Flow rate determination without flow meter
The method determines fluid flow rate in data center cooling systems by measuring pressure drop across a reference section, addressing the inefficiencies and costs of mechanical flow meters, ensuring reliable and efficient operation.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- DANFOSS AS
- Filing Date
- 2025-12-08
- Publication Date
- 2026-06-18
Smart Images
Figure EP2025085895_18062026_PF_FP_ABST
Abstract
Description
[0001]
[0002] Flow rate determination without flow meter
[0003] The invention relates to a method for determining a flow rate of a fluid flow through a flow path, to an evaluation module for determining a flow rate of a fluid flow through a flow path, to a measurement system for determining a flow rate of a fluid flow through a flow path, and to a cooling distribution unit for a data center cooling system.
[0004] Due to the increasing demand for computing power, new data centers are built, and existing data centers are enlarged or updated. For example, the data centers are server farms, cloud computing centers, mainframe computers, and the like.
[0005] Such a data center includes parts of an IT infrastructure that generate heat during operation, e.g. server racks. Such parts of the IT infrastructure must be cooled in order to ensure proper and safer operation.
[0006] The efficient cooling of the IT infrastructure is a crucial aspect. Data centers, which house large amounts of computing equipment, generate significant amounts of heat that must be effectively managed to ensure the reliability and longevity of the IT infrastructure.
[0007] One common method for managing heat in data centers is to provide the data center with a data center cooling system that comprises an outer fluid circuit, one or more inner fluid circuits, and several cooling distribution units (CDlls) for thermal coupling between the inner fluid circuit(s) and the outer fluid circuit. The outer fluid circuit is sometimes referred to as facility system.
[0008] Such an inner fluid circuit provides cooling to relevant heat-generating parts of the IT infrastructure, for example via direct cooling of said parts, especially direct- to-chip liquid cooling. The inner fluid circuit is sometimes referred to as technology
[0009] December 2025 D 200 P 2657 WO cooling system loop (TCS loop). A first fluid is circulated in the inner fluid circuit. The first fluid can be also referred to as "coolant". Typically, the inner fluid circuit is a closed system.
[0010] The outer fluid circuit takes up heat from the inner fluid circuit and further dissipates the heat. For example, the outer fluid circuit can comprise air / water or wa- ter / water chillers or dry coolers to dissipate heat to the environment. A second fluid is circulated in the outer fluid circuit.
[0011] The data center cooling system typically includes several cooling distribution units for the heat exchange between the inner fluid circuits and the outer fluid circuit. Even a single inner fluid circuit can be thermally coupled to the outer fluid circuit by several cooling distribution units.
[0012] Each cooling distribution unit comprises an outer fluid section for fluid coupling with the outer fluid circuit, an inner fluid section for fluid coupling with the inner fluid circuit, and a heat exchanger for providing heat transfer between the outer fluid section and the inner fluid section. The inner fluid circuit has a pump for pumping the first fluid. The cooling distribution units, especially the heat exchangers, separate the first fluid from the second fluid.
[0013] Using several cooling distribution units, even for a single inner fluid circuit, allows for easy and flexible scaling of a cooling capacity of the inner fluid circuit and adds redundancy and thereby resilience to the entire system.
[0014] The cooling capacity of the inner fluid circuit is managed and controlled via the cooling distribution units that are fluidly coupled with the inner fluid circuit. It can be assumed that the cooling capacity of the inner fluid circuit is determined by the cooling capacities of the corresponding cooling distribution units. In each individual cooling distribution unit, the inner fluid section includes a flow meter that
[0015] December 2025 D 200 P 2657 WO measures a flow rate of the first fluid (the coolant) through the inner fluid section, a pump with a variable pump performance for pumping the first fluid, and a controller for controlling this pump. The flow rates through the inner fluid sections of the individual cooling distribution units add up to a common flow rate of the corresponding inner fluid circuit. Each cooling distribution unit can influence the cooling capacity provided by the inner fluid circuit, especially by changing a pump speed of its pump. Accordingly, the common flow rate in the inner fluid circuit can be controlled and optimal operating conditions can be ensured in the inner fluid circuit by means of the corresponding cooling distribution units.
[0016] Maximum flow rates in the cooling distribution units are high. Hence, the flow meters used in the cooling distribution units are large and expensive.
[0017] Further, mechanical flow meters exhibit a flow resistance. Even if the flow resistance is not high, it still reduces the efficiency of the cooling distribution unit. As the data centers and the cooling distribution units are typically operated nonstop, even small efficiency reductions can add up to significant additional power consumption over time. Apart from that, mechanical fluid meters can be prone to failure because they typically include movable parts. This can impair the reliability of the cooling distribution units.
[0018] One approach in order to get rid of the disadvantages of a mechanical flow meter is to employ a magnetic flow meter instead. However, suitable magnetic flow meters are particularly expensive. Accordingly, a price of the cooling distribution unit must be increased. Furthermore, the magnetic flow meter consumes some electric power for operation.
[0019] The problem underlying the invention to provide a cost-efficient and reliable estimation of the flow rate.
[0020] December 2025 D 200 P 2657 WO
[0021] This problem is solved by a method according to claim 1 .
[0022] It is a method for determining a flow rate of a fluid flow through a flow path, for example in a cooling distribution unit.
[0023] The method comprises:
[0024] - guiding the fluid flow through a reference section in the flow path;
[0025] - determining a pressure drop of the fluid flow over the reference section;
[0026] - determining the flow rate of the fluid flow based on the determined pressure drop and correlation information for the reference section, wherein the correlation information relates to at least one correlation between the flow rate through the reference section and the pressure drop of the fluid flow over the reference section.
[0027] The present invention provides a cost-efficient and reliable determination of the flow rate. Typically, the inner fluid section of a cooling distribution unit comprises measurement means that provide measurement signals that are indicative of the pressure drop anyways, for example a first pressure sensor upstream of the heat exchanger and a second pressure sensor downstream of the heat exchanger. The present invention can make use of these measurement means and measurement signals for determining the flow rate in a synergistic manner.
[0028] The method works without using a flow meter. The flow path can be free of a flow meter. Hence, there is no additional flow resistance, power consumption, and / or required space of a flow meter.
[0029] The correlation between the flow rate through the reference section and the pressure drop of the fluid flow over the reference section is known, at least for one pre-determined fluid composition that forms the fluid flow. The correlation
[0030] December 2025 D 200 P 2657 WO information reflects said correlation. The correlation information is used to determine the flow rate based on the pressure drop.
[0031] The fluid composition may consist of only one fluid or of several types of fluid. For example, the fluid composition can be pure water, a water-glycol-mixture, or another coolant fluid composition.
[0032] The pressure drop may be determined between a first location along the flow path and a second location along the flow path. The reference section is arranged in the flow path in-between the first location and the second location along the fluid flow. For example, the reference section may be arranged downstream of the first location and upstream of the second location.
