U.S. patent application number 10/964196 was filed with the patent office on 2005-04-21 for accumulator with pickup tube.
Invention is credited to Dickson, Timothy Russell, Finlayson, Scott Murray, McGregor, Ian Alexander Neil.
Application Number | 20050081559 10/964196 |
Document ID | / |
Family ID | 34465311 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050081559 |
Kind Code |
A1 |
McGregor, Ian Alexander Neil ;
et al. |
April 21, 2005 |
Accumulator with pickup tube
Abstract
A suction accumulator for refrigeration or air-conditioning
system use, especially for automotive air conditioning system use,
which comprises a "pickup tube" to withdraw liquid from a reservoir
of the accumulator to return oil to the compressor. The accumulator
has a deflector with an outlet tube, to help ensure that fluid does
not flow directly from the inlet opening to the outlet opening of
the accumulator. The relatively narrow second portion of the outlet
tube is closer to the outlet opening than the first portion. The
pickup tube is secured in communication with the relatively narrow
second portion and optimises the oil return function, minimises
restriction to refrigerant flow, maximises effective and actual
reservoir volume, and minimises the amount of liquid delivered to
the compressor at switch-off. Incorporating an electric heating
element or a heat exchanger for engine coolant or exhaust allows
the accumulator of the present invention to function as the
evaporator when the refrigeration system is used in heat pump mode
for heating applications.
Inventors: |
McGregor, Ian Alexander Neil;
(Belleville, CA) ; Dickson, Timothy Russell;
(Kingston, CA) ; Finlayson, Scott Murray;
(Belleville, CA) |
Correspondence
Address: |
BAKER & DANIELS
300 NORTH MERIDIAN STREET
SUITE 2700
INDIANAPOLIS
IN
46204-1782
US
|
Family ID: |
34465311 |
Appl. No.: |
10/964196 |
Filed: |
October 13, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60512102 |
Oct 20, 2003 |
|
|
|
Current U.S.
Class: |
62/503 |
Current CPC
Class: |
F25B 43/006 20130101;
F25B 31/004 20130101; F25B 2341/0016 20130101; F25B 2500/01
20130101; F25B 2400/03 20130101 |
Class at
Publication: |
062/503 |
International
Class: |
F25B 043/00 |
Claims
1. An accumulator comprising an inlet opening, an outlet opening, a
deflector to help ensure that liquid does not flow directly from
the inlet opening to the outlet opening, a conduit inside the
accumulator in communication with the outlet opening, the conduit
comprising a conduit wall surrounding an open interior, the open
interior having a first portion and a second portion, the second
portion having a cross-sectional area less than a cross-sectional
area of the first portion and the second portion being closer to
the outlet opening than the first portion, a pickup tube having a
first end and a second end, the second end being in communication
with the second portion of the open interior.
2. The accumulator of claim 1 wherein the first end of the pickup
tube is adapted to extend into liquid accumulated within the
accumulator.
3. The accumulator of claim 2 wherein the conduit wall has a
passageway formed therein extending from the second portion of the
open interior through at least part of the conduit wall and the
second end of the pickup tube being secured in communication with
the second portion of the open interior via the passageway.
4. The accumulator of claim 2 wherein the conduit forms part of the
deflector.
5. The accumulator of claim 2 wherein the conduit comprises one or
more parts.
6. The accumulator of claim 3 wherein the passageway extends from
the open interior of the conduit to an exterior of the conduit
wall.
7. The accumulator of claim 4 wherein the deflector is secured to
the outlet opening.
8. The accumulator of claim 2 wherein the inlet opening and the
outlet opening are both located in a top of the accumulator.
9. The accumulator of claim 2 wherein the inlet opening is located
in a top of the accumulator and the outlet opening is located in a
side of the accumulator.
10. The accumulator of claim 2 wherein the inlet opening and the
outlet opening are both located in one or more sides of the
accumulator.
11. The accumulator of claim 2 wherein the pickup tube comprises a
means to trap liquid in the pickup tube if suction within the
pickup tube is stopped or if suction is insufficient to draw liquid
up the pickup tube.
12. The accumulator of claim 11 wherein the means to trap liquid
comprises a ball valve.
13. The accumulator of claim 2 wherein the pickup tube comprises a
filter located at a lower end of the pickup tube.
14. The accumulator of claim 2 wherein the pickup tube has several
openings at different heights above the floor of the
accumulator.
15. The accumulator of claim 2 further comprising heat exchanger
coils.
16. The accumulator of claim 2 wherein the open interior tapers
smoothly from the first portion to the second portion.
17. The accumulator of claim 2 wherein an entrance to the open
interior of the first portion is gently flared.
18. An accumulator comprising an inlet opening, an outlet opening,
a means to help ensure that liquid does not flow directly from the
inlet opening to the outlet opening, an outlet conduit means inside
the accumulator in communication with the outlet opening, the
outlet conduit means comprising an open interior, the open interior
having a first portion and a second portion, the second portion
having a cross-sectional area less than a cross-sectional area of
the first portion and the second portion being closer to the outlet
opening than the first portion, a pickup conduit means in
communication with the second portion of the open interior.
19. The accumulator of claim 18 wherein one end of the pickup
conduit means is adapted to extend into liquid accumulated within
the accumulator.
20. The accumulator of claim 18 wherein the means to help ensure
that liquid does not flow directly from the inlet opening to the
outlet opening is a deflector.
21. The accumulator of claim 2 further comprising one of engine
coolant coils and electric heating coils.
22. The accumulator of claim 21 for use as an evaporator.
Description
[0001] This application is a conversion from U.S. Provisional
application No. 60/512,102.
FIELD OF THE INVENTION
[0002] The present invention relates to a new and improved suction
accumulator for use in a refrigeration system, including
air-conditioning (A/C) or heat pump systems, and may be used in an
air-conditioning or heat pump system of a motor vehicle.
BACKGROUND OF THE INVENTION
[0003] Closed-loop refrigeration systems conventionally employ a
compressor that is meant to draw in gaseous refrigerant at
relatively low pressure and discharge hot refrigerant at relatively
high pressure. The hot refrigerant condenses into liquid as it is
cooled in a condenser. A small orifice or valve divides the system
into high and low-pressure sides. The liquid on the high-pressure
side passes through the orifice or valve and turns into a gas in
the evaporator as it picks up heat. (Some systems operate in
"transcritical" mode, where the hot refrigerant is merely cooled in
the high side heat exchanger, now termed a "gas cooler", and turns
to gas plus liquid as it passes through the expansion device.) At
low heat loads, it is not desirable or possible to evaporate all
the liquid in the evaporator. However, excess liquid may cause
problems. Excess liquid refrigerant entering the compressor (known
as "slugging") causes system efficiency loss and can cause damage
to the compressor. For that reason, it is standard practice to
include a reservoir between the evaporator and the compressor to
separate and store the excess liquid. The reservoir is also used to
store excess refrigerant. (Extra refrigerant is typically added to
the system during manufacture to compensate for unavoidable leakage
during the working life of the system.) This reservoir is called a
suction line accumulator, or simply an accumulator.
