Method and a device for detecting an abnormality of a heat exchanger and the use of such a device

Abstract

A method and a device for detecting an abnormality of a heat exchanger exchanging heat between a first fluid flow flowing in a conduit and a second fluid flow flowing along a flow path, said conduit and said flow path each having an inlet and an outlet, whereby the method comprises the steps of establishing at least one parameter representative of the temperature conditions of the heat exchanger, establishing a second fluid inlet temperature, establishing a parameter indicative of expected heat exchange between the heat exchanger and the second fluid, processing the heat exchanger temperature, the second fluid temperature and the parameter indicative of expected heat exchange for establishing an estimated second fluid outlet temperature, and employing the estimated second fluid outlet temperature for evaluating the heat exchange between the first and second fluids by comparing the estimated second fluid outlet temperature, or a parameter derived therefrom, with a reference value.

1 . A method for detecting an abnormality of a heat exchanger exchanging heat between a first fluid flow flowing in a conduit and a second fluid flow flowing along a flow path, said conduit and said flow path each having an inlet and an outlet, said method comprising the steps of: 
 establishing at least one parameter representative of the temperature conditions of the heat exchanger;    establishing a second fluid inlet temperature;    establishing a parameter indicative of expected heat exchange between the heat exchanger and the second fluid;    establishing an estimated second fluid outlet temperature; and    employing the estimated second fluid outlet temperature for evaluating the heat exchange between the first and second fluids by comparing the estimated second fluid outlet temperature, or a parameter derived therefrom, with a reference value,    wherein the estimated second fluid outlet temperature is established from at least one parameter representative of the temperature conditions of the head exchanger, the second fluid inlet temperature and the parameter being indicative of an expected heat exchange.    
     
     
         2 . The method according to  claim 1 , wherein the reference value is a predetermined second fluid outlet temperature.  
     
     
         3 . The method according to  claim 1 , wherein the estimated second fluid outlet temperature is used for establishing a second heat rate of the second fluid for evaluating the energy balance of the second heat rate of the second fluid compared to a first heat rate of the first fluid.  
     
     
         4 . The method according to  claim 3 , wherein the second rate of heat flow of the second fluid is established by establishing an estimate of a second fluid mass flow and a specific enthalpy change of the second fluid across the heat exchanger based on the estimated second fluid outlet temperature and the second fluid inlet temperature, and the condensation pressure.  
     
     
         5 . The method according to  claim 3 , wherein the first rate of heat flow is established by establishing a first fluid mass flow and a specific enthalpy change of the first fluid across the heat exchanger based on parameters representative for first fluid inlet and outlet temperatures.  
     
     
         6 . The method according to  claim 3 , wherein a residual is established as difference between the first heat rate and the second heat rate.  
     
     
         7 . The method according to  claim 2 , wherein a residual is established as difference between the estimated and predetermined second fluid outlet temperature.  
     
     
         8 . The method according to  claim 6 , wherein an abnormality indicator is provided by means of the residual, the abnormality indicator being provided according to the formula:  
       
         
           
             
               
                 
                   
                     
                       S 
                       
                         μ 
                         , 
                         i 
                       
                     
                     = 
                     
                       { 
                       
                         
                           
                             
                               
                                 
                                   S 
                                   
                                     μ 
                                     , 
                                     
                                       i 
                                       - 
                                       1 
                                     
                                   
                                 
                                 + 
                                 
                                   s 
                                   i 
                                 
                               
                               , 
                               
                                 
                                   
                                     when 
                                     ⁢ 
                                     
                                         
                                     
                                     ⁢ 
                                     
                                       S 
                                       
                                         μ 
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                                           i 
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                                   + 
                                   
                                     s 
                                     
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                                       i 
                                     
                                   
                                 
                                 > 
                                 0 
                               
                             
                           
                         
                         
                           
                             
                               0 
                               , 
                               
                                 
                                   
                                     when 
                                     ⁢ 
                                     
                                         
                                     
                                     ⁢ 
                                     
                                       S 
                                       
                                         μ 
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                                           i 
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                                 ≤ 
                                 0 
                               
                             
                           
                         
                       
                     
                   
                 
                 
                   
                     ( 
                     20 
                     ) 
                   
                 
               
             
           
         
         where s μ,i  is calculated according to the following equation:  
         
           
             
               
                 
                   
                     
                       
                         s 
                         
                           μ 
                           , 
                           i 
                         
                       
                       = 
                       
                         
                           c 
                           1 
                         
                         ⁡ 
                         
                           ( 
                           
                             
                               r 
                               i 
                             
                             - 
                             
                               
                                 
                                   μ 
                                   0 
                                 
                                 + 
                                 μ 
                               
                               2 
                             
                           
                           ) 
                         
                       
                     
                   
                   
                     
                       ( 
                       21 
                       ) 
                     
                   
                 
               
             
           
         
         where  
         r i : residual  
         c 1 : proportionality constant  
         μ 0 : first sensibility value  
         μ: second sensibility value.  
       
     
     
         9 . A heat exchanger abnormality detection device for a heat exchanger exchanging heat between a first fluid in a conduit and a second fluid in a flow path the device comprising: 
 a first estimator estimating at least one parameter representative of the temperature conditions of the heat exchanger;    a first intermediate memory means storing at least one parameter representative of the temperature conditions of the heat exchanger;    a temperature sensor measuring the second fluid inlet temperature;    a second intermediate memory means storing the second fluid inlet temperature, a second estimator establishing a parameter indicative of expected heat exchange between the heat exchanger and the second fluid;    a third intermediate memory means storing the parameter indicative of expected heat exchange;    a processor establishing an estimated second fluid outlet temperature; and    a comparator comparing the estimated second fluid outlet temperature, or a parameter established on basis thereof, with a reference value;    wherein the estimated second fluid outlet temperature is based on said at least one parameter representative of the temperature conditions of the heat exchanger, said second fluid inlet temperature, from the first and second intermediate memory means, respectively, and the parameter indicative of expected heat exchange from the third intermediate memory means.    
     
     
         10 . The detection device according to  claim 9 , wherein the detection device further comprises memory means for storing at least one parameter from the processor.  
     
     
         11 . The detection device according to  claim 9 , wherein the heat exchanger is part of a vapour-compression refrigeration or heat pump system comprising a compressor, a condenser, an expansion device, and an evaporator interconnected by conduits providing a flow circuit for the first fluid, said first fluid being a refrigerant.  
     
     
         12 . The detection device according to  claim 11 , wherein the heat exchanger is the condenser.  
     
     
         13 . The detection device according to  claim 9 , wherein the second fluid is air.  
     
     
         14 . The detection device according to  claim 11 , wherein that the condenser is part of a refrigerated display cabinet positioned within a building and the condenser is positioned outside the building.  
     
     
         15 . The detection device according to  claim 9 , wherein the detection device is used for detecting fouling of the heat exchanger and/or detecting insufficient flow of the second fluid.