KR20190040058A - Ship cooling system - Google Patents

Abstract

The cooling system of the ship includes a heat exchanger for performing heat exchange between clean water and seawater, a temperature control valve for changing the ratio of the flow rate of fresh water passing through the heat exchanger and the flow rate of fresh water flowing through the bypass line, The rotation speed of the seawater pump is controlled via the inverter so that the temperature detected by the temperature sensor after the fresh water cooling is maintained at the set temperature while the temperature control valve is controlled so that the rotation speed of the seawater pump is the minimum rotation speed, And a control device for controlling the temperature control valve so that the temperature detected by the temperature sensor after the fresh water cooling is maintained at the lower limit temperature lower than the set temperature when the temperature detected by the temperature sensor is lower than the set temperature.

Description

Ship cooling system

The present invention relates to a cooling system of a ship.

Generally, in ships, fresh water circulates between the main engine and the heat exchanger in order to cool the main engine, and heat exchange between fresh water and seawater is performed in the heat exchanger. For example, Patent Document 1 discloses a ship cooling system 100 as shown in Fig.

Specifically, in the cooling system 100, seawater is led from the outside of the hull to the heat exchanger 110 by the first seawater line 151, and is discharged from the heat exchanger 110 to the outside of the hull by the second seawater line 152 It is delivered. A seawater pump 160 is installed in the first sea water line 151. The fresh water that performs heat exchange with the seawater in the heat exchanger 110 is led from the heat exchanger 110 to the main engine 120 by the first fresh water line 131, (120) to the heat exchanger (110).

A bypass line 133 is connected to the first fresh water line 131 and the second fresh water line 132 to bypass the heat exchanger 110. The ratio of the flow rate of fresh water passing through the heat exchanger 110 and the flow rate of fresh water flowing through the bypass line 133 is changed by the temperature control valve 140. The temperature control valve 140 is controlled by the controller 170. [

The controller 170 controls the temperature regulating valve 140 such that the temperature of fresh water supplied to the main engine 120 is constant. The control device 170 controls the rotation speed of the seawater pump 160 through the inverter 175 so that the opening degree of the temperature control valve 140 on the heat exchanger 110 approaches the target opening degree.

Japanese Patent Application Laid-Open No. 2009-274469

However, in the cooling system 100 shown in Fig. 4, the fuel consumption of the main engine 120 can be further improved.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a cooling system for a ship capable of further improving the fuel efficiency of the main engine.

As a result of intensive studies, the inventors of the present invention have found that, when the main engine is a reciprocating engine, fresh water is supplied not only to the main engine but also to an air cooler that cools the air supplied to the main engine from the supercharger , It is devised that the fuel efficiency of the main engine is improved by lowering the temperature of fresh water supplied to the air cooler and realizing the control method. The present invention has been made in view of this.

A cooling system for a ship according to one aspect of the present invention comprises a heat exchanger for performing heat exchange between fresh water and seawater to cool the fresh water, a first seawater line for delivering seawater to the heat exchanger from the outside of the ship, A first fresh water line for guiding fresh water to an air cooler for cooling the air supplied to the main engine from the main engine and the turbocharger, which are reciprocating engines of the ship, from the heat exchanger, a second fresh water line for directing seawater from the heat exchanger to the outside of the hull, A second fresh water line for delivering fresh water to the heat exchanger from the main engine and the air cooler, a bypass line branching from the second fresh water line to join the first fresh water line to bypass the heat exchanger, The ratio of the flow rate of fresh water passing through the heat exchanger and the flow rate of clear water flowing through the bypass line A temperature sensor for detecting the temperature of fresh water flowing in the first fresh water line on the downstream side of the junction point of the bypass line; The control unit controls the rotation speed of the seawater pump through the inverter so that the temperature detected by the temperature sensor after the fresh water cooling is maintained at the set temperature while controlling the temperature control valve, And a control device for controlling the temperature control valve such that the temperature detected by the temperature sensor after the fresh water cooling is maintained at a lower limit temperature lower than the set temperature when the temperature detected by the post-temperature sensor is lower than the set temperature .