[0033] The method, for example the step of determining the pressure drop, can comprise providing, with measurement means, measurement signals that are indicative of the pressure drop.
[0034] The measurement means can include a first pressure measurement means at the first location and a second pressure measurement means the second location. The measurement signals of the first pressure measurement means and the second measurement signals are (together) indicative of the pressure drop. Accordingly, determining the pressure drop can include measuring a first pressure at the first location with the first pressure measurement means and measuring a second pressure at the second location with the second pressure measurement means and calculating the pressure drop based on the (measurement signals) indicating the first pressure and (measurement signals indicating) the second pressure. The first pressure measurement means can include a pressure sensor, a pressure transducer, and / or a pressure transmitter. The second pressure measurement means can include a pressure sensor, a pressure transducer, and / or a pressure transmitter.
[0035] December 2025 D 200 P 2657 WO
[0036] Additionally or alternatively, determining the pressure drop can include measuring the pressure drop with a differential pressure sensor. The differential pressure sensor may directly measure a difference of the first pressure at the first location and the second pressure at the second location. Accordingly, the measurement means can include (and even consist of) the differential pressure sensor.
[0037] According to one aspect, the reference section is used as flow orifice / known contraction in the flow path.
[0038] The reference section may exhibit a maximum flow resistance and / or a minimum effective flow cross-section along the flow path, at least between the first location and the second location.
[0039] The first location can be directly at a beginning of the reference section (e.g. defined along a flow direction of the fluid flow).
[0040] Additionally or alternatively, the second location can be directly at an end of the reference section (e.g. defined along a flow direction of the fluid flow).
[0041] However, in general, the first location does not need to be directly at the beginning of the reference section as long as an intermediate section of the flow path between the first location and the beginning of the reference section has no substantial influence on the pressure drop.
[0042] Similarly, in general, the second location does not need to be directly at the end of the reference section as long as an intermediate section of the flow path between the end of the reference section and the second location has no substantial influence on the pressure drop.
[0043] December 2025 D 200 P 2657 WO
[0044] The reference section may have the only substantial influence on the pressure drop along the flow path between the first location and the second location.
[0045] In one embodiment, the reference section includes a flow branch of a heat exchanger (e.g. in cooling distribution unit). Especially, the reference section can (at least substantially) consist of the flow branch of the heat exchanger. For example, a liquid-to-liquid heat exchanger may have a first flow branch for a first fluid flow and a second flow branch for a second fluid flow. In one embodiment, the first flow branch is integrated into the flow path and used as the reference section. In another embodiment, the second flow branch is integrated into the flow path and used as the reference section.
[0046] It is also possible to use the method twice, for both sides (both flow branches) of the heat exchanger. This can include the following:
[0047] Guiding a first fluid flow through a first reference section including the first flow branch of the heat exchanger, determining a first pressure drop of the first fluid flow over the first reference section, and determining a first flow rate of the first fluid flow based on the determined first pressure drop and first correlation information for the first reference section, wherein the first correlation information relates to at least one correlation between the first flow rate through the first reference section and the first pressure drop of the first fluid flow over the first reference section; and guiding a second fluid flow through a second reference section including the second flow branch of the heat exchanger, determining a second pressure drop of the second fluid flow over the second reference section, and determining a second flow rate of the second fluid flow based on the determined second pressure drop and second correlation information for the second reference section, wherein the second correlation information relates to at least one correlation between the second flow rate through the second reference section and the second pressure drop of the second fluid flow over the second reference section.
[0048] December 2025 D 200 P 2657 WO
[0049] Naturally, the first correlation information and the second correlation information can be the same if the first flow branch and the second flow branch of the heat exchanger have the same flow characteristics and if the fluid compositions of the first fluid flow and the second fluid flow are the same.
[0050] In one embodiment, the flow path forms part of a cooling distribution unit for a data center cooling system. In more detail, the flow path can form part of an inner fluid section of the cooling distribution unit. The cooling distribution unit can include the heat exchanger. According to one aspect, the flow branch of the heat exchanger that forms part of the inner fluid section can be used as the reference section.
[0051] The method can include pumping the fluid flow by means of at least one pump, wherein the at least one pump is provided in the flow path upstream or downstream of the reference section. Especially, the pump can be located upstream of the first location and downstream of the second location. In other words, the pump is not arranged directly in-between the reference section and any one of the first location and the second location in the flow path. The pressure drop and / or the determined flow rate may be used for controlling the pump. The pump ensures a strong fluid flow through the fluid path. In tendency, a stronger fluid flow results in a larger pressure drop. This is beneficial for a high accuracy of the flow rate determination.
[0052] For example, the pump can form part of the inner fluid section of the cooling distribution unit.
[0053] The determined flow rate may be a mass flow rate, e.g. in units kg / s. Additionally or alternatively, the determined flow rate may be a volume flow rate, e.g. in units m3 / s.
[0054] December 2025 D 200 P 2657 WO
[0055] According to one aspect, the method may include estimating a heat transport capacity of the fluid flow based on the flow rate of the fluid flow and a specific heat capacity of the fluid composition of the fluid flow. The estimation might be done by multiplying the determined flow rate with the specific heat capacity. The estimation does not need to be performed as separate step. For example, the estimation (i.e. the multiplication of the determined flow with the specific heat capacity) may form part of a more complex estimation (e.g. the calculation of a heat transfer capacity of the fluid flow as described below). The heat transport capacity can be useful for control of in a HVAC system, for example for control of the cooling distribution unit, especially the pump thereof.
[0056] According to one aspect, the method may include determining at least one temperature of (the fluid in) the fluid flow in the flow path, e.g. a temperature of the fluid flow upstream of the reference section, a temperature of the fluid flow in the reference section, and / or a temperature of the fluid flow downstream of the reference section.
[0057] For example, the method may include measuring a first temperature of (the fluid in) the fluid flow at a first temperature location in the flow path upstream of the reference section, maybe directly upstream of the reference section. In this specific context, "directly upstream" might be understood in that no significant change of the temperature of (the fluid in) the fluid flow is to be expected between the first temperature location and (the beginning of) the reference section. The pump (if applicable) can be located upstream of the first temperature location.
[0058] Additionally or alternatively, the method may include measuring a second temperature of (the fluid in) the fluid flow at a second temperature location in the flow path downstream of the reference section, maybe directly downstream of the reference section. In this specific context, "directly downstream" might be
[0059] December 2025 D 200 P 2657 WO understood in that no significant change of the temperature of (the fluid in) the fluid flow is to be expected between (the end of) the reference section and the second temperature location. The pump (if applicable) can be located downstream of the second temperature location.
