Information
-
Patent Grant
-
6349564
-
Patent Number
6,349,564
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Date Filed
Tuesday, September 12, 200024 years ago
-
Date Issued
Tuesday, February 26, 200222 years ago
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Inventors
-
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 062 510
- 062 503
- 062 509
- 062 175
- 062 335
- 236 1 EA
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International Classifications
-
Abstract
The improved refrigeration system of the present invention includes an accumulator with a diffuser pipe extending downwardly into the upper end of a vapor refrigerant tank, the diffuser pipe extending from an evaporator and discharging vapor refrigerant therefrom into the tank. The diffuser pipe includes a lower end located within the interior of the tank which is expanded in diameter relative to the upper end, thereby reducing the velocity of fluid flowing through the pipe and entering the accumulator tank. A diffusion plate is mounted in the lower end of the diffuser pipe, to further diffuse fluid flowing therethrough. The improved refrigeration system also includes a tee having a stem portion extending horizontally from the condenser of the system, and a pair of upper and lower arms connected in a vertical orientation to the stem. The tee lower arm is connected to the receiver and the upper arm is connected to a purge connection. The improved refrigeration system further includes a two stage refrigeration system with the condenser of the high stage having a second section with a desuperheating coil therein to cool vapor refrigerant from the low stage compressor and supplying it to the high stage accumulator.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
(Not applicable)
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
(Not applicable)
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates generally to industrial refrigeration systems, and more particularly to an improved dry suction ammonia refrigeration system having a desuperheating coil, a modified accumulator, and a specially shaped and located purge connection.
(2) Background Information
A major drawback of industrial and commercial refrigeration systems which utilize ammonia as a refrigerant is a high cost of installation, operation, and maintenance. Conventional two stage refrigeration systems utilize a first stage which will provide refrigerant gas having a pressure of about 15 inches HG-0 psig from a low stage accumulator to a compressor, which will compress the gas to approximately 25-30 psi and discharge the compressed gas to a desuperheating coil, then through an oil separator to the second stage. The second stage will take this pressurized gas through a second compressor which increases the pressure to approximately 185 psig. This high pressure gas is then run through a condenser.
The inventors herein have found that a reduction in the heat of the gas through a desuperheating coil prior to running the gas through a second compressor, reduces the horse power required to compress the gas in the second stage compressor, and also extends the life of the compressor. This in turn results in reduced maintenance, wear, and overall cost and efficiency of the refrigeration system.
BRIEF SUMMARY OF THE INVENTION
It is therefore a general object of the present invention to provide an improved ammonia refrigeration system.
A further object is to provide an improved ammonia refrigeration system which reduces operating costs, installation costs, and maintenance costs as compared to conventional ammonia refrigeration systems.
Another object of the present invention is to provide an improved ammonia refrigeration system with a desuperheating coil located and connected so as to reduce the horse power required to compress the gas in the system.
Yet another object is to provide a refrigeration system with an improved accumulator design.
Still another object of the present invention is to provide an improved refrigeration system with a tee purge connection located to permit purging of gas downstream of the condenser.
Yet a further object of the present invention is to provide an improved refrigeration system which reduces operating costs, installation costs, and maintenance costs as compared to conventional refrigeration systems.
These and other objects of the present invention will be apparent to those skilled in the art.
The improved refrigeration system of the present invention includes an accumulator with a diffuser and velocity reducer pipe extending downwardly into the upper end of a vapor refrigerant tank, the return pipe extending from an evaporator and discharging vapor refrigerant therefrom into the tank. The diffuser pipe includes a lower end located within the interior of the tank which is expanded in diameter relative to the upper end, thereby reducing the velocity of fluid flowing through the pipe and entering the accumulator tank. A diffusion plate is mounted in the diffuser pipe, to further diffuse fluid flowing therethrough.
The improved refrigeration system also includes a tee having a stem portion extending horizontally from the condenser of the system, and a pair of upper and lower arms connected in a vertical orientation to the stem. The tee lower arm is connected to the receiver and the upper arm is connected to a purge connection. This allows for a positive separation and accumulation of noncondensable gases.
