WO2001001045A1

WO2001001045A1 - Method of adjusting mass flow in liquid circuit transferring energy

Info

Publication number: WO2001001045A1
Application number: PCT/FI2000/000565
Authority: WO
Inventors: Christer Ekman; Juhani Yli-Olli
Original assignee: ABB Flaekt Oy
Current assignee: Flaekt Woods Oy
Priority date: 1999-06-24
Filing date: 2000-06-22
Publication date: 2001-01-04
Anticipated expiration: 2001-12-24
Also published as: FI991444L; FI991444A7; AU5537700A; FI991444A0

Abstract

The invention relates to a method of adjusting mass flow in a liquid circuit transferring energy, the liquid circuit being part of an arrangement wherein one or more devices (1) emitting energy and/or one or more devices (2) receiving energy are connected to the liquid circuit (3) filled with liquid, through which liquid circuit energy is transmitted in a closed circuit, and the mass flow or energy content of a medium (4) emitting and/or a medium (5) receiving energy varies during the energy transfer process. In order to achieve optimal efficiency, the flow of the liquid circuit (3) is adjusted stepwise such that first, in a step of optimizing the energy process, the mass flow of the liquid circuit (3) is controlled according to a varying reference value or default value of the computational formula of the desired energy efficiency with respect to the current mass flow or energy flow of the medium (4) emitting and/or the medium (5) receiving energy, after which, in a second step, after predetermined conditions have been fulfilled, the flow in the liquid circuit (3) is adjusted on the basis of aT least one reference measurement (10) responding to the efficiency after a change has been intentionally effected in the flow such that the change in the variable describing the effect is compared with the previous step, and after it has been compared whether the new situation is better, the next step will continue similar, opposite or unchanged.

Description

METHOD OF ADJUSTING MASS FLOW IN LIQUID CIRCUIT TRANSFERRING

ENERGY

The invention relates to a method of adjusting mass flow in a liquid circuit transferring energy, the liquid circuit being part of an arrangement wherein one or more devices emitting energy and/or one or more devices receiving energy are connected to the liquid circuit filled with liquid, through which liquid circuit energy is transmitted in a closed circuit, and the mass flow or energy content of a medium emitting and/or a medium receiving energy varies during the energy transfer process. Energy consumption of today not only emphasizes energy recovery but also efficient utilization of energy. In practice this means that devices and systems should utilize the energy used as efficiently as possible within an extensive operation area in varying load situations. Generally thinking, in such systems energy is transferred from steps of recovering, receiving and produc- ing energy to a step of emitting energy through one or more liquid circuits by using a suitable liquid or solution as a medium. The steps of receiving, recovering and/or emitting energy thus comprise a process in which the medium with its pipes serves as one element for transferring energy from one step to another. This element is henceforth called a liquid circuit. The other element is a medium receiving or emitting energy, either flowing air or a gaseous mixture, or, alternatively, a liquid, which will henceforth be called a medium emitting or a medium receiving energy.

The received or emitted amount of energy compared with the amount of energy to be received or to be emitted describes the efficiency of the apparatus, in other words the efficiency of the process. A desirable characteristic is as high efficiency as possible, which means that as much as possible of the energy used can be utilized. In order for this condition to be fulfilled, the relationship between mass flows and the relationship between the mass flows and the size of the plant must be optimal. If the media emitting or receiving energy are constant in mass flow or energy amount, in order to achieve good efficiency it will usually suffice to adjust the liquid circuit once, and the relationship between the mass flows in the liquid circuit and between the media emitting or receiving energy remains optimal, which is required by the dimensioning of the devices. If the mass flows or amounts of energy of the media emitting or receiving energy change in the same proportion or differ in proportion to each other or if, alternatively, energy at as low a level as possible is to be utilized, the need for adjustment of the energy transfer process changes according to the situation. Potential restrictive functions, which, for example, protect the system against freezing, may make the situation more difficult. A common practice currently is that the flow in the liquid circuit is generated by one or more pumps having a constant speed of rotation. The protective measures and potential adjustment have been implemented by arranging a by-pass or limiting at the device either emitting or receiving energy to partly or completely reduce the effect of the device. Alternatively, it is possi- ble to affect the flow in the liquid circuit and thus also the amount of energy received or emitted by the liquid by using flow control, which may be an adjustable pump, valve or another device. If the mass flows or energy contents of the media emitting or receiving energy vary, the maximum efficiency has to be determined according to a situation or flow area, which is taken into account in the dimensioning of the devices. If the adjustment process is uncontrolled, the flow in the liquid circuit may end up in an area wherein heat transfer is substantially impaired when, for example, the flow changes into a laminar one in the energy transfer devices. Usually, this means great financial losses since the energy level required changes if the desired amounts of energy are to be transferred through the same apparatus. It is typical of a liquid circuit that the technical adjustment process is extremely slow and equipped with great delay owing to the effect of the medium, varying from case to case and depending on the distance between the devices emitting or receiving energy, mass flow of the control circuit, etc. Owing to the above-disclosed facts, it is difficult to find a functional adjustment variable to control the process such that the mass flow in the liquid circuit would be optimal under all circumstances.

