CN113775490B

CN113775490B - Design method of centralized water cooling system of wind generating set

Info

Publication number: CN113775490B
Application number: CN202111140169.3A
Authority: CN
Inventors: 贺国凌; 张洪溢; 肖长远; 余民姚
Original assignee: CSIC Haizhuang Windpower Co Ltd
Current assignee: CSIC Haizhuang Windpower Co Ltd
Priority date: 2021-09-28
Filing date: 2021-09-28
Publication date: 2023-04-18
Anticipated expiration: 2041-09-28
Also published as: CN113775490A

Abstract

The invention provides a design method of a centralized water cooling system of a wind generating set, which comprises the following steps: respectively acquiring the maximum allowable inlet water temperature of a cooling part of a heating component; judging the temperature difference between any two allowable inlet water temperatures, and if the temperature difference between every two allowable inlet water temperatures is larger than a reference value, serially connecting the cooling parts of the heating parts according to the sequence of the allowable inlet water temperatures from low to high; if at least one value in the temperature difference between every two allowable inlet water temperatures is larger than a reference value, the cooling parts of the two heating parts with the closest allowable inlet water temperatures are connected in parallel and then connected in series with the cooling part of the heating part with the largest difference in the inlet water temperatures; if the temperature difference between the two allowable inlet water temperatures is not greater than the reference value, the cooling parts of the heating parts are all arranged in parallel. The system principle layout and each node parameter design for the centralized cooling of the generator, the frequency converter and the transformer provide support for the development and application of the centralized water cooling system of the generator, the frequency converter and the transformer.

Description

Design method of centralized water cooling system of wind generating set

Technical Field

The invention relates to the technical field of wind power generation, in particular to a design method of a centralized water cooling system of a wind generating set.

Background

With the continuous development of wind generating sets towards the direction of large megawatt and offshore development, the installation positions of generators, transformers and converters of more and more sets are turned from the previous dispersed positions at a tower foundation and an engine room to be installed in the engine room in a centralized manner, so that the development of a centralized water cooling system for the three parts has greater feasibility. At present, a generator cooling system, a frequency converter cooling system and a transformer cooling system of a wind generating set in the industry are mutually independent, and each part is provided with an independent heat dissipation tail end, a water supply device, a connecting pipeline and a related sensor. The equipment has more parts, the initial investment cost of the equipment is higher, the fault points are increased, the maintenance cost of the unit is increased, particularly for the offshore unit, the cost of one-time offshore maintenance is not low, and the cost of the equipment can be possibly reached by the operation and maintenance cost of the unit for several times.

Disclosure of Invention

In view of this, the present invention provides a method for designing a centralized water cooling system of a wind turbine generator system, which is used for designing the system principle layout and the parameters of each node of the centralized cooling system of a generator, a frequency converter and a transformer, and provides theoretical support for the development and application of the centralized water cooling system of the generator, the frequency converter and the transformer.

The invention solves the technical problems by the following technical means: the invention provides a design method of a centralized water cooling system of a wind generating set, which is used for cooling a generator, a frequency converter and a transformer of heating parts of the wind generating set and comprises the following steps:

maximum allowable inlet water temperatures T1, T2, and T3 of a cooling portion of a heat generating component are acquired, respectively;

judge the difference in temperature T between arbitrary two allowwed entry water temperatures to set up difference in temperature benchmark N, compare difference in temperature T and benchmark N:

if the temperature difference between every two allowable inlet water temperatures is larger than a reference value N, serially connecting the cooling parts of the heating parts according to the sequence of the allowable inlet water temperatures from low to high;

if at least one value in the temperature difference between every two allowable inlet water temperatures is larger than a reference value, and at least one value is smaller than the reference value, the cooling parts of the two heating parts with the closest allowable inlet water temperatures are connected in parallel and then connected in series with the cooling part of the heating part with the largest difference in the inlet water temperatures;

if the temperature difference between the two allowable inlet water temperatures is not greater than the reference value N, the cooling parts of the heating parts are all arranged in parallel.

