CN116336578A

CN116336578A - Method and device for controlling centrifugal refrigerator

Info

Publication number: CN116336578A
Application number: CN202111602640.6A
Authority: CN
Inventors: 张雨薇; 徐峰; 钱亮; 胡敬仁; 陈嘉雯
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2021-12-24
Filing date: 2021-12-24
Publication date: 2023-06-27

Abstract

The present application relates to air conditioning systems, and more particularly, to a control method for a centrifugal chiller, a control device and a computer-readable storage medium for implementing the method, and an air conditioning system including the control device. According to one aspect of the present application, there is provided a control method for controlling a centrifugal refrigerator, comprising the steps of: A. when the centrifugal refrigerator operates under the variable flow working condition, obtaining the measured flow and the measured inlet water temperature of chilled water at the evaporator side of the centrifugal refrigerator; B. determining the equivalent water inlet temperature of chilled water at the evaporator side under the variable flow working condition by taking the constant flow working condition of the centrifugal refrigerator as a reference; and C, controlling the operation of the centrifugal refrigerator based on the measured flow rate, the equivalent inlet water temperature and the measured outlet water temperature of the chilled water at the evaporator side.

Description

Method and device for controlling centrifugal refrigerator

Technical Field

The present application relates to air conditioning systems, and more particularly, to a control method for a centrifugal chiller, a control device and a computer-readable storage medium for implementing the method, and an air conditioning system including the control device.

Background

Centrifugal refrigerators generally employ flooded evaporators which feature a shell side for the refrigerant and a tube side for the water. The heat exchange between the liquid refrigerant and the liquid water is always carried out in the heat exchange process, the heat transfer surface is basically contacted with the liquid refrigerant, the generated refrigerant gas directly enters the compressor from the air suction of the compressor, the heat exchange area is effectively utilized, and the heat exchange efficiency of the unit is improved.

In a centrifugal refrigerator, a flow system is used to supply a cooled medium (chilled water) to an evaporator. In a constant flow system, the refrigeration capacity of a centrifugal chiller is typically determined based on the full load and fixed chilled water flow. On the other hand, with the increasing use of variable flow systems, how to determine appropriate control parameters for different water flows has become an urgent issue to be addressed.

Disclosure of Invention

According to one aspect of the present application, there is provided a method for controlling a centrifugal chiller, comprising the steps of:

A. when the centrifugal refrigerator operates under the variable flow working condition, obtaining the actually measured flow, actually measured inlet water temperature and actually measured outlet water temperature of chilled water at the evaporator side of the centrifugal refrigerator;

B. determining the equivalent water inlet temperature of chilled water at the evaporator side under the variable flow working condition by taking the constant flow working condition of the centrifugal refrigerator as a reference; and

C. and controlling the operation of the centrifugal refrigerator based on the measured flow rate, the equivalent inlet water temperature and the measured outlet water temperature of the chilled water at the evaporator side.

Optionally, in the above method, further comprising:

D. when the centrifugal refrigerator operates under a constant flow rate working condition, the operation of the centrifugal refrigerator is controlled based on the set flow rate of the chilled water at the evaporator side, the actually measured inlet water temperature and the actually measured outlet water temperature.

Alternatively, in the above method, in step a, the measured flow rate is obtained by reading a measured value of the flow rate from a flow meter or a differential pressure sensor provided in the chilled water line flowing through the evaporator.

Alternatively, in the above method, in step B, the equivalent inlet water temperature of the chilled water at the evaporator side under the variable flow condition is determined by making the refrigerating capacity of the centrifugal refrigerator under the variable flow condition equal to the refrigerating capacity under the fixed flow condition.

Optionally, in the above method, in step B, the equivalent inlet water temperature of the chilled water at the evaporator side under variable flow conditions is determined as follows:

here, T _v T is the equivalent water inlet temperature of chilled water at the evaporator side under the working condition of variable flow _enter For the actual measured inlet temperature of chilled water at the evaporator side, T _exit For the measured outlet temperature of chilled water at the evaporator side, M _f The set flow of chilled water at the evaporator side under the constant flow working condition is M _v Is the actual measurement flow of chilled water at the evaporator side under the variable flow working condition.

Optionally, in the above method, further comprising:

E. determining whether the measured inlet water temperature of the chilled water at the evaporator side is within a set range; and

F. and when the measured inlet water temperature of the chilled water at the evaporator side exceeds a set range, generating an alarm indication.

