In  the  case  of  the  puddling  furnace  of  Problem  22,  assume
that  the  hot  gases,  instead  of  going  directly  into  the  chimney,
are  passed  through  the  flues  of  a  boiler  placed  above  the  fur-
nace, and  thence  pass  into  the  chimney  at  a  point  15  feet
higher  than  before.  Assume  chimney  3  feet  6  inches  internal
diameter,  64.5  feet  high  above  the  furnace  flue,  and  that  the
gases  now  passing  into  it  15  feet  higher  up  are  at  350°  C.,  and
cool  to  250°  C.  at  the  top  of  the  chimney.  The  boiler  flues  in-
troduce additional  frictional  resistance  equal  to  0.1  inch  of
water.  The  boiler  raises  steam  at  a  net  efficiency  of  45  per
cent.,  the  steam  engine  utilizes  the  steam  at  a  mechanical
efficiency  of  20  per  cent.,  and  a  centrifugal  fan  supplies  the
forced  draft  needed  at  a  mechanical  efficiency  of  25  per  cent.
Required:  (1)  The  total  head  of  the  chimney,  when  the
furnace  discharged  directly  into  it,  and  the  average  tempera-
ture of  the  gases  in  it  was  1100°  C.,  and  specific  gravity  1.03
(air  =  1).
(2)  The  head  absorbed  as  velocity  of  the  outgoing  gases,
their  temperature  being  1000°  C.
(3)  The  head  lost  in  friction  in  the  chimney,  in  this  case.
(4)  The  head  which  was  available  to  run  the  puddling  furnace.
(5)  The  total  head  of  the  chimney  with  the  gases  entering
15  feet  above  former  flue,  and  average  temperature  300°  C.
CHIMNEY  DRAFT  AND  FORCED  DRAFT  195

(6)  The  head  absorbed  in  this  case  as  velocity  of  outgoing
gases,  their  temperature  being  250°  C.
(7)  The  head  lost  in  friction  in  the  chimney  in  this  case.
(8)  The  available  head  to  draw  gases  into  the  chimney.
