Throttling device and method for air-suspension variable-frequency centrifugal water chilling unit

Abstract

The invention discloses an air-suspension variable-frequency centrifugal water chilling unit throttling device, which belongs to the technical field of water chiller, and comprises a condenser, a flash tank is communicated with the condenser, an evaporator and a compressor are communicated with the flash tank, the evaporator is communicated with the compressor, and the compressor is communicated with the condenser, so that a refrigeration circulation loop is formed. The condenser is communicated with the flash tank through a first throttling pipeline, the flash tank is communicated with the evaporator through a second throttling pipeline, a first electric ball valve is arranged on the first throttling pipeline, a second electric ball valve is arranged on the second throttling pipeline, and the first electric ball valve and the second electric ball valve are both electrically connected with the main controller. The invention further provides a throttling method of the air-suspension variable-frequency centrifugal water chilling unit. The liquid level of the evaporator is kept stable, and the problems that the compressor is prone to air suction and liquid carrying due to the too high liquid level, liquid impact is generated, and the refrigerating capacity is insufficient due to the too low liquid level are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of chillers, and particularly relates to a throttling device and method for an air suspension variable frequency centrifugal chiller. Background Art

[0002] The throttling device is one of the key components of an air-conditioning refrigeration system. Its function is to throttle and depressurize the high-pressure liquid from the condenser into a low-pressure liquid, and at the same time regulate the refrigerant flow rate entering the evaporator.

[0003] Common throttling mechanisms for large central air-conditioning chillers include orifice plates, thermostatic expansion valves, electronic expansion valves, manual throttle valves, float valves, electric ball valves, etc. The orifice plate throttle valve has excellent throttling characteristics and a uniform change in flow area, but it belongs to a throttling orifice with a fixed cross-section and cannot automatically adjust the flow rate according to load changes; the thermostatic expansion valve can automatically adjust the refrigerant flow rate according to changes in the system load, keep the superheat at the evaporator outlet stable, and has strong adaptability, but its adjustment accuracy is low, the range is limited, and the delay time for responding to superheat is long; compared with the thermostatic expansion valve, the electronic expansion valve has a higher response speed and a wider adjustment range, and can be dynamically adjusted according to various parameters of the system, but its price is high; the manual regulating valve is one of the most traditional throttling devices, and completely relies on manual operation to adjust the valve opening, resulting in low control accuracy; the float valve has a simple structure, but in the case of large liquid level fluctuations, the impact of the float on the valve core may cause damage.

[0004] Existing throttling devices are difficult to meet the requirements of timely response and automatic precise control of the throttling device for an air suspension variable frequency centrifugal chiller.

[0005] Therefore, there is an urgent need to design a throttling device and method for an air suspension variable frequency centrifugal chiller to solve the problem of difficulty in meeting the requirements of timely response and automatic precise control of the throttling device for an air suspension variable frequency centrifugal chiller mentioned above. Summary of the Invention

[0006] To solve the technical problem of difficulty in meeting the requirements of timely response and automatic precise control of the throttling device for an air suspension variable frequency centrifugal chiller mentioned in the background art, a throttling device and method for an air suspension variable frequency centrifugal chiller are provided to solve the above problems.

[0007] To achieve the above object, the specific technical solutions of the throttling device and method for an air suspension variable frequency centrifugal chiller of the present invention are as follows: A throttling device for an air suspension variable frequency centrifugal chiller includes a condenser, a flash tank is connected to the condenser, an evaporator and a compressor are connected to the flash tank, the evaporator is connected to the compressor, and the compressor is connected to the condenser, thus forming a refrigeration cycle loop. The condenser is connected to the flash tank through the first throttling pipeline, and the flash tank is connected to the evaporator through the second throttling pipeline. A first electric ball valve is provided on the first throttling pipeline, and a second electric ball valve is provided on the second throttling pipeline. Both the first electric ball valve and the second electric ball valve are electrically connected to the main controller.

