A ventilation energy-saving system for the refrigerated cargo hold of an ammonia-powered container ship

Abstract

The present invention discloses a ventilation energy-saving system for a refrigerated cargo hold of an ammonia-powered container ship, which is composed of a temperature monitoring system, an air precooling system, a ventilation pipeline system and a central control system; the temperature monitoring system is composed of temperature induction probes arranged at the ends of the heat dissipation outlets of the refrigerated containers, and is mainly responsible for real-time monitoring of the temperature information near the heat dissipation outlets of the containers; the air precooling system is responsible for cooling normal-temperature air into low-temperature air through a heat exchanger; the ventilation pipeline system sends the cooled low-temperature air to the specific positions of the refrigerated containers in the refrigerated cargo hold; the central control system is responsible for simulating and calculating the temperature field distribution and the number and positions of the refrigerated containers in the refrigerated cargo hold according to the received temperature monitoring data, and formulating and sending specific instructions: controlling the opening, closing, blowing air volume and the rotational speed and power of the ventilation fans of each air outlet. The present invention rationally utilizes the heat exchange process in which ammonia fuel absorbs energy during the gasification process, optimizes the form of the ventilation ducts, and achieves the best temperature reduction effect for the refrigerated cargo hold.

Description

Technical Field

[0001] The present invention belongs to the field of ventilation energy conservation of cargo holds, and particularly relates to a ventilation energy conservation system for a refrigerated cargo hold of an ammonia-powered container ship. Background Art

[0002] With the advancement of the global carbon neutrality strategy and technological progress, low-carbon fuel container ships will become a reality. Ammonia fuel, due to its characteristics such as zero carbon and high boiling point, has gradually become one of the preferred low-carbon fuel options for container ships. Ammonia fuel is usually stored in a liquid state at -33°C under atmospheric pressure, and needs to be vaporized before use. During the vaporization process of ammonia fuel, a large amount of heat from the surrounding air needs to be absorbed. During this heat absorption process, the temperature of the surrounding air will decrease.

[0003] The containers carried on container ships are usually divided into general containers and refrigerated containers. With the increasing demand for fresh food by people, the number of refrigerated containers carried on large container ships has been continuously increasing. According to statistics, the number of refrigerated containers on large container ships has reached 1000 - 2000 containers.

[0004] Refrigerated containers are equipped with their own refrigeration units. While the refrigeration units are refrigerating, they dissipate heat to the cargo hold. When a large number of refrigerated containers dissipate heat simultaneously, the temperature of the cargo hold will rise. The increase in the temperature of the cargo hold will reduce the refrigeration effect of the refrigerated containers.

[0005] In order to avoid the temperature of the cargo hold rising and exceeding the standard due to the heat dissipation of the refrigeration machines, the existing technical solution is to use a supply air fan to blow the air outside the cargo hold into the refrigerated cargo hold to lower the ambient temperature inside the cargo hold. To ensure an appropriate cargo hold temperature, taking the ventilation requirement of a single 40-inch refrigerated container reaching 75m 3 / min as an example, the total power consumed by the supply air fans for the whole ship will reach more than 2800 kW. Moreover, the fans need to be continuously turned on throughout the process, and the amount of electric energy consumed during the entire voyage is astonishing. Fan ventilation has now become a major power consumer on container ships.

[0006] For ship design, an increase in ventilation capacity not only poses a severe challenge to the spatial layout of ventilation ducts but also brings a serious test to the power load of the ship's power grid.

[0007] In actual operation, the number and positions of reefer containers in each voyage may change. Based on the existing ventilation technology solution: the power and air volume of the ventilation fans for the entire voyage are fixed values, and each ventilation duct only has an air outlet at the bottom of the cargo hold, and the position of the air outlet cannot be adjusted. When the number of reefer containers, the stowage position, the external temperature, etc. in the cargo hold change, the air volume of the fan and the position of the air outlet cannot be adjusted accordingly; the energy consumption of the fan cannot be adjusted in real time with the changes in the number and position of the reefer containers. For example, when there are only a small number of reefer containers left in the refrigerated cargo hold, ventilation is still carried out according to the full-load condition of the refrigerated cargo hold, which will cause an excessive consumption of fan power. How to achieve dynamic adjustment of the ventilation fan power with the number of refrigerated containers, the cargo hold temperature, etc. is one of the important means to achieve energy saving in fan ventilation.

