to the diameter of the impeller and its revolutions per minute. Tip speed and impeller diameter can be estimated by making some fundamental relationships for refrigeration equipment that use centrifugal compressors. The torque an impeller ideally imparts to a gas is defined as
*(v 2 *r 2 −v 1 *r 1
) Equation 1
- T=torque, Newton-meters
- m=mass rate of flow, kg/sec
- v2=tangential velocity of refrigerant leaving impeller (tip speed), meters/sec
- r2=radius of exit impeller, meters
- v1=tangential velocity of refrigerant entering impeller, meters/sec
- r1=radius of inlet of impeller, meters
Assuming the refrigerant enters the impeller in an essentially axial direction, the tangential component of the velocity v1=0, therefore
T=m*v 2 *r 2 Equation 2
The power required at the shaft is the product of the torque and the rotative speed
- P=power, W
- ω=angular velocity, radians/s therefore,
P=T*w=m*v 2 *r 2*ωEquation 4
At low refrigerant flow rates, the tip speed of the impeller and the tangential velocity of the refrigerant are nearly identical; therefore
r 2 *w=v 2 Equation 5
P=m*v 2 *v 2 Equation 6
Another expression for ideal power is the product of the mass rate of flow and the isentropic work of compression,
*(1000J/kJ) Equation 7
- Hi=Difference in enthalpy of the refrigerant from a saturated vapor at the evaporating conditions to saturated condensing conditions, kJ/kg.
Combining the two expressions Equation 6 and 7 produces,
v 2 *v 2=1000*H i Equation 8
The capacity of the centrifugal compressor is determined by the size of the passages through the impeller. This makes the size of the compressor more dependent on the pressure required than the capacity. Large centrifugal compressors typically operate at 3000 to 7000 revolutions per minute (rpm). Small scale centrifugal compressors (mini-centrifugals) are designed for high speeds, from about 20,000 rpm to about 75,000 rpm, and have small impeller diameter, typically less than about 0.15 meters (about 6 inches). The mini-centrifugal compressors which can be used with the present invention preferably operate at impeller speeds of 30,000 to 50,000 rpm and have impeller diameter of less than 0.10 meters (about 4 inches).
Stationary refrigeration or air-conditioning apparatus refers to the equipment used for cooling the air in a building, or cooling perishable goods such as foods, pharmaceutical materials, etc, in a conventional, non-mobile, non-vehicle mounted, system.
Such stationary refrigeration or air conditioning systems may be associated with CHP (Combined Heat and Power) systems, wherein a stationary internal combustion engine is used to drive an electrical generator. The waste heat produced by the engine may be recovered and used to perform work, by such means as a Rankine Cycle (steam engine) or Organic Rankine cycle (ORC). In a Rankine cycle, the heat is used to vaporize a liquid (an organic liquid in the case of an ORC), which in turn drives a turbine. The mechanical energy of the turbine may be used to drive an electricity generator, which runs a refrigeration or air-conditioning system.
An alternative embodiment of the present invention involves using a high ratio gear drive from the crankshaft of the stationary engine employed in such a system, with the output shaft from the gears being coupled to a mini-centrifugal compressor. An example could be use of this as part of a commercially available CHP system for homes, which are off the power grid, to generate electricity and recover exhaust heat to heat water or building air, and at the same time, use the ratioed gear driven compressor to provide cooling. The present invention is particularly useful in remote locations where access to electrical power is limited, if available at all.
Mobile refrigeration apparatus or mobile air-conditioning apparatus refers to any refrigeration or air-conditioning apparatus incorporated into a mobile transportation unit for the road, rail, sea or air. In addition, apparatus, which are meant to provide refrigeration or air-conditioning for a system independent of any moving carrier, known as “intermodal” systems, are included in the present invention. Such intermodal systems include “containers” (combined sea/land transport) as well as “swap bodies” (combined road and rail transport). The present invention is particularly useful for road transport refrigerating or air-conditioning apparatus, such as automobile air-conditioning apparatus or refrigerated road transport equipment.
The mini-centrifugal compressors of the present invention are capable of producing refrigeration capacity in the range from about 0.5 tons (1.7 kW) to about 3 tons (10.3 kW). Typically, about 1.2 tons (4.0 kW) to about 2.0 tons (6.8 kW) would be needed to cool an automobile passenger compartment. Greater capacity may be needed for many mobile refrigeration units such as road and rail refrigerated containers.
