Patent Application
20160216052
The present invention relates to a method of monitoring and operating a heat exchanger for fuels containing carbon.
Priority is claimed on Japanese Patent Application No. 2013-218494, filed Oct. 21, 2013, the content of which is incorporated herein by reference.
In various types of plant, such as gas turbine power generation plants, nuclear power generation plants or chemical plants, a monitoring device acquires and monitors the state quantities of the plants, such as temperature and pressure, in order to monitor whether the plants are operating normally. That is, the monitoring device measures the state quantities of a plurality of monitoring items that are monitoring targets at predetermined time intervals. The monitoring device calculates and normalizes the average and distribution of the state quantities for each monitoring item. The monitoring device calculates the correlation between the state quantities of each monitoring item, thereby calculating the Mahalanobis distance. The monitoring device determines that there are signs of abnormality in a plant, when the Mahalanobis distance exceeds a preset threshold. A plant operation state monitoring method using such a Mahalanobis distance is disclosed in PTL 1.
A technique of preventing adhesion of foreign matter to a heat transfer pipe of a heat exchanger of a coal gasification combined power generation system is disclosed in PTL 2. In a heat exchanger for fuels containing carbon, such as a heat exchanger of the coal gasification combined power generation system illustrated in PTL 2, soot may adhere to a heat transfer face of the heat exchanger depending on the type of gas. If an abnormality in such a heat exchanger for fuels containing carbon is not found at an early stage, adhered soot is sintered, and it becomes difficult to remove the soot. Therefore, it is preferable to monitor an abnormality in the heat exchanger for fuels containing carbon and find the abnormality at an early stage.
[PTL 1] Japanese Unexamined Patent Application Publication No. 2010-181188
[PTL 2] Japanese Unexamined Patent Application Publication No. 2001-254086
A technique of calculating the Mahalanobis distance on the basis of state quantities in a plurality of places in a circumferential direction of a rotating shaft of a gas turbine, thereby appropriately monitoring a plant operation state, is disclosed in PTL 1. Meanwhile, a configuration for finding an abnormality in the heat exchanger for fuels containing carbon at an early stage is not disclosed in PTL 1.
An object of the invention is to provide a method of monitoring and operating a heat exchanger for fuels containing carbon that allows finding of an abnormality in the heat exchanger for fuels containing carbon at an early stage.
A first aspect of the invention is a method of monitoring a heat exchanger for fuels containing carbon. The method includes a process of calculating the Mahalanobis distance on the basis of temperatures in a plurality of locations in a direction of flow on a primary side of a heat exchanger of a heat exchanger for fuels containing carbon; and a process of determining the presence of an abnormality on the heat transfer face by the Mahalanobis distance.
A second aspect of the invention is the method of monitoring a heat exchanger for fuels containing carbon described in the first aspect. In the process of calculating the Mahalanobis distance, the Mahalanobis distance is calculated on the basis of at least one of a differential pressure between an inlet and an outlet on the primary side, a flow rate on the primary side, a plurality of temperatures in a direction of flow on a secondary side of the heat exchanger, a flow rate on the secondary side, and the like, in addition to the temperatures in the plurality of locations in the direction of flow on the primary side of the heat exchanger.
A third aspect of the invention is a method of operating a heat exchanger for fuels containing carbon. The operating method of a third aspect of the invention includes a process of modifying the operating conditions of a removing device included in the heat exchanger when it is determined that there is an abnormality in the heat transfer face by the method of monitoring a heat exchanger for fuels containing carbon described in the first aspect or the second aspect.
According to the above aspects, by calculating the Mahalanobis distance on the basis of the temperatures in the plurality of locations in the direction of flow on the primary side, it is possible to detect that the efficiency of heat exchange has degraded due to blocking of a portion of the heat transfer face. Accordingly, an abnormality in the heat exchanger for fuels containing carbon can be determined at an early stage.
Hereinafter, a first embodiment of the invention will be described with reference to
In addition, as state quantities for monitoring the heat exchanger 1 for fuels containing carbon, for example, there are temperatures (an inlet temperature, an outlet temperature, and the like of a heat exchanger 2) in a plurality of locations in a direction G of flow on a primary side of the heat exchanger 2, a differential pressure between an inlet and an outlet in the direction G of flow on the primary side, a flow rate on the primary side, a plurality of temperatures in a direction W of flow on a secondary side, the flow rate of a heat exchange medium within a heat transfer pipe 4, and the like. The primary side of the heat exchanger 2 is a high-temperature side. That is, in the present embodiment, the primary side of the heat exchanger 2 is a side to which fuel flows. The secondary side of the heat exchanger 2 is a low-temperature side. That is, in the present embodiment, the secondary side of the heat exchanger 2 is a side to which the heat exchange medium flows. These state quantities are shown as monitoring target data.