According to another aspect of the present application, there is provided a control apparatus for a centrifugal refrigerator, comprising:

a memory;

a processor; and

a computer program stored on the memory and executable on the processor, the execution of the computer program causing the operations of:

A. when the centrifugal refrigerator operates under the variable flow working condition, obtaining the measured flow and the measured inlet water temperature and the measured outlet water temperature of the chilled water at the evaporator side of the centrifugal refrigerator;

According to still another aspect of the present application, there is provided an air conditioning system including:

a centrifugal refrigerator; and

the control device as described above.

According to yet another aspect of the present application, there is provided a computer readable storage medium having instructions stored therein, which when executed by a processor, cause the processor to perform the method as described above.

Drawings

The foregoing and/or other aspects and advantages of the present application will become more apparent and more readily appreciated from the following description of the various aspects taken in conjunction with the accompanying drawings in which like or similar elements are designated with the same reference numerals. The drawings include:

fig. 1 is a schematic block diagram of a typical air conditioning system.

Fig. 2 is a schematic block diagram of a control device for a centrifugal chiller according to some embodiments of the present application.

Fig. 3 is a flow chart of a method for controlling a centrifugal chiller according to further embodiments of the present application.

Fig. 4 is a flow chart of a method for controlling a centrifugal chiller according to still further embodiments of the present application.

Fig. 5 is a flow chart of a method for controlling a centrifugal chiller according to still further embodiments of the present application.

Detailed Description

The present application is described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the application are shown. This application may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. The above-described embodiments are provided to fully complete the disclosure herein so as to more fully convey the scope of the application to those skilled in the art.

In this specification, terms such as "comprising" and "including" mean that there are other elements and steps not directly or explicitly recited in the description and claims, nor do the subject matter of the present application exclude the presence of other elements and steps.

Unless specifically stated otherwise, terms such as "first" and "second" do not denote a sequential order of elements in terms of time, space, size, etc., but rather are merely used to distinguish one element from another.

In this specification, "coupled" should be understood to include the case of directly transferring electrical energy or electrical signals between two units, or the case of indirectly transferring electrical energy or electrical signals through one or more third units.

Fig. 1 is a schematic block diagram of a typical air conditioning system. As shown in fig. 1, the air conditioning system 10 includes an evaporator or water chiller 110, a condenser 120, a compressor 130, a throttle device 140, a control device 150, a main pump 160, a flow meter 170, and the like. In fig. 1, a thick solid line indicates a refrigerant line, a thick dotted line indicates a chilled water line, and a thin solid line indicates a control signal or measurement signal transmission line.

It should be noted that the air conditioning system shown here does not show the indoor fan and the temperature sensor, etc., but such omission does not constitute an obstacle and difficulty for a person skilled in the art to understand and implement the technical solutions described in the present specification.

In the air conditioning system shown in fig. 1, chilled water is delivered to the evaporator 110 side by the main pump 160, where heat exchange with refrigerant occurs, so that the heat of the former is absorbed, thereby achieving the purpose of cooling.

With continued reference to fig. 1, a flow meter 170 is provided in the line through which chilled water circulates to measure the flow of chilled water on the evaporator side. Alternatively, a differential pressure sensor may be used instead of a flow meter to obtain the measured flow rate of chilled water on the evaporator side.

When the centrifugal refrigerating unit adopts a constant flow system to convey chilled water (hereinafter also referred to as constant flow working condition), the refrigerating capacity of the centrifugal refrigerating unit can be determined according to the following formula:

Q _f ＝M _f ×C×(T _enter -T _exit ) (1)

here, Q _f In order to adopt the constant flow system to convey the refrigerating capacity of the chilled water, C is the specific heat coefficient of the chilled water, T _enter For the actual measured inlet temperature of chilled water at the evaporator side, T _exit For the measured outlet temperature of chilled water at the evaporator side, M _f The flow rate of chilled water at the evaporator side is set when a constant flow rate system is used.

On the other hand, when the centrifugal chiller unit employs a variable flow system to deliver chilled water, the flow rate of the chilled water at the evaporator side may be equal to the above-described set flow rate, but may be greater or less than the above-described set flow rate. The inventors of the present applicant have found through research that if the refrigerating capacity of the centrifugal refrigerator is still calculated according to the above formula (1) and the refrigerating capacity and the measured inlet water temperature are adopted as input parameters in the operation control logic of the centrifugal refrigerator, a large control error will be caused, thereby causing unstable operation of the whole system.

