Absorption type refrigeration system

Abstract

To provide an absorption type refrigeration system capable of suppressing increase in electric power consumption and shortening of a service life of a pump.SOLUTION: An absorption type refrigeration system includes: water supply piping 24 for sending out cooling water to a lower water tank 23; a float valve 25 for opening / closing the water supply piping 24; a water level sensor 26 for detecting a water level of the lower water tank 23; a control device that stops a cooling water pump P when a water level detected by the water level sensor 26 is lower than a first level, and starts an operation of the cooling water pump P when the water level detected through the water level sensor 26 is equal to or higher than a second level exceeding the first level; and second water supply piping 27 provided separately from the water supply piping 24 to send out the cooling water to the lower water tank 23. When stop frequency or operation start frequency of the cooling water pump P reaches predetermined frequency or more, the control device reduces a pressure-feed amount of the cooling water to be pressure-fed per unit time by the cooling water pump P.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an absorption refrigeration system. [Background technology]

[0002] Conventionally, there has been known an absorption refrigeration system having an absorption chiller (including an absorption chiller / heater with a heating function) and a cooling tower that supplies cooling water to the absorption chiller (see, for example, Patent Document 1). In this absorption refrigeration system, when the absorption chiller is installed or when switching from heating operation to cooling operation, water filling is performed to fill the water passage part in the absorption chiller with cooling water. The absorption refrigeration system is equipped with a pump that pressure-feeds cooling water from the cooling tower to the absorption chiller, and when water filling is performed, cooling water is sent from the cooling tower to the absorption chiller by the pump to fill the water passage part with cooling water. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-2296 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional absorption refrigeration systems, the pump has to be started and stopped repeatedly when filling the refrigeration tank with water. This causes a large amount of power consumption and shortens the life of the pump.

[0005] The present invention has been made to solve such problems, and an object of the present invention is to provide an absorption refrigeration system that can suppress an increase in power consumption and a shortening of the pump's lifespan. [Means for solving the problem]

[0006] The absorption refrigeration system of the present invention comprises an absorption chiller, a cooling tower which supplies cooling water to a water passage section of the absorption chiller, and a pump which serves as a power source for sending cooling water in a water tank provided in the cooling tower to the absorption chiller, and which fills the water passage section with cooling water from a state in which the water passage section is not filled with cooling water. The absorption refrigeration system comprises a water supply pipe for taking cooling water into the water tank, a float valve which takes cooling water into the water tank through the water supply pipe when the water level in the water tank is below a predetermined level, a water level sensor for detecting the water level of the water tank, and control means which stops the pump when the water level detected by the water level sensor is below a first level and operates the pump when the water level detected by the water level sensor is at or above a second level that is higher than the first level, and the control means reduces the amount of cooling water pumped by the pump per unit time when the number of times the pump has stopped or started operation reaches or exceeds a predetermined number. Effect of the Invention

[0007] According to the present invention, it is possible to provide an absorption refrigeration system capable of suppressing an increase in power consumption and a shortened life of a pump. [Brief description of the drawings]

[0008] [Figure 1] 1 is a configuration diagram showing an absorption refrigeration system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a configuration diagram showing the vicinity of the lower water tank of the cooling tower shown in FIG. [Diagram 3] 4 is a flowchart showing a control process of the control device according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be described below along with preferred embodiments. Note that the present invention is not limited to the embodiments shown below, and can be modified as appropriate within the scope of the present invention. In addition, in the embodiments shown below, some configurations are omitted from illustration and description, but it goes without saying that publicly known or well-known technologies are appropriately applied to the details of the omitted technologies within the scope of no contradiction with the contents described below.

[0010] Fig. 1 is a configuration diagram showing an absorption refrigeration system according to this embodiment. As shown in Fig. 1, the absorption refrigeration system 1 includes an absorption chiller 10, a cooling tower 20, a cooling water pump (pump) P, a control device (control means) 30, and first and second circulation pipes L1 and L2. The first circulation pipe L1 is a pipe for sending the cooling water of the cooling tower 20 to the absorption chiller 10. The second circulation pipe L2 is a pipe for returning the cooling water from the absorption chiller 10 to the cooling tower 20. The cooling water pump P is provided in the first circulation pipe L1 and serves as a power source for sending the cooling water of the cooling tower 20 to the absorption chiller 10.

[0011] The absorption chiller 10 has a circulation cycle consisting of an evaporator, an absorber, a regenerator and a condenser, and cools the refrigerant by this circulation cycle. Such an absorption chiller 10 is equipped with a water passing section 11. The water passing section 11 is for passing cooling water discharged from a cooling tower 20 through the absorption chiller 10, and is a section through which the cooling water flows when the absorption chiller 10 is filled with cooling water during cooling operation.

