FACSIMILE

Arsineh Hecobian Jaemeen Baek

Index

  Important Functions of Facsimile Model Run Examples   Application: HONO Reaction Conclusion

Overview

   A user-friendly computer program for modeling chemical kinetics and transport Develop useful models rapidly, with specific facilities for modeling chemical kinetics Handle very stiff ordinary differential equations with the robust numerical integrator   a predictor-corrector technique The values of the solution vector at the end of a step are first predicted, and are then corrected to satisfy the differential equations by a few Newton iterations

Important Functions of Facsimile

  4 Model Types  Homogeneous chemical reaction scheme    Chemistry with flow and diffusion Fitting model to data 2-Dimensional flow with diffusion Reaction Database  Thousands of reactions from many database (NIST Chemical Kinetics, NDRL/NIST Solution Kinetics, SGTE pure element, etc.)

Homogeneous chemical reaction

 Illustrates simple chemical reaction H2 = H + H kf 10 H + O2 = OH + O 200 kr 1 2

Chemistry with flow and diffusion

 Simulates chemical kinetics, plug flow (1-D) and diffusion along a pipe 

c



t



Q



D

 2

c



x

2 

u



c



x

c: A species concentration t: time x: The distance along the pipe Q: The net production/destruction rate of the species due to the chemical reaction D: The species diffusion constant u: The flow velocity

Fitting model to data

  Fits unknown parameters in the model to experimental data (A B) time A B 0.2 2.019

0.3 0.907

0.4 0.408

0.5 0.183

8 9.1

9.6

9.8

The reaction equation for data

dA

 

kA dt

=> find k

2-Dimensional flow with diffusion

   Similar to the Advection-Diffusion model Simulates transport through a two dimensional matrix Reactants can flow from one cell to the next in either dimension  From a cell (x, y) to (x,y+1) or (x+1,y), and can diffuse to any adjacent cell ie from (x,y) to (x,y+1), (x,y-1), (x-1,y) and (x+1,y)

Model Run – Main Menu

Main Menu Model Wizard

Model Run – Homogeneous Rxn

*.fac

% k1db : O3 + O = O2 + O2; % k2db : O2x + O3 = O + O2 + O2; % k3db : Ox + O3 = O + O + O2; % k4db : Ox + O3 = O2 + O2; % k5db : O3 + M = O + O2; % k6db : H + O3 = OH + O2; % k7db : H + O3 = OH + O2; % k8db : O3 + OH = HO2 + O2; % k9db : HO2 + O3 = OH + O2 + O2; % k10db : O3 + M = O + O2; % k11db : O + O3 = O2 + O2; % k12db : OH + O3 = HO2 + O2; % k13db : HO2 + O3 = OH + O2 + O2; % k14db : O + O2 = O3; % k15db : O + O2 + M = O3 + M;

Model Run – Homogeneous Rxn

Initial concentration Time steps

Model Run – Homogeneous Rxn

Homogeneous Reaction

* Generated by FACSIMILE Reaction Wizard Tuesday, November 25, 2003 ; ; TEMP 298 k7db k8db k9db 1.21E+09 k10db k11db 2.35E+13 k12db 1.93E+10 COMPILE EQUATIONS ; % k1db : O3 + O = O2 + O2; % k2db : O2x + O3 = O + O2 + O2; % k3db : Ox + O3 = O + O + O2; % k4db : Ox + O3 = O2 + O2; % k5db : O3 + M = O + O2; % k6db : H + O3 = OH + O2; % k7db : H + O3 = OH + O2; % k8db : O3 + OH = HO2 + O2; % k9db : HO2 + O3 = OH + O2 + O2; % k10db : O3 + M = O + O2; % k11db : H + O3 = OH + O2; % k12db : O + O3 = O2 + O2; % k13db : OH + O3 = HO2 + O2; ; % k14db : HO2 + O3 = OH + O2 + O2;

VARIABLE

;

O3 OH

COMPILE INSTANT; % k15db : O + O2 = O3; % k16db : O + O2 + M = O3 + M;

H HO2 M O Ox O2 O2x

SETPSTREAM 1 8 ; TIME ; HO2 = 0.00000001 ; H HO2 M O Ox O2 O2x ;

k1db = 5.20E+12 * EXP(-2090/TEMP) ; k5db = 4.60E+16 * TEMP@(-0.44) * EXP(-11930.0/TEMP) ; k7db = 9.00E+12 * TEMP@(0.5) * EXP(-2010.0/TEMP) ;

k1db = 5.20E+12 * EXP(-2090/TEMP) ;

k8db = 7.80E+11 * EXP(-960/TEMP) ;

O3 OH ; **; COMPILE OUT ; **; k7db = 9.00E+12 * TEMP@(0.5) * EXP(-2010.0/TEMP) ; WHENEVER TIME= k8db = 7.80E+11 * EXP(-960/TEMP) ; k10db = 4.60E+16 * TEMP@(-0.44) * EXP(-11930.0/TEMP) ; **; 20 * (+0.5) 0 % CALL OUT; **; BEGIN;

Model Run – 2-D Flow & Diffusion

Model Run – 2-D Flow & Diffusion

Model Run – 2-D Flow & Diffusion

Model Run – 2-D Flow & Diffusion

Application: HONO Reaction

  Production of HONO (Nitrous Acid) from mixing OH and NO This experiment was used to make a known amount of HONO (in lab) to be used to calibrate an LIF (Laser Induced Fluorescence) instrument which will be used to measure ambient HONO concentrations

Experimental setup

NO NO, OH, H, O 2 , H 2 O, H 2 O 2 , HO 2 O 3 , HNO 3 , O, NO 2 , N 2 ,… H 2 O + N 2 2” Hg Lamp LIF

Reactions

  Main Reaction  OH + NO + [M]  HONO + [M] Other Reactions     OH + OH + [M] OH + OH  H 2 0 + O OH + HOOH  H 2 O + H0 2 OH + HO And more… 2  H 2  H 2 O 2 + [M] O + O 2

Facsimile model setup

   Set Conditions:  T = 293K  P = 1013 mb 29 reactions and their rate constants were used in this model Using (H 2 O + hv  OH + H) J value, the flow rate of 1 slpm(standard liter per meter) for water vapor and N 2 and manufacture’s specifications for the intensity of the Hg Lamp, the amount of OH and H produced were calculated and put as initial values in the model

Facsimile model setup

  Model Type  Chemistry with flow and diffusion model Reactions were selected from the reaction database

Initial Values

   OH = 7.4 x 10 11 molecules cm -3 H = 7.4 x 10 11 molecules cm -3 NO = 5 x 10 12 molecules cm -3 (from a 10 ppb cylinder)

Results of the model

Snapshot graphs

Conclusions

 The data from this model agreed with the experimental data and data from another model in MATLAB

Advantages

  A very fast and very easy model setup for different applications   No need to arrange bundle of differential equations Correct model results Model scripts in text files   Easy to edit The model wizard adds comments automatically

Further Improvement

  Bunch of errors  Using special character ‘*’ in reaction database  Hard to debug  The more powerful debugging tool  The more detailed error messages Weak graphic functions   No axis scaling is available Graphs are not compatible with windows cut and paste

Further Improvement

 Hidden limitations  The pipe length  Maximum values for some parameters  Not best-fitted for atmospheric chemistry  Photochemical decomposition rates are missing  150 lines to define 20 x 20 grid model  Limitations may not be larger enough to define atmospheric chemical reaction system