2. Evaporator Performance

There are three main measures of evaporator performance:

  1. Capacity (kg vaporized/time)

  2. Economy (kg vaporized/kg steam input)

  3. Steam Consumption (kg/hr)

Note that the measures are related, since \[\text{Steam Consumption} = \frac{\text{Capacity}}{\text{Economy}}\]

Economy calculations are determined using enthalpy balances.

The key factor in determining the economy of an evaporator is the number of effects. The economy of a single effect evaporator is always less than 1.0. Multiple effect evaporators have higher economy but lower capacity than single effect.