[0008] For ammonia-powered container ships, energy conservation and emission reduction are the fundamental design goals. In this context, how to study methods to reduce the power consumption of the ventilation fans in the refrigerated cargo hold around the characteristics of ammonia-powered ships will be the key to the energy-saving design of ammonia-powered ships. First of all, how to reasonably use ammonia fuel to cool the air and blow the cooled air into the refrigerated cargo hold to reduce the ventilation power of the ventilation fans and reduce the power consumption.

[0009] How to optimize the layout of the ventilation pipeline to improve the air outlet layout, so as to control the flow rate and the number of air outlets, and reduce the energy consumption during the ventilation of the refrigerated cargo hold. By monitoring the temperature in the cargo hold, the position of the reefer containers, the number of reefer containers, etc., ensure that the power of the ventilation fan is accurately matched with the number and position of the reefer containers in the refrigerated cargo hold. To achieve precise utilization of energy and real-time management of power consumption.

[0010] The application number is: 202011390870.6, and the patent name is: An energy-saving system for improving the temperature of the cargo hold of a container ship by using LNG cold energy. The system of this patent can make full use of LNG cold energy, improve the utilization rate of cold energy, reduce the environmental temperature of the cargo hold, reduce the permeation heat between the insulation layer of the refrigerated container and the air in the cargo hold, and reduce the heat load of the refrigerated container body. The system of this patent reduces the condensation temperature of the refrigeration unit, improves the coefficient of performance of the refrigeration unit, reduces the power consumed by the refrigeration equipment of the refrigerated container, thereby reducing the load on the ship's power grid, and further reducing fuel consumption. The system of this patent uses the cold energy of LNG to improve the environmental temperature of the cargo hold, saving the heat of the jacket water required for heating LNG fuel. In addition, since there are a large number of refrigerated containers on the ship and the amount of cold energy required to cool the air in the cargo hold is large, almost most of the cold energy of LNG fuel can be fully utilized. For the cargo hold, the system of this patent does not require modification of the cargo hold structure, and only needs to install ventilation pipes to achieve it, which is simple, convenient, easy to implement, and has a low cost, and is suitable for newly built ships and existing ships.

[0011] Application No.: 201911110018.6, Patent Name: Ventilation Structure of Cargo Hold of Container Ship. Through the layout of lateral ventilation, this patent enables effective air flow in the cargo hold space at the end face of the refrigerated container, achieving a good cooling effect throughout the space. This patent can achieve good ventilation even when the cargo hold is filled with refrigerated containers, and simplifies the layout of air ducts as much as possible, reducing the installation and commissioning workload of the shipyard. The variable frequency control technology is used in the cargo hold ventilation system to achieve energy conservation and good ventilation effect. Summary of the Invention

[0012] Object of the Invention: To solve the deficiencies of the prior art, the present invention provides a ventilation and energy-saving system for the refrigerated cargo hold of an ammonia-powered container ship.

[0013] Technical Solution: A ventilation and energy-saving system for the refrigerated cargo hold of an ammonia-powered container ship, the ventilation and energy-saving system is composed of a temperature monitoring system, an air precooling system, a ventilation pipeline system and a central control system; among them:

[0014] The temperature monitoring system is composed of temperature induction probes arranged at the end of the refrigerated container heat dissipation port, mainly responsible for real-time monitoring of the temperature information near the refrigerated container heat dissipation port;

[0015] The air precooling system is responsible for cooling normal temperature air to low temperature air through a heat exchanger;

[0016] The ventilation pipeline system sends the cooled low temperature air into the specific position of the refrigerated cargo hold where the cold boxes are located; based on the CFD simulation results, the ventilation pipeline system adopts the form of a main pipeline + multi-layer branch pipelines, and the air outlet position is aligned with the heat dissipation port; the number of vertical ventilation pipe air outlets is increased; multi-layer branch pipelines are arranged, and each container heat dissipation unit corresponds to an air outlet one by one; an electromagnetic control valve is installed at the air outlet to achieve point-to-point ventilation adjustment of the refrigerated container heat dissipation points;

[0017] The central control system is responsible for simulating and calculating the temperature field distribution in the refrigerated cargo hold and the cold box quantity and position information according to the collected temperature monitoring data, and formulating and sending specific instructions: controlling the opening, closing, air blowing volume size of each air outlet, and the rotational speed and power of the ventilation fan.

