Some devices use liquids to perform various functions. Consider, for example, a heat exchanger 100 such as the one illustrated in
Impurities and contaminants in the liquid may form on surfaces within the heat exchanger 100. This “fouling layer” 102 might include organic, inorganic, and/or biological material. For example, organic deposits might include polymers and inorganic materials might include Calcite.
Eventually, the fouling layer 102 may grow thick enough to substantially decrease performance of the heat exchanger 100 (e.g., the energy efficiency of the device may be substantially reduced). By this point, however, removing the relatively thick fouling layer 102 can be a time consuming and expensive process. For example, a factory might need to be shut down while a massive chemical cleaning of the heat exchanger is performed.
According to some embodiments, a first capacitive element may be provided for a surface where a fouling layer is to be detected. A second capacitive element may also be provided, and a capacitance between the first and second capacitive elements may be used to detect formation of the fouling layer.
Some embodiments include: means for measuring a capacitance between a first capacitive element associated with a surface and a second capacitive element; and means for determining that a fouling layer has formed on the surface based at least in part on the measured capacitance.
Other embodiments provide a surface where a fouling layer is to be detected, and a thermal device may provide heat proximate to the surface. A detector may detect a condition associated with the surface, and formation of the fouling layer may be determined based at least in part on the condition.
Yet other embodiments comprise: means for providing thermal energy proximate to a surface where a fouling layer is to be detected; means for detecting a condition associated with the surface; means for determining that the fouling layer has formed based at least on part on the condition.
The first capacitive element 210 might comprise, for example, a first conducting plate mounted onto and parallel to the surface 110. Note that a bonding or insulating layer (not illustrated in
As the fouling layer 102 grows on the surface 110, it may also grow on the first capacitive element 210. This may be especially true if the thermal characteristics of the surface 110 and the first capacitive element 210 are similar (e.g., such that they will both be at similar temperatures).
According to some embodiments, a capacitance between the first and second capacitive elements 210, 220 is used to detect formation of the fouling layer 102 (e.g., that the fouling layer 102 has reached a pre-determined thickness). Note that the fouling layer 102 may have different dielectric characteristics as compared to a fluid that is normally present between the elements 210, 220 and, therefore, the capacitance between the elements 210, 220 will change as deposits accumulate (e.g., the elements 210, 220 might act as two plates of a capacitor). By monitoring the capacitance between the elements 210, 220 the formation of the fouling layer 102 can be detected.
In this and other embodiments described herein, a scaled down device may more accurately detect formation of the fouling layer 102. For example, a very small gap between the elements 210, 220 may result in a more accurate sensor (e.g., because a small layer 102 will have a greater proportional impact on the capacitance). According to some embodiments, the elements 210, 220 may be associated with Micro-ElectroMechanical System (MEMS) devices and/or silicon micromachining technology. Such a sensor may detect a fouling layer 102 having a thickness of 1-10 micrometers or less. By sensing the fouling layer 102 at such an early stage the efficiency and maintenance costs associated with the system 200 may be improved.
Although a single pair of elements 210, 220 are illustrated in
According to some embodiments, the elements 410, 420 comprise two parallel conductors by wet etching into a silicon wafer. Moreover, the elements 410, 420 may be isolated from each other, and a thin silicon oxide may be grown thermally to electrically isolate the silicon plates 410, 420 from surrounding fluid.
As the fouling layer 102 grows on the surface 110, it may also grow on the first capacitive element 410 and/or the second capacitive element 420. This may be especially true if the thermal characteristics of the surface 110 and the elements 410, 420 are similar (e.g., such that they will both be at similar temperatures). Moreover, the elements 410, 420 may need to be relatively short so that the portions of the elements 410, 420 farthest from the surface 110 will be at a temperature similar to the temperature of the surface 110 (and, therefore, will accumulate the fouling layer 102 at a similar rate).
According to some embodiments, a capacitance between the first and second capacitive elements 410, 420 is used to detect formation of the fouling layer 102. Note that the fouling layer 102 may have different dielectric characteristics as compared to a fluid that is normally present between the elements 410, 420 and, therefore, the capacitance between the elements 410, 420 will change as deposits accumulate. By monitoring the capacitance between the elements 410, 420 the formation of the fouling layer 102 can be detected.
