JP3593480B2 - Seawater cooling system - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a seawater cooling system that cools a condenser of a refrigerator or a steam turbine using seawater.
[0002]
[Prior art]
BACKGROUND ART In recent years, district cooling and heating systems have been adopted because of the advantages that air pollution can be prevented and energy can be used efficiently. In particular, in various buildings constructed on the waterfront, such as in the vicinity of the bay shore or in marine land, air-conditioning is performed using an energy plant, which is a single heat-generating facility, thereby reducing the cost, maintenance, and space of the facility. Becomes possible. In air conditioning of such a facility on the waterfront, abundant seawater is used as a cooling source. This example is the heat supply unused energy feature NO. 3 "Heat supply in Cosmosquare area using seawater heat" is described in Japan Heat Supply Association 1993.
[0003]
In this document, fresh water is circulated as cooling water for a refrigerator for air conditioning using fresh water, and the fresh water is exchanged with seawater for cooling. In the heat exchanger for exchanging heat between fresh water and seawater, the temperature difference between the inlet temperature and the outlet temperature of the heat exchanger on the seawater side is set to 5 to 6 ° C. The amount of seawater pumped into the refrigerator is controlled so that environmental destruction does not occur when discharging seawater into the sea.
[0004]
On the other hand, as for fresh water that exchanges heat with seawater, even if the temperature of the fresh water at the outlet of the heat exchanger is high, the performance of the refrigerator is slightly reduced. Tend to set. When the amount of cooling water is reduced, power such as pump power for transporting the cooling water can be reduced, and the pipe diameter can be reduced, so that the construction cost can be significantly reduced. As a result, in a heat exchanger that exchanges heat between freshwater and seawater, the temperature difference on the freshwater side is more than twice the temperature difference on the seawater side.
[0005]
Further, when seawater is used for cooling, dust and the like adhere to the heat exchanger, so that the heat exchanger needs to be washed. An example of removing dirt from a heat exchanger contaminated with seawater is described in the refrigeration "Introduction of NEDO Unused Energy Utilization Project" vol. 73, no. 853, pp. 88-92, November 1998.
[0006]
[Problems to be solved by the invention]
By the way, a plate heat exchanger is generally used as a heat exchanger for exchanging heat between fresh water and seawater. In this plate heat exchanger, fresh water and seawater alternately flow between the plates. The size of the plate heat exchanger is minimized when the inlet and outlet temperature differences and flow rates between seawater and freshwater are about the same. As described above, since the temperature difference on the seawater side in the conventional heat exchanger is about half of the temperature difference on the freshwater side, the circulation amount of seawater is about twice the circulation amount of freshwater. For this reason, in a plate heat exchanger that exchanges heat between seawater and freshwater, more plates than the number of plates required for heat transfer are required to guide seawater in the heat exchanger. As a result, there is a problem that the size of the heat exchanger becomes large.
[0007]
Further, since a large amount of seawater is guided to the plate heat exchanger in order to reduce the temperature difference of the seawater, the power of the seawater pump is increased. Furthermore, since microorganisms in seawater may adhere to the refrigeration system and generate slime and algae, a filter is required at the seawater inlet to filter seawater. The vessel also becomes large, and the cost increases.
[0008]
On the other hand, in the method described in the literature for removing dirt from the heat exchanger due to seawater, the seawater in the heat exchanger is discharged out of the system, and then hot water or ozone water is passed through to kill marine organisms attached to the plate. Then, dirt is removed by air bubbling. According to this method, a boiler for generating hot water, an ozone generator, and the like are required, and the convenience of using seawater may be impaired.