[0004] An accumulator is typically a metal can, welded together,
and often has fittings attached for a switch, transducer and/or
charge port. One or more inlet-tubes and an outlet tube pierce the
top, sides, or occasionally the bottom, or attach to fittings
provided for that purpose. The refrigerant flowing into a typical
accumulator will impinge upon a deflector or baffle intended to
reduce the likelihood of liquid flowing out the exit, generally by
removing kinetic energy from the liquid so it settles quietly into
the reservoir area without churning or splashing. There are several
known baffles and deflectors, designed to reduce liquid
carryover.
[0005] Promoters of certain accumulators claim not to need
deflectors. These can be satisfactory for designs that have an
inlet that enters the accumulator from one side, horizontally. In
those cases, the opposite side of the accumulator can act as an
energy-reducing deflector. However, for other configurations, such
as those having an inlet in the top, the lack of a deflector may
reduce effective reservoir volume and system efficiency by allowing
churning and splashing that allows liquid to exit the accumulator
and flow to the compressor, that is, by allowing liquid
carryover.
[0006] Some known devices are concerned with reducing the
turbulence of the inlet flow as a way to reduce liquid carryover.
Other designs are more concerned with the coupling between the
reservoir and an outlet passage, mainly to reduce the pressure drop
across the accumulator (an important system performance
parameter).
[0007] A consequence of using a suction line accumulator is that
compressor oil can become trapped within it. Compressor oil is
circulated with the refrigerant in some systems in current usage.
Even if a separator is used, some oil escapes into the system. This
oil will find its way into the accumulator.
[0008] While liquid refrigerant may be expected to evaporate and
return to circulation as needed, the oil does not evaporate. Some
means must be provided to return this oil to circulation.
[0009] A common current practice is to use a J-shaped outlet tube
(a "J-tube") to carry the exiting gaseous refrigerant from the top
of the accumulator down to the bottom and then back up to the
outlet from the accumulator. An orifice at the bottom of the
"J-tube" is used to entrain the oil from the bottom of the liquid
area into the stream of exiting gas. Often, the orifice has a
filter around (or in) it, and the filter may extend into a sump
formed in the bottom of the accumulator to collect the oil-rich
liquid.
[0010] Some J-tubes have a hole near the top, which prevents the
liquid from siphoning or flowing out of the accumulator reservoir
when the system is switched off. The size of the hole is a balance
between breaking any siphon and reducing the effectiveness of oil
pickup.
[0011] Another feature of known designs is the inclusion of
desiccant in the accumulator. Some refrigerant systems are more
susceptible to moisture ingression and damage than others. In some
systems, it is necessary to remove any moisture. The accumulator is
a convenient spot to house a desiccating element. Many early
designs featured desiccant cartridges (or other desiccant
containers), but the typical modern usage is a porous fabric bag of
some suitable shape, containing beads of desiccating material like
alumino-silicate zeolite, and secured to some inner feature of the
accumulator, such as the J-tube, at a position where the beads will
contact the liquid refrigerant.
[0012] Certain known devices are concerned with transferring heat
from the warm refrigerant flowing to the expansion device on the
high pressure side of the refrigerant loop to the cold refrigerant
on the low pressure side. The purpose is typically to cool the high
pressure refrigerant to get more capacity from the evaporator, or
to evaporate any excess liquid that would otherwise flow to the
compressor and damage it. It has been taught to have heat exchange
with automobile exhaust gases to evaporate the excess liquid
refrigerant. There are several reasons why heat exchange with the
accumulator fluid may be desirable. However the desire to put heat
exchangers into an accumulator is typically hampered by the
requirement of many accumulator designs to have the gaseous
refrigerant routed near the bottom of the reservoir volume as it
exits the accumulator so that oil may be entrained. A large, open,
and accessible reservoir volume would be more convenient for
including a heat exchanger.
[0013] In view of volume restrictions in a J-tube style
accumulator, it is difficult to fit heat exchanger coils into an
accumulator that utilizes a j-tube for oil return. It would
therefore be advantageous to have an accumulator with a large,
unobstructed reservoir for incorporating features in an
accumulator, such as heat-exchange coils.
[0014] While it is possible to put heat exchange coils in an
accumulator, it is typically not recommended have a heat source in
the reservoir. The heat source may vaporize liquid refrigerant,
causing more refrigerant to circulate in the system than would
otherwise be the case, which may defeat the purpose of having a
reservoir. One example where heat in the reservoir may be
advantageous is where the A/C system is operated in heat pump
mode--that is, when the object is to supply warm air, not cool.
Typically in such systems, the condenser is located in the area to
be warmed, for instance the cabin of an automobile, and the
evaporator is in the ambient air. Under very cold ambient
conditions, it is difficult for the evaporator to extract heat from
the air, and performance suffers.
[0015] In motor vehicle applications, it is possible to extract
heat from the engine exhaust gases or coolant. The engine coolant
warms rapidly. However, in some case, it takes a significant amount
of time before the coolant is warm enough to transfer sufficient
heat to the cabin, such as, for instance, when it is necessary to
defrost the windscreen. With some high-efficiency motors,
especially diesels, the coolant may never get warm enough to
provide comfortable cabin temperatures in very cold weather.
However the coolant is warm enough to provide sufficient heat to
evaporate the refrigerant, if connected to the refrigerant through
a suitable heat exchanger. Accordingly, in some cases it would be
desirable to be able to put heat exchange coils in an
accumulator.
[0016] As another issue, often the compressor oil and the
refrigerant are selected to be miscible so that the oil does not
deposit thickly on heat exchanger walls, or collect in pools in the
A/C system plumbing or separate in the accumulator. However, in
some instances the required refrigerant and the required oil are
not miscible. The separation of the oil and refrigerant in the
accumulator does not affect the return of oil to the compressor
provided the oil is more dense than the refrigerant, because the
extraction point is typically fixed near the bottom of the
reservoir. However if the oil is less dense than the refrigerant it
is problematic to extract the oil as the volume of refrigerant
changes in the reservoir. The problem is particularly acute if the
oil is more dense than the refrigerant at high temperatures but
less dense at low temperatures such that the location of the oil
switches from under to over the refrigerant when the operating
conditions change. A similar problem could exist (where the
location of the oil within the accumulator changes) when the
accumulator is tilted when climbing steep hills, for example. It
would be desirable to overcome this problem.
