U.S. patent application number 09/843717 was filed with the patent office on 2001-08-23 for brine cooling apparatus.
Invention is credited to Ichikawa, Yoshifumi, Morohoshi, Tsuneji.
Application Number | 20010015075 09/843717 |
Document ID | / |
Family ID | 17379567 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010015075 |
Kind Code |
A1 |
Ichikawa, Yoshifumi ; et
al. |
August 23, 2001 |
Brine cooling apparatus
Abstract
A brine cooling apparatus is provided which addresses an
environmental problem by not contributing to global warming and can
prevent brine from freezing within a heat exchanger. The apparatus
is structured such that a screw compressor, a condenser, a main
expansion valve and an evaporator are connected by a pipe so as to
cool brine flowing through the evaporator. The refrigerant is an
ammonia refrigerant, the evaporator is a plate type heat exchanger
constructed by laying a plural sheets of plates, and capacity
control means is provided in such a manner as to control a capacity
of the screw compressor in accordance with the flow amount of the
brine.
Inventors: |
Ichikawa, Yoshifumi;
(Shizuoka-shi, JP) ; Morohoshi, Tsuneji;
(Shizuoka-shi, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
17379567 |
Appl. No.: |
09/843717 |
Filed: |
April 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09843717 |
Apr 30, 2001 |
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09391079 |
Sep 16, 1999 |
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6253566 |
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Current U.S.
Class: |
62/434 ;
62/228.3 |
Current CPC
Class: |
F25B 49/022 20130101;
F25B 39/022 20130101; F28D 9/005 20130101; F25B 1/047 20130101;
F25B 47/006 20130101; F25B 2400/13 20130101; F28F 3/04
20130101 |
Class at
Publication: |
62/434 ;
62/228.3 |
International
Class: |
F25D 017/02; F25B
049/00; F25B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 1998 |
JP |
10-262713 |
Claims
What is claimed is:
1. A brine cooling apparatus comprising a compressor, a condenser,
a main expansion valve, an evaporator, a pipe for connecting the
compressor, the condenser, the main expansion valve and the
evaporator, a refrigerant evaporated by said evaporator, said brine
being cooled by evaporating the refrigerant by said evaporator,
wherein said refrigerant is an ammonia refrigerant; said evaporator
is a plate type heat exchanger constructed by stacking a plurality
of plates; and capacity control means are provided in such a manner
as to reduce an operating capacity of said compressor in the case
that the flow amount of said brine is reduced.
2. A brine cooling apparatus as claimed in claim 1, further
comprising suction pressure detecting means for detecting a suction
pressure of said compressor; and capacity control means provided in
such a manner as to reduce an operating capacity of said compressor
in the case that it is judged by said suction pressure detecting
means that the suction pressure of said compressor is lowered.
3. A brine cooling apparatus as claimed in claim 1, wherein an
operating capacity of said compressor is reduced in the case that
the suction pressure of said compressor is continuously lower than
or equal to a predetermined value for a fixed time.
4. A brine cooling apparatus as claimed in claim 1, wherein the
predetermined value of said suction pressure is set to a saturated
pressure corresponding to a temperature 5 to 10.degree. C. higher
than the brine freezing temperature.
Description
[0001] This application is a continuation application of U.S. Ser.
No. 09/391,079, filed Sep. 16, 1999.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a cooling apparatus for
circulating a cooled brine used for a freezing show case, a
refrigerating show case, a freezer, a refrigerator and the
like.
[0003] Conventionally, a freon refrigerant has been used as a
refrigerant employed in a compression type refrigerating machine,
however, by reconsidering an ozone layer breakage and an earth
warming-up, it has been considered in a cooling apparatus to employ
ammonia as a refrigerant. A flooded type cooling apparatus or a
liquid circulating type cooling apparatus are described, for
example, in Japanese Patent Unexamined Publication No. 10-170124 as
a cooling apparatus employed in an ammonia freezer.
[0004] Further, in order to reduce an amount of the refrigerant
sealed within a refrigerating cycle, it has been known to be proper
to use a plate type heat exchanger represented by a herringbone
plate, a corrugate plate and the like in an evaporator.
