Technical Papers and Presentations

High temperature variations inside a tent can be a problem for campers’ thermal comfort. To increase user comfort, Decathlon has tents called "Fresh & Black (F&B)". The main improvement of this equipment lies in the textile technology, regulating the temperature inside and reducing the interior surface irradiation compared to classic textiles. To quantify this, laboratory tests are conducted. Today, testing the tents is the only way of comparing the performance of different prototypes regarding temperature and solar radiation resistance. This procedure is expensive, time consuming and needs reliable physical prototypes. That is why Decathlon leads a thermal digital project with three aims. Firstly, to reproduce the existing physical tests. Secondly, to compare the performance of different tents. Thirdly, to create a simulation application as a predictive tool. Using the COMSOL’s Heat Transfer Module and Fluid Flow Module was proven to be a good solution because of the multiphysics occurring in this problem. In addition, the COMSOL Application Builder represents a great advantage since the app is designed for users who are unfamiliar with simulation. The model is defined using two multiphysics: Nonisothermal flow and Heat transfer with Surface-to-surface radiation. This means three physics: Flow, Heat transfer in fluids and Surface-to-surface radiation. A symmetry is considered in the longitudinal cross section since symmetrical tents are analyzed and to reduce the calculation time. To solve the model, three stationary studies are considered: °Using a k-ε turbulence model with wall functions treatment. °Implementing a Low Reynolds number k-ε turbulence model with an Automatic wall treatment and considering the initial values of variables solved from the first study. °Using the Ray shooting method as a radiation method and considering the values of variables not solved from the second study.
For the first evaluation of the numerical model, one tent is simulated in two different configurations: classic and F&B. The model is built using a wind speed of 2 m/s, a temperature of 27 °C and an external radiation source of 24 x 2500 W, estimated iteratively using an auxiliary sweep to get a surface irradiation of 750 ± 50 W/m² on the floor. The F&B tent shows a lower internal temperature of 6 °C experimentally and of around 2 °C by simulation, compared to the classic one. The surface irradiation inside the tent is measured numerically; for the F&B tent a value of 477 W/m² is obtained whereas for the classic tent 498 W/m². Internal temperature and surface irradiation are more important for the classic tent, which means the F&B technology protects more from solar radiation and ensures a fresher temperature inside the tent, providing a better thermal comfort to the user. The main next step for the current model is to test it considering bigger tents of differing shapes and materials, to validate its reliability and robustness. Afterwards, a model for trekking tents will be developed, and more critical conditions like condensation will be considered. Heat and humidity data simulating the human interaction with the tent will also be taken into account.