[0017] It would be desirable to design an accumulator for an
air-conditioning system where one or more of the following are
achieved: restrictions to refrigerant flow are minimized or
reduced; the effective and actual reservoir volume is increased by
minimizing or reducing the volume occupied by internal components
and by minimizing or reducing liquid splashing and churning; oil is
returned to the compressor in optimal (or improved) fashion; the
amount of liquid delivered to the compressor at switch-off is
minimized or reduced; and the accumulator cost is minimized by
improving the ease of assembly and minimizing the size and number
of components.
[0018] As noted above, there are several challenges and goals for
designers of suction line accumulators. Any restriction in flow
between the evaporator and the compressor decreases system
performance as it increases evaporator pressure (increasing the
temperature) and increases compressor specific work. Hence one
challenge is to minimize the pressure drop caused by the
accumulator. Second, it is desirable to minimize liquid carryover
during operation. Third, the oil required by the compressor should
be returned to circulation. Fourth, it is desirable to minimize or
reduce the flow of liquid to the compressor when the system is
switched off, either by siphoning or migration. Fifth, it would be
desirable to make the accumulator small, inexpensive, and easy to
assemble. Existing literature in this field typically considers
these challenges or goals as being largely separate, where one
design seeks to achieve one goal, at the expense of the others. It
would be desirable for an accumulator to achieve as many of these
goals as possible.
SUMMARY OF THE INVENTION
[0019] An improved accumulator may be achieved through the
realization that although pressure drop between the evaporator and
the compressor caused by the accumulator can be minimized or
reduced by eliminating unnecessary restrictions, pressure drop
cannot be eliminated entirely due to the requirement to return oil
to the compressor. Although apparently not previously recognized, a
careful study of the mechanism for collecting oil from the
reservoir in the accumulator and delivering it out of the
accumulator shows that some pressure difference is required to draw
the oil out. That is primarily because of the design of many
accumulators where the oil and liquid refrigerant settle into the
bottom of the reservoir section while the outlet is located at or
near the top of the accumulator. However even when the outlet is at
or near the bottom of the accumulator, a riser tube is typically
required to prevent the reservoir from being emptied at switch-off
(to avoid filling the lines or the compressor with liquid and
causing undesirable compressor slug at start up).
[0020] An embodiment of the present invention minimizes or reduces
the pressure drop by using a deflector to manage the flow of fluid
and by using a pressure reduction at a restriction within a conduit
through the deflector. The pressure reduction helps lift liquid
(oil or mostly oil) up a small tube or passage (a "pickup tube")
where the liquid is be entrained into the outlet flow of gaseous
refrigerant. The pickup tube is relatively small in diameter
(occupying much less internal volume than a conventional J-tube)
which therefore increases the effective internal volume of the
accumulator when combined with a deflector (where the deflector
helps to minimize or reduce reservoir churning and splashing).
[0021] As noted in the previous paragraph, reduced pressure is used
to lift oil up the pickup tube. Less pressure is needed in view of
the use of the restriction in the conduit. The pickup tube is
secured in communication with the restriction in the conduit. Fluid
is accelerated through the restriction. In other words, pressure is
decreased locally in the area of the restriction according to
Bernoulli's law and does not contribute to overall pressure
drop.
[0022] In practice some pressure drop is introduced in the
accumulator because the flow is not incompressible. There is a
minimum required pressure differential that must be incurred to
return the oil to the compressor. The simplicity of certain
embodiments of the present invention eliminates (or reduces) the
existence of incidental elements that contribute to pressure drop.
Oil is thus returned to the compressor in a more efficient
fashion.
[0023] The pickup tube also minimizes the return of liquid to the
compressor at switch-off, because the pickup tube is open at the
top and hence cannot function as a siphon. As well, because the gas
flow after switch-off is due primarily to migration (refrigerant
evaporating from warm areas of the system and condensing at cooler
places), and the velocity of migrating refrigerant is quite small,
the pressure drop generated at the restriction will be quite small
as well, and hence only minimal liquid, if any, will be withdrawn
from the reservoir at switch-off.
[0024] In accordance with a further embodiment of the present
invention, there is provided an accumulator which is relatively
small, has few components, and is relatively easy to manufacture,
all of which results in decreased cost. The relatively small size
also makes embodiments of the present invention easier to package
into systems. Further, the relatively large unobstructed reservoir
in the accumulator allows for the possibility of other features to
be incorporated into the accumulator, such as, for example,
desiccant and/or coils for heat exchange, if desired.
[0025] In accordance with a further aspect of the present
invention, there is provided an accumulator especially for
automotive use embodying an outer housing consisting of sides and
ends which are welded, crimped, or otherwise hermetically joined
together, with one or more inlets, one or more outlets, and ports
piercing or connecting through the ends and sides as required, and
a deflector and an outlet tube or passage, with a restriction in
the outlet passage to increase the flow velocity therein. A pickup
tube, or other passage, is connected in communication with the
restriction. The pickup tube extends to the bottom (or near the
bottom) of the reservoir to facilitate liquid pickup. The
restriction effect is used to meter liquid from the reservoir into
the flow of gas through the outlet tube. There may also be a
container, either of rigid or flexible material, which holds
desiccant for drying the refrigerant as it flows through the
accumulator, and filters as required. There may also be coils or
other components in the accumulator reservoir for heat
exchange.
[0026] In accordance with another aspect of the present invention,
refrigerant and oil entering an accumulator through an inlet hits
against a deflector surface and possibly other inner surfaces to
dissipate kinetic energy. Oil and liquid refrigerant then flow
downward along the inside surface of the accumulator and settle on
the bottom of the accumulator due to gravity, while the gaseous
refrigerant rises toward an inlet of the outlet passage. The inlet
of the outlet passage is protected from splashing liquid. The inlet
of the outlet passage is shielded by the deflector. Gaseous
refrigerant is drawn up through the outlet passage and out of the
accumulator, and then flows to the compressor. The path through the
outlet passage has a restriction which causes the gaseous
refrigerant passing through it to increase in velocity and thus
have reduced static pressure. Advantageously, to minimize or reduce
turbulence and unnecessary pressure drop, the outlet tube may
include a gradual taper into the restriction. A pickup tube or
passage extends from the reduced pressure area of the restriction
to the liquid reservoir at or near the bottom of the accumulator.
The reduction in static pressure at the restriction can be
calculated to draw the required amount of liquid from the reservoir
through the pickup tube and into the outlet flow of gaseous
refrigerant.
[0027] In accordance with a further aspect of the present
invention, there is provided a pickup tube having a flow check
device that only allows liquid to flow up the tube, and not
downward. This device helps keep the pickup tube filled with liquid
even when there is no (or insufficient) refrigerant flow through
the outlet tube. A filled pickup tube reduces the time required to
return oil to the compressor at system switch-on. The pickup tube
could also be provided with a screen or filter to help prevent
debris from clogging it or passing to the compressor. The pickup
tube could also have more than one orifice in the reservoir of the
accumulator, allowing hydraulic connection to the reservoir at more
than one point, particularly at different heights. Such a feature
could be important should the oil be lighter than the liquid
refrigerant.
