A widely adjustable absorption heat pump

Abstract

The application provides a wide-range adjustable absorption heat pump, and relates to the field of waste heat recovery heating. The application solves the problems of poor solution flow, unimprovable load, and unsatisfied heating demand at the beginning and end of the heating period, and adopts the following scheme: a condenser is internally provided with a first water inlet and a first water outlet, a bypass valve is connected between the first water inlet and the first water outlet, the bypass valve is provided with a flow adjusting part, and the flow adjusting part is used for adjusting the opening degree of the bypass valve; an evaporator is internally provided with a waste heat water inlet and a waste heat water outlet, and is used for absorbing external waste heat; the top of the evaporator is connected to the top of an absorber through a gaseous refrigerant water pipeline; the absorber is internally provided with a second water inlet and a second water outlet, and the lower part of the absorber is connected to the upper part of a generator through a dilute solution pipeline; and the generator is heated by an external heat source to heat internal solution to boiling, and water vapor is generated. The technical scheme of the application can realize wide-range and accurate adjustment.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery heating, and more particularly to an absorption heat pump that can be adjusted over a wide range. Background Technology

[0002] Traditional heat pump systems typically include main components such as a generator, condenser, absorber, and evaporator, as well as auxiliary components such as a solution pump, refrigerant pump, and solution heat exchanger. In conventional operation, the solution and refrigerant water circulate within the four main components of the unit via the solution pump and refrigerant pump, thereby converting external heat energy into usable heat energy.

[0003] Absorption heat pumps used for heating suffer from problems such as poor solution flow, inability to increase load, inability to adjust over a wide range, and inability to meet heating demand during the initial and late cold periods of the heating season. Summary of the Invention

[0004] To solve the above-mentioned technical problems, in a first aspect, the present invention provides an absorption heat pump that can be adjusted over a wide range, comprising:

[0005] A condenser is provided with a first water inlet and a first water outlet. The condenser is connected to the top of the evaporator through a liquid refrigerant water pipeline. A bypass valve is connected between the first water inlet and the first water outlet. The bypass valve has a flow regulating element, which is used to adjust the opening degree of the bypass valve.

[0006] The evaporator is equipped with a waste hot water inlet and a waste hot water outlet for absorbing external waste heat. The top of the evaporator is connected to the top of the absorber via a gaseous refrigerant water pipeline.

[0007] The absorber is provided with a second inlet and a second outlet, and the lower part of the absorber is connected to the upper part of the generator through a dilute solution pipeline;

[0008] The generator uses an external heat source to heat the internal solution to boiling, generating water vapor. The heated and concentrated solution is cooled by a solution heat exchanger in the concentrated solution pipeline and then enters the absorber. The water vapor passes through the top of the generator and enters the condenser through a water vapor pipeline.

[0009] In some embodiments, the wide-range adjustable absorption heat pump has an automatic control system that controls the flow regulating element of the bypass valve, and the control parameters of the automatic control system include the crystallization margin of the solution concentration in the generator.

[0010] In some embodiments, the solution in the generator has a concentration meter that transmits the measured solution concentration to the automatic control system, which determines the crystallization margin of the solution in the generator based on the solution concentration.

[0011] In some embodiments, the control parameters further include internal parameters of the absorption heat pump, including the internal temperature of the generator solution. The automatic control system is also configured to determine the crystallization margin of the generator solution concentration based on the solution temperature and the solution concentration.

[0012] In some embodiments, the generator solution contains a thermometer that transmits the measured solution temperature to the automatic control system.

[0013] In some embodiments, the wide-range adjustable absorption heat pump is a single-stage heat pump, and the second outlet of the absorber is connected to the first inlet of the condenser via a heating water pipeline.

[0014] In some embodiments, the wide-range adjustable absorption heat pump is multi-stage, and the first water inlet of the condenser is connected to the first water outlet of the condenser of the previous stage absorption heat pump.

[0015] In some embodiments, a refrigerant circulation pipeline is further connected between the lower part and the upper part of the evaporator, and a refrigerant circulation pump is provided on the refrigerant circulation pipeline.

[0016] In some embodiments, the water vapor enters the condenser through a water vapor pipe after passing through the top of the generator, specifically including: the water vapor entering the condenser after passing through a baffle plate at the top of the generator.

