Simplified methodology for indoor environment designs

Abstract

Current design of the building indoor environment uses averaged single parameters such as air velocity, air temperature or contaminant concentration. This approach gives only general information about thermal comfort and indoor air quality, which is limiting for the design of energy efficient and healthy buildings. The design of these buildings requires sophisticated but practical tools that are not currently available, and the objective of this thesis is to develop such a tool. The development of the simple design tool had several phases. Each phase employed simplified models validated with measured data in order to assess model accuracy and reliability. The validation data was obtained from a state-of-the-art experimental facility at MIT. Based on the collected data, we first developed simplified boundary conditions for the diffuser jet flow, which is the key flow element in mechanically ventilated spaces. The boundary conditions employ resultant momentum from the supply diffusers without modeling the detailed diffuser geometry. Although simple, the models can simulate airflow from complex diffusers commonly used for air-conditioning with reasonable accuracy. Another simplification is the use of a zero-equation turbulence model to calculate indoor air distribution. The model uses the concept of eddy-viscosity and approximate turbulent viscosity with an algebraic equation. To test the turbulence model, an airflow program was developed. The program can simulate indoor airflow on a PC within several minutes, which is five to ten times faster than with the similar programs with a "standard" k-£ model. Finally, the airflow program was coupled with an energy analysis program. The combined program simultaneously analyzes internal heat transfer and air movement as well as the heat transfer through the building envelope. The impacts on the thermal comfort in the occupied zone are quantified, and we found that the thermal comfort in most cases is not