[0028] If the oil is less dense than the refrigerant, it is
problematic to extract the oil as the volume of refrigerant changes
in the reservoir. The problem is particularly acute if the oil is
more dense than the refrigerant at high temperatures but less dense
at low temperatures such that the location of the oil switches from
under to over the refrigerant when the operating conditions change.
The pickup tube concept can be employed to resolve this problem by
utilizing multiple tubes at various heights in the reservoir.
[0029] In accordance with another aspect of the present invention
there is provided an accumulator with a largely unobstructed
reservoir volume that could be used for ancillary purposes such as
containing a heat exchanger, for instance, for heat exchange with
other available fluids such as engine exhaust or coolant.
[0030] While many different heat exchangers have been used in motor
vehicles, implementing one as a separate unit requires finding a
space to put it and entails additional cost, both problems in
modern vehicles. It would be advantageous to have such space.
Putting the heat exchange coils in the accumulator would resolve
much of the space and cost issues. While operating as an A/C unit
the heat exchange coils could be rendered inactive with a suitable
valve to shut off the coolant or exhaust gas. In heat pump mode the
valve could be opened and the accumulator would function as the
evaporator. In other words, the refrigerant would be routed into
the accumulator directly from the expansion device, and the heat
exchange coils would evaporate the liquid to gas in the reservoir
volume, from whence the gas would return to the compressor. In this
embodiment, the reservoir function would be largely lost and hence
system efficiency would suffer. However, that is not serious in
heat pump mode for two reasons. First, the actual energy delivered
for supplementary heating is typically not as great as the energy
that must be extracted for cooling. Second, the amount of heat
extracted from the refrigerant by the condenser is the sum of the
heat input mechanically by the compressor plus the heat put in by
the evaporator, so the system does not need to work as efficiently
to deliver as much energy in heating mode as it does to extract the
same amount of energy in A/C mode.
[0031] Electric heaters may be used to provide supplementary heat.
A cost effective option is to install an electric heater in the
accumulator reservoir to supply heat for evaporation. Since the
heat delivered by the heat pump is the sum of the heat put in by
the compressor plus the heat put in by the evaporator, the heat put
in to evaporate the refrigerant is less than the heat evolved by
the heat pump, and therefore less electricity would be required to
get sufficient supplementary heat with this method. By using such a
heat pump, a smaller alternator, less wiring, and fewer controls
would be required than to provide direct electric supplementary
heating. Hence in one embodiment, it is advantageous to have an
accumulator with a large open reservoir volume that can effectively
house heat exchanger coils or an electric heater to provide the
evaporator function in heat pump mode.
[0032] In accordance with a further aspect of the present
invention, there is provided an accumulator comprising an inlet
opening, an outlet opening, a deflector to help ensure that liquid
does not flow directly from the inlet opening to the outlet
opening, a conduit inside the accumulator in communication with the
outlet opening, the conduit comprising a conduit wall surrounding
an open interior, the open interior having a first portion and a
second portion, the second portion having a cross-sectional area
less than a cross-sectional area of the first portion and the
second portion being closer to the outlet opening than the first
portion, and a pickup tube having a first end and a second end, the
second end being in communication with the second portion of the
open interior.
[0033] In accordance with another aspect of the present invention,
there is provided an accumulator comprising an inlet opening, an
outlet opening, a means to help ensure that liquid does not flow
directly from the inlet opening to the outlet opening, an outlet
conduit means inside the accumulator in communication with the
outlet opening, the outlet conduit means comprising an open
interior, the open interior having a first portion and a second
portion, the second portion having a cross-sectional area less than
a cross-sectional area of the first portion and the second portion
being closer to the outlet opening than the first portion, and a
pickup conduit means in communication with the second portion of
the open interior.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1a is a sectional side view of a top in, top out
accumulator, in accordance with an embodiment of the present
invention;
[0035] FIG. 1b is a sectional view of the accumulator of FIG. 1a
taken along line B-B of FIG. 1a;
[0036] FIG. 1c is a magnified view of a circled portion of FIG.
1b;
[0037] FIG. 1d is a magnified view of another circled portion of
FIG. 1b;
[0038] FIGS. 1e, 1f and 1g are three views, similar to FIG. 1c,
showing three different techniques for securing a deflector to an
outlet port;
[0039] FIG. 2a is a sectional side view of a top in, top out
accumulator in accordance with another embodiment of the present
invention;
[0040] FIG. 2b is a magnified view of the circled portion of FIG.
2a;
[0041] FIG. 2c is an alternate embodiment of a pickup tube having a
number of offshoot tubes ending at different heights;
[0042] FIG. 3a is a sectional side view of a top in, side out
accumulator in accordance with another embodiment of the present
invention;
[0043] FIG. 3b is a magnified view of the circled portion of FIG.
3a;
[0044] FIG. 4a is a sectional side view of a side in, side out
accumulator in accordance with another embodiment of the present
invention;
[0045] FIG. 4b is a magnified view of the circled portion of FIG.
4a;
[0046] FIG. 4c is a perspective view of a portion of the deflector
of FIG. 4a;
[0047] FIG. 5 is a sectional side view of a top in, bottom out
accumulator in accordance with another embodiment of the present
invention;
[0048] FIG. 6a is a sectional side view of a side in, bottom out
accumulator in accordance with another embodiment of the present
invention;
[0049] FIG. 6b is a cross-sectional view of the accumulator of FIG.
6a, taken along line B-B of FIG. 6a.
[0050] FIG. 7a is a side sectional view of a ball valve (or a check
valve), in accordance with an embodiment of the present invention,
where the ball is in a raised position;
[0051] FIG. 7b is a side sectional view of the ball valve of FIG.
7a where the ball is in a lowered or closed position;
[0052] FIG. 7c is a cross-sectional view of the ball valve of FIG.
7a taken along line C-C of FIG. 7a;
[0053] FIG. 8 is a partial, sectional side view of an accumulator
having heat exchange coils, in accordance with another embodiment
of the present invention.
DETAILED DESCRIPTION
[0054] A sectional side view of an accumulator 20 is shown in FIG.
1a. The accumulator has a body 22 and a cap 24.
[0055] The body 22 is generally cylindrical, with an open top end,
and a closed bottom end or floor 26. The bottom end 26, in this
embodiment, is sloped inwards, with a depression or sump around and
near the center. The volume within the accumulator 20 may be
referred to as a reservoir 30.
[0056] The cap 24 is formed to fit securely over the top end of the
body 22. The cap 24 has in inlet hole (or inlet port or inlet
opening) 32 and an outlet hole (or outlet port or outlet opening)
34 formed therein. An inlet line 36 is secured to the inlet hole
32. The cap 24 is formed of a suitable material, such as aluminum,
for example.