[0005] Since a large amount of refrigerant is required in the
flooded type and liquid circulating type cooling apparatuses in
accordance with the prior art, they do not address the problems of
the ozone layer breakage and global warming, and it is necessary to
sufficiently consider an efficiency, a risk and the like in the
case of employing ammonia.
[0006] Further, in the case of using the plate type heat exchanger,
it is necessary to consider a risk that an internal freezing is
generated when a flow rate of the brine is reduced and a heat
transmitting pipe forming the heat exchanger is clogged so as to be
deformed or broken.
SUMMARY OF THE INVENTION
[0007] An object of the present invention is to provide a brine
cooling apparatus which can solve the problems mentioned above,
prevent a brine from freezing within a heat exchanger, improve
reliability and secure a stable operation.
[0008] Further, another object of the present invention is to
provide a brine cooling apparatus which addresses an environmental
problem by reducing an amount of used refrigerant, reducing a fear
of breaking the ozone layer and preventing global warming.
[0009] Still further, another object of the present invention is to
provide a brine cooling apparatus which can secure an improvement
in performance with a reduced amount of a refrigerant, provide an
improved efficiency even when employing a natural type refrigerant,
and increase safety with respect to combustibility and a poison of
the natural type refrigerant.
[0010] Here, the present invention is constituted such as to solve
at least one of the problems mentioned above.
[0011] In order to achieve the objects mentioned above, in
accordance with the present invention, there is provided a brine
cooling apparatus including a screw compressor, a condenser, a main
expansion valve, an evaporator, a pipe for connecting the screw
compressor, the condenser, the main expansion valve and the
evaporator, a refrigerant evaporated by the evaporator, and brine
flowing through the evaporator. The brine is cooled by evaporating
the refrigerant by the evaporator. The refrigerant is an ammonia
refrigerant, the evaporator is a plate type heat exchanger
constructed by stacking a plurality of plates, and capacity control
means is provided in such a manner as to control a capacity of the
screw compressor in accordance with the flow rate of the brine.
[0012] Since ammonia is employed as the refrigerant, there is no
risk of breaking the ozone layer and warming the earth, and an
amount of the used refrigerant can be reduced to serve as an
evaporator. The plate type heat exchanger is structured by stacking
a plurality of plates. Then, since the capacity of the screw
compressor which can obtain a high output is controlled in
accordance with the flow rate of the brine, freezing within the
heat exchanger caused by reducing the amount of the sealed
refrigerant can be prevented and reliability can be improved.
[0013] Further, in accordance with the present invention, there is
provided a brine cooling apparatus including a screw compressor, a
condenser, a main expansion valve, an evaporator, a pipe for
connecting the screw compressor, the condenser, the main expansion
valve and the evaporator, a refrigerant evaporated by the
evaporator, and brine flowing through the evaporator, the brine
being cooled by evaporating the refrigerant by the evaporator. The
refrigerant is an ammonia refrigerant, the evaporator is a plate
type heat exchanger constructed by stacking a plurality of plates,
flow rate detecting means for detecting a flow rate of the brine is
provided, and capacity control means is provided in such a manner
as to reduce an operating capacity of the screw compressor in the
case that the reduction of the flow rate of the brine is detected
by the flow amount detecting means.
[0014] A cooling load is reduced together with a reduction of the
flow rate of the brine; however, since the operating capacity of
the screw compressor is reduced in the case that the reduction of
the flow amount of the brine is detected, a temperature of the
brine is not excessively lowered to a freezing temperature.
Accordingly, it is possible to prevent freezing within the heat
exchanger and improve reliability.
[0015] Still further, in accordance with the present invention,
there is provided a brine cooling apparatus including a screw
compressor, a condenser, a main expansion valve, an evaporator, a
pipe for connecting the screw compressor, the condenser, the main
expansion valve and the evaporator, a refrigerant evaporated by the
evaporator, and brine flowing through the evaporator, the brine
being cooled by evaporating the refrigerant by the evaporator. The
refrigerant is an ammonia refrigerant, the evaporator is a plate
type heat exchanger constructed by stacking a plurality of plates,
and suction pressure detecting means for detecting a suction
pressure of the compressor and capacity control means are provided
in such a manner as to reduce an operating capacity of the screw
compressor in the case that it is judged by the suction pressure
detecting means that the suction pressure of the compressor is
lowered.
