Ammonia absorption refrigeration system and method driven by waste heat of ship

Abstract

A marine waste heat-driven ammonia absorption refrigeration system and method belong to the field of marine energy conservation and absorption refrigeration technology. The system uses the low-temperature waste heat of the cylinder liner water (65℃-95℃) of the marine diesel engine as the driving heat source, employing a novel ammonia-salt working fluid pair. It forms an absorption refrigeration circuit consisting of a generator, condenser, throttle valve, evaporator, absorber, solution pump, and solution heat exchanger, and is equipped with a waste heat supply circuit and a cooling capacity output circuit, simultaneously providing cooling for the ship's air conditioning and refrigeration systems. The salt solute used in this invention has high solubility in ammonia and is non-volatile. The ammonia gas obtained from the solution heating and desorption is of high purity, eliminating the need for a distillation device. The system is compact, small in size, and low in cost, making it suitable for the space-constrained environment of ships. By replacing electric compression refrigeration with absorption refrigeration and using environmentally friendly ammonia refrigerant instead of high GWP refrigerants, it significantly reduces marine fuel consumption and carbon emissions. The system operates safely and stably, with high energy efficiency and waste heat utilization, meeting the needs of maritime emission reduction and ship refrigeration.

Description

Technical Field

[0001] This invention relates to a marine waste heat-driven ammonia absorption refrigeration system and method, which belongs to the field of marine energy-saving technology and absorption refrigeration. Background Technology

[0002] Marine diesel engines generate a large amount of low-temperature waste heat from cylinder liner cooling water during operation. This waste heat, typically ranging from 65°C to 95°C, is of low grade and currently has a low recovery rate, with most cases resulting in direct emission and energy waste. Under the increasingly stringent emission reduction regulations of the International Maritime Organization, efficiently recovering marine low-temperature waste heat and converting it into energy for refrigeration is a crucial direction for improving ship energy efficiency and reducing fuel consumption and carbon emissions.

[0003] Existing marine refrigeration systems mostly employ electrically driven compression refrigeration, consuming significant amounts of electricity from the ship's electrical grid and indirectly increasing fuel consumption and carbon emissions. Furthermore, these systems often use hydrofluorocarbon (HFC) refrigerants with high global warming potential (GWP), facing a global phase-out trend. Although the industry has experimented with natural refrigerants such as propane and CO2, issues remain regarding safety, system compatibility, and low energy efficiency in the confined, enclosed, and vibrating environment of ships.

[0004] Ammonia absorption refrigeration can directly utilize low-temperature waste heat for driving and can achieve refrigeration below 0°C. Ammonia, as a natural working fluid, has excellent environmental friendliness. However, in traditional ammonia-water absorption refrigeration systems, both water and ammonia vaporize during heating. To ensure ammonia purity, a complex distillation device must be installed, resulting in large equipment size, high cost, and complex structure, making it difficult to meet the space-constrained requirements of ships. Furthermore, the toxicity and flammability of ammonia pose safety hazards in the confined spaces of ships, and the large ammonia charge in traditional systems further increases the risk. Summary of the Invention

[0005] This invention aims to solve the problems of high energy consumption, non-environmentally friendly refrigerants, complex distillation devices required for traditional ammonia absorption refrigeration, large system size, and insufficient safety in existing marine refrigeration systems. It provides a marine waste heat-driven ammonia absorption refrigeration system and method, which achieves compact structure, no need for distillation, safety and reliability, and efficient utilization of engine low-temperature waste heat for refrigeration.

[0006] This invention employs an ammonia-salt working fluid pair, using liquid ammonia as the refrigerant and a highly soluble, non-volatile salt as the absorbent dissolved in the liquid ammonia. Upon heating, only ammonia gas is released, resulting in high gas phase purity and fundamentally eliminating the need for a distillation unit. The system utilizes the waste heat from the 65℃-95℃ cylinder liner cooling water of the marine diesel engine as the driving heat source, forming a closed-loop absorption refrigeration cycle. Simultaneously, it outputs cooling capacity to marine air conditioning and refrigeration users, replacing traditional electric compression refrigeration and significantly improving marine energy efficiency.