For this reason, in some embodiments of the present application, for the condition in which the variable flow system delivers chilled water (hereinafter also referred to as variable flow condition), an equivalent inlet water temperature, which will be described in detail below, is used as an input parameter in controlling the operation of the centrifugal refrigerator instead of the measured inlet water temperature of the chilled water. The inventor of the applicant has found through research that after replacing the measured inlet water temperature with the equivalent inlet water temperature, the application of centrifugal refrigerator control logic under constant flow rate working conditions to control various units (such as a compressor, a condenser, an evaporator and the like) in the centrifugal refrigerator can still ensure the stability of the operation of the system.

In some embodiments of the present application, the equivalent inlet water temperature is determined based on a constant flow rate working condition of the centrifugal refrigerator, that is, when the equivalent temperature is determined, the refrigeration capacity required by the centrifugal refrigerator under the constant flow rate working condition is determined according to the measured inlet water temperature, the measured outlet water temperature and the set flow rate, and the determined refrigeration capacity is taken as the refrigeration capacity required by the centrifugal refrigerator under the variable flow rate working condition.

One example of how the equivalent inlet water temperature is determined is described below.

For variable flow systems, the refrigeration capacity of a centrifugal chiller is still expressed in a mathematical form similar to equation (1), namely:

Q _v ＝M _v ×C×(T _v -T _exit ) (2)

here, Q _v The refrigerating capacity under the variable flow working condition is C is the specific heat coefficient of chilled water, T _v T is the equivalent inlet temperature of chilled water at the evaporator side _exit For the measured outlet temperature of chilled water at the evaporator side, M _v Is the measured flow rate of chilled water at the evaporator side (e.g., as measured by a flow meter or differential pressure sensor) under variable flow conditions.

As described above, the required cooling capacity under variable flow conditions is determined to be equal to the required cooling capacity under constant flow conditions, i.e., Q _f ＝Q _v 。

The following formula can be obtained from formulas (1) and (2):

Under the variable flow working condition, the control logic of the centrifugal refrigerator under the constant flow working condition can be continuously used by replacing the actually measured water inlet temperature with the equivalent water inlet temperature, so that the cost reduction and the acceleration of the development process are facilitated. Furthermore, the calculation of the equivalent inlet water temperature does not involve complex algorithms, which makes the above advantages even more pronounced.

Fig. 2 is a schematic block diagram of a control device for a centrifugal chiller according to some embodiments of the present application. The control device shown in fig. 2 may be used to implement the control device 150 of fig. 1.

The control device 20 shown in fig. 2 comprises a communication unit 210, a memory 220 (e.g. a non-volatile memory such as a flash memory, a ROM, a hard disk drive, a magnetic disk, an optical disk, etc.), a processor 230, and a computer program 240.

The communication unit 210 serves as a communication interface configured to establish a communication connection between the control apparatus and an external device or a network (e.g., other units in the air conditioning system or external devices of the air conditioning system).

The computer program 240 stored on the memory 220 may run on the processor 230 to implement the steps involved in the control method described below with the aid of fig. 3-5.

The method flow of the present embodiment will be described below by way of example using the control device shown in fig. 2, i.e. the steps of the method shown in fig. 3-5 are implemented by running a computer program 240 on the processor 230. It should be understood, however, that the implementation of the method steps described below is not limited to a particular type and configuration of control device.

The method shown in fig. 3 comprises the following steps:

step 301: whether the chilled water supply system of the centrifugal chiller is a constant flow system or a variable flow system is determined, and if it is a constant flow system, the flow enters a sub-flow described below with the aid of fig. 4, and if it is a variable flow system, the flow enters a sub-flow described below with the aid of fig. 5.

Fig. 4 is a flow chart of a method for controlling a centrifugal chiller according to further embodiments of the present application.

Step 401: obtaining the actually measured inlet water temperature T of chilled water at the evaporator side _enter And the measured outlet water temperature T _exit (e.g., reading temperature measurements from temperature sensors disposed near the evaporator side chilled water inlet and outlet via communication unit 210).

Step 402: determining the actual measured inlet water temperature T _enter If within the set range, step 403 is entered, otherwise step 404 is entered.