The improved refrigeration system further includes a two stage refrigeration system with the condenser of the high stage having a second section with a desuperheating coil therein to cool vapor refrigerant from the low stage compressor and supplying it to the high stage accumulator.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
The preferred embodiment of the invention is illustrated in the accompanying drawings, in which similar or corresponding parts are identified with the same reference numeral throughout the several views, and in which:
FIG. 1
is a detailed flow diagram of a single stage refrigeration system of the present invention;
FIG. 2
is an enlarged schematic view of the accumulator of the system shown in
FIG. 1
;
FIG. 3
is an enlarged elevational view of the accumulator shown in
FIG. 2
;
FIG. 4
is a super enlarged sectional view through the diffuser pipe of the accumulator shown in
FIG. 3
;
FIG. 5
is a plan view of the diffusion plate installed within the diffuser pipe shown in
FIG. 4
;
FIG. 6
is an enlarged schematic view of the condenser used in the system of
FIG. 1
;
FIG. 7
is a block flow diagram of a two stage refrigeration system;
FIG. 8
is a detailed schematic view of a two stage refrigeration system; and
FIG. 9
is an enlarged schematic view of the two stage system condenser showing the desuperheating coil of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, and more particularly to
FIG. 1
, a dry suction ammonia refrigeration system is designated generally at
10
, and a general flow diagram is schematically shown. Beginning at the control pressure receiver
12
, liquid refrigerant, preferably ammonia, is pushed to evaporators designated generally at
14
. The evaporators include processing units
14
a,
cooler units
14
b,
and a chiller
14
c.
Obviously, other types of uses are encompassed within the scope of this invention, although not detailed in this drawing. At each evaporator unit
14
a,
14
b,
and
14
c,
the flow of liquid is completely evaporated to form a dry suction gas. In order to distinguish between the forms of the refrigerant, solid line
16
indicates refrigerant in a liquid form, and dashed line
18
shows refrigerant in a dry suction gas form. The dry suction gas is moved from the evaporators
14
to accumulator
20
, where the gas is then drawn by a compressor
22
. At the compressor, the refrigerant gas is compressed and pumped to condenser
24
. Once condenser
24
transforms the gas back to a liquid, it is returned to receiver
12
for another cycle.
Referring now to
FIG. 2
, the accumulator
20
of the present invention is shown in enlarged schematic form. Accumulator
20
is of a relatively radical design that is not used in standard systems. Suction gas coming back from the plant would enter via conduit
26
, at a pressure of approximately 25-30 psi. Gas traveling to compressor
22
(shown in
FIG. 1
) would exit accumulator
20
via pipe
28
.
An electronic expansion valve
30
is installed upstream of accumulator
20
along conduit
26
, with probes
32
located to monitor the super heated gas entering accumulator
20
. Expansion valve
30
is installed along a line
34
which is tapped into the conduit
36
carrying liquid from the controlled pressure receiver
12
to the evaporators
14
. Expansion valve
30
is designed to protect the compressor
22
from overheating due to excessive super heated gas coming back from the plant. If the temperature of the super heated gas entering accumulator
20
becomes too high, the expansion valve
30
injects an amount of liquid refrigerant into the gas stream in conduit
26
to quench the excess heat.
Referring now to
FIG. 3
, accumulator
20
is shown in more detail. The accumulator
20
includes a containment vessel
38
having an upper portion
38
a
and a lower portion
38
b.
As shown in
FIG. 2
, accumulator
20
is designed to accumulate any refrigerant in the form of liquid within lower portion
38
b
and includes a fluid level control apparatus
40
of a conventional type to maintain the liquid level within lower portion
38
b.
A diffuser pipe
42
enters the upper end of vessel upper portion
38
a
and has an upper end connected to conduit
26
, to direct super heated gas into accumulator
20
.
As shown in
FIG. 4
, diffuser pipe
42
includes an upper end
42
a
connected to conduit
26
and equal in diameter to conduit
26
. Diffuser pipe includes a concentric reducer
42
b
downstream of upper portion
42
a,
which increases in diameter from its upper end to its lower end to approximately twice the diameter of upper portion
42
a
at its lower end. A lower portion
42
c
of diffuser pipe
42
extends vertically downward from the enlarged lower end of reducer
42
b.
Preferably, the lower end
42
c
of diffuser pipe
42
extends downward a distance approximately one-half the height of vessel upper portion
38
a,
but spaced above the liquid level in the vessel lower portion
38
b,
as shown in FIG.
3
. This diffuser pipe length assists in diffusing the super heated gas and causing it to swirl about within the vessel, thereby causing any liquid within the gas to accumulate within the vessel lower portion
38
b.
Referring once again to
FIG. 4
, reducer
42
b
will cause the velocity of refrigerant entering accumulator
20
from conduit
26
to reduce, because of the increase in diameter of the pipe from the upper portion
42
a
to the lower portion
42
c
in reducer
42
b.
