Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
  • G01F1/34—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K17/00—Measuring quantity of heat
  • G01K17/06—Measuring quantity of heat conveyed by flowing media, e.g. in heating systems e.g. the quantity of heat in a transporting medium, delivered to or consumed in an expenditure device

Definitions

• the invention is related to consumption measu ing, viz. establishing the amount of a fluid or fluidborne heat energy that has been consumed in the course of a technological process or supplied by public ser vices such as waterworks or district heating plants.
• a new method has been conceived which is preferably per formed by using a new meter offering the advantage that
• the data obtained by an indirect measurement of the wanted quantities may immediately be displayed in the wanted dimensions, the said data may also be collected and stored and/or further processed at the very spot and/or transmitted to external processing and/or process control means.
• billing/ - establishing the amount of fluid consumption or heat consumption individually for each consumer /be it an industrial plant, a public building, the individual dweller of a lodgement or a certain community of dweller/; - preparing the bill in consideration of the consumption within a certain period /hereinafter shortly referred to as billing/;
• Another very important task is the control of the fluid flow in order to achieve optimum working conditions and avoid as far as possible any superfluous consumption such as overflov; or heat loss without thereby affecting the undisturbed supply of the wanted quantities.
• Such a process control is usually performed by applying control signals which represent either the quantity already consumed or the deviation of the transported volume from the optimum, respectively.
• Such control is of a continually increasing importance especially since the economizing of energy is recently more and more laid stress upon. It can be seen that the amount of consumption is the basis for both the billing of supply and the optimizing of consumption. It would therefor be reasonable and this is the object of our invention to obtain all information necessary for both billing and controlling from a single signal proportional to a single physical quantity.
• the heat energy consumption in a district heating plant in a manner that the consumption of any individual consumer or even any of his heat exchangers may be specified individually and also the su ⁇ merized consumption of a greater unit may be established, and on the other hand the water consumption in any of the lodgements which shall, if necessary, individually be specified even for each water-tap and also summarized in any wanted relation.
• the measuring of the consumed heat energy may according to pri'or art be performed in different ways.
• Another method consists in measuring only the temperature difference and multiplying same by a constant value representing all other quantities to be taken into consideration.
• a device has been developed based on the principle of evaporation but there arises an important heat loss and the device is also delicate for both the manufacturing and application aspects so that its widespread use can hardly 6e reckoned with.
• the different heat consumption measuring devices belonging to prior art and used in the industrial practice are aside from their particular shortcomings showing some common disadvantages: - the device may only be contacted with the fluid flow by disrupting the pipe system at a given spot; this is especially disadvantageous if a working plant shall afterwards be equipped for s more particular consumption measuring and/or controlling but the insertion of any of the known means into a fluid transport path is usually disadvantageous even in case of plants yet to be built;
• the known devices apt for this purpose are usually relatively extensive and intricate.
• the application of the known devices is also often restricted by the dimensions of the connecting path, e.g. the diameter of the pipe etc.
• ⁇ Q/ ⁇ t the heat supply reckoned for a time unit
• C P the specific heat of the heat carrying fluid
• ⁇ m/ ⁇ t tte quantity of fluid flowing through a certa cross-section during a time unit.
• the temperature measuring may be performed by any known method.
• the known devices used for measuring the fluid flow may work on a mechanical principle, they may be based on electro-mechanical conversion, and contractless devices may also be used; there are among others devices converting the rotation of a propeller into an electric signal, capacitive sensors, sensors based on the eddy current phenomenon or utilizing the magnetic momentum, etc.
• the known methods are either providing rather inaccurate data or requiring the performance of more measurements of different kind the greater part of the devices used for measuring the mass flow are inserted into the transport path in a disturbing manner whereas the use of the known contact less sensors is unbearable for economic reasons.
• the invention is based on the conception tha the different data necessary for performing the above specified tasks such as billing, process control, keeping evidence and the like can be provided in a relatively simple and inexpensive manner by measuring a single physical quantity which
• Such a physical quantity is the difference between the pressure valmes sensed in two characteristic cross-sections of tbe pipe system during the mass flow. This quantity is properly speaking the dynamic differential pressure since all static components bein equal in both cross-sections are eliminated when producing a signal representing the difference between the said pressure values.
• the sensors used in the methods according to prior art are usually contacted with the flowing fluid medium in a manner disturbing a working conditions whereas the differential pressure may be measured by just tapping the pipe wall over a very small boring not interfering with the fluid flow in any way the leakage being of an incommensurabily small value.
• the sensors of some of the known diffe rential pressure gauges may, e.g. be adjusted to the pipe wall by the well known injecting method used for fixing rivets, pins and the like into the wall.