The refrigeration or air-conditioning apparatus of the present invention may additionally employ fin and tube heat exchangers, microchannel heat exchangers and vertical or horizontal single pass tube or plate type heat exchangers for the evaporator and/or the condenser.
Conventional microchannel heat exchangers may not be ideal for the new low-pressure refrigerants to be used in the refrigeration or air-conditioning apparatus of the present invention. The low operating pressure and density result in high flow velocities and high frictional losses in all components. In these cases, the evaporator design may be modified. Rather than several microchannel slabs connected in series (with respect to the refrigerant path) a single slab/single pass heat exchanger arrangement may be used. This type of heat exchanger comprises multiple channels through which the refrigerant all flows at the same time, thus producing a smaller pressure drop across the heat exchanger. Therefore, a preferred heat exchanger design for use as the evaporator and/or condenser in the refrigeration or air-conditioning apparatus of the present invention is a single slab/single pass heat exchanger.
The engine crank-shaft will generally operate in a range from about 600 revolutions per minute (rpm) to about 6000 rpm. As the mini-centrifugal compressor must operate at about 20,000 rpm to about 75,000 rpm, the ratioed gear drive assembly is needed to provide the increased rotational speed. The gears and the optional ratioed belt drive must therefore be sized for that magnitude of increase. Additionally, the compressor impeller speed must be maintained at a minimum speed to ensure adequate cooling during all road speeds and engine idle.
Certain controls may be needed within the present refrigeration or air-conditioning apparatus to ensure optimum cooling performance. At high engine speed conditions, the engine crank-shaft will be rotating at a higher rate, which will increase the compressor impeller speeds as well. The ratioed gear drive must be controlled such that the compressor impeller is not driven to too high a rate of speed. Excessive impeller speeds above the design limits may cause damage to compressor internals, such as distortion of the impeller blades, which may result in generally reduced compressor performance and eventually, shorter compressor lifetime. Further, at engine idle, the gears must maintain the impeller speed at a minimum level for adequate cooling to be accomplished.
In one embodiment of the present invention, at least 2 gear sets are used to control the compressor impeller speed in the optimum range for adequate cooling. Reference in now made to FIG. 3, wherein a gear assembly shaft (74) is shown joining gear set (82 a) to gear set (82 b). When the engine is running at high speeds, the controls would clutch to a lower ratio gear set to keep the compressor running at a suitable speed for proper air-conditioner performance. Alternatively, at engine idle, the gear drive would clutch to a higher ratio gear set, thus maintaining adequate impeller speeds for proper cooling by the air-conditioner.
Additionally, in a second embodiment of the present invention, the speed of the compressor impeller may be controlled by way of a drive belt system, which employs adjustable sheaves on the pulleys in order to increase or decrease the speed of the compressor to accommodate for changes in engine rpm from idle speeds to highway speeds. The adjustable sheave variable speed drive mechanism can be sized to either increase or decrease the speed of the driven pulley. Variable sheave belt drives are available commercially.
The choices for drive types for adjustable speed drives include traction drives, belt and chain drives, gear drives or differentials, hydraulic drives, eddy current drives, and magnetic coupling. Traction drives depend upon friction between a speed adjusting mechanism and specially shaped input and output plates to achieve adjustable speed with relatively high efficiency. Belt and train drives operate with adjustable diameter sheaves or pulleys. Gear drives are the most durable, rugged, and efficient of all adjustable-speed drives, but they are capable of providing only a specific number of fixed gear ratios. In a hydraulic drive there are two main methods of hydraulically varying the speed of the driven load when the driving motor is operating at a constant speed, fluid coupling and hydraulic pump and motor. Hydraulic drives offer some additional flexibility in that the orientation of the output and input shafts can be in any of a variety of geometries, thus allowing more design and installation options. However, hydraulic drives do add elements of complexity in that hydraulic fluid systems are required.
