A multi-stage evaporator system and a refrigerant water regulating method thereof

Abstract

The application provides a multi-stage evaporator system and a refrigerant water regulation method thereof, comprising a lower evaporator and an upper evaporator, wherein a first spray pipe for introducing refrigerant is arranged above a second heat exchange tube bundle in the upper evaporator; a plurality of refrigerant outlet pipes are arranged at the bottom end of the side of the upper evaporator in the height direction, each of the refrigerant outlet pipes is communicated with the lower evaporator, and a valve is arranged on each of the refrigerant outlet pipes except the topmost refrigerant outlet pipe; the multi-stage evaporator system can fully utilize the storage space of the water tray of the upper evaporator, eliminates the adverse effects of refrigerant overflow, liquid deficiency and the discontinuous operation of the refrigerant pump caused by the weight change of the refrigerant water due to the working condition fluctuation, and eliminates the load deviation caused by the enthalpy difference of the refrigerant water of the two-stage evaporator temperature and the spray of the refrigerant pump from the lower evaporator to the two-stage evaporator; and the vibration or noise problem caused by the connecting pipe of the refrigerant water of the upper evaporator to the lower evaporator is also eliminated.

Description

Technical Field

[0001] This invention relates to the field of multi-stage evaporator system technology, and in particular to a multi-stage evaporator system and a method for regulating the refrigerant water thereon. Background Technology

[0002] Currently, lithium bromide absorption heat pump units are widely used in various waste heat recovery fields. They are used to extract heat from circulating water, exhaust steam, slag flushing water, sewage, and geothermal water in power plants and industrial production processes to heat the heating network water for centralized heating or the hot water required by production processes. Compared to the internationally or domestically common operating parameters of chilled water (12 / 7) and cooling water (32 / 37) for refrigeration units, absorption heat pumps have a wide operating range. Especially in the field of centralized heating, because the temperature requirements of the heating network water differ greatly between the beginning and end of the cold season and the severe cold season, absorption heat pumps are required to have excellent adaptability to operating conditions and to operate efficiently and stably under various conditions. Because lithium bromide absorption heat pumps use lithium bromide solution and refrigerant water as the absorbent and refrigerant respectively, and operate in a closed loop, the lithium bromide solution exists in the generator and absorber, while the refrigerant water exists in the evaporator and condenser, primarily in the evaporator. When operating conditions change, the concentration of the lithium bromide solution changes accordingly. When the concentration increases, the weight of the lithium bromide solution decreases, and the amount of decrease is the concentrated refrigerant water, leading to an equal increase in the amount of refrigerant water. Conversely, when the concentration of the lithium bromide solution decreases, its weight increases, and this increase also comes entirely from the refrigerant water.

[0003] The lithium bromide solution and refrigerant water fluctuate in opposite directions. Since the refrigerant water is mainly stored in the evaporator liquid pan, the structural design requirement for variable operating conditions is that the evaporator water pan must have a sufficiently large capacity to adapt to fluctuations in the refrigerant water volume, ensuring that the refrigerant water does not overflow when the concentration is high and that the evaporator liquid pan does not lack water when the concentration is low.

[0004] When the temperature difference of the waste hot water exceeds 10℃ or the unit capacity is extremely large (e.g., single-stage cooling capacity exceeds 15MW), a two-stage absorption and two-stage evaporation process is generally used. The evaporator is divided into two evaporation stages to fully utilize the high evaporation temperature of the high-temperature stage, which helps to improve the unit's energy efficiency and reduce equipment costs. This type of two-stage evaporation process unit generally has a large capacity and a large demand for lithium bromide solution. Therefore, when the concentration changes, the weight fluctuation of the refrigerant will also be large. In conventional designs, the primary refrigerant water from the condenser enters the lower or upper evaporator. The refrigerant pump is located in the lower evaporator to distribute the refrigerant water that needs to be sprayed into the two-stage evaporators. The water that has not evaporated in the upper evaporator flows back to the lower evaporator. Therefore, the liquid storage space in the lower evaporator needs to be made large, and even an external refrigerant water tank is required. Meanwhile, the water pan in the upper evaporator hardly stores any water, and its liquid storage space is not utilized.