Furthermore, the cooling liquid flows through the cooling parts of the three heat generating components and then flows back through the water pump and the radiator to form a closed cycle, and meanwhile, a flow regulating mechanism is arranged in parallel on the cooling part of each heat generating component for controlling the actual flow of the heat generating component to be kept at the rated flow for operation.

Further, if the temperature difference between every two allowable inlet water temperatures is larger than a reference value N, and if the temperature difference between every two allowable inlet water temperatures is larger than the reference value N, the cooling parts of the heating parts are serially connected in the sequence from the allowable inlet water temperatures to the allowable inlet water temperatures, and the rated total flow of the cooling system is set according to the following steps:

judging the magnitude of the coolant outflow temperature of the first cooling part and the permissible inlet temperature of the second cooling part according to the flow sequence of the coolant;

increasing the total flow by increasing the flow of the bypass branches which are connected in parallel with the corresponding cooling parts until the total flow is equal to the total flow, and simultaneously obtaining a system total flow I;

then, judging the rated flow of the first cooling component and the second cooling component, and increasing the total flow by increasing the flow of a bypass branch which is connected with the component with smaller flow in parallel so as to enable the total flow of the system to be equal to the rated flow of the component with larger flow;

then judging the temperature of the cooling liquid flowing out of the second cooling component and the allowable inlet temperature of the third component;

increasing the flow of a flow regulating mechanism connected with the first cooling component or/and the second cooling component in parallel, so that the temperature of the cooling liquid flowing out of the second cooling component is equal to the allowable inlet temperature of the third component, and obtaining a total system flow rate II;

the rated total flow of the system is determined according to the rated flow sizes of the second cooling component, the third cooling component and the three cooling components.

Further, if at least one value of the temperature difference between the two allowable inlet water temperatures is greater than a reference value, and at least one value of the temperature difference is smaller than the reference value, the cooling parts of the two heating components with the closest allowable inlet water temperatures are connected in parallel and then connected in series with the cooling part of the heating component with the largest difference in the inlet water temperatures, and the rated total flow of the cooling system is set according to the following steps:

firstly, determining the sum of rated flow of two parallel components and the water temperature of mixed cooling water at the outlet of the parallel components;

comparing the water temperature of the mixed cooling water with the inlet allowable water temperature of the serial cooling part:

if the water temperature of the cooling water is higher than the inlet allowable water temperature of the serial cooling part, the total flow is increased by changing the flow of the flow regulating mechanism of the bypass branch of the parallel cooling part until the total flow is equal to the rated flow of the serial part, and the rated total flow of the cooling system is the rated flow of the serial part at this moment;

if the water temperature of the cooling water is not more than the inlet allowable water temperature of the serial cooling part, and the sum of the rated flow rates of the two parallel components is less than the flow rate of the serial cooling part, increasing the flow rate of the flow rate adjusting mechanism of the bypass branch of the parallel cooling component to increase the total flow rate until the total flow rate is equal to the rated flow rate of the serial component, and at the moment, the rated total flow rate of the cooling system is the rated flow rate of the serial component;

if the water temperature of the cooling water is not more than the inlet allowable water temperature of the serial cooling part and the sum of the rated flow rates of the two parallel components is more than or equal to the flow rate of the serial cooling part, the rated total flow rate of the cooling system is the sum of the rated flow rates of the parallel components.

Further, if the temperature difference between every two allowable inlet water temperatures is not greater than the reference value N, the rated total flow of the cooling system is the sum of the rated flows of all the cooling parts.

According to the technical scheme, the invention has the beneficial effects that: the invention provides a design method of a centralized water cooling system of a wind generating set, which is used for cooling a generator, a frequency converter and a transformer of heating parts of the wind generating set and comprises the following steps: maximum allowable inlet water temperatures T1, T2 and T3 of a cooling part of a heating component are respectively obtained; judge the difference in temperature T between arbitrary two allowwed entry water temperatures to set up difference in temperature benchmark N, compare difference in temperature T and benchmark N: if the temperature difference between every two allowable inlet water temperatures is larger than a reference value N, serially connecting the cooling parts of the heating parts according to the sequence of the allowable inlet water temperatures from low to high; if at least one value in the temperature difference between every two allowable inlet water temperatures is larger than a reference value, and at least one value is smaller than the reference value, the cooling parts of the two heating parts with the closest allowable inlet water temperatures are connected in parallel and then connected in series with the cooling part of the heating part with the largest difference in the inlet water temperatures; if the temperature difference between every two allowable inlet water temperatures is not greater than the reference value N, the cooling parts of the heating parts are all arranged in parallel. The system principle layout and each node parameter design for the centralized cooling of the generator, the frequency converter and the transformer provide theoretical support for the development and application of the centralized water cooling system of the generator, the frequency converter and the transformer.

