Method for determining the self-cooling range of a seawater central heat exchanger and a ship

Abstract

This invention discloses a method for determining the self-flowing cooling range of a centralized seawater heat exchanger and a corresponding vessel. It is applied to a system for determining the self-flowing cooling range of a centralized seawater heat exchanger. The system includes a controller, a power switch, a first temperature sensor, a second temperature sensor, and a seawater pump, a centralized seawater heat exchanger, and a freshwater circuit connected in sequence. The method includes: obtaining the freshwater outlet temperature limit of the centralized seawater heat exchanger; obtaining the initial value of the upper limit of the self-flowing cooling seawater temperature of the centralized seawater heat exchanger; obtaining the seawater temperature and the freshwater outlet temperature of the centralized seawater heat exchanger; and determining whether to start or stop the seawater pump. The technical solution of this invention, by measuring the seawater inlet temperature and the freshwater outlet temperature, can continuously correct the seawater temperature limit of the self-flowing cooling of the centralized seawater heat exchanger, thereby enabling timely switching between starting and stopping the seawater pump, ensuring the efficient operation of the seawater cooling system, and providing significant economic benefits to vessel operation.

Description

Technical Field

[0001] This invention relates to the field of ship digital control technology, and in particular to a method for determining the self-flow cooling range of a seawater centralized heat exchanger and a ship thereof. Background Technology

[0002] Shipboard machinery, electrical, electronic, and refrigeration equipment continuously generate heat during operation, which needs to be dissipated through the ship's sea-through cooling system to ensure normal and reliable operation within a certain temperature range. Mechanical equipment mainly includes diesel engine cylinders, pistons, and bearings; electrical equipment mainly includes propulsion motors, electric pumps, and frequency converters; electronic equipment mainly includes chips and circuit boards; and refrigeration equipment mainly includes air conditioners. Furthermore, the lubricating oil required for bearing lubrication also needs to be cooled through the sea-through cooling system. To reduce seawater corrosion and fouling of shipboard equipment and pipelines, modern ships have gradually adopted staged cooling technology, known as a central cooling system. This system features an intermediate freshwater loop to cool equipment inside the cabins with freshwater, which is then cooled by a centralized seawater heat exchanger. With centralized cooling, ships only need two parallel centralized seawater heat exchangers and corresponding sea-through pipelines, thus significantly shortening the length of the pipelines, improving safety and reliability, and reducing maintenance and support burdens.

[0003] The energy consumption of a ship's sea-through cooling system can account for 10% of the total energy consumption of the ship's auxiliary machinery systems. Therefore, optimizing its design and operation mode is of great significance for energy conservation and emission reduction in ships. Currently, the main energy-saving measure is to balance the cooling water volume with the freshwater cooling demand through variable frequency speed control of seawater pumps. It is now necessary to determine the gravity cooling range of the centralized seawater heat exchanger in order to achieve refined ship control and support the energy-saving operation of the sea-through cooling system.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the self-flow cooling range of a centralized seawater heat exchanger and a corresponding vessel. By measuring the seawater inlet temperature and freshwater outlet temperature, the seawater temperature limit for self-flow cooling of the centralized seawater heat exchanger can be continuously corrected, thereby enabling the timely switching of the seawater pump for starting and stopping, ensuring the efficient operation of the seawater cooling system, and providing good economic value for the operation of the vessel.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for determining the self-flowing cooling range of a centralized seawater heat exchanger, applied to a system for determining the self-flowing cooling range of a centralized seawater heat exchanger. The system includes a controller, a power switch, a first temperature sensor, a second temperature sensor, and a seawater pump, a centralized seawater heat exchanger, and a freshwater circuit connected in sequence. The method comprises: step S100, obtaining the freshwater outlet temperature limit of the centralized seawater heat exchanger; step S200, obtaining the initial value of the upper limit of the self-flowing cooling seawater temperature of the centralized seawater heat exchanger; step S300, obtaining the seawater temperature and the freshwater outlet temperature of the centralized seawater heat exchanger; step S400, determining whether to start or stop the seawater pump; step S500, when the seawater pump is stopped, correcting the upper limit of the self-flowing cooling seawater temperature using the seawater temperature and the freshwater outlet temperature; and step S600, returning to step S300.