• the relation between the supplied heat energy, the mass flow, and the differential pressure will hereinbelor/ bet set forth particularly. It can be seen that the measuring of neither the temperature nor the mass flow will be needed any longer once the data representing the differential pressure will be at our disposal.
• the value of the differential pressure ⁇ P din is directly representing also the heat loss but the other physical quantities components of the resulting formula for heat loss can also be derived therefrom considering that there is also an unambiguous relation between the mass flow and the differential pressure. It goes without aaying that the amount of water supply, viz.
• the amount of water flowing through a certain cross-section of a pipe can also be derived from the differential pressure by use of known and cheap data processing means; the single physical quantity obtained by a slight, undisturbing interference with the pipe wall for performing the indirect measurement provides all information necessary to establish the heat supply and/or the fluid supply of a system and even other important features of the system such as the ratio of static and dynamic pressure and their changes during work and the like which may be useful for process control and/or other purposes. If, e.g. a pipe section ending in a water-tap is in two different cross-sections lying near to each other subjected to the said pressure sensing, the water supply of either a cold water-tap or a hot water-tap can immediately be established.
• consumption meters performin same can manifold be designed adjusting them to different systems and for different purposes. They may be arranged even at each heat exchanger and each water-tap of a dwelling at very small expenses and space requi rement, and the output signals of the said meters may preferably over a wire connection be transmitted to a common data processing device of similarly small space requirement and simple construction the said data processing device being in a known manner embodied for any wanted purpose, viz. to be able to derive any wante other quantity from the single input signal representing the said differential pressure.
• Figure 1 is illustrating the consumption measurement as used in a district heating system by meters arranged in a dwelling
• Figure 2 is showing the water consumption measurement performed by sensing the differential pressure in a pipe section ending in a water-tap
• a pressure transmitter 12, 12i is arranged at each heat exchanger Hi and also at the central unit 11 providing output signals proportional to the pressure difference between the fluid input and output of the given heat exchanger.
• the data measured with the radiators are transmitted through the wire 142 to the data processing unit 132 whereas the data measured with the central unit 11 are transmitted through the wire 141 to the data processing unit 131.
• the pressure transmitter 22 is over its sensors coupled to the pipe section 21 ending in a water-tap at two different cross- -sections 211 and 212 /spaced of each other at a distance L/, and the transmitter 22 is connected to the data processing unit 23; the latter one is storing and displaying the measured data but also utilizing them for the supply control system deriving from the said signals the values of the controlled variable and generating the control signal for an actuator 24 such as a valve in accordance with the error value.
• Figure 3 illustrates the data processing.
• the said data processing units 131, 132, 23 are comprising an arithmetical stage 32 each to the input/s/ of which is coupled at least one pressure transmitter 311 in direct or indirect connection whereas one or more DC-signal sources 312, 313, 314 are coupled to further inputs of the arithmetical stage 32 the said DC-signals representing constant value system features such as the diameter of the pipe, the specific heat of the carrier if different from 1, or the constant values to be taken into consideration if converting the measured quantity into any other kind of related quantities.
• an A/D converter such as voltage /pulse train converter 33 is coupled to the output of the arithmetical stage 32 followed by a pulse counter 34.
• a display means showing the instant value of the stored sum may be integrated into the pulse counter 34 but it may also be expedient to use a special data recording device, e.g. a data printer or a numerical data recorder 35 coupled with a numerical display device 36.
• a separate output of the arithmetical stage 32 or the A/D converter may be coupled to a further device such as an instant value display 37 showing the instan value of heat or water supply /flow intensity/ or the separate output may be coupled to an external data processing system or the process control system re ferred to when explaining Figure 2, e.g. to its actuator 24.
• the arithmetical stage 32 can be provided with different outputs one of them being coupled to the input of the A/D converter.
• the data processing unit 131, 132, 23 may also be a multi-purpose device or the units 131, 132, 23 may be integrated into a common one so that the hot water consumption of a dwelling may be obtained over one of the outputs, another output may signalize the cold water consumption, a further output the heat consumption, etc.
• Any transmission line of the measuring system may be built in a manner as to carry digital, binary signals, there may be multiwire parallel outputs for signals comprising more than one digit, etc. It is also possible to use a pressure transmitter with an immediate digital output in which case the arithmetical stage 32 is also a digital type device and no subsequent A/D conversion is needed.
• the heat energy consumption during a time unit /which can subsequently be summed up over the whole working period/ shall be expressed by a formula comprising only a single independent variable, viz. the differential pressure ⁇ P din .
• ⁇ P ⁇ P st + ⁇ P sziv ⁇ P din
• ⁇ P st the static pressure difference from a given height h /pressure drop/
• ⁇ P sziv the pressure difference caused by the pump