[0057] The cap 24 is secured to the body 22 by welding, swaging,
heat or ultrasonic staking, gluing or some other suitable
technique.
[0058] A deflector 40 is secured to (or in communication with) the
outlet port 34. The deflector 40 has an exterior deflecting surface
42. As shown in the views of FIGS. 1a, 1b and 1c, the deflector 40
in this embodiment is of a generally inverted funnel shape, having
an open interior 44, with a relatively narrow portion or
restriction 46 and a portion of greater diameter 50. The open
interior 44 may also be referred to as a conduit, an outlet
conduit, an outlet conduit means or an outlet tube. The deflector
40 is formed of a suitable material such as polyamide or
polypropylene plastic.
[0059] The deflector 40 is secured to or in communication with the
outlet port 34 through one of any number of techniques known to
those skilled in the art, such as a snap detail, as shown in the
magnified views of FIGS. 1c and 1d. In this embodiment, one or more
beads 52 protrude from the exterior of the deflector 40, near an
upper end of the deflector 40. There are one or more corresponding
indentations formed within the outlet port 34 to securely
accommodate the one or more beads 52. Alternatively, the one or
more beads could extend from the outlet port (not shown) and fit
within corresponding indentations within the exterior of the
deflector (not shown).
[0060] Different embodiments for securing the deflector 40 to the
outlet port 34 include ultrasonic staking (using ultrasonic sound
to locally melt and push plastic into grooves or other features
machined into an aluminum port), swaging (deforming outwards) a
metal (or plastic) deflector into the outlet port 34, which
typically has grooves for better grip, swaging a short aluminum
tube insert inside the outlet tube 44 to hold plastic more firmly
against the outlet port 34, and heat staking (deforming plastic to
lock it into position). FIG. 1e shows a plastic deflector 40
ultrasonically staked to the outlet port 34. FIG. 1f shows a swaged
aluminum tube insert 55 used in conjunction with the snap detail
(for ease of fixturing during swaging). FIG. 1g shows a deflector
40 staked into the outlet port 34, a procedure that could be
performed mechanically on a metal deflector or with heat on a
plastic deflector. For the staking technique, it is necessary to
have a bead or stop formed on the underside of the deflector to
lock it in place with the top 1e staked downwards to form the
outward projections that complete the lock.
[0061] The inlet line 36 and an outlet line (not shown) are secured
to the inlet hole 32 and the outlet port 34, respectively.
[0062] A passageway 54 is formed within a wall of the deflector 40
adjacent the restriction 46, extending from the restriction 46 of
the deflector 40 to the exterior of the deflector 40. A tube
(hereinafter referred to as a "pickup" tube) 60 is secured to or in
communication with the passageway 54. The pickup tube 60 extends
outside the deflector 40 and down the reservoir 30 near the floor
26 of the accumulator 20. The pickup tube 60 may be secured
directly to the passageway 54 or may be secured in communication
with the passageway 54 otherwise, such as, for example, through a
port 62 shown in FIGS. 1b and 1c.
[0063] The restriction 46 is that portion of the outlet tube 44
where the cross section is reduced. For ease of reference, the
portion of restriction 46 having a minimum cross-sectional area may
be referred to as a throat 63. The cross-sectional area of the
restriction 46 may increase downstream from the throat 63. For
instance, in FIG. 1f, the diameter of the restriction 46 reduces
smoothly to a minimum at the throat 63 and then increases
again.
[0064] For maximum suction, the pickup tube may be connected
(directly or indirectly) to the restriction 46 at the throat
63.
[0065] In FIG. 3a and FIG. 3b, the entire outlet tube 44 functions
as a restriction 46 and there is no separate throat 63 since no one
point has a minimum cross-section. In FIGS. 3a and 3b, the pressure
will be reduced in the entire outlet tube 44 because the gas
velocity in the outlet tube 44 is higher than in the reservoir,
creating the required lower pressure in the outlet tube 44 to pull
liquid up the pickup tube 60. However, because the outlet tube 44
in FIGS. 3a and 3b is not tapered, there may be undesirable
turbulence and pressure drop. Accordingly, the outlet tube 44 in
the embodiment of FIG. 3a could be modified to include a tapered
restriction (not shown). The cross-sectional area of throat 63 of
the restriction 46 may be determined according to the parameters
discussed below. However, it is first helpful to discuss the
operation of the accumulator 20.
[0066] In operation, fluid (not shown), namely refrigerant mixed
with oil, enters the accumulator 20 through the inlet line 36. The
fluid encounters the deflecting surface 42 of the deflector 40, and
is therefore directed down and towards the perimeter of the
accumulator 20. Gaseous refrigerant flows into the open interior 44
of the deflector 40 and then flows up the open interior 44 and out
the outlet port 34.
[0067] Liquid refrigerant and oil flow to the floor 26 of the
accumulator 20. In cases where the oil is denser than the liquid
refrigerant, the oil will settle on the floor 26 of the accumulator
20 below the liquid refrigerant. Advantageously, the end of the
pickup tube 60 extends below the liquid refrigerant (assuming the
oil is denser than the liquid refrigerant) and into the oil.
[0068] Gaseous refrigerant flowing up the interior 44 of the
deflector 40, past the restriction 46, causes a pressure reduction,
thereby drawing oil up the pickup tube 60, and into the throat 63,
where the oil becomes entrained with the gaseous refrigerant and
therefore flows out the accumulator 20 with the gaseous
refrigerant.
[0069] The size of the restriction 46 is determined empirically
and/or through a calculation as discussed below.
[0070] The restriction 46 is similar to a venturi, which is used to
entrain fluids into other fluids.
[0071] The size of the throat 63 is determined so that the pressure
at that point (which, advantageously, is the location in the
restriction 46 where the pickup tube 60 connects) is low enough to
draw the liquid up out of the reservoir 30. The main principle is
the Bernoulli principle, and it is the same principle that causes
lift on an airplane wing: faster flowing fluid exerts less
pressure. For the airplane wing, air moves faster to get around the
curved surface of the top of the wing compared to the flatter lower
surface, so the air on top exerts less pressure than the air on the
bottom (ergo lift).
[0072] In accordance with an aspect of the present invention, the
gas at the throat 63 must move faster to get the same amount of
fluid through because the cross-sectional area for flow is reduced.