[0007] In one embodiment of the present invention, step S100 includes: step S101, setting the freshwater outlet temperature limit of the seawater centralized heat exchanger; step S102, the controller acquiring the freshwater outlet temperature limit of the seawater centralized heat exchanger.

[0008] In one embodiment of the present invention, step S200 includes: step S201, obtaining the cold-side gravity flow rate, hot-side freshwater flow rate, freshwater circuit heat load, and heat exchange area of ​​the seawater centralized heat exchanger at a preset speed; step S202, generating the initial value of the upper limit of the gravity-cooled seawater temperature using a heat balance formula; and step S203, the controller obtaining the initial value of the upper limit of the gravity-cooled seawater temperature.

[0009] In one embodiment of the present invention, step S300 includes: step S301, the first temperature sensor measures the seawater temperature; step S302, the second temperature sensor measures the freshwater outlet temperature of the seawater centralized heat exchanger; and step S303, the controller acquires the seawater temperature and the freshwater outlet temperature.

[0010] In one embodiment of the present invention, step S400 includes: step S401, setting a first condition and a second condition; step S402, when the first condition is met, the controller controls the seawater pump to stop running; step S403, when the second condition is met, the controller controls the seawater pump to start.

[0011] In one embodiment of the present invention, the first condition is: t1≤t a -Δt; where t1 is the seawater temperature, t a The upper limit of the temperature of the self-flowing cooled seawater is given, and Δt is the given temperature interval.

[0012] In one embodiment of the present invention, the second condition is: t1≥t a Where t1 is the seawater temperature, t a This represents the upper limit of the temperature of the self-flowing cooled seawater.

[0013] In one embodiment of the present invention, step S500 includes: step S501, when the seawater pump stops running, t1 and t2 are used to control t. a Perform correction; Step S502, if t2 > t0, take t a =t1-xΔt; Step S503, if t2<t0, calculate t a *=t1+x(t0–t2), take t a =max(t) a ,t a *); where t0 is the freshwater outlet temperature limit, t1 is the seawater temperature, t2 is the freshwater outlet temperature, x is a coefficient less than 1, Δt is the given temperature interval, and t a *For use in updating t a The intermediate quantity.

[0014] Secondly, the present invention provides a ship, including a system for determining the self-flowing cooling range of a centralized seawater heat exchanger, wherein the system employs the method for determining the self-flowing cooling range of a centralized seawater heat exchanger as described above.

[0015] Compared with the prior art, the method for determining the self-flow cooling range of the seawater centralized heat exchanger according to the present invention and the ship can continuously correct the seawater temperature limit of the self-flow cooling of the seawater centralized heat exchanger by measuring the seawater inlet temperature and the freshwater outlet temperature, thereby realizing the timely switching of the seawater pump to start and stop, ensuring the efficient operation of the seawater cooling system, and having good economic value for ship operation. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a method for determining the self-flowing cooling range of a centralized seawater heat exchanger according to Embodiment 1 of the present invention.

[0017] Figure 2 This is a schematic diagram of the logic flow of a method for determining the self-flowing cooling range of a centralized seawater heat exchanger according to Embodiment 1 of the present invention;

[0018] Figure 3 This is a schematic diagram of a system for determining the self-flow cooling range of a centralized seawater heat exchanger according to Embodiment 1 of the present invention.

[0019] Explanation of key figure labels:

[0020] 1-Seawater pump, 2-Seawater central heat exchanger, 3-Seawater temperature sensor, 4-Freshwater temperature sensor, 5-Controller, 6-Power switch. Detailed Implementation

[0021] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0022] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0023] To facilitate understanding, the main implementation concepts of the various embodiments of the present invention will be briefly described first.