[0017] The above-mentioned technical solution of the present invention has at least the following beneficial technical effects: Based on the characteristics of the absorption heat pump process and the excellent operating conditions during the initial and final cold periods of heating, the technical solution of the embodiments of the present invention finds a solution that minimizes the impact on unit performance, namely, bypassing the condenser and not bypassing the absorber, and introducing the control of the bypass valve into the control range of the absorption heat pump itself, thereby achieving wide-range and precise adjustment; In the technical solution of the present invention, a bypass valve 5 is connected between the first inlet and the first outlet of the condenser. The bypass valve 5 has a flow regulating component, which is used to adjust the opening of the bypass valve 5, thereby adjusting the flow rate entering the condenser. When the temperature is low, a large flow rate is used, increasing the opening of the bypass valve, resulting in a large flow rate entering the condenser; when the temperature is high, a small flow rate is used, reducing the opening of the bypass valve, resulting in a small flow rate entering the condenser, achieving wide-range and more precise adjustment. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the conventional art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of an absorption heat pump in the prior art provided by the present invention;

[0020] Figure 2 This is a schematic diagram of an improved absorption heat pump in the prior art of this invention;

[0021] Figure 3 This is a schematic diagram of a single-stage absorption heat pump provided in an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of a multi-stage absorption heat pump provided in an embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of another multi-stage absorption heat pump provided in an embodiment of the present invention;

[0024] Figure 6 This is a schematic diagram of another multi-stage absorption heat pump provided in an embodiment of the present invention.

[0025] in, Figures 1 to 2 The correspondence between the reference numerals and component names in the attached drawings is as follows:

[0026] 1-Condenser, 2-Evaporator, 3-Absorber, 4-Generator, P1-Condensing pressure, P2-Evaporating pressure, T1-Condenser outlet water temperature, T2-Evaporator outlet water temperature. Detailed Implementation

[0027] 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. 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.

[0028] If the embodiments of this application involve descriptions such as "first" or "second," such descriptions 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. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features; the technical solutions of various embodiments can be combined with each other, based on what those skilled in the art can implement.

[0029] Absorption heat pumps are common equipment in waste heat recovery heating systems. An absorption heat pump consists of two sealed chambers: a generator / condenser chamber and an evaporator / absorber chamber. The solution and refrigerant water need to flow between the two chambers, typically requiring a shielded pump and taking into account the internal pressure difference.

[0030] Absorption heat pumps used for heating suffer from problems such as poor solution flow and inability to increase load during the initial and late cold periods of the heating season.

[0031] The heat pump process in the prior art is shown in the attached figure. Figure 1 As shown.

[0032] 1-Condenser, 2-Evaporator, 3-Absorber, 4-Generator, P1-Condensing pressure, P2-Evaporating pressure, T1-Condenser outlet water temperature, T2-Evaporator outlet water temperature.

[0033] The working principle of a heat pump is as follows: A heat pump consists of four main components: generator 4, condenser 1, absorber 3, and evaporator 2, as well as components such as a solution pump, refrigerant pump, and solution heat exchanger (not shown in the diagram). The solution pump and refrigerant pump are both vacuum-shielded pumps, whose main function is to circulate the solution and refrigerant water within the four main components of the unit. The location of the solution pump varies depending on the unit structure; in this diagram, it is considered to be located at absorber 3. In generator 4, an external high-temperature heat source (dashed line pipe ----) heats the solution to boiling, generating water vapor. The concentrated solution is cooled by the solution heat exchanger and then enters absorber 3 for distribution (shown as a spray in the diagram, but it could also be a drip structure). The water vapor generated in generator 4 passes through a baffle plate and enters the condenser, where it condenses into water and releases heat, heating external hot water (double-dotted line). The refrigerant water formed by the condensation of water vapor enters the evaporator and evaporates, absorbing external waste heat (single-dotted line). Unevaporated refrigerant water is then recycled through a refrigerant pump. Water vapor generated in the evaporator is absorbed by the concentrated solution in the absorber, releasing heat to heat the hot water pipes (double-dotted lines). The concentrated solution absorbs water vapor to form a dilute solution, which is then heated through a solution heat exchanger by a solution pump before re-entering the generator to continue the cycle.