Drawings

In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings used in the detailed description or the prior art description will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.

FIG. 1 is a flow chart of the present invention;

FIG. 2 is a schematic diagram of a cooling system according to a first embodiment of the present invention;

FIG. 3 is a flowchart illustrating a design process according to a first embodiment of the present invention;

FIG. 4 is a schematic diagram of a cooling system according to a second embodiment of the present invention;

FIG. 5 is a design flowchart of a second embodiment of the present invention;

FIG. 6 is a schematic diagram of a cooling system according to a third embodiment of the present invention;

FIG. 7 is a flow chart of an embodiment of the present invention;

reference numerals: 1-a flow regulating mechanism.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.

Referring to fig. 1 to 7, a method for designing a centralized water cooling system of a wind turbine generator system is used for cooling a generator, a frequency converter and a transformer of a heating component of the wind turbine generator, and includes the following steps:

the cooling requirements of the heating source of the wind driven generator are obtained according to the selected models of the generator, the frequency converter and the transformer of the wind driven generator as shown in the following table:

	generator	Frequency converter	Transformer device
				Heating power/kW	Q1	Q2	Q3
Maximum inlet water temperature/° c allowed	T1	T2	T3
				Rated flow/(L/min)	q1	q2	q3

if the temperature difference between every two allowable inlet water temperatures is larger than a reference value N, serially connecting the cooling parts of the heating parts according to the sequence of the allowable inlet water temperatures from low to high; meanwhile, a regulating valve is arranged in parallel on each heat generating component to control the flow of the cooling liquid, so that the actual flow of the three components is kept to be operated at the rated flow. The flow regulating mechanism is a regulating valve.

Specifically, due to the fact that the maximum inlet water temperature difference allowed by the three components is large, the cooling equipment is cooled by using water temperatures with different gradients.

In the first embodiment, if the comparison result of the temperature difference between any two allowable inlet water temperatures is T1-T2> N and T2-T3> N, the cold utilization devices are distributed in series, and according to the sequence of the inlet temperatures from low to high, the cooling liquid firstly enters the transformer, passes through the frequency converter and finally flows through the generator. The cooling liquid from the generator is delivered back to the transformer by a water pump after passing through the radiator, so as to form closed circulation. The temperature values of the cooling liquid after passing through the generator, the frequency converter and the transformer are respectively t1, t2 and t3, and q0 is the rated flow finally determined by the system;

firstly, the system flow is set according to the rated flow q3 of the transformer of the lowest part of the inlet water temperature, and whether the temperature value T3 of the cooling liquid flowing through the transformer is larger than the maximum allowable inlet water temperature T2 of the frequency converter is judged:

if T3> T2, increasing the flow by adding a transformer bypass branch until T3= T2, wherein the total flow is q4, and if q4> q2, adjusting the flow of the bypass branch of the frequency converter to adjust the total flow so that the total flow q4= q2; then, judging the temperature value T2 of the cooling liquid flowing through the frequency converter and the maximum allowable inlet water temperature T1 of the generator: if T2> T1, increasing the total flow until T2 is less than or equal to T1, wherein the total flow is q5, and if q5 is less than q1, the rated flow q0 finally determined by the system is = q1; if q5= q1, the rated flow rate q0 finally determined by the system = q5; if q5< q1, the flow is increased by increasing the flow through the generator bypass branch until the total flow through the generator equals q5, then the system finalizes the rated flow q0= q5.