Therefore, the pressure at the throat 63 is reduced and this
reduced pressure can be used to suck liquid out of the reservoir
30. If friction and other losses are ignored, the calculation may
be described as follows. The pressure reduction at the throat 63 of
the restriction 46 is calculated by Bernoulli's equation: 1 P = P
tube - P throat = 1 2 gas ( v tube 2 - v throat 2 )
[0073] where v.sub.tube is the velocity of the gas in the portion
of the outlet tube of greater diameter 50 and V.sub.throat is the
velocity of the gas at the throat 63 where the pickup tube 60
enters. The velocity of the gas is related to the diameter of a
tube by the mass flow rate, {dot over (m)}: 2 m . = 4 gas v gas d
2
[0074] The difference in pressure (.DELTA.P) required to lift the
liquid is the density of the liquid (.rho..sub.liquid) times
gravity (g) times the height of the lift (h):
.DELTA.P=.rho..sub.liquid.multidot.g.multidot.h
[0075] By equating the two pressure drops it is possible to solve
for the diameter of the throat 63. So to calculate the diameter of
the throat 63 the following factors are considered:
[0076] d.sub.outlet tube=diameter of the portion of the outlet tube
of greater diameter 50.
[0077] {dot over (m)}=mass flow rate of refrigerant.
[0078] h=h.sub.reservoir-h.sub.liquid where
[0079] h.sub.reservoir=the height of the reservoir section of the
accumulator (measured from the floor to where the pickup tube joins
the throat), and
[0080] h.sub.liquid=the height of the liquid in the reservoir
[0081] .rho..sub.gas=the density of the gas in the accumulator
[0082] .rho..sub.liquid=the density of the liquid in the
accumulator
[0083] Unfortunately the calculated diameter is only a good
starting approximation. Several "secondary" factors have, so far,
been neglected in the calculation. For instance, the pressure
difference required to lift the liquid up the pickup tube 60 is not
exactly the same as the pressure difference between the throat
pressure and the pressure in the portion of the outlet tube of
greater diameter 50. Actually it is the difference between the
pressure inside the accumulator 20 and the pressure at the throat
63. There will be some pressure drop caused by the gas in the
accumulator 20 squeezing into the outlet tube 44, so the pressure
in the portion of the outlet tube of greater diameter 50 will be
less than the pressure in the accumulator interior. To help reduce
these pressure losses, changes in cross-sectional area along the
path followed by the gas may advantageously be made gradually, with
smooth transitions rather than sharp edges. It may also be
advantageous to have a flare on the entrance to the outlet tube 44,
such as, for example, like the end of a trumpet, as shown at the
entrance to the outlet tube 44 in FIG. 1c.
[0084] The pressure loss due to an expansion or contraction in a
tube is governed by an equation of the form: 3 P = C 2 v 2
[0085] where .rho. is the density of the fluid, v is the velocity
of the fluid in the portion of the outlet tube greater diameter 50,
and Cis a "loss coefficient". Loss coefficients may be calculated
by various correlation equations and relations, but it is typically
more accurate to measure them. A neglected secondary factor here is
the loss coefficient for the entry of gas into the outlet tube 44.
Advantageously, as discussed above, the entrance to the outlet tube
46 may be flared.
[0086] Not all of the pressure across the pickup tube 60 will be
applied to lifting the liquid. Some of the pressure will be
consumed in frictional losses through a filter 64 on the end of the
pickup tube 60 (if there is one, such as that shown in FIG. 2a
discussed below) and frictional losses incurred moving the liquid
up the pickup tube 60. The pressure loss related to the filter 64
is another relation like the one used at the entrance to the outlet
tube 44, but now the density is of the liquid and the velocity is
of the liquid moving up the pickup tube 60 of diameter D. Putting
the relation in terms of the mass flow of liquid instead of the
pressure drop results in the following equation: 4 P filter = C
filter 8 m . liquid up tube 2 2 liquid D pickup tube 4
[0087] Other secondary factors to consider include the loss
coefficient of the filter 64, the diameter of the pickup tube 60,
and the flow rate of the liquid. The liquid is typically a mixture
of refrigerant and oil, so the flow of liquid is related to the
percentage of oil in circulation.
[0088] The pressure loss required to overcome friction when moving
fluid through a pipe (or tube) of length L and diameter D is
governed by: 5 P flow = f L D 2 v 2
[0089] where f is the "friction factor". Over quite a wide range of
flow conditions, the friction factor is described quite well by the
Blasius equation:
f=0.3164.multidot.Re.sup.-1/4
[0090] where Re is the "Reynold's number" of the flow, given by: 6
Re = v D
[0091] The following secondary factors that affect the calculation
of the diameter of the restriction have been considered:
[0092] C.sub.flare=Loss coefficient of the entrance to the outlet
tube, which may be flared.
[0093] C.sub.filter=Loss coefficient of the filter (if any) on the
pickup tube.
[0094] {dot over (m)}.sub.liquid up tube=Mass flow of liquid up the
pickup tube, which is related to:
[0095] % OIC=Percentage of oil in circulation in the A/C
system.
[0096] D.sub.pickup tube=The diameter (or cross-sectional area) of
the pickup tube.
[0097] L.sub.pickup tube=The length of the pickup tube.
[0098] f=The friction factor of the flow up the pickup tube, which
is related to: 7 Re = v D
[0099] =The Reynold's number of the flow up the pickup tube, which
involves the density .rho. of the liquid and the diameter D of the
pickup tube, which have already been mentioned as factors, and to
the velocity v of the liquid up the pickup tube, which is
proportional to the mass flow rate of liquid up the tube and is
related to the % OIC, as above, and also to:
[0100] .mu.=The viscosity of the liquid
[0101] Accordingly, there are several factors involved in sizing
the throat diameter. All of these can be calculated. It may also be
effective to calculate once to get a good starting range, and then
make prototypes and test experimentally to optimise.
[0102] Embodiments of the present invention provide improved
control of the oil entrainment while allowing minimized (or less)
overall pressure drop without harming the oil pickup function. The
pressure drop across the present accumulator 20 is given by the sum
of pressure drops due to expansion into the accumulator 20,
dissipation of energy (to separate the liquid and prevent liquid
carry over), the gas squeezing into the outlet tube 46 (using the
flare) and contracting and expanding through the restriction 56.
(The Bernoulli principle predicts that the pressure will return to
the same pressure as it had upstream before the restriction 46, but
in practice there is always some pressure drop across the
restriction 46.) The pressure drop across the accumulator 20 may be
represented as follows: 8 P accumulator = C expansion 2 v 2 + C
dissiption 2 v 2 + C flare 2 v 2 + C restriction 2 v 2
[0103] This equation would appear to represent the smallest value
of .DELTA.P for a functional accumulator 20, which, it will be
noted, does not have terms that are required to ensure oil pick
up.
[0104] Commonly used accumulators may be referred to as "dome
deflector" (U.S. Pat. No. 4,474,035), "dixie cup deflector" (U.S.
