DE2758831A1 - Detection method for surface deposits - uses differential heat flow measurement in comparison with reference surface - Google Patents

Abstract

The detection and measurement of deposits, such as scale or wax on different types of surfaces, is determined by thermal measurements on a test sample compared with a reference. This procedure is sensitive enough to detect deposits without having to wait until they effect operation of a system. A test and a reference surface are submitted to a fluid environment and are subjected to heat flow in a known relationship. The transfer of heat between the surfaces and their fluid environments is compared. Heat flow is applied differentially to decrease difference in temp. of the fluid. These measurements are then used to determine their effect on deposit formation.

Description

Method and device for detecting and measuring

Deposits The invention relates to the detection, measurement and control of the formation of adhering precipitates such as scale, paraffin, Wax, etc. on different surfaces.

There is a need for one that is practical and commercially useful Procedure to determine whether a system contains significant scale or other deposits form or not to determine the conditions under scale formation could occur and determine the conditions among which such formation can be prevented either by adding by chemical scale inhibitors or by controlling process variables.

It is very important that the process be commercially available Apparatus can be carried out, which are always ready and for their Operation does not require a qualified chemist or scientist. It is also very It is important that the procedure is so sensitive that there is a tendency of a scale formation system is registered without having to wait until the precipitation significantly disrupts the monitored system.

In the past, the systems were usually inspected visually, to detect adhering scale and other deposits. Another common one The method consisted of measuring changes in the heat transmission rate or the Liquid flow rates. those to maintain a certain Heat transfer rate were required. These known methods have the considerable Deficiency that the disorder that is to be prevented, so z. B. the reduced Rate of heat transfer, must occur before any presentational measures are taken can.

In Applicants' US Patents 3,848,187 and 3,951,161 become extreme exact and very sensitive methods are described in which the electrical contact resistance is used to prevent the incipient formation of a precipitate, such as scale, Paraffin, wax or the like to be scanned. The methods described in these patents and devices are efficient and highly sensitive, but require movable ones Parts that are unsuitable for operation over long periods of time. Also wear moving parts add to complexity and cost.

A difficulty with some known systems is that the measured temperature varies with many parameters of the fluid in which the test surface is immersed. In some systems, the flow rate by a test cell increased to the cell temperature on the Temperéttur of the entering Stabilize fluid. With such high flow velocities however, the flow rate itself becomes critical. So can with one device high sensitivity, relatively small changes in one of a large number of parameters of the fluid cause an output signal to go from zero to full deflection changes even if there is little disturbance of the parameter such as the flow rate is present. The fluid parameters that affect the temperature measurement include the speed, the viscosity, the temperature, the composition, the thermal Conductivity, the flow pattern on the surface, which changes with the Roughness can change due to increased rainfall, and other flow characteristics.

It is therefore with the known measurements that are based on the acquisition of Changes in heat transfer due to changes in precipitation are necessary to keep all these fluid parameters constant for each measurement period hold so that the fluid at the test surface has the same effect on the surface temperature has during one measurement period that it has during a subsequent measurement period exercises. Such an identity of the fluid properties is also under laboratory conditions extremely difficult to get to. In practical circumstances and when used in Is outdoors, especially when an apparatus is used for long-term monitoring control of such fluid properties is impractical.

The known methods thus represent the accumulation of precipitates only solidly when a considerable amount of precipitation has already built up and can already lead to a considerable disturbance, and further enable it the known methods also fail to produce a specific liquid in a relatively short time Time to check with regard to their tendency to precipitate.

In the case of the original system, a thermal bridge is added used the heat transfer properties of test and reference surfaces that are in identical Fluid environments are immersed, compare to the heat transfer properties the test area to be determined essentially independently of the fluid environment. The thermal bridge is brought into equilibrium, the dead area becomes stronger Dimension to the formation of scale or other covering leaves as the reference area, and a comparative measurement is carried out on the two surfaces which are identical Exposed to fluid environments. The procedure is carried out by using a single probe carried out one or more surfaces that are heated and their temperature difference is measured. The measurement results are adjusted to compensate for the effects of a varying fluid environment.

The device according to the invention has no moving parts on and is relatively insensitive to changes in the fluid environment and can can easily be embodied in a single probe, which is in the actual fluid of a to be monitored system can be suspended, with either an intermittent or continuous measurement and recording of precipitation or slope to precipitate formation with such sensitivity that the undesired Precipitation is signaled before the system through the precipitation Suffers damage.

The invention is illustrated in greater detail using exemplary embodiments explained. The figures show: FIG. 1 a functional diagram of a thermal according to the invention Bridge; 2 shows a sectional view of a probe designed according to the invention; Fig. 3 is an exploded perspective view with parts broken away and the components of the probe of Fig. 2 are shown; 4 along a section the line 4-4 of Figure 2; Fig. 5 is an enlarged partial longitudinal section of the Probe of Fig. 2; Figure 6 is a diagram of those used with the probe of Figures 2-5 Circuits; Figure 7 is a diagram of other electrical circuitry associated with the probe Figures 2-5 can be used; 8 shows further modified electrical circuits for use with the probe of Figures 2-5; and FIG. 9 shows an application of a boiler stone probe in a fluid system shown by way of example.

An essential feature of the invention is that the heat transfer properties a surface covered with a precipitate can be quickly detected or measured without the need for precise control of the fluid environment. And indeed will a new type of thermal bridge is provided, in which a flow of heat through first and second heat flow paths over first and second surfaces flows to first and second fluid environments; The two fluid environments are such that they inevitably have a fixed relationship in terms of heat transfer properties exhibit. This solid relationship will easiest to use achieved from substantially identical fluid environments. Instead of that now essentially the temperature on a single surface along a single heat flow path is measured, one essentially observes the temperature difference between similar ones Places in each of the heat flow paths and ultimately performs a comparison or a Difference measurement of the temperature drop along the first and second heat flow paths and the first and second fluid environments. Differences in thermal resistances of the two heat flow paths, the z. B. on differences regarding the formation of precipitation are made easy by means of such a comparison recognized.

When using this thermal bridge, it is not necessary to the same fluid parameters or a known relationship thereof from a measurement to maintain the next. It is only necessary to use the same relative Maintain parameters of the two fluid environments at the time of measurement. Within certain ranges, these parameters can change from one measurement to the next vary without seriously affecting the detection or measurement.

A thermal bridge that corresponds to this aspect of the invention, is shown in Fig. 1 in functional terms, wherein a heat source 18 a Generates heat flow that flows via first and second heat flow paths 20 and 22, respectively, each of which has a surface that is in contact with each one of the two fluid environments 24 and 26 is located, which heat to one schematically Discharge indicated heat sink 18. In the case of the heat sink, it can end up being around act the fluid itself, which during the measurement continuously on the surfaces can flow by. The heat flow paths 20 and 22 contain those parts of the first and second precipitation gauges (test and reference elements) that are between fluid environments 24 and 26 in contact with them and points 30 and 52 are located within the measuring elements. Temperature sensors are located on the Points 30 and 32. The parts of the precipitation gauges between points 30 and 32 and heat source 18 may be used as part of this discussion for the purposes of this discussion the heat source.

