Multi-stage evaporator system and refrigerant water regulation and control method thereof

Abstract

The invention provides a multi-stage evaporator system and a refrigerant water regulation and control method thereof. The multi-stage evaporator system comprises a lower evaporator and an upper evaporator, and a first spraying pipe used for introducing a refrigerant is arranged at the position, 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 face of the upper evaporator in the height direction at intervals, each refrigerant outlet pipe is communicated with the lower evaporator, and valves are installed on the other refrigerant outlet pipes except the refrigerant outlet pipe at the topmost end. According to the multi-stage evaporator system, the storage space of the upper evaporator water disc can be fully utilized, and the adverse effects of refrigerant overflow, liquid shortage, non-continuous operation of refrigerant pumps and the like caused by refrigerant water weight change due to working condition fluctuation are eliminated; the load deviation caused by the enthalpy difference of refrigerant water at the two-stage evaporation temperature due to the fact that a refrigerant pump arranged on the lower evaporator sprays to the two-stage evaporator is eliminated; and the problem of vibration or noise generated by a connecting pipe from the refrigerant water of the upper evaporator to the lower evaporator is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-stage evaporator systems, and in particular to a multi-stage evaporator system and a refrigerant water control method thereof. Background Art

[0002] At present, lithium bromide absorption heat pump units are widely used in various waste heat recovery fields, and are used to extract the heat of circulating water, exhaust steam, slag water, sewage, and geothermal water in power plants and industrial production processes to heat the hot water network water for centralized heating or hot water required by production processes. Compared with the international or domestic general operating parameters of 12 / 7 for chilled water and 32 / 37 for cooling water of refrigerators, the operating range of absorption heat pumps is very wide, especially when used in the field of centralized heating. Since the demand for hot water temperature in the early and late cold periods and severe cold periods is very different, absorption heat pumps are required to have good adaptability to operating conditions and can operate efficiently and stably under various operating conditions. Since the lithium bromide absorption heat pump uses lithium bromide solution and refrigerant water as absorbent and refrigerant respectively, and it is a closed cycle, the lithium bromide solution exists in the generator and absorber, while the refrigerant water exists in the evaporator and condenser, and mainly in the evaporator; when the operating conditions change, the concentration of the corresponding lithium bromide solution will change. When the concentration becomes higher, the weight of the lithium bromide solution will decrease. The reduced amount is the concentrated refrigerant water, which will cause the refrigerant water to increase by the same amount. On the contrary, when the concentration of the lithium bromide solution becomes dilute, its weight will increase, and the increase is also entirely from the refrigerant water.

[0003] The lithium bromide solution and refrigerant water increase and decrease at the expense of each other. Since the refrigerant water is mainly stored in the evaporator liquid pan, the variable operating conditions require that the evaporator water pan have a large enough capacity to adapt to the fluctuation of the refrigerant water volume, so that the refrigerant water does not overflow at high concentrations and the evaporator liquid pan does not lack water at low concentrations.

[0004] When the temperature difference of the waste hot water exceeds 10℃ or the unit capacity is very large (for example, the single-stage cooling capacity exceeds 15MW), a two-stage absorption and two-stage evaporation process is generally used to divide the evaporator into two stages of evaporation, making full use of the advantage of the high evaporation temperature in the high-temperature stage, which is beneficial to improving the unit energy efficiency and reducing the equipment cost; this 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. The conventional design generally has the primary refrigerant water from the condenser enter the lower or upper evaporator, and the refrigerant pump is set in the lower evaporator to distribute the refrigerant water that needs to be sprayed with liquid to the two-stage evaporator, and the unevaporated water in the upper evaporator flows to the lower evaporator. Therefore, it is necessary to enlarge the liquid storage space of the lower evaporator, and even require an external refrigerant water tank, while the upper evaporator water pan hardly stores water, and its liquid storage space is not utilized.

[0005] In addition, the above method has two disadvantages: one is that the evaporation temperatures of the two-stage evaporators are different, so the enthalpy values ​​of the refrigerant water are also different. When the lower evaporator is a low-temperature stage, the enthalpy value of the refrigerant water from the upper evaporator of the high-temperature stage is large, which will increase the load of the lower evaporator. Conversely, when the lower evaporator is a high-temperature stage and the upper evaporator is a low-temperature stage, the refrigerant pump is connected to the lower evaporator, and the enthalpy value of the refrigerant water sprayed from the lower evaporator to the upper evaporator is larger than the enthalpy value corresponding to the evaporation temperature of the upper evaporator, which increases the load of the upper evaporator accordingly; the second is that the connecting pipe from the refrigerant water of the upper evaporator to the lower evaporator is generally a non-full pipe flow, which will bring some bubbles to the lower evaporator. These bubbles will burst in the water pan of the lower evaporator and produce large vibrations or noise. Summary of the invention

[0006] The object of the present invention is to provide a multi-stage evaporator system and a refrigerant water control method thereof, so as to realize adaptive control of the refrigerant water according to the load condition of the unit.