[0024] The energy consumption of a ship's offshore cooling system can account for up to 10% of the total energy consumption of the ship's auxiliary machinery systems. Therefore, optimizing its design and operation mode is of great significance for energy conservation and emission reduction in ships. Currently, the main energy-saving measure is to balance the cooling water volume with the freshwater cooling demand through variable frequency speed regulation of seawater pumps. The master's thesis, "Research on Energy Conservation of Ship Central Cooling System," also proposes to use synchronous variable frequency operation of freshwater pumps and seawater pumps to further reduce energy consumption. In addition, utilizing the ship's navigation head pressure to generate gravity flow head is a promising energy-saving method. It can reduce the head requirement of seawater pumps, save pump power or even completely shut down the system at the same flow rate. The shutdown conditions depend on the ship's operating conditions and seawater temperature. It is necessary to determine the gravity flow cooling range of the centralized seawater heat exchanger to achieve refined ship control and support the energy-saving operation of the offshore cooling system.

[0025] By discovering the technical defects described in the background art, the inventors hoped to find a way to enable the timely switching of seawater pumps to start and stop, ensuring the efficient operation of the sea cooling system and providing good economic value for ship operation.

[0026] To address the technical problems in existing technologies, such as excessive energy consumption of seawater pumps, inability to start or stop them according to actual needs, lack of determination of the self-flow cooling range of centralized seawater heat exchangers, and inability to achieve precise ship control, the inventors of this invention, through creative work, have obtained a method for determining the self-flow cooling range of centralized seawater heat exchangers and a ship based on this invention.

[0027] Example 1

[0028] Figure 1 This is a flowchart illustrating a method for determining the self-flowing cooling range of a centralized seawater heat exchanger according to Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the logic flow of a method for determining the self-flowing cooling range of a centralized seawater heat exchanger according to Embodiment 1 of the present invention; Figure 3This is a schematic diagram of a system for determining the self-flowing cooling range of a centralized seawater heat exchanger, as described in Embodiment 1 of the present invention. Figures 1 to 3 As shown in Embodiment 1, a method for determining the self-flowing cooling range of a centralized seawater heat exchanger is applied to a system for determining the self-flowing cooling range of a centralized seawater heat exchanger. The system includes a controller, a power switch, a first temperature sensor, a second temperature sensor, and a seawater pump, a centralized seawater heat exchanger, and a freshwater circuit connected in sequence.

[0029] Specifically, the centralized seawater heat exchanger includes a seawater heat exchanger and a freshwater heat exchanger. The seawater in the seawater heat exchanger is used to cool the freshwater in the freshwater heat exchanger. The seawater heat exchanger includes a seawater inlet and a seawater outlet, and the freshwater heat exchanger includes a freshwater inlet and a freshwater outlet. The inlet of the seawater pump is connected to the seawater inlet, and the outlet of the seawater pump is connected to the seawater inlet through a first pipeline. The two ends of the freshwater circuit are connected to the freshwater inlet and the freshwater outlet through a second pipeline and a third pipeline, respectively. A first temperature sensor is installed outside the seawater inlet of the centralized seawater heat exchanger (on the seawater-connected pipeline before the seawater pump) to measure the seawater temperature in real time. A second temperature sensor is installed on the third pipeline to measure the freshwater outlet temperature in real time. The controller is electrically connected to the first temperature sensor, the second temperature sensor, and the power switch. The power switch is electrically connected to the seawater pump. The controller stores the limit value t of the seawater temperature for self-flow cooling of the centralized seawater heat exchanger. a The current value and the freshwater outlet temperature limit t0. The controller receives measurements from two temperature sensors and the power switch status, performs calculations according to step S400, and implements control, including changing the power switch from closed to open or from open to closed, thereby changing the seawater pump from start to stop or from stop to start. When the seawater pump stops running, step S500 adjusts t0 accordingly. a Update.

[0030] Methods for determining the self-flow cooling range of a centralized seawater heat exchanger include:

[0031] Step S100: Obtain the freshwater outlet temperature limit of the seawater centralized heat exchanger.

[0032] Specifically, a limit value t0 is set for the freshwater outlet temperature on the hot side of the centralized seawater heat exchanger.