[0016] When the flow rate of the brine is reduced, the cooling load
is reduced and the suction pressure of the compressor is lowered.
Then, in the case that it is judged by the suction pressure
detecting means that the suction pressure of the compressor is
lowered, the operating capacity of the screw compressor is reduced,
so that it is possible to prevent the brine within the heat
exchanger from freezing during a normal continuous operation.
[0017] Furthermore, in accordance with the present invention, there
is provided a brine cooling apparatus including a screw compressor,
a condenser, a main expansion valve, an evaporator, a pipe for
connecting the screw compressor, the condenser, the main expansion
valve and the evaporator, an ammonia refrigerant evaporated by the
evaporator, and brine flowing through the evaporator, the brine
being cooled by evaporating the refrigerant by the evaporator. The
evaporator is a plate type heat exchanger constructed by stacking a
plurality of plates, and capacity control means for controlling a
capacity of the screw compressor, suction pressure detecting means
for detecting a suction pressure of the compressor, and capacity
control means for reducing an operating capacity of the screw
compressor in the case that the suction pressure of the compressor
is continued lower than or equal to a predetermined value for a
fixed time are provided.
[0018] Accordingly, since the operating capacity of the screw
compressor is reduced in the case that the suction pressure of the
compressor is continued lower than or equal to a predetermined
value for a fixed time, it is possible to securely prevent the
brine within the heat exchanger from freezing during a normal
continuous operation, so that the plate type heat exchanger can be
used for the exchanger in order to reduce the amount of the ammonia
sealed within the refrigerating cycle, and the structure can be
made preferable for preventing the ozone layer breakage and the
global warming.
[0019] Further, in accordance with the present invention, in the
brine cooling apparatus mentioned above, it is desirable to set the
predetermined value of the suction pressure to a saturated pressure
corresponding to a temperature 5 to 10.degree. C. higher than the
brine freezing temperature.
[0020] Still further, in accordance with the present invention, in
the brine cooling apparatus mentioned above, it is preferable to
reduce the operating capacity of the screw compressor from a 100%
operating capacity to a 50% operating capacity in view of an
operating efficiency and the like in the case of again returning to
a cooling operation from the operation for preventing the
freezing.
[0021] Furthermore, according to the present invention, in the
brine cooling apparatus mentioned above, it is advantageous to
employ a pressure switch as the suction pressure detecting means in
view of cost reduction and reliability.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic view of a cycle system of a brine
cooling apparatus in accordance with an embodiment of the present
invention;
[0023] FIG. 2 is a perspective view of a structure of a plate type
heat exchanger 6 in accordance with an embodiment of the present
invention;
[0024] FIG. 3 is a schematic view of a method of connecting a pipe
of a pressure switch 10 for preventing a freezing in accordance
with an embodiment of the present invention;
[0025] FIG. 4 is a graph of a change of a suction pressure of a
screw compressor in accordance with an embodiment of the present
invention;
[0026] FIG. 5 is a schematic view of a sequence circuit in
accordance with an embodiment of the present invention; and
[0027] FIG. 6 is an operation table of a capacity control
electromagnetic valve 19 in accordance with an embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Hereinafter, an embodiment in accordance with the present
invention will be described with reference to FIGS. 1 to 6.
[0029] FIG. 1 is a schematic view of a cycle system in an ammonia
refrigerating cycle, in which a solid line shows a flowing
direction of a refrigerant and a broken line shows a flowing
direction of a refrigerating machine oil. A compressor is
structured such that open-type screw compressors 1 are arranged in
two stages, an ammonia (gas) is compressed by low stage and high
stage rotors in the screw compressor 1 so as to become a gas having
a high temperature and a high pressure and be discharged together
with the refrigerating machine oil, thereby being separated into
the refrigerant gas and the refrigerating machine oil within an oil
separator 2.
