[Gasification] heat exchanger

[Oscar]

...Very sorry, my former message was aimed to Toby not to Jim.
My deepest apologies for my unforgivable mistake...!!!!

Kindest regards.

Oscar.

 

-----Mensaje original-----
De: Oscar [mailto:oscar at geprop.cu] 
Enviado el: martes, 18 de septiembre de 2007 8:49
Para: 'Discussion of biomass pyrolysis and gasification';
'jimmason at whatiamupto.com'
Asunto: RE: [Gasification] heat exchanger

Hi Jim and colleagues.

Jim, it seems to me that there is a small misunderstanding when you say that
turbulent flow is not the proper flow to maximize heat exchange. 
According to heat transfer phenomena it is just turbulent regime the one
which ensure higher heat transfer rate because the laminar layer on the
solid surface over which is flowing the fluid gets to its minimum. Otherwise
such layer will built up making it more difficult to transfer heat across
the solid surface. 
On the other hand turbulent regime will also help in keeping solid
deposition to its minimum because of higher flow velocity over the surface. 
Just for the sake of having a quick picture about this I suggest you get
some good text books on heat transfer and/or thermodynamic, including
Perry's handbook, Bennets and Myers, Coulson and Richardson etc.

Hope this help.

Kindest regards.

Oscar.

 

-----Mensaje original-----
De: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org] En nombre de Toby Seiler
Enviado el: martes, 18 de septiembre de 2007 6:06
Para: jimmason at whatiamupto.com
CC: gasification at listserv.repp.org
Asunto: [Gasification] heat exchanger

Jim,
   
  A comment on heat exchangers that stuck with me is about turbulence.
Turbulent flow is not the proper flow to maximize heat exchange, laminar is.
The hot surface should be wiped clean of it's heat and moved on.  Turbulent
flow regions in a given pipe should be avoided.
   
  A boiler is a big heat exchanger.  Fire tube boilers are often used for
wood burning because of the larger passage size that does not clog as fast
as the smaller spaces of the typical water tube.  But a water tube can have
more surface area for collection.  Be it radiant or conductive, square feet
matter.  
   
  Also the bending of the water tube can be shaped to collect from a given
fire box. Water tubes over an iridescent catalyst unit fed from a gasifier
would work, since most ash and solids would have been significantly reduced,
compared to a direct wood fired boiler.  
   
  Regards,  Toby Seiler
   
   

       
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