According to the above configuration, the temperature constant control is performed so that the temperature of the fresh water supplied to the main engine and the air cooler is maintained at the set temperature at normal times. On the other hand, when the seawater pump has the minimum number of revolutions, when the temperature of fresh water supplied to the main engine and the air cooler does not flow to the bypass line, it is left to flow between the set temperature and the lower limit temperature, The lower limit temperature is maintained. That is, when the seawater pump has the minimum rotation speed, the temperature of fresh water supplied to the air cooler can be suppressed to be lower than the set temperature. According to this, the temperature of the air supplied to the main engine is lowered, and the fuel consumption of the main engine can be improved.

According to another aspect of the present invention, there is provided a ship cooling system comprising: a heat exchanger for performing heat exchange between fresh water and seawater to cool the fresh water; and a control unit for guiding the seawater from the outside of the ship to the heat exchanger, A second seawater line for delivering seawater to the outside of the hull from the heat exchanger, and a second seawater line for passing seawater from the heat exchanger to the main engine, which is a reciprocating engine of the ship, A first fresh water line for guiding fresh water to an air cooler for cooling air supplied to the main engine from the supercharger, a second fresh water line for directing fresh water from the main engine and the air cooler to the heat exchanger, A bypass line branching from the second clear water line to join the first clear water line to the first clear water line, A temperature regulating valve for changing a ratio of a flow rate of fresh water passing through the bypass line to a flow rate of fresh water flowing through the bypass line, A cold water cooling pre-temperature sensor for detecting the temperature of fresh water flowing in the second fresh water line; a seawater inflow temperature sensor for detecting the temperature of the seawater flowing in the first sea water line; Speed operation in which fresh water can be cooled to a set temperature or lower in the heat exchanger when the seawater pump is set to the first rotation speed based on the temperature detected by the sensor, the fresh water cooling pre-temperature sensor and the seawater inflow temperature sensor And when the low speed operation condition is not satisfied, it is determined that the sea water pump When the seawater pump is switched to the first rotation speed, the temperature control valve is controlled so that clear water does not flow to the bypass line when the rotation speed is switched to the second rotation speed, And a control device for controlling the temperature control valve such that the temperature detected by the post-temperature sensor is maintained at a lower limit temperature lower than the set temperature.

In general, the heat exchanger is configured to cool the fresh water to a set temperature or lower when the seawater pump is rotated for the second time. Therefore, according to the above configuration, the temperature of fresh water supplied to the main engine and the air cooler can be changed between the set temperature and the lower limit temperature. That is, when the temperature of the fresh water supplied to the air cooler is lower than the set temperature, the temperature of the air supplied to the main engine is lowered. Accordingly, the fuel consumption of the main engine can be improved. Furthermore, since the inverter does not need to be used in the above configuration, the cost can be reduced.

For example, the seawater pump may be manually switched to one of the first rotation speed and the second rotation speed, and the control device may indicate through the indicator whether the low speed operation condition is satisfied .

Alternatively, the seawater pump may be configured to be switched to one of the first rotation speed and the second rotation speed by an electrical signal, and when the control device does not satisfy the low speed operation condition, And when the low speed operation condition is satisfied, the seawater pump may be switched to the first rotation speed.

Wherein the controller calculates a heat exchange capacity coefficient of the heat exchanger based on the temperature detected by the temperature sensor after the fresh water cooling, the fresh water cooling preheat temperature sensor and the seawater inflow temperature sensor when the seawater pump is at the second rotation speed And it may be determined whether or not the low-speed operation condition is satisfied by using the calculated heat exchange capacity coefficient. According to such a configuration, it is possible to determine whether or not the low-speed operation condition is satisfied in consideration of aging due to contamination or the like of the heat exchanger.

The first fresh water line directs clean water from the heat exchanger to the main engine and the air cooler as well as to the EGR cooler and the second fresh water line passes the main engine and the air cooler as well as the EGR cooler to the heat exchanger It is also permissible to direct the fresh water. Especially, for ships with EGR, EGR is only used in specific sea areas. In other words, since the cooling capacity of the cooling system is sufficient in the normal operation in which the EGR is not used, the effect of improving the fuel efficiency of the main engine can be obtained more remarkably.

The first fresh water line not only delivers the fresh water to the main engine and the air cooler in the heat exchanger but also to a special cooling device that needs to be cooled at a predetermined temperature, and the second fresh water line not only passes through the main engine and the air cooler, Further comprising a reflux line which branches off from the second fresh water line and joins the first fresh water line so as to form a circulation circuit of the special cooling device, the fresh water leading from the special cooling device to the heat exchanger, It is also good. According to this configuration, fresh water supplied to the special cooling device can be maintained at a constant temperature.

