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December 10, 2006, 05:00 
Vessel Residence Time Distribution Help

#1 
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Can someone please step me through how to calculate the residence time of water in a settling tank? I have read about creating an additional variable RTD and analysing the spatial distribution at the outlet, but I do not know how to do this.
Any help would be greatly appreciated. Thanks Davo 

December 10, 2006, 09:58 
Re: Vessel Residence Time Distribution Help

#2 
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Help manual: Look at the user cel and user fortran examples. One is for an RTD.


December 11, 2006, 06:39 
Re: Vessel Residence Time Distribution Help

#3 
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I have modified tutorial 1 Static Mixer Transient and added a Additional Variable, but am unsure if the source point and boundary conditions are setup correctly. Here is the CCL, can someone point me in the correct direction please as I am pretty sure the Source Point 1 is not correct, it is meant to be 1 [s/s] but I cannot get it to accept that.
Thanks Davo FLOW: DOMAINefault Domain Coord Frame = Coord 0 Domain Type = Fluid Fluids List = Water Location = Assembly BOUNDARY:in1 Boundary Type = INLET Location = in1 BOUNDARY CONDITIONS: ADDITIONAL VARIABLE:advRTD1 Additional Variable Value = 0 [s] Option = Value END FLOW REGIME: Option = Subsonic END HEAT TRANSFER: Option = Static Temperature Static Temperature = 315 [K] END MASS AND MOMENTUM: Normal Speed = 2 [m s^1] Option = Normal Speed END TURBULENCE: Option = Medium Intensity and Eddy Viscosity Ratio END END END BOUNDARY:in2 Boundary Type = INLET Location = in2 BOUNDARY CONDITIONS: ADDITIONAL VARIABLE:advRTD1 Additional Variable Value = 0 [s] Option = Value END FLOW REGIME: Option = Subsonic END HEAT TRANSFER: Option = Static Temperature Static Temperature = 285 [K] END MASS AND MOMENTUM: Normal Speed = 2 [m s^1] Option = Normal Speed END TURBULENCE: Option = Medium Intensity and Eddy Viscosity Ratio END END END BOUNDARYut Boundary Type = OUTLET Location = out BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Option = Average Static Pressure Relative Pressure = 0 [Pa] END PRESSURE AVERAGING: Option = Average Over Whole Outlet END END END BOUNDARYefault Domain Default Boundary Type = WALL Location = F1.B1.P3,F2.B1.P3,F4.B1.P3,F5.B1.P3,F6.B1.P3,F8.B1 .P3 BOUNDARY CONDITIONS: HEAT TRANSFER: Option = Adiabatic END WALL INFLUENCE ON FLOW: Option = No Slip END WALL ROUGHNESS: Option = Smooth Wall END END END DOMAIN MODELS: BUOYANCY MODEL: Option = Non Buoyant END DOMAIN MOTION: Option = Stationary END MESH DEFORMATION: Option = None END REFERENCE PRESSURE: Reference Pressure = 1 [atm] END END FLUID MODELS: ADDITIONAL VARIABLE:advRTD1 Option = Transport Equation END COMBUSTION MODEL: Option = None END HEAT TRANSFER MODEL: Option = Thermal Energy END THERMAL RADIATION MODEL: Option = None END TURBULENCE MODEL: Option = k epsilon END TURBULENT WALL FUNCTIONS: Option = Scalable END END INITIALISATION: Option = Automatic INITIAL CONDITIONS: Velocity Type = Cartesian ADDITIONAL VARIABLE:advRTD1 Additional Variable Value = 0 [s] Option = Automatic with Value END CARTESIAN VELOCITY COMPONENTS: Option = Automatic with Value U = 0 [m s^1] V = 0 [m s^1] W = 0 [m s^1] END K: Option = Automatic with Value END STATIC PRESSURE: Option = Automatic with Value Relative Pressure = 101325 [Pa] END TEMPERATURE: Option = Automatic with Value Temperature = 300 [K] END END END SOURCE POINT:Source Point 1 Cartesian Coordinates = 0.829942 [m], 3 [m], 0.829942 [m] Option = Cartesian Coordinates SOURCES: EQUATION SOURCE:advRTD1 Option = Total Source Total Source = 1 [m^3] END END END SUBDOMAIN:subDom Coord Frame = Coord 0 Location = Assembly END END INITIALISATION: Option = Automatic INITIAL CONDITIONS: Velocity Type = Cartesian ADDITIONAL VARIABLE:advRTD1 Additional Variable Value = 0 [s] Option = Automatic with Value END CARTESIAN VELOCITY COMPONENTS: Option = Automatic END EPSILON: Option = Automatic END K: Option = Automatic END STATIC PRESSURE: Option = Automatic END TEMPERATURE: Option = Automatic END END END OUTPUT CONTROL: RESULTS: File Compression Level = Default Option = Standard END TRANSIENT RESULTS:Transient Results 2 File Compression Level = Default Option = Standard Time Interval = 0.1 [s] END END SIMULATION TYPE: Option = Transient INITIAL TIME: Option = Value Time = 0 [s] END TIME DURATION: Option = Total Time Total Time = 5 [s] END TIME STEPS: Option = Timesteps Timesteps = 0.1 [s] END END SOLUTION UNITS: Angle Units = [rad] Length Units = [m] Mass Units = [kg] Solid Angle Units = [sr] Temperature Units = [K] Time Units = [s] END SOLVER CONTROL: ADVECTION SCHEME: Option = Upwind END CONVERGENCE CONTROL: Maximum Number of Coefficient Loops = 10 Timescale Control = Coefficient Loops END CONVERGENCE CRITERIA: Residual Target = 1.0E4 Residual Type = RMS END EQUATION CLASS:av ADVECTION SCHEME: Option = High Resolution END END TRANSIENT SCHEME: Option = Second Order Backward Euler END END END LIBRARY: ADDITIONAL VARIABLE:advRTD1 Option = Definition Tensor Type = SCALAR Units = [ s] Variable Type = Volumetric END 

December 19, 2006, 04:36 
Re: Vessel Residence Time Distribution Help

#4 
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I am a university student and I am designing a waste water treatment plant for our university canteen. It is a group project and my part of design is equalisation tank.According to our data, our canteen water has some amount of oil. Therefore we disided to treat oil by using saponification process. Then it is depolimerised and treated by using microorganism. We are interested to do saponification process at equalisation tank. Another thing is there are some amounts of solid things in canteen stream. So we want to sediment these things at equalisation tank. So I want to know how to find the residence time for our equalisation tank by considering two things mentioned.Thanks


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