Water mixing type high-energy-efficiency heat exchange system and control method thereof

Abstract

The invention belongs to the technical field of energy conservation and environmental protection, and relates to a water mixing type high-energy-efficiency heat exchange system and a control method thereof.The water mixing type high-energy-efficiency heat exchange system comprises a jet type water-water heat exchanger, an absorption type heat pump circulation unit, a solution pump, a refrigerant pump, a solution heat exchanger and matched valves and pipelines; the system divides secondary side inlet water into three paths, wherein the first path is directly mixed with primary side hot water in the jet type heat exchanger to achieve near-zero temperature difference heat exchange; the second path sequentially flows through the absorber and the condenser to recover heat; and the third path flows through the evaporator as low-temperature waste heat, releases heat and then returns to the primary-side water return pipeline. Water mixing heat exchange and heat pump waste heat recovery are integrated, the energy utilization efficiency is remarkably improved, pipe network transmission and distribution energy consumption is reduced, and the system is suitable for efficient and energy-saving upgrading and transformation of a central heating system.

Description

Technical Field

[0001] This invention relates to the field of energy conservation and environmental protection technology, and in particular to a mixed-water type high-efficiency heat exchange system and its control method. Background Technology

[0002] In the field of centralized heating in northern cities, the demand for energy conservation, emission reduction, and energy efficiency upgrades is becoming increasingly urgent. Absorption heat exchangers with large temperature difference have become the mainstream technical solution for upgrading and retrofitting in this field. Its core principle is to recover waste heat by relying on high-grade heat, expanding the temperature difference between the primary water supply and outlet, and constructing a highly efficient heating mode of "small flow rate, large temperature difference." This not only ensures heating quality but also significantly improves the heat transmission capacity and efficiency of the pipeline network, reduces transmission energy consumption, and thus optimizes the system's energy utilization rate and overall life-cycle economics. Currently, this technology has been applied in several key heating cities in northern China, demonstrating significant effectiveness in reducing fossil fuel consumption and carbon and pollutant emissions.

[0003] The absorption heat exchanger unit mainly consists of a generator, condenser, evaporator, absorber, solution heat exchanger, and water-to-water plate heat exchanger. Essentially, it is an integrated device combining a type I absorption heat pump and a plate heat exchanger. High-temperature primary water first flows through the generator to heat the lithium bromide solution, then enters the water-to-water plate heat exchanger to exchange heat with part of the low-temperature secondary water, and finally enters the evaporator. The waste heat from the low-temperature primary water is absorbed by the refrigerant for further cooling. The primary water inlet uses a multi-stage heat exchange mode of "generator-driven heat exchange + direct heat exchange via water-to-water plate heat exchanger + waste heat recovery from the evaporator" to achieve large temperature difference heat exchange, effectively solving the energy waste problem caused by excessively high primary network outlet water temperature in traditional heat exchange systems.

[0004] However, absorption heat exchangers with large temperature difference still have some shortcomings in practical applications: the water-to-water plate heat exchanger built into the unit is large in volume, which is not conducive to overall transportation and on-site installation; at the same time, there is an inherent heat exchange end difference between the high-temperature water on the primary side and the low-temperature water on the secondary side inside the water-to-water plate heat exchanger, which means that the waste heat in the low-temperature section of the primary water is not fully utilized, and there is still potential for further energy saving.

[0005] Publication No.: CN211854138U A large temperature difference absorption heat exchanger unit and its heating network system are described. In this unit, the medium flowing into the unit from the primary side return pipe undergoes heat exchange in the generator and then flows directly into the secondary side supply water pipe to form part of the heat source. Simultaneously, the medium flowing out from the condenser and / or absorber also flows into the secondary side supply water pipe to form another part of the heat source. The two heat sources mix and then enter the secondary side system for heat exchange. Part of the secondary side return water after heat exchange enters the evaporator, undergoes heat exchange in the evaporator, and then flows back into the primary side system to form the first circulation path. The other part of the secondary side return water flows into the condenser and / or absorber for heating and then flows back into the secondary side supply water pipe to form the second circulation path. However, in this technical solution, the medium in the primary side return pipe mixes with the medium in the secondary side supply water pipe, leading to a mismatch between the primary and secondary side pressures, preventing operation. Furthermore, the temperature of the medium in the secondary side supply water pipe cannot be controlled, resulting in insufficient waste heat utilization efficiency.