[0018] As an optimization: The ventilation pipeline system is divided into a main pipeline and each branch pipeline. An air outlet is arranged at the end of the branch pipeline, and an electromagnetic control valve and a temperature probe are installed. The electromagnetic control valve and the temperature probe (air outlet) correspond one by one to the maximum number of refrigerated containers that can be loaded in the cargo hold. The central processor can judge whether a refrigerated container is loaded at a certain position according to the temperature change detected by the temperature probe. When there is no refrigerated container loaded at a certain position, the ventilation at this position can be closed or reduced. Finally, the central processor can adjust the power of the ventilation fan according to the number of electromagnetic control valves (air outlets) and the magnitude of the air output volume, so as to realize the real-time adjustment of the fan power along with the cargo hold temperature and the amount of loaded containers, reduce the excessive ventilation of the fan, and achieve the purpose of energy conservation.

[0019] As an optimization: A temperature sensor probe is arranged on the side of the heat dissipation unit. The ventilation opening is designed to be normally closed under normal conditions. Only when the temperature probe detects abnormal temperature, the ventilation opening will start to ventilate. When the temperature sensor probe detects a relatively high temperature field at this place, it transmits the detected temperature information to the central processor. The central processor can remotely control the electromagnetic valve according to the detected temperature level and adjust the ventilation magnitude at this position. The central processor can compare the temperature information at this place with the ambient temperature according to the detected cargo hold temperature information. When the detected temperature at this position is less than 30°C, or higher than the ambient temperature but the deviation is less than 10°C, the ventilation at this position can be closed.

[0020] As an optimization: The air outlet and the temperature probe are arranged in one-to-one correspondence with the maximum number of refrigerated container positions that can be loaded. After obtaining the temperature detection information and the air outlet switch signal, the central processor can conduct comprehensive analysis and judgment based on relevant information. For example, if the temperature does not rise at the heat dissipation unit corresponding to a certain position within half an hour after the air outlet is closed, it can be considered that there is no refrigerated container loaded at this position. That is to say, the central processor can comprehensively judge whether there is a refrigerated container at a certain refrigerated container position and the specific position information of the cold box by controlling the opening and closing of the air outlet, the magnitude of the ventilation volume, and combining the temperature change situation. Furthermore, it can monitor the number, position of the refrigerated containers in the cargo hold and the temperature information of the heat dissipation outlets of each cold box in real time. Correspondingly, it can also obtain the distribution of the cold boxes and the temperature distribution in the cargo hold. The central processor can adjust the air output volume of each air outlet in real time based on this information, and always keep the temperature at a certain position matching the required ventilation volume. The ventilation volume changes with the change in the number of cold boxes in the cargo hold. As the cold boxes are loaded at different positions in the cargo hold, the corresponding air outlets can be opened or closed. The ventilation magnitude is adjusted according to the temperature level in the cargo hold, and always keeps the temperature at this place matching the required ventilation volume.

[0021] As an optimization: The central processor adjusts the rotation speed and power of the ventilation fan on the main pipeline in real time by summarizing the air volume information of all air outlets, so as to realize the precise utilization of energy and the real-time management of power consumption. At the same time, in order to improve the adjustment accuracy of the ventilation volume of the fan, the motor of the ventilation fan adopts a variable frequency motor.

[0022] As an optimization: To more effectively improve the cooling effect of the refrigerated cargo hold, cold air is used for the air in the refrigerated cargo hold ventilation. The cold air comes from the air heat exchanger and the cold air delivery pipeline system; by using this system, the air for ventilation can be pre-cooled through the low temperature of ammonia fuel; the normal temperature air is cooled to low temperature air by the heat exchanger, and the air below the ambient temperature is used to cool the refrigerated cargo hold; this solution has a more obvious cooling effect, uses less ventilation volume, and effectively saves the power consumption of the ventilation fan.

