A high outlet water temperature chiller and control method thereof

Abstract

The invention relates to the technical field of chillers, and discloses a high-outlet-water-temperature chiller and a control method thereof, wherein the high-outlet-water-temperature chiller consists of 4 screw compressors, 4 condensers, 3 heat recovery devices, 2 evaporators, 4 antifreeze switches, 4 refrigerant pipelines, 1 hot water pipeline and 1 chilled water pipeline; the high-outlet-water-temperature chiller and the control method thereof provided by the invention can fully recycle and utilize the condensation heat of each compressor system to achieve energy saving, and can also realize the function of using one chiller to simultaneously produce cold water for air conditioning and hot water for domestic use, thereby achieving the dual goals of one machine with multiple uses and energy saving.

Description

Technical Field

[0001] The invention belongs to the technical field of chillers, and in particular relates to a high outlet water temperature chiller and a control method thereof. Background Art

[0002] According to the requirements of the national standard GB / T18430, ordinary heat pump chillers usually produce 45-degree hot water under nominal working conditions. This hot water temperature can only be provided to the hot water coil of the terminal unit for indoor air heating, and only hot water or cold water can be produced at the same time, and hot water and cold water cannot be produced together. For places such as large hotels that need to use a large amount of domestic hot water, on the one hand, hot water of about 60 degrees is needed for the domestic water needs of guests, and on the other hand, chilled water of about 7 degrees is needed for room air cooling needs. The existing technology usually uses two systems to meet the above requirements. One system consists of ordinary air-cooled (water-cooled) chillers plus terminal equipment such as fan coils, which is mainly responsible for providing cold sources for indoor air; the other system consists of boilers and hot water pipes, which is mainly responsible for providing domestic hot water for hotels and hotel rooms. As the largest energy consumer in modern buildings, the cold source and heat source systems have accounted for nearly 40% of the total energy consumption of buildings. This shows that the large-scale application of energy-saving measures and technologies of cold and heat source systems in the field of construction has become the most urgent social demand and has great potential.

[0003] How to make full use of the condensing heat of the chiller to achieve energy saving in places such as large hotels where a large amount of domestic hot water is needed, and to solve the problems of both cold water for air conditioning and domestic hot water with only one central air-conditioning system, is the main problem that current technology needs to solve.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] In view of the above-mentioned deficiencies of the prior art, an object of the present invention is to provide a high outlet water temperature chiller and a control method thereof, aiming to solve the problem that the prior art cannot simultaneously produce cold water for air conditioning and hot water for domestic use based on a single chiller.

[0006] The technical solution of the present invention is as follows:

[0007] A high outlet water temperature chiller, comprising: a first evaporator and a second evaporator connected through a chilled water pipeline, a first screw compressor, a first heat recovery device and a first condenser connected in sequence with the first evaporator through a first refrigerant pipeline to form a circulation path, a second screw compressor, a second heat recovery device and a second condenser connected in sequence with the first evaporator through a second refrigerant pipeline to form a circulation path; a third screw compressor, a third heat recovery device and a third condenser connected in sequence with the second evaporator through a third refrigerant pipeline to form a circulation path, a fourth screw compressor, a fourth heat recovery device and a fourth condenser connected in sequence with the second evaporator through a fourth refrigerant pipeline to form a circulation path; the first condenser, the first heat recovery device, the second condenser, the second heat recovery device, the third condenser, the third heat recovery device, the fourth condenser and the fourth heat recovery device are connected in series in sequence through a hot water pipeline; a first antifreeze switch is provided on the first refrigerant pipeline; a second antifreeze switch is provided on the second refrigerant pipeline, a third antifreeze switch is provided on the third refrigerant pipeline, and a fourth antifreeze switch is provided on the fourth refrigerant pipeline.