[0060] In one embodiment, the method includes determining a temperature difference between the temperature of (the fluid in) the fluid flow at the first temperature location (i.e. in the flow path upstream of the reference section, maybe directly upstream of the reference section), and the temperature of (the fluid in) the fluid flow at the second temperature location (i.e. in the flow path downstream of the reference section, maybe directly downstream of the reference section). The temperature difference might be measured directly (e.g. by a temperature difference sensor) and / or calculated based on the signals from the first temperature sensor and the second temperature sensor.
[0061] Said temperature difference might be referred to as the temperature drop (over the reference section).
[0062] According to one aspect, the method can include estimating a heat transfer capacity of the fluid flow based on the flow rate, the specific heat capacity, and the temperature drop. For example, the heat transfer capacity can be estimated by multiplying the heat transport capacity of the fluid flow with the temperature drop. The heat transfer capacity indicates how much heat is taken up by the fluid flow or given off from the fluid flow in the reference section. This is, for example, particularly useful if the reference section includes (or even consist of) one flow branch of the heat exchanger. The estimated heat transfer capacity can be used for controlling, e.g. for controlling a pump performance of the at least one pump, for example in the cooling distribution unit. In the data center cooling system, the heat transfer capacity indicates the present contribution of the cooling distribution
[0063] December 2025 D 200 P 2657 WO unit to a cooling capacity of the inner fluid circuit. Accordingly, the heat transfer capacity can be referred to as cooling capacity (of the cooling distribution unit).
[0064] The correlation information may include a non-linear function relating the flow rate to the pressure drop. The non-linearity allows for a more precise determination of the flow rate based on the determined pressure drop.
[0065] The (e.g. non-linear) function may include at least two different parameters, for example at least three parameters, maybe exactly three parameters. This facilitates a sufficiently precise modeling of the correlation.
[0066] According to one aspect, the non-linear function includes a term ((B / (2*A))2-(C- PRD) / A)A(1 / 2)-B / (2*A) relating the flow rate FLR with the pressure drop PRD, wherein A, B, and C are parameters, or a mathematical equivalent to this term.
[0067] The correlation information may cover correlations for different conditions, for example for different fluid compositions, temperatures, and / or viscosities of the fluid flow. This increases the versatility.
[0068] According to one aspect, the function is adapted to the different operational conditions, e.g. to the different fluid compositions, temperatures, and / or viscosities of the fluid flow, by modified parameters of the function.
[0069] As an example, a look-up table (or several look-up) tables with different parameters for the different operational conditions may be provided.
[0070] Additionally or alternatively, the correlation information may include information for adjusting one of, several, or all of the parameters depending on at least one of the operational conditions.
[0071] December 2025 D 200 P 2657 WO
[0072] According to one aspect, the correlation information includes information related to variations of the viscosity with temperature (e.g. using at least one look-up table and / or at least one formula). This information may be provided for at least one fluid composition, maybe for several (i.e. at least two) fluid compositions. With this information, the pressure drop can be determined more precisely, especially in the case of excessive temperature(s).
[0073] The correlation information may include information related to variations of a fluid density with temperature (e.g. using at least one look-up table and / or at least one formula). This information may be provided for at least one fluid composition, maybe for several (i.e. at least two) fluid compositions. With this information, the flow rate can be determined more precisely from the pressure drop, especially in the case of excessive temperature(s).
[0074] Additionally or alternatively, he correlation information can include information related to variations of the fluid density with pressure (e.g. at least one look-up table and / or at least one formula). This information may be provided for at least one fluid composition, maybe for several (i.e. at least two) fluid compositions. With this information, the flow rate can be determined more precisely from the pressure drop, especially in the case of excessive pressure(s).
[0075] As a further example, the correlation information can include information related to variations of the specific heat capacity with temperature and / or pressure (e.g. using at least one look-up table and / or at least one formula). This information may be provided for at least one fluid composition, maybe for several (i.e. at least two) fluid compositions. With this information, the heat transport capacity and / or the heat transfer capacity can be estimated more precisely.
[0076] The method may include generating and / or providing the correlation information based on the at least one correlation (if applicable: the several correlations)
[0077] December 2025 D 200 P 2657 WO between the flow rate through the reference section and the pressure drop of the fluid flow over the reference section.
[0078] According to one aspect, the method includes investigating the at least one correlation (if applicable: the several correlations) between the flow rate through the reference section and the pressure drop of the fluid flow over the reference section, e.g. by performing measurements and / or simulations. The measurements can be made with at least test specimen of the reference section that is representative for the reference section, e.g. identical to the reference section.
[0079] Correlations covering different operational conditions can be investigated with corresponding measurements and / or simulations. Correlation information covering the different operational conditions can be generated and / or provided based upon the investigations. For example, the correlation information may lead to different value(s) of the parameter A, the parameter B, and / or the parameter C for at least some different operational conditions.
[0080] The problem mentioned above is further solved by an evaluation module according to claim 12.
[0081] The evaluation module is for determining a flow rate of a fluid flow through a flow path, wherein the flow path is equipped with a reference section arranged in the flow path for guiding the fluid flow therethrough and measurement means for providing measurement signals that are indicative of a pressure drop of the fluid flow over the reference section, wherein the evaluation module includes a measurement interface for receiving the measurement signals and a processor, wherein the evaluation module is configured to retrieve correlation information for the reference section, wherein the correlation information relates to at least one
[0082] December 2025 D 200 P 2657 WO correlation between the flow rate through the reference section and the pressure drop of the fluid flow over the reference section, and wherein the evaluation module is configured to determine the flow rate of the fluid flow based on the measurement signals and the correlation information.
[0083] The modifications, embodiments, and the advantages described with respect to the method apply accordingly with respect to the evaluation module, and vice versa.
[0084] The evaluation module can be a controller of a cooling distribution unit.
[0085] The evaluation module can include a communication interface. The communication interface may be connected to the processor or form part of the processor. The communication interface may be configured for data exchange with external electronic devices. It may be configured for wired and / or wireless communications.
[0086] In one embodiment, the evaluation module includes a memory storing the correlation information. Additionally or alternatively, the evaluation module can include the communication interface and be configured to retrieve the correlation information from an external source. Storing the correlation information locally increases the versatility and reliability because it is not necessary to retrieve the correlation from the external source. Receiving the correlation information from the external source facilitates it to obtain correlation information for different fluid compositions and / or to use most recent correlation information. Naturally, both approaches can be combined. For example, the evaluation module can retrieve the correlation information from the external use and additionally store it in the memory (e.g. for the case of communication failure) and / or use it to update correlation information stored in in the memory.
[0087] December 2025 D 200 P 2657 WO
[0088] In one embodiment, the evaluation module includes the memory storing the correlation information, wherein the correlation information covers correlations for different fluid compositions, temperatures, and / or viscosities of the fluid flow. This increases the versatility of the evaluation module.
