## 3 Simulation of Thermal Processes in the Food Industry Using CFD
### Examples of Thermal Processes Modeled Using CFD  
#### 3.2.1 Baking, Frying, and Grilling Processes  
Baking, frying, and grilling are key thermal processes in the food industry, each characterized by complex heat transfer mechanisms that can be accurately simulated using CFD. These processes involve intricate interactions between heat transfer, fluid dynamics, and mass transfer, making CFD an essential tool for optimizing product quality, energy efficiency, and process design. Through the application of advanced mathematical models, CFD simulations can provide detailed insights into thermal behavior, enabling more precise control over manufacturing conditions. Baking Process  
In the baking process, heat transfer occurs predominantly via conduction and convection. Thermal energy is transferred from the oven surfaces to the dough through conduction, while convective heat transfer occurs as hot air circulates within the baking chamber. The CFD models employed for baking simulations typically integrate the Navier-Stokes equations (Equation (1)) for fluid flow, [PERSON]'s law of heat conduction (Equation (6)), and equations governing moisture migration and phase change phenomena. These models enable the prediction of temperature distributions, moisture content profiles, and crust formation dynamics with high spatial resolution [72,73]. To accurately model airflow patterns within the oven, turbulence models such as k-\(\epsilon\) or k-\(\omega\) are commonly employed. These models allow for the prediction of turbulent eddy viscosities and the characterization of the interaction between turbulent eddies and heat transfer. For instance, studies have demonstrated that adjusting airflow configurations in the oven can significantly improve heat transfer uniformity, reduce baking times, and enhance product consistency [26]. Additionally, CFD simulations can account for the moisture diffusion and vaporization processes occurring in the dough, employing models for phase change, such  
Figure 1: CFD simulation of beef roasting in a convection–steam oven. as the Clausius-Clapeyron relation and the Fick's law of diffusion. These considerations are critical for controlling the final texture and moisture content of the product [74]. The frying process is primarily driven by convective heat transfer between the hot oil and the food product. The temperature of the frying medium plays a pivotal role in determining the final texture, flavour, and nutritional properties of the food. CFD simulations of frying incorporate models such as the VOF method, which is used to track the interface between the oil and the food (Equation (5)) [25]. The VOF method captures the oil-food interface dynamics, which is crucial for accurately modeling oil absorption and frying efficiency. Additionally, empirical correlations for the convective heat transfer coefficient in the oil phase can be integrated to improve the precision of the heat transfer predictions [75]. Furthermore, CFD allows for the analysis of bubble dynamics during frying, which can significantly impact heat transfer and oil degradation. The dynamics of gas bubbles, such as their rise velocity and coalescence, influence both the thermal conductivity of the oil and the mass transfer between the oil and the food. The incorporation of chemical kinetics into CFD models enables the simulation of oil oxidation and degradation reactions, which are critical for understanding the shelf life and safety of fried products [75; 76]. Grilling Process  
Grilling is characterized by both conduction (from the grill surface to the food) and convection (through the surrounding hot air). The application of CFD in grilling involves solving heat conduction equations for the grill surface and convective heat transfer equations for the surrounding air, typically using the Boussinesq approximation for buoyancy effects in the air flow (Equation (2)) [20; 77].