Pat. No. 4,111,005), or "trumpet tube" (U.S. Pat. No. 5,179,844)
(no deflector) types (not shown). These all share the same form of
expression for the pressure drop, although the magnitude of the
terms will vary depending on the details of construction: 9 P dome
= C expansion 2 v 2 + C dissiption 2 v 2 + C contraction 2 v 2 + f
j - tube L j - tube D j - tube 2 v 2 + C restriction 2 v 2
[0105] Here the friction of the j-tube is included as well as a
term due to the restriction caused by punching the oil pickup hole
in the j-tube. The word "contraction" is used instead of "flare" in
the third term because many of these accumulators do not use a
flare at the entrance to the j-tube, but it is understood to mean
"flare" if one is present.
[0106] All these other types of accumulators noted in the preceding
paragraph (but not shown) generate a pressure drop across an oil
pick-up hole to pump liquid into a gas stream. That pressure drop
is the sum of the pressure due to the column of liquid in the
reservoir above the pick-up hole, plus the pressure drops caused by
contraction plus the friction in the portion of the j-tube (or
liner, in a liner-type accumulator) between the reservoir and oil
pick-up point. For the common types this would be: 10 P oil pickup
= liquid gh liquid + C contraction 2 v 2 + 1 2 f j - tube L j -
tube D j - tube 2 v 2 + C restriction 2 v 2
[0107] It may be that the term due to the column of liquid is not
too important. A test was conducted with plastic blocks inside an
accumulator to displace the liquid refrigerant and create a higher
column of liquid. The system performance for this test was the same
(or similar) as a test without the blocks, which suggested that the
liquid exiting the accumulator was the same at identical charge
levels, regardless of the liquid height. Since the column of liquid
is likely not as significant as the other terms, the other terms
are likely more important to ensure oil pick-up. Those other terms
are also included in the expression for pressure drop across the
accumulator, so the pressure drop across the accumulator cannot be
eliminated or made as small as might otherwise be desired without
harming the oil pick up function. In contrast, the expression for
oil pick up for certain embodiments of the present invention is: 11
P oil pickup = C flare 2 v 2 + 1 2 gas ( v tube 2 - v throat 2
)
[0108] This expression relies upon the velocity difference within
the outlet tube 44 and the throat 63 of the restriction 46. This
difference does not appear in the expression for pressure drop
across this accumulator. Hence with embodiments of the present
invention, pressure drop across an accumulator can be minimized or
reduced without compromising the oil pick up function. Although the
restriction 46 in embodiments of the present invention actually
does add some pressure drop (as discussed above), the situation is
improved from other accumulators. Therefore, embodiments of the
present invention provide an improved accumulator having the
minimum or reduced pressure drop and good oil pick up.
[0109] In the embodiment described above, the pickup tube 60 is
described as being separate from the deflector 40. In another
embodiment (not shown), the pickup tube 60 could be integral with
the deflector 40 or the outlet tube 44.
[0110] In the embodiment shown in FIG. 1a, a pickup tube 60 is
secured in communication with the restriction 46.
[0111] FIGS. 2a and 2b show a different embodiment. In this
embodiment, the floor 26 of the accumulator 20 is essentially flat
as shown. However, a sump or depression could be provided within
the floor 26 (such as that shown in FIG. 1a, for example), if
desired. A filter 64 is attached to a lower end of the pickup tube
60 to help prevent fouling or blockage of the pickup tube 60 or
downstream by detritus that might otherwise flow from the reservoir
30 up the pickup tube 60.
[0112] In this embodiment, the pickup tube 60 is relatively
straight, and is secured to the inside of the deflector 40, unlike
in the embodiment of FIG. 1a, for example. A passageway 54 extends
from the throat 63 through, or part-way through the wall or
boundary of the deflector 40. One end of the pickup tube 60 is
secured to (or in communication with) the passageway 54, as shown
in the magnified view of FIG. 2b. The pickup tube 60 may be formed
integrally with the passageway 54, for example, or welded or
otherwise secured in communication with the passageway 54.
[0113] Top and side surfaces of the accumulator body 22 may be
formed by welding or otherwise joining separate pieces, or by
forming as one piece, for instance by impact-extruding. The floor
26 of the accumulator 20 may be formed by spin-closing, to create a
hermetic body. The accumulator body 22 may also be formed, for
example, by welding and/or forming.
[0114] In the embodiments shown in FIGS. 1a and 2a, the pickup tube
60 is secured in communication with the passageway 54. However,
according to another embodiment (not shown), the pickup tube 60
extends inside the outlet tube 44. In this embodiment, there is no
passageway 54. For example, the pickup tube 60 may extend up the
outlet tube 44 so that one end of the pickup tube 60 terminates at
the restriction 46. For maximizing or improving suction, with
minimum or reduced turbulence, it may be advantageous to secure one
end of the pickup tube 60 so that its opening is at approximately
90.degree. to the flow of gaseous refrigerant through the
restriction 46.
[0115] Various different configurations of inlet and outlet
positions may be used, as required by the geometry of the
surrounding components. FIGS. 1 and 2 show top-in, top-out
configurations.
[0116] FIG. 3a shows an embodiment with a top-in, side-out
configuration. FIG. 3b shows a magnified view around the outlet
port 34. In this embodiment, fluid enters the accumulator 20
through an inlet port 32. The fluid is deflected by the deflecting
surface 42 of the deflector 40 towards the sides of the accumulator
20 and then flows downward. Gaseous refrigerant flows up the
interior of the deflector 40, and then out the outlet port 34. Oil
and liquid refrigerant flow to the floor 26 of the accumulator 20.
Oil (and perhaps some liquid refrigerant) then flows through the
filter 64 at the bottom of the pickup tube 60 and up the pickup
tube 60, and then into the restriction 46, where it is entrained
within the gaseous refrigerant.
[0117] FIG. 4a shows an embodiment with a side-in, side-out
configuration. FIG. 4b is a magnified view of the circled portion
of FIG. 4a. In this embodiment, fluid flows into the side of the
accumulator 20 through an inlet port. Typically, the velocity of
the fluid through the inlet port 36 is such that all the fluid will
impinge on the deflecting surface 42 of the deflector. The
deflecting surface 42 should advantageously be shaped to ensure (or
reduce the likelihood) that fluid will not be deflected directly
into the outlet tube. Gaseous refrigerant flows into the interior
of the deflector, through the openings created between support arms
66, as perhaps best seen in the perspective view of FIG. 4c. The
gaseous refrigerant then flows out of the accumulator 20 through
the outlet port. Oil and liquid refrigerant will flow to the floor
26 of the accumulator 20, where the oil (and perhaps some liquid
refrigerant) will be drawn up the outlet tube 60 and then out
through the outlet port 34. The outlet tube 46 in FIG. 4b could be
modified to have a flared entrance (not shown) and/or a more
tapered restriction (not shown).