[0089] The problem mentioned above is further solved by a measurement system for determining a flow rate of a fluid flow through a flow path, wherein the measurement system includes a reference section arranged in the flow path for guiding the fluid flow therethrough and measurement means for providing measurement signals that are indicative of a pressure drop of the fluid flow over the reference section. The measurement system can include the evaluation module according to the present invention. Additionally or alternatively, the measurement system can be configured to perform the method according to the present invention.
[0090] In one embodiment, the pressure measurement means are mounted directly to a component including the reference section, for example to a heat exchanger.
[0091] The modifications, embodiments, and the advantages described with respect to the any one of the method and the evaluation module apply accordingly with respect to the measurement system, and vice versa.
[0092] The problem mentioned above is further solved by a cooling distribution unit for a data center cooling system, wherein the data center cooling system comprising an inner fluid circuit for providing cooling to parts of an IT infrastructure in a data center, and an outer fluid circuit for dissipating heat; wherein the cooling distribution unit comprises: an outer fluid section for fluid coupling with the outer fluid circuit; an inner fluid section for fluid coupling with the inner fluid circuit, wherein the inner fluid section comprises a pump; and
[0093] December 2025 D 200 P 2657 WO a heat exchanger for heat coupling between the outer fluid section and the inner fluid section.
[0094] The cooling distribution unit comprises the measurement system according to the present invention, wherein the measurement system includes an (e.g. inward) flow branch of the heat exchanger forming part of the inner fluid section as the reference section.
[0095] Additionally or alternatively, the cooling distribution unit is configured to perform the method according to the present invention.
[0096] The modifications, embodiments, and the advantages described with respect to the any one of the method, the evaluation module, and the measurement system apply accordingly with respect to the cooling distribution unit, and vice versa.
[0097] In general, the application of the present invention is not restricted to cooling distribution units.
[0098] Additional features, advantages and possible applications of the invention result from the following description of exemplary embodiments and the drawings. All the features described and / or illustrated graphically here form the subject matter of the invention, either alone or in any desired combination, regardless of how they are combined in the claims or in their references back to preceding claims.
[0099] Preferred embodiments of the invention will now be described with reference to the drawings, in which:
[0100] Fig. 1 schematically shows a data center cooling system with an inner fluid circuit for providing cooling to parts of an IT infrastructure in a data center, an outer fluid circuit for dissipating heat, and two cooling distribution units
[0101] December 2025 D 200 P 2657 WO for transferring heat from the inner fluid circuit to the outer fluid circuit and for pumping a first fluid in the inner fluid circuit, wherein each of the cooling distribution units determines a flow rate of a fluid flow through a flow path in the respective cooling distribution unit without using a flow meter;
[0102] Fig. 2 schematically shows an evaluation module that is implemented in each of the cooling distribution units of Fig. 1 ; and
[0103] Fig. 3 schematically shows a correlation between a flow rate through a reference section and the pressure drop of the fluid flow over the reference section.
[0104] Fig. 1 shows a data center cooling system 100 with an outer fluid circuit 70 and an inner fluid circuit 80.
[0105] The inner fluid circuit 80 provides cooling to parts 81 of an IT infrastructure in a data center. The parts 81 can, for example, include or consist of server racks. The inner fluid circuit 80 may be used for direct-to-chip liquid cooling in the parts 81. A first fluid is circulated in the inner fluid circuit 80. The first fluid can include water and / or glycol. For example, the first fluid can be a water-glycol-mixture.
[0106] The data center cooling system 100 includes at least one cooling distribution unit 1. Despite of Fig. 1 showing two cooling distribution units 1 , the data center cooling system 100 can also include only one cooling distribution unit 1 or more than two cooling distribution units 1.
[0107] The cooling distribution units 1 couple the inner fluid circuit 80 to the outer fluid circuit 70. In particular, in operation, the cooling distribution units 1 transfer heat from the inner fluid circuit 80 to the outer fluid circuit 70. The outer fluid circuit 70 dissipates the heat further, e.g. via outdoor heat exchangers (not shown) of the data center cooling system 100. A second fluid is circulated in the outer fluid
[0108] December 2025 D 200 P 2657 WO circuit 70. The second fluid can include water and / or glycol. For example, the second fluid can be a water-glycol-mixture. The second fluid and the first fluid can be of the same fluid composition or of different fluid compositions.
[0109] Further, the cooling distribution units 1 pump the first fluid, thereby circulation the first fluid in the inner fluid circuit 80.
[0110] In modifications (not shown), the data center cooling system 100 can include several (at least two) inner fluid circuits 80, each of the inner fluid circuits 80 being thermally coupled to the outer fluid circuit 70 by at least one corresponding cooling distribution unit 1 , respectively.
[0111] Turning back to Fig. 1 , the outer fluid circuit 70 includes a fluid supply branch 71 for supplying the second fluid to the cooling distribution units 1 and a fluid return branch 72 for discharging the second fluid from the cooling distribution units 1 .
[0112] The inner fluid circuit 80 includes a fluid supply branch 82 for supplying the first fluid from the cooling distribution units 1 to the parts 81 and a fluid return branch 83 for returning the first fluid from the parts 81 to the cooling distribution units 1 . The inner fluid circuit 80 can include valves 84 for controlling fluid supply to the individual parts 81 .
[0113] In the following, the individual cooling distribution unit 1 is described in more detail.
[0114] The cooling distribution unit 1 comprises an outer fluid section 10 that is fluidly coupled with the outer fluid circuit 70, in more detail with the fluid supply branch 71 and the fluid discharge branch 72. Further, the cooling distribution unit 1 comprises an inner fluid section 30 that is fluidly coupled with the inner fluid circuit 80, in more detail with the fluid supply branch 82 and the fluid return branch 83.
[0115] December 2025 D 200 P 2657 WO
[0116] A heat exchanger 20 of the cooling distribution unit 1 provides thermal coupling between the outer fluid section 10 and the outer fluid section 30 and hence between the outer fluid circuit 70 and the inner fluid circuit 80. The heat exchanger 20 includes a first flow branch 22 (also referred to as inner flow branch 22) that forms part of the inner fluid section 30 and is hence fluidly coupled with the inner fluid circuit 80. A second flow branch 21 of the heat exchanger 20 (also referred to as outward flow branch 21 ) forms part of the outer fluid section 10 and is hence fluidly coupled with the outer fluid circuit 70. Accordingly, it may be considered that the heat exchanger 20 forms part of both the outer fluid section 10 and the inner fluid section 30.
[0117] The heat exchanger 20 prevents mixing of the first fluid and the second fluid. The cooling distribution unit 1 (especially the heat exchanger 20) provides thermal coupling between the outer fluid circuit 70 and the inner fluid circuit 80 without fluid coupling between the outer fluid circuit 70 and the inner fluid circuit 80.
