A marine urea tank cooling system and method

Abstract

This invention discloses a cooling system and method for a ship's urea tank, comprising a refrigeration circulation unit, a urea tank, and a urea circulation pipeline. The refrigeration circulation unit includes a compressor, a condenser, an expansion valve, and an evaporator connected in sequence. The evaporator includes a shell and evaporation pipes disposed within the shell. The evaporation pipes are connected to the expansion valve and the compressor. The shell has a urea solution inlet and a urea solution outlet. The urea circulation pipeline connects the urea tank and the evaporator shell, and is used to directly transport the urea solution in the urea tank to the evaporator shell, where it exchanges heat with the refrigerant flowing through the evaporation pipes before being returned to the urea tank. This invention improves heat exchange efficiency by directly introducing the urea solution into the evaporator shell for cooling, eliminating the need for intermediate heat exchange media or independent coil structures. The forced convection within the urea tank is enhanced through the nozzles or diagonal arrangement of the return pipeline, solving the problem of temperature stratification in the urea tank. This invention has the advantages of compact structure, high cooling efficiency, and low cost.

Description

Technical Field

[0001] This invention relates to the field of marine technology, specifically to a cooling system and method for a ship's urea tank. Background Technology

[0002] With increasingly stringent ship emission standards, new ships generally adopt selective catalytic reduction (SCR) technology for exhaust gas treatment to meet TIER III emission requirements. This necessitates the installation of urea tanks on board to store urea solution as a reducing agent. The storage temperature of the urea solution must be strictly controlled; excessively high temperatures can lead to urea deterioration, while excessively low temperatures can cause crystallization. Therefore, a urea tank cooling system is essential.

[0003] Existing urea tank cooling systems are mainly divided into two categories: The first category uses direct cooling with seawater coils, where seawater is drawn from the seawater tank by the main seawater pump and cooled by heat exchange between the seawater and the urea solution inside the tank. This method has the following problems: the cooling coils are prone to corrosion due to long-term contact with seawater; in some sea areas or seasons, the seawater temperature is higher than the urea storage temperature, making effective cooling impossible and leading to a shortened storage life or even deterioration of the urea solution. The second category uses indirect cooling with low-temperature freshwater produced by a refrigeration unit, where freshwater at 5-25°C is produced by a refrigeration unit and then used to cool the urea solution in the urea tank through a freshwater circulation pipeline. This method has the following problems: the cooling coils are located at the bottom of the urea tank, and the density of the urea at the bottom increases after cooling, making it impossible to form effective convection heat exchange within the tank through density difference. This results in low overall cooling efficiency and slow cooling of the urea tank, and temperature stratification occurs with lower temperatures at the bottom and higher temperatures at the top, affecting the storage life of the urea.

[0004] Chinese invention patent CN115750045B discloses a ship cooling device that combines an air conditioning refrigeration cycle unit with a urea cooling unit. The urea cooling unit includes an independent urea system evaporator, where the urea solution indirectly exchanges heat with the refrigerant through urea coils within the evaporator. While this solution solves the corrosion problem associated with direct seawater cooling, it still employs an indirect heat exchange method and does not effectively address the temperature stratification issue within the urea tank, leaving room for improvement in cooling efficiency.

[0005] Therefore, it is necessary to provide a ship urea tank cooling system and method to solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a shipboard urea tank cooling system and method that is compact in structure, highly efficient in cooling, and can effectively solve the problem of temperature stratification in urea tanks.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A ship urea tank cooling system, comprising:

[0009] A refrigeration cycle unit, comprising a compressor, a condenser, an expansion valve, and an evaporator connected sequentially by pipelines to form a refrigerant circuit;

[0010] The evaporator includes a shell and an evaporation tube disposed inside the shell. The inlet of the evaporation tube is connected to an expansion valve, and the outlet of the evaporation tube is connected to a compressor. The shell of the evaporator is provided with a urea solution inlet and a urea solution outlet.

[0011] Urea tank, used to store urea solution;

[0012] The urea circulation pipeline connects the urea tank and the evaporator shell, and is used to transport the urea solution in the urea tank to the evaporator shell. After exchanging heat with the refrigerant flowing in the evaporator tube, the cooled urea solution is sent back to the urea tank.

[0013] Preferably, the urea circulation pipeline includes an outlet pipeline and a return pipeline. One end of the outlet pipeline is connected to the liquid inlet of the urea tank, and the other end is connected to the urea solution inlet of the evaporator shell. A circulation pump is installed on the outlet pipeline. One end of the return pipeline is connected to the urea solution outlet of the evaporator shell, and the other end is connected to the liquid return port of the urea tank.

[0014] Preferably, the urea tank's suction port and return port are arranged diagonally to create forced convection circulation within the urea tank.