According to the present invention, the fuel consumption of the main engine of the ship can be further improved.

1 is a schematic configuration diagram of a ship cooling system according to a first embodiment of the present invention.
2 is a system diagram relating to supply and exhaust of the main engine.
3 is a schematic configuration diagram of a ship cooling system according to a second embodiment of the present invention.
4 is a schematic configuration diagram of a conventional ship cooling system.

(Embodiment 1)

Fig. 1 shows a ship cooling system 1A according to a first embodiment of the present invention. This cooling system 1A is for cooling the ship's main engine 11 and other equipment using clear water and seawater.

The main engine 11 may directly drive a propeller (not shown) (machine propulsion), and may drive the propeller through a generator and a motor (electric propulsion). The main engine 11 is a reciprocating engine and has a plurality of combustion chambers formed by cylinders and pistons.

2, the main engine 11 is connected to the compressor 92 of the turbocharger 91 by an air supply line 94 and is connected to the turbine 93 of the turbocharger 91 by an exhaust line 95 ). The air supply line 94 is provided with an air cooler 12. The air cooler 12 cools the air supplied to the main engine 11 from the compressor 92 of the supercharger 91.

The exhaust gas recirculation line 96 branches from the exhaust line 95 and the EGR line 96 joins the air supply line 94 on the downstream side of the air cooler 12 . The EGR line 96 is provided with an EGR cooler 13 and a blower 97 in this order from the upstream side.

As shown in Fig. 1, the cooling system 1A includes a heat exchanger 21 for performing heat exchange between fresh water and seawater to cool fresh water. The cooling system 1A also includes a first seawater line 31 for delivering seawater to the heat exchanger 21 from outside the hull and a second seawater line 32 for delivering seawater from the heat exchanger 21 to the outside of the ship, . A seawater pump 33 is installed in the first sea water line 31.

Further, the cooling system 1A includes a first fresh water line 4 for delivering fresh water from the heat exchanger 21 to the main engine 11, the air cooler 12 and the EGR cooler 13, , An air cooler (12) and a second fresh water line (5) for delivering fresh water from the EGR cooler (13) to the heat exchanger (21). The first fresh water line 4 leads the fresh water to the special cooling device 14 requiring cooling at a constant temperature from the heat exchanger 21 and the second fresh water line 5 is connected to the special cooling device 14, To the heat exchanger (21). The special cooling device 14 is, for example, a power generation engine or the like.

More specifically, the first fresh water line 4 includes one main flow path 41 extending from the heat exchanger 21, a main flow path 41, the aforementioned cooling target device (main engine 11, (EGR cooler 13 and special cooling device 14), which are connected to each other. Likewise, the second fresh water line 5 includes one main flow path 51 extending from the heat exchanger 21 and a plurality of branch flow paths 52 connecting the main flow path 51 and the device to be cooled .

A bypass line 22 is connected to the first fresh water line 4 and the second fresh water line 5 to bypass the heat exchanger 21. The bypass line 22 branches from the main flow channel 51 of the second fresh water line 5 and joins the main flow channel 41 of the first fresh water line 4. A fresh water pump 23 is provided in the main flow path 51 of the second fresh water line 5 at a position upstream of the branch point of the bypass line 22.

The ratio of the flow rate of clear water passing through the heat exchanger 21 and the flow rate of fresh water flowing through the bypass line 22 is changed by the temperature control valve 24. [ In the present embodiment, the temperature regulating valve 24 is a three-way valve (mixing valve) provided at the junction point of the bypass line 22 in the main flow path 41 of the first fresh water line 4. However, the temperature regulating valve 24 may be a three-way valve (distribution valve) provided at a branch point of the bypass line 22 in the main flow path 51 of the second fresh water line 5. [ Alternatively, the temperature regulating valve 24 may be disposed upstream of the junction point of the bypass line 22 in the main flow path 41, or in a portion upstream of the branch point of the bypass line 22 in the main flow path 51, A flow rate control valve, and a second flow rate control valve provided in the bypass line 22. [

The circulation line 61 is connected to the branch flow paths 42 and 52 for the main engine 11 in the first fresh water line 4 and the second fresh water line 5. The circulation line 61 branches from the branch flow channel 52 of the second fresh water line 5 to join the branch flow channel 42 of the first fresh water line 4 so as to form a circulation circuit for the main engine 11 . The circulation line 61 is provided with a pump 62 for circulating fresh water to the circulation circuit for the main engine 11. However, the pump 62 may be provided upstream of the branch point of the circulation line 61 in the branched flow path 52, or at a downstream side of the junction point of the circulation line 61 in the branched flow path 42.

