5

The invention relates to a combined sensor-actuator system. Such a system is particularly suitable for detecting and/or controlling deposit on a surface, more particularly0 on a surface of for instance a reactor, heat exchanger or conduit .

It is known in practice that many surfaces are susceptible to deposit. This for instance relates to

deposition of ice, scaling or limescale, fouling and

5 precipitation of salts. This is understood to include, among others, deposit, growth and encrustation. The effectiveness of a device or process is reduced as a whole due to presence of deposit. It is also known in practice to remove for instance ice using a scraper. It is also known in practice0 to control deposit using the periodic addition of chemicals and/or throughflow or flushing of the system with the surface on which the deposit is or is assumed to be present. Such a periodic cleaning operation can be performed on the basis of elapsed time as well as on the basis of a pressure5 drop measurement or decreased heat transfer. This has the consequence that periodic measures have to be taken, wherein an installation with a surface on which deposit may occur is temporarily taken out of operation. In the case of ice formation it may thus be necessary to melt the ice on the0 installation. Such an installation then has to be restarted.

An object of the invention is to obviate the above stated problems.

This object is achieved using the combined sensor- actuator system according to the invention, the system

5 comprising: - a sensor matrix which can be arranged on or at a surface,

- an actuator which can act on the surface for the

purpose of controlling the deposit; and

- control means operatively connected to the sensor

matrix and suitable for detecting a local deposit and controlling the actuator on the basis of a sensor signal .

Arranging a sensor matrix on or at a surface, wherein this surface may be susceptible to the formation of a deposit thereon, achieves that such formation of deposit can already be detected at an early stage. This formation can be detected locally, and also at an early stage, by providing a matrix over the surface. Also provided is an actuator which is suitable for controlling this formed deposit. By

controlling this local deposit using the actuator, this deposit can be controlled at an early stage with a

relatively simple and short activation of the actuator. The effectiveness of the whole device is thus maintained. The activation for controlling the locally detected deposit is preferably carried out on-line, optionally during operation. An additional advantage hereof is that deposit control can be performed more continuously such that occurring peaks or declines in the effectiveness of the overall device or process are avoided. Further additional advantages are the adjustment of the control actions in time, whereby these are not performed too early (loss of chemicals, process

downtime), or too late (loss of effectiveness), or performed on too large a scale (loss of effectiveness) .

Such a device in which the sensor matrix can be applied is for instance a heat exchanger, reactor, conduit or pipe. The deposit occurring is for instance ice, scaling such as limescale, fouling and salts precipitated onto the surface, such as sodium chloride or other soluble salt. Other types of device and other types of deposit are otherwise also possible . It is thus even possible to control ice formation on wind turbines or aircraft wings. Other examples of possible applications are detection of precipitation of salts and application in so-called Eutectic Freeze Crystallisation, or crystallisation. In addition to preventing limescale in a reactor, the system according to the invention can also control such deposit in a water purification plant. It is also possible, for instance in case of a cooling surface, to integrate the sensor matrix in a heat-conducting structure or layer so that the sensors can perform measurements and the cooling of the medium in the associated device is maintained .

A particular additional advantage of the system according to the invention is that occurring deposit can be determined locally and preferably also be controlled locally. The deposit is preferably controlled here at the most critical local point in order to thereby enable an effective control. It is hereby possible to take action against the formation of deposit in very efficient manner with minimal energy consumption. The effectiveness of the installation of which the relevant surface forms part is thus maintained in the best possible manner. A further additional advantage is that the controlling action can be geared to the local quantity of deposit and that unnecessary and/or excessive action is not taken. This enhances the overall effectiveness and efficiency of the installation.

The sensor matrix is preferably used to detect the deposit and the occurring local deposit is then controlled with the actuator. Additionally or alternatively, it is also possible according to the invention to perform an action with the actuator whereby, using the sensor matrix, a response measurement can be performed for the purpose of thereby detecting for instance the local deposit. If desired, it is possible to utilize the actuator once again to control this deposit. The local measurement values can optionally be

displayed visually. This further improves operation of the relevant device or performing of the process.

In an advantageous embodiment the sensor matrix

comprises temperature sensors. Temperature gradients and/or temperature differences within the matrix can hereby be determined and optionally monitored in time. It is possible to infer from detected changes whether a deposit is forming. This deposit can then be controlled with the actuator.

Additionally or alternatively, the sensor matrix can be provided with conductivity meters, capacitive sensors, optical sensors, pressure sensors and/or pH, ion-selective electrodes .