[0009]
The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to reduce the size of a seawater cooling system used for a refrigerator while preserving the marine environment. It is another object of the present invention to realize both conservation of the marine environment and reduction of the power required for the refrigerator. Still another object of the present invention is to achieve both the conservation of the marine environment and the reduction of construction and manufacturing costs of refrigerators.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a refrigeration system having a bleed condensing steam turbine, a condenser, a turbo chiller driven by the bleed condensing steam turbine, and an absorption chiller, and the refrigeration system is distributed. A plurality of heat exchangers for exchanging freshwater cooling water with seawater, a seawater intake pipe that supplies seawater to the plurality of heat exchangers and has an intake pump, and seawater that returns seawater from the respective heat exchangers to the sea A seawater cooling system including a return pipe is configured. And the first feature is that a second seawater intake pipe for mixing low-temperature seawater with high-temperature seawater flowing out of the seawater return pipe is provided, and this second seawater intake pipe is connected to the seawater return pipe, Seawater strainer was installed in the seawater intake pipe.
[0013]
And, the temperature difference between the temperature of the fresh water that flows to the temperature of the fresh water flowing into the heat exchanger, to a temperature difference between the temperature of the seawater flows out temperature of seawater flowing into the heat exchanger at approximately the same Is desirable.
[0014]
Further, a second feature is that each of the plurality of heat exchangers is provided with a replacement means for replacing seawater flowing inside the heat exchanger with fresh water. The replacement means includes a first bypass pipe having a first valve means provided in the seawater intake pipe, a second bypass pipe having a second valve means provided in the seawater return pipe, and a seawater intake means. and third valve means have, have a fourth valve means provided in the seawater return pipe, a pipe connecting the fresh water side outlet and freshwater side inlet of the condenser, a pump interposed in the pipe And a check valve, so that when seawater in the heat exchanger is replaced with freshwater, freshwater circulates between the pipe and the condenser.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of one embodiment of an air conditioning system according to the present invention. The air-conditioning system is an air-conditioning system that air-conditions a waterfront or a building that is buried offshore, for example, at an airport. An air conditioning system for cooling an airport building or the like includes a bleed condensing turbine 1, a generator 2, a condenser 4, a turbo compressor 7, an evaporator 8, a condenser 9, an absorption refrigerator 13, a plurality of fresh water and sea water. 17m (m: indicates the m-th), freshwater pump 16, seawater pump 18, seawater bypass pump 20, seawater filter 22, and steam pipes 3, 5, and 6 connecting these devices. , A freshwater pipe 15, a seawater pipe 19,..., 19m (m: indicates the m-th), 21, 23, 24, and the like.
[0016]
The cooling fresh water is cooled by sea water in the fresh water / sea water heat exchangers 17,..., 17m, and then pressurized by the fresh water pump 16. Then, it flows through the condenser 9 of the turbo refrigerator, the absorption refrigerator 13, and the condenser 4 through the fresh water pipe 15 in this order, and cools each apparatus. At that time, the temperature of the fresh water itself rises, and the fresh water is returned to the heat exchangers 17,..., 17m of the sea water and is cooled again by the sea water. Thereafter, this circulation is repeated.
[0017]
On the other hand, seawater is pumped from the sea by an intake pump 21 and supplied to seawater pumps 18, ..., 18m via seawater pipes 23, 19, ..., 19m. The seawater pumps 18,..., 18m supply the required amount of seawater to the heat exchangers 17,. The outlet temperature of freshwater in the summer in the freshwater / seawater heat exchangers 17,..., 17m rises to about 28 ° C because the seawater temperature is about 25 ° C.
[0018]
The fresh water that has risen to 28 ° C. cools the condenser 9 and the absorption refrigerator 13 of the centrifugal chiller, raises the temperature, and flows into the condenser 4. In the condenser 4, the steam discharged from the steam turbine 1 is cooled to liquefy the steam. The temperature of the fresh water is further increased by this steam turbine, and is returned to the heat exchanger 17,..., 17m of the fresh water and the seawater at about 40 ° C. to 45 ° C. Therefore, the temperature difference between the fresh water and sea water heat exchangers 17,..., 17m on the fresh water side is as large as 12 ° C. to 17 ° C.