Step 403: set flow rate M based on chilled water on evaporator side _f Measured water inlet temperature T _enter And the measured outlet water temperature T _exit Controlling the operation of the centrifugal refrigerator.

Step 404: generating an alarm indication that the measured inlet water temperature exceeds a set range.

Fig. 5 is a flow chart of a method for controlling a centrifugal chiller according to further embodiments of the present application.

Step 501: obtaining the measured flow M of chilled water at the evaporator side of a centrifugal refrigerator _v And the measured water inlet temperature T _enter 。

Step 502: determining the actual measured inlet water temperature T _enter If within the set range, step 503 is entered, otherwise step 505 is entered.

Step 503: the equivalent inlet temperature T of chilled water at the evaporator side under variable flow working condition is determined by taking the constant flow working condition of the centrifugal refrigerator as a reference _v . As described above, the equivalent intake temperature of chilled water at the evaporator side under variable flow conditions can be determined by making the refrigeration capacity of the centrifugal refrigerator under variable flow conditions equal to the refrigeration capacity under fixed flow conditions. The specific determination of the equivalent inlet water temperature is described in detail above and will not be repeated here.

Step 504: based on the measured flow M of chilled water at the evaporator side _v Equivalent water inlet temperature T _v And the measured outlet water temperature T _exit Controlling the operation of the centrifugal refrigerator.

Step 505: generating an alarm indication that the measured inlet water temperature exceeds a set range.

According to another aspect of the present application, there is also provided a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, realizes the steps involved in the control method described above with the aid of fig. 3-5.

Those of skill would appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both.

To demonstrate interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Implementation of such functionality in hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

Although only a few specific embodiments of this application have been described, those skilled in the art will appreciate that this application may be embodied in many other forms without departing from the spirit or scope thereof. Accordingly, the illustrated examples and embodiments are to be considered as illustrative and not restrictive, and the application is intended to cover various modifications and substitutions without departing from the spirit and scope of the application as defined by the appended claims.

The embodiments and examples set forth herein are presented to best explain the embodiments in accordance with the present technology and its particular application and to thereby enable those skilled in the art to make and use the application. However, those skilled in the art will recognize that the foregoing description and examples have been presented for the purpose of illustration and example only. The description as set forth is not intended to cover various aspects of the application or to limit the application to the precise form disclosed.

Claims

1. A method for controlling a centrifugal chiller, comprising the steps of:

2. The method of claim 1, further comprising:

3. The method of claim 1, wherein in step a, the measured flow rate is obtained by reading a measurement of the flow rate from a flow meter or a differential pressure sensor provided in a chilled water line flowing through the evaporator.

4. A method according to any one of claims 1-3, wherein in step B the equivalent inlet temperature of the chilled water on the evaporator side in variable flow conditions is determined by making the refrigeration capacity of the centrifugal chiller in variable flow conditions equal to the refrigeration capacity in fixed variable flow conditions.

5. The method of claim 4, wherein in step B, the equivalent feed water temperature of chilled water at the evaporator side for variable flow conditions is determined as follows:

6. A method as claimed in any one of claims 1 to 3, further comprising:

7. A control device for a centrifugal chiller, comprising:

a memory;

a processor; and

8. The control device of claim 7, wherein execution of the computer program further causes the following operations:

9. The control device of claim 7, wherein the computer program is operative to obtain the measured flow rate of chilled water at the evaporator side in the following manner: the measured flow rate is obtained by reading a measurement value of the flow rate from a flow meter or a differential pressure sensor provided in the chilled water line flowing through the evaporator.

10. A control apparatus as claimed in any one of claims 7 to 9 wherein the computer program is operable to determine the equivalent inlet temperature of chilled water on the evaporator side in variable flow conditions by equating the refrigeration capacity of the centrifugal chiller in variable flow conditions to the refrigeration capacity in fixed flow conditions.

11. The control device of claim 10, wherein the operation of the computer program further causes the equivalent inlet water temperature of chilled water on the evaporator side to be determined under variable flow conditions by:

12. The control device of any of claims 7-9, wherein execution of the computer program further causes the following:

13. An air conditioning system, comprising:

a centrifugal refrigerator; and

a control device as claimed in any one of claims 7 to 12.

14. A computer readable storage medium having instructions stored therein, which when executed by a processor, cause the processor to perform the method of any of claims 1-6.