[0034] As can be seen from the above process, the condensing pressure of condenser 1 is determined by the characteristics of water vapor, corresponding to a unique condensing temperature. This condensing temperature needs to heat the water in the heat exchange tubes to the outlet water temperature T1, i.e., condensing temperature > T1. The temperature difference is generally 2-5℃. For example, if the outlet water temperature is 60℃, the condensing temperature is 62℃, and the condensing pressure is approximately 22 kPa. Similarly, the evaporation pressure is also affected by the evaporator outlet water temperature T2, and the evaporation temperature < T2. For example, if the waste water is cooled from 30℃ to 20℃, the evaporation temperature is 18℃, and the evaporation pressure is 2 kPa. Since the heat pump absorbs low-temperature waste heat to heat high-temperature water, under normal conditions, T1 > T2, meaning the condensing pressure > the evaporation pressure. Thus, a pressure difference exists between the generating / condensing chamber and the absorption / evaporation chamber. When the solution and refrigerant water flow between them, they are affected by the height difference, pressure difference, and pump output.

[0035] The parameters of waste heat recovery in the heating sector are as follows: During the early and late cold periods, outdoor temperatures are high, waste heat temperatures are relatively high (such as circulating water and flue gas waste heat), and the heating network water temperature is low, even close to the waste heat temperature; during the severe cold periods, outdoor temperatures are low, waste heat temperatures decrease, and the heating network water temperature increases. The two extreme operating conditions differ significantly.

[0036] During periods of severe cold, the condenser 1 of the heat pump has a high outlet water temperature and high condensing pressure, while the evaporator 2 has a low outlet water temperature and low evaporating pressure, resulting in a significant pressure difference and a lower output from the canned motor pump. Conversely, during the early to late colder periods, the condenser 1 has a low outlet water temperature and relatively low condensing pressure, while the evaporator 2 has a high outlet water temperature and relatively high evaporating pressure, resulting in a smaller pressure difference and a higher output from the canned motor pump. Therefore, the canned motor pump in a heating-type absorption heat pump is generally selected to ensure a wider adjustment range.

[0037] However, in some special cases, such as during the extreme early winter months of flue gas waste heat recovery projects or the restart phase of projects after prolonged heating shutdowns, the pressure difference is essentially nonexistent, requiring the canned motor pump to operate at a much higher capacity. Taking flue gas waste heat recovery projects as an example, during the initial startup phase of an early winter period, the large volume of flue gas continuously heats the heating network water, potentially raising the intermediate water temperature to 50°C. At this point, the heating network water temperature is around 40°C, potentially creating a reverse pressure difference, requiring a significantly higher canned motor pump output. However, heat pumps are generally designed for severe winter conditions with intermediate water around 20°C and heating network water above 50°C. If a canned motor pump is selected based on the reverse pressure difference, it will operate at minimal capacity during normal operation, resulting in unstable performance. Therefore, canned motor pump selection typically does not consider this scenario, leading to significant startup difficulties. Furthermore, if there has been a prolonged heating shutdown, and the heating network water temperature drops below the waste water temperature, a similar situation will occur during startup. Startup is also very challenging in such cases.

[0038] If started under these conditions (when T1 is close to T2, or when T2 is higher than T1), the internal circulation volume of the heat pump is very small, making it impossible to increase the load. If the heating load of generator 4 is slightly larger (when T2 is high, the system has difficulty flowing), the solution temperature in generator 4 will rise sharply, approaching the crystallization condition, and the automatic control system will immediately reduce the load on generator 4. Ultimately, this results in the heat pump operating only at a very low load, unable to increase the load and meet the heating demand.

[0039] To solve the above problems, there are two solutions: The first is to require the heat pump to be started only when the external load reaches a certain level. At this time, the temperature of the heating network water rises, and after being heated by the heat pump, the temperature of the condenser outlet water rises, and the internal pressure is high, which can form a positive pressure difference and ensure that it is within the design range of the canned pump.

[0040] The second method involves installing bypass pipes and regulating valves on the system. By manually adjusting the valves, a portion of the water flow is bypassed, reducing the amount of water entering the heat pump's heating network, widening the temperature difference, increasing the condenser outlet water temperature, and raising the internal pressure. This also meets the design requirements of a canned motor pump. Essentially, a bypass valve is added to the hot water side to bypass the entire heat pump (absorber and condenser). Figure 2 As shown.

[0041] However, both of these methods have problems.