The circulation circuit for the main engine 11 is provided with a temperature control valve 63 for keeping the temperature of fresh water supplied to the main engine 11 constant. In the present embodiment, the temperature regulating valve 63 is a three-way valve (mixing valve) installed at the confluence point of the circulation line 61 in the branched flow path 42, Way valve (distributing valve) provided at the branch point of the second valve 61.

Likewise, in the first fresh water line 4 and the second fresh water line 5, the circulation line 64 is connected to the branched flow paths 42 and 52 for the special cooling device 14. The circulation line 64 branches off from the branch flow channel 52 of the second fresh water line 5 and flows into the branch flow channel 42 of the first fresh water line 4 so as to form a circulation circuit for the special cooling device 14 I am joining. The circulation line 64 is provided with a pump 65 for circulating fresh water to the circulation circuit for the special cooling device 14. [ However, the pump 65 may be provided upstream of the bifurcation point of the circulation line 64 in the branch passage 52 or downstream of the junction point of the circulation line 64 in the branch passage 42.

The circulation circuit for the special cooling device 14 is provided with a temperature control valve 66 for keeping the temperature of fresh water supplied to the special cooling device 14 constant. In the present embodiment, the temperature control valve 66 is a three-way valve (mixing valve) installed at the junction point of the circulation line 64 in the branch passage 42, Way valve (distributing valve) provided at the branch point of the valve 64 may be used.

The above-mentioned temperature control valves 24, 63, 66 are controlled by the control device 7. The control device 7 also controls the number of revolutions of the above-described seawater pump 33 via the inverter 8. Here, in FIG. 1, only a part of signal lines are depicted in order to simplify the drawing. On the other hand, the number of revolutions of the fresh water pump 23 is constant. For example, the control device 7 is a computer having a CPU and a memory such as ROM or RAM. The control device 7 may be a single device or may be divided into a plurality of devices for controlling the seawater pump 33 and a plurality of devices for controlling the temperature control valves 24, 63 and 66. Hereinafter, the control of the temperature control valve 24 will be described in detail.

A fresh water cooling post-temperature sensor 71 for detecting the fresh water temperature flowing in the first fresh water line 4 on the downstream side of the junction point of the bypass line 22 is installed in the main flow path 41 of the first fresh water line 4 . When the control device 7 is divided into a plurality of devices for controlling the seawater pump 33 and control devices for the temperature control valves 24, 63 and 66, the temperature sensor 71 for the fresh water- A temperature sensor, and a temperature sensor for controlling the temperature control valve (24) may be used.

The control device 7 controls the temperature regulating valve 24 so that clear water does not flow to the bypass line 22 normally so that the temperature detected by the temperature sensor 71 after fresh water cooling is maintained at the set temperature Td And controls the number of rotations of the seawater pump 33 through the inverter 8. That is, the rotation number of the seawater pump 33 is usually adjusted between the maximum rotation number N1 and the minimum rotation number N2 so that the temperature of the clear water flowing out from the heat exchanger 21 is constant. For example, the set temperature Td is 36 DEG C, and the maximum number of revolutions N1 and the minimum number of revolutions N2 are 1200 rpm and 600 rpm, respectively.

For example, when the load of the main engine 11 is high, the temperature of the fresh water flowing out of the main engine 11 becomes high, so that the rotation speed of the seawater pump 33 becomes large. The rotation speed of the seawater pump 33 is reduced because the temperature of fresh water flowing out from the main engine 11 is low.

On the other hand, when the number of rotations of the seawater pump 33 becomes the minimum number of revolutions N2 and the temperature detected by the temperature sensor 71 after the fresh water cooling becomes lower than the set temperature Td, And switches from constant control to temperature variable control. The temperature constant control is a control in which the temperature of fresh water supplied to the cooling target devices (the main engine 11, the air cooler 12, the EGR cooler 13 and the special cooling device 14) is maintained at the set temperature Td , The variable temperature control is a control in which the temperature of the fresh water supplied to the device to be cooled is suppressed to be lower than the set temperature Td.