[0008] A control method for a high outlet water temperature chiller according to the present invention, comprising the steps of:

[0009] The hot water inlet temperature t1 of the first condenser is used as the control condition for whether the screw compressor is turned on, and four different temperature thresholds are set as T1>T2>T3>T4;

[0010] If the hot water inlet temperature t1>T1 is monitored, the first screw compressor, the second screw compressor, the third screw compressor and the fourth screw compressor are controlled not to start;

[0011] If it is detected that T2<hot water inlet temperature t1≤T1, only the third screw compressor or the fourth screw compressor is turned on;

[0012] If it is detected that T3<hot water inlet temperature t1≤T2, the third screw compressor and the fourth screw compressor are turned on;

[0013] If it is monitored that T4<hot water inlet temperature t1≤T3, the first screw compressor, the third screw compressor and the fourth screw compressor are started, or the second screw compressor, the third screw compressor and the fourth screw compressor are started;

[0014] If the hot water inlet temperature t1≤T4 is monitored, the first screw compressor, the second screw compressor, the third screw compressor and the fourth screw compressor are started;

[0015] When the chilled water outlet temperature t5 of the first evaporator is higher than 7°C, the unit control does not consider the cold water antifreeze protection function. At this time, the hot water outlet temperature t2 of the fourth heat recovery device is used as the control condition of the screw compressor operation state, and the target temperature of the hot water outlet is set to Sd (Sd<65°C), and the fluctuation range is set to D;

[0016] If the hot water outlet temperature t2 is detected to be lower than Sd-D, the screw compressor that has been turned on is controlled to execute the loading operation instruction;

[0017] If the hot water outlet temperature t2 is monitored to be between Sd-D and Sd+D, the screw compressor that has been turned on is controlled to execute a stable operation instruction;

[0018] If it is monitored that the hot water outlet temperature t2 is higher than Sd+D, the turned-on screw compressor is controlled to execute the unloading operation instruction.

[0019] The control method of the high outlet water temperature chiller, wherein the method further comprises the steps of:

[0020] Set the ultra-high protection temperature value of the hot water outlet temperature t2 to 65°C, and monitor the hot water outlet temperature t2;

[0021] When all the turned-on screw compressors are executing the unloading operation instruction, if it is monitored that 63.5℃<hot water outlet temperature t2≤64℃, the first screw compressor will be shut down; if it is monitored that 64℃<hot water outlet temperature t2≤64.5℃, the first screw compressor and the second screw compressor will be shut down; if it is monitored that 64.5℃<hot water outlet temperature t2≤65℃, the first screw compressor, the second screw compressor and the third screw compressor will be shut down; if it is monitored that 65℃<hot water outlet temperature t2, the first screw compressor, the second screw compressor, the third screw compressor and the fourth screw compressor will be shut down.

[0022] The control method of the high outlet water temperature chiller, wherein the method further comprises the steps of:

[0023] Real-time monitoring of the chilled water outlet temperature t5 of the first evaporator and the chilled water outlet temperature t4 of the second evaporator;

[0024] If the chilled water outlet temperature t5 or the chilled water outlet temperature t4 is monitored to be lower than 3°C, the cold water antifreeze protection function will be activated to control all currently running screw compressors to stop running;

[0025] If the monitored chilled water outlet temperature t5 is between 3°C and 7°C, the currently running screw compressor is controlled to unload and operate until the chilled water outlet temperature t5 recovers to above 7°C, and then returns to normal with the hot water outlet temperature t2 of the fourth heat recovery device as the control condition for the operating state of the screw compressor.

[0026] The control method of the high outlet water temperature chiller, wherein the method further comprises the steps of:

[0027] If the first evaporator or the second evaporator triggers any antifreeze switch, all currently running screw compressors are controlled to stop running.

[0028] Beneficial effect: The control method of the high-outlet-water-temperature chiller provided by the present invention can fully recycle and utilize the condensation heat of each compressor system to achieve energy saving, and can also realize the function of using one chiller to simultaneously produce cold water for air conditioning and hot water for domestic use, thereby achieving the dual goals of multi-purpose use of one machine and energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic structural diagram of a high-water-outlet-temperature chiller.