[0006] Therefore, there is an urgent need to design a mixed-water type high-efficiency heat exchange system and its control method to solve the problems of large size, limited installation space and low waste heat utilization efficiency of existing absorption heat exchange units with large temperature difference. Summary of the Invention

[0007] In view of this, the present invention aims to propose a mixed-water type high-efficiency heat exchange system and its control method to solve the problems of large size, limited installation space and low waste heat utilization efficiency of existing absorption heat exchange units with large temperature difference.

[0008] This invention replaces the water-to-water plate heat exchanger in traditional absorption heat exchange units with a jet-type water-to-water heat exchanger. This not only effectively reduces the overall size and installation space of the unit, significantly improving the convenience of equipment transportation and on-site installation, but also further controls the overall cost of the equipment. In addition, the system can achieve zero-temperature-difference heat exchange between the high-temperature water on the primary side and the low-temperature water on the secondary side within the jet-type water-to-water heat exchanger. At the same time, a portion of the secondary side outlet water is introduced into the evaporator as low-temperature waste heat for cooling before flowing back to the primary side outlet water pipeline. This design further reduces the primary side outlet water temperature, significantly improves the overall heat exchange efficiency of the primary and secondary sides, and effectively enhances the system's heating capacity.

[0009] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0010] One object of this invention is to disclose a high-efficiency heat exchange system for mixing water, comprising:

[0011] The primary water pipeline includes a primary water inlet pipeline for introducing high-temperature primary water and a primary water outlet pipeline for discharging cooled primary water.

[0012] The secondary water pipeline includes a secondary water inlet pipeline for introducing low-temperature secondary water returned by the user and a secondary water outlet pipeline for delivering heated secondary water to the user.

[0013] A jet-type water-to-water heat exchanger has a first inlet connected to the outlet section of the primary side inlet pipe, a second inlet connected to a first branch from the secondary side inlet pipe, and an outlet connected to the secondary side outlet pipe.

[0014] An absorption heat pump cycle unit includes a generator, a condenser, an evaporator, and an absorber. The heat source side of the generator is connected to the inlet section of the primary side water inlet pipe. The cooling sides of the condenser and the absorber are connected in series to a second branch from the secondary side water inlet pipe. The heat source side of the evaporator is connected to the primary side water outlet pipe after the primary side water inlet pipe passes through the generator.

[0015] The third pipeline has one end branching off from the secondary side water inlet pipeline and connecting to the cooling side inlet of the evaporator, and the other end returning from the cooling side outlet of the evaporator to the primary side water outlet pipeline.

[0016] Furthermore, the absorption heat pump cycle unit is a type I lithium bromide absorption heat pump, and its working fluid pair is a water-lithium bromide solution.

[0017] Furthermore, it also includes a three-way regulating valve installed on the secondary side water inlet pipe, used to dynamically distribute the flow rate ratio of the fluid branched from the secondary side water inlet pipe between the second and third paths.

[0018] Furthermore, a water regulating valve is provided on the primary hot water pipeline to adjust the primary water inlet flow rate according to the secondary water inlet temperature.

[0019] Furthermore, the jet-type water-to-water heat exchanger has no heat transfer baffles inside, allowing hot water from the primary side inlet pipe to directly mix with the first return water from the secondary side inlet pipe, achieving near-zero temperature difference heat exchange.

[0020] Another objective of this invention is to disclose a control method for a mixed-flow high-efficiency heat exchange system, based on any of the aforementioned mixed-flow high-efficiency heat exchange systems, comprising the following specific steps:

[0021] S1: Real-time acquisition of the inlet water temperature of the secondary side inlet pipe;

[0022] S2: Compare the secondary side inlet water temperature with the preset target temperature. If the secondary side inlet water temperature is lower than the target temperature, proceed to step S3; if the secondary side inlet water temperature is higher than the target temperature, proceed to step S4.

[0023] S3: Open the primary water regulating valve to increase the primary hot water flow rate, and simultaneously execute step S5;

[0024] S4: Close the water regulating valve of the main network slightly, and execute step S5 simultaneously;

[0025] S5: Synchronous adjustment three-way regulating valve, so that the third flow from the secondary side water inlet pipe maintains a preset ratio with the current primary side water inlet flow, so as to ensure the effective recovery of low-temperature waste heat from the primary side by the evaporator.