[0007] The present invention provides a multi-stage evaporator system, comprising a lower evaporator and an upper evaporator arranged in an upper and lower manner, wherein a first heat exchange tube bundle is provided inside the lower evaporator, and a second heat exchange tube bundle is provided inside the upper evaporator; a first spray pipe for introducing refrigerant is provided above the second heat exchange tube bundle inside the upper evaporator; a plurality of refrigerant outlet pipes are provided at intervals along the height direction at the bottom end position of the side surface of the upper evaporator, each of the refrigerant outlet pipes is connected to the lower evaporator, and valves are installed on the remaining refrigerant outlet pipes except the topmost refrigerant outlet pipe; a second spray pipe is provided at the top end of the lower evaporator, and the second spray pipe is connected to the bottom end of the lower evaporator through a refrigerant pump; a third spray pipe is provided at the top end of the upper evaporator, and the third spray pipe is connected to the bottom end of the upper evaporator through a refrigerant pump.

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

[0009] Furthermore, a refrigerant inlet is provided on the lower evaporator, and a plurality of refrigerant outlet pipes are connected in parallel and communicated with the refrigerant inlet.

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

[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 communicated with the bottom of the water pan of the lower evaporator, and the refrigerant pump of the upper evaporator is communicated with 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 end of the lower evaporator.

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

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

[0017] S1: When the unit load is large and the concentration of lithium bromide solution is high, combined with the liquid level information displayed by the liquid level gauge, the valves on the refrigerant outlet pipe are closed in order from low to high, and the excess refrigerant water is stored in the upper evaporator;

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

[0019] The beneficial effects of the technical solution are as follows: the multi-stage evaporator system can make full use of the storage space of the upper evaporator water pan, eliminating adverse effects such as refrigerant overflow, liquid shortage and inability of the refrigerant pump to run continuously caused by changes in the weight of the refrigerant water due to operating condition fluctuations. The other two evaporators are respectively equipped with refrigerant pumps, eliminating the load deviation caused by the enthalpy difference of the refrigerant water in the two-stage evaporation temperature due to the refrigerant pump configured from the lower evaporator spraying to the two-stage evaporator; in addition, through the arrangement of multiple refrigerant outlet pipes and their valves, the problem of vibration or noise generated by the connecting pipe from the upper evaporator refrigerant water to the lower evaporator is eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

[0022] Explanation of the accompanying drawings: 1-upper evaporator, 2-lower evaporator, 3-first spray pipe, 4-refrigerant outlet pipe, 5-valve, 6-liquid 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 DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0025] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] Example 1

[0027] like Figure 1As shown, the present invention provides a multi-stage evaporator system, comprising a lower evaporator 2 and an upper evaporator 1 arranged in an upper and lower manner, a first heat exchange tube bundle 10 is provided inside the lower evaporator 2, a second heat exchange tube bundle 11 is provided inside the upper evaporator 1, and the first heat exchange tube bundle 10 and the second heat exchange tube bundle 11 are connected in series or in parallel with each other; a first spray pipe 3 for introducing refrigerant is provided above the second heat exchange tube bundle 11 inside the upper evaporator 1; three refrigerant outlet pipes 4 are provided at intervals along the height direction at the bottom end position of the side surface of the upper evaporator 1 , each refrigerant outlet pipe 4 is connected to the lower evaporator 2, and valves 5 are installed on the other refrigerant outlet pipes 4 except the top refrigerant outlet pipe 4; a second spray pipe 8 is provided at the top of the lower evaporator 2, and the second spray pipe 8 is connected to the bottom of the water pan of the lower evaporator 2 through a refrigerant pump 7; a third spray pipe 9 is provided at the top of the upper evaporator 1, and the third spray pipe 9 is arranged between the first spray pipe 3 and the second heat exchange tube bundle 11, and 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 liquid level gauge 6 is provided at the bottom of the side of the lower evaporator 2. It is used to detect the liquid level of the water pan in the lower evaporator 2 and control the opening of the valve 5.

[0029] A refrigerant inlet is provided on the lower evaporator 2 above the liquid level gauge 6, and a plurality of refrigerant outlet pipes 4 are connected in parallel and communicated with the refrigerant inlet.

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

[0031] A liquid level sensor is provided at the bottom of the lower evaporator 2 , and the intelligent regulation of the refrigerant water can be achieved through an external controllable device according to the signal fed back by the liquid level sensor and the control of the opening of the valve 5 by the controller.