[0008] Furthermore, a first electronic liquid level gauge is provided on the flash tank to detect the liquid level height of the flash tank. The first electronic liquid level gauge is electrically connected to the main controller. A second electronic liquid level gauge is provided on the evaporator to detect the liquid level height of the evaporator. The second electronic liquid level gauge is electrically connected to the main controller.

[0009] Furthermore, both the first electric ball valve and the second electric ball valve are V-type electric ball valves.

[0010] Another object of the present invention is to provide a throttling method for an air suspension variable frequency centrifugal chiller, which controls the throttling device of the air suspension variable frequency centrifugal chiller, including: S1. The main controller obtains the readings of the first electronic liquid level gauge and the second electronic liquid level gauge; S2. The main controller compares the reading of the first electronic liquid level gauge with the first preset height to obtain a first deviation value, and the main controller compares the reading of the second electronic liquid level gauge with the second preset height to obtain a second deviation value; S3. The main controller maintains the liquid level height of the flash tank at the first preset height according to the first deviation value; the main controller maintains the liquid level height of the evaporator at the second preset height according to the second deviation value.

[0011] Furthermore, in S3, the main controller controls the opening degree of the first electric ball valve through the PID algorithm according to the first deviation value, and the main controller controls the opening degree of the second electric ball valve through the PID algorithm according to the second deviation value.

[0012] Furthermore, the PID algorithm is an integral separation PID control algorithm. The main controller controls the opening degree of the first electric ball valve through the integral separation PID control algorithm according to the first deviation value, including: ; where k is the current sampling moment; is the PID calculation result of the flash tank; is the proportional coefficient; is the first deviation value at the current sampling moment; A is the opening coefficient of the integral term; is the integral time; is the differential time; is the first deviation value at the previous sampling moment; T is the sampling time.

[0013] Furthermore, the value of A is as follows: , where B is the preset deviation value.

[0014] Further, when [condition], PD control is adopted; when [condition], PID control is adopted.

[0015] The throttling device and method of the air suspension variable frequency centrifugal chiller of the present invention have the following advantages: By detecting the liquid levels in the flash tank and the evaporator, the present invention controls the opening degrees of two electric ball valves, so that the pressure in the flash tank can send the refrigerant gas to the second-stage pipeline of the compressor for air replenishment, increasing the compression efficiency of the compressor and improving the refrigeration energy efficiency; at the same time, the liquid level of the evaporator is controlled to be stable, avoiding the problem that when the liquid level is too high, the compressor is prone to suck liquid and generate liquid hammer, and when the liquid level is too low, the refrigeration capacity is insufficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of the throttling device of the air suspension variable frequency centrifugal chiller of the present invention; Figure 2 is a flowchart of the throttling method of the air suspension variable frequency centrifugal chiller of the present invention; Description of the reference numerals in the drawings: 1. Condenser; 2. Flash tank; 3. Evaporator; 4. Compressor; 5. First throttling pipeline; 6. Second throttling pipeline; 7. First electric ball valve; 8. Second electric ball valve; 9. First electronic liquid level gauge; 10. Second electronic liquid level gauge. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] Those skilled in the art can understand that although some embodiments herein include certain features included in other embodiments but not other features, the combination of the features of different embodiments means within the scope of the present invention and forms different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

[0019] Next, refer to the attached Figure 1 to the attached Figure 2 to describe the throttling device and method of the air suspension variable frequency centrifugal chiller of the present invention.

[0020] An air suspension variable frequency centrifugal chiller throttling device, as Figure 1As shown in the figure, it includes a condenser 1, a flash evaporator 2 is connected to the condenser 1, an evaporator 3 and a compressor 4 are connected to the flash evaporator 2, the evaporator 3 is connected to the compressor 4, and the compressor 4 is connected to the condenser 1, thus forming a refrigeration cycle loop. The condenser 1 and the flash evaporator 2 are connected through a first throttling pipeline 5, and the flash evaporator 2 and the evaporator 3 are connected through a second throttling pipeline 6. A first electric ball valve 7 is arranged on the first throttling pipeline 5, and a second electric ball valve 8 is arranged on the second throttling pipeline 6. Both the first electric ball valve 7 and the second electric ball valve 8 are electrically connected to a main controller (not shown in the figure). Specifically, the main controller independently controls the first electric ball valve 7 and the second electric ball valve 8 respectively, thereby adjusting the flow rates in the first throttling pipeline 5 and the second throttling pipeline 6, so as to achieve the timely response and automatic precise control of the throttling device of the air suspension variable frequency centrifugal chiller.