[0026] Furthermore, in step S5, the preset ratio is that the flow rate of the third secondary side inlet is equal to or slightly greater than the flow rate of the primary side inlet, so as to fully cool the primary side outlet water and reduce its temperature to 20–30°C.

[0027] Furthermore, during the system startup phase, the third secondary side water inlet is opened first, and the second water inlet is opened only after the absorption heat pump cycle is stable, in order to avoid the evaporator from dry burning or the solution from crystallizing.

[0028] Furthermore, in step S5, when the primary side outlet water temperature is detected to be higher than the set upper limit, the flow rate of the third secondary side inlet is automatically increased, and the speed of the solution pump is increased in conjunction with the increase to enhance the waste heat recovery capability.

[0029] Furthermore, in step S5, the final outlet temperature of the primary side water pipe is controlled at ≤30℃, thereby achieving large temperature difference heating and reducing the energy consumption of the pipeline transmission.

[0030] Compared with the prior art, the mixed-water type high-efficiency heat exchange system and its control method of the present invention have the following advantages:

[0031] 1. This invention achieves direct mixing and heat exchange between high-temperature hot water on the primary side and a portion of low-temperature effluent on the secondary side by using a jet-type water-to-water heat exchanger. This eliminates the inherent heat transfer difference in traditional plate heat exchangers, realizes near-zero temperature difference and high-efficiency heat transfer, significantly improves heat exchange efficiency, and greatly reduces the size of the equipment, solving the problems of large structure and limited installation of traditional large temperature difference units.

[0032] 2. This invention couples an absorption heat pump cycle with mixed-water heat exchange technology, using the high-temperature section of the primary side to drive the lithium bromide heat pump cycle, and introduces secondary water through a third path into the evaporator to deeply recover the low-temperature waste heat on the primary side, so that the primary side outlet water temperature can be reduced to 20-30℃. This breaks through the technical bottleneck of conventional heat exchange systems that cannot fully recover low-grade waste heat due to the limitation of heat transfer temperature difference, and significantly improves the comprehensive energy utilization efficiency.

[0033] 3. This invention monitors the secondary side inlet water temperature and the primary side outlet water temperature in real time, and adjusts the primary side regulating valve and the three-way diverter valve in a coordinated manner to dynamically match the heat input and waste heat recovery requirements, ensuring heating stability, optimizing the system's operating energy efficiency under variable load conditions, reducing pump power consumption and carbon emissions, and possessing outstanding energy-saving performance and engineering practicality. Attached Figure Description

[0034] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0035] Figure 1 This is a schematic diagram of Embodiment 1 of the mixed-water high-efficiency heat exchange system of the present invention;

[0036] Figure 2 This is a schematic diagram of Embodiment 2 of the mixed-water high-efficiency heat exchange system of the present invention.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1. Condenser; 2. Solution heat exchanger; 3. Solution throttling element; 4. Absorber; 401. First absorber; 402. Second absorber; 5. Solution pump; 6. Three-way regulating valve; 7. Secondary side water pump; 8. Refrigerant pump; 9. Evaporator; 901. First evaporator; 902. Second evaporator; 10. Refrigerant throttling element; 11. Jet-type water-to-water heat exchanger; 12. Primary water regulating valve; 13. Generator. Detailed Implementation

[0039] To make the technical means and objectives and effects of the present invention easier to understand, the embodiments of the present invention will be described in detail below with reference to specific illustrations.

[0040] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "lateral," "longitudinal," and "center," are only used to explain the relative positional relationships and connections between components in a specific state. They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0041] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0043] In centralized heating systems, traditional heat exchange stations commonly use plate heat exchangers to transfer heat between the primary and secondary sides. However, this method has inherent drawbacks such as large heat transfer temperature difference, bulky equipment, and difficulty in reducing the primary side outlet water temperature, resulting in high energy consumption in pipeline distribution, low utilization rate of low-grade waste heat, and difficulty in meeting the technical requirements of new large temperature difference heating systems. To systematically solve the above problems, this invention proposes a mixed-water high-efficiency heat exchange system, including a generator 13, a condenser 1, an evaporator 9, an absorber 4, a solution heat exchanger 2, a refrigerant pump 8, a solution pump 5, and a jet-type water-to-water heat exchanger 11, along with supporting fluid transmission and connection pipelines such as vacuum pipelines and water pipelines. Its core lies in the organic integration of direct mixed-water heat exchange, absorption heat pump waste heat recovery, and intelligent flow control, thereby improving energy efficiency while achieving a compact structure and intelligent operation.

