1. Heat and material balances are the basis for evaporator calculations.
2. The rate of boiling is governed by the heat transfer equations.
3. For multiple effect evaporators, i.e. two or more evaporators used in series,
with two evaporators, if q1 = q2
U1A1DT1= U2A2DT2
and if A1 and A2 are equal U2/U1 = DT1/DT2
(and this can be extended to more than two effects.)
4. Multiple-effect evaporators use less heat than single-effect evaporators. For an n-effect evaporator, the steam requirement is approximately 1/n, but requires more heat exchange surface; the heat-exchange surface required is approximately n times for the same output. From the energy viewpoint, evaporators can therefore be very much more efficient than dryers.
1. Heat and material balances are the basis for evaporator calculations.
2. The rate of boiling is governed by the heat transfer equations.
3. For multiple effect evaporators, i.e. two or more evaporators used in series,
with two evaporators, if q1 = q2
U1A1DT1= U2A2DT2
and if A1 and A2 are equal U2/U1 = DT1/DT2
(and this can be extended to more than two effects.)
4. Multiple-effect evaporators use less heat than single-effect evaporators. For an n-effect evaporator, the steam requirement is approximately 1/n, but requires more heat exchange surface; the heat-exchange surface required is approximately n times for the same output. From the energy viewpoint, evaporators can therefore be very much more efficient than dryers.
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