[0015] Preferably, one end of the return pipeline is connected to the urea tank return port and extends into the urea tank. The section of the return pipeline located in the urea tank has multiple spray holes along its circumference. The cooled low-temperature urea solution is sprayed out through the spray holes, forming turbulent convection in the urea tank, thereby achieving uniform diffusion of the urea solution's cooling capacity.

[0016] Preferably, the condenser is a water-cooled condenser, including condenser tubes and a shell. The shell is connected to a cooling water inlet pipe and a cooling water outlet pipe, respectively, and the heat of the refrigerant in the condenser tubes is removed by the cooling water circulation.

[0017] Preferably, the expansion valve is used to control the evaporation pressure in the evaporator, so that the temperature of the refrigerant in the evaporator is not lower than 2°C, and to prevent the urea solution from crystallizing in the evaporator.

[0018] Preferably, a dryer filter is installed on the pipeline between the expansion valve and the condenser, the dryer filter being used to absorb moisture in the refrigerant and filter solid impurities.

[0019] A method for cooling a ship's urea tank using a ship's urea tank cooling system includes the following steps:

[0020] S1. Start the compressor of the refrigeration cycle unit. The refrigerant is compressed into a high-pressure gaseous state by the compressor and then enters the condenser through the pipeline. The condenser is fed seawater or central cooling fresh water through the cooling water inlet pipe. The seawater or central cooling fresh water exchanges heat with the refrigerant in the condenser tube, and the refrigerant liquefies into a high-pressure liquid state.

[0021] S2. After the high-pressure liquid refrigerant is throttled and depressurized by the expansion valve to a low-temperature, low-pressure liquid state, it enters the evaporator tube of the evaporator. The refrigerant vaporizes and absorbs heat in the evaporator tube, and forms a low-temperature heat exchange environment in the shell of the evaporator. The minimum temperature of the refrigerant is controlled to be no lower than 2°C.

[0022] S3. Start the circulation pump on the outlet pipeline to transport the urea solution in the urea tank to the shell of the evaporator through the outlet pipeline. The urea solution exchanges heat with the refrigerant in the evaporator tube in the shell, and the urea solution is cooled down.

[0023] S4. The cooled low-temperature urea solution is transported back to the urea tank through the return pipeline. Forced convection is formed in the urea tank by diffusion through nozzles or diagonal arrangement to achieve uniform transfer of cold energy throughout the tank.

[0024] S5. When the temperature of the urea solution in the urea tank rises again, repeat steps S1 to S4 to form a closed-loop cooling system for the urea solution.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. This invention uses a closed refrigeration circulation unit to cool the urea solution. The urea solution does not come into contact with seawater, which completely avoids the corrosion problem of seawater on the cooling pipes and extends the service life of the system. At the same time, the refrigeration circulation unit can stably provide cooling capacity below the seawater temperature, which is not affected by the sea area or season, ensuring that the storage temperature of the urea solution is always within a suitable range.

[0027] 2. The present invention adopts a method of not installing a cooling water pan in the cabin, which can effectively avoid the risks of low heat exchange efficiency, corrosion and leakage of the coils in the cabin. It also avoids the complicated operation and maintenance process of intermittent operation of the system and removal and drying of seawater in the pipes when the system is shut down due to the cooling of seawater coils in the cabin, thereby reducing the system operation and maintenance costs.

[0028] 3. This invention introduces urea solution directly into the evaporator shell for indirect heat exchange with the refrigerant, eliminating the need for intermediate refrigerant and its circulation pipeline, reducing the number of heat exchange stages, and improving heat exchange efficiency; at the same time, the urea solution is in direct contact with the evaporator tube bundle inside the evaporator shell, resulting in a larger heat exchange area and a more significant cooling effect.

[0029] 4. By setting the spray holes or suction ports diagonally with the return port in the return pipeline, the present invention creates forced convection or turbulence in the urea tank, effectively solving the problem of temperature stratification in the urea tank, achieving uniform distribution of cooling capacity throughout the tank, and further extending the storage life of the urea solution. Attached Figure Description

[0030] Figure 1 This is a system schematic diagram of Embodiment 1 of the present invention;

[0031] Figure 2 This is a system schematic diagram of Embodiment 2 of the present invention;

[0032] Among them, 1-compressor, 2-condenser, 201-cooling water inlet pipe, 202-cooling water outlet pipe, 3-expansion valve, 4-evaporator, 5-drier filter, 6-urea tank, 7-outlet pipe, 8-return pipe, 9-circulation pump Detailed Implementation

[0033] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and not for limiting the scope of the invention. After reading this invention, any modifications of the invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0034] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixed connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] In this invention, terms such as "upper," "lower," "bottom," and "top" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are merely relational terms determined for the convenience of describing the structural relationship of the various components or elements of this invention, and do not specifically refer to any component or element in this invention, and should not be construed as limiting this invention.