[0118] FIG. 5 shows an embodiment with a top-in, bottom-out
configuration. In this embodiment, fluid flows into the accumulator
20 through the inlet port 32. Fluid is deflected toward the inside
surfaces of the accumulator 20 by the deflecting surface 42 of the
deflector 40. Fluid then flows down. Gaseous refrigerant flows into
the interior of the deflector 40, through the openings created
between support arms 66. The gaseous refrigerant then flows out of
the accumulator 20 through outlet tube 70. Oil and liquid
refrigerant flow to the floor 26 of the accumulator 20, where oil
(and perhaps some liquid refrigerant) is drawn up pickup tube 60
and then out through the outlet tube 70.
[0119] The outlet tube 70 in FIG. 5 could be modified to have a
flared entrance (not shown) and/or a tapered (or more tapered)
restriction (not shown).
[0120] FIGS. 6a and 6b show an embodiment with a side-in,
bottom-out configuration. In this embodiment, fluid enters
accumulator 20 through inlet port 32. Some fluid (without much
velocity) may flow down, inside the accumulator 20. However,
typically most will deflect against the deflecting surface 42 of
deflector 40. As noted above, advantageously, the defecting surface
42 will be shaped to ensure (or reduce the likelihood) that fluid
will not be deflected directly into the outlet tube 70. Gaseous
refrigerant will flow into and down the outlet tube 70, and then
exit the accumulator 20. Oil and liquid refrigerant will flow to
the floor 26 of the accumulator 20, where suction will draw oil
(and perhaps some liquid refrigerant) up the pickup tube 60 and
then into and down the outlet tube 70.
[0121] Under certain conditions of rapid cycling, for instance due
to a low amount of charge in the air conditioning system, the
pickup tube 60 may not deliver sufficient oil to prevent the
compressor (not shown) from overheating. When the compressor is
first turned on, there is a short time when no oil is entrained
with the gaseous refrigerant exiting the accumulator 20, namely
when oil is being drawn up to fill the pickup tube 60. If that time
is a significantly large fraction of the cycle time, the amount of
oil flowing to the compressor may be significantly reduced. This
potentially harmful situation can be remedied by maintaining liquid
in the pickup tube 60. One such technique or means to trap liquid
in the pickup tube 60, according to an embodiment of the present
invention, involves the use a check valve (or "ball valve") 72 in
(or in communication with) the pickup tube 60, for instance as
shown in FIGS. 7a-7c.
[0122] FIG. 7a depicts the check valve 72 when fluid is flowing up
through the pickup tube 60. The upward flow of fluid causes a ball
74 to move upward against a ball barrier 76. A cross-sectional view
of the ball barrier 76 is shown in FIG. 7c. In this position, fluid
flows around the ball 74 and continues up through openings 80 in
the ball barrier 76.
[0123] When the flow of fluid stops (or is sufficiently reduced),
the ball 74 is pulled by gravity (and/or pushed by the weight of
fluid above it) to a narrowed section 82 of the valve 72, where the
diameter of the narrowed section 82 is less than the diameter of
the ball 74. The ball 74 fits snugly, and preferably sealingly,
within the narrowed section 82 of the valve 72, thereby preventing
fluid above the ball 74 from flowing down below the ball 74.
[0124] Another embodiment (not shown) includes a desiccant. The
desiccant may be placed in the reservoir of the accumulator in a
location through which all liquid refrigerant must pass. The
desiccant could be housed in a canister, a fabric bag, or any other
appropriate container. The desiccant and/or its container could be
combined with a filter.
[0125] If the oil is less dense than the refrigerant, it is
problematic to extract the oil when the volume of refrigerant
changes in the reservoir. The problem is particularly acute if the
oil is more dense than the refrigerant at high temperatures but
less dense at low temperatures, such that the location of the oil
switches from under to over the refrigerant when operating
conditions change. One or more pickup tubes can be employed to
resolve this problem by utilizing multiple tubes at various heights
in the reservoir. An example is shown in FIG. 2c, which shows an
alternate embodiment of the pickup tube 60 of FIG. 2a. In FIG. 2c,
pickup tube 60' has two offshoot pickup tubes 60", each of which
has a filter 64 on a lower end. Each of the offshoot pickup tubes
60" is positioned at a different height above the floor 26.
Similarly, another embodiment may include a single pickup tube
having two or more openings at different heights (not shown).
[0126] An embodiment of the present invention, such as that shown
in FIG. 1 can provide a large reservoir for incorporating features
in an accumulator, such as heat-exchange coils. FIG. 8 shows an
example where two coils 90, 92 have been inserted in the reservoir
section of the accumulator of FIG. 1, especially to enable engine
coolant to provide heat exchange with the refrigerant in heat pump
mode. In this example, fluid flows in and up the coils 90, 92 from
coil flow inlet 94 and flows out the accumulator 20 through coil
flow outlet 96. As discussed above, these coils 90, 92 could be
replaced with an electric heating element for heat pump function.
If, instead, warm refrigerant from the condenser was routed through
the coils in air conditioning mode then heat exchange with the cold
refrigerant in the accumulator would provide the "internal heat
exchange" function for enhanced air conditioning effect. However
the internal heat exchange would probably be too large, and baffles
may be required to limit the exposure of reservoir fluid to the
coils.
[0127] Numerous modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims, the invention may be practised otherwise than as
specifically described herein. The present invention allows for
significant changes in shapes, sizes, dimensions, materials, and
aspects as required by the overall air-conditioning and/or heating
system. The external structure such as the tubes and fittings can
be modified without departing from the invention as disclosed
herein, as can adding brackets, insulation, service ports, inlets
from auxiliary evaporators, etc.
[0128] As an example, all of the embodiments described above
incorporate a deflector. While the accumulator 20 should have a
means to help ensure that liquid does not flow directly from the
inlet opening 32 to the outlet opening 34, that means need not be a
deflector, per se. In other words, provided that an accumulator can
be designed so that liquid refrigerant is substantially prevented
from flowing from the inlet port 32 directly to the outlet port 34,
it may be possible to avoid the use of a deflector. In such a case,
the accumulator will have a particular geometry or other means
(such as the shape of the accumulator combined with the location of
the inlet port 32 with respect to the outlet port 34) to help
ensure that liquid does not flow directly from the inlet port 32 to
the outlet port 34 (or outlet tube 44).
[0129] The outlet tube 44 as described above may be cylindrical or
tubular. The outlet tube 44 could also be any other shape that
allows fluid to flow through. The outlet tube 44 could comprise one
or more parts. For example, the portion of the outlet tube 44
containing the restriction 46 need not be integral with the portion
of greater diameter 50.
[0130] It should also be noted that the pickup tube 60 need not be
a tube, per se. It need only be a passage (not shown) adapted to
extend from liquid in the reservoir 30 of the accumulator 20 and be
in communication with the restriction 46. Such a passage may be
referred to as a pickup conduit means.
[0131] While the above description refers to a single inlet port 32
and a single outlet port 34, alternate embodiments could
incorporate one or more inlet ports and one or more outlet ports
(not shown).
* * * * *