[0030] Figure 2 The present invention is a flow chart of a control method of a high outlet water temperature chiller. DETAILED DESCRIPTION

[0031] The present invention provides a high outlet water temperature chiller and a control method thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" or "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0033] For ease of understanding, the specific solutions of the embodiments of the present invention are described below. Figure 1 , Figure 1A schematic structural diagram of a high outlet water temperature chiller provided by the present invention, as shown in the figure, comprises a first evaporator 11 and a second evaporator 12 connected through a chilled water pipeline 10, a first screw compressor 21, a first heat recovery device 22 and a first condenser 23 connected in sequence with the first evaporator 11 through a first refrigerant pipeline 20 to form a circulation path, a second screw compressor 31, a second heat recovery device 32 and a second condenser 33 connected in sequence with the first evaporator 11 through a second refrigerant pipeline 30 to form a circulation path; a third screw compressor 41, a third heat recovery device 42 and a third condenser 43 connected in sequence with the second evaporator 12 through a third refrigerant pipeline 40 to form a circulation path 3, a fourth screw compressor 51, a fourth heat recovery device 52 and a fourth condenser 53 which are sequentially connected with the second evaporator 12 through a fourth refrigerant pipeline 50 to form a circulation path; the first condenser 23, the first heat recovery device 22, the second condenser 33, the second heat recovery device 32, the third condenser 43, the third heat recovery device 42, the fourth condenser 53 and the fourth heat recovery device 52 are sequentially connected through a hot water pipeline 60; a first antifreeze switch 24 is provided on the first refrigerant pipeline 20; a second antifreeze switch 34 is provided on the second refrigerant pipeline 30, a third antifreeze switch 44 is provided on the third refrigerant pipeline 40, and a fourth antifreeze switch 54 is provided on the fourth refrigerant pipeline 50.

[0034] like Figure 1 As shown, the high outlet water temperature chiller provided by the present invention is generally composed of 4 screw compressors, 4 condensers, 3 heat recovery devices, 2 evaporators, 4 antifreeze switches, 4 refrigerant pipelines, 1 hot water pipeline and 1 chilled water pipeline. In the figure, the red pipeline represents the hot water pipeline, the black pipeline represents the refrigerant pipeline, and the blue pipeline represents the chilled water pipeline; wherein, the first screw compressor and the second screw compressor share the first evaporator; the third screw compressor and the fourth screw compressor share the second evaporator; this enables the first screw compressor and the second screw compressor to have a fault replacement protection function, the third screw compressor and the fourth screw compressor to have a fault replacement protection function, and the failure of any one screw compressor in the present invention will not affect the normal operation of other screw compressors of the unit.

[0035] Based on the high outlet water temperature chiller, the present invention also provides a control method for the high outlet water temperature chiller, such as Figure 2 As shown, it includes the steps of:

[0036] S10, taking the hot water inlet temperature t1 of the first condenser as the control condition for whether the screw compressor is turned on, and setting four different temperature thresholds as T1>T2>T3>T4;

[0037] S20, if it is monitored that the hot water inlet temperature t1>T1, the first screw compressor, the second screw compressor, the third screw compressor and the fourth screw compressor are controlled not to be turned on;

[0038] S30, if it is detected that T2<hot water inlet temperature t1≤T1, only the third screw compressor or the fourth screw compressor is turned on;

[0039] S40, if it is detected that T3<hot water inlet temperature t1≤T2, the third screw compressor and the fourth screw compressor are turned on;

[0040] S50, if it is monitored that T4<hot water inlet temperature t1≤T3, start the first screw compressor, the third screw compressor and the fourth screw compressor, or start the second screw compressor, the third screw compressor and the fourth screw compressor;

[0041] S60: If the hot water inlet temperature t1≤T4 is detected, the first screw compressor, the second screw compressor, the third screw compressor and the fourth screw compressor are started;

