Method and apparatus for controlling total dissolved solids in a liquid circulation system

Abstract

A method and apparatus for controlling the total dissolved solids in a liquid circulation system having a sump to which liquid is supplied from a liquid source measures the liquid level in the sump, calculates the average evaporation rate of the liquid over time based on that measurement and also calculates the total dissolved solids level in the liquid based on sump volume, the measured liquid level in the sump, the calculated evaporation rate and the total dissolved solids content of the liquid from the liquid source and adds supply liquid to the liquid circulating system when the calculated total dissolved solids content in the liquid in the system attains a predetermined level.

What is claimed is: 
     
         1 . A method for controlling the total dissolved solids in a liquid circulation system using a liquid supply having a known, measured, or estimated total dissolved solids content and including a sump, said method comprising the steps of;
 a) measuring the liquid level in the sump at least periodically over time;   b) calculating at least periodically the average liquid evaporation rate over time based on the liquid level measurements;   c) calculating at least periodically the total dissolved solids level in the liquid based on the sump volume, the measured calculated liquid level in the sump, the evaporation rate and the total dissolved solids content of the supply liquid;   d) draining a portion of the sump volume when the calculated tds reaches a predetermined limit;   e) adding supply liquid to the liquid circulation system to replenish the sump volume and reduce the tds and to maintain the sump level between maximum and minimum levels;   f) recalculating the totals dissolved solids content in the liquid circulatory system after the addition of supply liquid based on the quantity of supply liquid added; and   g) repeating steps a) through e) over time during operation of the system.   
     
     
         2 . The method as defined in  claim 1  wherein steps a); b) and c) are performed continuously. 
     
     
         3 . The method as defined in  claim 1  or  claim 2  wherein the step of measuring the liquid level is performed using a liquid level sensor. 
     
     
         4 . The method as defined in  claim 3  wherein said liquid level sensor is a pressure transducer. 
     
     
         5 . The method as defined in  claim 1  or  claim 2  wherein the liquid circulation system is an evaporative cooling system and the method includes the step of calculating the cooling load performance of the evaporative cooling system based on the calculated evaporation rate and the heat of evaporation of the liquid. 
     
     
         6 . The method as defined in  claim 5  including the step of comparing the calculated cooling load performance with the predicted air side cooling performances of the evaporative cooler based on the values of the enthalpy of the surrounding ambient air and the enthalpy of the air leaving the evaporative cooler. 
     
     
         7 . The method as defined in  claim 6  including the step of measuring the enthalpy of the ambient air and leaving air. 
     
     
         8 . The method as defined in  claim 1  or  claim 2  including the step of measuring the amount of liquid supplied to the system in step e) and supplying at least one liquid treatment chemical to the liquid circulating system based on that measurement. 
     
     
         9 . The method as defined in  claim 1  or  claim 2  including the step of measuring the amount of liquid supplied to the system in step e) and using that measurement and the content calculated total dissolved solids to supply liquid chemical treatment to the liquid in the system. 
     
     
         10 . The method as defined in  claim 1  or  claim 2  including the step of periodically draining the sump near its bottom to flush precipitated solids there from. 
     
     
         11 . A liquid circulation system connected to a source of liquid for circulation therein, in which total dissolved solids in the liquid circulating in the system is controlled, said system comprising:
 a) a liquid circulation path in the system including a sump for liquid;   b) means for measuring the liquid level in the sump, at least periodically, while the system is in operation;   c) controller means for calculating, at least periodically the average evaporation rate over time based on the liquid measurements in the sump; and for calculating the total dissolved solids level in the liquid based on the sump volume, the liquid level in the sump, the calculated average evaporation rates and the total dissolved solids content of the supply liquid;   d) means responsive to said controller for draining of portion of the sump volume when the calculated total dissolved solids reaches a predetermined level   e) means responsive to said controller for supplying liquid from said liquid source to the system in order to reduce the level of total dissolved solids and to maintain sump levels between predetermine minimum and maximum levels; and   e) said controller being adapted to recalculate the total dissolved solids content in the liquid circulating in the system after the addition of liquid to the system based on the quantity of liquid added and the total dissolved content calculated before the liquid additive.   
     