[0033] Step S200: Obtain the initial value of the upper limit of the self-flowing cooling seawater temperature of the centralized seawater heat exchanger.

[0034] Specifically, based on the ship speed, the seawater temperature t that will cause the freshwater outlet temperature on the hot side of the seawater centralized heat exchanger to reach its limit t0 under gravity cooling conditions is estimated. a .

[0035] Step S300: Obtain the seawater temperature and the freshwater outlet temperature of the seawater central heat exchanger.

[0036] Specifically, the seawater temperature t1 and the freshwater outlet temperature t2 of the seawater central heat exchanger are measured.

[0037] Step S400: Determine whether to start or stop the seawater pump.

[0038] Specifically, the operation logic for stopping and starting the seawater pump is defined, that is, when the seawater temperature t1≤t a -Δt and when the current seawater pump starts, the seawater pump stops running, where Δt is a given temperature interval to prevent crossing the control boundary; when the seawater temperature t1≥t a And when the current seawater pump is stopped, start the seawater pump.

[0039] Step S500: When the seawater pump stops operating, the upper limit of the self-flowing cooling seawater temperature is corrected by the seawater temperature and the freshwater outlet temperature.

[0040] Specifically, when the seawater pump stops running, the time is controlled by t1 and t2. a Perform correction; if t2 > t0, then take t. a = t1 – xΔt; otherwise, calculate the intermediate quantity t. a *=t1+x(t0–t2), take t a =max(t) a ,t a *), where x is a coefficient less than 1.

[0041] Step S600, return to step S300.

[0042] Based on the above analysis, it can be seen that, following the above method, the seawater temperature limit t can be continuously monitored during ship operation. a The system is calibrated so that when the seawater pump stops operating at this seawater temperature, the freshwater outlet temperature on the hot side of the centralized seawater heat exchanger exactly reaches the specified limit t0. This ensures the safe operation of the freshwater loop equipment and avoids starting the seawater pump unnecessarily, thus supporting the ship's high-efficiency operation. a After continuous calibration, the upper limit of the seawater temperature that the seawater central heat exchanger can self-cool is determined.

[0043] In this embodiment, step S100 includes:

[0044] Step S101: Set the freshwater outlet temperature limit of the seawater centralized heat exchanger;

[0045] Step S102: The controller acquires the freshwater outlet temperature limit of the seawater centralized heat exchanger.

[0046] In this embodiment, step S200 includes:

[0047] Step S201: Obtain the cold-side gravity flow rate, hot-side freshwater flow rate, freshwater loop heat load, and heat exchange area of ​​the seawater centralized heat exchanger at a preset speed.

[0048] Step S202: Using the heat balance equation, generate the initial value of the upper limit of the temperature of the self-flowing cooling seawater;

[0049] Step S203: The controller acquires the initial value of the upper limit of the temperature of the self-flowing cooling seawater.

[0050] Specifically, estimate the cold-side gravity flow rate G1 and the hot-side freshwater flow rate G2 of the seawater centralized heat exchanger at this speed, the freshwater loop heat load Q, and the heat exchange area A of the seawater centralized heat exchanger, using the heat balance equation:

[0051]

[0052] in

[0053]

[0054]

[0055] Δt in =t2-t1

[0056]

[0057] Where t1 and t'1 are the inlet and outlet temperatures of seawater, and t'2 and t2 are the inlet and outlet temperatures of freshwater, t2 = t0, meaning the freshwater outlet temperature on the hot side exactly reaches the specified limit t0. p1 For the specific heat of seawater, c p2 Let Δt1 be the specific heat of freshwater, Δt2 be the temperature rise of seawater, and Δt be the temperature rise of freshwater. in The difference in elevation at the seawater inlet is Δt. out It is the difference at the seawater outlet.

[0058] Because Q, G1, G2, c p1 c p2 Given quantities such as t0 and A, and based on the heat transfer characteristics of the seawater centralized heat exchanger, the overall heat transfer coefficient K and the seawater inlet temperature t1 can be calculated using the above heat balance equation. At this point, t1 is the seawater temperature limit t. a The initial value.