[0021] Preferably, a first electronic liquid level gauge 9 is arranged on the flash evaporator 2 to detect the liquid level height of the flash evaporator 2. The first electronic liquid level gauge 9 is electrically connected to the main controller. A second electronic liquid level gauge 10 is arranged on the evaporator 3 to detect the liquid level height of the evaporator 3. The second electronic liquid level gauge 10 is electrically connected to the main controller. Specifically, the main controller controls the opening degree of the first electric ball valve 7 by receiving the reading of the first electronic liquid level gauge 9, thereby adjusting the flow rate of the first throttling pipeline 5; the main controller controls the opening degree of the second electric ball valve 8 by receiving the reading of the second electronic liquid level gauge 10, thereby adjusting the flow rate of the second throttling pipeline 6.

[0022] Preferably, both the first electric ball valve 7 and the second electric ball valve 8 are V-type electric ball valves. A V-shaped opening is provided on the ball of the V-type electric ball valve. As the ball rotates, the opening area changes, but the shape of the opening surface always remains triangular, and the flow characteristic is approximately equal percentage. The percentage value obtained by the PID algorithm can be directly used to adjust the opening percentage of the V-type electric ball valve. It has a strong adaptability to the PID algorithm. At the same time, the V-type electric ball valve has a large flow capacity, a large adjustable range, and characteristics such as shear force and tight closing.

[0023] An air suspension variable frequency centrifugal chiller throttling method, as Figure 2 shown, includes: S1. The main controller obtains the readings of the first electronic liquid level gauge 9 and the second electronic liquid level gauge 10; S2. The main controller compares the reading of the first electronic liquid level gauge 9 with a first preset height to obtain a first deviation value, and the main controller compares the reading of the second electronic liquid level gauge 10 with a second preset height to obtain a second deviation value; S3. The main controller maintains the liquid level height of the flash evaporator 2 at the first preset height according to the first deviation value; the main controller maintains the liquid level height of the evaporator 3 at the second preset height according to the second deviation value; The master controller controls the opening degree of the first electric ball valve 7 through the PID algorithm according to the first deviation value, and the master controller controls the opening degree of the second electric ball valve 8 through the PID algorithm according to the second deviation value; Preferably, taking the first throttle pipeline 5 as an example: The PID algorithm is an integral separation PID control algorithm. The master controller controls the opening degree of the first V-type electric ball valve through the integral separation PID control algorithm according to the first deviation value, including: ; where k is the current sampling moment; is the PID calculation result of the flash evaporator; is the proportional coefficient; is the first deviation value at the current sampling moment; A is the opening coefficient of the integral term; is the integral time; is the differential time; is the first deviation value at the previous sampling moment; T is the sampling time; is the integral starting moment.

[0024] Preferably, the value of A is as follows: , and B is a preset deviation value.

[0025] Preferably, when, PD control is adopted to avoid excessive overshoot and make the system have a faster response; when, PID control is adopted to ensure the liquid level control accuracy.

[0026] Similarly, the control mode of the second throttle pipeline 6 is the same as that of the first throttle pipeline 5, which will not be elaborated here.

[0027] In a specific implementation, the sampling time T in the first throttle pipeline 5 takes a value of 1 s, the proportional coefficient Kp takes a value of 1.8, the integral time Ti takes a value of 100 s, the differential time Td takes a value of 3.5 s, and the preset deviation B is 10 mm. The opening degree of the first electric ball valve 7 is controlled according to the PID calculation result of the flash evaporator 2; the sampling time T in the second throttle pipeline 6 takes a value of 1 s, the proportional coefficient Kp takes a value of 3.1, the integral time Ti takes a value of 80 s, the differential time Td takes a value of 2.6 s, and the preset deviation B is 6 mm. The opening degree of the second electric ball valve 8 is controlled according to the PID calculation result of the evaporator 3.