[0019]
The seawater is supplied to the fresh water and seawater heat exchangers 17,..., 17m at about 25 ° C. by the seawater pumps 18,. Then, in this heat exchanger, the temperature rises to the same temperature difference as that of fresh water, and the temperature of the heat exchanger becomes 37 ° C. to 42 ° C. and flows out of the heat exchangers 17,. When the temperature difference between the inlet and the outlet of the heat exchanger is substantially the same between fresh water and seawater, the heat transfer coefficient of the freshwater and seawater is substantially the same, so that the heat exchanger can be downsized. At this time, the respective flow rates of seawater and freshwater flowing through the heat exchanger are also substantially the same.
[0020]
By the way, since the seawater flowing out of the heat exchangers 17,..., 17m has a high temperature, if it is discharged into the sea as it is, the sea environment is disturbed. Therefore, a part of the cold seawater taken from the water intake pipe 23 is bypassed by the bypass pipe 21. The seawater bypass pump 20 is interposed in the bypass pipe 21. The bypass pipe 21 is connected to the seawater discharge pipe 24 flowing out of the heat exchangers 17,..., 17m. Then, by mixing the seawater flowing out of the heat exchangers 17,..., 17m with the cold seawater that has just been taken, the temperature of the seawater discharged into the sea can be reduced to a temperature that does not affect the environment. .
[0021]
The seawater pumps may be only the intake pumps 18,..., 18m, and bypass pipes may be connected from the inlets of the heat exchangers 17,. However, in this case, since seawater that is bypassed to lower the discharge temperature is also passed through the heat exchanger, it is necessary to increase the pressure to a pressure required for flowing through the heat exchanger.
[0022]
Further, as seawater pumps, pumps 18, ..., 18m having a head of about 15 to 20m for supplying seawater to the heat exchangers 17, ..., 17m of fresh water and seawater, and a seawater bypass pump 20 having a head of about 5m are provided. If a staged pump is used, there is no need to increase the pressure of the seawater to be bypassed, so the boosted amount of the bypassed seawater is reduced to 1/3 to 1/4 of that in the single stage. Therefore, the total pump power can be reduced.
[0023]
Further, as shown in FIG. 2, a pump 25 may be provided in the main water intake line, and a control valve 26 may be provided in the bypass line 21. In this manner, when the amount of seawater that exchanges heat with the cooling water is small, or when the temperature of the seawater that exchanges heat with the cooling water is low, the control valve 26 can be throttled to reduce the required power of the pump 25. Become.
[0024]
Since seawater contains a lot of debris, the seawater intake has a screen that removes large debris that may interfere with the operation of the pump, and the line that supplies the heat exchanger contains debris in the heat exchanger. Each is fitted with a fine-grained, automatic-cleaning filter to prevent clogging and preventing seawater from flowing.
[0025]
According to this embodiment, since the seawater supplied to the heat exchanger and the bypass seawater for cooling the seawater discharged into the sea from the heat exchanger are separated, the bypass seawater is not filtered, and the heat exchanger is not filtered. If a seawater filter is provided only in the seawater line supplied to the seawater, the amount of seawater passing through the seawater filter 22 is reduced by about half compared with the conventional case, the capacity of the seawater filter 22 is reduced by half, and cost reduction is achieved. Will be possible.
[0026]
Furthermore, if the rotation speed of the seawater bypass pump 20 is controlled according to the cooling load so that the seawater discharge temperature difference becomes constant, a wasteful bypass of seawater becomes unnecessary, and the pump power can be further reduced.
[0027]
Meanwhile, marine organisms may adhere to the seawater side of the heat exchangers 17,..., 17m of freshwater and seawater, so that heat transfer may be hindered. Therefore, it is necessary to periodically clean the seawater side. As described above, a method of replacing the seawater side with freshwater and then increasing the temperature of the freshwater to a temperature at which marine organisms are killed and washing is often adopted from the viewpoint of marine environmental conservation. In the case of cooling using seawater, since the seawater intake temperature is about 25 ° C, the vicinity of this temperature is the living temperature range of marine organisms. Marine organisms are thought to die.