[0059] In this embodiment, step S300 includes:

[0060] Step S301: The first temperature sensor measures the seawater temperature;

[0061] Step S302: The second temperature sensor measures the freshwater outlet temperature of the seawater centralized heat exchanger;

[0062] In step S303, the controller acquires the seawater temperature and the freshwater outlet temperature.

[0063] In this embodiment, step S400 includes:

[0064] Step S401: Preset the first condition and the second condition;

[0065] Step S402: When the first condition is met, the controller controls the seawater pump to stop running;

[0066] Step S403: When the second condition is met, the controller controls the seawater pump to start.

[0067] In this embodiment, the first condition is: t1≤t a -Δt; where t1 is the seawater temperature, t a The upper limit of the temperature of the self-flowing cooled seawater is given, and Δt is the given temperature interval.

[0068] In this embodiment, the second condition is: t1≥t a Where t1 is the seawater temperature, t a This represents the upper limit of the temperature of the self-flowing cooled seawater.

[0069] In this embodiment, step S500 includes:

[0070] Step S501: When the seawater pump stops running, t1 and t2 are used to control t. a Perform correction;

[0071] Step S502, if t2 > t0, take t a = t1 - xΔt;

[0072] Step S503: If t2 < t0, calculate the intermediate quantity t. a *=t1+x(t0–t2), take t a =max(t) a ,t a *); where t0 is the freshwater outlet temperature limit, t1 is the seawater temperature, t2 is the freshwater outlet temperature, x is a coefficient less than 1, and Δt is the given temperature interval.

[0073] Based on the above, in order to meet the requirements of refined energy-saving operation of centralized seawater cooling systems, and to determine the self-flow cooling range of centralized seawater heat exchangers, the method for determining the self-flow cooling range of centralized seawater heat exchangers provided in this embodiment can correct the upper limit of the seawater temperature for self-flow cooling of centralized seawater heat exchangers based on the seawater inlet temperature and the freshwater outlet temperature.

[0074] Secondly, the present invention provides a ship, including a system for determining the self-flowing cooling range of a centralized seawater heat exchanger, wherein the system employs the method for determining the self-flowing cooling range of a centralized seawater heat exchanger as described above.

[0075] In practical applications, specific calculation examples are as follows:

[0076] A certain ship adopts a fully enclosed central cooling system, and the heat exchange area A of the seawater centralized heat exchanger is 1000m². 2 The specific heat of seawater is approximately 4000 J / (kg℃), and the specific heat of freshwater is approximately 4200 J / (kg℃). The calculation is based on a ship speed of 14 knots.

[0077] According to step S100, the limit value t0 of the freshwater outlet temperature on the hot side of the seawater centralized heat exchanger is set to 32℃.

[0078] Estimate the seawater temperature t according to step S200. a First, at a speed of 14 knots, the cold-side gravity flow rate G1 and the hot-side freshwater flow rate G2 of the centralized seawater heat exchanger are estimated to be 700 t / h and 600 t / h respectively, with a total heat load Q of 3.5 MW. Based on the single-phase flow heat transfer estimation using a shell-and-tube heat exchanger, the overall heat transfer coefficient K is approximately 850 W / (m³). 2 The required seawater inlet temperature t1 is approximately 28.13℃, i.e., t a The initial value is 28.13℃, at which point the freshwater outlet temperature on the hot side of the seawater central heat exchanger reaches 32℃.

[0079] According to step S300, the measured seawater temperature t1 and the freshwater outlet temperature t2 of the seawater central heat exchanger are 25.6℃ and 30.3℃, respectively.

[0080] According to step S400, the temperature interval Δt is taken as 2℃. Assuming the seawater pump is currently running, since t1 <t a -Δt, therefore the seawater pump is shut down.

[0081] According to step S500, after the seawater pump stops operating, the measured freshwater outlet temperature t2 of the centralized seawater heat exchanger is 31.5℃. Taking the coefficient x = 0.5, the t2 temperature is calculated. a *=t1+x(t0–t2)=25.85℃ <t a Therefore, t a It remains unchanged.