[0028] The present invention controls the opening degrees of two electric ball valves by detecting the liquid levels in the flash evaporator 2 and the evaporator 3, so that the pressure in the flash evaporator 2 can send the refrigerant gas to the secondary pipeline of the compressor 4 for gas replenishment, increasing the compression efficiency of the compressor 4 and improving the refrigeration energy efficiency; at the same time, the liquid level of the evaporator 3 is controlled to be stable, avoiding the problem that the compressor 4 is prone to liquid carry-over and liquid hammer when the liquid level is too high, and insufficient refrigeration capacity when the liquid level is too low.

[0029] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made on the basis of the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A throttling device for an air suspension variable frequency centrifugal chiller, characterized in that It includes a condenser, a flash evaporator is connected to the condenser, an evaporator and a compressor are connected to the flash evaporator, the evaporator is connected to the compressor, and the compressor is connected to the condenser, thus forming a refrigeration cycle loop. The condenser and the flash evaporator are connected through a first throttle pipeline, the flash evaporator and the evaporator are connected through a second throttle pipeline, a first electric ball valve is arranged on the first throttle pipeline, a second electric ball valve is arranged on the second throttle pipeline, and both the first electric ball valve and the second electric ball valve are electrically connected to the main controller.

2. The throttling device of the air suspension variable frequency centrifugal chiller according to claim 1, characterized in that, A first electronic liquid level gauge is arranged on the flash evaporator to detect the liquid level height of the flash evaporator, the first electronic liquid level gauge is electrically connected to the main controller, a second electronic liquid level gauge is arranged on the evaporator to detect the liquid level height of the evaporator, and the second electronic liquid level gauge is electrically connected to the main controller.

3. The throttling device for an air suspension variable frequency centrifugal chiller according to claim 1 or 2, characterized in that, Both the first electric ball valve and the second electric ball valve are V-type electric ball valves.

4. A throttling method for an air suspension variable frequency centrifugal chiller, which controls the throttling device of the air suspension variable frequency centrifugal chiller as described in any one of claims 1-3, characterized in that, It includes: S1. The main controller obtains the readings of the first electronic liquid level gauge and the second electronic liquid level gauge. S2. The main controller compares the reading of the first electronic liquid level gauge with a first preset height to obtain a first deviation value, and compares the reading of the second electronic liquid level gauge with a second preset height to obtain a second deviation value. S3. The main controller maintains the liquid level height of the flash evaporator at the first preset height according to the first deviation value; the main controller maintains the liquid level height of the evaporator at the second preset height according to the second deviation value.

5. The throttling method of the air suspension variable frequency centrifugal chiller according to claim 4, characterized in that, In S3, the main controller controls the opening degree of the first electric ball valve through the PID algorithm according to the first deviation value, and controls the opening degree of the second electric ball valve through the PID algorithm according to the second deviation value.

6. The throttling method of the air suspension variable frequency centrifugal chiller according to claim 5, characterized in that, The PID algorithm is an integral separation PID control algorithm. The main controller controls the opening degree of the first electric ball valve through the integral separation PID control algorithm according to the first deviation value, including: ； where k is the current sampling time; is the calculation result of the flash tank PID; is the proportional coefficient; is the first deviation value at the current sampling time; A is the opening coefficient of the integral term; is the integral time; is the derivative time; is the first deviation value at the previous sampling time; T is the sampling time.

7. The throttling method of the air suspension variable frequency centrifugal chiller according to claim 6, characterized in that, The value of A is as follows: , where B is a preset deviation value.

8. The throttling method of the air suspension variable frequency centrifugal chiller according to claim 7, characterized in that When it is [specific condition 0], PD control is adopted; When it is [specific condition 1], PID control is adopted.

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