[0036] Example 1

[0037] like Figure 1 As shown, the present invention provides a ship urea tank cooling system, including a refrigeration circulation unit, a urea tank, and urea circulation pipelines;

[0038] The refrigeration cycle unit includes a compressor 1, a condenser 2, an expansion valve 3, and an evaporator 4, which are connected sequentially through pipes to form a refrigerant circuit. The compressor is used to compress the low-temperature, low-pressure gaseous refrigerant into a high-temperature, high-pressure gaseous refrigerant. The condenser is a water-cooled condenser, including condenser tubes and a shell. The shell is connected to a cooling water inlet pipe 201 and a cooling water outlet pipe 202, which is used to remove the heat of the refrigerant in the condenser tubes through seawater or central cooling fresh water circulation, so that the refrigerant condenses from a gaseous state to a high-pressure liquid state. The expansion valve is used to throttle and reduce the pressure, turning the high-pressure liquid refrigerant into a low-temperature, low-pressure liquid refrigerant. At the same time, it is used to control the evaporation pressure in the evaporator, so that the temperature of the refrigerant in the evaporator is not lower than 2°C, to prevent the urea solution from crystallizing in the evaporator. The evaporator includes a shell and evaporator tubes installed in the shell. The inlet of the evaporator tubes is connected to the expansion valve, and the outlet of the evaporator tubes is connected to the compressor. The shell of the evaporator has a urea solution inlet and a urea solution outlet. A dryer filter 5 is also installed on the pipeline between the expansion valve and the condenser to absorb moisture in the refrigerant and filter solid impurities, ensuring the cleanliness and reliability of the refrigeration system.

[0039] The urea tank 6 is used to store urea solution and has an internal suction port and a return port. The urea circulation pipeline includes an outlet pipe 7 and a return pipe 8. One end of the outlet pipe 7 is connected to the suction port of the urea tank 6, and the other end is connected to the urea solution inlet of the evaporator 4 shell. A circulation pump 9 is installed on the outlet pipe. One end of the return pipe is connected to the urea solution outlet of the evaporator shell, and the other end is connected to the return port of the urea tank.

[0040] In this embodiment, the suction port and return port of the urea tank 6 are arranged diagonally, that is, the suction port is located at the bottom or lower part of one side of the urea tank, and the return port is located at the upper part of the opposite side of the urea tank. This arrangement allows the cooled low-temperature urea solution to enter the urea tank through the return port, forming a forced convection circulation from top to bottom or from one side to the other within the tank. This effectively avoids the problem of insufficient natural convection caused by density differences and achieves a uniform temperature field distribution within the urea tank.

[0041] The principle and usage method of this embodiment are as follows:

[0042] S1. Start the compressor of the refrigeration cycle unit. The refrigerant is compressed into a high-pressure gaseous state by the compressor and then enters the condenser through the pipeline. The condenser is fed seawater or central cooling fresh water through the cooling water inlet pipe. The seawater or central cooling fresh water exchanges heat with the refrigerant in the condenser tube, and the refrigerant liquefies into a high-pressure liquid state.

[0043] S2. After the high-pressure liquid refrigerant passes through the dryer filter to remove moisture and impurities, it enters the expansion valve for throttling and pressure reduction, becoming a low-temperature, low-pressure liquid refrigerant. It then enters the evaporator tubes of the evaporator. The refrigerant vaporizes and absorbs heat within the evaporator tubes, creating a low-temperature heat exchange environment within the evaporator shell. The expansion valve controls the evaporation temperature to be no lower than 2°C to prevent urea crystallization.

[0044] S3. When the temperature of the urea solution in the urea tank rises to the set value, the circulation pump on the outlet pipeline is started, and the urea solution in the urea tank is transported to the shell of the evaporator through the outlet pipeline. The urea solution exchanges heat with the refrigerant in the evaporator tube in the shell, and the urea solution is cooled down.

[0045] S4. The cooled low-temperature urea solution is transported back to the urea tank through the return pipeline. Forced convection is formed in the urea tank through the diagonally arranged return ports to achieve uniform transfer of cooling capacity throughout the tank.

[0046] S5. When the temperature of the urea solution in the urea tank rises again, repeat steps S1 to S4 to form a closed-loop cooling system for the urea solution.

[0047] Example 2

[0048] like Figure 2 As shown, the present invention provides a ship urea tank cooling system, the main difference of which is the different convection enhancement structure inside the urea tank compared with Embodiment 1.

[0049] In this embodiment, the basic structure of the refrigeration cycle unit, urea tank and urea circulation pipeline is the same as that in Embodiment 1. The difference is that one end of the return pipeline is connected to the urea tank return port and extends into the urea tank. Multiple spray holes are provided along the circumferential direction on the section of the return pipeline located in the urea tank.