Specifically, in the temperature variable control, the control device 7 controls the temperature regulating valve 24 so that the temperature detected by the temperature sensor 71 after fresh water cooling is maintained at the lower limit temperature Tl, which is lower than the set temperature Td do. For example, the lower limit temperature (Tl) is 10 占 폚. In the Arctic Circle, the temperature of the seawater may fall below 10 ° C.

When the temperature detected by the temperature sensor 71 after the fresh water cooling is higher than the lower limit temperature Tl, the detected temperature becomes higher when fresh water flows through the bypass line 22. Therefore, when the temperature detected by the temperature sensor 71 after the fresh water cooling is between the lower limit temperature Tl and the set temperature Td, the control device 7 controls the temperature of the bypass line 22 so that clear water does not flow And controls the regulating valve 24. That is, in this case, the temperature of the fresh water supplied to the cooling object device is left to the flow (to be precise, the main engine 11 and the special cooling device 14 are supplied with the temperature control valves 63 and 66) Fresh water is supplied). On the other hand, when the temperature detected by the temperature sensor 71 after the fresh water cooling is lower than the lower limit temperature Tl, the control device 7 determines that the fresh water flows into the bypass line 22, The temperature control valve 24 is controlled so that the detected temperature rises to the lower limit temperature Tl.

As described above, in the cooling system 1A according to the present embodiment, the temperature constant control is usually performed. On the other hand, when the seawater pump 33 reaches the minimum rotation speed N2, when the temperature of the fresh water supplied to the cooling target device does not flow to the bypass line 22, the set temperature Td and the lower limit temperature Tl , And is maintained at the lower limit temperature Tl when fresh water flows in the bypass line 22. That is, when the seawater pump 33 has the minimum number of revolutions N2, the temperature of fresh water supplied to the air cooler 12 can be suppressed to be lower than the set temperature Td. Accordingly, the temperature of the air supplied to the main engine 11 is lowered, and the fuel consumption of the main engine 11 can be improved.

In particular, in a ship adopting EGR as in the present embodiment, EGR is not used outside a specific sea area. That is, since the cooling capacity of the cooling system 1A is sufficient for normal operation in which the EGR is not used, the effect of improving the fuel economy of the main engine 11 can be obtained more remarkably.

Further, in this embodiment, since the circulation circuit of the special cooling device 14 is formed, the fresh water supplied to the special cooling device 14 can be maintained at a constant temperature.

(Second Embodiment)

FIG. 3 shows a ship cooling system 1B according to a second embodiment of the present invention. This cooling system 1B differs from the cooling system 1A of the first embodiment in that the seawater pump 33 is rotated at a second rotation speed Nb that is larger than the first rotation speed Na and the first rotation speed Na, It is possible to switch to one of them. For example, the first rotation speed Na is 600 rpm and the second rotation speed Nb is 1200 rpm.

In this embodiment, the seawater pump 33 is configured to be manually switched to one of the first rotation speed Na and the second rotation speed Nb. Then, the control device 7 is connected to the display device 9.

Further, in this embodiment, the fresh water cooling pre-temperature sensor 72 is provided in the main flow channel 51 of the second fresh water line 5, and the seawater inflow temperature sensor 73 is provided in the first sea water line 31 Is installed. The fresh water cooling preheat temperature sensor 72 detects the temperature of clear water flowing in the main channel 51 of the second fresh water line 5 and the sea water inflow temperature sensor 73 detects the temperature of fresh water flowing in the first sea water line 31 The temperature is detected.

The control device 7 determines whether or not the low speed operation condition is satisfied based on the temperatures detected by the temperature sensor 71, the fresh water cooling pre-temperature sensor 72 and the seawater inflow temperature sensor 73 after the fresh water cooling. The low speed operation condition is a condition that the fresh water can be cooled to the set temperature Td or lower in the heat exchanger 21 when the sea water pump 33 is set to the first rotation speed Na. The control device 7 displays on the indicator 9 whether or not the low-speed operation condition is satisfied.

The display device 9 may be a display having a screen, or may be a lamp. The control device 7 displays whether the first rotation number Na and the second rotation number Nb are to be selected as to whether or not the low speed operation condition is satisfied when the display device 9 is displayed It is also good. The shipbuilder looks at the display of the indicator 9 and switches the seawater pump 33 to the first rotation speed Na or the second rotation speed Nb.

