U.S. patent application number 11/378832 was filed with the patent office on 2006-11-02 for cooling apparatus powered by a ratioed gear drive assembly.
Invention is credited to Donald Bernard Bivens, Thomas J. Leck, Paul K. Mathur, Miroslav Rohacek, Fuqin Zhao.
Application Number | 20060245944 11/378832 |
Document ID | / |
Family ID | 36616993 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060245944 |
Kind Code |
A1 |
Leck; Thomas J. ; et
al. |
November 2, 2006 |
Cooling apparatus powered by a ratioed gear drive assembly
Abstract
The present invention relates to a cooling apparatus comprising
a refrigeration or air-conditioning apparatus. In particular the
present invention relates to refrigeration or air-conditioning
apparatus utilizing a mini-centrifugal compressor with rotational
power provided by a ratioed gear drive assembly coupled to an
internal combustion engine.
Inventors: |
Leck; Thomas J.; (Hockessin,
DE) ; Bivens; Donald Bernard; (Kennett Square,
PA) ; Zhao; Fuqin; (Toronto, CA) ; Rohacek;
Miroslav; (Landenberg, PA) ; Mathur; Paul K.;
(Hockessin, DE) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY;LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
36616993 |
Appl. No.: |
11/378832 |
Filed: |
March 17, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60663924 |
Mar 21, 2005 |
|
|
|
Current U.S.
Class: |
417/364 |
Current CPC
Class: |
B60H 1/3223 20130101;
B60H 1/3222 20130101 |
Class at
Publication: |
417/364 |
International
Class: |
F04B 35/00 20060101
F04B035/00 |
Claims
1. A refrigeration or air-conditioning apparatus comprising a
compressor driven by a ratioed gear drive assembly coupled to an
internal combustion engine.
2. The apparatus of claim 1, said apparatus being a mobile
refrigeration or mobile air-conditioning apparatus.
3. The apparatus of claim 1, said apparatus being a stationary
refrigeration or stationary air-conditioning apparatus.
4. The apparatus of claim 1, wherein the compressor is a
centrifugal compressor.
5. The apparatus of claim 4, wherein the compressor is a
mini-centrifugal compressor.
6. The apparatus of claim 5, wherein the compressor is a multistage
mini-centrifugal compressor.
7. The apparatus of claim 6, wherein the compressor is a 2-stage
mini-centrifugal compressor.
8. The apparatus of claim 1, further comprising a ratioed belt
drive to connect the ratioed gear drive assembly to the internal
combustion engine.
9. The apparatus of claim 1 wherein the ratioed gear drive assembly
turns a gear assembly rotating shaft external to said compressor,
said gear assembly rotating shaft being coupled to a compressor
rotating shaft by a coupling device.
10. The apparatus of claim 9 wherein said coupling device is a
rotary magnetic coupling device.
11. A method for controlling compressor surge within refrigeration
or air-conditioning 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.
12. 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.
13. 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.
14. 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.
15. 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.
16. 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.
17. 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.
18. 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.
19. The method of any of claims 11-18, wherein the compressor is a
mini-centrifugal compressor.
20. 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.
21. The apparatus of claim 1 further comprising at least one single
slab/single pass heat exchanger as evaporator, condenser or
both.
22. The process of claim 20, wherein said body to be cooled is an
automobile passenger compartment or stationary structure.
23. The apparatus of claim 9 wherein the compressor is coupled to
the ratioed gear drive assembly by an adjustable speed mechanical
drive system.
24. The apparatus of claim 23 wherein the adjustable speed
mechanical drive system is selected from the group consisting of
traction drives, belt and chain drives, gear drives or
differentials, hydraulic drives, eddy current drives and magnetic
coupling.
25. The apparatus of claim 24 wherein the adjustable speed mechanic
drive system is a magnetic adjustable speed drive.
26. 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.
27. 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.