[0118] The outer fluid section 10 may include at least one valve 11 and one or several sensors, e.g. temperature sensors 12, 15 and / or pressure sensors 13, 14.
[0119] Further, each cooling distribution unit 1 has a pump 31 for pumping the (first) fluid flowing through the inner fluid section 30. The pump 31 can comprise a pump driver 32a and a pump element 32b with a pump motor. Each pump 31 contributes to circulating the first fluid in the inner fluid circuit 80.
[0120] The cooling distribution unit 1 comprises a measurement system 40 for determining a flow rate FLR (see Fig. 3) of a fluid flow FLF in a flow path FPH. In this case, the inner fluid section 30 forms the flow path FPH.
[0121] The measurement system 40 is described referring to Fig. 2 in more general.
[0122] December 2025 D 200 P 2657 WO
[0123] The measurement system 40 includes a reference section 41 in the flow path FPH and measurement means for determining a pressure drop PRD (see x-axis / ab- scissa in Fig. 3) over the reference section 41 along the flow path FPH (and hence along the fluid flow FLF).
[0124] The pressure drop PRD is the difference between a first pressure PR1 at a first location in the flow path FPH and a second pressure PR2 at a second location in the flow path FPH (PRD = PR2 - PR1 ). The reference section 41 is arranged in the flow path FPH between the first location and the second location. For example, in Fig. 2, the first location is upstream of the reference section 41 and the second location is downstream of the reference section 41 along an intended flow direction of the fluid flow FLF in operation.
[0125] The measurement means (the entirety thereof) generate measurement signals MTS that are indicative of the pressure drop PRD. In the exemplary embodiment, the measurement means include a first pressure measurement means 42 (e.g. including a pressure sensor, a pressure transmitter, and / or a pressure transducer) measuring the first pressure PR1 at the first location and a second pressure measurement means 43 (e.g. including a pressure sensor, a pressure transmitter, and / or a pressure transducer) measuring the second pressure PR2 at the second location. Hence, the measurement signals MTS provided by the combination of the first pressure measurements means 42 and the second pressure measurement means 43 are indicative of the pressure drop PRD = PR2 - PR1. Additionally or alternatively, the measurement means could include a differential pressure sensor (not shown).
[0126] In addition, the measurement system can include at least one temperature sensor for measuring a temperature of (the fluid in) the fluid flow FLF. Fig. 2 shows a first temperature sensor 44 that measures a first temperature T1 on a first temperature
[0127] December 2025 D 200 P 2657 WO location along the fluid path FPH and a second temperature sensor 45 that measures a second temperature T2 on a second temperature location along the fluid path FPH, wherein the reference section 41 is arranged in the flow path FPH between the first temperature location and the second temperature location. For example, in Fig. 2, the first temperature location is upstream of the reference section 41 and the second temperature location is downstream of the reference section along the intended flow direction of the fluid flow FLF in operation.
[0128] In Fig. 1 , in each of the measurement systems 40, and additional optional third temperature sensor 46 that measures a third temperature along the fluid path FPH is shown. Since the third temperature location and the second temperature locations are directly subsequent in this example, it can be assumed that the third temperature is the same as the second temperature. The third temperature sensor 46 can be provided as a redundancy for the second temperature sensor 45 and / or for increasing the measurement of the second temperature.
[0129] Apart from this, the inner fluid section 30 can include a pressure sensor 33 downstream of the pump 31 and / or a differential pressure sensor measuring a pressure increase caused by the pump 31 .
[0130] For example, the measurement signals MTS and / or the signals from the temperature sensor(s) 44, 45, 46 may be obtained with a sample rate, e.g. by an evaluation module 50 described below. The time intervals might be in the range from 1 s to 30 s, e.g. 5 s.
[0131] The measurement signals MTS and / or the signals from the temperature sensor(s) of several sampling instances might be stored (e.g. in the memory 57) and / or averaged as basis for further determinations / calculations, e.g. over at least a certain number of values and / or over at last a predetermined period of time.
[0132] December 2025 D 200 P 2657 WO
[0133] For example, at least six subsequent sampled values of the measurement signals MTS indicating the first pressure PR1 and / or sampled values of the measurement signals MTS indicating the first pressure PR1 over at least at least 30 s might be stored and averaged. Corresponding approaches can apply regarding the measurement signals MTS indicating the second pressure PR2 and / or regarding the signals from the temperature sensor(s).
[0134] Turning back to Fig. 2, the reference section 41 provides a smallest effective flow cross-section along the flow path FPH, at least between the first location and the second location (which are the relevant locations for determining the pressure drop PRD). The pressure drop PRD between the first location and the second location is dominated by the influence of the reference section 41. For example, for a given first pressure PR1 and given operational conditions, the reference section 41 may cause at least 95 %, maybe at least 99 % of the pressure drop PRD.
[0135] The operational conditions may include one of, several of, or all of the following:
[0136] - a fluid composition of the fluid flow FLF;
[0137] - a viscosity of (the fluid in) the fluid flow FLF (e.g. a viscosity of the fluid composition);
[0138] - at least one temperature of (the fluid in) the fluid flow, e.g. the first temperature T1 and / or the second temperature T2;
[0139] - a temperature difference of (the fluid in) the fluid flow FLF over the reference section 41 , e.g. temperature drop TRD = T2 - T1 (the temperature difference TRD is not shown in the figures).
[0140] At least one correlation CRR between the flow rate FLR through the reference section 41 and the pressure drop PRD of the fluid flow FLF over the reference section 41 is known, for example for pre-determined operational conditions.
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[0142] An example for the at least one correlation CRR for the reference section 41 is shown in Fig. 3. The shown correlation CRR is applicable for the inward fluid branches 21 of the heat exchangers 20.
[0143] The at least one correlation CRR can be investigated in advance, for example by performing measurements and / or simulations. This can be done by the manufacturer or on behalf of the manufacturer. In general, a test specimen that is of the same type than the actual reference section 41 can be used for performing the measurement or at least a part of the measurements. It is also possible that the actual reference section 41 is used for performing the measurement or at least a part of the measurements for investigating the correlation CRR.
[0144] In general, it is not necessary (but possible) that the at least one correlation CRR is investigated individually for each reference section 41 of the same type. The at least one correlation CRR might be investigated by performing measurements on the test specimen and / or by performing simulations with a simulation model representing the reference section 41 .
[0145] Nevertheless, at least some of the individual reference sections 41 might be subjected to a control measurement regarding the at least correlation CRR. For example, the manufacturer subject only some of the reference sections 41 to control measurements in order to check conformity of those reference sections 41 with the pre-investigated correlation CRR, e.g. randomly picked for quality control purposes. Alternatively or in addition, the control measurements may be limited to checking the conformity of the reference section 41 with the correlation CRR only partly, e.g. for only one pre-determined pressure drop or only a few pre-determined pressure-drop(s).