[0042] S70, when the chilled water outlet temperature t5 of the first evaporator is higher than 7°C, the hot water outlet temperature t2 of the fourth heat recovery device is used as the control condition of the operating state of each screw compressor, and the target temperature of the hot water outlet is set to Sd, and the fluctuation range is set to D;

[0043] S80, if it is detected that the hot water outlet temperature t2 is lower than Sd-D, the turned-on screw compressor is controlled to execute the loading operation instruction;

[0044] S90, if it is monitored that the hot water outlet temperature t2 is between Sd-D and Sd+D, the turned-on screw compressor is controlled to execute a stable operation instruction;

[0045] S100: If it is detected that the hot water outlet temperature t2 is higher than Sd+D, the turned-on screw compressor is controlled to execute an unloading operation instruction.

[0046] In the present invention, the hot water inlet temperature t1 is used as a restriction condition for whether each screw compressor is running, that is, when the hot water inlet temperature t1 reaches a certain temperature, the control system will limit the unit to run only part of the compressors. The specific restriction conditions are as follows: when the hot water inlet temperature t1>T1, the four screw compressors are controlled not to be turned on, which means that the hot water inlet temperature t1 at this time is high enough and there is no need to turn on the screw compressor to increase the hot water outlet temperature; when T2<hot water inlet temperature t1≤T1, only the fourth screw compressor or the third screw compressor is allowed to be turned on, which means that only one screw compressor needs to be turned on to increase the hot water outlet temperature degrees, the target temperature can be reached. In this embodiment, the fourth screw compressor and the third screw compressor have the function of fault replacement and time rotation. To avoid water temperature fluctuations, the time rotation is only when the unit is shut down or the third and fourth screw compressors are both shut down. Only then will it be decided to start one of the fourth and third screw compressors according to the running time of the two screw compressors; when T3<hot water inlet temperature t1≤T2, the third screw compressor and the fourth screw compressor need to be started at the same time, indicating that the hot water inlet temperature t1 is far from the target temperature at this time, and the two screw compressors need to be started at the same time to increase the hot water outlet temperature t2 to reach the target temperature; when T4<hot water inlet temperature t1≤T3, the first screw compressor, the third screw compressor and the fourth screw compressor are turned on, or the second screw compressor, the third screw compressor and the fourth screw compressor are turned on, indicating that the hot water inlet temperature t1 is low at this time, and three screw compressors need to be turned on to increase the hot water outlet temperature t2 to make the hot water outlet temperature t2 reach the target temperature. At this time, the No. 1 and No. 2 screw compressors have fault replacement and time rotation functions. To avoid water temperature fluctuations, the time rotation will only be decided according to the running time of the two screw compressors after the unit is shut down or the first and second screw compressors are shut down. Start one of the screw compressors No. 1 and No. 2; when the hot water inlet temperature t1≤T4, it is necessary to start the first screw compressor, the second screw compressor, the third screw compressor and the fourth screw compressor, indicating that the hot water inlet temperature t1 is very low at this time, and it is necessary to start four screw compressors at the same time to increase the hot water outlet temperature t2, so that the hot water outlet temperature t2 can reach the target temperature. The start sequence of the four screw compressors is four, three, two, and one. There is a start interval of 5S-10S between each compressor, which is 5S by default (settable). While realizing the rapid hot water production function, it can avoid the impact of the simultaneous start of each compressor on the customer's power grid. In this embodiment, T1>T2>T3>T4. As an example, assuming that the target temperature is 60°C, T1 can be 58°C, T2 can be 55°C, T3 can be 45°C, and T4 can be 32°C.