[0005] In addition, the above method has two drawbacks: First, the evaporation temperatures of the two evaporators are different, so the enthalpy of the refrigerant water is also different. When the lower evaporator is a low-temperature stage, the enthalpy of the refrigerant water from the upper evaporator of the high-temperature stage is large, which will increase the load on the lower evaporator. Conversely, when the lower evaporator is a high-temperature stage and the upper evaporator is a low-temperature stage, and the refrigerant pump is connected to the lower evaporator, the enthalpy of the refrigerant water sprayed from the lower evaporator to the upper evaporator is larger than the enthalpy corresponding to the evaporation temperature of the upper evaporator, which will correspondingly increase the load on the upper evaporator. Second, the connecting pipe from the upper evaporator to the lower evaporator is generally not a full-pipe flow, which will carry some air bubbles to the lower evaporator. The bursting of these air bubbles in the water pan of the lower evaporator will generate greater vibration or noise. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-stage evaporator system and its refrigerant water regulation method, so as to realize adaptive regulation of refrigerant water according to the unit load conditions.

[0007] This invention provides a multi-stage evaporator system, comprising a lower evaporator and an upper evaporator arranged vertically. The lower evaporator contains a first heat exchange tube bundle, and the upper evaporator contains a second heat exchange tube bundle. Above the second heat exchange tube bundle, the upper evaporator contains a first spray pipe for introducing refrigerant. Multiple refrigerant outlet pipes are spaced along the height direction at the bottom of the side of the upper evaporator, each of which is connected to the lower evaporator. Valves are installed on all refrigerant outlet pipes except the topmost one. A second spray pipe is located at the top of the lower evaporator and is connected to the bottom of the lower evaporator via a refrigerant pump. A third spray pipe is located at the top of the upper evaporator and is connected to the bottom of the upper evaporator via a refrigerant pump.

[0008] Furthermore, a level gauge is provided at the bottom end of the side of the lower evaporator.

[0009] Furthermore, the lower evaporator is provided with a refrigerant inlet, and multiple refrigerant outlet pipes are connected in parallel and communicate with the refrigerant inlet.

[0010] Furthermore, three refrigerant outlet pipes are provided at the bottom of the side of the upper evaporator, and valves are installed on the two lower refrigerant outlet pipes.

[0011] Furthermore, the valve is an electric valve, a solenoid valve, or a manual valve.

[0012] Furthermore, the refrigerant pump of the lower evaporator is connected to the bottom of the water pan of the lower evaporator, and the refrigerant pump of the upper evaporator is connected to the bottom of the water pan of the upper evaporator.

[0013] Furthermore, the refrigerant pump is a variable frequency refrigerant pump.

[0014] Furthermore, a liquid level sensor is provided at the bottom of the lower evaporator.

[0015] Furthermore, the third spray pipe is disposed between the first spray pipe and the second heat exchange tube bundle.

[0016] A refrigerant control method for a multi-stage evaporator system, implemented based on the multi-stage evaporator system, is as follows:

[0017] S1: When the unit load is high and the lithium bromide solution concentration is high, based on the liquid level information displayed by the liquid level gauge, close the valves on the refrigerant outlet pipe sequentially from low to high, and store the excess refrigerant water in the upper evaporator.

[0018] S2: When the unit load is low and the lithium bromide solution concentration is low, based on the liquid level information displayed by the liquid level gauge, open the valves on the refrigerant connection pipe in sequence from high to low, and put some of the refrigerant water originally stored in the upper evaporator into the lower evaporator.