[0032] In this embodiment, on the multiple refrigerant outlet pipes 4 arranged on the upper evaporator 1, except for the topmost refrigerant outlet pipe 4 which is not provided with a valve 5, the other refrigerant outlet pipes 4 are all provided with valves 5. The evaporator outlet pipe located at the top is used as the highest liquid level control point of the upper evaporator 1. The control method for refrigerant water during operation of the system is as follows: when the unit load is large and the solution concentration is high, the amount of refrigerant will increase, and the valves 5 on the refrigerant outlet pipes 4 are closed from low to high according to the liquid level set by the liquid level gauge 6, 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, and the valves 5 on the refrigerant outlet pipes 4 are opened from high to low according to the liquid level set by the liquid level gauge 6, and part of the refrigerant water originally stored in the upper evaporator 1 is placed in the water pan of the lower evaporator 2.

[0033] The method of using two-stage evaporators for refrigerant storage and control makes full use of the water pan space of the upper evaporator 1, balances the change of refrigerant water volume when the working condition fluctuates, ensures that the refrigerator does not overflow or lack liquid when the working condition changes, ensures the continuous and efficient operation of the refrigerant pump 7, and thus ensures the continuous and efficient operation of the unit. Through the arrangement of multiple refrigerant outlet pipes 4 and their valves 5, the refrigerant water is in a full pipe state when entering the lower evaporator 2, eliminating the vibration or noise problem of the connecting pipe from the upper evaporator 1 to the lower evaporator 2.

[0034] The system can be expanded to a multi-stage (≥3) evaporator, and the multi-stage evaporator is also arranged from high to low. The primary refrigerant also enters the uppermost evaporator first, and the unevaporated refrigerant in the uppermost evaporator is replenished in turn to the lower evaporators. The upper evaporators can also be provided with multiple refrigerant outlet pipes 4 and valves 5 from high to low, so as to make full use of the storage space of the water pans of the upper evaporators.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 multi-stage evaporator system, characterized in that: It comprises a lower evaporator and an upper evaporator which are arranged in an upper and lower manner, the lower evaporator is provided with a first heat exchange tube bundle, and the upper evaporator is provided with a second heat exchange tube bundle; the upper evaporator is provided with a first spray pipe for introducing refrigerant above the second heat exchange tube bundle; a plurality of refrigerant outlet pipes are provided at intervals along the height direction at the bottom end position of the side surface of the upper evaporator, each of the refrigerant outlet pipes is connected to the lower evaporator, and valves are installed on the remaining refrigerant outlet pipes except the topmost refrigerant outlet pipe; a second spray pipe is provided at the top end of the lower evaporator, and the second spray pipe is connected to the bottom end of the lower evaporator through a refrigerant pump; a third spray pipe is provided at the top end of the upper evaporator, and the third spray pipe is connected to the bottom end of the upper evaporator through a refrigerant pump.

2. The multi-stage evaporator system according to claim 1, characterized in that: A liquid level gauge is provided at the bottom end of the side surface of the lower evaporator.

3. The multi-stage evaporator system according to claim 2, characterized in that: The lower evaporator is provided with a refrigerant inlet, and a plurality of refrigerant outlet pipes are connected in parallel and communicated with the refrigerant inlet.

4. The multi-stage evaporator system according to claim 3, characterized in that: Three refrigerant outlet pipes are arranged at the bottom end of the side surface of the upper evaporator, and valves are installed on the two refrigerant outlet pipes located at the bottom.

5. The 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 multi-stage evaporator system according to claim 1, characterized in that The refrigerant pump of the lower evaporator is communicated with the bottom of the water pan of the lower evaporator, and the refrigerant pump of the upper evaporator is communicated with the bottom of the water pan of the upper evaporator.

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

8. The multi-stage evaporator system according to claim 1, characterized in that A liquid level sensor is arranged at the bottom end of the lower evaporator.

9. The multi-stage evaporator system according to claim 1, characterized in that The third spray pipe is arranged between the first spray pipe and the second heat exchange tube bundle.

10. A refrigerant water control method for a multi-stage evaporator system, characterized in that: Based on the multi-stage evaporator system described in any one of claims 1 to 9, the specific control method is as follows: S1: When the unit load is large and the concentration of lithium bromide solution is high, combined with the liquid level information displayed by the liquid level gauge, the valves on the refrigerant outlet pipe are closed in order from low to high, and the excess refrigerant water is stored in the upper evaporator; S2: When the unit load is small and the concentration of lithium bromide solution is low, based on the liquid level information displayed by the liquid level gauge, open the valves on the refrigerant pipes in sequence from high to low to release part of the refrigerant water originally stored in the upper evaporator into the lower evaporator.

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