Strategies for solving the air flow—Thermal problem in multiroom buildings

Iterative and direct methods for solving the coupled problem of heat and mass transfers in buildings are presented and compared. Numerical problems often trouble the resolution of this problem and a choice between different strategies can be a way to overcome instabilities of calculus and runningtime difficulties. The state of the zones of air is represented as a function of temperature and pressure. The iterative method consists of separating the problem into two sub-sets, the first being a function of temperature and the other a function of pressure. The direct method simultaneously carries out the resolution of the original set. Two simulation codes were developed based on the ‘coupling method’, which is a method of solving the thermal problem by splitting it into levels of coupling. The direct option needs more computational effort, but is easier to run by non-experts. In contrast, the iterative method is better adapted to the connection of different programs. Simulation results are presented, and the performances of the two strategies are compared and discussed.