The control device 7 controls the temperature regulating valve 24 so that clear water does not flow to the bypass line 22 when the seawater pump 33 is switched to the second rotation speed Nb when the low speed operation condition is not satisfied, . On the other hand, when the low-speed operation condition is satisfied, the controller 7 determines whether the temperature detected by the temperature sensor 71 after the fresh water cooling has reached the set temperature (for example, when the seawater pump 33 is switched to the first rotation speed Na) Temperature control valve 24 so as to maintain the lower limit temperature Tl lower than the lower limit temperature Td.

When the low speed operation condition is satisfied, as in the first embodiment, when the temperature detected by the temperature sensor 71 after the fresh water cooling is higher than the lower limit temperature Tl, if fresh water flows through the bypass line 22, Higher. Therefore, when the temperature detected by the temperature sensor 71 after the fresh water cooling is between the lower limit temperature Tl and the set temperature Td, the control device 7 controls the temperature of the bypass line 22 Thereby controlling the valve 24. That is, in this case, the temperature of fresh water supplied to the cooling object devices (the main engine 11, the air cooler 12, the EGR cooler 13, and the special cooling device 14) The coolant 11 and the special cooling device 14 are supplied with fresh water of a constant temperature by the action of the temperature control valves 63 and 66). On the other hand, when the temperature detected by the temperature sensor 71 after the fresh water cooling is lower than the lower limit temperature Tl, the control device 7 determines that the fresh water flows into the bypass line 22, The temperature control valve 24 is controlled so that the detected temperature rises to the lower limit temperature Tl.

Further, in the present embodiment, the control device 7 controls the temperature sensor 71, the fresh water cooling pre-temperature sensor 72 and the seawater inflow temperature sensor 72 when the seawater pump 33 is at the second rotation speed Nb, (Kb) of the heat exchanger (21) in accordance with the temperature detected by the temperature sensor (73), and judges whether or not the low-speed operation condition is satisfied by using the calculated heat-exchange capacity coefficient (Kb). The heat exchange capacity coefficient Kb is the sum of the heat exchange area S, the heat transfer coefficient k and the contamination coefficient λ (Kb = S × k × λ).

On the other hand, when the seawater pump 33 is at the first rotation speed Na, when the temperature detected by the temperature sensor 71 after the fresh water cooling becomes equal to or higher than the set temperature Tb, the low speed operation condition can not be satisfied .

Specifically, the control device 7 first calculates the heat exchange amount Q from the following equation (1).

Q = (Tf1 - Tf2) x cf x df x Ff (1)

Tf1: the temperature detected by the fresh water cooling pre-temperature sensor 72

Tf2: temperature detected by the temperature sensor 71 after fresh water cooling

cf: Specific heat of fresh water

df: Specific gravity of clean water

Ff: Flow rate of clean water (converted from rotation speed of fresh water pump 23)

Next, the controller 7 calculates the seawater outlet temperature Ts2b from the following equation (2).

Ts2b = Ts1 + Q / (cs 占 ds 占 Fsb)

Ts1: the temperature detected by the seawater inflow temperature sensor 73

cs: Specific heat of seawater

ds: Seawater specific gravity

Fsb: Flow rate of seawater at the second rotation speed (Nb)

Next, the control device 7 calculates the logarithmic mean temperature difference LMTDb at the second rotation speed Nb from the following equation (3).

LMTDb = (TD1b-TD2b) / ln (TD1b / TD2b)

TD1b: Fresh water inlet side temperature (Tf1 - Ts2b)

TD2b: Fresh water outlet side temperature (Tf2 - Ts1)

Finally, the controller 7 calculates the heat exchange capacity coefficient Kb from the following equation (4).

Kb = Q / LMTDb (4)

Next, the control device 7 calculates a virtual heat exchange capacity coefficient Ka in which the fresh water outflow temperature becomes the set temperature Td when the seawater pump 33 is set to the first rotation speed Na.

First, the controller 7 calculates the fresh water cooling pre-temperature Tf1a from the following equation (5).

Tf1a = Td + Q / (cf x df x Ff)

Next, the control device 7 calculates the seawater outlet temperature Ts2a from the following expression (6).