[0028]
Since the apparatus becomes complicated in this method, an example of a more simplified seawater cooling system is shown in FIG. The embodiment shown in FIG. 3 is the same as the above-described embodiment except for the heat exchangers 17,... A case where only one of the plurality of heat exchangers 17,..., 17m is cleaned is taken as an example.
[0029]
Among the m heat exchangers 17,..., 17m to be cleaned, only one heat exchanger 17 closes the seawater side stop valves 38, 39 and slightly opens the fresh water stop valves 36, 37. At this time, both the fresh water and the seawater are passed through the other heat exchangers 17m,... To put the refrigerator system into an operating state. The seawater discharge valve 28 of the heat exchanger 17 to be washed is opened, and the seawater in the heat exchanger 17 is drained. After extracting seawater, the freshwater supply valve 27 is opened, and the inside of the heat exchanger 17 is filled with freshwater.
[0030]
When each valve is set in this way, a small amount of fresh water heated by the refrigerator system and heated to a high temperature flows through the heat exchanger 17. Then, finally, the internal temperature of the entire heat exchanger 17 reaches the fresh water temperature returned from the refrigerator system. When the temperature of the heat exchanger 17 rises to the returned freshwater temperature, the marine organisms attached to the heat exchanger 17 die. Eventually, the marine organisms separate from the heat transfer surface of the heat exchanger 17. Since the inside of the heat exchanger 17 is heated from the freshwater side, the temperature of the side to which the marine organisms are attached becomes high, and the marine organisms are easily peeled.
[0031]
Depending on the season, the seawater temperature may be lower and the freshwater return temperature from the refrigerator system may be lower. Further, the load on the refrigerator system may be reduced, and the fresh water return temperature may be reduced. In order to prevent such a problem, a temperature sensor 29 for detecting a fresh water return temperature of the refrigerator system is provided, and a temperature controller 30 is required for cleaning based on the temperature detected by the temperature sensor 29 when cleaning the heat exchanger. The freshwater flow rate is controlled to increase the temperature. Specifically, the temperature controller 30 instructs the control valve 31 to be throttled.
[0032]
When the cleaning is completed, the control valve 31 is returned to the fully opened state. In addition, the fresh water supply valve 27 and the sea water discharge valve 28 are closed, and the sea water stops 38, 39 and the fresh water stop valves 36, 37 are fully opened to return to the normal operation.
[0033]
FIG. 4 shows a modification of the above embodiment. This modification differs from the above embodiment in that a pipe 34 for circulating the condenser 4 is provided in the freshwater circulation path. When washing the fresh water and seawater heat exchangers 17,..., 17m, if the circulation amount of fresh water flowing back to the refrigerator is excessively reduced, the cooling water outlet temperature of the refrigerator becomes high, which hinders the operation of the refrigerator. May come.
[0034]
At this time, the circulation amount of fresh water is reduced to such an extent that the operation of the refrigerator is not hindered. The fresh water on the outlet side of the condenser 4 circulates through the condenser 4 by a bypass pump 32 provided in a pipe 34 returning to the inlet side, and when the fresh water outlet temperature of the condenser 4 rises to a temperature required for washing, heat is generated. , 17m.
[0035]
The pipe 34 is provided with a check valve 33 to prevent fresh water from returning to the condenser 4 when the heat exchangers 17,..., 17m are not washed. The rotation speed of the bypass pump 32 is controlled using an inverter so that the fresh water return temperature becomes a temperature required for washing. Note that a control valve may be attached instead of the rotation speed control to adjust the amount of bypass water.
