Construction, Validation and Testing of a Water Table for Natural Ventilation Analysis

Monisha Royan, Prasad Vaidya | 2020


Natural Ventilation in mixed mode cooling presents an opportunity to reduce the dependence on air-conditioning for cooling and ventilation, especially in residential buildings. Intuitive design approaches for natural ventilation can lead to less than optimal performance, and performance analysis is necessary for more predictable performance. However, analytical tools such as CFD modelling can be too complex and time consuming to be accessible to design professionals for assessing natural ventilation flows of real buildings with elaborate geometry. Conversely, simplified approaches may not represent the complex conditions in the building. The water table apparatus was developed as an affordable and accessible tool to simulate air movement, visualize ventilation flows, and enable quantitative comparative analysis.

This paper summarizes the design and construction of the water table apparatus, the method for conducting experiments, validation of its results, and its use for design analysis. A parametric study of design alternatives is conducted for a residential three-bedroom apartment building, and design decisions such as building orientation, window size and internal obstructions are evaluated. The airflow through the building model was simulated with water, video recordings are used to visualize flow, and still images are processed with graphic filters for quantitative analysis. The quantitative results are in the form of percentage area with access to good ventilation, percentage area with dead spots, air changes per hour, and a preliminary assessment of temperature gradients due to mixed air. The water table apparatus is an affordable, accessible tool that provides visual and quantitative results that are useful in the design of wind-driven natural ventilation.