The heat exchanger 1 for fuels containing carbon that is a monitoring target includes the heat exchanger 2, a fuel flow passage 3, the heat transfer pipe 4, and a soot removing device 5. Fuel is supplied to the inside of the heat exchanger 2 via the fuel flow passage 3. Examples of the fuel include fuel gas and powder fuel. The heat transfer pipe 4 passes through the heat exchanger 2. A heat transfer face 6 is constituted by the heat transfer pipe 4. In the heat transfer face 6, heat exchange is performed between the fuel that flows from the fuel flow passage 3 to the heat exchanger 2 and the heat exchange medium that flows through the heat transfer pipe 4. Examples of the heat exchange medium include water and the like. The soot removing device 5 removes soot adhering to the heat transfer face 6 constituted of the heat transfer pipe 4. The soot is soot produced from carbon included in the fuel. As the soot removing device 5, an vibration type soot removing device that applies vibration to the heat transfer face 6, a hard ball falling type soot removing device that drops hard balls to the heat transfer face 6, a jet type soot removing device (for example, a soot blower) that jets compressed gas (nitrogen, steam, or the like) to the heat transfer face 6, or the like can be used.
The abnormality monitoring device 10 monitors the state of the heat exchanger 1 for fuels containing carbon. In the present embodiment, the abnormality monitoring device 10 monitors the state of one heat exchanger 1 for fuels containing carbon. However, the operation state of a plurality of the heat exchangers 1 for fuels containing carbon may be monitored. The abnormality monitoring device 10 is, for example, a computer, and is configured to include an input/output unit (I/O) 11, a processing unit 12, and a storage unit 13. The abnormality monitoring device 10 may be configured using a so-called personal computer, or may be configured combining a central processing unit (CPU) and a memory.
The processing unit 12 receives the state quantities of the heat exchanger 1 for fuels containing carbon from various types of state quantity detecting means (sensors). The various types of state quantity detecting means are attached to the heat exchanger 1 for fuels containing carbon via the input/output unit 11. The various types of state quantity detecting means periodically acquire corresponding state quantities at predetermined time intervals from starting. The various types of state quantity detecting means input the state quantities to the processing unit 12 via the input/output unit 11.
A monitoring target data group showing the state quantities of the heat exchanger 1 for fuels containing carbon is sent to the processing unit 12 of the abnormality monitoring device 10 in the form of electrical signals. The processing unit 12 is constituted of, for example, a CPU. The processing unit 12 reads and interprets an instruction string referred to as a program (computer program) that is present on the storage unit 13 in order. The processing unit 12 moves or processes data according to the result of the interpretation.
The processing unit 12 related to other embodiments may be realized by exclusive hardware.
The processing unit 12 related to other embodiments may execute the processing procedure of the monitoring and operating method related to the present embodiment according to the following procedure. A computer program for realizing the functions of the processing unit 12 is recorded on computer-readable recording media that are not temporary. The processing unit 12 makes a computer system read and execute the computer program recorded on the recording media. The “computer system” herein includes an OS, or hardware, such as a peripheral device.
The “computer-readable recording media that are not temporary” mean portable media, such as flexible disks, magnetic-optical disks, ROMs, or CD-ROMs, or storage devices, such as hard disks, built in the computer system. Moreover, the “computer-readable recording media” include recording media that dynamically hold computer programs in a short time, like the Internet, or communication lines, such as telephone lines, in a case where the computer programs are transmitted via the communication lines. The “computer readable recording media” include recording media that hold the computer programs for a predetermined period of time, like a volatile memory inside the computer system serving as a server or a client that receives the computer programs. Additionally, the above computer programs may be provided for realizing some of the aforementioned functions. The above computer programs may be programs that can realize the aforementioned functions in combination with the computer programs already recorded in the computer system.