In an advantageous embodiment according to the present invention the actuator comprises heating means.

Providing the actuator with heating means makes it possible to add an amount of energy to the surface on which the deposit is discovered. The actuator is preferably embodied such that the energy can be supplied at the

position of the detected local deposit. The detected deposit can hereby be controlled in very effective manner with a relatively small amount of energy.

The heating means preferably comprise electrical heating means. An amount of energy can be supplied locally to a surface by using electricity. It has been found that an effective control of detected local deposit is hereby possible .

In an advantageous preferred embodiment according to the present invention the actuator comprises a supply channel suitable for carrying a deposit-controlling fluid to the surface.

Providing at least one, and preferably more, supply channels enables a deposit-controlling fluid, for instance acids, chemical control agents etc., to be transported preferably to the position of the detected local deposit. The channels are preferably formed as so-called microchannels .

In an advantageous preferred embodiment according to the present invention the actuator activates a chemical process.

Such a chemical process relates for instance to an electrolysis process such that reagents can be dosed at a specific location. Limescale for instance can in this way be removed locally.

In a further advantageous preferred embodiment

according to the present invention the sensor matrix is provided in or on a foil material.

Providing the sensor matrix in or on a foil material achieves that such a sensor matrix can be manufactured in effective manner and can likewise be arranged in effective manner on a surface. Making use of a heat-conducting foil material, for instance a metal, also enables application in or on a cooling or heating surface.

The foil material preferably comprises at least a part of the actuator. A combined sensor-actuator system according to the invention can in this way be provided in effective manner by being manufactured in combined form and preferably also being arranged in combined form on the surface.

By providing the sensor-actuator integrally with the foil material, production thereof can be scaled up

relatively easily. This enables cost-effective manufacture, which increases possible application in practice. A

combination of printing and other ways of applying

components is also possible if desired. The electronic components (for instance sensors and actuators) can thus be co-printed or be assembled at a later stage.

The invention further relates to a foil provided with a combined sensor-actuator system as described above.

Such a foil provides the same effects and advantages as described for the sensor-actuator system. Use of the foil makes it possible for the combined sensor-actuator system to be produced in relatively simple manner, and preferably also for it to be arranged on the surface, or even form part thereof, in relatively simple manner.

The invention also relates to a device provided with a sensor-actuator system as described above.

Such a device provides the same effects and advantages as described for the combined sensor-actuator system and/or the foil. Such a device preferably comprises at least one of a heat exchanger, heating boiler, water conduit and reactor.

The invention further also relates to a method for detecting and/or controlling deposit on or at a surface, comprising of providing a sensor-actuator system as

described above.

Such a method provides the same advantages and effects as described above for the combined sensor-actuator system, the foil and/or the device.

In an advantageous embodiment of the method according to the invention a signal is generated with the actuator and a response is then measured with the sensor matrix for the purpose of thereby detecting a local deposit. The deposit can hereby be detected locally in effective manner. It is thus possible for instance to measure the local temperature increase after briefly supplying heat for the purpose of determining an indication of the thermal constant. This constant can be used as measure for determining whether deposit is present, and to what extent. It is optionally possible to then use the actuator again in order to control the detected deposit.

Further advantages, features and details of the

invention are elucidated on the basis of preferred

embodiments thereof, wherein reference is made to the accompanying drawings :

- figure 1 is a schematic representation of the sensor system according to the invention;

- figure 2 shows an overview of electronic components used in the system of figure 1; - figure 3 is a visualization of a temperature profile;

- figure 4 is a schematic overview of a matrix of the system of figure 1; and

- figure 5 is a schematic overview of a possible

embodiment of the device according to the invention.

A sensor system 2 (figures 1 and 2) comprises a foil 4 on which a copper layer 6 is arranged as cover layer. The use of other materials as cover layer, such as other metals or plastic, is likewise possible according to the invention. Circuits can be embedded in a multi-layer foil material if desired. Because of the good heat conduction, the shown embodiment with copper layer 6 has been found highly

suitable for application in a heat exchanger.

In the shown embodiment a number of sensors 8 are arranged on copper layer 6. Metal actuators 10 are also arranged on or in foil 4. Actuators 10 are connected via openings 12 to the other side of foil 4 and are for instance controlled in this way. A read unit 14 reads sensors 8 and actuators 10 are controlled via controller 16, for instance via the same data line. In an advantageous preferred

embodiment unit 14 reads sensors 8 in a specific sequence. When applied to a matrix 18 of temperature sensors, a visualization 20 (figure 3) of a surface of a device, for instance a heat exchanger, can hereby be realized.