[0007] A marine waste heat-driven ammonia absorption refrigeration system includes a waste heat supply circuit, an absorption refrigeration circuit, and a cooling capacity distribution circuit, all of which are connected by pipes. The absorption refrigeration circuit includes a generator, a condenser, a throttling valve, an evaporator, an absorber, a solution throttling valve, and a solution heat exchanger, which are connected to the pipeline in sequence. The generator heat exchange side is connected to the waste heat supply circuit, including a waste heat inlet and a waste heat outlet; one end of the generator is connected to the condenser to transport the evaporated refrigerant to the condenser; the other end is connected to the solution heat exchanger so that the dilute solution recovers heat through the solution heat exchanger and then enters the absorber through the solution throttling valve. The condenser is a water-cooled condenser that uses marine cooling water; the liquid refrigerant produced by condensation enters the evaporator. The heat exchange surface of the evaporator is connected to the cooling capacity distribution loop, which includes an intermediate refrigerant pump, a regulating valve, and a cooling capacity demand side; the refrigerant after evaporation and heat absorption enters the absorber; The absorber is equipped with a solution pump at its outlet to pump the concentrated solution into the solution heat exchanger; the preheated concentrated solution is then returned to the generator. The refrigerant is liquid ammonia, and the absorbent is an ammonia-salt solution; The pipeline is a ship-specific pipeline.

[0008] Furthermore, the waste heat supply circuit is connected to the ship's cylinder liner cooling water.

[0009] Furthermore, the waste heat supply circuit is connected to the engine exhaust system.

[0010] Furthermore, the cooling demand side of the cooling distribution loop consists of an air conditioning branch heat exchanger and a refrigeration branch heat exchanger, and the regulating valve is an air conditioning branch regulating valve and a refrigeration branch regulating valve.

[0011] Furthermore, the absorbent is an ammonia-lithium nitrate solution with a mass fraction of 50%-65%.

[0012] Furthermore, temperature sensors are installed at the waste heat inlet, in the generator, at the evaporator outlet, and at the cooling demand side; pressure sensors are installed in the absorber; and frequency controllers are installed on the solution pump and the intermediate refrigerant pump.

[0013] Furthermore, a method for a marine waste heat-driven ammonia absorption refrigeration system includes the following steps: S1. System Startup and Heat Source Connection The system is ready to start when the ship's engine is running and outputting a stable 65℃-95℃ cylinder liner cooling water waste heat.

[0014] The engine waste heat supply circuit is activated, and the solution pump and intermediate refrigerant pump are started simultaneously, putting the system into a pre-operation state.

[0015] S2, Establishment of absorption refrigeration cycle Inside the generator, the ammonia-salt solution is heated by residual heat, and the liquid ammonia vaporizes into high-purity ammonia gas. The ammonia gas is then cooled by the ship's cooling water in the condenser, condensing into high-pressure liquid ammonia.

[0016] Liquid ammonia is throttled and depressurized by a throttling valve before entering the evaporator. Under low pressure, it rapidly evaporates and absorbs heat, cooling the refrigerant in the cooling output circuit and achieving continuous refrigeration.

[0017] The evaporated low-pressure ammonia gas enters the absorber and is fully absorbed by the dilute solution from the generator, which has been cooled by the solution heat exchanger, to reform a high-concentration ammonia-salt solution, thus completing the absorption process.

[0018] The concentrated solution is pressurized by a solution pump, preheated by a solution heat exchanger, and then sent to the generator, where it is heated and decomposed again, forming a continuous closed-loop absorption refrigeration cycle that continuously converts the engine's waste heat into cooling capacity.

[0019] S3, Cooling Capacity Output and Distribution The cooling capacity generated by the evaporator is transferred to the refrigerant through the heat exchange surface. The low-temperature refrigerant is then transported along the pipeline to the cooling demand side by the intermediate refrigerant pump.

[0020] S4. When the ship's engine stops and there is no waste heat available, or when the ship does not require refrigeration, the system sequentially shuts down the solution pump, the intermediate refrigerant pump, and closes the engine waste heat supply circuit valve, and the system safely shuts down according to the procedure.

[0021] Furthermore, In step S1, the engine waste heat supply circuit is turned on, and cylinder liner cooling water is used to enter the generator through the waste heat inlet to provide a driving heat source for the system.

[0022] In step S2, inside the generator, the ammonia-lithium nitrate solution is heated by cylinder liner cooling water.

[0023] In step S3, the cooling capacity generated by the evaporator is transferred to the refrigerant through the heat exchange surface. The low-temperature refrigerant is then transported along the pipeline to the air conditioning branch heat exchanger and the refrigeration branch heat exchanger, driven by the intermediate refrigerant pump.

