This case study focuses on the problem analyzed by Zuritz of designing a TTHE-HL to cool a food product from 80 °C to 30 °C. The cooling fluid, tap water, is available at 15 °C and flows in the inner tube and the outer annular section. The food product flows counter-currently in the inner annular section. The wall thickness of the tubes is 0.0015 m and, for the simulations, a length of 35 m is assumed. The other parameters used in the analytical and numerical solutions are given in Table .