[0044] like Figures 1 to 2 As shown, to overcome the heat transfer losses and space occupation problems caused by traditional indirect heat exchange, this invention first introduces a jet-type water-to-water heat exchanger 11 as the main heat exchange unit. Preferably, the heat exchanger does not have metal partitions or heat transfer walls inside, allowing the high-temperature hot water on the primary side to mix directly with part of the secondary side inlet water (i.e., the low-temperature return water returned by the user) under controlled conditions. Furthermore, the heat exchanger can have a built-in Venturi throat or swirling mixing chamber structure to enhance the turbulent mixing effect and ensure rapid and uniform heat distribution.

[0045] In one specific embodiment, high-temperature hot water (e.g., 95°C) from the primary side first enters generator 13, releases some heat, and then cools to approximately 70°C. It then enters jet-type water-to-water heat exchanger 11, where it mixes with the first stream of secondary-side inlet water at approximately 40°C. The outlet water temperature can reach 68–70°C, with the heat transfer temperature difference approaching zero. This setup significantly improves local heat exchange efficiency and drastically reduces the equipment's overall size, facilitating deployment in the retrofitting of existing heat exchange stations.

[0046] To further address the technical bottlenecks of ineffective utilization of waste heat in the primary low-temperature section and persistently high outlet water temperature, this invention integrates the aforementioned mixed-water heat exchange structure with an absorption heat pump circulation unit. This circulation unit uses water-lithium bromide as the working fluid pair and mainly includes a generator 13, a condenser 1, an evaporator 9, an absorber 4, a solution heat exchanger 2, a solution pump 5, a refrigerant pump 8, as well as vacuum-sealed pipes and matching control valves connecting the various components.

[0047] Specifically, high-temperature hot water on the primary side serves as the driving heat source, heating the dilute solution from the absorber 4 in the generator 13, causing it to concentrate and release refrigerant water vapor. After cooling down, the hot water enters the jet-type water-to-water heat exchanger 11. The generated refrigerant vapor flows into the condenser 1 through a vacuum pipe, where it liquefies into refrigerant water under the cooling effect of the second secondary side inlet water. The refrigerant water then enters the evaporator 9 through the throttling device 10, where it absorbs heat and evaporates—its heat source being the low-temperature hot water at the end of the primary side process. To achieve efficient evaporation, a refrigerant pump 8 is installed at the bottom of the evaporator 9 to force the accumulated refrigerant water to the top of the evaporation coil for uniform spraying, thereby improving evaporation efficiency and preventing dry burning.

[0048] Meanwhile, the concentrated solution flowing out of generator 13 is pre-cooled by solution heat exchanger 2 before entering absorber 4. Solution heat exchanger 2 is preferably a high-efficiency plate or spiral wound structure, and its function is to use the dilute solution about to return to generator 13 to cool the high-temperature concentrated solution, while preheating the dilute solution, thereby recovering internal heat and improving the cycle performance coefficient. The concentrated solution entering absorber 4 absorbs refrigerant vapor from evaporator 9, releases absorbed heat, and is converted into dilute solution; this process is carried away by the heat carried away by the second secondary side inlet water flowing through the cooling side of absorber 4, completing the heat output. Subsequently, driven by solution pump 5, the dilute solution first passes through solution heat exchanger 2 to recover heat, and then returns to generator 13, forming a closed solution cycle.

[0049] To ensure stable operation of the entire heat pump cycle under high vacuum and leak-free conditions, all working fluid flow paths are connected by welded or metal-sealed vacuum pipes, and equipped with vacuum detection ports and automatic evacuation devices. In addition, manual shut-off valves and electric regulating valves are installed at key nodes, such as the generator 13 outlet, evaporator 9 inlet, and before and after the solution pump 5, for maintenance isolation, start-up and shutdown control, and flow fine-tuning.

