阅读说明：本技术 用于并联冷水系统的水冷机组及水泵的变台数控制方法 (Water cooling unit for parallel cold water system and variable station number control method of water pump ) 是由 周旭辉 于 2020-07-16 设计创作，主要内容包括：本发明属于中央空调调控的技术领域,公开了一种用于并联冷水系统的水冷机组及水泵的变台数控制方法,应用于末端负荷减少的工况下,计算末端负荷变化后所需冷水机组与水泵的运行台数m,结合末端负荷变化前所需冷水机组与水泵的运行台数n,确定水泵运行台数变化过程中通过单台水泵的最大流量Q<Sub>max</Sub>,判断最大流量Q<Sub>max</Sub>是否超过单台水泵运行允许通过的最大流量,若是,则采用逐级减少规则确定最终所需运行台数；若否,则最终所需运行台数即为m。(The invention belongs to the technical field of central air conditioning regulation and control, and discloses a water cooling unit and water pump station changing number control method for a parallel cold water system, which is applied to the working condition of reducing the tail end load, calculates the running number m of the water cooling unit and the water pump after the tail end load changes, and determines the maximum flow Q of a single water pump in the process of changing the running number of the water pump by combining the running number n of the water cooling unit and the water pump before the tail end load changes max Judging the maximum flow Q max Whether the maximum flow allowed by the operation of a single water pump is exceeded or not, if yes, determining the number of the finally required operation units by adopting a step-by-step reduction rule; if not, the number of the finally needed operation units is m.)

1. A control method for the number of the water cooling units and the water pumps connected in parallel is characterized in that: the method is applied to the working condition of reducing the tail end load, the number m of the running water pumps and the number n of the running water pumps and the number of the cold water sets required after the tail end load changes are calculated, and the maximum flow Q of the water pumps passing through a single water pump in the process of changing the number of the running water pumps is determined by combining the number n of the running water pumps and the number n of the running water sets_maxJudging the maximum flow Q_maxWhether the maximum flow allowed by a single pump operation is exceeded,if yes, determining the number of the finally needed operation stations by adopting a step-by-step reduction rule; if not, the number of the finally needed operation units is m.

2. The method for controlling the number of the water chilling units and the water pumps connected in parallel according to claim 1, wherein the method comprises the following steps: the step-by-step reduction rule is set to be that if the maximum flow Q_maxIf the maximum flow rate allowed by the operation of a single water pump is exceeded, the number of the required operation units is modified into m +1, and the maximum flow rate Q of the single water pump passing through the process of changing the number of the operation units n → m +1 and m +1 → m is calculated respectively_maxContinuously judging Q_maxWhether the maximum flow allowed by the operation of a single water pump is exceeded or not, if not, the number change scheme n → m +1 → m can be directly executed; if the number of the channels exceeds the preset value, modifying the number change scheme to be n → m +2 → m, repeating the process and continuing the judgment, and the like.

3. The method for controlling the number of the water chilling units and the water pumps connected in parallel according to claim 2, wherein the method comprises the following steps: the maximum flow rate Q_maxThe water pump is determined by the characteristic parameters of the water pump and the number of the running water pumps required before and after the load change.

4. The method for controlling the number of the water chilling units and the water pumps connected in parallel according to claim 3, wherein the method comprises the following steps: the maximum flow rate Q is calculated using the following equation_max，

wherein the content of the first and second substances,

5. The method for controlling the number of the water chilling units and the water pumps connected in parallel according to claim 1, wherein the method comprises the following steps: and the water chilling units in the parallel water chilling system and the water pumps are connected in series one to one.

6. The method for controlling the number of the water chilling units and the water pumps connected in parallel according to claim 1, wherein the method comprises the following steps: the number m of the running water chilling units and the running water pumps required after the load at the tail end is changed is determined by the changed load and the refrigerating capacity of a single water chilling unit.

Technical Field

The invention relates to the technical field of central air conditioner regulation, in particular to a water cooling unit for a parallel cold water system and a method for controlling the number of a water pump to be changed.

Background

At present, a large and medium-sized refrigeration station system still widely adopts a variable-station-number control mode to adjust system load, compared with variable-speed adjustment, the variable-station-number control system not only has the advantages of simple control management, low investment cost and the like, but also can keep a water chilling unit to operate under a high-efficiency working condition on the premise of meeting the requirement of terminal load, but in the variable-station-number adjustment process of the water chilling unit, the overload phenomenon of a water pump corresponding to the water chilling unit often occurs due to the change of the pipeline characteristics of the system, and the stability of the system is influenced.