[0146] December 2025 D 200 P 2657 WO
[0147] Correlation information CRI related to the at least one correlation CRR is provided. The correlation information CRI can be generated, e.g. by the manufacturer, based on the results of the investigation of the correlation(s) CRR.
[0148] The correlation information CRI describes, for example mathematically models, the at least one correlation CRR such that the flow rate FLR can be calculated based on the pressure drop PRD (based on the measurement signals MTS) and the correlation information CRI in operation.
[0149] The measurement system 40 determines the flow rate FLF without a flow meter. Accordingly, in the embodiments shown in Figs. 1 and 2, the measurement system 40 is free of any flow meter.
[0150] In more detail, the measurement system 40 can include the evaluation module 50. An embodiment of the evaluation module 50 is shown in more detail in Fig. 2. The description also is an example how a method for determining the flow rate FLF without using a flow meter can be implemented.
[0151] The evaluation module 50 comprises a measurement interface 51. The measurement interface 51 includes at least an interface I input for receiving the measurement signals MTS from the measurement means. For example, the measurement interface 51 can include a first pressure sensor interface 52 for receiving the measurement signals from the first pressure sensor 42 and a second pressure sensor interface 53 for receiving the measurement signals from the second pressure sensor 43.
[0152] Additionally, the measurement interface 51 can include at least one temperature interface for receiving signals from a temperature sensor, e.g. a temperature sensor interface 54 for receiving signals from the first temperature sensor 44 (indicating the first temperature T1 ) and / or a temperature sensor interface 55 for
[0153] December 2025 D 200 P 2657 WO receiving signals from the second temperature sensor 45 (indicating the second temperature T2).
[0154] Further, the evaluation module 50 has at least one (micro-)processor 56. The at least one microprocessor 56 is functionally coupled to the measurement interface 51 .
[0155] The evaluation module 50 can further include a memory 57, in which the correlation information CRI is stored. This allows local access to the correlation information CRI. Especially, the correlation information CRI might be pre-stored in the memory 57, e.g. by the manufacturer. The memory 57 can be connected to the microprocessor 56.
[0156] Additionally or alternatively, the evaluation module 50 has a communication interface 58. The communication interface 58 can be connected to the microprocessor 56. The communication interface 58 may be configured for data exchange with external electronic devices. It may be configured for wired and / or wireless communications. For example, it might include a bus interface (such as a fieldbus interface and / or a CAN bus interface), a local area network interface, a Bluetooth® interface, and / or the like. The communication interface 58 may include at least one connector terminal 59, 60, e.g. at least one RJ-45 connector and / or another connector terminal.
[0157] In particular, the evaluation module 50 can be configured to receive (at least parts of) the correlation information CRI and / or updates of the correlation information CRI from an external source, e.g. from a data server (not shown). Optionally, the data server can form part of the measurement system 40.
[0158] Accordingly, the method can include providing correlation information CRI in the memory 57 of the evaluation module 50 and / or via at least one data server.
[0159] December 2025 D 200 P 2657 WO
[0160] Optionally, the correlation information CRI covers correlations CRR for different (operational) conditions, for example for different fluid compositions, temperatures, and / or viscosities of (the fluid in) the fluid flow. This means that the correlation information CRI includes information related to different correlations CRR for several (at least two) different operational conditions and / or information related to an impact of variations of the operational conditions on the at least one correlation CRR.
[0161] Accordingly, the different correlations CRR and / or the impact of variations of the operational conditions on the at least one correlation CRR can be investigated. The above disclosure regarding investigation of the at least one correlation CRR may apply accordingly.
[0162] According to one aspect, the correlation information CRI can include a function for calculating the flow rate FLR based on the pressure drop PRD. For example, the function can correspond to the following formula:
[0163] (F1 ) FLR (PRD) = ((B / (2*A))2- (C - PRD) / A)A(1 / 2) - B / (2*A)
[0164] A, B, and C are parameters.
[0165] The flow rate FLR can be a mass flow rate. For example, the pressure drop PRD may be indicated in kPa and the flow rate FLR may be is indicated in kg / s. Additionally or alternatively, a volume flow rate can be determined.
[0166] Just as an example, parameter A can be in the range from 0,4 kPa*s2 / kg2to 0,7 kPa*s2 / kg2, parameter B can be in the range from 0,05 kPa*s / kg to 0,3 kPa*s / kg, and / or parameter C can be in the range from -0,1 kPa to -0,02 kPa. Naturally, the parameters vary for different types of reference sections 41 . They
[0167] December 2025 D 200 P 2657 WO can be investigated for different types of reference section 41 and / or for different operational conditions.
[0168] One possible equivalent to the function above is:
[0169] (F2) FLR (PRD) = (D2- (E - PRD) / F)A(1 / 2) - D
[0170] D, E, and F are parameters in this case.
[0171] The correlation information CRI might include information for adapting one of, several of, or all of the parameters to different operational conditions. For example, it may include a function and / or a look-up table for adapting at least one of the parameters for variations of at least one of the operational conditions. Optionally, the correlation information CRI can include functions and / or look-up tables to adapt several of the parameters (maybe all of the parameters) for of at least one of the operational conditions, several of the operational conditions, or all operational conditions.
[0172] As noted above, the evaluation module 50 determines the flow rate FLR of the fluid flow FLF based on the measurement signals MTS (e.g. based on the pressure drop calculated from the measurement signals MTS) and the correlation information CRI.
[0173] Further, the evaluation module 50 can be configured to determine the temperature drop TRD of (the fluid in) the fluid flow FLF over the reference section 41. With regard to Fig. 2, the temperature drop TRD can be calculated as TRD = T2 - T1.
[0174] The evaluation module 50 may be configured to estimate a heat transport capacity (referred to as HTPC, not shown on the figures) of the fluid flow FLF. The heat transport capacity HTPC may be estimated by multiplying the determined flow
[0175] December 2025 D 200 P 2657 WO rate FLR with a specific heat capacity (referred to as SHC, not shown in the figures) of the fluid composition in the fluid flow FLF:
[0176] (F3) HTPC = FLF * SHC
[0177] According to one aspect, the evaluation module 50 may be configured to estimate a heat transfer capacity (referred to as HTFC, not shown in the figures) of the fluid flow FLF. The heat transfer capacity HTFC may be estimated by multiplying the determined flow rate FLR with the specific heat capacity SHC of the fluid composition in the fluid flow FLF and with the temperature difference TRD:
[0178] (F3) HTFC = FLF * SHC * TRD = HTPC * TRD
[0179] Information on the specific heat capacity SHC may be stored in the memory 57, e.g. pre-stored by the manufacturer, and / or received from the external source (or another external source) via the communication interface 58. The information on the super heat capacity SHC may form part of the correlation information CRI.
