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    Ch128P: Principles of Transport Processes Worksheet No. 5: Diffusion

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    SC Tagle
    This document contains 4 diffusion problems to solve for a transport processes class. The problems involve calculating rates of diffusion of substances like benzene and CO2 through various mediums, as well as determining concentration profiles of diffusing substances over time. Students are instructed to show their work and solutions on separate sheets of paper and submit by a specified date.

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    Ch128P: Principles of Transport Processes Worksheet No. 5: Diffusion

    Uploaded by

    SC Tagle
    58 views1 page
    This document contains 4 diffusion problems to solve for a transport processes class. The problems involve calculating rates of diffusion of substances like benzene and CO2 through various mediums, as well as determining concentration profiles of diffusing substances over time. Students are instructed to show their work and solutions on separate sheets of paper and submit by a specified date.

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    Diffusion

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    This document contains 4 diffusion problems to solve for a transport processes class. The problems involve calculating rates of diffusion of substances like benzene and CO2 through various mediums, as well as determining concentration profiles of diffusing substances over time. Students are instructed to show their work and solutions on separate sheets of paper and submit by a specified date.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    58 views1 page

    Ch128P: Principles of Transport Processes Worksheet No. 5: Diffusion

    Uploaded by

    SC Tagle
    This document contains 4 diffusion problems to solve for a transport processes class. The problems involve calculating rates of diffusion of substances like benzene and CO2 through various mediums, as well as determining concentration profiles of diffusing substances over time. Students are instructed to show their work and solutions on separate sheets of paper and submit by a specified date.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
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    CH128P: PRINCIPLES OF TRANSPORT PROCESSES

    Worksheet No. 5: Diffusion


     
     
    Solve  the  following  problems.  Write  your  solutions  on  separate  sheets  of  paper  (1  sheet  per  problem).  
    Submission  is  on  April  27,  2020.  

     
    1. An  open  circular  tank  8  m  in  diameter  contains  benzene  at  22°C  exposed  to  the  atmosphere  in  such  a  
    manner   that   the   liquid   is   covered   with   a   stagnant   air   film   estimated   to   be   5   mm   thick.   The  
    concentration   of   benzene   beyond   the   stagnant   film   is   negligible.   The   vapor   pressure   of   benzene   at  
    22°C  is  100  mm  Hg.  What  is  the  rate  of  loss  of  benzene  from  this  tank?  The  specific  gravity  of  benzene  
    is  0.88.  
     
    2. An   ammonia   (A)-­‐water   (B)   solution   at   278   K   and   4.0   mm   thick   is   in   contact   at   one   surface   with   an  
    organic   liquid   at   this   interface.   The   concentration   of   ammonia   in   the   organic   phase   is   held   constant  
    and   is   such   that   the   equilibrium   concentration   of   ammonia   in   the   water   at   this   interface   is   2.0   wt%  
    3
    ammonia   (density   of   solution   is   991.7   kg/m )   and   the   concentration   of   ammonia   in   water   at   the   other  
    3
    end  of  the  film  4.0  mm  away  is  10  wt%  ammonia  (density  of  solution  is  961.7  kg/m ).  Water  and  the  
    -­‐9 2
    organic  are  insoluble  in  each  other.  The  diffusion  coefficient  of  ammonia  in  water  is  1.24  x  10  m /s.  
    At  steady  state,  calculate  the  flux  NA.  Also,  what  is  NB?  
     
    -­‐4 2  
    3. A   flat   plug   30   mm   thick   having   an   area   of   4.0   ×   10   m and   made   of   vulcanized   rubber   is   used   for  
    closing  an  opening  in  a  container.  The  gas  CO2  at  25°C  and  2.0  atm  pressure  is  inside  the  container.  
    Calculate   the   total   leakage   or   diffusion   of   CO2   through   the   plug   to   the   outside   at   steady   state.   Assume  
    3
    that  the  partial  pressure  of  CO2  outside  is  zero.  The  solubility  of  the  CO2  gas  is  0.90  m  gas  (at  STP  of  
    3 -­‐9 2
    0°C  and  1  atm)  per  m  rubber  per  atm  pressure  of  CO2.  The  diffusivity  is  0.11  ×  10  m /s.    
     
    -­‐4 3
    4. A  long  gel-­‐like  slab  of  material  (1.5  cm  thick)  contains  a  solvent  (concentration  of  2  x  10  gmol/cm ).  
    The   solid   is   placed   in   a   fast-­‐flowing   water   stream   so   that   the   solvent   can   diffuse   in   the   direction  
    -­‐1   2
    perpendicular  to  the  slab  axis.  The  solvent  diffusivity  in  the  solid  is  5.0  x  10 m /s.  Find  the  centerline  
    concentration  of  the  solvent  after  a  day.  
     

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