This decrease in velocity also serves to diffuse the gas and assists in removing liquid from the gas.
In order to assist in diffusion, diffusion plate
44
may be installed within the upper end of lower portion
42
c
of diffuser piper
42
. Diffusion plate
44
includes a plurality of apertures
46
, as shown in
FIG. 5
, with the area of apertures
46
being approximately 1.5 times the cross-sectional inside area of conduit
26
and/or diffuser pipe upper portion
42
a.
For example, if conduit
26
has a diameter of six inches, diffusion plate
44
should have apertures with a cross-sectional area equal to about 1.5 times the cross-sectional area (about 29 square inches) of conduit
26
, equal to slightly more than 43 square inches. In addition, the side walls of each aperture
46
are preferably chamfered on the lower side, to function similar to reducer
42
b,
as refrigerant passes through each aperture
46
.
Referring once again to
FIG. 3
, accumulator vessel upper portion
38
a
includes dual outlet pipes
48
extending vertically out of vessel upper portion
38
a
and thence connected together and to outlet pipe
28
, as shown in FIG.
2
. While dual outlet pipes
48
are shown in the drawings, dual outlets are not a requirement for the invention, and a single outlet pipe would function adequately.
FIG. 3
additionally discloses reinforcing rings
50
mounted on vessel upper portion
38
a
around each of the outlet pipes
48
and the upper portion
42
a
of diffuser pipe
42
where it enters accumulator
20
.
Referring now to
FIG. 6
, the condenser
24
of the refrigeration system
10
is shown in enlarged schematic form. Condenser
24
is of conventional manufacture, but significant changes in the piping are used in the refrigeration system of this invention. Refrigerant in the form of gas having a pressure of approximately 110-185 psi is conveyed from compressor
28
(shown in
FIG. 1
) via inlet pipe
50
, to condenser
24
. The outlet pipe
52
is connected to the stem
54
a
of a full size tee
54
which is oriented with the stem
54
a
extending horizontally, and arms
54
b
and
54
c
extending vertically in opposing directions. The upper arm
54
b
of tee
54
has a full extension
56
of approximately 8-10 inches, which is capped. A purge valve
58
off of the cap of extension
56
is piped to a conventional purger. This feature allows a significant amount of noncondensable gases to accumulate and be purged. This improvement is necessary to remove noncondensable gases when condenser outlets are installed with mechanical traps. Once condenser
24
has condensed the refrigerant gas to liquid form, it exits the condenser through outlet pipe
52
. The noncondensable gases will collect in tee upper arm
54
b
and extension
56
for purging, while the condensed liquid refrigerant continues through the tee lower arm
54
c,
thence through a trap
60
, a check valve
62
, and thence via pipe
64
to the receiver, at a pressure of approximately 55-60 psi.
Referring now to
FIG. 7
, a two stage refrigeration system is shown in a block flow diagram, with a first stage having a lower pressure and lower temperature, and a second stage having a higher pressure and higher temperature. The high stage of the system of
FIG. 7
is identical to the single stage version of the invention shown in
FIG. 1
, and for this reason all components will be identified with the same reference numerals. Starting once again at the controlled pressure receiver
12
, liquid refrigerant is pushed to evaporators
14
, wherein the refrigerant is completely evaporated to a dry suction gas. The dry suction gas is moved to the accumulator
20
where it is then drawn in by compressor
22
. The refrigerant gas is compressed at compressor
22
and pumped to condenser
24
where the gas is condensed back to a liquid and flows back to the controlled pressure receiver
12
.
Liquid refrigerant from control pressure receiver
12
is pushed through a pipe to the low stage receiver
66
. The liquid refrigerant in low stage receiver
66
is pushed to the low temperature evaporator units
68
, where the liquid is completely evaporated to form a dry suction gas. The dry suction gas from evaporators
68
is brought to the low stage accumulator
70
where the gas is then drawn by the low stage compressor
72
. The gas is compressed in compressor
72
, and pumped to a desuperheating coil
74
within the high stage condenser
24
. After desuperheating the gas, the gas is brought back through an optional oil separator
76
to the high stage accumulator
20
. Excess liquid in the low stage accumulator
70
is pushed through a pipe to the suction of the high stage accumulator
20
utilizing a transfer system.
FIG. 8
is similar to
FIG. 7
, but utilizes component designations for the various boxes in the flow diagram of FIG.