[0047] In the present invention, when the chilled water outlet temperature t5 of the first evaporator is higher than 7°C, the cold water antifreeze protection function is not considered, and the hot water outlet temperature t2 of the fourth heat recovery device is used as the control condition of the operating state of the screw compressor. The target temperature of the hot water outlet is set to Sd, and the fluctuation range is set to D. If the hot water outlet temperature t2 is monitored to be lower than Sd-D, the turned-on screw compressor is controlled to execute the loading operation instruction; if the hot water outlet temperature t2 is monitored to be between Sd-D and Sd+D, the turned-on screw compressor is controlled to execute the stable operation instruction; if the hot water outlet temperature t2 is monitored to be higher than Sd+D, the turned-on screw compressor is controlled to execute the unloading operation instruction. For example, the default setting value Sd of the hot water outlet temperature of the unit after leaving the factory is 60℃, and the allowable fluctuation range of the hot water outlet temperature t2 of the unit is D. The default value of D is 1℃ when leaving the factory. The control system will take the hot water outlet temperature t2 as the final stabilization between 59℃-61℃ as the control target, load operation if it is below 59℃, unload operation if it exceeds 61℃, and the current output remains unchanged if it is stable between 59℃ and 61℃.

[0048] The present invention is based on the control method of the high outlet water temperature chiller, which can fully recycle and utilize the condensation heat of each compressor system to achieve energy saving, and can also use one chiller to simultaneously produce cold water for air conditioning and hot water for domestic use, thereby achieving the dual goals of multi-purpose use of one machine and energy saving.

[0049] In some embodiments, the control method of the high outlet water temperature chiller provided by the present invention also has an ultra-high protection function for the hot water outlet temperature, and the ultra-high protection temperature value of the hot water outlet temperature t2 is set to 65°C, and the hot water outlet temperature t2 is monitored; when the screw compressors that have been turned on are all executing the unloading operation instruction, if it is monitored that 63.5°C < hot water outlet temperature t2≤64°C, the first screw compressor is turned off; if it is monitored that 64°C < hot water outlet temperature t2≤64.5°C, the first screw compressor and the second screw compressor are turned off; if it is monitored that 64.5°C < hot water outlet temperature t2≤65°C, the first screw compressor, the second screw compressor and the third screw compressor are turned off; if it is monitored that 65°C < hot water outlet temperature t2, the first screw compressor, the second screw compressor, the third screw compressor and the fourth screw compressor are turned off. The control method of this embodiment can effectively control the hot water outlet temperature and utilize the condensation heat of the compressor system to prevent heat loss.

[0050] In some embodiments, the control method of the high outlet water temperature chiller provided by the present invention also has a cold water outlet temperature too low protection function, real-time monitoring of the chilled water outlet temperature t5 of the first evaporator and the chilled water outlet temperature t4 of the second evaporator; if it is monitored that any of the chilled water outlet temperature t5 or the chilled water outlet temperature t4 is lower than 3°C, the cold water antifreeze protection function is activated to control all currently running screw compressors to stop running; if the first evaporator or the second evaporator triggers any antifreeze switch (any one of the first antifreeze switch to the fourth antifreeze switch), all currently running screw compressors are controlled to stop running; if it is monitored that the chilled water outlet temperature t5 is between 3°C-7°C, the currently running screw compressor is controlled to unload and run until the chilled water outlet temperature t5 returns to above 7°C, and then the normal control condition of the operation state of the screw compressor is restored to the hot water outlet temperature t2 of the fourth heat recovery device. The control method of this embodiment can effectively avoid the risk of evaporator freezing and cracking.

[0051] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A high outlet water temperature chiller, characterized in that: include: a first evaporator and a second evaporator connected through a chilled water pipeline, a first screw compressor, a first heat recovery device and a first condenser connected in sequence with the first evaporator through a first refrigerant pipeline to form a circulation path, a second screw compressor, a second heat recovery device and a second condenser connected in sequence with the first evaporator through a second refrigerant pipeline to form a circulation path; a third screw compressor, a third heat recovery device and a third condenser connected in sequence with the second evaporator through a third refrigerant pipeline to form a circulation path, a fourth screw compressor, a fourth heat recovery device and a fourth condenser connected in sequence with the second evaporator through a fourth refrigerant pipeline to form a circulation path; the first condenser, the first heat recovery device, the second condenser, the second heat recovery device, the third condenser, the third heat recovery device, the fourth condenser and the fourth heat recovery device are connected in series in sequence through a hot water pipeline; a first antifreeze switch is provided on the first refrigerant pipeline; a second antifreeze switch is provided on the second refrigerant pipeline, a third antifreeze switch is provided on the third refrigerant pipeline, and a fourth antifreeze switch is provided on the fourth refrigerant pipeline.