[0024] The system automatically adjusts the opening of the air conditioning branch regulating valve and the refrigeration branch regulating valve according to the air conditioning set temperature and the refrigeration set temperature, and distributes the refrigerant flow of the two circuits to maintain the air-conditioned area at the set cooling temperature and the refrigeration area to reach the low temperature storage requirement of about -20℃, so as to realize dual temperature zone and on-demand cooling.

[0025] In step S4, during system operation, the controller collects parameters such as waste heat inlet temperature, generator solution temperature, evaporator outlet temperature, absorber pressure, and air conditioning and refrigeration branch temperature in real time. Based on the preset control logic, it automatically adjusts the solution pump frequency, intermediate refrigerant pump frequency, and the opening of each branch regulating valve to ensure that the system maintains efficient and stable operation under changing heat source and changing load conditions.

[0026] Compared with the prior art, the present invention has the following advantages: it adopts a novel anhydrous ammonia-salt working fluid pair, and only high-purity ammonia gas is released upon heating. It does not require a distillation device, and the system has a compact structure, small size, low cost, and is suitable for the space-constrained environment of ships.

[0027] It directly utilizes the low-temperature waste heat of the cylinder liner water (65℃-95℃) for driving, requiring only a small amount of electricity to drive the pumps and valves, replacing traditional electric compression refrigeration, and significantly reducing marine fuel consumption and carbon emissions. Using ammonia as the refrigerant, its GWP is approximately 0, demonstrating excellent environmental performance and meeting international maritime emission reduction requirements.

[0028] Anhydrous ammonia-salt working fluid pairs can reduce ammonia charging volume and improve the safety of use in confined spaces on ships. They can simultaneously meet the cooling needs of both air conditioning and refrigeration / refrigeration zones on ships, offering flexible cooling capacity distribution, high energy efficiency, and high waste heat utilization. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 Schematic diagram of a marine waste heat-driven absorption refrigeration system Figure 2 Schematic diagram of a marine waste heat-driven absorption refrigeration system with added sensors Figure 3 Driving heat source temperature - cooling temperature matching relationship table In the diagram: 1. Waste heat inlet; 1a. Waste heat inlet temperature sensor; 2. Generator; 21. Generator temperature sensor; 3. Condenser; 4. Throttling valve; 5. Evaporator; 51. Evaporator outlet temperature sensor; 6. Absorber; 62. Absorber pressure sensor; 7. Solution pump; 73. Solution pump frequency controller; 8. Solution heat exchanger; 9. Solution throttling valve; 10. Waste heat outlet; 11. Intermediate refrigerant pump; 113. Intermediate refrigerant pump frequency controller; 12. Air conditioning branch regulating valve; 13. Air conditioning branch heat exchanger; 131. Air conditioning branch temperature sensor; 14. Refrigeration branch regulating valve; 15. Refrigeration branch heat exchanger; 151. Refrigeration branch temperature sensor; 16. Marine cooling water. Detailed Implementation

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0035] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" are generally based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0036] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0037] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0038] Unless otherwise specified in this application, the definitions of concentration are as follows: concentrated and dilute refer to the concentration of ammonia. After the absorber absorbs ammonia vapor, the concentration of ammonia in the solution increases, becoming a concentrated solution; after the generator heats and vaporizes ammonia gas, the concentration of ammonia in the solution decreases, becoming a dilute solution.

[0039] The present invention provides a marine waste heat driven absorption refrigeration system, including an absorption refrigeration circuit, an engine waste heat supply circuit, and a cooling output circuit.

[0040] Absorption refrigeration circuits are used to complete the heat absorption, cooling, and heat release cycle of the working fluid, realizing the conversion of thermal energy into cold energy.

[0041] The engine waste heat supply circuit is used to recover the waste heat generated by the marine diesel engine and provide a driving heat source for the system. It preferentially uses cylinder liner cooling water with a temperature of 65℃-95℃, and can also be extended to recover and utilize engine exhaust waste heat.

[0042] The cooling output circuit is used to transport and distribute the cooling generated by the system to different cooling demand points on the ship, including ship air conditioning, food freezing and refrigeration equipment, etc.