[0180] Just as an example, the specific heat capacity SHC for the fluid composition consisting of 75 % water and 25 % propylene glycol at a temperature of 30 °C may be 3,97 kJ / (kg*K).
[0181] According to one aspect, the information on the specific heat capacity SHC may include information on variations on the specific heat capacity SHC for different operational conditions. For example, the information on the specific heat capacity SHC may include information on variations on the specific heat capacity SHC for different temperatures of the fluid composition, for example a function SHC(T) and / or a look-up table with different values of the specific heat capacity SHC for different temperatures of the fluid composition.
[0182] December 2025 D 200 P 2657 WO
[0183] As an example, the evaluation module may calculate the heat transfer capacity HTFC as:
[0184] (F4) HTFC(PRD, T1 , T2) = FLF * J SHC(T) dT with integration limits from T1 to T2.
[0185] Other, but maybe less accurate approaches are as follows:
[0186] (F5) HTFC(PRD, T1 , T2) = FLF * TRD * (SHC(T2) + SHC(T1 )) / 2
[0187] The information on the specific heat SHC may cover at least a predetermined fluid composition. Of course, it can also cover several fluid compositions.
[0188] The evaluation module 50 may be configured to use the most suitable information on the specific heat capacity SHC depending on the temperature(s) and / or the selected fluid composition of the fluid flow FLF.
[0189] Optionally, the evaluation module 50 can include a user interface 61. The user interface 61 may comprise a screen, e.g. a touchscreen, buttons, and / or soundgenerating means. The user interface 61 may be detachable. In the latter case, it can be sufficient that the evaluation module 50 comprises a mount for detachably mounting the user interface 61 . The user interface 61 can be adapted for receiving user input and / or to present information to the user, e.g. including graphic output (for example via the screen / touchscreen) and / or audio output. The user input can, for example, include information on the fluid composition of the fluid flow FLF.
[0190] In particular, the evaluation module 50 can be configured to receive user input for selecting the fluid composition of the fluid flow FLF (e.g. via the user input 61 and / or via the communication interface 58) and to determine the flow rate FLR
[0191] December 2025 D 200 P 2657 WO based on the determined pressure drop PRD and the correction information CRI, wherein specific information based on the selection of the fluid composition is used.
[0192] The evaluation module 50 can be configured to display, with the (touch-)screen of the user interface 61 , at least one of, several of, or all of the following: The pressure P1 , the pressure P2, the pressure drop PRD, the first temperature T1 , the second temperature T2, the temperature drop TRD, the flow rate FLR, the heat transport capacity HTPC, and the heat transfer capacity HTFC.
[0193] Additionally or alternatively, the evaluation module 50 can be configured to transmit, vie the communication interface 58, one of, several of, or all of the following: The pressure P1 , the pressure P2, the pressure drop PRD, the first temperature T1 , the second temperature T2, the temperature drop TRD, the flow rate FLR, the heat transport capacity HTPC, and the heat transfer capacity HTFC.
[0194] The heat transfer capacity HTFC can be displayed in kilowatts (kW). The displayed value may be rounded to a nearest full kilowatt value.
[0195] The heat transfer capacity HTFC may be recalculated and / or the display may be updated in regular intervals, e.g. every 30 s.
[0196] The evaluation module 50 may be configured to automatically prevent calculation and / or outputting (e.g. displaying and / or transmitting) of the heat transport capacity HTPC and / or the heat transfer capacity HTFC when the determined flow rate FLR is below a minimum flow rate threshold. The screen may show a corresponding message informing the user in this case (e.g. "Cooling cap. N.A: flow capacity too low").
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[0198] Additionally or alternatively, the evaluation module 50 can be configured to automatically prevent calculation and / or outputting (e.g. displaying and / or transmitting) of the heat transport capacity HTPC and / or the heat transfer capacity HTFC when the pressure drop PRD is below a minimum pressure drop threshold. The screen may show a corresponding message informing the user in this case (e.g. "Cooling cap. N.A - very low flow"). Just as an example, the minimum pressure drop threshold may be in the range from 10 kPa to 30 kPa.
[0199] The evaluation module 50 may be configured to indicate a warning with the user interface 58 (e.g. via displaying a warning message on the screen) and / or to transmit a warning message with the communication interface 58 if the measurement signals MTS and / or the temperature(s) are not available (e.g. "Cooling cap. N.A. - sensor error").
[0200] In the cooling distribution unit 1 as shown in Fig. 1 , the measurement system 40 determines the flow rate FLR of the fluid flow FLF in the inner fluid section 30 of the cooling distribution unit 1. In this embodiment, the inward flow branch 21 of the heat exchanger 20 constitutes the reference section 41 .
[0201] The evaluation module 50 may be configured further functionalities, e.g. for controlling the pump 31 (e.g. a pump speed and / or a pump power thereof). At least one of, several of, or all of the following may be considered by the evaluation module 50 for controlling the pump 31 : The pressure P1 , the pressure P2, the pressure drop PRD, the first temperature T 1 , the second temperature T2, the temperature drop TRD, the flow rate FLR, the heat transport capacity HTPC, the heat transfer capacity HTFC, a pressure measured by the pressure sensor 33, and the pressure increase causes by the pump 31 .
[0202] In general, the reference section 41 can include any arbitrary inner and outer structure, at least as long as the at least one correlation CRR between the flow
[0203] December 2025 D 200 P 2657 WO rate FLR through the reference section 41 and the pressure drop PRD of the fluid flow FLF over the reference section 41 is investigated and as long as the correlation information CRI is sufficient to determine the flow rate FTR based on the determined pressure drop PRD and the correlation information CRI with a desired precision.
[0204] In the examples above, no fluid is added to the fluid flow FLF or removed from the fluid flow FLF along the flow path FPH between the first location (the location of the first pressure P1 ) and the second location (the location of the second pres- sure P2). However, in modifications, the at least one correlation CRR and accordingly the correction information CRI can also include information for considering predictable addition of fluid to the fluid flow FLF and / or predictable removal of fluid from the fluid flow FLF between the first location and the second location. For example, the at least one correlation CRR and accordingly the correction infor- mation CRI can reflect the influence of a pressure relief valve (not shown) in the reference section 40.