[0019] The beneficial effects of this technical solution are as follows: This multi-stage evaporator system can make full use of the storage space of the upper evaporator water pan, eliminating the adverse effects of refrigerant overflow, liquid shortage, and refrigerant pump discontinuous operation caused by changes in refrigerant water weight due to fluctuations in operating conditions. In addition, the two evaporators are equipped with refrigerant pumps, eliminating the load deviation caused by the enthalpy difference of refrigerant water between the two evaporation stages due to the refrigerant pump spraying from the lower evaporator to the two evaporators. Furthermore, the installation of multiple refrigerant outlet pipes and their valves eliminates the vibration or noise problems caused by the connecting pipes from the upper evaporator to the lower evaporator. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific 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 from these drawings without creative effort.

[0021] Figure 1 This is a simplified structural diagram of the present invention.

[0022] Explanation of reference numerals in the attached drawings: 1-Upper evaporator, 2-Lower evaporator, 3-First spray pipe, 4-Refrigerant outlet pipe, 5-Valve, 6-Level gauge, 7-Refrigerant pump, 8-Second spray pipe, 9-Third spray pipe, 10-First heat exchange tube bundle, 11-Second heat exchange tube bundle. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and 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. Therefore, they should not be construed as limiting this invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Example 1

[0027] like Figure 1As shown, the present invention provides a multi-stage evaporator system, including a lower evaporator 2 and an upper evaporator 1 arranged vertically. The lower evaporator 2 contains a first heat exchange tube bundle 10, and the upper evaporator 1 contains a second heat exchange tube bundle 11. The first heat exchange tube bundle 10 and the second heat exchange tube bundle 11 are connected in series or in parallel. Above the second heat exchange tube bundle 11, a first spray pipe 3 for introducing refrigerant is provided inside the upper evaporator 1. Three refrigerant outlet pipes 4 are spaced apart along the height direction at the bottom end of the side of the upper evaporator 1. Each refrigerant outlet pipe 4 is connected to the lower evaporator 2. Except for the topmost refrigerant outlet pipe 4, all other refrigerant outlet pipes 4 are equipped with valves 5. The top of the interior of the lower evaporator 2 is provided with a second spray pipe 8, which is connected to the bottom of the water pan of the lower evaporator 2 through a refrigerant pump 7. The top of the interior of the upper evaporator 1 is provided with a third spray pipe 9, which is located between the first spray pipe 3 and the second heat exchange tube bundle 11. The third spray pipe 9 is connected to the bottom of the water pan of the upper evaporator 1 through a refrigerant pump 7.

[0028] A level gauge 6 is installed at the bottom of the side of the lower evaporator 2. It is used to detect the water level in the water pan inside the lower evaporator 2 and control the opening of the valve 5.

[0029] The lower evaporator 2 has a refrigerant inlet above the level gauge 6, and multiple refrigerant outlet pipes 4 are connected in parallel to the refrigerant inlet.

[0030] In this embodiment, valve 5 can be set as an electric valve, solenoid valve or manual valve, and refrigerant pump 7 is a variable frequency refrigerant pump 7.

[0031] The bottom of the lower evaporator 2 is equipped with a liquid level sensor. The refrigerant water can be intelligently regulated by an external controller based on the signal fed back by the liquid level sensor and the controller's control of the valve 5 opening.

[0032] In this embodiment, multiple refrigerant outlet pipes 4 are installed on the upper evaporator 1. Except for the topmost refrigerant outlet pipe 4, which does not have a valve 5, all other refrigerant outlet pipes 4 are equipped with valves 5. The topmost evaporator outlet pipe serves as the highest liquid level control point of the upper evaporator 1. The system operates by regulating the refrigerant water as follows: When the unit load is high and the solution concentration is high, the amount of refrigerant will increase. Based on the liquid level set by the level gauge 6, the valves 5 on the refrigerant outlet pipes 4 are closed sequentially from low to high, and the excess refrigerant water is stored in the water pan of the upper evaporator 1. When the unit load decreases and the solution concentration decreases, the amount of refrigerant water will decrease. Based on the liquid level set by the level gauge 6, the valves 5 on the refrigerant outlet pipes 4 are opened sequentially from high to low, and some of the refrigerant water originally stored in the upper evaporator 1 is placed into the water pan of the lower evaporator 2.