[0023] Beneficial effects: The present invention reasonably utilizes the heat exchange process in which ammonia fuel absorbs energy during the gasification process, optimizes the form of the ventilation duct, and achieves the best cooling effect of the refrigerated cargo hold. Brief description of the drawings

[0024] Figure 1 is a schematic diagram of the ventilation and temperature distribution of the refrigerated cargo hold of the present invention;

[0025] Figure 2 is a schematic diagram of the comparison before and after the structure of the ventilation duct of the present invention;

[0026] Figure 3 is a schematic diagram of the process of real-time monitoring of the outlet temperature of the present invention;

[0027] Figure 4 is a schematic diagram of the structure of the spiral air duct of the present invention;

[0028] Figure 5 is a schematic diagram of the structure of the air damper of the present invention;

[0029] Figure 6 is a schematic diagram of the structure of the double-layer tube heat exchanger of the present invention;

[0030] Figure 7 is a schematic diagram of the structure of the ventilation air device of the cold cargo hold of the present invention;

[0031] Figure 8 is a schematic diagram of the structure of the electromagnetic closing device at the air outlet of the present invention. Detailed implementation manners

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below, so that those skilled in the art can better understand the advantages and features of the present invention, and thus make a clearer definition of the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the protection scope of the present invention. Embodiment

[0033] The main objectives achieved by the present invention are as follows: Assuming a certain number of reefer containers in the cargo hold, under the condition of ensuring the normal operating temperature of the reefer containers (45 degrees required by the classification society rules), the power consumption of the ventilation fans is minimized as much as possible.

[0034] Main implementation methods:

[0035] The implementation idea and method of the present invention are as follows: Reasonably utilize the heat exchange process in which ammonia fuel absorbs energy during the gasification process, optimize the form of the ventilation duct, and expect to achieve the best cooling effect for the refrigerated cargo hold.

[0036] First, during the design of a new ship: Based on the layout plan of the ventilation ducts in the existing container refrigerated cargo hold, the main reason for the increase in the temperature of the refrigerated cargo hold is the heat dissipated by the refrigeration of the reefer containers. Its characteristics can be modeled for the refrigerated cargo hold through CFD. Under the assumed boundary conditions, the ventilation and temperature distribution diagrams of the refrigerated cargo hold are obtained as Figure 1 shown.

[0037] Through the analysis of the CFD simulation calculations of the present invention, it is found that the temperature field distribution law of the refrigerated cargo hold is as follows:

[0038] 1. Temperature field in the refrigerated cargo hold: The temperature at the heat dissipation outlet (refrigeration unit) of the reefer container is higher than that in other areas.

[0039] 2. The closer the outlet position of the ventilation duct is to the heat dissipation outlet of the refrigerated container, the better the heat dissipation effect on the reefer container. The wind direction of the outlet of the ventilation duct and the wind direction of the heat dissipation outlet of the condenser have a great influence on the temperature at the end of the reefer container. Therefore, it is very important to reasonably optimize the position and air outlet direction of the ventilation duct and the outlet to the temperature at the heat dissipation outlet of the reefer container.

[0040] 3. Based on the original ventilation design of the container ship, there is only one air inlet at the bottom end ventilation duct, and the temperature field distribution of the entire cargo hold is uneven. The temperature field in the upper part of the refrigerated cargo hold is higher than that in the bottom part of the refrigerated cargo hold.

[0041] 4. The ambient air temperature also directly affects the ventilation effect. The higher the ambient air temperature of the refrigerated cargo hold, the greater the required ventilation volume. To reduce the required ventilation volume and energy consumption, it is necessary to use a lower ambient air temperature. (That is, the heat dissipated by the cooler is taken away through ventilation. The lower the air temperature used for ventilation, the better the heat dissipation effect and the less energy consumed).

[0042] The countermeasures implemented by the present invention are as follows:

[0043] A. For the first, second, and third points of the above CFD simulation conclusions:

[0044] 1. Optimize the structure form of the ventilation duct, and adjust it from the original single ventilation main pipe to the form of main pipe + multiple branch pipes, specifically as Figure 2 shown.

[0045] ①Align the air outlet position with the heat dissipation outlet as much as possible. ②Increase the number of air outlet of the vertical ventilation pipe. ③Arrange branch pipelines, and each container heat dissipation unit corresponds to an air outlet. And through the switch regulating valve, point-to-point control of each refrigerated container can be realized according to the temperature detection result.