If q4< q2, adjusting the total flow by adjusting the bypass branch flow of the transformer so that the total flow q4= q2; simultaneously recording the flow value of a bypass branch of the transformer and the regulating value of each time; then, judging the temperature value T2 of the cooling liquid flowing through the frequency converter and the maximum allowable inlet water temperature T1 of the generator: if T2> T1, the total flow is increased by adding the bypass branch of the frequency converter until T2= T1, at which time the total flow is q5: if q5< q1, the rated flow q0 finally determined by the system = q1; if q5= q1, the rated flow rate q0 finally determined by the system = q5; if q5 is less than q1, increasing the flow by increasing the flow of the bypass branch of the generator until the total flow is equal to q5, and then finally determining the rated flow q0= q5 by the system; if T2< T1 and q2< q1, increasing the total flow by increasing the flow of the bypass branch of the frequency converter until the total flow is equal to q1, and then finally determining a rated flow q0= q1 by the system; if T2< T1 and q2= q1, the rated flow rate q0= q2 finally determined by the system; if T2< T1 and q2> q1, the total flow rate is increased by increasing the flow rate of the generator bypass branch until the total flow rate equals q2, and the rated flow rate q0= q2 finally determined by the system.

If T3 is less than or equal to T2 and q3 is more than or equal to q2, increasing the flow of a bypass branch of the frequency converter to increase the total flow until the total flow is equal to q3, and then judging the temperature value T2 of the cooling liquid flowing through the frequency converter and the maximum allowable inlet water temperature T1 of the generator; if T2> T1, increasing the total flow until T2= T1 by adding the theory of the frequency converter and the transformer bypass branch, wherein the total flow is q5, and if q5< q1, the rated flow q0 finally determined by the system is = q1; if q5= q1, the rated flow q0 finally determined by the system is = q5; if q5< q1, increasing the flow by increasing the flow of the bypass branch of the generator until the total flow equals q5, and then the system finally determines the rated flow q0= q5;

if T3 is less than or equal to T2 and q3 is less than q2, increasing the total flow by increasing the flow of the transformer bypass branch until the total flow is equal to q2; then, judging the temperature value T2 of the cooling liquid flowing through the frequency converter and the maximum allowable inlet water temperature T1 of the generator; if T2> T1, the total flow is increased by adding the bypass branch of the frequency converter until T2= T1, at which time the total flow is q5: if q5< q1, the rated flow q0 finally determined by the system = q1; if q5= q1, the rated flow rate q0 finally determined by the system = q5; if q5< q1, increasing the flow by increasing the flow of the bypass branch of the generator until the total flow equals q5, and then the system finally determines the rated flow q0= q5; if T2< T1 and q2< q1, increasing the total flow by increasing the flow of the bypass branch of the frequency converter until the total flow is equal to q1, and then finally determining a rated flow q0= q1 by the system; if T2< T1 and q2= q1, the rated flow rate q0= q2 finally determined by the system; if T2< T1 and q2> q1, the total flow is increased by increasing the flow of the generator bypass branch until the total flow equals q2, the rated flow q0 that the system finally determines = q2.

In a specific embodiment, the outlet water temperature actually flowing through the transformer, the frequency converter and the generator coolant is calculated to be t1, t2 and t3 according to a heat balance formula Q = Q · ρ · cp · Δ t, wherein: q is the heating value of the heating component, and Q is the flow rate flowing through the heating component; ρ is the coolant density; cp is the specific heat capacity at constant pressure of the cooling liquid; Δ t is the temperature difference before and after the coolant flows through the heat generating component.

In a certain wind generating set, a generator, a frequency converter and a transformer of the wind generating set are cooled in an air-water cooling mode, and input parameters are shown in the following table; wherein the value of N is 2 ℃.

	Generator	Frequency converter	Transformer device
				Number of cabinets/	1	2	1
Heating power/kW of each cabinet body	230	100	80
				Maximum permissible inlet water temperature/° c	55	50	45
Rated flow/(L/min) of each cabinet body	450	300	260
				Internal pressure loss per bar at rated flow	1	2	0.52