2. A control method for a high outlet water temperature chiller as claimed in claim 1, characterized in that: Includes steps: The hot water inlet temperature t1 of the first condenser is used as the control condition for whether the screw compressor is turned on, and four different temperature thresholds are set as T1>T2>T3>T4; If the hot water inlet temperature t1>T1 is monitored, the first screw compressor, the second screw compressor, the third screw compressor and the fourth screw compressor are controlled not to start; If it is detected that T2<hot water inlet temperature t1≤T1, only the third screw compressor or the fourth screw compressor is turned on; If it is detected that T3<hot water inlet temperature t1≤T2, the third screw compressor and the fourth screw compressor are turned on; If it is monitored that T4<hot water inlet temperature t1≤T3, the first screw compressor, the third screw compressor and the fourth screw compressor are started, or the second screw compressor, the third screw compressor and the fourth screw compressor are started; If the hot water inlet temperature t1≤T4 is monitored, the first screw compressor, the second screw compressor, the third screw compressor and the fourth screw compressor are started; When the chilled water outlet temperature t5 of the first evaporator is higher than 7°C, the unit control does not consider the cold water antifreeze protection function. At this time, the hot water outlet temperature t2 of the fourth heat recovery device is used as the control condition of the screw compressor operation state, and the target temperature of the hot water outlet is set to Sd, and the fluctuation range is set to D; If the hot water outlet temperature t2 is detected to be lower than Sd-D, the screw compressor that has been turned on is controlled to execute the loading operation instruction; If the hot water outlet temperature t2 is monitored to be between Sd-D and Sd+D, the screw compressor that has been turned on is controlled to execute a stable operation instruction; If it is monitored that the hot water outlet temperature t2 is higher than Sd+D, the turned-on screw compressor is controlled to execute the unloading operation instruction.

3. The control method of the high outlet water temperature chiller according to claim 2, characterized in that: Also includes the steps: Set the ultra-high protection temperature value of the hot water outlet temperature t2 to 65°C, and monitor the hot water outlet temperature t2; When all the turned-on screw compressors are executing the unloading operation instruction, if it is monitored that 63.5℃<hot water outlet temperature t2≤64℃, the first screw compressor will be shut down; if it is monitored that 64℃<hot water outlet temperature t2≤64.5℃, the first screw compressor and the second screw compressor will be shut down; if it is monitored that 64.5℃<hot water outlet temperature t2≤65℃, the first screw compressor, the second screw compressor and the third screw compressor will be shut down; if it is monitored that 65℃<hot water outlet temperature t2, the first screw compressor, the second screw compressor, the third screw compressor and the fourth screw compressor will be shut down.

4. The control method of the high outlet water temperature chiller according to claim 2, characterized in that: Also includes the steps: Real-time monitoring of the chilled water outlet temperature t5 of the first evaporator and the chilled water outlet temperature t4 of the second evaporator; If the chilled water outlet temperature t5 or the chilled water outlet temperature t4 is monitored to be lower than 3°C, the cold water antifreeze protection function will be activated to control all currently running screw compressors to stop running; If the monitored chilled water outlet temperature t5 is between 3°C and 7°C, the currently running screw compressor is controlled to unload until the chilled water outlet temperature t5 recovers to above 7°C, and then the normal operation is restored with the hot water outlet temperature t2 of the fourth heat recovery device as the control condition for the operating status of the screw compressor.

5. The control method of the high outlet water temperature chiller according to claim 2, characterized in that: Also includes the steps: If the first evaporator or the second evaporator triggers any antifreeze switch, all currently running screw compressors are controlled to stop running.

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