In a preferred embodiment of the present invention, the speed of the compressor impeller may be controlled by use of a magnetic adjustable speed drive. This adjustable speed drive may serve as the coupling device (21) as shown in FIG. 2. Such magnetic drives replace the physical connection between drivers and loads with a gap of air. As there is no physical connection, this type of drive eliminates vibration, reduces noise, tolerates misalignment, provides overload protection, extends equipment life and reduces overall maintenance costs.
The adjustable speed drives work by transmitting torque from the driver to the load across an air gap. There is no mechanical connection between the driving side (e.g., gear assembly) and the driven side (e.g., compressor impeller shaft). The torque is created by the interaction of rare-earth magnets on one side of the drive with induced magnetic fields on the other side. By varying the air gap spacing, the amount of torque transmitted can be controlled, thus permitting speed control.
The magnetic adjustable speed drive may be located between the gear assembly (82) and the compressor rotating shaft (71). In this embodiment of the invention, the compressor rotating shaft would be separate from a shaft being rotated by the gear assembly. This gear assembly shaft would be the driving side for the adjustable speed drive and the compressor impeller shaft would be the load side.
The magnetic adjustable speed drive consists of a magnet rotor assembly, containing rare-earth magnets, attached to the load; a copper conductor rotor assembly attached to the gear driven shaft; and actuation components that control the air gap spacing between the magnet rotors and the conductor rotors. Relative rotation of the copper conductor and magnet rotor assemblies induces a magnetic coupling across the air gap. Varying the air gap spacing between the magnet rotors and the conductor rotors results in controlled output speed. The output speed is adjustable, controllable, and reproducible.
The principle of magnetic induction requires relative motion between the magnets and the conductors. This means that the output speed is always less than the input speed. The difference in speed is known as slip. Several examples of magnetic adjustable speed drives are described in U.S. Pat. No. 6,682,430, U.S. Pat. No. 6,072,258, and U.S. Pat. No. 6,005,317, all of which are incorporated herein by reference.
A control system may be used that senses the compressor shaft rotational speed and adjusts the engine idle, gear set in operation, or magnetic adjustable speed drive as necessary to maintain desired cooling capacity and optimum operation of the refrigeration or air-conditioning apparatus.
Under conditions when refrigeration or air-conditioning are not needed, for instance air-conditioning is seldom used in the cold winter months in an automobile passenger compartment, the compressor should be turned off. In this situation, the clutch (81) will set the gear assembly (82) free from the rotating pulley (32). Thus, the compressor rotating shaft will be disconnected and maintained in a stationary condition.
The present invention further relates to a process for producing cooling comprising compressing a refrigerant in a mini-centrifugal compressor powered by a ratioed gear drive assembly coupled to an internal combustion engine; condensing said refrigerant; and thereafter evaporating said refrigerant in the vicinity of a body to be cooled.