Ts2a = Ts1 + Q / (cs x ds x Fsa) (6)

Fsa: Flow rate of seawater at the first revolution (Na)

Next, the control device 7 calculates the logarithmic mean temperature difference LMTDa at the first rotation speed Na in the following equation (7).

LMTDa = (TD1a-TD2a) / ln (TD1a / TD2a) (7)

TD1a: fresh water inlet side temperature (Tf1a-Ts2a)

TD2a: fresh water outlet side temperature (Td - Ts1)

Finally, the control device 7 calculates the heat exchange capacity coefficient Ka from the following equation (8).

Ka = Q / LMTDa (8)

After calculating both the heat exchange capacity coefficient Kb at the second rotation speed Nb and the virtual heat exchange capacity coefficient Ka at the first rotation speed Na, the control device 7 compares them , Kb > Ka, it is determined that the low-speed operation condition is satisfied. If Kb < Ka, it is determined that the low-speed operation condition is not satisfied.

Generally, the heat exchanger 21 is configured to cool the seawater pump 33 to the fresh water set point Td or lower when the seawater pump 33 becomes the second rotation speed Nb. Therefore, according to the control as in the present embodiment, the temperature of fresh water supplied to the cooling object device can be changed between the set temperature Td and the lower limit temperature Tl. That is, when the temperature of fresh water supplied to the air cooler 12 is lower than the set temperature Td, the temperature of the air supplied to the main engine 11 is lowered. Accordingly, the fuel consumption of the main engine 11 can be improved. In addition, since it is not necessary to use the inverter 8 (see Fig. 1) in the above configuration, the cost can be reduced.

<Modifications>

In determining whether or not the low-speed operation condition is satisfied, instead of using the calculated heat-exchange capacity coefficient Kb, the heat-exchange capacity coefficient K at the time of designing is stored in advance in the control device 7 and the design heat- K) may be used to determine whether or not the low-speed operation condition is satisfied. However, when the heat exchange capacity coefficient Kb of the heat exchanger 21 is calculated as in the above embodiment, it is possible to determine whether or not the low-speed operation condition is satisfied in consideration of the aging due to contamination or the like of the heat exchanger 21. [

When the change of the heat exchange capacity when the flow rate of the seawater is changed is known as the characteristic of the heat exchanger 21, this effect may be added to determine whether or not the low-speed operation condition is satisfied. For example, if the heat exchange capacity is reduced by 20% when the flow rate of seawater is reduced, the low-speed operation condition may be determined as Kb x 0.8 > Ka.

The seawater pump 33 may be configured to be switched to one of the first rotation speed Na and the second rotation speed Nb by an electric signal. In this case, when the low-speed operation condition is not satisfied, the controller 7 switches the seawater pump 33 to the second rotation speed Nb, and when the low-speed operation condition is satisfied, To the first rotation number (Na).

Also, a seawater outlet temperature sensor may be provided in the second seawater line 32, and the temperature directly detected by the temperature sensor may be used as the seawater outlet temperature Ts2b.

(Other Embodiments)

The present invention is not limited to the above-described first and second embodiments, and various modifications are possible without departing from the gist of the present invention.

For example, the EGR line 96 and the EGR cooler 13 may not be installed in Fig. The first fresh water line 4 is connected to the main engine 11 and the air cooler 12 from the heat exchanger 21 without employing the special cooling device 14 as well as the EGR cooler 13 in Figs. It is also good to induce fresh water only.

1A, 1B: Cooling system of ship 11: Main engine
12: Air cooler 13: EGR cooler
14: Special cooling device 21: Heat exchanger
22: bypass line 24: temperature control valve
31: first sea water line 32: second sea water line
33: Seawater pump 4: 1st fresh water line
5: second fresh water line 64: circulation line
7: Control device 71: Temperature sensor after fresh water cooling
72: fresh water cooling temperature sensor 73: seawater inflow temperature sensor
8: Inverter 9: Indicator

Claims (7)

