Study of residence time distribution and heat transfer in an exchanger used for cooling liquid foods

• Grant number: 25/03310-8
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: May 01, 2025
• End date: April 30, 2026
• Field of knowledge: Engineering - Chemical Engineering - Industrial Operations and Equipment for Chemical Engineering
• Principal Investigator: Jorge Andrey Wilhelms Gut
• Grantee: João Pedro Balbino da Silva
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Given the low overall heat transfer coefficients in heat exchangers for heating or cooling products in laminar flow, mixing elements, such as corrugated surfaces, static mixers or curved tubes, are useful for increasing efficiency and reducing size. In helical flow in spiral tubes, centrifugal force generates vortices that promote radial mixing, improving convection and reducing dispersion in the residence time distribution (RTD), important for reactive flow. In this research, heat transfer and RDT in a helical heat exchanger used as a cooler in the thermal processing of liquid foods on a pilot scale will be studied using water and a simulated food with properties close to those of fruit juices and pulps and pseudoplastic rheology (flow rates between 0.5 and 2.0 L/min) as fluids. Tracers with electrical conductivity or color response will be used for RDT, with model adjustment and correlation of parameters and mean residence time with flow rate. For heat transfer, cooling tests will be performed to correlate the overall exchange coefficient with the exchanger operating conditions. Adjusted correlations will be used to calculate the temperature history of a particle in the system and the sterilization value. The influence of helical flow on the DTR and heat transfer in relation to a straight tube will be analyzed, also comparing results for water and simulated food. This study contributes to the research project "Development of a microwave applicator for continuous thermal processing of liquid foods" (FAPESP 2023/1316-4, CNPq 409472/2021-2) in the process modeling validation stage, in addition to contributing to the proponent's chemical engineering training.