[0050] To deeply recover low-grade heat at the end of the primary side process, this invention innovatively sets up a third secondary side water inlet. This water flows through the cooling side of the evaporator 9, absorbs residual heat from the primary side as a cold source, and then does not return to the user end, but directly flows into the primary side outlet water pipe. More preferably, the flow rate of this third inlet is controlled to be basically equal to or slightly higher than the primary side flow rate, thereby ensuring that the final outlet water temperature of the primary side can be stably reduced to 20–30℃, achieving true large temperature difference heating.

[0051] To ensure a stable and uniformly distributed heating medium for the user side, this invention employs a three-way diversion design for the secondary side inlet water. Specifically, the low-temperature secondary side inlet water (e.g., 40°C) first enters the three-way regulating valve 6 and is divided into three paths: the first path, the second path, and the third path.

[0052] The first stream enters the jet-type water-to-water heat exchanger 11 to participate in direct mixing;

[0053] The second stream flows sequentially through absorber 4 and condenser 1, absorbing heat and increasing temperature step by step.

[0054] The third channel is dedicated to waste heat recovery, as described above. Preferably, the flow rate of the secondary side inlet water in the third channel is set to be equal to or slightly larger than the primary side flow rate.

[0055] Furthermore, the heated water flows from the first and second paths converge at the front end of the secondary outlet pipe and are preferably homogenized by a static mixer to eliminate local temperature fluctuations caused by path differences. Thus, the system maintains excellent heating quality while efficiently recovering energy.

[0056] To achieve adaptive and efficient operation under all working conditions and avoid mismatch between waste heat recovery and heat load demand, this invention incorporates a coordinated control strategy. In a preferred embodiment, the control system collects real-time inlet water temperature signals from the secondary side outlet pipe and outlet water temperature signals from the primary side outlet pipe, and dynamically adjusts two key actuators based on preset target values: the primary water regulating valve 12 and the three-way regulating valve 6. The specific control logic is as follows: when the supply water temperature is lower than the set value, the primary water regulating valve 12 is opened wider to increase the input of high-temperature heat sources; simultaneously, based on the current primary side flow rate, the opening of the three-way regulating valve 6 is automatically adjusted to maintain a preset ratio between the third-way flow rate and the primary side flow rate. More specifically, this ratio can be feedforward corrected according to seasonal load or outdoor temperature—for example, appropriately increasing the third-way ratio during severe cold periods to enhance waste heat recovery, and moderately reducing it during transitional seasons to prevent over-cooling. Preferably, the system also integrates a crystallization protection mechanism: when the solution temperature inside the absorber 4 is detected to be close to the lithium bromide crystallization threshold, the third-way flow rate is automatically reduced or a dilution cycle is initiated to prevent equipment damage.

[0057] Furthermore, to improve system reliability and maintenance convenience, this invention incorporates filters and drain outlets at the inlets of the primary and secondary water pipes, and preferably adopts a modular integrated design—encapsulating the jet-type water-to-water heat exchanger 11, the absorption heat pump body, main valves, and sensors within the same insulated housing, forming a compact heat exchange unit that can be hoisted as a whole and is plug-and-play. In one embodiment, the unit's dimensions are reduced by more than 40% compared to traditional large temperature difference units, and no on-site welding is required, significantly shortening the construction period.

[0058] In summary, this invention, through a technical architecture of "near-zero temperature difference mixed water heat exchange + low-temperature waste heat heat pump upgrade + three-way intelligent coordinated control," systematically solves the key technical problems of traditional heat exchange systems, such as low energy efficiency, large size, slow control, and high outlet water temperature, through multi-dimensional synergistic optimization from thermodynamics, fluid mechanics, and automatic control. Actual operating data shows that the primary side outlet water temperature of this system can be stably controlled below 30℃, with a significantly improved overall performance coefficient, demonstrating outstanding energy-saving benefits and broad engineering application value.

