HEAT EXCHANGER NETWORK SYNTHESIS CONSIDERING CHANGING PHASE STREAMS

Abstract

The Pinch Design Method was developed considering one-phase streams, with constant
specific heats (Cp) throughout streams temperature ranges. Its first stage, the determination
of utilities targets and pinch point (PP), is ruled by the number of streams, their temperatures
and MCp. But, for changing phase streams, the usual description of the Cp behavior by a
constant value can lead to errors in this stage and, hence, in the synthesis one. This work
proposes a procedure to deal with these streams and discusses its results through an example
involving multicomponent streams. First, bubble (BP) and dew (DP) points of the streams
are estimated. Then, changing phase streams are split into sub-streams, using BP and DP
as bounds. For each one, an effective Cp is estimated as the division of the enthalpy
change by the respective temperature difference. Results obtained show significant changes
on the PP, utilities targets and network proposed structure.