     
         12 . The system as defined in  claim 11  wherein said means for measuring the liquid level in the sump is a liquid level sensor. 
     
     
         13 . The system as defined in  claim 11  wherein said means for measuring the liquid level in the sump is a pressure transducer. 
     
     
         14 . The system as defined in  claim 11  wherein said liquid circulation system includes an evaporative cooling section and said controller means is adapted to calculate the cooling load performance of the evaporative cooling section based on the calculated liquid evaporation rate and the heat of evaporation of the liquid. 
     
     
         15 . The system as defined in  claim 14  wherein said controller means is adapted to compare the calculated cooling load performances of the evaporative cooling section with the predicted air side cooling performance of the evaporative cooler section based on the values of the enthalpy of the surrounding ambient air and the enthalpy of the air leaving the evaporative cooler section. 
     
     
         16 . The system as defined in  claim 14  including means for measuring the enthalpy of the ambient air and for measuring the enthalpy of the air leaving the evaporative cooler. 
     
     
         17 . The system as defined in  claim 11  including means for measuring the amount of liquid supplied to the system in response to the calculated total dissolved solids content of the liquid and supplying at least one liquid treatment chemical to the liquid circulating system based on that measurement. 
     
     
         18 . The system as defined in  claim 11  including means for measuring the amount of liquid supplied to the system in response to the calculated total dissolved solids content and for using that measurement and the calculated total dissolved solids content to supply liquid chemical treatment to the liquid in the system. 
     
     
         19 . The system as defined in  claim 11  including means responsive to said controller for periodically draining the sump near its bottom to flush precipitated solids therefrom. 
     
     
         20 . The system as defined in  claim 13  wherein said means for draining the sump is responsive to the controller means calculation of a total dissolved solids content in the liquid that is higher than the total dissolved solids content at which liquid is added to the system. 
     
     
         21 . The system as defined in  claim 11 ,  12 ,  13 ,  14 ,  15 ,  16 ,  17 ,  18 ,  19  or  20  wherein said means for measuring the liquid level in the sump operates continuously and said controller continuously calculates the average evaporation rate and total dissolved solids level of the liquid. 
     
     
         22 . A method for controlling the total dissolved solids in a liquid circulation system using a liquid supply having a known measured or estimated total dissolved solids content and including a sump, said method comprising the steps of;
 a) measuring the liquid level in the sump at least periodically over time;   b) calculating at least periodically the average liquid evaporation rate over time based on the liquid level measurements;   c) calculating at least periodically the total dissolved solids level in the liquid based on the sump volume, the measured calculated liquid level in the sump, the evaporation rate and the total dissolved solids content of the supply liquid;   d) draining a portion of the sump periodically when the calculated tds reaches a predetermined limit; and   e) adding supply liquid to the liquid circulation system to maintain a predetermined liquid level in the sump and reduce sump tds.   
     
     
         23 . A liquid circulation system connected to a source of liquid for circulation therein, in which total dissolved solids in the liquid circulating in the system is controlled, said system comprising:
 a) a liquid circulation path in the system including a sump for liquid;   b) means for measuring the liquid level in the sump, at least periodically, while the system is in operation;   c) controller means for calculating, at least periodically the average evaporation rate over time based on the liquid measurements in the sump; and for calculating the total dissolved solids level in the liquid based on the sump volume, the liquid level in the sump, the calculated average evaporation rates and the total dissolved solids content of the supply liquid; and   d) means responsive to controller to partially drain sump when the calculated tds reaches a predetermined level; and   e) means responsive to said controller for supplying liquid from said liquid source to the system when the calculated total dissolved solids content attains a predetermined level.