[0043] The engine waste heat supply circuit is connected to the marine diesel engine cylinder liner cooling water system to deliver low-temperature waste heat at 65℃-95℃. This temperature range closely matches the thermodynamic characteristics of the working fluid used in this invention, allowing the system to stably complete the refrigeration cycle without the need for a distillation unit. The engine waste heat supply circuit can also be connected to the engine exhaust system, recovering higher-grade exhaust waste heat through heat exchange devices such as exhaust gas boilers, serving as the system's main or auxiliary heat source, further improving the overall utilization rate of marine waste heat.

[0044] Absorption refrigeration circuits are installed in the ship's engine room or dedicated refrigeration equipment room, featuring a compact structure that facilitates centralized management and maintenance. The cooling output circuits are laid out according to the actual locations of the ship's air-conditioned and refrigerated areas, with cooling supply pipelines extending to each cooling terminal to achieve long-distance, stable cooling.

[0045] Each circuit is connected by pressure-resistant and corrosion-resistant marine-specific pipelines. The pipelines are equipped with regulating valves, shut-off valves, temperature sensors, pressure sensors, and flow sensors, which can automatically control the system's start-up, operation, regulation, and shutdown based on parameters such as heat source temperature, waste heat flow, and user-side cooling load, achieving dynamic matching between waste heat utilization and cooling output.

[0046] The absorption refrigeration circuit includes a generator 2, a condenser 3, a throttling valve 4, an evaporator 5, an absorber 6, a solution pump 7, a solution heat exchanger 8, and a solution throttling valve 9. These devices are sequentially connected to an ammonia vapor pipeline via a solution pipeline, forming a closed-loop circuit.

[0047] The solution pump 7 is located at the outlet of the absorber 6 and is used to pressurize and transport the concentrated solution after ammonia absorption. The solution heat exchanger 8 is located between the absorber 6 and the generator and is used to preheat the concentrated solution entering the generator and recover the heat of the dilute solution flowing out of the generator to improve the overall energy efficiency of the system. The solution throttling valve 9 is located between the cold side outlet of the solution heat exchanger 8 and the absorber 6 and is used to send the cooled and depressurized dilute solution into the absorber 6 to complete the solution circulation.

[0048] The engine waste heat supply circuit includes a waste heat inlet 1 and a waste heat outlet 10, which are connected to the heat exchange side of the generator 2 through a heat transfer pipeline to form an independent waste heat transport cycle. The cylinder liner water of the marine diesel engine enters the generator 2 from the waste heat inlet 1, exchanges heat with the internal ammonia-salt working fluid, and after releasing heat, flows back to the engine cylinder liner water system from the waste heat outlet 10, realizing the continuous recovery and utilization of waste heat.

[0049] The cooling output circuit includes an intermediate refrigerant pump 11, an air conditioning branch regulating valve 12, an air conditioning branch heat exchanger 13, a refrigeration branch regulating valve 14, and a refrigeration branch heat exchanger 15. This circuit is connected to the heat exchange side of the evaporator 5 through a refrigerant pipeline, forming a secondary cooling cycle. This safely and stably delivers the cooling capacity generated by the evaporator 5 to different cooling terminals, preventing ammonia refrigerant from directly entering personnel activity areas and food storage areas, thus improving system operational safety.

[0050] The cooling output circuit can simultaneously serve at least two user terminals with different temperature requirements: First, the ship's air conditioning system is designed to provide a cooling temperature of approximately 5°C, which meets the air conditioning and cooling needs of the crew's living quarters and public areas. Secondly, the ship's food freezing and refrigeration system is designed to have a cooling temperature as low as -20℃, meeting the needs of food freezing and refrigeration storage.

[0051] The system dynamically adjusts the refrigerant flow rate of the two branches through the air conditioning branch regulating valve 12 and the refrigeration branch regulating valve 14, in conjunction with the real-time signals collected by the temperature sensor and the flow sensor, so as to realize the on-demand distribution and precise control of cooling capacity and ensure that different user terminals can stably reach the set temperature.

[0052] In one embodiment of the present invention, the system uses a homogeneous solution composed of liquid ammonia and lithium nitrate as the working fluid pair, wherein the mass fraction of lithium nitrate is 50%-65%. Under heating conditions, this working fluid pair only releases high-purity ammonia gas, and the salt absorbent does not volatilize or precipitate with the ammonia gas. Therefore, high-purity ammonia refrigerant can be obtained without a distillation device.

