Numerical Modeling of Turbulent Heat Transfer and Fluid Flow in a Tunnel Pasteurization Process

Abstract

The purpose of this study is to model the heat transfer and fluid flow in a tunnel pasteurizer, which can be used to predict the operation status of the pasteurization process. This modeling is very useful when some changes must be made to the design, operation, or the types of products to be pasteurized. Moreover, the model can be used to provide valuable data for the optimization of the pasteurization design. In the modeling two approaches have been adopted. One is the Lumped Parameter Method (LPM), which is used to model the whole pasteurization system, including pipes, zones and heat exchangers. The other one is the Computational Fluid Dynamics (CFD) technology for calculations of the heat transfer and fluid flow rates in the heat exchanger tank. A steady state model in a tunnel pasteurizer has been developed by using the LPM. The temperatures of the spray water and the products in the pasteurization process were calculated by employing this model. The comparisons showed reasonably good agreements between the predicted results and the experimental data. The pressure variations along the regenerative loops were also calculated. With the CFD technology, the numerical calculations of heat transfer and fluid flow have been performed on the temperature distribution in the cylindrical heat exchanger tank that provides a hot water through the top and a cold water through the bottom of tank. There are two outlets. In the heat exchanger tank, the tube arrays are set along the azimuth direction of the tank. This is a thermally stratified layered water tank that can control the four zones of the water temperatures.