[0059] To improve the safety and stability of system start-up and shutdown, this invention further optimizes the control logic for cold start-up and abnormal operating conditions. In a preferred embodiment, during the initial stage of system startup, the third secondary side water inlet is preferentially opened, allowing it to flow through the cooling side of the evaporator 9 to establish initial cooling conditions for the evaporator and prevent the heat exchange tubes from dry burning due to lack of cooling medium. After the refrigerant circulation in the evaporator is initially established and the solution concentration in the generator 13 and absorber 4 tends to stabilize, the second secondary side water inlet is gradually opened to provide the absorber 4 with the necessary cooling, thereby meeting the dual safety requirements of preventing dry burning of the evaporator and preventing crystallization of the lithium bromide solution.

[0060] In addition, to cope with the rise in return water temperature caused by fluctuations in primary side residual heat or sudden load changes, the present invention also sets up a high-temperature adaptive control mechanism: when the temperature of the primary side outlet water pipe exceeds the preset upper limit (e.g., 32°C) in real time, the control system automatically increases the opening of the three-way regulating valve 6 to the third channel, increasing the secondary side inlet water flow rate of the third channel; at the same time, it links to increase the motor speed of the solution pump 5, accelerates the circulation rate of the dilute solution, and enhances the heat absorption capacity of the evaporator 9 for the primary side low-temperature hot water, thereby quickly suppressing the rising trend of the primary side outlet water temperature and ensuring that it is stably maintained below 30°C.

[0061] The above control strategy significantly improves the robustness of the system and the efficiency of waste heat recovery under varying operating conditions through multivariate collaborative feedback.

[0062] Example 1

[0063] This invention discloses a high-efficiency heat exchange system of mixing water, such as... Figure 1As shown, the system mainly consists of core components such as generator 13, condenser 1, evaporator 9, absorber 4, solution heat exchanger 2, refrigerant pump 8, solution pump 5, jet-type water-to-water heat exchanger 11, vacuum pipeline and water pipeline.

[0064] After being heated by high-temperature hot water on the primary side in generator 13, the dilute lithium bromide solution evaporates and is converted into a concentrated lithium bromide solution. The separated refrigerant water vapor enters condenser 1 and condenses into refrigerant water. The concentrated solution flows through solution heat exchanger 2, where it exchanges heat with the dilute solution from absorber 4 to cool down. After being depressurized by solution throttling element 3, it flows into absorber 4, where it absorbs refrigerant water vapor from evaporator 9. After completing the absorption process, it is converted into a dilute solution. This dilute solution is cooled by secondary side water inlet in absorber 4 and then driven by solution pump 5. It first enters solution heat exchanger 2 to exchange heat with the concentrated solution to raise its temperature, and then enters generator 13, thus completing the entire circulation process of lithium bromide solution.

[0065] The refrigerant water vapor separated by generator 13 enters condenser 1, where it exchanges heat with the secondary side inlet water and condenses into liquid refrigerant water. The liquid refrigerant water is depressurized through the refrigerant pipeline and refrigerant throttling element 10 and then enters evaporator 9. It absorbs the residual heat of the primary side low-temperature hot water outside the tubes of evaporator 9 to complete evaporation and is converted into refrigerant water vapor. It then enters absorber 4 and is absorbed by lithium bromide concentrated solution to realize refrigerant water circulation.

[0066] The primary side high-temperature water first enters the generator 13 and completes the first heat exchange and cooling with the dilute lithium bromide solution. The cooled primary side hot water then enters the jet-type water-to-water heat exchanger 11 and directly mixes and exchanges heat with the first secondary side inlet water. The mixed hot water flows into the secondary side outlet water pipeline and is delivered to the heat user end. In addition, the primary side inlet water pipeline is equipped with a network water regulating valve 12 to accurately control the total amount of hot water entering the unit, providing a basis for load regulation.

[0067] The secondary water inlet is divided into three parts:

[0068] The first part is mixed with the primary side water supply through the jet-type water-to-water heat exchanger 11 and then enters the secondary side water outlet pipeline;

[0069] The second part flows through absorber 4 and condenser 1 in succession, and after being heated, it enters the secondary side outlet water pipe.

[0070] The third part goes directly into the evaporator tube 9 side, where it absorbs waste heat as a cooling medium and then returns to the primary side outlet water pipe.

[0071] The secondary water circuit is equipped with a secondary water pump 7 to provide power for water circulation; a three-way regulating valve 6 is installed at the outlet of the secondary water pump 7 to distribute the flow of the second and third circuits.