[0053] The system uses a 50% ethylene glycol aqueous solution as a refrigerant. It has a low freezing point, good low-temperature fluidity, stable chemical properties, and weak corrosiveness to ship pipelines and equipment. It is suitable for the low-temperature refrigeration environment of ships and can simultaneously meet the cooling needs of air conditioning and refrigeration dual-temperature zones.

[0054] The selection criteria for the working medium to absorb salts are as follows: It has high solubility in liquid ammonia and can form a stable homogeneous solution with liquid ammonia; It does not decompose, volatilize, or undergo irreversible chemical reactions with ammonia within the system's operating temperature range; It has good thermal stability, low toxicity, and is suitable for use in confined spaces on ships.

[0055] This invention preferably uses lithium nitrate as the absorbent because it has high solubility in liquid ammonia, good solution stability, moderate cost, and is easy to apply in engineering. Alternative salt absorbents include inorganic salts soluble in liquid ammonia such as thiocyanates, halides, and nitrates.

[0056] This system employs anhydrous ammonia-salt working fluid pair, using liquid ammonia as the refrigerant and a high-boiling-point salt as the absorbent. Since the boiling point of the salt absorbent is much higher than that of ammonia, only the ammonia vaporizes and precipitates when heated in generator 2, while the salt absorbent remains in the liquid phase. The resulting gas phase is high-purity ammonia gas. Unlike traditional ammonia-water working fluid pairs, there is no need for a distillation column to separate water vapor, fundamentally simplifying the system structure, reducing equipment size, and lowering manufacturing costs. This makes it more suitable for the limited space and complex vibration environment of ships. Simultaneously, the anhydrous ammonia-salt working fluid pair reduces the amount of ammonia charged into the system, decreasing the overall risk of leakage and improving the safety of ship operation.

[0057] By matching and optimizing the thermodynamic properties of the ammonia-salt working fluid, this system can operate stably and efficiently under low-temperature waste heat conditions ranging from 65℃ to 95℃, realizing the conversion of low-grade waste heat into effective cooling capacity. The system can automatically adjust the solution circulation rate, refrigerant flow rate, and valve opening of each branch according to real-time changes in engine waste heat temperature, air conditioning load, and refrigeration load, ensuring that the system always operates within a range close to its optimal coefficient of performance, achieving a highly efficient match between waste heat resources and refrigeration needs.

[0058] The working process of the refrigerant in the cooling output circuit includes the following stages: 1. Cooling stage: The refrigerant exchanges heat with the ammonia refrigerant in the evaporator 5. The ammonia evaporates and absorbs heat, which lowers the temperature of the refrigerant, forming a low-temperature refrigerant. 2. Delivery and circulation stage: Driven by the intermediate refrigerant pump 11, the low-temperature refrigerant enters the air conditioning branch and the refrigeration branch respectively, and exchanges heat with the air conditioning terminal and refrigeration equipment to absorb heat to meet the user's cooling needs. 3. Recooling stage: The refrigerant whose temperature rises after heat exchange flows back to evaporator 5, is cooled again by ammonia refrigerant, and enters the next cycle, realizing continuous output and distribution of cooling capacity.

[0059] This invention establishes a matching relationship between the driving heat source temperature (generating temperature) and the cooling temperature (evaporating temperature) by studying the thermodynamic properties of the working fluid pair, as follows: Figure 3 As shown, the system can be configured or controlled to adjust its operating state according to the available engine waste heat temperature and the target cooling demand, so that the system always operates in the range closest to the optimal performance coefficient, thereby achieving efficient matching between waste heat resources and cooling demand.

[0060] The operation method of the above-mentioned marine waste heat driven ammonia absorption refrigeration system includes the following steps: S1. System Startup and Heat Source Connection The system is ready to start when the ship's engine is running and outputting a stable 65℃-95℃ cylinder liner cooling water waste heat.

[0061] Open the corresponding valves in the engine waste heat supply circuit, and the cylinder liner cooling water enters the generator 2 through the waste heat inlet 1 to provide a driving heat source for the system. At the same time, start the solution pump 7 and the intermediate refrigerant pump 11 to establish the working fluid circulation and the refrigerant circulation, and the system enters the pre-operation state.

[0062] S2, Establishment of absorption refrigeration cycle Inside generator 2, the concentrated ammonia-salt solution is heated by cylinder liner cooling water, and the liquid ammonia vaporizes into high-purity ammonia gas. Since the salt absorbent is non-volatile, the ammonia gas can directly enter condenser 3 without distillation. Inside condenser 3, the ammonia gas is cooled by marine cooling water 16 and condensed into high-pressure liquid ammonia.