[0012] The water passage section 11 includes a first water passage section 11a and a second water passage section 11b. The first water passage section 11a is connected to the first circulation pipe L1 at its upstream side and to the second water passage section 11b at its downstream side. The second water passage section 11b is connected to the first water passage section 11a at its upstream side and to the second circulation pipe L2 at its downstream side.

[0013] The first water passage 11a is provided, for example, in the absorber, and serves to liquefy the refrigerant vapor evaporated in the evaporator. The second water passage 11b is provided, for example, in the condenser, and serves to liquefy the refrigerant vapor evaporated in the regenerator.

[0014] Such a water passage section 11 takes in cooling water from the cooling tower 20 through the first circulation piping L1, and returns the cooling water to the cooling tower 20 again through the second circulation piping L2 after being used in the first and second water passage sections 11a and 11b. Note that, although the absorption refrigeration system 1 in the example shown in Fig. 1 includes an absorption chiller 10 having a cooling function, this absorption chiller 10 may also be an absorption chiller / heater further having a heating function.

[0015] The cooling tower 20 supplies cooling water to the absorption chiller 10, and includes an upper water tank 21, a filler 22, and a lower water tank (water tank) 23.

[0016] The upper water tank 21 temporarily stores the cooling water returning from the absorption chiller 10. The upper water tank 21 also includes a spray unit (not shown) that sprays the temporarily stored cooling water onto the filler 22. The filler 22 lowers the cooling water temperature by exposing the cooling water sprayed from the upper water tank 21 to the outside air. The lower water tank 23 temporarily stores the cooling water whose temperature has been lowered by passing through the filler 22.

[0017] Fig. 2 is a configuration diagram showing the vicinity of the lower water tank 23 of the cooling tower 20 shown in Fig. 1. As shown in Fig. 2, the cooling tower 20 further includes a water supply pipe 24, a float valve 25, and a water level sensor 26. In addition, as shown in Fig. 2, a first circulation pipe L1 is connected to the vicinity of the lower end of the lower water tank 23.

[0018] The water supply pipe 24 is connected to, for example, a water pipe or the like, and serves to send cooling water to the lower water tank 23. The float valve 25 opens and closes the water supply pipe 24. When the water level in the lower water tank 23 is below a predetermined level, the float valve 25 opens the water supply pipe 24 to take in cooling water into the lower water tank 23. On the other hand, when the water level in the lower water tank 23 exceeds the predetermined level, the float valve 25 closes the water supply pipe 24 to prohibit the cooling water from flowing into the lower water tank 23. Here, the predetermined level is higher than a second level and lower than a third level, which will be described later.

[0019] The water level sensor 26 detects the water level of the lower water tank 23, and has a first contact 26a and a second contact 26b. The first contact 26a is for determining whether the water level is equal to or higher than a first level. When the first contact 26a is immersed in water, the water level sensor 26 outputs a signal to that effect to the control device 30 (see FIG. 1). The first level is set to a height that prevents air from entering the first circulation pipe L1.

[0020] The second contact 26b is for determining whether the water level is equal to or higher than a second level that exceeds the first level. When the second contact 26b is immersed in water, the water level sensor 26 outputs a signal to that effect to the control device 30.

[0021] Here, the control device 30 has a function of determining the water level based on a signal from the water level sensor 26, and controls the operation of the cooling water pump P according to the water level. That is, when the control device 30 determines that the water level is below the first level based on the signal from the water level sensor 26, it stops the cooling water pump P to prevent air from being trapped in the cooling water pump P. In addition, once the control device 30 stops the cooling water pump P, it keeps the cooling water pump P stopped until it can determine that the water level has reached the second level or higher based on the signal from the water level sensor 26, and starts the operation of the cooling water pump P when it determines that the water level has reached the second level.

[0022] Here, in the absorption refrigeration system 1, the water passage section 11 of the absorption chiller 10 before installation or during heating operation is not filled with cooling water. For this reason, when the absorption chiller 10 is installed or when switching from heating operation to cooling operation, the absorption refrigeration system 1 fills the water passage section 11 with cooling water. However, the control device 30 may repeatedly start and stop the cooling water pump P during water filling.

[0023] That is, during water filling, cooling water is taken into the lower water tank 23 from the water supply pipe 24, but the amount of cooling water pumped by the cooling water pump P is sufficiently larger than the amount of cooling water supplied from the water supply pipe 24, so that the water level frequently alternates between being below the first level and being above the second level. In particular, if the water level repeatedly alternates between being below the first level and being above the second level, the cooling water pump P will be started and stopped frequently, for example, several hundred times, until water filling is complete. As a result, the absorption refrigeration system 1 consumes a lot of power due to the starting and stopping, and the pump life is shortened.