Disclosure of Invention

The invention provides a water cooling unit for a parallel cold water system and a control method for the number of the water pumps, which solve the problems that the number of the water cooling units is easy to overload in the adjustment process of the number of the water pumps of the existing water cooling unit.

The invention can be realized by the following technical scheme:

a water cooling unit and water pump station changing number control method for a parallel cold water system is applied to the working condition of reducing end load, the number m of running water pumps and water cooling units required after the end load changes is calculated, and the maximum flow Q of a single water pump passing through the water pump in the process of changing the number of running water pumps is determined by combining the number n of running water pumps and water cooling units required before the end load changes_maxJudging the maximum flow Q_maxWhether the maximum flow allowed by the operation of a single water pump is exceeded or not, if yes, determining the number of the finally required operation units by adopting a step-by-step reduction rule; if not, the number of the finally needed operation units is m.

Further, the step-by-step reduction rule is set to be that if the maximum flow Q is_maxIf the maximum flow rate allowed by the operation of a single water pump is exceeded, the number of the required operation units is modified into m +1, and the maximum flow rate Q of the single water pump passing through the process of changing the number of the operation units n → m +1 and m +1 → m is calculated respectively _maxContinuously judging Q_maxWhether the maximum flow allowed by the operation of a single water pump is exceeded or not, if not, the number change scheme n → m +1 → m can be directly executed; if the number of the channels exceeds the preset value, modifying the number change scheme to be n → m +2 → m, repeating the process and continuing the judgment, and the like.

Further, the maximum flow rate Q_maxThe water pump is determined by the characteristic parameters of the water pump and the number of the running water pumps required before and after the load change.

Further, the maximum flow rate Q is calculated using the following equation_max，

Taking the root of the plant,

wherein the content of the first and second substances,

A₀、B₀、C₀respectively represent a constant, H_{Forehead (forehead)}Representing the rated lift, Q, of a single pump_{Forehead (forehead)}Indicating the rated flow of a single water pump.

Further, the water chilling units in the parallel water chilling system and the water pumps are connected in series one to one.

Furthermore, the number m of the running water chilling units and the running water pumps required after the load at the tail end is changed is determined by the changed load and the refrigerating capacity of a single water chilling unit.

The beneficial technical effects of the invention are as follows:

the method for controlling the number of the variable stations can predict the maximum flow of the water pump in a short time in the process of working condition change in advance, thereby effectively avoiding the occurrence of the overload phenomenon of the water pump and ensuring the stable operation of the system.

Drawings

FIG. 1 is a general flow chart of the variable number control of the water chilling units and the water pumps in the parallel water chilling system of the invention;

FIG. 2 is a schematic diagram of the variation of the operating conditions of the water pumps in the parallel chilled water system of the present invention;

FIG. 3 is a graph illustrating water pump characteristics according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clear and complete, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The following detailed description of the preferred embodiments will be made with reference to the accompanying drawings.

As shown in figures 1 and 2, the invention provides a water chilling unit and a water pump platform changing number control method for a parallel cold water system, which are applied to the working condition that the end load is reduced, and the water chilling unit and the water pump needed after the end load is changed are calculatedDetermining the maximum flow Q of the water pump passing through the single water pump in the change process of the number of the running water pumps by combining the number m of the running water pumps with the number n of the running water pumps of the water chilling unit and the water pump required before the load change at the tail end _maxJudging the maximum flow Q_maxWhether the maximum flow allowed by the operation of a single water pump is exceeded or not, if yes, determining the number of the finally required operation units by adopting a step-by-step reduction rule; if not, the number of the finally needed operation units is m.

The step-by-step reduction rule is set to be that if the maximum flow Q_maxIf the maximum flow rate allowed by the operation of a single water pump is exceeded, the number of the required operation units is modified into m +1, and the maximum flow rate Q of the single water pump passing through the process of changing the number of the operation units n → m +1 and m +1 → m is calculated respectively_maxContinuously judging Q_maxWhether the maximum flow allowed by the operation of a single water pump is exceeded or not, if not, the number change scheme n → m +1 → m can be directly executed; if the number of the channels exceeds the preset value, modifying the number change scheme to be n → m +2 → m, repeating the process and continuing the judgment, and the like.

It should be noted that, the number modification scheme herein should minimize the time of the number changing process on the principle of ensuring that the number changing steps are as few as possible. For example, when n ═ m +3, then the order of the number of stations change scheme modifications should be: n → m, n → m +1 → m, n → m +2 → m +1 → m.

The water chilling units and the water pumps in the parallel water chilling system are connected in series one to one, namely the number of the running water chilling units and the running water pumps before and after load change is equal.

The number m of the running water chilling units and the running water pumps required after the load at the tail end is changed is determined by the changed load and the refrigerating capacity of a single water chilling unit.