[0063] Liquid ammonia enters the evaporator 5 after being throttled and depressurized by the throttling valve 4. Under low pressure, it rapidly evaporates and absorbs heat, cooling the refrigerant in the cooling output circuit to achieve continuous refrigeration.

[0064] The evaporated low-pressure ammonia gas enters the absorber 6 and is fully absorbed by the dilute solution from the generator 2, which has been cooled by the solution heat exchanger 8, to reform the concentrated ammonia-salt solution and complete the absorption process.

[0065] The concentrated solution is pressurized by the solution pump 7, preheated by the solution heat exchanger 8, and then sent to the generator 2, where it is heated and decomposed again, forming a continuous closed-loop absorption refrigeration cycle that continuously converts the engine's waste heat into cooling capacity.

[0066] S3, Cooling Capacity Output and Distribution The cooling capacity generated by the evaporator 5 is transferred to the refrigerant through the heat exchange surface. Driven by the intermediate refrigerant pump 11, the low-temperature refrigerant is transported along the pipeline to the air conditioning branch heat exchanger 13 and the refrigeration branch heat exchanger 15 respectively.

[0067] The system automatically adjusts the opening of the air conditioning branch regulating valve 12 and the refrigeration branch regulating valve 14 according to the air conditioning set temperature and the refrigeration set temperature, and distributes the refrigerant flow of the two branches to maintain the air-conditioned area at the set cooling temperature and the refrigeration area to reach the low temperature storage requirement of about -20℃, so as to realize dual temperature zone and on-demand cooling.

[0068] S4, System Adjustment and Shutdown During system operation, the controller collects parameters in real time, such as the temperature of waste heat inlet 1, the solution temperature of generator 2, the outlet temperature of evaporator 5, the pressure of absorber 6, and the temperature of air conditioning and refrigeration branches. Based on the preset control logic, it automatically adjusts the frequency of solution pump 7, the frequency of intermediate refrigerant pump 11, and the opening of regulating valves in each branch, so that the system can maintain efficient and stable operation under changing heat sources and changing loads.

[0069] When the ship's engine stops and there is no waste heat available, or when the ship does not require refrigeration, the system sequentially shuts down the solution pump 7, the intermediate refrigerant pump 11, and closes the engine waste heat supply circuit valve. The system then safely shuts down according to the procedure to avoid no-load operation and energy waste.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A marine waste heat-driven ammonia absorption refrigeration system, comprising a waste heat supply circuit, an absorption refrigeration circuit, and a cooling capacity distribution circuit, all circuits being connected via pipes, characterized in that: The absorption refrigeration circuit includes a generator (2), a condenser (3), a throttle valve (4), an evaporator (5), an absorber (6), a solution throttle valve (9), and a solution heat exchanger (8) connected in sequence to the pipeline. The generator (2) is connected to the waste heat supply circuit on the heat exchange side, including a waste heat inlet (1) and a waste heat outlet (10); the outlet end of the generator (2) is connected to the condenser (3) to transport the evaporated refrigerant to the condenser (3); the condenser (3) is a water-cooled condenser, which uses marine cooling water (16) to exchange heat with the evaporated refrigerant, and condenses to produce liquid refrigerant which enters the evaporator (5). The heat exchange surface of the evaporator (5) is connected to the cold energy distribution circuit, including an intermediate refrigerant pump (11), a regulating valve, and a cold energy demand end; the refrigerant that vaporizes after absorbing heat enters the absorber (6); the dilute solution in the absorber (6) absorbs the vaporized refrigerant and becomes a concentrated solution; the concentrated solution is pumped by the solution pump (7) through the solution heat exchanger (8) and then enters the generator (2) through the concentrated solution inlet; the dilute solution that evaporates after passing through the generator (2) returns to the absorber (6) through the solution heat exchanger (8) and the solution throttle valve (9) through the dilute solution inlet. The refrigerant is liquid ammonia, and the solutions in the generator (2) and absorber (6) are ammonia-salt solutions, with the salt being lithium nitrate, sodium thiocyanate, or sodium iodide.

2. The marine waste heat-driven ammonia absorption refrigeration system as described in claim 1, characterized in that: The waste heat supply circuit is connected to the ship's cylinder liner cooling water.