[0030] The refrigerant gas is condensed to a condensed liquid by a
cooling water in a condenser 3, is further lowered in temperature
by a supercooler 4, becomes a wet gas having a low temperature by a
main expansion valve 5, and is sucked into the screw compressor 1
after an operation of cooling brine corresponding to a cooled
subject within a plate type heat exchanger 6 corresponding to an
evaporator.
[0031] FIG. 2 is a perspective view which shows a structure of
brine outlet and inlet ports in the plate type heat exchanger, and
the brine is flowed into from an upper inlet port in the plate type
heat exchanger. The ammonia refrigerant is evaporated, whereby the
brine is cooled while flowing toward the lower portion from the
upper portion and is discharged from a lower outlet port in a state
that its temperature is reduced.
[0032] When a flow rate of the brine is reduced, a flow of the
brine becomes non-uniform within the plate type heat exchanger 6,
so that in comparison with a flow passage having a normal flow
within the plate, a passing speed of the brine is significantly
lowered or the brine does not flow so as to be stayed. Accordingly,
the brine staying within the plate type heat exchanger 6 is cooled
in accordance that the ammonia refrigerant is evaporated within the
plate type heat exchanger 6, and gradually starts freezing.
[0033] Since an evaporation of the ammonia refrigerant is
continued, the freezing of the brine is further increased and the
flow rate of the brine is reduced, so that there is a case that an
air is mixed into the plate type heat exchanger 6. Accordingly, a
concentration of the brine is lowered, a freezing temperature is
increased and brine freezing is easily caused.
[0034] When the brine is frozen within the plate type heat
exchanger 6, there is a case that each of the stacked plates is
deformed or broken, so that the ammonia refrigerant is leaked
within the brine cycle or leaked out to an external portion,
whereby there is a risk of applying an influence such as corrosion
and the like to the other equipment.
[0035] On the other hand, the refrigerating machine oil separated
by the oil separator 2 is discharged to an oil tank 7 and enters
into an oil cooler 8 from the oil tank 7. The refrigerating machine
oil cooled by the cooling water in the oil cooler 8 is supplied to
bearing portions 15a and 15b and a shaft sealing apparatus portion
16 corresponding to an intermediate pressure portion of the screw
compressor 1 after a foreign substance in the oil is removed in an
oil strainer 9.
[0036] FIG. 3 is a schematic view which shows a method of
connecting a pipe of a pressure switch 10 for preventing freezing,
in which a compound pressure gauge 11 displaying a suction pressure
of the screw compressor 1 is connected to a suction pressure
portion of the screw compressor 1 via a service valve 17 by a pipe
12, the pipe 12 is branched, and one of the branched pipes is
connected to the freezing preventing pressure switch 10 by a pipe
13 having the same size so as to detect the suction pressure of the
screw compressor 1.
[0037] FIG. 4 is a graph which shows a change of the suction
pressure of the screw compressor 1, FIG. 5 shows a sequence circuit
for detecting the suction pressure so as to perform a capacity
control, and FIG. 6 shows an operation of the capacity controlling
electromagnetic valve.
[0038] In the compressor 1, at a time of 100% load, capacity
controlling electromagnetic valves (20A and 20C) 19a and 19c are in
an open state, and when the flow rate of the brine within the plate
type heat exchanger 6 is reduced during the operation under 100%
load, a cooling load is also reduced, so that the main expansion
valve 5 performs a control in a closing direction and the suction
pressure is lowered.
[0039] Then, in the case that the suction pressure of the screw
compressor 1 is lowered to a set value of the freezing preventing
pressure switch 10 and this value is continued for a set time of a
time limit relay 18, the respective capacity controlling
electromagnetic valves (20B and 20C) 19b and 19c of the two-stage
screw compressor 1 are energized so as to be in an open state,
thereby shifting an operation capacity to a 50% load capacity
control operation.
[0040] Due to the capacity control operation, a cooling capacity of
the compressor 1 is reduced, thereby preventing the brine storing
within the plate type heat exchanger 6 from lowering to a freezing
temperature.