The refrigerants for which this new refrigeration or air-conditioning apparatus are useful are hydrofluorocarbons (HFCs), including saturated and unsaturated compounds, fluoroethers (HFOCs), haloketones, hydrocarbons, chlorocarbons, alcohols, ketones, ethers, esters, N-(difluoromethyl)-N,N-dimethylamine, 1,1,1,2,2-pentafluoro-2-[(pentafluoroethyl)thio]ethane and combinations thereof. Depending upon the cooling capacity required, the boiling points of useful refrigerants may be anywhere from about −50° C. to about +75° C. Preferably, the refrigerants useful with the present invention possess boiling points in the range from about 0° C. to about +60° C., thus having lower vapor pressures at room temperature than the conventional CFC, HCFC and HFC refrigerants, such as R-12, R-22, or R-134a. The refrigerants also have low or zero ozone depletion potential and low global warming potential. Refrigerants useful with the new mini-centrifugal compressor in a refrigeration or air-conditioning apparatus include but are not limited to HFC-245fa (1,1,1,3,3-pentafluoropropane, CF3CH2CHF2), HFC-365 mfc (CF3CH2CF2CH3, 1,1,1,3,3-pentafluorobutane), HFC43-10mee (1,1,1,2,3,4,4,5,5,5-decafluoropentane, CF3CHFCHFCF2CF3), HFC-63-14mcee (1,1,1,2,2,3,4,5,5,6,6,7,7,7-tetradecafluoroheptane, CF3CHFCHFCF2CF3), HFC-1336mzz (CF3CH═CHCF3, 1,1,1,4,4,4-hexafluoro-2-butene), HFC-1429myz (CF3CF═CHCF2CF3, 1,1,1,2,4,5,5,5-nonafluoro-2-pentene), HFC-1429mzy (CF3CH═CFCF2CF3, 1,1,1), HFC-1438mzz (CF3CH═CHCF2CF3, 1,1,1,4,4,5,5,5-octafluoro-2-pentene), HFC-153-10mzz (CF3CH═CHCF2CF2CF3, 1,1,1,4,4,5,5,6,6,6-decafluoro-2-hexene), HFC-153-10mczz (CF3CF2CH═CHCF2CF3, 1,1,1,2,2,5,5,6,6,6-decafluoro-3-hexene, HFC-153-10mmyzz (CF3CH═CHCF(CF3)2, 1,1,1,4,5,5,5-heptafluoro-4-(trifluoromethyl)-2-pentene), PFBE (perfluorobutylethylene, CF3(CF2) 3CH═CH2), PEIK (perfluoroethylisopropylketone, CF3CF2C(O)CF(CF3)2), PMIK (perfluoromethylisopropylketone, CF3C(O)CF(CF3)2), HFOC-272fbEβγ (CH3OCH2CHF2, 1,1-difluoro-2-methoxyethane), HFOC-347mmzEβγ (CH2FOCH(CF3)2, 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane), HFOC-365mcEγδ (CF3CF2CH2OCH3, 1,1,1,2,2-pentafluoro-3-methoxypropane), HFOC-356mmzβγ (CH3OCH(CH3) 2, 1,1,1,3,3,3-hexafluoro-2-methoxypropane), HFOC-467mmyEβγ (CH3CH2OCF(CF3)2, 2-ethoxy-1,1,1,2,3,3,3-heptafluoropropane), 2,2-dimethylbutane (CH3CH2C(CH3)3), cyclopentane (cyclo-(CH2)5-), trans-1,2-dichloroethylene (CHCl═CHCl), dimethoxymethane (CH3OCH2OCH3), methyl formate (HCOOCH3), C4F9OCH3, and combinations thereof. These and other suitable refrigerants for use with the refrigeration or air-conditioning apparatus of the present invention are disclosed in U.S. Provisional Patent Applications 60/651,687, filed Feb. 9, 2005; 60/674,825, 60/674,929, 60/674,921 all filed Apr. 26, 2005; 60/685,287, 60/685,288, both filed May 27, 2005; and 60/732,581, filed Nov. 1, 2005; U.S. patent applications Ser. Nos. 11/014,006, 11/014,000, 11/014,435, 11/014433, 11/014,438, 11/014,334, 11/013,901, 11/014,343, all filed Dec. 16, 2004; Ser. Nos. 11/063,178, 11/063,203, 11/063,040, and 11/062,975, all filed Feb. 22, 2005; Ser. No. 11/151,481, filed Jun. 13, 2005; Ser. Nos. 11/152,731, and 11/152,732, both filed Jun. 14, 2005; and Ser. Nos. 11/153,195, 11/153,168, and 11/153,804, all filed Jun. 15, 2005
A body to be cooled may be any space, location or object requiring refrigeration or air-conditioning. In stationary applications the body may be the interior of a structure, i.e. residential or commercial, or a storage location for perishables, such as food or pharmaceuticals. Numerous mobile systems are described earlier in defining mobile refrigeration apparatus and mobile air-conditioning apparatus.
The present invention further relates to a method for providing power to a compressor within a refrigeration or air-conditioning apparatus, said method comprising coupling the compressor to a ratioed gear drive assembly driven by an internal combustion engine to power the compressor. The present invention further relates to a method for controlling impeller speed in a compressor within a refrigeration or air-conditioning apparatus, wherein the compressor is driven by a ratioed gear drive assembly coupled to an internal combustion engine, said method comprising varying the engine idle speed during apparatus operation.
The present invention further relates to a method for controlling impeller speed in a compressor within a refrigeration or air-conditioning apparatus, wherein the compressor is powered by a ratioed gear drive assembly coupled to an internal combustion engine, said method comprising providing a ratioed gear drive comprising multiple gear sets and at least one clutch.