3. The marine waste heat-driven ammonia absorption refrigeration system as described in claim 1, characterized in that: The waste heat supply circuit is connected to the engine exhaust system.

4. A marine waste heat-driven ammonia absorption refrigeration system as described in any one of claims 1-3, characterized in that: The cooling demand side of the cooling distribution loop is the air conditioning branch heat exchanger (13) and the refrigeration branch heat exchanger (15), and the regulating valve is the air conditioning branch regulating valve (12) and the refrigeration branch regulating valve (14).

5. A marine waste heat-driven ammonia absorption refrigeration system as described in claim 4, characterized in that: The ammonia-salt solution is an ammonia-lithium nitrate solution with a mass fraction of 50%-65%.

6. A marine waste heat-driven ammonia absorption refrigeration system as described in claim 5, characterized in that: Temperature sensors are installed at the waste heat inlet (1), in the generator (2), and at the outlet of the evaporator (5) at the cooling demand end; a pressure sensor is installed in the absorber (6); and a frequency controller is installed on the solution pump and the intermediate refrigerant pump (11).

7. A method using a marine waste heat-driven ammonia absorption refrigeration system as described in claim 6, comprising the following steps: S1. System Startup and Heat Source Connection The system is ready to start when the ship's engine is running and outputting a stable 65℃-95℃ cylinder liner cooling water waste heat. The waste heat supply circuit of the engine is turned on, and the solution pump (7) and the intermediate refrigerant pump (11) are started at the same time, and the system enters the pre-operation state; S2, Establishment of absorption refrigeration cycle Inside the generator (2), the ammonia-salt solution is heated by residual heat, and the liquid ammonia is vaporized into high-purity ammonia gas; the ammonia gas is cooled by marine cooling water (16) in the condenser (3) and condensed into high-pressure liquid ammonia. High-pressure liquid ammonia is throttled and depressurized by the throttling valve (4) and then enters the evaporator (5). Under low pressure, it rapidly evaporates and absorbs heat to cool the refrigerant in the cooling output circuit, thus achieving continuous refrigeration. The evaporated low-pressure ammonia gas enters the absorber (6) and is fully absorbed by the dilute solution from the generator (2) and cooled by the solution heat exchanger (8), thus reforming a high-concentration ammonia-salt solution and completing the absorption process. The high-concentration ammonia-salt solution is pressurized by the solution pump (7), preheated by the solution heat exchanger (8), and then sent to the generator (2) for further heating and decomposition, forming a continuous closed-loop absorption refrigeration cycle that continuously converts the engine waste heat into cooling capacity. S3, Cooling Capacity Output and Distribution The cooling capacity generated by the evaporator (5) is transferred to the refrigerant through the heat exchange surface. The low-temperature refrigerant is transported to the cooling demand end along the pipeline under the drive of the intermediate refrigerant pump (11). S4. When the ship's engine stops and there is no residual heat, or when the ship does not need to be refrigerated, the system sequentially shuts down the solution pump (7), the intermediate refrigerant pump (11), and closes the engine residual heat supply circuit valve, and the system safely shuts down according to the procedure.

8. The method for a marine waste heat-driven ammonia absorption refrigeration system as described in claim 7, characterized in that: In step S1, the engine waste heat supply circuit is turned on, and cylinder liner cooling water is used to enter the generator (2) through the waste heat inlet (1) to provide a driving heat source for the system; In step S2, inside the generator (2), the ammonia-salt solution is heated by the cylinder liner cooling water; In step S3, the cooling capacity generated by the evaporator (5) is transferred to the refrigerant through the heat exchange surface. The low-temperature refrigerant is driven by the intermediate refrigerant pump (11) and transported along the pipeline to the air conditioning branch heat exchanger (13) and the refrigeration branch heat exchanger (15). The system automatically adjusts the opening of the air conditioning branch regulating valve (12) and the refrigeration branch regulating valve (14) according to the air conditioning set temperature and the refrigeration set temperature, and distributes the refrigerant flow of the two branches to achieve dual-temperature zone and on-demand cooling. In step S4, during system operation, the controller collects the temperature of the waste heat inlet (1), the solution temperature of the generator (2), the outlet temperature of the evaporator (5), the pressure of the absorber (6), and the temperature of the air conditioning and refrigeration branches in real time, and automatically adjusts the frequency of the solution pump (7), the frequency of the intermediate refrigerant pump (11), and the opening degree of the regulating valves of each branch according to the preset control logic.

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