[0072] The unit's load regulation is based on the secondary side inlet water temperature as the core control target. The temperature sensor collects the outlet temperature of the secondary side inlet water pipe in real time, calculates the deviation between the detected value and the set target value, and adaptively adjusts the opening of the primary water regulating valve 12. At the same time, the system dynamically matches the opening of the three-way regulating valve 6 according to the real-time flow of the primary side to ensure that the flow of the third channel is consistent with the flow of the primary side, thus ensuring the stability of the waste heat recovery efficiency of the evaporator 9.

[0073] Example 2

[0074] This invention discloses a high-efficiency heat exchange system of mixing water, such as... Figure 2 As shown, the system mainly consists of core components such as generator 13, condenser 1, first evaporator 901, second evaporator 902, first absorber 401, second absorber 402, solution heat exchanger 2, refrigerant pump 8, solution pump 5, jet-type water-to-water heat exchanger 11, vacuum pipeline and water pipeline.

[0075] The lithium bromide solution is heated to a concentrated solution by high-temperature hot water in the generator 13. The separated refrigerant water vapor enters the condenser 1 and condenses into liquid refrigerant water. The concentrated solution exchanges heat with the dilute solution in the solution heat exchanger 2 to cool down. After being depressurized by the solution throttling element 3, it first enters the first absorber 401, where it absorbs refrigerant water vapor from the first evaporator 901 to become a dilute solution. The dilute solution is cooled by secondary water in the first absorber 401 and then enters the second absorber 402, where it absorbs refrigerant water vapor from the second evaporator 902. After being cooled by secondary water in the second absorber 402, it is driven by the solution pump 5 to first enter the solution heat exchanger 2 to exchange heat with the concentrated solution to raise its temperature, and then enters the generator 13 to complete the solution circulation.

[0076] The refrigerant water is condensed in the condenser 1 by the refrigerant water vapor from the generator 13, and then enters the first evaporator 901 through the refrigerant pipeline and the refrigerant throttling element 10. It evaporates outside the tube of the first evaporator 901 and becomes refrigerant water vapor, which enters the first absorber 401. Then it enters the second evaporator 902 and evaporates into refrigerant water vapor, which enters the second absorber 402.

[0077] By employing a combination of two-stage evaporators and absorbers, the recovery temperature of the primary side outlet water is further reduced, thereby improving the efficiency of the heat exchange system.

[0078] The primary high-temperature water supply first enters the generator 13 to heat the lithium bromide solution, achieving the first heat exchange. Then it enters the jet-type water-to-water heat exchanger 11, where it directly mixes and exchanges heat with a portion of the secondary side inlet water. The mixed hot water then enters the secondary side outlet water pipeline for use by heating users. A network water regulating valve 12 is installed on the primary side high-temperature water supply pipeline to control the amount of hot water entering the unit.

[0079] The secondary water inlet is divided into three parts:

[0080] The first part is mixed with the primary side water supply through the jet-type water-to-water heat exchanger 11 and then enters the secondary side water outlet pipeline;

[0081] The second part flows through the second absorber 402, the first absorber 401, and the condenser 1 in sequence, and enters the secondary side outlet pipe after being heated.

[0082] The third part directly enters the pipe side of the first evaporator 901 and the second evaporator 902 as a cooling medium. After being cooled in the evaporator, it returns to the primary side outlet pipe.

[0083] The secondary water circuit is equipped with a secondary water pump 7 to provide power for water circulation; a three-way regulating valve 6 is installed at the outlet of the secondary water pump 7 to distribute the flow of the second and third circuits.

[0084] The unit's load regulation is based on the secondary side inlet water temperature as the core control target. The inlet temperature data is collected in real time by the secondary side outlet water temperature sensor. The deviation between the detected value and the set target value is calculated, and the opening of the primary water regulating valve 12 is adaptively adjusted according to the magnitude of the deviation. At the same time, the system can dynamically match the opening of the secondary side three-way regulating valve 6 according to the real-time flow rate of the primary side water supply, ensuring that the secondary water flow rate of the third part is consistent with the primary side water supply flow rate, thus ensuring the stability of the evaporator waste heat recovery efficiency.