7
. This dual stage refrigeration system utilizes a high temperature stage for things such as processing units, cooler units, and chillers, and a low temperature stage for evaporators, such as blast freezers, where a very low temperature is desired. Beginning with the high stage compressor, ammonia gas is pumped from the high stage accumulator
20
to the condenser
24
. At the condenser
24
, water and air are used to condense the ammonia gas back to a liquid. The liquid is pushed down to control pressure receiver
12
, which pushes the liquid through the plant to the various evaporators
14
a,
14
b,
and
14
c.
At each evaporator
14
a,
14
b,
and
14
c,
an electronic expansion valve is utilized to meter the flow of liquid to the exact proportions needed to do maximum cooling, without over feeding and causing liquid carryover. For extremely low temperature applications, such as a blast freezer where a temperature of 0° F. or lower is desired, the ammonia liquid is pushed from receiver
12
to a low temperature low pressure receiver
66
. Receivers
12
and
66
take the majority of the “flash” out of liquid ammonia, thereby making evaporators
14
a,
14
b,
and
14
c
and low temperatures evaporators
68
a
and
68
b,
more efficient. “Flash” has been a major problem for ammonia refrigeration systems, and has been known to cause an evaporator coil to lose as much as
10
percent of its capacity. The refrigeration system
10
greatly reduces this problem, and uses the pressure of the receivers to “pump” the liquid. This pressure is typically equal to the pressure a modern liquid ammonia pump would output, so that the efficiency of the “pumping” would not be compromised compared to the conventional liquid pumps.
Once the liquid ammonia is evaporated in the various evaporators
14
a,
14
b,
14
c,
68
a
and
68
b,
the ammonia gas is motivated back to the high stage accumulator
20
from evaporators
14
a,
14
b,
and
14
c,
and to low stage accumulator
70
from low temperature evaporators
68
a
and
68
b,
respectively. Once in accumulators
20
and
70
, the gas is simply suctioned back into the associated compressors
22
and
72
, respectively.
Referring now to
FIG. 9
, condenser
24
in the dual stage refrigeration system, includes the standard portion
24
which condenses gas from the high stage compressors via inlet pipe
50
and returns the condensed liquid through trap
60
and pipe
64
. The desuperheating coil
74
is located proximal condenser
24
, and takes gas from the low stage compressor
72
(shown in
FIGS. 7 and 8
) via line
78
, and removes heat via the desuperheating coil before the gas reaches the high stage accumulator
20
. To facilitate the efficient removal of oil, an oil separator
76
may be mounted in outlet line
80
from the desuperheating coil
74
.
Prior art dual stage refrigeration systems may pump high stage gas of approximately 185 psi through a coil to remove oil, and thence through a condenser. The present desuperheating coil differs significantly from this prior art in that the desuperheating coil is located after the low stage compression and prior to the high stage suction. This reduction of heat in the gas requires less horsepower for the high stage compressor to compress the gas from 30 psi to 185 psi, thereby extending the life of the compressor and increasing the efficiency of the system.
Whereas the invention has been shown and described in connection with the preferred embodiment thereof, many modifications, substitutions and additions may be made which are within the intended broad scope of the appended claims.
Claims
- 1. A two-stage refrigeration system, comprising:a high stage evaporator fed with liquid refrigerant and discharging a vapor refrigerant; a high stage compressor receiving vapor refrigerant from the high stage accumulator, for compressing the vapor refrigerant; a high stage condenser receiving compressed vapor refrigerant from the high stage compressor, for condensing it into liquid refrigerant; a controlled pressure receiver receiving the liquid refrigerant from the high stage condenser and supplying it to the high stage evaporator; a low stage receiver for receiving low temperature liquid refrigerant from the high stage accumulator, said low temperature liquid refrigerant having a lower temperature and pressure than the liquid refrigerant in the high stage, and supplying the low temperature liquid refrigerant to a low temperature evaporator; said low temperature evaporator evaporating the low temperature liquid refrigerant and discharging a low temperature vapor refrigerant; a low stage accumulator for accumulating low temperature vapor refrigerant discharged from the low stage evaporator; a low stage compressor receiving low temperature vapor refrigerant from the low stage accumulator, for compressing the low temperature vapor refrigerant and discharging compressed vapor refrigerant; and said high stage condenser including a second section for receiving and cooling the compressed low temperature vapor refrigerant and supplying it to the high stage accumulator.
US Referenced Citations (26)