Numerical modelling and experimental validation of heat transfer enhancement and thermal mixing in a triple-tube heat exchanger for food processing

Purpose The aim of this study is to evaluate the thermal performance of a triple-tube heat exchanger equipped with staggered fins for food processing. Challenges arise due to the high viscosity of non-Newtonian fluids treated in the food industry, which lead to laminar flow and limited thermal penetration. This research focuses on enhancing heat transfer efficiency and improving fluid thermal mixing using passive heat transfer enhancement methods in a triple-tube heat exchanger. Design/methodology/approach Numerical simulations, implemented within an ANSYS© Fluent environment, are used to solve the equations governing the thermofluid dynamics of a triple-tube heat exchanger with staggered fins in the internal annulus. The rheological behavior of tomato concentrate is modeled by means of a power-law model, coupled with the Arrhenius law to introduce temperature dependency of the consistency index. Experimental validation is adopted to verify simulations accuracy. Findings The finned configuration enhances heat transfer and improves thermalization by induced swirling flows and consequent boundary layers disruption. The geometrical configuration presenting eight-finned modules achieves a maximum performance index of 1.23 in the entrance region, while mitigating frictional effects. Moreover, such fins arrangement guarantees good thermal mixing. Originality/value This study represents one of the first attempts of enhancing heat transfer performance of a triple-tube heat exchanger for thermal processing of food products. The exceptionally low generalized Reynolds number and high generalized Prandtl number characterizing the treated fluid result in severe heat transfer limitations, tackled by a practical design strategy able to improve energy and thermal treatment efficiency.