One can have a flow of heat from source 18 via paths 20 and 22 flow for certain purposes in a predetermined relationship, e.g. B. for the purpose Compensation for an asymmetry of the paths, as will be described below. For those here given explanation is however assumed that the heat flows over the Paths 20 and 22 from a constant heat source 18 with equal heat flux density take place and that therefore the relative temperature drop along the two paths of whose relative thermal resistances are determined.

It is also assumed for purposes of illustration that none thermal conduction occurs between the two paths.

The thermal resistance, in addition to that of the first heat flow path 20 and the first fluid environment 24 is present, can in one branch of this thermal bridge can be neglected. The thermal resistance can be similar in addition to the second heat flow path 22 and the second fluid environment 26 is present, can be neglected in the second branch of the thermal bridge.

As long as in the bridge of FIG. 1 the first and second fluid environments 24 and 26 have heat transfer properties that are closely related to one another stand, or in the special case the two fluid environments with regard to the thermal Resistance are identical to each other, it does not matter how the two look together change if only they change in the same way. In other words, it is at Use of this thermal bridge only necessary that the relative effective thermal transfer properties of the two fluid environments from one measurement to the next remain constant, but with the thermal properties themselves can change. This condition can be obtained relatively easily, in particular in two adjacent parts of the same fluid system.

When the relative effective thermal transfer properties of the two fluid environments 24 and 26 are constant, is the temperature difference at points 30 and 32 an accurate indication of the temperature drop along the Path 22 relative to the temperature drop along path 20. If the two paths same thermal resistance or specific thermal conductivity have, the temperature difference displayed in a measuring device 34 between points 30 and 32 will be zero if one has equal heat flows from source 18 for the two routes 20 and 22. On the other hand, if there is a difference in thermal resistances of the two paths 20 and 22, as they are, for. 3.

is caused by a different draft formation in which one surface is covered more than the other, so will be with the same input heat flows a difference in temperature drop along the first and second Surrender to the way. This difference depends on the difference in thermal resistances of the two paths, which in turn depends on the difference in the formation of precipitation depends on both surfaces. The difference is displayed on a measuring device 34, the reading of which represents the temperature difference (aT) at points 30 and 32.

This difference is independent of changes in the fluid environment, if one assumes a symmetry of the surfaces and an ideal apparatus. at However, very high sensitivities can lead to changes in asymmetries and deficiencies in the equipment the fluid environment and thereby impair the measurement. Below methods and circuit arrangements are described with which such effects can be compensated, thereby further increasing the sensitivity will.

The thermal bridge described above can be in many different Molds can be used to practice the invention. In general is a test element, which has a heat flow path analogous to z. B. the heat flow path 20 of Fig.

1 has, with one surface immersed in a fluid, the Tendency to form precipitation is to be determined.

This surface is left so submerged for such a time and under such conditions that normally the fluid in which it is immersed is, to some extent, causes precipitation thereon. Then the The thermal bridge described is used to prevent precipitation to measure or record the surface. For such a measurement or acquisition the test surface and the surface of a second element, which as Reference element can be designated and the heat flow path 22 is analogous, in im substantially identical fluid environments immersed or immersed in fluid environments, which have known relative heat transfer properties. The reference surface shows z. No precipitation at present. The test and reference elements have a known one Relationship - such as identity or almost identity - of heat transfer properties, before the test surface of the possibly to Precipitation exposed to a prone fluid environment. While they are submerged, be both surfaces heated by the source 18 for the measurement. The relative > Heat transfer along paths 2 () and 22 or, more precisely, via the interface between the test surface and its fluid environment on the one hand and between the The reference surface and its fluid environment, on the other hand, are compared. This Comparison gives the desired indication of the test surface covering.

Such a method results in a comprehensible without additional steps and measuring plaque on the test surface compared to that on the reference surface. For the acquisition or measurement, the thermal bridge is initially adjusted, and although preferably while the test surface and the reference surface are in the same State, e.g. B. in a clean layer-free state, such that in such a State the meter 34 provides a first known reading, such as. B. Zero. After a precipitate on which the test surface has the potential to precipitate causing conditions has been exposed, while the reference surface has not has been or to a lesser extent exposed to such conditions has been or has been cleaned or otherwise protected against the formation of precipitation has been, the difference measurement is repeated, with the difference from the measuring device 34 is displayed. The difference between the reading of the meter 34 in this Measurement period and the measurement value during the initial measurement period is a display for changing the thermal transfer properties of the test surface afterwards the period during which the bridge was initially adjusted. So that is The measurement result is a measure of the formation of precipitation.

A measurement period can have a duration of 5-15 minutes, with how long must only be sufficient for the arrangement to be thermally and electrically stabilized while the heat input flow from one state to another is changed. A typical precipitation formation period, i. H. the time between two consecutive measurement periods, can be on the order of one to four Hours lie.

The cyclically alternating succession of measurement and precipitation formation periods continues as long as monitoring of the fluid system is desired.

The method and apparatus described herein can can be used for the rapid determination of conditions under which an adherent Precipitation is deposited. It is only necessary to have a certain condition during the precipitation period and the effects of precipitation to measure under this condition during a subsequent measuring period.

So z. B. by the fact that the test surface is supplied Heat or the temperature or the composition or the viscosity of the monitored Liquid during the precipitation period selects the precipitation processes examined individually under such special conditions.

It should be clear that the principles of the invention can be embodied in many different apparatuses and circuits / non, which perform the functions of the'besUhriebenen thermal bridge. A great variety of heat sources can be used including separate internal or external heating devices, electrical heating or flow heating, for example with steam or direct resistance heating. A wide variety of temperature sensors can be used including independent of the heating devices Temperature sensors such as thermistors, thermocouples and the like.

There can be many different ways to achieve a different rollover can be used on the test surface and the reference surface. Applicants' earlier patents 3,848,187 and 3,951,161 describe a number of such methods of increasing the tendency to precipitate in which the precipitation rate or the precipitation formation potential is increased significantly and thereby the sensitivity of the measurement is increased considerably. Such Methods can easily be used to determine the test surface and the Covering the reference surface differently with precipitation and thereby a greater precipitation and a greater likelihood of precipitation on the test surface than on the reference surface. The methods physical protection is provided for different types of precipitation the reference surface during the time that the test surface is subject to precipitation conditions is exposed. Thus the reference surface can be removable or separate from the test surface and may from the fluid environment during the precipitation period removed. The reference surface may reflect the precipitation formation conditions exposed together with the test surface, but before a subsequent one Measurement after the precipitation period. The reference surface can be provided with a protective layer. Chemical inhibitors can be used limited to an area in close proximity to the reference surface are. For those fluid systems in which the formation of precipitation by low As temperatures are increased, cooling devices can be used to control the temperature lower the test surface below that of the fluid environment, while higher Temperature is maintained at the reference surface or the reference surface is protected against precipitation in another way.

Another method to have a different precipitation Achieve, consists in the supply of the same heating power to the reference surface and the test surface during precipitation and concurrent use a lower fluid temperature around the reference surface. It will then the fluid flow is increased during a measurement period or other measures are taken, around the fluid environment of the reference surface and that of the test surface to match.