[0042] The first option cannot be operated during the early to late cold period, resulting in a reduction in waste heat recovery and a significant decrease in the project's economic and environmental benefits. The full start-up time is nearly a month, and even at the fastest, it is nearly half a month (in fact, the early to late cold period is a stage with very good external parameters, and if it is operated, a large amount of waste heat can be recovered).

[0043] The second option requires manual operation, which is difficult to adjust and cannot be precisely controlled, resulting in poor unit operation (too little bypass makes the heat pump difficult to operate, while too much bypass leads to excessively high condenser outlet temperature, deteriorating parameters and affecting the heat pump's waste heat recovery, making it difficult to control). In other words, the second option has two drawbacks: first, the valves are added to the system later, making it impossible to achieve automatic control of the heat pump based on internal parameters; second, system modifications can only bypass both the absorber and condenser, which does not help solve the problem but only worsens the operating conditions.

[0044] Therefore, how to design a heat pump that can automatically adjust under low load and optimal parameters, and meet the heating demand under such conditions, is a technical problem that needs to be solved.

[0045] To address the aforementioned problems, one embodiment of the present invention provides an absorption heat pump with a wide adjustable range, such as... Figure 3As shown, the embodiment of the present invention is described using a single-stage absorption heat pump as an example, including:

[0046] The condenser 1 is provided with a first water inlet and a first water outlet. The condenser is connected to the top of the evaporator 2 through a liquid refrigerant water pipeline. A bypass valve 5 is connected between the first water inlet and the first water outlet. The bypass valve 5 has a flow regulating component, which is used to adjust the opening degree of the bypass valve 5.

[0047] Evaporator 2 is equipped with a waste hot water inlet and a waste hot water outlet for absorbing external waste heat. The top of evaporator 2 is connected to the top of absorber 3 through a gaseous refrigerant water pipeline.

[0048] Absorber 3 is provided with a second inlet and a second outlet. The lower part of absorber 3 is connected to the upper part of generator 4 through a dilute solution pipeline.

[0049] Generator 4 uses an external heat source to heat the internal solution to boiling point, generating water vapor. The heated and concentrated solution is cooled by the solution heat exchanger in the concentrated solution pipeline and then enters the absorber 3. The water vapor passes through the top of generator 4 and enters the condenser 1 through the water vapor pipeline.

[0050] The technical solution of this invention, based on the characteristics of the absorption heat pump process and the excellent operating conditions during the initial and final cold periods of heating, finds a solution that minimizes the impact on unit performance. This solution involves bypassing the condenser and not bypassing the absorber, and introducing the control of the bypass valve into the control range of the absorption heat pump itself. This achieves both wide-range and precise adjustment. A bypass valve 5 is connected between the first inlet and the first outlet of the condenser. The bypass valve 5 has a flow regulating component, which is used to adjust the opening of the bypass valve 5, thereby regulating the flow rate entering the condenser. When the temperature is low, a large flow rate is used, increasing the opening of the bypass valve and resulting in a large flow rate into the condenser. When the temperature is high, a small flow rate is used, decreasing the opening of the bypass valve and resulting in a small flow rate into the condenser, thus achieving wide-range and precise adjustment.

[0051] Optional, wide-range adjustable absorption heat pumps have an automatic control system that controls the flow regulating element of the bypass valve. The control parameters of the automatic control system include the crystallization margin of the solution concentration in the generator.

[0052] The technical solution of this invention introduces the control of the bypass valve into the control range of the absorption heat pump itself, which can be adjusted over a wide range, thereby achieving precise adjustment. Moreover, the control process does not require human intervention, saving human resources and realizing automatic control.

[0053] Optionally, the generator solution has a concentration meter that transmits the measured solution concentration to an automatic control system, which then determines the crystallization margin of the generator solution based on the solution concentration.

[0054] Optionally, the control parameters also include the internal parameters of the absorption heat pump that can be adjusted over a wide range. The internal parameters include the internal temperature of the generator solution. The automatic control system is also used to determine the crystallization margin of the generator solution concentration based on the solution temperature and the solution concentration.

[0055] The automatic control system uses two technical solutions to determine the crystallization margin of the generator solution concentration, based on the solution concentration or the crystallization margin together with the solution concentration. This provides a basis for the automatic control system to control the bypass valve, so that the automatic control system can more accurately control the opening of the bypass valve and achieve more precise regulation of the absorption heat pump.