[0033] The two-stage evaporator system for refrigerant storage and control fully utilizes the water pan space of the upper evaporator 1, balancing refrigerant volume changes during fluctuations in operating conditions. This ensures that the refrigeration unit does not overflow or run out of liquid during varying operating conditions, guaranteeing the continuous and efficient operation of the refrigerant pump 7, and thus ensuring continuous and efficient unit operation. The multiple refrigerant outlet pipes 4 and their valves 5 ensure that the refrigerant water is always fully loaded when entering the lower evaporator 2, eliminating vibration or noise issues caused by the connecting pipes from the upper evaporator 1 to the lower evaporator 2.

[0034] The system can be expanded to multiple stages (≥3) of evaporators. The multiple stages of evaporators are also arranged from high to low. The primary refrigerant also enters the top stage evaporator first. The unevaporated refrigerant in the top stage evaporator is then replenished to the lower stages of evaporators. The upper stages of evaporators can also be equipped with multiple refrigerant outlet pipes 4 and valves 5 from high to low, which can make full use of the storage space of the water pans of the upper stages of evaporators.

[0035] 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 method for regulating refrigerant water in a multi-stage evaporator system, characterized in that, The system includes a lower evaporator and an upper evaporator arranged vertically. The lower evaporator contains a first heat exchange tube bundle, and the upper evaporator contains a second heat exchange tube bundle. Above the second heat exchange tube bundle, the upper evaporator has a first spray pipe for introducing refrigerant. Multiple refrigerant outlet pipes are spaced along the height direction at the bottom of the side of the upper evaporator, each of which is connected to the lower evaporator. Valves are installed on all refrigerant outlet pipes except the topmost one. A second spray pipe is located at the top of the lower evaporator and is connected to the bottom of the lower evaporator via a refrigerant pump. A third spray pipe is located at the top of the upper evaporator and is connected to the bottom of the upper evaporator via a refrigerant pump. The refrigerant water control method for this system is as follows: S1: When the unit load is high and the lithium bromide solution concentration is high, based on the liquid level information displayed by the liquid level gauge, close the valves on the refrigerant outlet pipe sequentially from low to high, and store the excess refrigerant water in the upper evaporator. S2: When the unit load is low and the lithium bromide solution concentration is low, based on the liquid level information displayed by the liquid level gauge, open the valves on the refrigerant connection pipe in sequence from high to low, and put some of the refrigerant water originally stored in the upper evaporator into the lower evaporator.

2. The refrigerant water control method for a multi-stage evaporator system according to claim 1, characterized in that, A level gauge is installed at the bottom of the side of the lower evaporator.

3. The refrigerant water control method for a multi-stage evaporator system according to claim 2, characterized in that, The lower evaporator is provided with a refrigerant inlet, and multiple refrigerant outlet pipes are connected in parallel and communicate with the refrigerant inlet.

4. The refrigerant water control method for a multi-stage evaporator system according to claim 3, characterized in that, The upper evaporator has three refrigerant outlet pipes at the bottom of its side, and valves are installed on the two lower refrigerant outlet pipes.

5. The refrigerant water control method for a multi-stage evaporator system according to claim 4, characterized in that, The valve is an electric valve, a solenoid valve, or a manual valve.

6. The refrigerant water control method for a multi-stage evaporator system according to claim 1, characterized in that, The refrigerant pump of the lower evaporator is connected to the bottom of the water pan of the lower evaporator, and the refrigerant pump of the upper evaporator is connected to the bottom of the water pan of the upper evaporator.

7. The refrigerant water control method for a multi-stage evaporator system according to claim 6, characterized in that, The refrigerant pump is a variable frequency refrigerant pump.

8. The refrigerant water control method for a multi-stage evaporator system according to claim 1, characterized in that, A liquid level sensor is installed at the bottom of the lower evaporator.

9. The refrigerant water control method for a multi-stage evaporator system according to claim 1, characterized in that, The third spray pipe is disposed between the first spray pipe and the second heat exchange tube bundle.

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