The method of monitoring and operating the heat exchanger 1 for fuels containing carbon related to the present embodiment can be realized by executing computer programs, which are prepared in advance, using personal computers, or computers, such as workstations. The computer programs can be distributed via communication lines, such as the Internet. Additionally, the computer programs are recorded on the computer-readable recording media, such as hard disks, flexible disks (FDs), CD-ROMs, MOs, or DVDs, or may be executed by being read from the recording mediums by computers.
The processing unit 12 performs a monitoring target data acquisition process A, a Mahalanobis distance calculation process B, a comparison process C, an abnormality determination process D, and an operating condition modification process E in respective calculating units, as illustrated in
The monitoring target data acquisition process A is a process of acquiring monitoring target data showing the state quantities of the heat exchanger 1 for fuels containing carbon. The Mahalanobis distance calculation process B is a process of calculating the Mahalanobis distance on the basis of the acquired monitoring target data. The comparison process C is a process of comparing the calculated Mahalanobis distance with a threshold. The abnormality determination process D is a process of determining the presence of an abnormality by a comparison result between the Mahalanobis distance and the threshold. The operating condition modification process E is a process of modifying the operating conditions of the soot removing device 5 on the basis of an abnormality determination result.
The concept of the Mahalanobis distance is illustrated in
The above-described Mahalanobis's unit space can be obtained according to the following items that are determined in advance in the present embodiment.
(1) The abnormality monitoring device 10 calculates the Mahalanobis's unit space on the basis of monitoring target data showing the state quantities of the heat exchanger 1 for fuels containing carbon in a past period obtained by tracing back to the past from a point of time when the states of the heat exchanger 1 for fuels containing carbon are evaluated to a point of time before a predetermined period.
(2) The abnormality monitoring device 10 predicts the future state of the heat exchanger 1 for fuels containing carbon on the basis of monitoring target data showing state quantities at the point of time when the state of the heat exchanger 1 for fuels containing carbon is evaluated. The abnormality monitoring device 10 calculates the Mahalanobis's unit space on the basis of the predicted value.
(3) The abnormality monitoring device 10 predicts the future state of the heat exchanger 1 for fuels containing carbon on the basis of the monitoring target data showing the state quantities at the point of time when the state of the heat exchanger 1 for fuels containing carbon is evaluated, and a control target set value set at the point of time when the heat exchanger 1 for fuels containing carbon is started. The abnormality monitoring device 10 calculates the Mahalanobis's unit space on the basis of the predicted value.
In addition, the abnormality monitoring device 10 converts multi-dimension data into one-dimensional data using the Mahalanobis distance when determining whether or not the heat exchanger 1 for fuels containing carbon is normal using the Mahalanobis distance. The abnormality monitoring device 10 evaluates the difference between the unit space and a signal space by the Mahalanobis distance. The signal space is data to be compared with the unit space, for example, state quantities when the state of the heat exchanger 1 for fuels containing carbon is evaluated. In the present embodiment, the abnormality monitoring device 10 obtains the Mahalanobis distance of the signal space using a matrix made from the unit space. An abnormality in the data is expressed by this.
A control panel 14 that is output means is connected to the input/output unit 11 of the abnormality monitoring device 10. The control panel 14 is provided with a display 14D and input means 14C. The display 14D is display means. The input means 14C is means for inputting a command to the abnormality monitoring device 10. The storage unit 13 of the abnormality monitoring device 10 is constituted of, for example, a volatile memory, such as a random access memory (RAM), a nonvolatile memory, such as a read-only memory (ROM), or a readable-only storage medium, such as a hard disk drive, a magnetic-optical disk device, or a CD-ROM, or is constituted by combining these. Computer programs, data, and the like for realizing the method of monitoring and operating the heat exchanger 1 for fuels containing carbon related to the present embodiment are stored in the storage unit 13. The processing unit 12 realizes the method of monitoring and operating the heat exchanger 1 for fuels containing carbon related to the present embodiment, using these computer programs and data. The processing unit 12 controls the operation of the heat exchanger 1 for fuels containing carbon, using these computer programs and data. In addition, in another embodiment, the storage unit 13 may be provided outside the abnormality monitoring device 10, and the abnormality monitoring device 10 may be configured so as to be capable of making an access to the storage unit 13 via a communication line.
Here, calculating formulas for calculating the general Mahalanobis distance D will be described.