According to the parameters, the system belongs to the first embodiment, the cold utilization equipment is distributed in series according to the first embodiment, the cooling liquid firstly enters the transformer, then passes through the frequency converter, then passes through the generator and finally passes through the radiator and then is conveyed back to the transformer by the water pump according to the sequence that the inlet temperature is from low to high, and closed circulation is formed. Then, the centralized cooling system is designed according to the flow chart of the first embodiment, specifically, as shown in fig. 7, the system flow is selected according to the transformer flow, the inlet water temperature is required to be 45 ℃ according to the maximum inlet water temperature allowed by the transformer, the cooling liquid flows into the transformer at 45 ℃, after the heat of the transformer is taken away, the water temperature rises by 4.4 ℃, the outlet water temperature of the transformer is 49.4 ℃, the requirement of the inlet water temperature of the frequency converter is met, but because the rated flow of the frequency converter is 600L/min and is greater than the system flow at the moment, a transformer bypass adjusting branch needs to be added, the system flow is kept at 600L/min, and the outlet water temperature of the transformer at the moment is 46.9 ℃. After the cooling liquid flows through the frequency converter, the water temperature rises by 4.8 ℃, the water temperature at the outlet of the frequency converter is 51.7 ℃ and is less than the maximum inlet water temperature of the generator by 55 ℃, the cooling requirement of the generator is met, and the cooling liquid can directly flow into the generator. Because the flow of the converter is greater than the rated flow of the generator, a bypass adjusting branch of the generator needs to be added, the flow of the system is kept at 600L/min, and the water temperature at the outlet of the generator is 57.2 ℃. The radiator reduces the temperature of the cooling liquid at the outlet of the generator from 57.2 ℃ to 45 ℃, and then the cooling liquid flows back to the transformer. The scheme adopts a series connection mode, the temperature difference between the front and the rear of the radiator is 12.2 ℃, and the total pressure loss of the main body component is delta P =deltaP 1 +. DELTA P2 +. DELTA P3 +. DELTA P4=4.6bar.

In the second embodiment, if at least one value of the temperature difference between every two allowable inlet water temperatures is greater than the reference value, and at least one value of the temperature difference is smaller than the reference value, the cooling parts of the two heating components with the closest allowable inlet water temperatures are connected in parallel and then connected in series with the cooling part of the heating component with the largest difference between the inlet water temperatures;

two heating components, namely a frequency converter and a transformer, with the inlet water temperature requirement close are connected in parallel, and then connected in series with a generator with the inlet water temperature difference larger, so that the total flow of parallel branches of the generator and the frequency conversion transformer can be balanced while different gradient water temperatures are fully utilized. Assuming that T2-T3 is more than or equal to 0 and less than or equal to N, and T1-T2 is more than N (variables are interchanged, the design method is similar), according to the sequence that the inlet temperature is from low to high, the cooling liquid simultaneously flows through the frequency converter and the transformer, the outlet water temperatures are T2 and T3 respectively, the mixed water temperature is T4, and then flows through the generator, and the outlet water temperature of the generator is T5. And finally, the water is conveyed back to the frequency converter and the transformer by the water pump after passing through the radiator to form closed circulation, wherein the frequency converter and the transformer are respectively provided with a regulating valve for controlling the actual flow of the frequency converter and the transformer to be rated flow. The regulating valve connected with the generator in parallel and the regulating valve connected with the frequency converter in parallel jointly act to control the actual flow of the generator to be the rated flow.

Specifically, the system flow is set according to the sum of rated flows of a frequency converter and a transformer, and the magnitudes of T4 and T1 are judged:

if T4> T1, increasing the total flow by increasing the transformer bypass branch until T4= T1, at which time the total flow is q4, and if q4< q1, increasing the transformer bypass branch flow until q4= q1, and finally determining a rated flow q0= q1 by the system; if q4 is more than or equal to q1, the rated flow q0 finally determined by the system is = q4.

If T4 is less than or equal to T1 and q2+ q3 is less than q1, increasing the flow by adding a transformer bypass branch until the total flow is equal to q1, and finally determining the rated flow q0= q1 by the system;

and if T4 is less than or equal to T1 and q2+ q3 is more than or equal to q1, increasing the total flow by increasing the bypass branch flow of the power generation rack until the total flow is equal to q2+ q3, and finally determining the rated flow q0= q2+ q3 by the system.

