Method and Device for Determining Fouling in a Heat Exchanger

Abstract

A device and method for increasing accuracy in the determination of fouling in a heat exchanger in which heat is transferred from a first medium to a second medium, wherein a value for a variable characterizing the fouling is determined from a value for a first variable influenced by the fouling and a value for a second variable, where the second variable compensates for a change in the first variable caused by a change in flow of the first and/or second mediums through the heat exchanger, where the first variable can be a thermal transmission resistance, a thermal transmittance or a thermal transmission coefficient, where the first and second variable are determined from values measured totemperaturesr and flows of the first and second mediums without using material properties of the first and second mediums and structural properties of the heat exchanger when determining the first and second variables.

1 .- 16 . 
     
     
         17 . A method for determining fouling in a heat exchanger, in which heat from a first medium is transferred to a second medium, the method comprising:
 determining a value for a variable characterizing the fouling from a value for a first variable affected by the fouling and from a value of a second variable; and   compensating for a change in the first variable caused by a change in a flow of at least one of (i) the first medium and (ii) the second medium through the heat exchanger at least in part by the second variable, the first variable being one of a thermal transmission resistance, a thermal transmittance and a thermal transmission coefficient, the first variable and the second variable being determined from measured values of a plurality of the measured variables comprising (i) temperatures of the first medium and the second medium at an inlet and at an outlet of the heat exchanger and (ii) flows of the first medium and the second medium through the heat exchanger, and the determination of the first and the second variable occurring without using material properties of the first medium and the second medium and structural properties of the heat exchanger.   
     
     
         18 . A method for determining fouling in a heat exchanger, in which heat is transferred from a first medium to a second medium, the method comprising:
 determining a value for a variable characterizing the fouling from a value for a first variable affected by the fouling and from a value of a second variable; and   compensating for a change in the first variable caused by a change in a flow of at least one of (i) the first medium and (ii) the second medium through the heat exchanger at least in part by the second variable, the first variable being a flow resistance, and the first variable and the second variable being determined from measured values of a plurality of measured variables comprising (i) pressures of the first medium and the second medium at an inlet and at an outlet of the heat exchanger and (ii) flows of the first medium and the second medium through the heat exchanger, and the determination of the first and the second variable occurring without utilizing material properties of the first medium and the second medium and structural properties of the heat exchanger.   
     
     
         19 . The method as claimed in  claim 17 , wherein at a time of a change in flow, the value of the second variable is changed such that the value of the variable characterizing the fouling remains constant. 
     
     
         20 . The method as claimed in  claim 18 , wherein at a time of a change in flow, the value of the second variable is changed such that the value of the variable characterizing the fouling remains constant. 
     
     
         21 . The method as claimed in  claim 19 , wherein after an initial startup and after a cleaning operation of the heat exchanger an initial value of the first variable is determined in each case and the value of the second variable is set to an initial value which corresponds to the initial value of the first variable. 
     
     
         22 . The method as claimed in  claim 17 , wherein a function is defined which in each case assigns a value for the second variable to a value for a flow of at least one of the first medium and the second medium. 
     
     
         23 . The method as claimed in  claim 22 , wherein the function is determined in a time interval after an initial startup or after cleaning the heat exchanger of fouling. 
     
     
         24 . The method as claimed in  claim 22 , wherein the function is formed by a regression of measured values of the flow and associated values of the second variable in the time interval. 
     
     
         25 . The method as claimed in  claim 23 , wherein the function is formed by a regression, in particular a linear or a 3D regression, of measured values of the flow and associated values of the second variable in the time interval. 
     
     
         26 . The method as claimed in  claim 24 , wherein the regression comprises a linear or a 3D regression. 
     
     
         27 . The method as claimed in  claim 25 , wherein the regression comprises a linear or a 3D regression. 
     
     
         28 . The method as claimed in  claim 17 , wherein value ranges for the flow are defined, to each of which a value for the second variable is assigned. 
     
     
         29 . The method as claimed in  claim 28 , wherein assignments of the values of the second variable to the flow are determined in a time interval after an initial startup or after cleaning the heat exchanger of fouling. 
     
     
         30 . The method as claimed in  claim 17 , wherein a characteristic curve for a relationship between the second variable and the flow of one of the two media is determined; and
 wherein, for the determination of the characteristic curve, a characteristic curve of a mathematical derivation of the first variable after the flow of the medium is initially determined and the characteristic curve initially obtained is subsequently again integrated with respect to the flow of the medium.   
     
     
         31 . The method as claimed in  claim 17 , wherein a first characteristic curve for a relationship between the second variable and the flow of the first medium and a second characteristic curve for a relationship between the second variable and the flow of the second medium are simultaneously determined; and
 wherein for the determination of the characteristic curves for each of the first and second media a characteristic curve of a mathematical derivation of the first variable after the flow of the respective first and second medium are each determined and the characteristic curves initially obtained are subsequently again integrated with respect to the flow of the respective medium.   
     
     
         32 . The method as claimed in  claim 17 , wherein the variable characterizing the fouling is a thermal transmission resistance. 
     
     
         33 . The method as claimed in one  claim 17 , wherein only relative changes in the variable characterizing the fouling, the first variable and the second variable are determined. 
     
     
         34 . A device for determining fouling in a heat exchanger, in which heat from a first medium is transferred to a second medium, the device comprising:
 a further device for receiving measured values or variables derived therefrom of the heat exchanger; and   an evaluation device which is configured to determine from the received measured values or the derived variables a value for a variable characterizing the fouling from a value for a first variable affected by the fouling and from a value of a second variable;   wherein a change in the first variable caused by a change in a flow of at least one of (i) the first medium and (ii) the second medium through the heat exchanger is compensated for at least in part by the second variable; and   wherein the first variable and the second variable are determined from measured values of a plurality of measured variables comprising (i) temperatures of the first medium and the second medium at an inlet and at an outlet of the heat exchanger and (ii) flows of the first medium and the second medium through the heat exchanger, and the determination of the first and the second variable occurring without utilizing material properties of the first medium and the second medium and structural properties of the heat exchanger being utilized.   
     
     
         35 . The device for determining fouling in a heat exchanger, in which heat is transferred from a first medium to a second medium, the device comprising:
 a further device for receiving measured values or variables derived therefrom of the heat exchanger; and   an evaluation device which is configured to determine from the measured values or the derived variables a value for a variable characterizing the fouling from a value for a first variable affected by the fouling and from a value of a second variable;   wherein a change in the first variable caused by a change in a flow of at least one of (i) the first medium and (ii) the second medium through the heat exchanger is compensated for at least in part by the second variable;   wherein the first variable is a flow resistance;   wherein the first variable and the second variable are determined from measured values of a plurality of measured variables comprising (i) pressures of the first medium and the second medium at an inlet and at an outlet of the heat exchanger and (ii) flows of the first medium and of the second medium through the heat exchanger, and the determination of the first and the second variables occurring without utilizing material properties of the first medium and the second medium and structural properties of the heat exchanger.   
     
     
         36 . A computer program comprising instructions which, when executed by a processor of a computer, cause the computer to execute the method as claimed in  claim 17 . 
     
     
         37 . A computer program comprising instructions which, when executed by a processor of a computer, cause the computer to execute the method as claimed in  claim 18 .