Finally, both the test surface and the reference surface can but the heat input to the test surface is several times higher is than that to the reference surface.

The probes can be designed so that they a flow of the observed Provide fluid either inside or outside the probe. The latter Training is chosen to achieve further aspects of the invention.

A probe having an external surface is preferred because it is easier to inspect and easier to dry clean.

In Fig. 2 an embodiment is shown, which is preferably for Certain aqueous systems such as cooling water systems are used with the probe however, it can also be used with other systems. The probe of Fig. 2 is especially for use with various adjustment and compensation circuits suitable, which are still to be described and allow quantitative measurements to be carried out with a very high degree of sensitivity and accuracy.

According to FIGS. 2, 3, 4 and 5, the probe means consists of an elongated one Hollow tube made of thin-walled thermally conductive material such as stainless steel and is streamlined at its upstream end 66 to avoid the disturbance to keep the flow low, and is of sufficient length to allow the test and reference heaters and the temperature sensors axially spaced from each other to keep. An annular peripheral region 68 of the shell 64 is used as a reference surface is used and a similar annular peripheral region 70 located downstream of area 68 is used as a test surface. Inside the jacket 64 and in fixed relation to this an electric cartridge heater is arranged, may be of the type described in U.S. Patent 2,831,951 and spaced apart and independently activated resistance heating wire coils 72 and 74, the are mounted within a cylindrical metallic tube 76. Heating current lines 78 connect the heating coils with external heating power levels, which will be described later will.

To the features of the thermal bridge shown in Fig. 1 in the To implement the embodiment of Figures 2, 5, 4 and 5, it is desirable to use the Temperature difference between the reference surface 68 and the test surface 70 increases measure up. As already mentioned, many different types of temperature sensors can be used be used. So you can use conventional thermocouples, thermistors or other temperature-sensitive ones Devices on the test surface and the reference surface inside or outside attach the same, or even inside the heating cartridge itself, to the desired one To measure the temperature difference.

It should be remembered that in the case of the thermal bridge described The measurement carried out does not require a temperature measurement at a certain point, it only requires the measurement of a temperature difference. There is only one temperature difference must be measured, this difference can be easily identified at surfaces 68 and 70 measure by connecting a single pair of thermocouples to these surfaces, d. H. one wire connects to surface 68 and the other wire connects to surface 70 connected provided that the wires are thermoelectrically different are made from the material of the electrically conductive sheath of the probe. When a temperature difference exists between the areas 68 and 70, a thermoelectric potential gradient is created along the probe between these areas.

Therefore, tension appears between the two with the test surface or wires connected to the reference surface, which are a measure of the temperature difference is.

The connection of such thermocouple wires, which relative to the probe jacket, however, they are not thermoelectrically dissimilar relative to one another, with the exterior the sample jacket or the connection of other temperature sensors to the exterior of the Sample jacket is undesirable because it creates the structure of the flow along the The outside of the jacket can be disturbed and cleaning of the probe is made more difficult. In the case of the probe described in FIGS. 2, 3, 4 and 5, the temperature difference is measured between the test surface and the reference surface in that thermoelectric Wires are connected to the inside of the probe jacket.

The type of connection of the thermoelectric wires shown here also gives a good heat flow path, namely a low thermal path Resistance, from the heating devices to the test surface or the reference surface and to the thermoelectrically dissimilar connecting wires. Around Connecting the thermocouple wires will be first and second thermally conductive spacers 80 and 82 mounted on the heating tube 76 above the respective heating coils. These pods 80 and 82 sit in a tight interference fit on the heating tube and are in a tight fit fixed system with the interior of the probe sleeve. The sleeves can be made from 1020-1040 Soft iron, Kungfer or another material with good thermal conductivity and thermoelectric properties that are different from the material the thermocouple wires. All thermocouple wires are made of the same material such as b. from ronstantan.

As can be seen in Figures d and 4, each sleeve has a plurality of circumferentially spaced grooves or slots running in the longitudinal direction, which together with the probe jacket 64 form a plurality of passages, which extend in the longitudinal direction of the sleeves. The grooves of the sleeve 82 rind with the Reference numerals 84a, 84b, 84c, 84d, 84e and 84f, and similar longitudinal grooves 86a, 86b, 86c, 86d, re and 66f are formed in the sleeve 82.

For sensing the temperature difference between the reference surface and the test surface, the thermoelectric wires are attached to the necks. A plurality of electrically insulated thermoelectric wires are attached to the sleeve 80 attached, such as constantan wires 82a, 82b and 82c stripped with their Tips such as tip 90 are attached to the sleeve, namely on in the circumferential direction spaced points around the sleeve. The sleeve 82 is with a similar group provided with insulated thermoelectric wires with stripped tips, such as the tip 91 which attaches to the sleeve at circumferentially spaced points are attached.

The wires are z. B. by welding or soldering attached to each sleeve, circumferentially spaced from each other by allow a temperature difference measurement at points around the perimeters the test and reference surfaces are spaced apart.

In the example shown, there are three thermocouple connection points on each sleeve intended. For each sleeve, the ends remote from the sleeve are associated with the three thermoelectric wires electrically and thermally connected to each other, as yet is described to determine a temperature difference which is the difference between Average temperature values of circumferentially spaced parts of the test and represents reference areas.

The sleeve 82, which is identical to the sleeve 80, also has three electrically insulated thermoelectric constantan wires 86a, 86b and 86c, which are housed in every second of the six slots and with their stripped Ends are bent into the circumferential slot 98 and welded to this, as shown at 91 for wire 96c.

To ensure heat conduction to the sleeves and thus to those connected to them enlarge thermoelectric wires from the outer surface of the probe jacket, is the shell with a plurality of circumferentially spaced holes like with the holes 700a; 100b and 100c. Located in the example described the effective thermocouple connections on the test and reference surfaces between the steel jacket and the constantan wires, although the mechanical connections exist between the wires and the sleeves, which are in good thermal contact with the jacket and form part of the thermoelectric circuit.

The holes may be in alignment with such areas of the underneath lying sleeves, which are removed from the grooves therein. After assembling these holes can be used to insert solder around the sleeve and to put the outer coat together well. Alternatively, the holes can be omitted and the brazing material can be in before assembling the sleeves with the jacket the grooves are placed. Subsequent heating then leaves the solder flow into the spaces between the jacket and the sleeve. If it is as necessary or if it is deemed desirable, the heat transfer from the outer surface of the jacket 64 to improve the measuring thermocouple connection, the jacket is placed on the Spacer sleeves and forged against them, ensuring that this Forging without significant disruption of the desired flow properties of the smooth and uninterrupted outer surfaces of the jacket. Preferably the forging of the jacket onto the sleeve is carried out before soldering.

It can thus be seen that the cartridge heater with its two separate heating coils is firmly fixed to the two spacer sleeves, which are in a press fit sit on it and that the sleeves by forging and / or soldering within the probe jacket are attached to this, creating a solid, compact probe that does not have a having moving parts.