Wherein q0 is the rated flow rate finally determined by the system. When the branch is added to the heating component to adjust the flow, the heating component is ensured to operate under the rated flow. By the design method, the schematic diagram and the flow distribution design relation corresponding to the centralized cooling system under the initial condition of the second condition and in various different states can be finally obtained, and reference is provided for the establishment of the centralized cooling system and the model selection of each part.

In the third embodiment, if the temperature difference between the two allowable inlet water temperatures is not greater than the reference value N, the cooling parts of the heating parts are all arranged in parallel; according to the characteristic that the inlet water temperature is close to the requirement, the generator, the frequency converter and the transformer are connected in parallel, so that cooling liquid with the same water temperature flows into the cooling equipment at the same time. The water temperature of the inlet of the cold equipment is selected according to the minimum value of the maximum water temperatures allowed by the generator, the frequency converter and the transformer, and the schematic diagram is shown in the figure if the water temperature of the inlet of the transformer is the minimum. The cooling liquid flows through the generator, the frequency converter and the transformer according to the water temperature of T3. The actual flow of the generator, the frequency converter and the transformer is controlled to be rated flow through the regulating valve of each branch, the water temperature of outlets of the generator, the frequency converter and the transformer is t1, t2 and t3 respectively, the water temperature after mixing is t4, and the cooling liquid passes through the radiator and is conveyed back to the generator, the frequency converter and the transformer by the water pump to form closed circulation. Total system flow q0= q1+ q2+ q3.

By the design method, the model selection requirements of the main component for realizing the system function, the system arrangement, the flow and temperature conditions of each node in the system can be obtained, and a radiator with corresponding cooling capacity, a water pump with corresponding performance and the like are configured according to the design result. And auxiliary monitoring equipment such as temperature and flow sensors with proper measuring ranges can be matched.

The centralized water cooling system obtained by the method can share a heat dissipation tail end with the three water cooling systems of the generator cooling system, the frequency converter cooling system and the transformer cooling system, adopts a water supply device, a set of pipelines and a set of sensors, integrates and utilizes resources, and has lower probability of failure and lower cost due to the reduction of cooling parts. Finally, the purposes of reducing equipment and maintenance cost and improving the operation reliability of the unit are achieved.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being covered by the appended claims and their equivalents.

Claims

1. A design method of a centralized water cooling system of a wind generating set is used for cooling a generator, a frequency converter and a transformer of heating components of the wind generating set, and is characterized in that: the method comprises the following steps:

2. The design method of the centralized water cooling system of the wind generating set according to claim 1, wherein the cooling liquid flows through the cooling parts of the three heat generating components and then flows back through the water pump and the heat sink to form a closed cycle, and meanwhile, a flow regulating mechanism is arranged in parallel on the cooling part where the cooling liquid flows through each heat generating component to control the actual flow of the heat generating components to be kept at the rated flow for operation.

3. The design method of the centralized water cooling system of the wind generating set according to claim 2, wherein if the temperature difference between every two allowable inlet water temperatures is greater than a reference value N, and if the temperature difference between every two allowable inlet water temperatures is greater than the reference value N, the cooling parts of the heat generating components are arranged in series according to the sequence of the allowable inlet water temperatures from low to high, and the rated total flow of the cooling system is set according to the following steps:

increasing the total flow by increasing the flow of the bypass branches which are connected in parallel with the corresponding cooling parts until the total flow is equal to the bypass branches, and simultaneously obtaining a system total flow I;

and determining the rated total flow of the system according to the rated flow of the second cooling component, the rated flow of the third cooling component and the rated flow of the three cooling components.

4. The design method of the centralized water cooling system of the wind generating set according to claim 2, wherein if at least one value of the temperature difference between two pairs of the allowable inlet water temperatures is greater than a reference value and at least one value is smaller than the reference value, the cooling parts of the two heat generating components with the closest allowable inlet water temperatures are connected in parallel and then connected in series with the cooling part of the heat generating component with the largest difference in the inlet water temperatures, and the rated total flow rate of the cooling system is set according to the following steps:

5. The design method of the centralized water cooling system of the wind generating set according to claim 2, wherein if the temperature difference between the two allowable inlet water temperatures is not greater than the reference value N, the rated total flow of the cooling system is the sum of the rated flows of all the cooling parts.