[0041] Thereafter, the 50% load capacity control operation is
performed until the suction pressure is increased and returned to a
return value of the freezing preventing pressure switch 10, and
thereafter, the operation capacity of the screw compressor 1 is
returned to the 100% load so as to again perform the cooling
operation.
[0042] A change of the suction pressure caused by a temperature
reduction of the brine is detected at the suction pressure portion
of the screw compressor 1, a saturated temperature corresponding to
the suction pressure is set such as to be only a degree of the
saturated temperature corresponding to a pressure loss within the
plate type heat exchanger 6 and within the suction pipe 14 lower
than an evaporating temperature of the ammonia refrigerant within
the plate type heat exchanger 6.
[0043] That is, in the case that the suction pressure of the
compressor is continued equal to or less than the predetermined
value for a fixed time, the operation capacity of the screw
compressor is reduced, thereby securely preventing the brine
freezing within the heat exchanger during the normal continuous
operation. Then, in order to reduce the amount of the ammonia
sealed within the refrigerating cycle, the plate type heat
exchanger is employed for the heat exchanger, thereby reducing a
risk that the ozone layer is broken and the earth is warmed.
Further, it is desirable to set the set value of the suction
pressure to the saturated pressure corresponding to a temperature 5
to 10.degree. C. higher than the brine freezing temperature,
whereby a safer countermeasure can be obtained for preventing the
brine freezing. Further, it is sufficient that the brine in this
case is a fluid corresponding to the subject to be cooled, so that
water can be employed as the brine.
[0044] In the brine cooling apparatus, in the case of constructing
the refrigerating cycle by using ammonia as the refrigerant, it is
possible to set the amount of ammonia sealed within the
refrigerating cycle to a minimum refrigerant amount by employing a
plate type heat exchanger 6 for the brine cooler.
[0045] Further, if the internal freezing of the plate type heat
exchanger 6 caused by the reduction of the flow rate of the brine
is previously prevented, it is possible to avoid a risk that the
ammonia refrigerant is leaked by the breakage of the plate.
[0046] Still further, when the 50% load capacity control operation
of the screw compressor 1 is performed by the operation of the
freezing preventing pressure switch 10 and the suction pressure is
increased to the return value of the freezing preventing pressure
switch 10, the operation capacity of the screw compressor 1 is set
to the 100% load so as to again return the operation to the cooling
operation, whereby it is possible to avoid the brine freezing
within the plate type heat exchanger 6 during the normal continuous
operation without abnormally stopping the unit due to the internal
freezing of the brine.
[0047] In accordance with the present invention, ammonia is
employed as the refrigerant having no risk of breaking the ozone
layer and warming the earth, the amount of the used refrigerant is
reduced by employing the plate type heat exchanger structured such
that a plurality of plates are layered for the evaporator, and the
capacity of the screw compressor is controlled in accordance with
the flow rate of the brine, so that it is possible to prevent the
refrigerant from freezing within the heat exchanger caused by the
reduction of the sealed amount of the refrigerant and it is
possible to provide brine cooling apparatus having an improved
reliability.
[0048] Further, in accordance with the present invention, since the
operation capacity of the screw compressor is reduced in the case
that the reduction of the brine flow amount is detected, the
temperature of the brine is not excessively lowered to the freezing
temperature, and it is possible to provide brine cooling apparatus
having an improved reliability.
[0049] Still further, in accordance with the present invention,
since the operation capacity of the screw compressor is reduced in
the case that it is judged by the suction pressure detecting means
that the suction pressure of the compressor is lowered, the
reduction of the suction pressure of the compressor invites the
reduction of the cooling load and the reduction of the brine flow
rate, so that it is possible to prevent the brine within the heat
exchanger from freezing during the normal continuous operation.
[0050] Furthermore, in accordance with the present invention, since
the operation capacity of the screw compressor is reduced in the
case that the suction pressure of the compressor is continuously
equal to or less than the predetermined value for the predetermined
time, and the plate type heat exchanger is employed for the heat
exchanger, it is possible to securely prevent the brine from
freezing and reduce the amount of ammonia sealed within the
refrigerating cycle, thereby providing a brine cooling apparatus
preferable for preventing the ozone layer breakage and global
warming.
* * * * *