The heater 72 and the reference surface thermocouple connections are symmetrical within the annular reference surface and circumferentially arranged around it, with the reference surface of the one extending around it Section 68 of the probe jacket is formed. The heater 74 and associated thermoelectric Wire bonds are within the annular area forming the test surface 70 of the probe jacket and arranged around this area.

The reference and test sections of the probe are a distance apart removed that is sufficient to provide sufficient thermal insulation between them to ensure.

If desired, additional thermal insulation can be added between the reference and test surfaces.

A suitable fitting such as this is provided on the probe jacket External thread 102, which is connected to a fitting part 104 having an internal thread cooperates which is attached to a system not shown in Fig. 2, the Fluidum is to be measured with regard to its tendency to form precipitates.

A housing 106 is attached to the outer end of the probe, which electronic components such as a preamplifier 108, a plug receptacle 110 for receiving heating and measuring power cables and a plug receptacle 112 for connection the thermoelectric lines and the preamplifier lines with external circuits, which will be described later.

It can be seen that the probe shown in Figures 2-5 has all of the elements the thermal bridge shown in Fig. 1 contains with the exception of the measuring device and Switches that are provided outside the probe and with its heating device and the thermoelectric wires are connected. The three (or more) thermoelectric Wires of a sleeve, such as wires 92a, 92b, 92c, are within housing 106 connected to each other, and accordingly are the three (or more) thermoelectric Wires 96a, 96b and 96c of the test surface sleeve within the housing 106 with each other connected so that two signals are provided to the test surface or are assigned to the reference surface and each signal has an average value represents of temperatures, which rings at circumferentially spaced points have been scanned around the test surface or the reference surface.

The probe described forms a thermal bridge to that in FIG. 1 Art shown. It has a heat source in the form of heating coils 72 and 74, one first heat flow path via sleeve 82 and test area 70 of jacket 74 and a second heat flow path via sleeve 80 and reference area 68 of the shell. Both heat flow paths are in contact with the mutually identical or almost identical fluid environments created by the flow of the same fluid at the Probe past and around it in the direction of arrows 116 are formed.

Various electrical circuits are shown in the drawings for the probe of Figures 2-5, showing just a few of the different possibilities compensation, measurement and control. The circuit of 6 contains an adjustable compensation for thermal asymmetry. The probe is shown schematically including its shell 64, the reference surface 63, test surface 70, reference and test heaters 72 and 74, and the thermoelectric reference and test transition points 90 and 91, all of these parts the parts shown in detail in FIGS. 2-5 are intended to indicate schematically.

Heating energy is from an energy source (not shown) via a Transformer 118 related, its secondary winding 119 with the arm 120 of a resistance divider 122 is connected, the ends of which are each connected to one of two interconnected switches 124 and 126 are connected. Switches 124 and 126 are on lines 128 and 130 connected to opposite ends of heaters 72 and 74, the themselves are connected to each other and their connection point to the other end the secondary winding of the transformer 18 is connected. Lines 128 and 130 from the ends of the heating wires are also connected to coupled switches 132 and 134, the one with the movable tap 136 or with one end 138 of a secondary winding 139 of a transformer 140 are connected, the primary winding of which with a second Source of electrical energy (not shown) is connected.

The three thermoelectric wires are shown in Fig. 10 through the wire 96 and are connected to terminal 97 in a common isothermal junction box 142 connected to each other. Similarly, the three are thermoelectric Wires shown in Figure 10 by lead 92 to terminal 99 in of the junction box 142 are connected to each other. Connect common copper wires 144 and 146 these thermocouple clamps to the inputs of a differential amplifier 148.

The amplifier 148 produces an output signal which corresponds to the difference between the two averaged thermoelectrically generated voltages at his is proportional to both inputs, whereby this difference can be represented as et ~ t where is the temperature of the test surface and dr is the temperature of the reference surface is.

A potentiometer 150 for zero point adjustment contains a variable one Resistance to which potentials of opposite polarity are applied and its output to the temperature difference signal from amplifier 148 in a resistive summing network 152, 154 is added, the output signal of which is sent to a suitable display measuring device or another display, processing or recording device 156 will.

A measurement current is supplied to both heaters 72 and 74 from the transformer 118 fed through switches 124 and 126 when these are closed, and on Precipitation current, which only heats the test surface, becomes the heating coil 74 fed from transformer 140 when switches 132 and 134 are closed are. The meter 156 gives the data on the surfaces 68 and 70 during a measurement period determined temperature differences again.

In every apparatus there are certain asymmetries, as it is practical it is not possible to manufacture a probe in which the test surface 68, the sleeve 80, thermoelectric junction 90, and heater 72, all of these Elements are connected to each other and interact thermally, physically and electrically, are designed exactly the same as the test surface 70, the sleeve 80, the thermoelectric Connection 91 and heater 74. The test and reference parts are also then asymmetrical if extreme care is taken in manufacturing the Manufacture reference and test parts exactly identically.

Cause such asymmetries between the reference and test parts of the probe Changes in the measured values supplied by the measuring device during a measurement, d. H. the sensed temperature difference, these changes being due to changes in the fluid environment caused.

However, it has been found that when the input heat flows to the test and bezu surfaces in the clean state of the same can be varied, there is a point in the relationship between the input heat flows at which the measured temperature difference little or no change over a substantial range of fluid environment variation shows.

It has been found that the device described in an initial Measurement period can be trimmed or adjusted in the following way, both of which Surfaces are in a clean condition without coating. The switches 132 and 134 are open. Switches 124 and 126 are closed and the probe is in a suitable fluid is immersed, which need not be the fluid of which Deposition tendency is to be measured. It becomes an initial position of the arm 120 of resistive divider 122 is selected and the fluid environment is varied. For this Adjustment process is the easiest way to change the fluid environment in that the Flow rate of fluid past the probe is changed, though one can also vary other properties of the fluid environment. The flow rate is varied by any conventional means (not shown) such as an adjustable one Control valve.

The temperature difference reproduced by the measuring device 156 is observed, while the fluid environment is varied.

If the temperature difference is at a certain position of the Arms 120 changes, while the fluid environment is varied, the arm is displaced, to change the relative heating input signals for the two heaters, and the fluid environment (fluid velocity) is again varied while one the measured temperature difference is observed. It is made through this trial method a position of the arm 120 found, 'The one from the measuring device 156 FeReits kUntdht fluctuates, or fluctuates minimally, when the fluidic environment is varied. This setting of the arm 120, with the two surface heating inputs be supplied in a certain ratio, is then used in all with this probe measurements carried out. In practice, this adjustment is completed after Manufacture of the probe is carried out in the factory, and the adjustment of the heat supply ratio can then be fixed or permanently built into the respective probe and forms a characteristic of the individual probe. If you z. B.

the heat supply ratio for the heaters of a given Probe determined according to the above method, fixed resistances can be used in the Heating circuits are installed to ensure this asymmetry compensation, and the variable resistive divider 122 can be omitted.