Note that this configuration may result in mostly fringe fields away from the plane of the elements 510, 520 (e.g., into and out of the page of
Referring to
It may be determined if the fouling layer 102 has formed (e.g., is of at least a certain thickness) based at least in part on the detected condition. In particular, note that the fouling layer 102 may act as an insulator that reduces the amount of heat that may be transferred from the surface to the liquid. As a result, increasing the thickness of the fouling layer 102 will cause the surface 110 to retain more heat from the pulse generated by the thermal device 610. Thus, at Step 706 it is determined if the temperature is above a pre-determined threshold. If so, an indication that the fouling layer 102 has formed on the surface 110 is output at Step 708. The process may then be repeated (e.g., rapid pulses of heat may be applied the surface and analyzed to reduce the impact of moving liquid in the system 600).
Note that the presence of moving liquid in the system 600 may make it difficult to accurately determine small temperature changes.
Refer to
It may be determined if the fouling layer 102 has formed (e.g., is of at least a certain thickness) based at least on part on the detected condition. In particular, note that the fouling layer 102 may act as thermal load that absorbs some of the heat received from the thermal device 810. As a result, increasing the thickness of the fouling layer 102 will cause the surface 110 to retain less heat from the pulse generated by the thermal device 810. Thus, at Step 906 it is determined if the temperature is below a pre-determined threshold. If so, an indication that the fouling layer 102 has formed on the surface 110 is output at Step 908.
Note that conditions other than temperature changes might be monitored to detect a fouling layer.
Refer to
At Step 1104, a condition associated with the surface 110 is detected. For example, the vibration detector 1020 might measure information associated with a resonant frequency and/or a damping behavior of the surface 110.
It may be determined if the fouling layer 102 has formed (e.g., is of at least a certain thickness) based at least on part on the detected condition. In particular, note that the fouling layer 102 may act alter the resonant frequency and/or damping behavior of the surface 110. Thus, at Step 1106 it is determined if certain vibration-related conditions are met. If so, an indication that the fouling layer 102 has formed on the surface 110 is output at Step 1108.
By detecting a fouling layer at an early stage of build up in accordance with any of the embodiments described herein, a maintenance frequency associated with a heat exchange or other types of devices may be reduce. Moreover, the need for factory shut downs may be avoided and/or the energy efficiency of such devices may be improved.
The following illustrates various additional embodiments of the invention. These do not constitute a definition of all possible embodiments, and those skilled in the art will understand that the present invention is applicable to many other embodiments. Further, although the following embodiments are briefly described for clarity, those skilled in the art will understand how to make any changes, if necessary, to the above-described apparatus and methods to accommodate these and other embodiments and applications.
Several approaches to early fouling detection have been provided, and any of the embodiments described here may be used together with other approaches. For example, a sensor may use both capacitance detection (e.g., as described with respect to
The present invention has been described in terms of several embodiments solely for the purpose of illustration. Persons skilled in the art will recognize from this description that the invention is not limited to the embodiments described, but may be practiced with modifications and alterations limited only by the spirit and scope of the appended claims.
Number | Name | Date | Kind |
---|---|---|---|
3665301 | Maltby | May 1972 | A |
3913378 | Hausler | Oct 1975 | A |
4147620 | Artiano et al. | Apr 1979 | A |
4485450 | Characklis et al. | Nov 1984 | A |
4766553 | Kaya et al. | Aug 1988 | A |
4912332 | Siebel et al. | Mar 1990 | A |
4942364 | Nishijima et al. | Jul 1990 | A |
5185533 | Banks et al. | Feb 1993 | A |
5619193 | Doherty et al. | Apr 1997 | A |
5985454 | McMordie et al. | Nov 1999 | A |
6023070 | Wetegrove et al. | Feb 2000 | A |
6094981 | Hochstein | Aug 2000 | A |
6241383 | Feller et al. | Jun 2001 | B1 |
6312644 | Moriarty et al. | Nov 2001 | B1 |
6790664 | Bailey et al. | Sep 2004 | B2 |
7017419 | Pedersen et al. | Mar 2006 | B2 |
7030982 | Woollam et al. | Apr 2006 | B1 |
7400267 | Doherty et al. | Jul 2008 | B1 |
20030183536 | Eden | Oct 2003 | A1 |
20060061485 | Doherty et al. | Mar 2006 | A1 |
20060268273 | Woollam et al. | Nov 2006 | A1 |
20070113644 | Manaka et al. | May 2007 | A1 |
Number | Date | Country |
---|---|---|
0873921 | Apr 1998 | EP |
60135749 | Jul 1985 | JP |
61027445 | Feb 1986 | JP |
9236397 | Sep 1997 | JP |
2003287396 | Oct 2003 | JP |
WO 0228517 | Apr 2002 | WO |
Number | Date | Country | |
---|---|---|---|
20080041139 A1 | Feb 2008 | US |