The heat exchanger consists of 13 plates and both counter-current andco-current flows exists.Milk(processfluid)enters the PHE at 60 C and its flowrate is 0.833]10~4 m3/s. The technical details of this exchanger are given in Table 2. Hot water is assumed to be the heating medium at a flowrateof 2.4]10~4 m3/s and inlet temperature 97C. The inlet protein concentration is 5 kg/m3. All these details were taken from Delplaceet al. (1994). Milk properties are assumed to be identical to those of water as in Delplace et al. (1994). Based on the given technical characteristics the heat transfer and cross sectional areas can be easily calculated (see Table 2). All plates are assumed to have the same geometric characteristics.