When you have adjusted the heat supply ratio in this way, will the temperature difference will generally not be zero, but the measuring device will 156 can be brought to zero by adjusting the potentiometer 150, to then increase signal #t - #r at the output of the differential amplifier 148 'or until the reading from meter 156 equals zero. Now is the probe including their circuits compensated and adjusted with regard to the zero point in a clean and coating-free condition of both surfaces. The switches 124 and 126 are opened, and, while the probe with its test and reference surfaces immersed in a liquid whose deposition tendency is to be measured coating switches 132 and 134 are closed to expose the test surface 70 to be heated via the heating device 74 to a temperature determined by the setting of the variable arm 136 of the secondary winding 138 of the transformer 140 is controlled will. the The temperature of the test surface 70 during the becomes so chosen that it is the temperature at which the desired detection and measurement of the deposition tendency of the liquid is to be carried out. If Desirably, the temperature of the test surface during the deposition period measured by additional thermocouples or thermistors (not shown in Fig. 6) as will be described later. The reference surface remains during the deposition period 68 near the temperature of the surrounding fluid around which the probe flows, and thus receives no deposits during the deposition period or when they are If deposits are received, these deposits are considerably less. Of course you can other methods of creating different deposits are used, as mentioned.

After the deposition period, the z. B. take one to four hours switches 132 and 134 are opened and switches 124 and 126 are opened closed again to supply the adjusted measurement heat. At that time will be no further settings made. The measured value of the measuring device 156 is noted, after the probe and associated circuitry have thermally stabilized. This stabilization period is needed, at least in part, because the Heat flow to the test and reference surfaces has been changed. The measured value of the meter relative to the measured value obtained in the initial measurement period, the was set to zero by means of the potentiometer 150 is a measure of the heat transfer properties of the test surface 70 for the heat transfer properties of the reference surface 68. The measured value is independent of the essentially identical fluid environments, in which the two surfaces are immersed, and is a measure of the deposits, that has been accumulated on the test surface 70 during the deposition period are essentially independent of the probe asymmetry.

In general, the duration of the deposit period and the condition increased deposition on the test surface (by increasing the temperature of the same by means of the heating device 74) selected so that on the reference surface 68 results in little or no deposit, while a considerably greater likelihood insists that debris accumulate on test surface 70. There are Many methods including those discussed above are available to make up a difference in the Deposition on the test surface and the reference surface during the deposition period to ensure. For example, the reference surface 68 may be prior to the deposition period be provided with a protective cover. Alternatively, the probe can be used before the second Measurement period are removed to the reference surface 68 of any debris that may have accumulated to clean up.

The circuit shown in Fig. 6, when used with the Probe of Figures 2-5 an apparatus of high sensitivity and good reliability, which is compensated for certain probe asymmetries. However, it is found that an additional compensation of the zero point of a probe of high sensitivity a further increase in this sensitivity has the consequence. Even with the one described above Adjustment of the heat input ratio can change the fluid environment of a person Very high sensitivity probe still has some fluctuation in the reading from the meter 156 cause. So can the probe described, although it is significantly better and is more sensitive than known arrangements, an undesirable sensitivity to Changes in the fluid environment when making measurements high precision and sensitivity is used. It will be understood that one high sensitivity to deposits in the methods and devices described is desirable because the chance to take corrective action before damage occurs to the earlier the scale is discovered, the greater it is and the smaller the amount of scale that can be detected.

An additional compensation for such changes in the Fluid environment can to a considerable extent in the in Fig.

7 can be achieved. With this arrangement, a Compensation caused by a signal, which the temperature difference between the reference surface and a third surface that is different heated or not heated or indirectly heated. In Fig.

7, a probe is shown schematically which is similar to the probe of FIG Figures 2-5 is. A probe jacket 160 has a reference surface 162, a test surface 164, a constantan-steel thermoelectric junction used to sense the reference temperature 166, a constantan-steel thermoelectric junction used to measure the test temperature 168 and reference and test heaters 170 and 172, all of these elements are so connected and work like the comparable elements of the probe's Figures 2-5. However, this probe has an additional thermoelectric junction 174 in a slightly and indirectly heated area 176 of the probe jacket 160, upstream from the test surface and from the reference surface.

The operation and control of heaters 170 and 172 this probe run exactly as with the probe of Figures 2-5 and the circuit of FIG. 6. The transition points 166 and 168 of the reference and test surfaces are with connected to a differential amplifier 180, the output of which is 5Yt -in a resistor-summing network 182 is combined with a selectively variable displacement signal derived from a potentiometer 184 is derived as well as in the circuit previously described.

In the arrangement of FIG. 7, however, the upstream Area 176 of the robe jacket, referred to as the fluid surrounding area can, a temperature relative to the temperature of the reference surface, which is of a thermoelectric junction 174 is sensed. The wires from the two Junctions 166 and 174 are used as inputs to a second differential amplifier 186 supplied. #R denotes the temperature at the reference surface, and #a denotes the sensed temperature at ambient fluid surface 176, the is at a different temperature from the reference surface, since the the former is only heated indirectly and the latter is heated directly. Hence shows the output of amplifier 186 differentiates the difference between these two heated surfaces, d. h.itr - ta 2 at what is referred to as the fluid environment signal can be. A function of this ambient fluid signal is used in the present case Compensation used.

The fluid environment signal is passed to an inverting amplifier 188 fed. The opposite polarity outputs of amplifiers 186 and 188 are fed to opposite ends of a resistive divider 190, which has a movable tap 192. The tap 192 is connected so that it provides an input to a resistor network 193, to which a second Input signal from the potentiometer 194 is supplied, which has a voltage of selectively variable size and polarity supplies, taken from a resistor 195 whose ends are connected to positive and negative potential sources. The output of the summing network 193 is matched with the output of the summing network 182 combined in a third summing network 196, and the output of the latter is fed to a meter 197 to obtain a compensated measured value of the temperature difference between the test surface and the reference surface.

The setting of potentiometer arm 192 for fluid environment compensation is determined empirically, with the surfaces in a clean, coating-free state is located. While measuring energy is supplied to the heating devices and the probe is immersed in a fluid which is not necessarily the fluid to be measured must be, but is preferably similar, the speed of the over flowing fluid of the normal value relative to the constant measuring speed considerably decreased. For example, the probe described can normally be used at fluid speeds measure on the order of 100 cm per second. This speed is at this empirical determination reduced by half, and a possible change the reading of the measuring device is noted. Then the speed drops to that normally is returned to the size used in the measurement, and the arm 192 is turned into an or shifted in another direction. The speed will be the same as previously reduced, e.g. B. to 50 cm per second, and the change in the measured value, the caused by the drop in speed at this new position of the arm 192 is noted. If the change in the measured value is greater than the previous change in the measured value, arm 192 is moved in the other direction. If they are lower, however, still is significant, arm 192 is moved again in the same direction. Again will the speed on the measurement condition returned, the reading is noted, the arm 192 is in one direction or the other in the above moves, and the speed is reduced again.

Again the change in the measured value is noted and with the previous one Change in measured value compared. This procedure is repeated until a setting is made of arm 192 is found to have a substantial change in fluid velocity causes little or no change in the measured value. Now is the probe compensated for the effects of speed changes, and this position of the arm 192 is fixed and remains constant during the subsequent measurement. balls necessary, the current position of the measuring device will return to zero adjusted by entering the summing network 193 by means of the potentiometer 194 introduces an adjustment signal, or potentiometer 184 can be used for this purpose in which case the potentiometer 194 is omitted.