[0046] 2. As Figure 3 shown, heat induction probes are arranged at the heat dissipation outlets of each layer to monitor the electromagnetic regulating valve in real time. The wireless signal can be transmitted to the stowage computer, and the analysis and processing system of this computer can analyze and judge the number of cold containers in the refrigerated cargo hold based on the position and temperature information of the temperature probe signal, and can simulate the temperature field distribution in the refrigerated cargo hold. Specifically: If the temperature detected by the temperature probe at a certain bin position in the refrigerated cargo hold is the cargo hold temperature, it means that there is no cold container at this bin position. At this time, the central processing system can send a wireless control signal to close the air outlet corresponding to this bin position to reduce the air volume consumption at this bin position.

[0047] 3. To reduce the cold air loss in the ventilation pipeline during the transmission of cold air, the ventilation pipeline is changed from a common steel pipeline to a spiral air duct, as Figure 4 shown. The outer layer is wrapped with heat-insulating rubber to reduce cold air loss.

[0048] 4. The branch pipeline is provided with a damper, as Figure 5 shown. When a certain branch pipeline needs to be repaired or out of use, the ventilation damper on this branch can be closed.

[0049] B. Regarding the fourth point of the above CFD simulation conclusion:

[0050] 1. Combining the characteristics of ammonia-powered ships, the heat absorption characteristic of the ammonia fuel gasification process can be utilized. Through the heat exchanger, the air is pre-cooled into low-temperature air. After pressurization, it is combined with the air at the air inlet to form lower-temperature air, which plays a role in quickly reducing the temperature of the refrigerated cargo hold (by using ventilation air below normal temperature, reducing the required ventilation volume, reducing the power of the fan, and reducing energy consumption). Considering the toxicity of ammonia fuel and avoiding the leakage of ammonia gas during the heat exchange process, a safer double-layer tube heat exchanger is adopted, as Figure 6 shown.

[0051] 2. When the ship sails using ammonia fuel, the ventilation air in the refrigerated cargo hold is mainly low-temperature air cooled by ammonia fuel. At this time, the cargo hold environment temperature is significantly reduced, and the cargo hold fan can reduce operation or stop, playing a role in saving energy of the fan. When the ship is stopped, ventilation is relied on traditional fans, and the fans play a backup or supplementary role in this invention, as Figure 7 shown.

[0052] 3. The vent is designed to be normally closed under normal conditions. Only when the temperature probe detects abnormal temperature will the vent start to ventilate. According to the monitoring results of the temperature probes in the cargo hold, when the temperature distribution in the cold cargo hold is uneven or there are no reefer containers loaded on some slots, the central processor remotely and centrally controls the solenoid control valves arranged at the end of the air outlet to adjust the air volume at each slot, as Figure 8 shown. For example, when there is no reefer container loaded on a certain slot, the central processor can send a signal to close the ventilation at that slot. When the temperature at a certain slot is lower than the working temperature of the cargo hold, after receiving the temperature signal, the central processor can send an instruction to reduce the air volume at that slot. In case of an emergency, when there is a power outage and the remote control fails, local manual control can be used for emergency.

[0053] To facilitate the precise control of the fan, the motor of the ventilation fan uses a variable-frequency fan, which can be precisely controlled to start, stop or change the speed according to the instructions of the computer control center, and the air volume can be adjusted according to the temperature of the cold cargo hold.