A heat exchanger for performing heat exchange between fresh water and seawater to cool the fresh water,
A first seawater line which directs seawater from the outside of the hull to the heat exchanger and has a seawater pump,
A second seawater line for delivering seawater from the heat exchanger to the outside of the hull,
A first fresh water line for guiding clean water from the heat exchanger to an air cooler for cooling the air supplied to the main engine from the main engine and the turbocharger of the ship,
A second fresh water line for directing fresh water from the main engine and the air cooler to the heat exchanger,
A bypass line branching from said second clear water line and joining said first clear water line to bypass said heat exchanger,
A temperature regulating valve for changing a ratio of a flow rate of fresh water passing through the heat exchanger and a flow rate of fresh water flowing through the bypass line,
A fresh water cooling post-temperature sensor for detecting the temperature of fresh water flowing in the first fresh water line on the downstream side of the confluence point of the bypass line,
Controlling the rotation speed of the seawater pump through the inverter so that the temperature detected by the temperature sensor after the fresh water cooling is maintained at the set temperature while controlling the temperature control valve so that clear water does not flow to the bypass line at normal times, When the number of revolutions of the pump is the minimum number of revolutions and the temperature detected by the temperature sensor after the fresh water cooling becomes lower than the set temperature, the temperature detected by the temperature sensor after the fresh water cooling is maintained at the lower limit temperature, And a control device for controlling the temperature control valve.
A heat exchanger for performing heat exchange between fresh water and seawater to cool the fresh water,
A first seawater line for delivering seawater to the heat exchanger from the outside of the hull and provided with a seawater pump capable of switching to a first rotation number and a second rotation number larger than the first rotation number;
A second seawater line for delivering seawater from the heat exchanger to the outside of the hull,
A first fresh water line for guiding clean water from the heat exchanger to an air cooler for cooling the air supplied to the main engine from the main engine and the turbocharger of the ship,
A second fresh water line for directing fresh water from the main engine and the air cooler to the heat exchanger,
A bypass line branching from said second clear water line and joining said first clear water line to bypass said heat exchanger,
A temperature regulating valve for changing a ratio of a flow rate of fresh water passing through the heat exchanger and a flow rate of fresh water flowing through the bypass line,
A fresh water cooling post-temperature sensor for detecting the temperature of fresh water flowing in the first fresh water line on the downstream side of the confluence point of the bypass line,
A fresh water cooling pre-temperature sensor for detecting the temperature of fresh water flowing in the second fresh water line,
A seawater inflow temperature sensor for detecting the temperature of the seawater flowing in the first seawater line,
Cooling the fresh water to a set temperature or lower in the heat exchanger when the seawater pump is at the first rotation speed based on the temperature detected by the temperature sensor after the fresh water cooling, the fresh water cooling pre-temperature sensor and the seawater inflow temperature sensor And when it is determined that the low speed operation condition is not satisfied, it is determined that the fresh water does not flow to the bypass line when the seawater pump is switched to the second rotation speed, And controls the valve so that the temperature detected by the temperature sensor after the fresh water cooling is maintained at the lower limit temperature lower than the set temperature when the seawater pump is switched to the first rotation speed when the low speed operation condition is satisfied, And a control device for controlling the control valve.
3. The method of claim 2,
Wherein the seawater pump is configured to be manually switched to one of the first rotation number and the second rotation number,
Wherein the control device displays, through an indicator, whether or not the low-speed operation condition is satisfied.
3. The method of claim 2,
Wherein the seawater pump is configured to be switched to one of the first rotation speed and the second rotation speed by an electric signal,
The control device switches the seawater pump to the second rotation speed when the low speed operation condition is not satisfied and switches the seawater pump to the first rotation speed when the low speed operation condition is satisfied Of the ship.
5. The method according to any one of claims 2 to 4,
Wherein the controller calculates a heat exchange capacity coefficient of the heat exchanger based on the temperature detected by the temperature sensor after the fresh water cooling, the fresh water cooling preheat temperature sensor and the seawater inflow temperature sensor when the seawater pump is at the second rotation speed And determines whether or not the low-speed operation condition is satisfied by using the heat exchange capacity coefficient thus calculated.
6. The method according to any one of claims 1 to 5,
The first fresh water line directs fresh water from the heat exchanger to the main engine and the air cooler as well as to the EGR cooler
Wherein the second fresh water line directs fresh water from the main engine and the air cooler as well as the EGR cooler to the heat exchanger.
The method according to any one of claims 1 to 6,
The first fresh water line guides the fresh water from the heat exchanger to the main engine and the air cooler as well as to a special cooling device requiring cooling at a predetermined temperature,
The second fresh water line directs fresh water from the main engine and the air cooler as well as from the special cooling device to the heat exchanger,
Further comprising a return line branching from said second clear water line and joining said first clear water line to form a circulation circuit of said special cooling device.

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