The fluid environment is used to empirically adjust the arm 192 varies and the arm 192 is adjusted until a reading is obtained which is none Fluctuates as the fluid environment is varied. In fact, the empirical determination obtained in that a heat transfer property of the Fluid environment is varied. However, as mentioned earlier, one of the properties is which can be varied particularly easily, the flow velocity. It is hence this special fluid property, namely the flow velocity, which is varied in the empirical determination, although the determination also by Variation of other fluid environment properties can be carried out, which the Affect heat transfer properties of the fluid environment.

The thermal bridge described has a considerably increased Sensitivity to and is with regard to adverse influences of the fluid environment compensated. Furthermore, the operation of the bridge by using electrical Improve precision circuits and precisely regulated power supplies. However can be further improved by a control loop and stabilization the fluid environment can be achieved. Thus, as is also shown in FIG. 7, the Fluid environment signal #r - #a appearing at the output of amplifier 186 during a measuring period is generated, a differential amplifier 198 are fed, the second input signal is an adjustable voltage given by a potentiometer 199 is derived, its opposite ends with potentials opposite Polarity are applied. The amplifier 198 generates a feedback signal, representing the sampled fluid environment signal #r - #a to a control stage 200 to operate, which controls a flow valve 201, which more or less is opened to the flow rate of the fluid depending on Increase or decrease changes in the fluid environment. The nature of this control the fluid environment can vary in many different ways. So you can take place the adjustment of the speed according to the output signal of the amplifier 198 the viscosity, the temperature or other parameters which the heat transfer properties affect the fluid environment, adjust depending on the sensed Temperature difference between the heated reference surface 162 and the unheated one Surface 176 during the measurement period.

The compensation and adjustment circuits described above provide although for a compensation of the asymmetry of the probe and also for a compensation the zero point setting with clean probe surfaces with regard to a change the fluid environment, thereby improving the sensitivity of the measurement and at the same time obtain increased insensitivity to changes in the fluid environment will; however, it has been found that when e.g. B. the test surface has deposits, which produces a reading on the order of half the full scale, the Reading still fluctuates when the fluid environment changes, even if the Precipitation does not change. Thus, with very high sensitivities, the Apparatus a change in the fluid environment during a measurement to a change the measured temperature difference of the coated or partially coated probe. This effect of changing the fluid environment on a coated surface can be minimized by means of the circuit shown in FIG. Fig. 8 shows essentially the same probe as previously described with certain modifications the heating and measuring circuit. This figure includes a representation of both the previous one described zero point compensation with regard to environmental changes and also shows Circuitry for compensating for a deposit having a probe on the base of the product of the deposit measuring device - 2tr and one representing the fluid environment Measured value 4 / a flows around in the arrangement of FIG. 3, as indicated by arrow 203 the fluid is a stainless steel probe jacket 202 with a Test surface 204 and a reference surface 206 and an upstream Fluid surrounding surface 208. Thermoelectric junctions 210 and 212 are shown in FIG Spacer sleeves attached near the test surface or the reference surface. Heinz 'before directions 214 and 216 for the test surface and the reference surface, respectively, are near these surfaces arranged in the manner previously described. A third single thermoelectric Constantan wire to steel transition 215 is provided on the fluid surrounding surface 208, and a two-wire thermoelectric junction 217 containing chrome and aluminum wires 218a and 218b is attached near surface 208 for an absolute temperature measurement to deliver.

Constantan wires 220 and 221 from junctions 210 and 212 are added in an isothermal junction box 222 with usual electrical lines such as with Copper wires 223 and 224 connected, which input signals to a differential amplifier 226 feed, the output signal of which is the signal t> t r, which is proportional to the temperature difference at the test surface and the reference surface. the Line 221 connected to thermoelectric junction 212, and one Lines 227 from thermoelectric junction 215 are in junction box 222 connected to copper wires 224 and 228 to a second differential amplifier 229 supply input signals, the output signal of which is the temperature difference to the Transitions 212 and 215, denoted by size, 9va represents. The absolute Temperature at junction 217 is determined by thermoelectric wires 218a, 218b junction box 222 for connection to copper wires 232 and 233 first and second inputs fed to an amplifier 234. The output of this amplifier is added to the output signal of an amplifier 236 in a summing network 235, which receives its inputs via lines 237 and 238 from a reference thermistor 240, which is used to measure the temperature of the isothermal junction box 222, in which all thermoelectric wires are connected with common copper wires.

The output of summing network 235 is proportional to the absolute Temperature of the surrounding fluid surface 208 and is in a summing network 244 with the output signal "~ r of the amplifier 226 and with the output signal -r of amplifier 229 combined to network 244 via lines not shown are fed. The summing network 244 generates a signal O / which is the absolute Represents the temperature of the test surface. This temperature of the surface 204 is the sum of the temperature of the surface 208 and the two temperature differences between surfaces 208 and 206 and between surfaces 206 and 204.

The signal from the summing network 244 is in a control stage 246 for the test surface temperature with a predetermined test surface temperature compared, which are set in the control stage 246 by means of an adjusting knob 248 has been. The control stage 246 receives electrical energy via lines 250 and 251 and generates an output signal via a deposition period switch 253 to the test surface heater 214. Thus, only during the deposition period the energy supplied to the heater 214 in a closed loop controlled and held at a temperature selected by the adjustment knob 248.

Measurement energy is both heating devices 214 and 216 via the coupled Switches 254 and 256 are fed to opposite ends of a coil 258 are connected, which is activated via an adjustable tap 260, the is in turn connected to a tap 262 of a coil 264, which via input lines 250 and 251 is activated.

The tap 262 is set so that during the measurement period desired amount of heat is supplied. The arm 260 is operated in the same way as that has been described for the adjustment of the arm 120 of FIG. 6, set so that the selected ratio of the energy supplied to the two heaters for the purpose of Compensation of the probe asymmetry is guaranteed. The arm 260 can in the previously mentioned way set and fixed in the factory during the manufacture of the probe or its function is taken over by fixed resistors.

A correspondingly precise control is required for very precise measurements of the power supplies required. However, to an expensive scheme of high To avoid power for heating purposes, the temperature difference readings are regarding Voltage changes compensated. The temperature difference signal ~ tr is through divides a power signal W, r which is proportional to the square of the heater voltage is. The signal W is supplied by a squaring stage 270, which has an input from arm 262 and provides an output to a divider 272 which also receives the temperature difference signal ~ 9or and divides the latter by W to order generate the voltage compensated signal S1.

The power signal W is also fed to a second divider 274, which receives the signal ~ ßá from the amplifier 229 r a and divides this signal W, to provide the voltage compensated fluid environment signal FE. If the input voltage should fluctuate, those supplied to the test surface and the reference surface change Amounts of heat, and an additional factor is provided by dividers 272 and 2/4 with the temperature difference signals combined to compensate for the To achieve effects of such voltage fluctuations.