[0205] December 2025 D 200 P 2657 WO
[0206] List of reference signs:
[0207] I cooling distribution unit
[0208] 10 outer fluid section
[0209] I I valve
[0210] 12, 15, 33 pressure sensor
[0211] 13, 14 temperature sensor
[0212] 20 heat exchanger
[0213] 21 second fluid branch (outward fluid branch)
[0214] 22 first fluid branch (inward fluid branch)
[0215] 30 inner fluid section
[0216] 31 pump
[0217] 32a pump driver
[0218] 32b pump element
[0219] 33 pressure sensor
[0220] 40 measurement system
[0221] 41 reference section
[0222] 42 first pressure measurement means
[0223] 43 second pressure measurement means
[0224] 44 first temperature sensor
[0225] 45 second temperature sensor
[0226] 46 third temperature sensor
[0227] 50 evaluation unit
[0228] 51 measurement interface
[0229] 52 first pressure sensor interface
[0230] 53 second pressure sensor interface
[0231] 54 first temperature sensor interface
[0232] 55 second temperature sensor interface
[0233] 56 (micro-)processor
[0234] 57 memory
[0235] 58 communication interface
[0236] December 2025 D 200 P 2657 WO
[0237] 59, 60 connector terminal
[0238] 61 user interface
[0239] 70 outer fluid circuit
[0240] 71 fluid supply branch
[0241] 72 fluid discharge branch
[0242] 80 inner fluid circuit
[0243] 81 parts
[0244] 82 fluid supply branch
[0245] 83 fluid return branch
[0246] 84 valve
[0247] 100 data center cooling system
[0248] CRR correlation
[0249] CRI correlation information
[0250] FLF fluid flow
[0251] FLR flow rate
[0252] FPH flow path
[0253] MTS measurement signals
[0254] PR1 first pressure
[0255] PR2 second pressure
[0256] PRD pressure difference
[0257] T1 first temperature
[0258] T2 second temperature
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Claims
Claims:
1. A method for determining a flow rate (FLR) of a fluid flow (FLF) through a flow path (FPH), the method comprising:- guiding the fluid flow (FLF) through a reference section (41 ) in the flow path (FPH);- determining a pressure drop (PRD) of the fluid flow (FLF) over the reference section (41 );- determining the flow rate (FLR) of the fluid flow (FLF) based on the determined pressure drop (PRD) and correlation information (CRI) for the reference section (41 ), wherein the correlation information (CRI) relates to at least one correlation (CRR) between the flow rate (FLR) through the reference section (41 ) and the pressure drop (PRD) of the fluid flow (FLF) over the reference section (41 ), wherein the correlation information (CRI) covers correlations (CRR) for different fluid compositions, temperatures (T1 , T2), and / or viscosities of the fluid flow (FLF).
2. The method according to claim 1 , wherein the reference section (41 ) at least substantially consists of a flow branch (22) of a heat exchanger (20).
3. The method according to any one of the preceding claims, wherein the flow path (FPH) forms part of a cooling distribution unit (1 ) for a data center cooling system (100).
4. The method according to any one of the preceding claims, wherein the method further comprises pumping the fluid flow (FLF) by means of at least one pump (31 ), wherein the at least one pump (31 ) is provided in the flow path (FPH) upstream or downstream of the reference section (41 ).December 2025 D 200 P 2657 WO5. The method according to any one of the preceding claims, further including estimating a heat transport capacity of the fluid flow (FLF) based on the flow rate (FLR) of the fluid flow (FLF) and a specific heat capacity of a fluid composition of the fluid flow (FLF).
6. The method according to any one of the preceding claim, wherein the method includes determining a temperature drop of the fluid flow (FLF) over the reference section (41 ) and estimating a heat transfer capacity of the fluid flow (FLF) based on the flow rate (FLR) of the fluid flow (FLF), the specific heat capacity, and the temperature drop.
7. The method according to any one of the preceding claims, wherein the correlation information (CRI) includes a non-linear function relating the flow rate (FLR) to the pressure drop (PRD).
8. The method according to claim 7, wherein the non-linear function includes at least two different parameters.
9. The method according to claim 7 or 8, wherein the non-linear function includes a term ((B / (2*A))2-(C-PRD) / A)A(1 / 2)-B / (2*A) relating the flow rate (FLR) with the pressure drop (PRD), wherein A, B, and C are parameters, or a mathematical equivalent to this term.
10. The method according to any one of the claims 8 or 9 and according to claim 10, wherein the function is adapted to the different fluid compositions, temperatures (T 1 , T2) and / or viscosities of the fluid flow (FLF) by modified parameters of the function.
11. Evaluation module (50) for determining a flow rate (FLR) of a fluid flow (FLF) through a flow path (FPH), wherein the flow path (FPH) is equippedDecember 2025 D 200 P 2657 WOwith a reference section (41 ) arranged in the flow path (FPH) for guiding the fluid flow (FLF) therethrough and measurement means (42, 43) for providing measurement signals (MTS) that are indicative of a pressure drop (PRD) of the fluid flow (FLF) over the reference section (41 ), wherein the evaluation module (50) includes a measurement interface (51 ) for receiving the measurement signals (MTS) and a processor (56), wherein the evaluation module (50) is configured to retrieve correlation information (CRI) for the reference section (41 ), wherein the correlation information (CRI) relates to at least one correlation (CRR) between the flow rate (FLR) through the reference section (41 ) and the pressure drop (PRD) of the fluid flow (FLF) over the reference section (41 ), and wherein the evaluation module (50) is configured to determine the flow rate (FLR) of the fluid flow (FLF) based on the measurement signals (MTS) and the correlation information (CRI), wherein the evaluation module (50) include a memory (57) storing the correlation information (CRI), and wherein the correlation information (CRI) covers correlations (CRR) for different fluid compositions, temperatures (T1 , T2), and / or viscosities of the fluid flow (FLF).
12. The evaluation module (50) according to claim 11 , wherein the evaluation module (50) includes a communication interface (58) and is configured to retrieve the correlation information (CRI) from an external source.December 2025 D 200 P 2657 WO13. A measurement system (40) for determining a flow rate (FLR) of a fluid flow (FLF) through a flow path (FPH), wherein the measurement system (40) includes a reference section (41 ) arranged in the flow path (FPH) for guiding the fluid flow (FLF) therethrough, measurement means (42, 43) for providing measurement signals (MTS) that are indicative of a pressure drop (PRD) of the fluid flow (FLF) over the reference section (41 ), and the evaluation module (50) according to any one of the claims 11 or 12.
14. Cooling distribution unit (1 ) for a data center cooling system (100), the data center cooling system (100) comprising an inner fluid circuit (81 ) for providing cooling to parts (81 ) of an IT infrastructure in a data center, and an outer fluid circuit (70) for dissipating heat; wherein the cooling distribution unit (1 ) comprises an outer fluid section (10) for fluid coupling with the outer fluid circuit (70); an inner fluid section (30) for fluid coupling with the inner fluid circuit (80), wherein the inner fluid section (30) comprises a pump (31 ); and a heat exchanger (20) for heat coupling between the outer fluid section (10) and the inner fluid section (30); wherein the cooling distribution unit (1 ) comprises the measurement system (40) according to claim 13 for the inner fluid section (30), wherein the measurement system (40) includes an inward flow branch (22) of the heat exchanger (20) forming part of the inner fluid section (30) as the reference section (41 ).December 2025 D 200 P 2657 WO