In a shown embodiment of a sensor matrix 22 (figure 4) according to the invention the individual sensors 24 are connected to earth A, optionally being mutually connected for this purpose. Matrix 22 is provided with power by the power MUX array component 26. Measurement data is read by read unit (read/drive MUX) 28. In the shown embodiment the output voltage employed is about 2.5 Volt at 0°C. In a possible embodiment, a MOSFET switch 30 (figure 5) is provided for activating a heating element 32, wherein the gate threshold of switch 30 amounts in the shown embodiment to 2.5 Volt. Heating 32 is switched off during the reading. During heating, a voltage of about 5 Volt is carried from unit 28 to switch 30 for the purpose of activating thereof. Component 26 transmits current using a semiconductor switch controlled by the controller. Unit 28 analyses the received measurement data using AD converters which are read by the controller. If desired, heating 32 is provided with power from unit 28. It will be apparent that other embodiments are likewise possible according to the invention.

Diverse combinations of sensors and actuators are possible according to the invention. The tables below state a number of possible variants which can be mutually

combined. It is noted here that it is also possible

according to the invention to use other combinations,

sensors and/actuators.

Table: Sensor

Sensor Sensor element Action Example of use type

Temperat Resistor, Resistance is Ice detection, ure temp . - measure of temperature dependent temperature profile resistance

Integrated Emitting a Ice detection, circuit Voltage, or temperature digital readout profile

Thermocouple Readout Voltage Ice detection, difference temperature profile

Flow meter Flow and flow Ice detection, profile temperature profile

Conduct! Electrodes Impedance Chemical

measurement (AC or composi-tion, on DC) ice detection

Capaciti Insulated Application of AC Chemical ve electrode potential , detection, capacity between scaling electrode can be detection, ice read detection

Optical LED and optical Light transmission Scaling

detector is detected detection

Pressure Microphone, Pressure Scaling ice, pressure sensor (difference) air bubble

detection in detection combination with

sound source

Table: Actuator

Actuator Actuator Action Example of use type element

Thermal Resistor Application of Melting of ice,

electric power local

results in temperature change element being in the medium, heated melting or

dissolving of salts or organic

substances

Electroly Bare Application of Change in chemical sis electrode electric power composition at

s results in a interface. Free

chemical reaction chlorine, copper.

Light LED/other Application of Visualization of power illuminates measurement results, the activation more colours location in a possible

determined colour

uv LED Application of Disinfection

power will

provide UV

radiation

Sound Piezo/oth Application of Scaling removal, er movement, sonic interface mixing energy

Thermal Heating, Detection of heat readout losses: flow rate. device Detection of heat pulse speed: medium detection etc.

A further example of a possible application lies in the field of melt crystallisation, wherein an organic melt

(envisage melted butter) crystallises. If the

crystallisation is intended in the form of a suspension, growth of solidified melt on the heat exchanger is

undesirable. Applications are in this way possible with organic substances or salts whose solubility decreases sharply with the temperature (ammonium nitrate, sodium sulphate etc.) .

A sensor matrix 18,22 is read for the purpose of measuring a fouling etc. Information concerning the local fouling etc. is hereby obtained. Using local actuators 10 the fouling etc. is then controlled in order to thus perform the desired action locally. Such a local detection and control results in effective and efficient operation.

The electronic operating principle of the active matrix is demonstrated with an experimental embodiment. The

embodiment comprises a sensor matrix of 5 sensors which are separately readable and have coupled thereto per sensor a thermal actuating unit. The eventual application can of course comprise a plurality of these sensor matrices. The sensors in a matrix can be read and controlled one by one. A whole row of sensors can also be read simultaneously, or the thermal sensors of this row can be controlled

simultaneously, which increases the reaction speed. Only one row at a time can be selected per sub-unit (matrix) . The read or actuation speed was limited in the experimental embodiment to several tens of thousands of times per second, although higher speeds can be achieved with other

components. The power which can be supplied per heat actuator is kept limited to 5 to 10 Watts per actuator at a 5 Volt supply voltage. In the prototype the matrix is read by an intelligent microcontroller which collects and transmits the data to a computer which visualizes and controls the process. The experimental embodiment was found to function according to expectation and to meet

requirements .

The present invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged. It is thus also possible to utilize the combined sensor-actuator system for (indicative) measurement of liquid flows, for instance on the basis of temperature or conductivity. Use can advantageously be made here of an embodiment based on the foil as described above.