28. The method of claim 26 or 27, wherein the adjustable speed
mechanical drive system is selected from the group consisting of
traction drives, belt and chain drives, gear drives or
differentials, hydraulic drives, eddy current drives and magnetic
coupling.
Description
CROSS REFERENCE(S) TO RELATED APPLICATION(S)
[0001] This application claims the priority benefit of U.S.
Provisional Application 60/663,924, filed Mar. 21, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] 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.
[0004] 2. Description of Related Art
[0005] 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.
[0006] 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.
[0007] Currently proposed replacement refrigerants for HFC-134a
include HFC-152a, pure hydrocarbons such as butane or propane, or
"natural" refrigerants such as CO.sub.2 or ammonia. Many of these
suggested replacements are toxic, flammable, and/or have low energy
efficiency. Therefore, new alternatives are constantly being
sought.
[0008] 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.
[0009] 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.
[0010] 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.times.) speed ratio
that can be obtained in such a system.
[0011] 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.
[0012] 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.
BRIEF SUMMARY OF THE INVENTION
[0013] The present invention relates to a means of supplying
rotational power to a mini-centrifugal compressor for a
refrigeration or air-conditioning apparatus.
[0014] 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.
[0015] 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
BRIEF DESCRIPTION OF THE DRAWING(S)
[0016] The present invention may be better understood with
reference to the following figures, wherein:
[0017] 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.
[0018] 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.
[0019] 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.
DETAILED DESCRIPTION OF THE INVENTION
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] As noted above with respect to the description of FIG. 1,
the refrigeration or air-conditioning system of the present
invention includes a compressor.
[0027] 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.
[0028] 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.
[0029] 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).
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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
T=m*(v.sub.2*r.sub.2-v.sub.1*r.sub.1) Equation 1 where [0035]
T=torque, Newton-meters [0036] m=mass rate of flow, kg/sec [0037]
v.sub.2=tangential velocity of refrigerant leaving impeller (tip
speed), meters/sec [0038] r.sub.2=radius of exit impeller, meters
[0039] v.sub.1=tangential velocity of refrigerant entering
impeller, meters/sec [0040] r.sub.1=radius of inlet of impeller,
meters
[0041] Assuming the refrigerant enters the impeller in an
essentially axial direction, the tangential component of the
velocity v.sub.1=0, therefore T=m*v.sub.2*r.sub.2 Equation 2
[0042] The power required at the shaft is the product of the torque
and the rotative speed P=T*.omega. Equation 3 where [0043] P=power,
W [0044] .omega.=angular velocity, radians/s therefore,
P=T*w=m*v.sub.2*r.sub.2*.omega.Equation 4
[0045] At low refrigerant flow rates, the tip speed of the impeller
and the tangential velocity of the refrigerant are nearly
identical; therefore r.sub.2*w=v.sub.2 Equation 5 and
P=m*v.sub.2*v.sub.2 Equation 6
[0046] Another expression for ideal power is the product of the
mass rate of flow and the isentropic work of compression,
P=m*H.sub.i*(1000J/kJ) Equation 7 where [0047] H.sub.i=Difference
in enthalpy of the refrigerant from a saturated vapor at the
evaporating conditions to saturated condensing conditions,
kJ/kg.
[0048] Combining the two expressions Equation 6 and 7 produces,
v.sub.2*v.sub.2=1000*H.sub.i Equation 8
[0049] 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).
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] 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
(82a) to gear set (82b). 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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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.degree. C. to about +75.degree. C. Preferably, the
refrigerants useful with the present invention possess boiling
points in the range from about 0.degree. C. to about +60.degree.
