Computational fluid dynamics-based thermal modeling for efficient building energy management

Heating, Ventilating and Air-conditioning systems have a significant share in the energy consumed by buildings. Development of a highly accurate thermal model is the first step in designing an efficient air-conditioning system. In this regard, this paper proposes a semi-nonlinear thermal model - ordinary differential equation with parameters as nonlinear functions of ambient temperature and cooling air flow-rate - to approximate the temperature solutions simulated using computational fluid dynamics (CFD). A three-roomed building, equipped with an air-conditioning system is modeled, and Navier-Stokes equations are solved to simulate the temporal evolution of temperatures for different ambient temperatures and cooling air flow-rates. The steady-state temperatures and transient solution parameters of the thermal model are assumed to be polynomial functions of ambient temperature and flow-rate, and are determined by minimizing the error between the thermal model- and the CFD-based final and transient temperature solutions, respectively. The proposed thermal model of third-order, with nonlinear type transient coefficients is shown to predict the temporal evolution of temperature accurately. The high prediction accuracy of the proposed thermal model makes it to be a potential candidate for the design of an optimal temperature regulator.