[0056] Optionally, the generator solution contains a thermometer that transmits the measured solution temperature to an automatic control system.

[0057] Optionally, the absorption heat pump is a single-stage system, with the second outlet of the absorber connected to the first inlet of the condenser via a pipeline.

[0058] like Figure 3 As shown, for a single-stage absorption heat pump, the second outlet of the absorber is connected to the first inlet of the condenser via a heating water pipeline.

[0059] Optionally, the absorption heat pump can be multi-stage, with the first inlet of the condenser connected to the first outlet of the condenser of the previous stage absorption heat pump.

[0060] like Figure 4 , Figure 5 , Figure 6 As shown, in the multi-stage structure of this invention, a bypass pipe and bypass valve can be added to one stage (not necessarily the highest or lowest stage), or two or more stages can be added, or bypass valves can be added to all stages. With multiple bypass valves, the opening degree of each valve can be determined according to external adjustments and unit performance, achieving more flexible regulation.

[0061] Optional, such as Figure 3 As shown, a refrigerant circulation pipeline is connected between the lower part and the upper part of the evaporator, and a refrigerant circulation pump is installed on the refrigerant circulation pipeline.

[0062] Optionally, water vapor enters the condenser through a water vapor pipe after passing through the top of the generator, specifically by passing through a baffle plate on the top of the generator into the condenser.

[0063] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A wide-range adjustable absorption heat pump, characterized in that, include: A condenser is provided with a first water inlet and a first water outlet. The condenser is connected to the top of the evaporator through a liquid refrigerant water pipeline. A bypass valve is connected between the first water inlet and the first water outlet. The bypass valve has a flow regulating element, which is used to adjust the opening degree of the bypass valve. The evaporator is equipped with a waste hot water inlet and a waste hot water outlet for absorbing external waste heat. The top of the evaporator is connected to the top of the absorber through a gaseous refrigerant water pipeline. The absorber is provided with a second inlet and a second outlet, and the lower part of the absorber is connected to the upper part of the generator through a dilute solution pipeline; The generator uses an external heat source to heat the internal solution to boiling, generating water vapor. The concentrated solution is cooled by the solution heat exchanger in the concentrated solution pipeline and then enters the absorber. The water vapor passes through the top of the generator and enters the condenser through the water vapor pipeline. An automatic control system, whose control parameters include the crystallization margin of the generator solution, is used to control the flow regulating element of the bypass valve; The automatic control system is further configured to: when the outlet water temperatures of the condenser and the evaporator are similar, or the outlet water temperature of the evaporator is higher than that of the condenser, resulting in insufficient internal pressure difference in the heat pump, adjust the opening of the bypass valve according to the control parameters to increase the internal pressure difference, thereby expanding and regulating the heat pump load.

2. The wide-range adjustable absorption heat pump according to claim 1, characterized in that, The generator has a concentration meter in its solution, which transmits the measured solution concentration to the automatic control system. The automatic control system determines the crystallization margin of the generator's solution based on the measured solution concentration.

3. The wide-range adjustable absorption heat pump according to claim 1, characterized in that, The control parameters also include the internal parameters of the absorption heat pump, including the internal temperature of the generator solution. The automatic control system is further configured to determine the crystallization margin of the generator solution concentration based on the generator solution temperature and the generator solution concentration.

4. The wide-range adjustable absorption heat pump according to claim 3, characterized in that, The generator solution contains a thermometer, which transmits the measured solution temperature to the automatic control system.

5. The wide-range adjustable absorption heat pump according to claim 1, characterized in that, The absorption heat pump is a single-stage type, and the second outlet of the absorber is connected to the first inlet of the condenser through a heating water pipeline.

6. The wide-range adjustable absorption heat pump according to claim 1, characterized in that, The absorption heat pump is multi-stage, and the first water inlet of the condenser is connected to the first water outlet of the condenser of the previous stage absorption heat pump.

7. The wide-range adjustable absorption heat pump according to claim 1, characterized in that, A refrigerant circulation pipeline is also connected between the lower part and the upper part of the evaporator, and a refrigerant circulation pump is installed on the refrigerant circulation pipeline.

8. The wide-range adjustable absorption heat pump according to claim 1, characterized in that, The water vapor enters the condenser through a water vapor pipe after passing through the top of the generator. Specifically, the water vapor enters the condenser after passing through a baffle plate at the top of the generator.

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