An object of the invention is to provide a solution to enable drawbacks of the prior art to be eliminated. This is achieved by a method of the in- vention, which is characterized in that the flow of the liquid circuit is adjusted stepwise such that first, in a step of optimizing the energy process, the mass flow of the liquid circuit is controlled according to a varying reference value or default value of the computational formula of the desired energy efficiency with respect to the current mass flow or energy flow of the medium emitting and/or receiving energy, after which, in a second step, after predetermined conditions have been fulfilled, the flow in the iiquid circuit is adjusted on the basis of at least one reference measurement responding to the efficiency after a change has been intentionally effected in the flow such that the change in the variable describing the effect is compared with the previous step, and after it has been compared whether the new situation is better, the next step will continue simi- Iar, opposite or unchanged.

A main advantage of the invention is that the invention enables technical problems relating to adjustment of the liquid circuit to be removed in a cost-efficient and reliable manner and optimal efficiency to be achieved during a varying process. A further advantage of the invention is versatility be- cause the invention can be applied in connection with various energy transfer processes.

In the following, the invention will be described in closer detail by means of the application examples disclosed in the accompanying drawing, in which Figure 1 is a simplified, diagrammatic view of an energy transfer circuit utilizing a method of the invention,

Figure 2 is a simplified, diagrammatic view of a second energy transfer circuit utilizing the method of the invention, and

Figure 3 is a simplified, diagrammatic view of a third example of an energy transfer circuit utilizing the method of the invention.

Figure 1 is a schematic, diagrammatic view of a simple energy transfer circuit. The recovery circuit comprises one device 1 emitting energy and one device 2 receiving energy, a liquid circuit 3 being arranged therebetween. In Figure 1 , a medium 4 emitting energy is designated by reference number 4, and a medium receiving energy by reference number 5. The medium 4 emitting energy may be, for example, indoor air flowing outdoors, also called exhaust air, and the medium receiving energy may, correspondingly, be outdoor air flowing indoors, also called incoming air, etc.

In addition to the above-mentioned components and factors, Figure 1 shows a device adjusting the mass flow of the liquid circuit, a pump 6 or a valve 7, and further, a device designated by reference number 8 for carrying out a registration function of the mass flow or energy flow, an adjuster designated by reference number 9, and a device designated by reference number 10 for carrying out a reference measurement. The basic idea in a solution according to Figure 1 is that the device

2 receiving energy and the device 1 emitting energy are connected to the liq- uid circuit 3 filled with liquid, through which energy is transferred in a closed circuit from one device to another, and, taken more broadly, from the medium 4 emitting energy to the medium receiving energy. The mass flow or energy content of the medium emitting and/or receiving energy may also vary during the energy transfer process. The above-mentioned facts are conventional technology to one skilled in the art; therefore, the facts will not be explained herein in greater detail.

The basic idea of the method of the invention is generally that the solution aims to remove technical problems relating to adjustment of the liquid circuit in a cost-efficient and reliable manner and to achieve optimal efficiency during a varying process. The method of the invention is substantially based on a procedure wherein the steps of receiving and/or emitting energy are adjusted by using adjustment arrangements separately known per se stepwise, separately, sequentially or simultaneously, depending on the adjustment step required by the energy transfer process. The method of the invention relates to adjusting the flow in the liquid circuit 3 at the device 1 emitting energy or the device 2 receiving energy by affecting the other device through, for example, the speed of rotation of the pump 6 or the operation of the valve 7 in a manner agreeing with the energy needed, good energy efficiency and the rest of the functions of the system.

Viewing the invention in closer detail, it can be stated that it is essential for the method of the invention that the flow of the liquid circuit 3 is adjusted stepwise such that first, the mass flow of the liquid circuit 3 is controlled in an optimizing step of the energy process according to a varying reference value or presumption of the computational formula of the desired energy efficiency with respect to the current mass flow or energy flow of the medium emitting and/or receiving energy. After the above-described step, in a situation wherein predetermined conditions are fulfilled, in a second step of the method, the flow in the liquid circuit 3 is adjusted on the basis of at least one reference measurement 10 responding to the efficiency after a change has been intentionally effected in the flow such that the change in the variable describing the effect is compared with the previous step, and after it has been compared whether the new situation is better, the next step will continue similar, opposite or unchanged. The reference measurement 10 may be carried out, for example, directly from the medium emitting energy, as in the example of Figure 1. This, however, is not the only alternative but corresponding information can also be obtained in a different manner. Such an example is shown in Figure 2. In its essential parts, the example in Figure 2 is similar to the example in Figure 1. Similar reference numerals used in Figure 2 indicate similar parts in Figure 1. The application example in accordance with Figure 2 differs from the example of Figure 1 only in the implementation in practice of the reference measurement. In the application of Figure 2, the flow of the liquid circle 3 is adjusted on the basis of the computational result of several measurements 11 describing the efficiency. Figure 2 shows that the measurements 11 reveal the same fact as the measurement 10 of Figure 1 , i.e. the amount of energy emitted by the liquid circuit 3 of the medium 4.