The number of items of a plurality of state quantities showing the state of the heat exchanger 1 for fuels containing carbon is defined as u. u is an integer that is equal to or greater than 2. State quantities of u items are defined as X1 to Xu, respectively. The state quantities X1 to Xu is shown by the monitoring target data. The abnormality monitoring device 10 collects a total of v (2 or more) state quantities X1 to Xu for each item, in the operation state of the heat exchanger 1 for fuels containing carbon that serves as a reference. For example, when sixty state quantities are acquired for each item, v=60 is established. The state quantities X1 to Xu of a j-th item of the respective items collected in the operation state is defined as X1j to Xuj. j takes any one value (integer) of 1 to v, and means that the number of state quantities of each item is v. That is, the abnormality monitoring device 10 collects the state quantities X11 to Xuv.
The abnormality monitoring device 10 obtains an average value Mi and a standard deviation σi (the variations degree of reference data) of the state quantities X11 to Xuv for each item according to Formula (1) and Formula (2). i is the number of items (the number of state quantities, integer). Here, i is set to 1 to u and indicates a value corresponding to the state quantities X1 to Xu. Here, the standard deviation is a positive square root of an expected value of values obtained by squaring differences between state quantities and an average value thereof.
The aforementioned average value Mi and standard deviation σi are state quantities showing features. The abnormality monitoring device 10 converts the state quantities X11 to Xuv into standardized state quantities x11 to xuv, according to the following Formula (3), using the average value Mi and the standard deviation σi that are calculated. That is, the abnormality monitoring device 10 converts the state quantities Xij of the heat exchanger 1 for fuels containing carbon into a random variable xij with an average value of 0 and a standard deviation of 1. In addition, in the following Formula (3), j takes any one value (integer) of 1 to v. This means that the number of state quantities for each item is v.
x
ij=(Xij−Mi)/σi (3)
In order to analyze variable quantities with data that is standardized to an average of 0 and a variance of 1, the abnormality monitoring device 10 specifies the state quantities X11 to Xuv. That is, the abnormality monitoring device 10 defines a covariance matrix (correlation matrix) R showing the relevance between the variable quantities, and an inverse matrix R−1 of the covariance matrix (correlation matrix), according to the following Formula (4). In addition, in the following Formula (4), k is the number of items (the number of state quantities). That is, k is equal to u. Additionally, i and p show values in each state quantity, and take a value of 1 to u here.
The abnormality monitoring device 10 obtains the Mahalanobis distance D, which is a state quantity showing a feature, on the basis of the following Formula (5) after such calculation processing. In addition, in Formula (5), j takes any one value (integer) of 1 to v. This means that the number of state quantities for each item is v. Additionally, k is the number of items (the number of state quantities). That is, k is equal to u. Additionally a11 to akk are coefficients of the inverse matrix R−1 of the covariance matrix R illustrated in the above-described Formula (4).
The Mahalanobis distance D is reference data. The average value of the Mahalanobis distance D of the unit space becomes 1. In a state where the state quantities of the heat exchanger 1 for fuels containing carbon are normal, the Mahalanobis distance D approximately falls within 3 or less. However, in a state where the state quantities of the heat exchanger 1 for fuels containing carbon are abnormal, the value of the Mahalanobis distance D becomes approximately greater than 3. In this way, the Mahalanobis distance D has a property in which the value thereof becomes greater according to the degree (the degree of separation from the unit space) of an abnormality in the state quantities of the heat exchanger 1 for fuels containing carbon.
The abnormality monitoring device 10 related to the present embodiment uses at least the temperatures in the plurality of locations in the direction G of flow on the primary side of the heat exchanger 2, as a parameter for calculating the Mahalanobis distance D.
If soot is accumulated in the heat transfer face 6 of the heat exchanger 2, the efficiency of heat exchange in the heat transfer face 6 degrades. Therefore, on the primary side of the heat exchanger 2, the temperature of fuel does not easily drops. In this case, if a temperature difference between the inlet and the outlet on the primary side of the heat exchanger 2 in normality is compared with a temperature difference between the inlet and the outlet on the primary side of the heat exchanger 2 in abnormality, the temperature difference in abnormality become small. Therefore, the abnormality monitoring device 10 can calculate the Mahalanobis distance D on the basis of the temperatures in the plurality of locations in the direction G of flow of the heat transfer face 6, thereby detecting that the efficiency of heat exchange degrades due to the blocking of a portion of the heat transfer face 6. Since soot is accumulated in the heat transfer face 6, a state where the efficiency of heat exchange degrades is generated before the differential pressure between the inlet and the outlet on the primary side of the heat exchanger 2 rises (becomes remarkable in the last stage of the blocking of the heat transfer face 6). Therefore, according to the method of monitoring and operating the heat exchanger 1 for fuels containing carbon related to the present embodiment, an abnormality in the heat exchanger 1 for fuels containing carbon can be determined before a rise in the differential pressure between the inlet and the outlet on the primary side becomes remarkable.