[0050] Specifically, the return pipe 8 extends into the urea tank 6 from the top or side wall, forming a horizontally or vertically arranged spray pipe section within the tank. This pipe section has multiple spray holes evenly or non-uniformly distributed along its circumference. The cooled, low-temperature urea solution is transported into the tank via the return pipe and sprayed out through the spray holes, creating strong turbulent convection within the urea tank. This ensures thorough mixing of the low-temperature urea solution with the existing urea solution, achieving rapid and uniform diffusion of cooling energy. The orifice diameter, number, and arrangement density can be optimized based on the urea tank volume and circulation flow rate to guarantee the best mixing effect.

[0051] The foregoing description illustrates and describes preferred embodiments of the present invention. As previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A ship urea tank cooling system, characterized in that, include: A refrigeration cycle unit includes a compressor, a condenser, an expansion valve, and an evaporator connected in sequence through pipelines to form a refrigerant circuit; wherein, the evaporator includes a shell and an evaporation tube disposed within the shell, the inlet of the evaporation tube is connected to the expansion valve, the outlet of the evaporation tube is connected to the compressor, and the shell of the evaporator has a urea solution inlet and a urea solution outlet. The urea tank is used to store urea solution; the urea circulation pipeline connects the urea tank and the evaporator shell, and is used to transport the urea solution in the urea tank to the evaporator shell, exchange heat with the refrigerant flowing in the evaporator tube, and then send the cooled urea solution back to the urea tank.

2. The ship urea tank cooling system according to claim 1, characterized in that: The urea circulation pipeline includes an outlet pipeline and a return pipeline. One end of the outlet pipeline is connected to the liquid inlet of the urea tank, and the other end is connected to the urea solution inlet of the evaporator shell. A circulation pump is installed on the outlet pipeline. One end of the return pipeline is connected to the urea solution outlet of the evaporator shell, and the other end is connected to the liquid return port of the urea tank.

3. A ship urea tank cooling system according to claim 2, characterized in that: The urea tank's suction port and return port are arranged diagonally to create forced convection circulation within the urea tank.

4. A ship urea tank cooling system according to claim 2, characterized in that: One end of the return pipeline is connected to the return port of the urea tank and extends into the urea tank. Multiple spray holes are opened circumferentially on the section of the return pipeline located in the urea tank. The cooled low-temperature urea solution is sprayed out through the spray holes, forming turbulent convection in the urea tank, so as to achieve uniform diffusion of the cold energy of the urea solution.

5. A ship urea tank cooling system according to claim 1, characterized in that: The condenser is a water-cooled condenser, including condenser tubes and a shell. The shell is connected to a cooling water inlet pipe and a cooling water outlet pipe, respectively, and the heat of the refrigerant in the condenser tubes is removed by the cooling water circulation.

6. A ship urea tank cooling system according to claim 1, characterized in that: The expansion valve is used to control the evaporation pressure in the evaporator, ensuring that the temperature of the refrigerant in the evaporator is not lower than 2°C, and to prevent the urea solution from crystallizing in the evaporator.

7. A ship urea tank cooling system according to claim 1, characterized in that: A dryer filter is installed on the pipeline between the expansion valve and the condenser. The dryer filter is used to absorb moisture in the refrigerant and filter out solid impurities.

8. A method for cooling a ship's urea tank using the system according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Start the compressor of the refrigeration cycle unit. The refrigerant is compressed into a high-pressure gaseous state by the compressor and then enters the condenser through the pipeline. The condenser is fed seawater or central cooling fresh water through the cooling water inlet pipe. The seawater or central cooling fresh water exchanges heat with the refrigerant in the condenser tube, and the refrigerant liquefies into a high-pressure liquid state. S2. After the high-pressure liquid refrigerant is throttled and depressurized by the expansion valve to a low-temperature, low-pressure liquid state, it enters the evaporator tube of the evaporator. The refrigerant vaporizes and absorbs heat in the evaporator tube, and forms a low-temperature heat exchange environment in the shell of the evaporator. The minimum temperature of the refrigerant is controlled to be no lower than 2°C. S3. Start the circulation pump on the outlet pipeline to transport the urea solution in the urea tank to the shell of the evaporator through the outlet pipeline. The urea solution exchanges heat with the refrigerant in the evaporator tube in the shell, and the urea solution is cooled down. S4. The cooled low-temperature urea solution is transported back to the urea tank through the return pipeline. Forced convection is formed in the urea tank by diffusion through nozzles or diagonal arrangement to achieve uniform transfer of cold energy throughout the tank. S5. When the temperature of the urea solution in the urea tank rises again, repeat steps S1 to S4 to form a closed-loop cooling system for the urea solution.

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