The present invention further relates to a method for controlling impeller speed in a compressor within a refrigeration or air-conditioning apparatus, wherein the compressor is powered by a ratioed gear drive assembly coupled to an internal combustion engine, said method comprising coupling the compressor to the ratioed gear drive assembly via a magnetic adjustable speed drive.
The present invention further relates to a method for controlling cooling capacity for a refrigeration or air-conditioning apparatus, wherein said apparatus includes a compressor powered by a ratioed gear drive assembly coupled to an internal combustion engine, said method comprising varying the engine idle speed during apparatus operation.
The present invention further relates to a method for controlling cooling capacity for a refrigeration or air-conditioning apparatus including a compressor powered by a ratioed gear drive assembly coupled to an internal combustion engine, said method comprising providing a ratioed gear drive assembly comprising multiple gear sets and at least one clutch.
The present invention further relates to a method for controlling cooling capacity for a refrigeration or air-conditioning apparatus, wherein said apparatus includes a compressor, and wherein the compressor is powered by a ratioed gear drive assembly coupled to an internal combustion engine, said method comprising coupling the compressor to the ratioed gear drive assembly via a magnetic adjustable speed drive.
The present invention further relates to a method for controlling compressor surge within refrigeration or air-conditioning apparatus, said apparatus including a compressor driven by a ratioed gear drive assembly coupled to an internal combustion engine, said method comprising maintaining minimum flow of a refrigerant through the compressor by controlling recycle of the refrigerant from the discharge to the suction of the compressor. Compressor surge is a condition that must be voided due to potential damage to the compressor. If the forward flow through the compressor can no longer be maintained due to an increased pressure differential across the compressor, a momentary flow reversal may occur. The recycle valve (51) shown in FIG. 1 allows some portion of the refrigerant flow out of the compressor to be diverted back to the compressor suction thus balancing the pressure across the compressor under the surge point.
The present invention further relates to a method for controlling impeller speed in a compressor within a refrigeration or air-conditioning apparatus, wherein the compressor is powered by a ratioed gear drive assembly coupled to an internal combustion engine, said method comprising coupling the compressor to the ratioed gear drive assembly via an adjustable speed mechanical drive.
The present invention further relates to a method for controlling cooling capacity for a refrigeration or air-conditioning apparatus, wherein said apparatus includes a compressor, and wherein the compressor is powered by a ratioed gear drive assembly coupled to an internal combustion engine, said method comprising coupling the compressor to the ratioed gear drive assembly via an adjustable speed mechanical drive.
The table below shows theoretical tip speed and impeller diameter for a system using PEIK (perfluoroethylisopropylketone) as refrigerant to produce cooling capacity of approximately 1.5 tons at an impeller speed of 40,000 rpm. The conditions assumed for this example are:
| || |
| || |
| ||Evaporator temperature || 40.0° F. (4.4° C.) |
| ||Condenser temperature ||110.0° F. (43.3° C.) |
| ||Liquid subcool temperature || 10.0° F. (5.5° C.) |
| ||Return gas temperature || 75.0° F. (23.8° C.) |
| ||Compressor efficiency is || 80% |
| || |
These are typical conditions under which small turbine centrifugal compressors perform. Table 1 below shows the enthalpy of the refrigerant gas as it leaves the evaporator, (H Evaporator Out), the enthalpy of the refrigerant gas as in enters condenser (H Condenser In), the change in enthalpy between the evaporator and compressor, (Delta Hi), and the change in enthalpy between the evaporator and compressor multiplied by 0.8 to account for a compressor efficiency of 80%. The table below also shows theoretical tip speed and impeller diameter for a refrigeration apparatus.
|TABLE 1 |
| ||H ||H || || || || || || |
| ||Evaporator ||Condenser || || || ||Tip Speed |
| ||Out ||In ||Delta Hi ||Hi * 0.8 ||Hi * 0.8 ||V2 ||Diameter ||Diameter |
|Refrigerant ||(Btu/lb) ||(Btu/lb) ||(Btu/lb) ||(Btu/lb) ||(KJ/Kg) ||(meter/sec) ||(meters) ||(inches) |
|PEIK ||38.37 ||49.92 ||11.55 ||9.2 ||21.5 ||146.6 ||0.0700 ||2.76 |