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, CF.sub.3CH.sub.2CHF.sub.2), HFC-365
mfc (CF.sub.3CH.sub.2CF.sub.2CH.sub.3,
1,1,1,3,3-pentafluorobutane), HFC43-10mee
(1,1,1,2,3,4,4,5,5,5-decafluoropentane,
CF.sub.3CHFCHFCF.sub.2CF.sub.3), HFC-63-14mcee
(1,1,1,2,2,3,4,5,5,6,6,7,7,7-tetradecafluoroheptane,
CF.sub.3CHFCHFCF.sub.2CF.sub.3), HFC-1336mzz
(CF.sub.3CH.dbd.CHCF.sub.3, 1,1,1,4,4,4-hexafluoro-2-butene),
HFC-1429myz (CF.sub.3CF.dbd.CHCF.sub.2CF.sub.3,
1,1,1,2,4,5,5,5-nonafluoro-2-pentene), HFC-1429mzy
(CF.sub.3CH.dbd.CFCF.sub.2CF.sub.3, 1,1,1), HFC-1438mzz
(CF.sub.3CH.dbd.CHCF.sub.2CF.sub.3,
1,1,1,4,4,5,5,5-octafluoro-2-pentene), HFC-153-10mzz
(CF.sub.3CH.dbd.CHCF.sub.2CF.sub.2CF.sub.3,
1,1,1,4,4,5,5,6,6,6-decafluoro-2-hexene), HFC-153-10mczz
(CF.sub.3CF.sub.2CH.dbd.CHCF.sub.2CF.sub.3,
1,1,1,2,2,5,5,6,6,6-decafluoro-3-hexene, HFC-153-10mmyzz
(CF.sub.3CH.dbd.CHCF(CF.sub.3).sub.2,
1,1,1,4,5,5,5-heptafluoro-4-(trifluoromethyl)-2-pentene), PFBE
(perfluorobutylethylene, CF.sub.3(CF.sub.2).sub.3CH.dbd.CH.sub.2),
PEIK (perfluoroethylisopropylketone,
CF.sub.3CF.sub.2C(O)CF(CF.sub.3).sub.2), PMIK
(perfluoromethylisopropylketone, CF.sub.3C(O)CF(CF.sub.3).sub.2),
HFOC-272fbE.beta..gamma. (CH.sub.3OCH.sub.2CHF.sub.2,
1,1-difluoro-2-methoxyethane), HFOC-347mmzE.beta..gamma.
(CH.sub.2FOCH(CF.sub.3).sub.2,
1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane),
HFOC-365mcE.gamma..delta. (CF.sub.3CF.sub.2CH.sub.2OCH.sub.3,
1,1,1,2,2-pentafluoro-3-methoxypropane), HFOC-356mmz.beta..gamma.
(CH.sub.3OCH(CH.sub.3).sub.2,
1,1,1,3,3,3-hexafluoro-2-methoxypropane), HFOC-467mmyE.beta..gamma.
(CH.sub.3CH.sub.2OCF(CF.sub.3).sub.2,
2-ethoxy-1,1,1,2,3,3,3-heptafluoropropane), 2,2-dimethylbutane
(CH.sub.3CH.sub.2C(CH.sub.3).sub.3), cyclopentane
(cyclo-(CH.sub.2).sub.5-), trans-1,2-dichloroethylene
(CHCl.dbd.CHCl), dimethoxymethane (CH.sub.3OCH.sub.2OCH.sub.3),
methyl formate (HCOOCH.sub.3), C.sub.4F.sub.9OCH.sub.3, 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
[0071] 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.
[0072] 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.
[0073] 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
EXAMPLE
[0081] 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: TABLE-US-00001 Evaporator temperature 40.0.degree. F.
(4.4.degree. C.) Condenser temperature 110.0.degree. F.
(43.3.degree. C.) Liquid subcool temperature 10.0.degree. F.
(5.5.degree. C.) Return gas temperature 75.0.degree. F.
(23.8.degree. C.) Compressor efficiency is 80%
[0082] 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-US-00002 TABLE 1 H H Evaporator Condenser Tip
Speed Out In Delta Hi Hi * 0.8 Hi * 0.8 V.sub.2 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
* * * * *