Modeling of thermal denaturation-aggregation of whey proteins can provide assistance in developing dairy products as well as in understanding the mechanisms which drive the formation of fouling deposits. Aggregation of whey proteins depends on temperature (perikinetic contribution, due to Brownian motion) and shear (orthokinetic contribution). Under realistic conditions, different temperature and shear histories are associated with fluid parcels which progress more or less quickly, far or close to the heating wall, inside the processing unit. A numerical approach is proposed for evaluating the thermal denaturation-aggregation of whey proteins, combining computational fluid dynamics and the population balance equation. Fluid flow and heat transfer are solved through the finiteelement- method in the Eulerian frame, while product transformation is evaluated along representative Lagrangian trajectories. Therefore, no assumptions are performed regarding dynamical and thermal histories. The approach is illustrated by the evolution of a suspension of betalactoglobulin, along the first section of a tubular heating exchanger (length 0.4 m, radius 0.004 m, flow rate 20 L/h, inward heat flux 13500 W/m2); at its inlet, the suspension contains 6 % of beta-lactoglobulin at 60 °C. Particle breakage is avoided (shear rate values below 125 s-1). Simulations are performed with and without the orthokinetic term of the aggregation kernel. Results put in evidence that the perikinetic and orthokinetic terms exhibit dominant role for particles sizes below and above about 1 mm, respectively.