• ⁇ P din is just the wanted variable, the dynamic differential pressure being proportional to the heat radiated by the heat exchangers.
• ⁇ P ⁇ P din if a pressure transmitter is used where the static components are not appearing in the output signal.
• the differential pressure transmitter is comprising a bridge circuit and the outputs of the strain gauges coupled with two different cross- -sections of the pipe are inserted into two different branches of the bridge, respectively, whereas the impedance of a third branch of the bridge circuit is an adjustable one such as a potenciometer, a zero compensation as starting calibration of the bridge will cause the elimination of the static components as far as the output signal of the bridge is concerned and such an elimination is justified by the reasonable presumption that the instant values of the eliminated static quantities will during work not change and not be affected by the dynamic changes occuring in the system such as a pressure deviation caused by a chang in density, or a change in the height of the fluid co lumn caused by a temperature difference.
• K' is a constant value system factor still including neither the cross-section of the pipe nOr the specific heat. Accordingly, the above transpositions allow furt a transposition of the equation /1.1/ - reducing it also by a 1 - as follows:
• the C factor may be reduced so that the system factor K' is also including the specific heat and is therefor indexed differently, be it: K o .
• the equation /1.1/ will now further be transposed:
• All components of the system factor K o are really constant values and may for any given system easily be defined by persons ordinarily skilled in the art.
• the diameter of the pipe may vary in different pla ces but it remains always unchanged at a given cross- -section of the pipe system and it is usually equal in the fluid input and output of one and the same heat exchanger so that in this case it can even be incorpora ted into the system factor K o . If the factor K o is cal culated with sufficient accuracy, the measured data may after the discussed processing give quite accurate values of the heat consumption.
• the ponderations set forth hereinabove allow a transposition of the formula /1.1.4/ for water carrier systems into It is therefor sufficient to multiply the value of the measured differential pressure ⁇ P din in the data processing stage by D 3 . ⁇ /6 to give the amount of the consumed heat energy. If the differential pressure is measured in a pipe supplying a dwelling, the diameter is also a constant value so that only a single DC-signal of constant value is needed; the data processing stage will need only a single DC-signal source and a very simple one since no adjusting of the level is needed. Such a heat consumption meter will only incur an extremely small space and expense requirement.
• the measuring is performed at a central unit supplying the fluid over pipes of different cross-section or a meter is wanted that may be adjusted to different heat exchengers or work ing conditions or a meter is wanted deriving different kinds of data from the measured quantity, a single DC -signal sources to provide different constant values for alternative or combined use in the data processing
• the arithmetical stage will always receive as many different DC-signals as necessry to perform the processing of data which shall be transformed according to different system features. It can be seen that the method according to the invention is a very flexible one.
• the method is apt to provide any data for billing and keeping evidence and also for generating signals for a process control intending the optimization of supply, consumption, and expenditure.
• the pipe section having a length L and lying between the first and the second cross-section coupled with the sensors of the pressure transmitter may be considered a pressure tube wherefrom the data to be processed may be obtained.
• the pressure transmitter may in this case comprise, e.g. a suitably shaped membrane following the dynamic changes of the pressure in a line manner and not subjected in the working range to any restricting conditions such as a threshold value. If taking into consideration the different members of the membrane equation, the modulus of flexibility and its effect on inclination, the dimensions of the membrane, and supposing that the movement of the membrane remains within the range of elasticity the well-known inclination formula may be transposed to comprise o nly a single independent variable, viz.
• the dynamic differential pressure whereas all other parameters may provided that suitable restrictions are complied with the converted into real constant value factors and incorporated into a resulting constant value system factor.
• the distance between the first and the second cross-section to be tapped by the sensors of the pressure gauge is expediently chosen as a function of the diameter of the pipe: L ⁇ 036 . D.
• One DC-signal source of the data processing unit will therefor supply a voltage proportional to the dimensionless system factor: 0,785 whereas another one will supply a voltage proportional to the diameter of the pipe. If, however, the differential pressure is measured in a pipe section ending in a water-tap of a dwelling, the value of the diameter is also an unchanging constant val so that a single DC-signal is needed for the data processing representing a combination of the dimensionless value 0,785 and the given pipe diameter.
• a suitable calibration of the data storing and display devices couple with the arithmetical stage is sufficient to obtain the water consumDtion in all stages in the usual dimension: m 3 .

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Fluid Mechanics (AREA)
• Measuring Volume Flow (AREA)

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Citations (4)

• 1982
  • 1982-11-04 WO PCT/HU1982/000057 patent/WO1983001685A1/en not_active Application Discontinuation
  • 1982-11-04 EP EP19820903179 patent/EP0093730A4/de not_active Withdrawn
• 1983
  • 1983-07-04 DK DK3080/83A patent/DK308083D0/da not_active Application Discontinuation

Patent Citations (4)

Non-Patent Citations (1)

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