Claims

1. A ventilation energy-saving system for the refrigerated cargo hold of an ammonia-powered container ship, characterized in that: The described ventilation energy-saving system is composed of a temperature monitoring system, an air pre-cooling system, a ventilation pipeline system, and a central control system; among which: The described temperature monitoring system is composed of temperature sensing probes arranged at the end of the heat dissipation outlet of the refrigerated container, and is mainly responsible for real-time monitoring of the temperature information near the heat dissipation outlet of the container; The described air pre-cooling system is responsible for cooling normal temperature air into low temperature air through a heat exchanger; The described ventilation pipeline system sends the cooled low temperature air into the position of the specific refrigerated container in the refrigerated cargo hold; based on the CFD simulation results, the ventilation pipeline system adopts the form of a main pipeline + multi-layer branch pipelines, and the air outlet position is aligned with the heat dissipation outlet; the number of vertical ventilation pipe air outlets is increased; multi-layer branch pipelines are arranged, and each container heat dissipation unit corresponds to an air outlet one by one; an electromagnetic control valve is installed at the air outlet, realizing point-to-point ventilation adjustment of the heat dissipation points of the refrigerated containers; The described central control system is responsible for simulating and calculating the temperature field distribution in the refrigerated cargo hold and the position information of the refrigerated containers according to the collected temperature monitoring data, and formulating and sending specific instructions: controlling the opening, closing, air blowing volume, and the rotational speed and power of the ventilation fan at each air outlet; The air outlets and temperature probes are arranged in one-to-one correspondence with the maximum number of refrigerated container positions that can be loaded; after obtaining the temperature detection information and the air outlet switch signal, the central processor conducts comprehensive analysis and judgment based on relevant information: within half an hour after the air outlet is closed, if there is no temperature rise at the heat dissipation unit of the corresponding container position, it is considered that there is no refrigerated container loaded at the container position; that is: the central processor comprehensively judges whether there is a refrigerated container at the refrigerated container position and the specific position information of the refrigerated container by controlling the opening and closing of the air outlet, the air volume, and combining the temperature change situation, and then real-time monitors the number, position of the refrigerated containers in the cargo hold and the temperature information of the heat dissipation outlets of each refrigerated container; correspondingly, the distribution of the refrigerated containers in the cargo hold and the temperature distribution situation are also obtained; the central processor adjusts the air volume of each air outlet in real time according to this information, always keeping the temperature at a certain container position matched with the required ventilation volume; the ventilation volume changes with the change in the number of refrigerated containers in the cargo hold; as the loading position of the refrigerated containers in the cargo hold is different, the air outlets at the corresponding positions are opened and closed; the ventilation size is adjusted according to the temperature in the cargo hold, always keeping the temperature matched with the required ventilation volume.

2. The ventilation energy-saving system for the refrigerated cargo hold of an ammonia-powered container ship according to claim 1, characterized in that: The described ventilation pipeline system is divided into a main pipeline and each branch pipeline. The end of the described branch pipeline is provided with an air outlet, and an electromagnetic control valve and a temperature probe are installed; the electromagnetic control valve and the temperature probe correspond to the maximum number of refrigerated containers that can be loaded in the cargo hold one by one; the central processor judges whether there is a refrigerated container loaded at the container position according to the temperature change detected by the temperature probe; when there is no refrigerated container loaded at a certain container position, the ventilation at the container position is closed or reduced; finally, the central processor adjusts the power of the ventilation fan according to the number of electromagnetic control valves and the air volume.

3. The ventilation energy-saving system for the refrigerated cargo hold of an ammonia-powered container ship according to claim 1, wherein: A temperature sensor is arranged on the side of the heat dissipation unit. The ventilation opening is designed to be normally closed under normal conditions. Only when the temperature sensor detects abnormal temperature will the ventilation opening start to ventilate. When the temperature sensor detects a relatively high temperature field at a certain place, it transmits the detected temperature information to the central processing unit. The central processing unit remotely controls the solenoid valve according to the detected temperature level to adjust the ventilation volume at the container position. The central processing unit compares the temperature information with the ambient temperature according to the detected temperature information of the cargo hold. When the detected temperature at the container position is less than 30°C, or higher than the ambient temperature but the deviation is less than 10°C, the ventilation at the container position is closed.

4. The ventilation energy-saving system for the refrigerated cargo hold of an ammonia-powered container ship according to claim 1, characterized in that: The central processing unit adjusts the rotation speed and power of the ventilation fan on the main pipeline in real time by summarizing the air volume information of all air outlets; at the same time, the motor of the ventilation fan is a variable frequency motor.

5. The ventilation energy-saving system for the refrigerated cargo hold of an ammonia-powered container ship according to claim 1, characterized in that: The air used for ventilation in the refrigerated cargo hold is cold air, and the cold air comes from the air heat exchanger and the cold air delivery pipeline system; the cold air delivery pipeline system is used to pre-cool the air used for ventilation through the low temperature of ammonia fuel; the normal temperature air is cooled to low temperature air by the heat exchanger, and the refrigerated cargo hold is cooled by the air below the ambient temperature.

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