A procedure of the method of monitoring and operating the heat exchanger 1 for fuels containing carbon related to the present embodiment will be described. The method of monitoring and operating the heat exchanger 1 for fuels containing carbon related to the present embodiment is realized by the processing unit 12 of the abnormality monitoring device 10 illustrated in
In Step S1, the processing unit 12 acquires monitoring target data showing state quantities from the heat exchanger 1 for fuels containing carbon in a current state quantity acquisition period. The state quantities, for example, are periodically acquired at predetermined time intervals from various types of sensors attached to the heat exchanger 1 for fuels containing carbon. The state quantities are stored in the storage unit 13 of the abnormality monitoring device 10.
In Step S2, the processing unit 12 calculates the Mahalanobis distance according to the above Formulas, regarding the state quantities stored in the storage unit 13.
In Step S3, the processing unit 12 compares a threshold that is set in advance with the Mahalanobis distance obtained in the previous Step S2. The processing unit 12 determines whether or not the Mahalanobis distance has exceeded the threshold. The processing unit 12 determines that the heat exchanger “abnormal” in case of YES in which the Mahalanobis distance has exceeded the threshold, on the basis of the determination result in Step S3 (Step S4). The processing unit 12 determines that the heat exchanger “normal” in case of NO in which the Mahalanobis distance does not the threshold (Step S5).
When the processing unit 12 determines that the heat exchanger 1 for fuels containing carbon is abnormal on the basis of the Mahalanobis distance, in Step S6, the abnormality monitoring device 10 modifies the operating conditions of the soot removing device 5. Accordingly, the abnormality monitoring device 10 can remove soot using the soot removing device 5 before soot is sintered and blocking occurs, in the heat exchanger 1 for fuels containing carbon. Methods of modifying the operating conditions of the soot removing device 5 include, for example, increasing frequency in use or the like. When the frequency in use is increased for the modification of the operating conditions, it is preferable that the abnormality monitoring device 10 returns the operating conditions when it is determined that the heat exchanger 1 for fuels containing carbon is normal in Step S4 after the operating conditions of the soot removing device 5 are modified.
As described above, the more the separation from the unit space, the Mahalanobis distance shows a greater value according to the degree of abnormality. The Mahalanobis distance D is reference data. The average value of the Mahalanobis distance D of the unit space becomes 1. In a state where the state quantities of the heat exchanger 1 for fuels containing carbon are normal, the Mahalanobis distance D approximately falls within 3 or less. Therefore, for example, the threshold can be appropriately set to a greater value than the maximum value of the unit space. Additionally, as the threshold, a set value obtained by taking into consideration characteristics specific to the heat exchanger 1 for fuels containing carbon, the manufacture variations of the heat exchanger 1 for fuels containing carbon, or the like can be used.
As described in details above, according to the method of monitoring and operating the heat exchanger 1 for fuels containing carbon illustrated in the present embodiment, at least the temperatures in the plurality of locations in the direction G of flow on the primary side of the heat exchanger 2 are used for the calculation of the Mahalanobis distance.
If soot is accumulated in the heat transfer face 6 of the heat exchanger 2, the efficiency of heat exchange in the heat transfer face 6 degrades. Therefore, in the heat transfer face 6 of the heat exchanger 2, the temperature of fuel does not easily drops. In this case, the difference between the temperature of the heat transfer face 6 of the heat exchanger 2 in normality and the temperature of the heat transfer face 6 of the heat exchanger 2 in abnormality becomes greater downstream in the direction G of flow than upstream in the direction G of flow. Therefore, the abnormality monitoring device 10 can calculate the Mahalanobis distance D on the basis of the temperatures in the plurality of locations in the direction G of flow on the primary side, thereby detecting that the efficiency of heat exchange degrades due to the blocking of a portion of the heat transfer face 6. Since soot is accumulated in the heat transfer face 6, a state where the efficiency of heat exchange degrades is generated before the differential pressure between the inlet and the outlet on the primary side of the heat exchanger 2 rises and the blocking of the heat transfer face 6 becomes remarkable. Therefore, according to the method of monitoring and operating the heat exchanger 1 for fuels containing carbon related to the present embodiment, the abnormality monitoring device 10 can determine an abnormality in the heat exchanger 1 for fuels containing carbon before a rise in the differential pressure between the inlet and the outlet on the primary side becomes remarkable.