[0085] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-efficiency heat exchange system for mixing water, characterized in that, include: The primary water pipeline includes a primary water inlet pipeline for introducing high-temperature primary water and a primary water outlet pipeline for discharging cooled primary water. The secondary water pipeline includes a secondary water inlet pipeline for introducing low-temperature secondary water returned by the user and a secondary water outlet pipeline for delivering heated secondary water to the user. The jet-type water-to-water heat exchanger (11) has a first inlet connected to the outlet section of the primary side water inlet pipe, a second inlet connected to the first branch from the secondary side water inlet pipe, and an outlet connected to the secondary side water outlet pipe. An absorption heat pump cycle unit includes a generator (13), a condenser (1), an evaporator (9), and an absorber (4). The heat source side of the generator (13) is connected to the inlet section of the primary side water inlet pipe. The cooling sides of the condenser (1) and the absorber (4) are connected in series to a second path branched off from the secondary side water inlet pipe. The heat source side of the evaporator (9) is connected to the primary side water outlet pipe. The third pipeline has one end branched off from the secondary side water inlet pipeline and connected to the cooling side inlet of the evaporator (9), and the other end returned from the cooling side outlet of the evaporator (9) to the primary side water outlet pipeline.

2. The high-efficiency heat exchange system of the mixing type according to claim 1, characterized in that, The absorption heat pump cycle unit is a type I lithium bromide absorption heat pump, and its working fluid pair is a water-lithium bromide solution.

3. The high-efficiency heat exchange system of the mixing type according to claim 1, characterized in that, It also includes a three-way regulating valve (6) installed on the secondary side water inlet pipe, used to dynamically distribute the flow ratio of the fluid split from the secondary side water inlet pipe between the second and third paths.

4. The high-efficiency heat exchange system of the mixing type according to claim 1, characterized in that, A water regulating valve (12) is provided on the primary side hot water pipeline to regulate the primary side inlet flow rate according to the secondary side inlet water temperature.

5. The high-efficiency heat exchange system of the mixing type according to claim 1, characterized in that, The jet-type water-to-water heat exchanger (11) has no heat transfer baffle inside, allowing hot water from the primary side inlet pipe to directly mix with the first return water from the secondary side inlet pipe, thus achieving near-zero temperature difference heat exchange.

6. A control method for a mixed-flow high-efficiency heat exchange system, characterized in that, The mixed-water type high-efficiency heat exchange system based on any one of claims 1-5 includes the following specific steps: S1: Real-time acquisition of the inlet water temperature of the secondary side inlet pipe; S2: Compare the secondary side inlet water temperature with the preset target temperature. If the secondary side inlet water temperature is lower than the target temperature, proceed to step S3; if the secondary side inlet water temperature is higher than the target temperature, proceed to step S4. S3: Open the primary water regulating valve (12) to increase the primary hot water flow rate, and execute step S5 simultaneously; S4: Close the main water regulating valve (12) and execute step S5 simultaneously; S5: Synchronously adjust the three-way regulating valve (6) to keep the third flow from the secondary side water inlet pipe in a preset ratio with the current primary side water inlet flow, so as to ensure that the evaporator (9) can effectively recover the low-temperature waste heat of the primary side.

7. The control method for the mixed-water high-efficiency heat exchange system according to claim 6, characterized in that, In step S5, the preset ratio is that the flow rate of the third secondary side inlet is equal to or slightly greater than the flow rate of the primary side inlet, so as to fully cool the primary side outlet water and reduce its temperature to 20–30°C.

8. The control method for the mixed-water high-efficiency heat exchange system according to claim 6, characterized in that, During the system startup phase, the third secondary side water inlet is first turned on, and the second water inlet is turned on after the absorption heat pump cycle is stable, in order to avoid the evaporator (9) from dry burning or solution crystallization.

9. The control method for the mixed-water high-efficiency heat exchange system according to claim 6, characterized in that, In step S5, when the temperature of the primary side outlet water is detected to be higher than the set upper limit, the flow rate of the third secondary side inlet water is automatically increased, and the speed of the solution pump (5) is increased in conjunction with the increase to enhance the waste heat recovery capability.

10. The control method for the mixed-water high-efficiency heat exchange system according to claim 6, characterized in that, In step S5, the final outlet temperature of the primary side water pipe is controlled at ≤30℃, thereby achieving large temperature difference heating and reducing the energy consumption of pipeline transmission.

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