[0024] Therefore, in the absorption refrigeration system 1 according to this embodiment, an inverter I is provided in the cooling water pump P. In this embodiment, the control device 30 is configured to control the rotation speed of the cooling water pump P by controlling the frequency of the inverter I. This enables the control device 30 to control the amount of cooling water pumped by the cooling water pump P per unit time.

[0025] Furthermore, the control device 30 has a function of counting the number of times the cooling water pump P stops or starts during water filling (e.g., from the start of water filling or per unit time). In this embodiment, the control device 30 reduces the operating frequency of the cooling water pump P when the number of times the cooling water pump P stops or starts during water filling reaches a predetermined number or more. This reduces the amount of cooling water pumped per unit time by the cooling water pump P, making it possible to approach the amount of cooling water supplied from the water supply piping 24. Therefore, it is difficult for the water level to easily fall below the first level, making it difficult for the cooling water pump P to start and stop repeatedly.

[0026] When reducing the pumping rate of the cooling water pump P, the control device 30 preferably reduces it to a level that matches the amount of water supplied to the lower water tank 23 (for example, the difference between the two is within 5%). This is because it is possible to further reduce the number of starts and stops.

[0027] Here, it is preferable that the control device 30 sufficiently reduces the pumping rate of the cooling water pump P, for example, to the extent that the pumping rate of the cooling water pump P matches the amount of water supplied to the lower water tank 23. However, the cooling water pump P must have enough power to pump the cooling water from at least the first water passage part 11a through the second water passage part 11b to the upper water tank 21, and there is a limit to how much the pumping rate can be reduced. In particular, when the capacity of the water passage part 11 becomes large due to the capacity of the absorption chiller 10 or the like, it becomes difficult to sufficiently reduce the pumping rate of the cooling water pump P relative to the amount of water supplied to the lower water tank 23 through the water supply pipe 24.

[0028] Therefore, the cooling tower 20 according to this embodiment preferably includes a second water supply pipe 27. The second water supply pipe 27 is provided separately from the water supply pipe 24, and is for sending cooling water to the lower water tank 23 at least when the tank is filled with water. The second water supply pipe 27 is provided with a control valve 27a for opening and closing the flow path.

[0029] In this embodiment, the control device 30 further has a function of controlling the opening and closing of the control valve 27a. When the number of times the cooling water pump P is stopped or started during water filling reaches or exceeds a predetermined number, the control device 30 opens the control valve 27a to open the second water supply pipe 27 and start the delivery of cooling water from the second water supply pipe 27.

[0030] This increases the amount of water supplied to the lower water tank 23, and makes it easier to bring the pumping volume of the cooling water pump P and the amount of water supplied to the lower water tank 23 closer to each other, even if there is a limit to how much the cooling water pump P can reduce.

[0031] Furthermore, the cooling tower 20 according to this embodiment preferably includes an overflow pipe 28. The overflow pipe 28 discharges the cooling water when the water level in the lower water tank 23 reaches a third level that exceeds the second level. This overflow pipe 28 prevents the cooling water from overflowing from the lower water tank 23. Here, the third level is a water level higher than a predetermined level.

[0032] The amount of cooling water discharged per unit time from the overflow pipe 28 is set to be equal to or greater than the amount of cooling water flowing into the lower water tank 23 per unit time through the water supply pipe 24 and the second water supply pipe 27. This ensures that the overflow pipe 28 can ensure a sufficient discharge amount even if the float valve 25, the control valve 27a, or the cooling water pump P fails, thereby preventing the cooling water from overflowing from the lower water tank 23.

[0033] Fig. 3 is a flowchart showing the control of the control device 30 according to this embodiment. The flowchart shown in Fig. 3 is executed at the start of water filling. First, the control device 30 turns on the cooling water pump P (starts operation) (S1). After that, the control device 30 sets the frequency of the cooling water pump P to a first frequency (S2).

[0034] Next, the control device 30 judges whether the water level is equal to or higher than the first level (S3). If the water level is equal to or higher than the first level (S3: YES), the process proceeds to step S9. On the other hand, if the water level is not equal to or higher than the first level (S3: NO), the control device 30 turns off (stops) the cooling water pump P (S4).

[0035] Thereafter, the control device 30 judges whether the water level is equal to or higher than the second level (S5). If the water level is not equal to or higher than the second level (S5: NO), this process is repeated until the water level becomes equal to or higher than the second level.