Under the condition that the number of running water pumps is increased due to the increase of the load at the tail end, the single water pump cannot be overloaded, so that the discussion is not provided here, and the following emphatically discusses the process for determining the maximum flow of the single water pump under the working condition that the load at the tail end is reduced, and the specific steps are as follows:

assuming that a single water pump characteristic curve equation obtained by fitting according to water pump sample data is as follows:

H＝A₀Q²+B₀Q+C₀

wherein H is the pump lift, Q is the pump flow, A₀、B₀、C₀Are each a constant.

The characteristic curve equation of the m parallel water pumps is as follows:

the following can be obtained:

wherein H_m1Is the total lift, Q, of m parallel water pumps under the working condition of m1_m1The total flow of m parallel water pumps under m1 working conditions is shown.

The characteristics of the parallel system show that:

Q_n＝nQ_{forehead (forehead)},Q_m＝mQ_{Forehead (forehead)},H_n＝H_m＝H_{Forehead (forehead)}

Wherein H_{Forehead (forehead)}Rated lift, Q, of a single water pump_{Forehead (forehead)}The flow rate is the rated flow rate of a single water pump, Qn is the total flow rate of n parallel water pumps under the stable working condition, Qm is the total flow rate of m parallel water pumps under the stable working condition, Hn is the total lift of n parallel water pumps under the stable working condition, and Hm is the total lift of m parallel water pumps under the stable working condition.

Meanwhile, the system pipeline characteristics can obtain:

Thus:

order to

Obtaining:

(Zhenggen)

Therefore, the maximum flow of a single water pump at this time is as follows:

(Zhenggen)

Maximum flow rate Q_maxThe water pump is determined by the characteristic parameters of the water pump and the number of the running water pumps required before and after the load change.

In order to facilitate understanding of the above-described aspects of the present invention, the following detailed description will be given of the aspects of the present invention with reference to a specific embodiment.

Taking a certain newly-built freezing station project as an example, according to the design working condition of the system, the project is supposed to adopt a Keystin Omega series horizontal split double-suction pump as a freezing water pump, and the rated lift and rated flow of the project under the design working condition are respectively 18m and 1695m³H, maximum allowable flow rate of 2235m³H is used as the reference value. The freezing station adopts 5 2800RT cold water units to run in parallel, and the total load is 14000 RT.

Fig. 3 is a water pump characteristic curve obtained by fitting water pump sample data.

As shown in fig. 3, the characteristic curve equation of the water pump is:

H＝-5.8227×10^-6Q²+6.69622×10^-4Q+33.97087

namely:

A₀＝-5.8227×10^-6

B₀＝6.69622×10^-4

C₀＝33.97087

working condition 1:

when the load at the tail end is reduced to 8400RT, the number of the water chilling units and the water pumps needing to be started is 3, so that the maximum flow of the water pumps when the number of the water chilling units and the water pumps are changed into 5 → 3 needs to be calculated, and after the maximum flow of the water pumps is substituted into the formula, the maximum flow of the water pumps passing through a single water pump at the moment is 2093m ³H, not exceeding the water pumpMaximum flow allowed by row (2235 m)³H), therefore, the number of the water chilling units and the water pumps can be directly reduced from 5 to 3.

Working condition 2:

when the load at the tail end is as small as 5600RT, the number of the water chilling units and the water pumps needing to be started is 2, so that the maximum flow of the water pumps when the change scheme of the number of the water chilling units is 5 → 2 needs to be calculated, and after the maximum flow of the water pumps is substituted into the formula, the maximum flow of the water pumps passing through the single water pump at the moment is 2281m³H, exceeding the maximum flow allowed by the water pump operation (2235 m)³H), therefore, the number of the water pumps needs to be modified to 5 → 3 → 2, and the maximum flow rates of the water pumps are 2093m when 5 → 3 and 3 → 2 are calculated respectively³H and 2026m³No more than the maximum flow permitted by the pump operation (2235 m)³And h), the number change scheme is feasible, namely, in the change process of the numbers of the water chilling units and the water pumps, the number of the water chilling units and the water pumps needs to be changed from 5 to 3, and after the system is stable, the number of the water chilling units and the water pumps needs to be changed from 3 to 2.

In conclusion, by means of the technical scheme, the overload phenomenon of the water pump can be effectively avoided on the basis of shortening the process time of changing the number of the water pumps as much as possible, and the stable operation of the system is ensured.

Although specific embodiments of the present invention have been described above, it will be appreciated by those skilled in the art that these are merely examples and that many variations or modifications may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is therefore defined by the appended claims.