The basic principles described above can be applied in accordance with the underlying idea of the invention in the manner shown in the figures. The basic idea of the invention can, however, be also applied such that the flow of the liquid circuit 3 is adjusted in the second step on the basis of one or more measurements 10, 11 by introducing the measurement results into a computational formula, which determines the adjustment effect of the second adjustment step. The basic idea of the invention and the application mentioned above may also be applied such that the steps are variably emphasized as necessary. The adjustment may, for example, be implemented by adjusting the flow of the liquid circuit 3 dynamically such that the degree of the adjustment effect changes during the adjustment process such that at first, the mass flow of the liquid circuit 3 is controlled, by using weighted adjusting, according to the computational formula of the desired energy efficiency of the energy process with respect to the current mass flow or energy flow of the medium emitting and/or receiving energy, and in the end, the flow of the iiquid circuit is controlled by weighted adjusting on the basis of, for example, one reference measurement 10 responding to the efficiency or on the basis of the computational result of several measurements 11 describing the efficiency. The ad- justment may utilize a function wherein a set value of a detecting element of the measuring device 10 in the medium 4 emitting energy or in the medium 5 receiving energy is determined from the temperature of the liquid circuit 3, and wherein the energy flow through the device 1 emitting energy and/or the device 2 receiving energy is adjusted such that said temperature is maintained. Figure 3 shows a third application of the method of the invention.

Similar reference numerals used in Figure 3 indicate similar parts in Figures 1 and 2. The application of Figure 3 comprises only one device 1 emitting energy and a liquid circuit 3. The adjustment of the application according to Figure 3 is carried out in a similar manner to that described above in connection with the applications of Figures 1 and 2. The example of Figure 3 can also be applied according to the basic idea of the invention such that in place of the device 1 emitting energy there is provided the device 2 receiving energy.

The application examples disclosed above are by no means intended to restrict the invention, but the invention can be freely modified within the scope of the claims. It is thus obvious that the applications of the figures or the details thereof do not have to be identical with those disclosed in the figures but other solutions are also possible.

Claims

1. A method of adjusting mass flow in a liquid circuit transferring energy, the liquid circuit being part of an arrangement wherein one or more devices (1) emitting energy and/or one or more devices (2) receiving energy are connected to the liquid circuit (3) filled with liquid, through which liquid circuit energy is transmitted in a closed circuit, and the mass flow or energy content of a medium (4) emitting and/or a medium (5) receiving energy varies during the energy transfer process, characterized in that the flow of the liquid circuit (3) is adjusted stepwise such that first, in a step of optimizing the energy process, the mass flow of the liquid circuit (3) is controlled according to a varying reference value or default value of the computational formula of the desired energy efficiency with respect to the current mass flow or energy flow of the medium (4) emitting and/or the medium (5) receiving energy, after which, in a second step, after predetermined conditions have been ful- filled, the flow in the liquid circuit (3) is adjusted on the basis of at least one reference measurement (10) responding to the efficiency after a change has been intentionally effected in the flow such that the change in the variable describing the effect is compared with the previous step, and after it has been compared whether the new situation is better, the next step will continue simi- lar, opposite or unchanged.

2. A method as claimed in claim 1, characterized in that in the second step, the flow of the liquid circuit (3) is adjusted on the basis of the computational result of several measurements (11 ) describing the efficiency.

3. A method as claimed in claim 1 or 2, characterized in that in the second step, the flow of the liquid circuit (3) is adjusted on the basis of one or more measurements (10, 11) by introducing the measurement results into a computational formula determining the adjustment effect of the second adjustment step.

4. A method as claimed in claim 1, 2 or 3, characterized in that the flow of the liquid circuit (3) is adjusted dynamically such that the degree of adjustment effect changes during the adjustment process such that at first, the mass flow of the liquid circuit (3) is controlled, by using weighted adjustment, according to the computational formula of the desired energy efficiency of the energy process with respect to the current mass flow or energy flow of the medium (4) emitting energy and/or the medium (5) receiving en- ergy, and in the end, the flow of the liquid circuit (3) is controlled by weighted adjusting on the basis of one reference measurement (10) responding to the efficiency or on the basis of the computational result of several measurements (11 ) describing the efficiency.

5. A method as claimed in claim 1 , c h a r a c t e r i z e d in that the flow of the liquid circuit (3) is adjusted such that a set value of a detecting element of a measuring device in the medium (4) emitting energy or in the medium (5) receiving energy is determined from the temperature of the liquid circuit (3), and that the energy flow through the device (1 ) emitting energy and/or the device (2) receiving energy is adjusted such that said temperature is maintained.