Thermal simulation: Response factor analysis using three-dimensional CFD in the simulation of air conditioning control

Abstract

The heat generated from an air-conditioning equipment or other thermal loads is distributed throughout a room by a three-dimensional airflow. This three-dimensional airflow creates a three-dimensional heat distribution in a room. To better understand building performance, we must integrate this spatial distribution into building simulations. Thus, three-dimensional computational fluid dynamics (CFD) analysis is necessary in design process because most conventional building energy simulations still employ a temperature that is averaged across the space of a room. However, usually only a few cases of CFD analyses are executable in real design process because of the large computational load they require. This paper presents a new, simplified method to calculate heat transport phenomena in rooms, based on a few cases of CFD analysis, and to integrate data into a nodal analysis. This method can be used to calculate an indoor environment, including the spatial distribution of temperature, with a computational load that is much lighter than it is in a simulation using CFD alone. Furthermore, in terms of precision, it is a far more reliable method than the conventional simulation, which assumes the perfect mixing of heat in a room. In the paper, we apply this method to simulate the control of air conditioning. Ordinarily, the reproduction of the phenomena shown in the calculation examples requires substantial manpower and costly computing resources for experimentation or CFD analysis. With our calculation method, it is possible to reproduce the same calculation results in a very short time with a PC. And we checked the potential to the practical use through a verification calculation with CFD analysis.