A zero point adjustment carried out on clean surfaces with regard to the fluid environment is used in conjunction with voltage dividers 190 and 192 of Fig. 7 described manner ensured. Thus, the fluid environment signal becomes FE from divider 274 via leads (not shown) to one end of a resistor 276 out, inverted in amplifier 278 and fed to the other end of the resistor. Tap 279 is set, like that in connection with tap 192 of FIG Fig. 6 has been described in order to minimize the change in the reading of the meter changing fluid environment. Thus, it becomes a fluid environment compensation signal k (FE) from arm 279 to the stress compensated scale signal S1 in one Summing network 280 added to a fluid environment compensated To get boiler stone signal S2.

An adjustment signal is obtained from the movable tap 282 of a resistor 284 removed, its opposite ends with positive and negative potentials be applied.

This adjustment signal is added to the signal S2 in the summing network 286, to generate an adjusted scale signal S3 which is a zero reading on measuring device 290 results.

To compensate for changes in the adjusted scale signal 53, which is sensitive to changes in the fluid environment in the event of scale formation Probe based, the fluid environment signal FE from the divider 274 becomes in one Multiplier 292 multiplied by the scale signal S3 to produce the signal S3 (FE) for an additional compensation. If no scale has occurred is, S3 is the same Zero, and this compensation is zero. The output of multiplier 292 is taken directly and through an inverting amplifier 294 fed to the opposite ends of a resistor 296, which is a slidable Has tap 298. The signal at tap 298 is fed to a summing network 300, to be added to the scale signal S3 at the output of the summing network 286 to become.

The combined signal S4 from the summing network 300 is the final one Signal which is fed to the measuring device 300 and which, with regard to voltage changes, Probe asymmetry, changes in the fluid environment causing the probe to become exposed to debris affected condition, and fluid environment changes that affect the clean Affect the probe, is compensated.

The arm 298 is adjusted empirically, in a manner such as they essentially in the adjustment of the arm 192 in connection with Figs. 7 and the arm 279 of Fig. 8, but the probe is in one with Deposits provided condition. One such with deposits State is equivalent to z. B.

a condition that has a reading equal to half of the full Scale of the measuring device results. The arm 298 is initially in a central position brought to the resistor 296, the standard measurement heat is supplied, and the speed of the fluid in which the probe is immersed is reduced to a preselected normal Measuring speed controlled. This speed is then reduced considerably, z. B. to about half of the original value, and a possible change to the Reading of the measuring device is noted. Then the arm 298 becomes in shifted to another position and the speed returned to its normal Value returned and then reduced again. The result of this change in speed Any change in the reading is noted again. If this change is less al is the first change noted, arm t9t3 is in the right direction been moved. If the second change is bigger, the arm is in the wrong one Direction has been moved. The arm 298 is then moved again, the speed is returned to normal and then decreased, and a third reading change is noted.

This trial method of adjusting the arm 298 continues, until a position of the arm 298 is reached. at which a big change in speed the fluid environment has little or no change in the reading caused. So that the arm 298 has been brought into a position in which the read measured values for sones with deposits with regard to possible changes the fluid environment are compensated. This makes it even more insensitive of the probe to changes in the fluid environment.

It can be seen that the methods and devices described do not Measurement of temperatures (but only of temperature differences) or of flow rates require and that improved measurement of deposits and increased sensitivity is achieved through various features and compensation measures. First, creates the use of the thermal bridge described is a significant improvement in terms of independence from the fluid environment. Secondly the thermal asymmetry is compensated for by adjusting the heat supply. Third, there is compensation for the fluid environment for the zero point adjustment intended. Fourth, there is compensation for scale and fluid environment intended for a condition with scale formation. Fifth is a scheme the fluid environment provided. Each of the aforementioned features can have two to five on its own or in conjunction with one or more of the other characteristics can be used to improve the operation of the thermal bridge described.

The measuring device can be calibrated in degrees of temperature difference or by dividing the temperature difference through the heat flux density occurring during the measurement period Divided into watts per cm2, the measuring device can measure in degrees cm2 / watt, i.e. in units the thermal resistance.

FIG. 14 illustrates the exemplary application of the probe of FIG FIGS. 2-5 for a cooling water system 340, whose scale formation tendency was measured shall be. For such a typical application of the probe, water is drawn from the cooling system withdrawn through conduit 342 and while it is through heater 344 flows, heated in order to raise its temperature to a value at which the deposition tendency should be measured. This temperature can e.g. B.

the temperature of the cooling water near a surface of the heat exchanger elements be in contact with the cooling water and are cooled by this. Generally is the formation of deposits on such hot heat exchanger surfaces biggest. The heated water from the system flows through a manifold valve 346 and from there via a line 348 to a line 352. The heated water flows then over the long straight line 352 through a T-fitting 354, one arm with the line 352 is connected. The T-fitting has an output arm 356 through which Water from line 352 is discharged into a container 358, from where it is either removed from the system or recirculated into the system. The other The end of the T-fitting is used to attach a probe like the probe shown in Figures 2-5 take up, with their jacket through the T-fitting through into the long straight Pipe 352 is inserted between the T-fitting and valve 346. The probe housing 106 (see also Fig. 6) is removably attached to the free end of the T-fitting and stands in front of this. The entire probe can be connected to the Fluid system used and removed from this.

The valve 346 is also provided with a source 360 of fresh water, such as tap water, for example, and can be switched between a first (deposit) position, in which it allows water to flow from heater 344 to conduit 348 and blocking the flow of fresh water from the source 360, and a second (Measuring) position can be switched in which water from the fresh water source 360 to line 348 while the water flow from the heater 344 is blocked.

The probe is inserted into the T-fitting with the valve 346 itself is in its measurement position and blocks flow from heater 344 and passing a flow of relatively cool water from fresh water source 360. The various adjustment processes as described in connection with FIG have been attached to the probe during an initial measurement period carried out, the two probe heating devices with a selected measurement heat activated to generate a reference surface and test surface temperature, which is higher than the temperature of the surrounding fluid. After this initial Adjustment in the measuring period, the valve 34fi is brought into its deposit position, to interrupt the flow of fresh water and water from the heater 344 to the probe. The heater 344 is set so that it brings the water to be measured from the cooling system to the desired temperature, namely the temperature at which the deposition tendency is to be measured. That heated water flows past the probe, which is now in its deposition period is located, to the container 358. In the deposition period of the probe, the measurement heat away from the heater, and only the reference surface heater is activated as described in connection with FIGS. 10, 11 or 12. As already mentioned, this deposition period can last from one to to have several hours. At the end of this period the probe circuit will return switched to the measuring state.

The deposit heating power is removed, the measuring power is supplied for the purpose of heating both the reference surface and the test surface, and that Valve 346 is again actuated to cut off flow from the cooling water system and fresh water at the temperature of the source 360, which is of the order of magnitude can range from 60 OF to 70 OF, via the probe and into the container 356. This cyclical switchover between the deposit and measurement state, i.e. the switchover the probe heater circuits and valve 346 can be done manually. For a long-term working method, simple repetitive switching functions can be used for these an automatic clock control can be used.