[0036]
According to this embodiment, a dedicated heating device such as a boiler is not required for cleaning the fresh water and seawater heat exchangers. Therefore, the cost of the refrigerator system that uses the seawater for cooling can be reduced. Further, since a heating source such as a boiler is not required, maintenance is facilitated and running costs are reduced.
[0037]
【The invention's effect】
According to the present invention, in the seawater cooling system that cools the cooling water with seawater, the temperature of the heat exchanger inlet of the circulating fresh water is increased, and the seawater after the heat exchange is mixed with the freshly taken seawater. The size of the air conditioning system can be reduced. In addition, power consumption can be reduced by miniaturization.
[Brief description of the drawings]
FIG. 1 is a system flow diagram of an embodiment of a seawater cooling system according to the present invention.
FIG. 2 is a system flow diagram of another embodiment of the seawater cooling system according to the present invention.
FIG. 3 is a system flow diagram of still another embodiment of the seawater cooling system according to the present invention.
FIG. 4 is a system flow diagram of still another embodiment of the seawater cooling system according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Extraction ascites turbine, 2 ... Generator, 3 ... Inlet steam piping, 4 ... Condenser, 5 ... Condensing steam piping, 6 ... Extraction steam piping, 7 ... Turbo compressor, 8 ... Evaporator, 9 ... Condenser 10: refrigerant discharge pipe, 11: refrigerant expansion device, 12: refrigerant suction pipe, 13: absorption refrigerator, 14: cold water pipe, 15: fresh water pipe, 16: fresh water pump, 17: heat exchanger, 17m: m-th Heat exchanger, 18 ... seawater pump, 18m ... mth seawater pump, 19 ... heat exchange seawater pipe, 19m ... mth heat exchange seawater pipe, 20 ... seawater bypass pump, 21 ... seawater bypass pipe, 22 ... seawater Filter, 23: Seawater intake piping, 24: Seawater discharge piping.

Claims (3)

A refrigeration system having an bleed condensing steam turbine, a condenser, a turbo chiller and an absorption chiller driven by the bleed condensing steam turbine, and heat-exchanging fresh water cooling water flowing through the refrigerating system with seawater. In a seawater cooling system including a plurality of heat exchangers, a seawater intake pipe that supplies seawater to the plurality of heat exchangers and has a water intake pump, and a seawater return pipe that returns seawater from the respective heat exchangers to the sea. ,
A second seawater intake pipe for mixing low-temperature seawater with high-temperature seawater flowing out of the seawater return pipe is provided. This second seawater intake pipe is connected to the seawater return pipe, and seawater is supplied to the seawater intake pipe. Seawater cooling system characterized by having a strainer. The temperature difference between the temperature of freshwater flowing into the heat exchanger and the temperature of freshwater flowing out, and the temperature difference between the temperature of seawater flowing into the heat exchanger and the temperature of seawater flowing out are substantially the same. The seawater cooling system according to claim 1, wherein A refrigeration system having an bleed condensing steam turbine, a condenser, a turbo chiller and an absorption chiller driven by the bleed condensing steam turbine, and heat-exchanging fresh water cooling water flowing through the refrigerating system with seawater. In a seawater cooling system including a plurality of heat exchangers, a seawater intake pipe that supplies seawater to the plurality of heat exchangers and has a water intake pump, and a seawater return pipe that returns seawater from the respective heat exchangers to the sea. ,
Each of the plurality of heat exchangers is provided with replacement means for replacing seawater flowing inside the heat exchanger with fresh water, and the replacement means has a first valve means provided on the seawater intake pipe. A second bypass pipe having a second pipe means provided in the seawater return pipe, a third valve means provided in the seawater intake means, and a fourth valve provided in the seawater return pipe Having means,
A pipe connecting the freshwater-side outlet and the freshwater-side inlet of the condenser, a pump interposed in the pipe, and a check valve; this pipe is used when seawater of the heat exchanger is replaced with freshwater. And fresh water circulating between the condenser and the condenser.

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