[0082] In summary, the method for determining the self-flow cooling range of the seawater centralized heat exchanger and the vessel of the present invention can continuously correct the seawater temperature limit for self-flow cooling of the seawater centralized heat exchanger by measuring the seawater inlet temperature and the freshwater outlet temperature, thereby enabling the timely switching of the seawater pump to start and stop, ensuring the efficient operation of the seawater cooling system, and having good economic value for the operation of the vessel.

[0083] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for determining the self-flowing cooling range of a centralized seawater heat exchanger, applied to a system for determining the self-flowing cooling range of a centralized seawater heat exchanger, the system comprising a controller, a power switch, a first temperature sensor, a second temperature sensor, and a seawater pump, a centralized seawater heat exchanger, and a freshwater circuit connected in sequence, characterized in that, The method includes: Step S100: Obtain the freshwater outlet temperature limit of the seawater centralized heat exchanger; Step S200: Obtain the initial value of the upper limit of the self-flowing cooling seawater temperature of the seawater centralized heat exchanger; Step S300: Obtain the seawater temperature and the freshwater outlet temperature of the seawater centralized heat exchanger; Step S400: Determine whether to start or stop the seawater pump; Step S500: When the seawater pump stops, the upper limit of the self-flowing cooling seawater temperature is corrected by the seawater temperature and the freshwater outlet temperature. Step S600, return to step S300; Step S400 includes: Step S401: Preset the first condition and the second condition; Step S402: When the first condition is met, the controller controls the seawater pump to stop running; Step S403: When the second condition is met, the controller controls the seawater pump to start. The first condition is: t1≤t a -Δt; Where t1 is the seawater temperature, t a The upper limit of the temperature of the self-flowing cooling seawater is given, and Δt is the given temperature interval. The second condition is: t1≥t a ; Where t1 is the seawater temperature, t a This represents the upper limit of the temperature of the self-flowing cooling seawater; Step S500 includes: Step S501: When the seawater pump stops running, t1 and t2 are used to control t. a Perform correction; Step S502, if t2 > t0, take t a =t1-xΔt; Step S503, if t2 < t0, calculate t a *=t1+x(t0–t2), take t a =max(t a ,t a *); Where t0 is the freshwater outlet temperature limit, t1 is the seawater temperature, t2 is the freshwater outlet temperature, x is a coefficient less than 1, Δt is the given temperature interval, and t a *For use in updating t a The intermediate quantity.

2. The method for determining the self-flowing cooling range of a centralized seawater heat exchanger as described in claim 1, characterized in that, Step S100 includes: Step S101: Set the freshwater outlet temperature limit of the seawater centralized heat exchanger; Step S102: The controller acquires the freshwater outlet temperature limit of the seawater centralized heat exchanger.

3. The method for determining the self-flowing cooling range of a centralized seawater heat exchanger as described in claim 1, characterized in that, Step S200 includes: Step S201: Obtain the cold-side gravity flow rate, hot-side freshwater flow rate, freshwater loop heat load, and heat exchange area of ​​the seawater centralized heat exchanger at a preset speed. Step S202: Using the heat balance equation, generate the initial value of the upper limit of the temperature of the self-flowing cooling seawater; Step S203: The controller acquires the initial value of the upper limit of the temperature of the self-flowing cooling seawater.

4. The method for determining the self-flowing cooling range of a centralized seawater heat exchanger as described in claim 1, characterized in that, Step S300 includes: Step S301: The first temperature sensor measures the seawater temperature; Step S302: The second temperature sensor measures the freshwater outlet temperature of the seawater centralized heat exchanger; In step S303, the controller acquires the seawater temperature and the freshwater outlet temperature.

5. A ship, characterized in that, The system includes a system for determining the self-flowing cooling range of a centralized seawater heat exchanger, wherein the system employs the method for determining the self-flowing cooling range of a centralized seawater heat exchanger as described in any one of claims 1-4.

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