Consolidation of heat transfer coefficients of viscoelastic simulated food solutions in helical exchangers Original Research Article

Heat transfer of viscoelastic liquids in helical exchangers attracted limited work in the past. Most heat transfer equations proposed do not reduce to the Graetz–Leveque equation for the straight tubes. Heat transfer coefficients were obtained for seven copper helical coil heat exchangers with different diameters and diameter ratios. Hot water was used as the heating medium; and dilute polyacrylamide solutions were used to simulate the food solutions. Results showed increased heat transfer coefficients but the magnitudes were lower than those obtained by previous workers. A unified form of the Graetz–Leveque equation obtained was: Nu = 1.75 Gz1/3[1 + 0.5421Dn0.45(d/D)0.54] for water. The heat transfer equation for the 250 ppm solution is represented by, Nu = 1.75 Gz1/3[1 + 0.3515Dn0.45(d/D)0.54]; and for the 500 ppm solution the results can be represented by Nu = 1.75 Gz1/3[1 + 0.3615Dn0.45(d/D)0.54]. Viscoelasticity reduces heat transfer performance.