[0036] If the water level is equal to or higher than the second level (S5: YES), the control device 30 judges whether the number of times the water level has fallen below the first level is equal to or higher than a predetermined number of times (S6). That is, the control device 30 judges whether the number of times the cooling water pump P has stopped is equal to or higher than a predetermined number of times. In addition, in step S6, the control device 30 may judge whether the number of times the water level has fallen to or higher than the second level, i.e., the number of times the cooling water pump P has started to operate is equal to or higher than a predetermined number of times. Furthermore, in step S6, the control device 30 may judge whether the number of times the water level has fallen below the first level during a certain time (unit time) is equal to or higher than a predetermined number of times. Similarly, the control device 30 may judge whether the number of times the water level has fallen to or higher than the second level during a certain time is equal to or higher than a predetermined number of times.

[0037] If the number of times the water level has fallen below the first level is not equal to or greater than the predetermined number (S6: NO), the process proceeds to step S3. On the other hand, if the number of times the water level has fallen below the first level is equal to or greater than the predetermined number (S6: YES), the control device 30 opens the control valve 27a (S7). That is, the control device 30 starts supplying water from the second water supply pipe 27. Next, the control device 30 sets the frequency of the cooling water pump P to a second frequency lower than the first frequency (S8). This reduces the pumping rate of the cooling water pump P. Then, the process proceeds to step S9.

[0038] Next, the control device 30 turns on the cooling water pump P (S9). After that, the control device 30 judges whether a predetermined time has continuously elapsed since the water level became equal to or higher than the first level (S10). If the predetermined time has not continuously elapsed since the water level became equal to or higher than the first level (S10: NO), the process proceeds to step S3.

[0039] On the other hand, if a predetermined time has passed continuously since the water level reached or exceeded the first level (S10: YES), the control device 30 determines that a certain amount or more of cooling water is returning from the absorption chiller 10 because the water level has not decreased. In other words, the control device 30 determines that water filling is complete.

[0040] As a result, the control device 30 closes the second water supply pipe 27 by closing the control valve 27a (S11), and returns the setting of the frequency of the cooling water pump P to the first frequency (S12). Next, the cooling water pump P is turned off (S13). Then, the process shown in FIG. 3 ends.

[0041] In this way, according to the absorption refrigeration system 1 of this embodiment, when the number of times the cooling water pump P stops or starts operation reaches a predetermined number or more, the amount of cooling water pumped per unit time by the cooling water pump P is reduced. This makes it difficult for the water level in the lower water tank 23 to drop when filled with water, and reduces the frequency with which the water level falls below the first level and the cooling water pump P stops. Therefore, it is possible to provide an absorption refrigeration system 1 that can reduce the number of times the cooling water pump P starts and stops.

[0042] Furthermore, cooling water is supplied to the lower water tank 23 not only from the water supply pipe 24 but also from the second water supply pipe 27. Therefore, even if cooling water is sent to the absorption chiller 10 by the cooling water pump P, the water level in the lower water tank 23 becomes even less likely to drop. This makes it even more difficult for the water level to fall below the first level, and makes it even more difficult for the cooling water pump P to stop. Therefore, it is possible to provide an absorption chiller system 1 that can further reduce the number of times the cooling water pump P is started and stopped.

[0043] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and modifications may be made without departing from the spirit of the present invention, and other well-known and publicly known technologies may be combined to the extent possible. [Explanation of symbols]

[0044] 1: Absorption refrigeration system 10: Absorption chiller 11: Water flow section 20: Cooling tower 23: Lower tank (tank) 24: Water supply pipe 25: Float valve 26: Water level sensor 27: Second water supply pipe 28: Overflow piping 30: Control device (control means) P: Cooling water pump (pump)

Claims

1. An absorption refrigeration system comprising: an absorption chiller; a cooling tower which supplies cooling water to a water passage section of the absorption chiller; and a pump which serves as a power source for sending cooling water in a water tank provided in the cooling tower to the absorption chiller, the absorption refrigeration system performing water filling to fill the water passage section with cooling water from a state in which the water passage section is not filled with cooling water, A water supply pipe for taking cooling water into the water tank; a float valve that draws cooling water into the water tank through the water supply pipe when the water level in the water tank is equal to or lower than a predetermined level; a water level sensor for detecting the water level of the water tank; a control means for stopping the pump when the water level detected by the water level sensor is below a first level, and for operating the pump when the water level detected by the water level sensor is equal to or higher than a second level that is higher than the first level; The control means reduces the amount of cooling water pumped by the pump per unit time when the number of times the pump is stopped or started reaches a predetermined number or more. An absorption refrigeration system.

2. A second water supply pipe is provided separately from the water supply pipe, and is used to take in cooling water into the water tank. The control means controls the intake of cooling water into the water tank through the second water supply pipe in addition to the water supply pipe when the number of times the pump is stopped or started reaches the predetermined number of times.

2. The absorption refrigeration system according to claim 1 .

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