Additionally, according to the method of monitoring and operating the heat exchanger 1 for fuels containing carbon illustrated in the present embodiment, the abnormality monitoring device 10 calculates the Mahalanobis distance, using the differential pressure between the inlet and the outlet in the direction G of flow on the primary side, the flow rate on the primary side, the plurality of temperatures in the direction W of flow on the secondary side, the flow rate of the heat exchange medium within the heat transfer pipe 4, and the like, in addition to the temperatures in the plurality of locations in the direction G of flow on the primary side of the heat exchanger 2. Accordingly, the abnormality monitoring device 10 can precisely determine the state of the heat exchanger 1 for fuels containing carbon. In addition, in the present embodiment, a case where the abnormality monitoring device 10 calculates the Mahalanobis distance, using the differential pressure between the inlet and the outlet in the direction G of flow on the primary side, the flow rate on the primary side, the plurality of temperatures in the direction W of flow on the secondary side, the flow rate of the heat exchange medium within the heat transfer pipe 4, and the like has been described. However, the invention is not limited thereto. For example, in another embodiment, the abnormality monitoring device 10 may calculate the Mahalanobis distance, using at least one of the differential pressure between the inlet and the outlet in the direction G of flow on the primary side, the flow rate on the primary side, the plurality of temperatures in the direction W of flow on the secondary side, the flow rate of the heat exchange medium within the heat transfer pipe 4, and the like, in addition to the temperatures in the plurality of locations in the direction G of flow on the primary side of the heat exchanger 2.
A second embodiment of the invention will be described with reference to
That is, as illustrated in
Specifically, the processing unit 20 performs a monitoring target data acquisition process A, a Mahalanobis distance calculation process B′, a comparison process C′, an abnormality determination process D, and an operating condition modification process E in respective calculating units, as illustrated in
Accordingly, the abnormality monitoring device 10 can determine whether abnormality occurs at a certain location in the direction G of flow on the primary side of the heat exchanger 2, in the abnormality determination process D. Additionally, accordingly, the abnormality monitoring device 10 can modify the operating conditions so that the soot removing device 5 is intensively operated in a place where abnormality is generated in the heat exchanger 2, the operating condition modification process E.
In the method of monitoring and operating the heat exchanger 1 for fuels containing carbon illustrated in the second embodiment, the abnormality monitoring device 10 also uses at least the temperatures in the plurality of locations in the direction G of flow on the primary side of the heat exchanger 2, similar to the first embodiment. Therefore, according to the method of monitoring and operating the heat exchanger 1 for fuels containing carbon related to the present embodiment, the abnormality monitoring device 10 can determine an abnormality in the heat exchanger 1 for fuels containing carbon before a rise in the differential pressure between the inlet and the outlet on the primary side becomes remarkable.
Additionally, according to the method of monitoring and operating the heat exchanger 1 for fuels containing carbon illustrated in the present embodiment, the abnormality monitoring device 10, similar to the first embodiment, calculates the Mahalanobis distance, using the differential pressure between the inlet and the outlet in the direction G of flow on the primary side, the flow rate on the primary side, the plurality of temperatures in the direction W of flow on the secondary side, the flow rate of the heat exchange medium within the heat transfer pipe 4, and the like, in addition to the temperatures in the plurality of locations in the direction G of flow on the primary side of the heat exchanger 2. Accordingly, the abnormality monitoring device 10 can precisely determine the state of the heat exchanger 1 for fuels containing carbon.
Although the embodiments of the invention have been described above in detail with reference to the drawings, specific configuration is not limited to the embodiments, and design changes or the like are also included without departing from the scope of the invention.
Therefore, by calculating the Mahalanobis distance on the basis of the temperatures in the plurality of locations in the direction of flow on the primary side, it is possible to detect that the efficiency of heat exchange degrades due to the blocking of a portion of the heat transfer face. Accordingly, an abnormality in the heat exchanger for fuels containing carbon can be determined in an early stage.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-218494 | Oct 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/077311 | 10/14/2014 | WO | 00 |