While the probe reverts to its measurement state, elne second measurement taken, a the reading of the meter or recorder 360, which with the probe circuit for playback or recording of the deposit measurement is connected produces an indication of the fouling propensity of the cooling water system. It should be noted that in the application shown, the probe in the to be measured Fluid, namely the water of the cooling system 340, only during the deposition periods works, while in the measuring periods another fluid, namely tap water is used. The tap water is cooler than the heated water from the cooling system 340, and therefore a greater thermal flux can flow over the test and reference surfaces be directed to achieve increased sensitivity.

The measuring period fluid can be chosen to have other properties which are desired for the measurement period.

The desired lower fluid temperature during the measurement period can alternatively be provided in such a way that the heating device 344 only is turned off without using a second source of fluid; in this If so, the valve 346 is omitted.

With an automatic operation of the system described one can z. B. take a measurement every hour or two, so that a large number of measurements can be made and averaged and changes in the measured values can be made more accurate can be determined. Such a change then means a change in the deposition tendency of the observed fluid system.

In many systems, the formation of deposits occurs very internally and harmful effects can only appear after a very long period of time. However, the described invention can be used to provide effective monitoring the deposition tendency to carry out over such long periods of time and well before such changes in relation to the measured values become harmful to the deposits Discovering deposits, which will then be sufficient to take remedial action to take. The detected deposit changes can be in a tax system can be used, which automatically triggers an alarm and also sufficient Take remedial action early, such as adding additional ones automatically Inhibitors to the system.

To compensate for changes in the fluid environment between perform the test surface and the reference surface during a measurement, the probe can be provided with two reference surfaces which are symmetrical in the same axial distances upstream and downstream from the test surface are. The heating powers supplied to the two reference surfaces are the same, and the measured temperatures of the two reference surfaces supplied heating power are the same, and the measured temperatures of the two reference surfaces will be averaged to with regard to possible axial asymmetries of the fluid environment compensate and around with regard to a possible axial gradient of the fluid temperature to compensate.

In one way of applying the invention described, the accumulation of deposits on cooled surfaces measured. In such an application will be the reference surface and the test surface are only cooled during the measurement period instead of heated. The fluid environment can be a hot geothermal fluid, thereby removing heat from the fluid environment to the cooled test and reference surfaces flows.

It can be seen that a reversal of the direction of the heat flow -in a Application for a cooled surface - in the thermal bridge of Fig. 1, where box 18 is a heat sink and box 28 is a heat source, none of the essential properties of the thermal bridge changed, such as one Reversal of the polarity of the voltage on an electrical bridge, its basic mode of operation does not change.

Claims (22)

A method for detecting the inclination of a fluid environment, depositing deposits on a surface immersed in it, characterized in that that a test surface is exposed to the fluid environment, that both a reference surface as well as the test surface fluid environments are set up that a known Have ratio of heat flow parameters, and that the heat transfers between the surfaces and their respective fluid environments are compared will. 2. The method according to claim 1, characterized in that the comparing step implies that the temperature difference between the test surface and the reference surface is measured and that these surfaces have a first and a second Wärznestrbmung are supplied, which are set in terms of their difference so that the Change in temperature difference when changing fluid environments to which the test and reference surfaces are exposed, is degraded. 3. The method according to claim 1, characterized in that measure be taken to a predetermined ratio of thermal properties ensure the specified surfaces before the first-mentioned process step, And that said comparing step includes the thermal properties of said surfaces are compared to determine whether the thermal Properties of the test surface are due to deposits on the first tooth Flidum environment have changed or not. 4. The method according to claim 3, characterized in that causes that said surfaces substantially prior to the first-mentioned step have the same thermal properties. 5. The method according to claim 1, characterized in that said The comparison step includes the heat fluxes of the test surface and the reference surface and the temperatures of these surfaces are compared with one another will. 6. The method according to claim 5, characterized in that the Test surface and the heat flows supplied to the reference surface are set so that daM a change in the temperature comparison result when the fluid environment changes, to which the surfaces are exposed is kept as low as possible. 7. The method according to claim 1, characterized in that the comparing step includes that different heat flows from the test surface and the Reference surface are supplied to have equal temperatures on these surfaces to maintain, and that the respective heat flows supplied to the surfaces be compared with each other. 8. The method according to claim 1, characterized in that the reference surface of the first-mentioned step is exposed to said first fluid environment and that the tendency of the former fluid environment to form deposits the test surface is varied versus the tendency of the fluid environment to form of deposits on the reference surface during the former step. 9. The method according to claim 8, characterized in that the step the variation of the deposition tendency includes that different temperatures be provided on the test surface and on the reference surface. 10. The method according to claim 1, characterized in that the reference surface during the first-mentioned step against deposits from the first-mentioned fluid environment is protected. 11. The method according to claim 1, characterized in that the latter Fluid environments are substantially identical to and different from one another the first-mentioned fluid environment. 12. The method according to claim 1, d a d u r c h g e k e n n z e i c h n e t that a first heat flow of the mentioned test surface during the first mentioned Step is fed to increase the deposition tendency, and that second heat flows both the test surface and the reference surface during the comparison step are fed. 12. The method according to claim 1, characterized in that the deposition conditions varies at the interface between the test surface and the fluid environment to change the rate of deposition on the tea surface, and that the last-mentioned step is carried out before the comparison step. 14. The method according to claim 1, characterized in that the comparing step includes that the temperature difference of the surfaces is measured that one Heat transfer property of the latter fluid environments is measured and that the measured temperature difference in accordance with the measured heat transfer property is compensated. 15. The method according to claim 14, characterized in that that the compensating step includes that with the measured temperature difference a quantity is combined which is a function of the product of the measured temperature difference Representative of the size and one of the measured heat transfer property representing second size is. 16. gate direction for detecting the inclination of a fluid environment depositing deposits on a surface immersed in it, characterized in that that a thermal bridge is provided to indicate the heat transfer properties a first heat transfer element exposed to a fluid environment, that the bridge is a heat transfer reference element, heating means for transferring Heat on the first element and the reference element in a predetermined ratio, Means for exposing said elements to a first or second fluid environment, having a known relationship of heat transfer properties and indicating means has to display the relative temperatures of the elements in the first or second flu'.dum environment. 17. The device according to claim 16, characterized in that the first and second fluid environments have the same heat transfer properties. 18. The device according to claim 16, characterized in that the first and second fluid environments consist of a single fluid environment, the both elements are exposed. 19. The device according to claim 16, characterized in that adjusting means provided for setting the ratio of the amounts of heat supplied to the elements are. 20. The device according to claim 16, characterized in that the Heating means have means for differential heating of the elements for the purpose of compensation of differences in the heat transfer properties of the elements, if these are in the same state. 21. The device according to claim 16, characterized in that thermo-electrical Material is provided which connects the elements together that the display means have a first and a second wire to display the relative temperatures, which are connected to the first and second element, and that the wires from one Material that is thermo-electrically different from the one connecting the elements Material is. 22. Method of detecting the accumulation of debris on a Surface that is exposed to a deposit-prone fluid, thereby characterized in that the surface and a reference surface share a common fluid are exposed and that the heat transfers between the common fluid and each of the surfaces can be compared with each other.